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Preview: Chemical Engineering & Technology

Chemical Engineering & Technology



Wiley Online Library : Chemical Engineering & Technology



Published: 2017-09-01T00:00:00-05:00

 



Surface modification of polysulfone membrane using poly(acrylic acid)-decorated alumina nanoparticles

2017-09-18T02:16:09.882383-05:00

Alumina nanoparticles were decorated by poly(acrylic acid) (PAA) as a hydrophilic polymer through a thermal polymerization of acrylic acid in the presence of alumina nanoparticles. The obtained PAA-decorated alumina (PAA-d-Al) nanoparticles were embedded into the polysulfone membrane matrix via nanofiller dispersion in the casting solution. The prepared membranes were characterized by porosity and water contact angle measurements, scanning electron and atomic force microscopy as well as fouling tests using whey proteins. According to the results, the presence of nanoparticles had significant effect on the membrane hydrophilicity and surface softness resulting in fouling mitigation and flux recovery enhancement compared with the virgin polysulfone membrane. Moreover, the prepared membrane embedded with 0.25 wt.% of PAA-d-Al nanofillers showed a remarkable durability and reusability during the filtration tests.



Capturing CO2 by Using a Micro-algae Culture Recycle Solution

2017-09-18T02:16:08.266768-05:00

In this study, capture of CO2 by using a micro-algae culture solution was explored in a continuous bubble-column scrubber under a constant pH environment. The aim of this work was to search for the optimum conditions for a pilot-scale study. With the Taguchi method, a total of L16(44) = 16 runs were required. The absorption rate (RA), absorption efficiency (E), overall mass-transfer coefficient (KGa) and gas-liquid flow rate ratio (γ) were determined by using a material balance, as well as a two-film model in a steady-state condition. From the signal/noise (S/N) ratio, the sequence of parameters showed that C(Qg)>A(pH)>B(T)>D(CL). In addition, the optimum results for E, RA, KGa and γ were all satisfied. Uncontrolled experiments were also carried out. Empirical equations were also discussed.



Low-cost Noninvasive Real-time Imaging for Tubular Continuous-flow Crystallization

2017-09-18T02:15:53.754037-05:00

A key design limitation to the effective monitoring and control of continuous crystallization processes is the ability to characterize crystals in real time. This article describes a low-cost system, composed of a basic stereomicroscope and video camera, for the in-situ imaging of sub-millimeter crystals through curved walls of millifluidic tubular crystallizers. Real-time videos taken for millimeter-size slurry slugs are used to guide the experimental design for a recently developed multiphase-flow crystallization process, including the improvement of the slug aspect ratio, visualization of crystal shapes, and observation of the extent of aggregation. Design considerations are also discussed for the use of multiple stereomicroscopes in other continuous-flow tubular experiments.



Efficient Control of Microbubble Properties by Alcohol Shear Flows in Ceramic Membrane Channels

2017-09-15T05:15:35.25508-05:00

The efficient control of microbubbles is achieved by using the alcohol shear flows in ceramic membrane channels. The dependence of hydrodynamic and mass transfer properties of microbubbles on liquid viscosity is investigated in a bubble column with 32 mm i.d. and 800 mm height. The multi-channel ceramic membrane with an average pore size of 200 nm works as the gas sparger, and the shear flow on the membrane surface controls the microbubble generation. Oxygen gas and glycerin solutions with different viscosities (μl = 1 - 42 mPa·s) are used as gas phase and liquid phase, respectively. The microbubbles are massively generated at different liquid viscosities. With increasing viscosity, the bubble size first decreases (μl < 2.0 mPa·s) and then increases. The dual effect of viscosity on bubble size is related to bubble coalescence. In low viscosity range, increasing viscosity hinders liquid film drainage and thus inhibits coalescence. At high viscosity, liquid turbulence intensity is weakened and bubble coalescence is enhanced. However, the dual effect of viscosity on gas holdup is not observed for microbubble. Increasing viscosity makes the monotonic increase in Sauter diameter and specific interfacial area, while the mass transfer coefficient decreases as viscosity increases at small cross flow velocities.



Rotor-stator spinning disc reactor: characterization of the single-phase stator-side heat transfer

2017-09-15T04:30:41.934063-05:00

The single-phase fluid-stator heat transfer in a rotor-stator spinning disc reactor in dependence on rotational Reynolds number, dimensionless throughput, Prandtl number and aspect ratio is examined. For a parameter range of Reω = 1.1 · 104 - 2.7 · 106, CW = 60 - 450, Pr = 4 - 14 and the two aspect ratios G = 0.0074 and 0.0154, an increase in the stator-side Nusselt number with increasing Reynolds number, Prandtl number and a higher throughput is found. Laminar and turbulent flow regions are observed, which coincide with a throughput- and a rotation-governed heat transfer regime, respectively. A Nusselt correlation to predict the experimental data in the turbulent flow regime within 20 % accuracy was established. An increase in the overall volumetric heat transfer coefficient from 1.27 MW m-3 K-1 to 2.16 MW m-3 K-1 for a rise in Reynolds number from 2.71 · 104 to 4.25 · 105 was observed, being considerably higher compared to conventional tube reactors and twice as large in contrast with a similar rotor-stator setup.



Continuous waste cooking oil transesterification accelerated by microwave heating and adding strontium oxide as the catalyst

2017-09-15T03:10:23.440932-05:00

Biodiesel produced from waste cooking oils (WCOs) mixed with methanol was efficiently transesterified using a continuous-fluid-flow system with a focused microwave heating device. Strontium oxide (SrO) was added as the catalyst. The factors that most affect the biodiesel conversion rate were first estimated by considering the effects of the oil:methanol ratio (1:6), added quantity of SrO (3 wt%), and microwave heating power (500 W) on reaction time in a built-in batch unit. The optimal parameter values were then applied to a continuous-fluid-flow system, which simulates the conversion of a scaled-up quantity of WCOs into biodiesel. Under a fluid flow velocity of 160 mL/min and an appropriate output temperature, a biodiesel conversion rate of ca. 93% was reached. The conversion of WCOs into biodiesel and the reaction rate are based on the transesterification reaction, which is associated with the decomposition of ester bonds and the formation of a tetrahedral intermediate substance.



Reaction Engineering for Continuous Production of Silver Nanoparticles

2017-08-28T02:00:19.298012-05:00

A scalable process for the production of Ag nanoparticles that gives complete conversion of the limiting reactant is analyzed in detail. The kinetics of silver nanoparticle synthesis using citrate reduction are investigated and used for development of a reaction engineering model to facilitate the reactor design. The effect of temperature, pH, concentration and mixing (axial dispersion) on the rates of nucleation and growth are analyzed quantitatively. An approach that considers reaction kinetics coupled with quality of dispersion is developed for reactor design as well as selection of reactor configurations for the synthesis of specific particle sizes. The developed approach has been used for continuous production of 10 L suspension Ag nanoparticles with very narrow particle size distribution.



Reaction Calorimetry for Exothermic Reactions in Plate-Type Microreactors Using Seebeck Elements

2017-08-25T00:40:33.847808-05:00

A flexible reactor and measurement set-up to safely obtain thermokinetic data for exothermic chemical reactions in plate-type microreactors is presented in this work. Precise heat flux measurement is realized by means of Seebeck elements and allows for direct as well as space and time resolved heat flux measurement across the reactor. The microreactor used in this work is manufactured from polyvinylidene fluoride foils and consists of 11 SZ-shaped mixing channel elements. The Seebeck elements are calibrated by Joule effect, while its performance is shown in heat transfer and neutralization reaction experiments. Furthermore, the local resolution enables an estimation of mixing time scale for rapid reactions. A comparison of obtained results indicates good accordance with literature data and is the base of further investigations using the calorimeter.



Rapid degradation of Rhodamine B via a poly (dopamine) modified membrane decorated with Ag nanoparticles

2017-08-25T00:40:30.843454-05:00

Rapid and convenient removal of organic dye from water still remains a great challenge. The study reports the rapid degradation of Rhodamine B (RhB) with NaBH4 as a reducing agent catalyzed by a catalytic membrane fabricated by poly (dopamine) modified PVDF powders and silver nanoparticles (NPs). Results indicate that the catalytic membrane shows an excellent performance for RhB degradation under a static state and cross-flow catalysis. Compared to the static catalysis, cross-flow catalysis can efficiently enhance the degradation of RhB due to the silver NPs and the high flowing rate of reactants on the membrane surface. The penetrated fluid can be directly excluded due to the RhB with a high conversion coming out from the membrane pores with silver NPs. The convenient operation avoids the additional steps to separate catalysts from the system, and therefore has good prospect in degradation of organic dye.



Local Mass Transfer Phenomena and Chemical Selectivity of Gas-Liquid Reactions in Capillaries

2017-08-24T00:55:25.281858-05:00

Gas-liquid reactions in microreactors play an important role in scientific research and industry. Enhancing heat and mass transfer allows overcoming mass transfer limitations in gas-liquid reactions. Mass transfer can be further increased by employing helically coiled capillaries, which induce Dean vortices and improve radial mixing. In this work, a colorimetric technique is proposed for gas-liquid reactions in straight and helically coiled capillaries in order to visualize local mass transfer phenomena and concentration distributions. This method is based on the consecutive oxidation of leuco-indigo carmine and enables non-invasive investigation of mass transfer and chemical selectivity in microchannels with high temporal and spatial resolution.



An Investigation of Blockage Conditions on the Laminated-sheet Microchannel Reactor

2017-08-23T01:10:21.245732-05:00

Microchannel reactor is generally an adopted laminated-sheet structure, in which several microchannel sheets with the same or different structures are laminated together and tightened by welding or other connection methods into a single reaction unit. Uniform velocity distribution among microchannels can improve heat and mass transfer efficiency. When one or more microchannels are blocked, the uniformity of velocity distribution is inevitably affected. In this work, velocity distributions among microchannels in a single-sheet and double-sheet laminated structure under different blockage conditions are investigated. As expected, the velocity values of other microchannels increase when one or more microchannels are blocked. The increase in the magnitude of the velocity is relatively large when there are more blocked microchannels, or near the blocked microchannel, or a small distance from two blocked microchannels. The velocity distribution is symmetrical when two blocked microchannels or two different sheets are centrally symmetrical. A blocked location within a microchannel shows similar effect on the velocity distribution. In the double-sheet laminated structure, a sheet with blockage shows similar effects on the velocity distribution of the other sheet, with or without a blockage. Whether a single-sheet structure or a double-sheet laminated structure is utilized, a more uniform velocity distribution can be achieved when the blocked microchannel is closer to the middle. The sheet without a blockage presents a more uniform velocity distribution in a double-sheet laminated structure. An increase in the number of blocked microchannels results in less uniformity in the velocity distribution. The number of laminated sheets shows little effect on the uniformity of the velocity distribution among microchannels with blockage.



Shell of Planet Earth – Global Batch Bioreactor

2017-08-21T04:10:25.218444-05:00

Planet Earth, precisely speaking its surface shell, might be considered as a huge, multiphase, batch, biochemical reactor heated by the Sun, whose energy is a unique resource. The Sun ensures our earthly life unconditionally; moreover, it compensates the heat losses of the land, water and ice by radiation emitted from the Earth surface to its surrounding space at night. It is evident that in this macro-reactor the complex transport phenomena occurs in many phases; involving mass, heat and momentum. Obviously such a responsive batch system is strongly limited by raw resources of all elements including carbon materials necessary for good living standard and utilized both in the energy production and for industrial main chemical processes.



Transfer Functions for Periodic Reactor Operation: Fundamental Methodology for Simple Reaction Networks

2017-08-17T07:08:40.305808-05:00

The contribution presents a method for frequency response analysis of chemical reactors with periodically modulated inlet concentration. The method is demonstrated for simple first-order irreversible consecutive and parallel as well as reversible reactions applying an isothermal continuous stirred tank reactor (CSTR). The frequency response of these reaction types is studied by simulations in time and frequency domain, being the latter based on Laplace transformation of the material balance. The results allow to clearly distinguish between the quasi and relaxed steady-state as well as the full transient region with impact on designing reactors for dynamic operation. Furthermore, the relation between the dynamic response and the time constants of the system is discussed.



Thermochemical biomass conversion for decentralized power generation with Inverse Brayton Cycle

2017-08-17T07:06:18.757875-05:00

Biomass is a meaningful energy source for the decentralized power generation. The combination of a 2-stage thermochemical conversion unit with an Inverse Brayton Cycle (IBC) is subject to present research activities. Several advantages are expected compared to commercial available concepts. A commercially proven turbocharger from the automotive industry is used for the IBC unit. No cost-intensive gas cleaning is required due to an almost dust and tar free biomass conversion. The influence of feedstock characteristics on the thermochemical conversion, emissions and overall plant performance is subject to process optimization studies. Furthermore validation of the concept is target of a demonstration phase which is planned at later stage of the research activities.



Continuous Hydrogenation of L-Arabinose and D-Galactose in a Mini Packed Bed Reactor

2017-08-17T07:06:14.63824-05:00

The continuous hydrogenation of a mixture of L-arabinose and D-galactose over a Ru/C catalyst was investigated in a miniaturized packed bed reactor. The reaction is one important step of the transformation process of the naturally occurring hemicellulose arabinogalactan (AG) into valuable sugar alcohols. Process intensification was accomplished by reducing the reactor dimensions to a few millimeters, thus leading to better mass and heat transfer performance. The effect of temperature, pressure and liquid flow rate on the yield as well as byproduct formation will be discussed. Based on a kinetic model derived from batch experiments, a model of the continuous reactor was developed and used for scale-up purposes.



A Novel Approach for Measuring Gas Solubility in Liquids Using a Tube-in-Tube Membrane Contactor

2017-08-16T07:16:18.676544-05:00

Data on oxygen solubility in organic solvents are essential for catalyst evaluation, reactor design, and process safety of catalytic aerobic oxidations which is an emerging area in green chemistry. A novel approach using a Teflon AF-2400 tube-in-tube membrane contactor was developed for the measurement of gas solubility in organic solvents. The semi-permeable Teflon AF-2400 membrane ensures gas saturation of liquids in continuous-flow at specific pressure and temperature. After liquid decompression, the amount of gas outgassed was measured with a bubble meter and used for solubility calculation. In this study, this approach was demonstrated for the measurement of oxygen solubility in toluene and benzyl alcohol. Validation experiments were initially performed by comparing the obtained oxygen solubility in toluene with literature data. Then, oxygen solubility in benzyl alcohol was measured at pressures up to 10 bar and temperatures 298 – 393 K. Oxygen solubility in benzyl alcohol at 298 K (Henry's law constant, 3462 bar) was observed to be ~1/3 of that in toluene (1057 bar). With increasing temperature, the solubility of oxygen in benzyl alcohol was found to increase, indicating that the oxygen-dissolving process is endothermic. Finally, an empirical correlation of the Henry's law constant as a function of temperature was determined.



Advanced Operating Strategies to Extend the Applications of Simulated Moving Bed Chromatography

2017-08-08T05:30:24.419674-05:00

Chromatographic separation with solid stationary and fluid mobile phases is widely used to isolate and purify compounds. One of the most productive improvements in preparative chromatography is the simulated moving bed (SMB) process, which enables continuous feed supply and product removal by periodic operation of a multi-column to simulate a counter-current flow between the phases. The SMB process produces high-purity compounds, even with low selectivity, and offers higher productivity and lower eluent consumption than batch chromatography. Recently, intensive efforts have been made to expand the range of applications through the design, modeling, and optimization of the SMB process to produce advanced operating strategies, which are described and evaluated in this paper.



Multi-step Consecutive Photo-chlorination of 1,2-Dichloroethane: Kinetics and Reactive Distillation Experiment

2017-08-07T05:00:29.479307-05:00

The development and validation of a novel kinetic model for the 1,2-dichloroethane chlorination to ultimate hexachloroethane catalyzed by blue light are presented. A factor (Xm) related to chlorination depth was introduced into the kinetics model, and the results showed that the dynamic features of the photo-chlorination are better predicted by the modified model than the conventional one. Furthermore, to enhance the selectivity towards tetrachloroethane and pentachloroethane, a novel reactive distillation with side reactor configuration (SRC) for the photo-chlorination process was proposed. For demonstrating the technical feasibility of the process, semi-batch SRC experiments in a laboratory scale were carried out. Up to 96.5 wt% of tetrachloroethane and pentachloroethane with molar ratios varied from 7 to 0.7 over time were obtained in the bottom product.



Absorption of CO2 with amino acids-based ionic liquids and the corresponding amino acids precursors

2017-08-07T05:00:19.796202-05:00

A comparative study for CO2 absorption among amino acids (AAs) and ionic liquids (ILs) containing Tetramethylammonium [TMA] and Tetrabutylphosphonium [TBP] as cations and the corresponding deprotonated amino acid as anions ([TMA][AA] and [TBP][AA]) is reported. Amino acids show an excellent performance for CO2 capture, better than the corresponding [TMA][AA], but AAs are less efficient than [TBP][AA]. In addition [TBP][AA] present faster kinetic of absorption than the corresponding AA. [TBP][Lysinate] shows the highest CO2 absorption capacity. A novel, fast and low energy demanding method for the microwave-assisted regeneration of the absorbents from the CO2 saturated solution is also described for the first time.



Enhanced CO2 capture performance of limestone by industrial waste sludge

2017-08-04T03:45:51.367901-05:00

Although inert supports have been proved effective to enhance CO2 capture performance of CaO sorbents, more commonly used supports are derived from expensive raw materials (such as nitrates and organometallic precursors). This work utilized cheap waste sludge from the steel plant, which is of a high daily output and has not received effective reuse, to promote the CO2 capture performance. The results showed that the sludge effectively promoted the performance of limestone. Homogeneously dispersed inert material of MgO, acting as the metal framework to resist sintering, was responsible for the enhanced performance. The introduction of waste sludge into the calcium looping could not only improve the sorbent performance, but also provide a potentially effective way to reuse the waste sludge.



Start and Stop Operation of Fixed-Bed Methanation Reactors – Results from Modeling and Simulation

2017-08-04T03:45:30.599852-05:00

The production of SNG from renewable sources in cases requires a dynamic and intermitted operation of the methanation reactors. This may lead to catalyst damage. Therefore, the present work is aiming at identifying restrictions and optimization approaches of the start and stop operation of fixed-bed methanation reactors. 2D modeling and simulation work is conducted and the warm start behavior of a fixed-bed reactor after 1 to 4 hours operation intermittence is analyzed. The analysis reveals the possibility for an operation interruption of up to 4 hours without high adaptation effort to restart the reactor. After approximately 4 hours the catalyst bed at the inlet part of the reactor reaches a temperature that provokes problems for a subsequent warm start.



Formation of Spherical Agglomerates in the Cooling Crystallization of Hexahydro-1,3,5-trinitro-1,3,5-triazine

2017-07-27T00:40:23.899601-05:00

The present work describes the production of spherical agglomerates of Hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX) from acetone by cooling crystallization with polyvinylpyrrolidone (PVP). It was found that PVP suppresses the nucleation of RDX at initial stage, but tremendous nucleation of RDX is occurred abruptly after induction period. The rapid nucleation may be associated with the primary nucleation by the presence of PVP. Thus, it can be concluded that the addition of PVP results in the formation of RDX particles with sufficient number density for spherical agglomeration. It was found that such spherical agglomeration propagates very rapidly after nucleation within a minute and size of spherical agglomerates is affected by cooling rate.



Activity Hysteresis during cyclic TPReactions in the Partial Oxidation of Acrolein to Acrylic Acid

2017-07-26T05:00:40.047872-05:00

Oxidation of acrolein to acrylic acid on Mo/V/W-mixed oxide catalyst was studied by transient (cyclic temperature-programmed (TP)) as well as steady state methods. TPReactions exhibits an activity hysteresis of the catalyst with respect to temperature. As a result of the steady state measurements, the activity hysteresis is not related to multiple steady states and is exclusively a transient phenomenon. Generally, the dynamics of bulk-oxygen plays a key role leading to a reversible oxidation/reduction of the catalyst surface, which influences the activity. This means the bulk acts as oxygen buffer. In this context a reaction model, which contains the participation of bulk-oxygen, has been deduced and verified by modeling.



Homogeneous gas-liquid distribution for monolithic structures via a needle distributor

2017-07-26T05:00:28.623714-05:00

Structured catalysts are a widely discussed approach for process intensification of chemical multiphase reactors. But equal to common catalyst structures homogeneous educt distribution along the catalytic surface is mandatory for high reactor performance. Especially monolithic structures require a homogeneous initial fluid distribution.



Biosorption and binding mechanisms of Ni2+ and Cd2+ with aerobic granules cultivated in different synthetic media

2017-07-06T09:30:20.033689-05:00

Aerobic granules synthesized by feeding real wastewater (R-granules) in a sequencing batch reactor were investigated to remove Ni2+ and Cd2+ from aqueous solutions for the first time. Simultaneously, the results were compared with granules cultivated using laboratory-synthesized wastewater (S-granules). The results showed that metal biosorption was related to the solution pH, initial metal concentration and reaction time. The biosorption capacities for Ni2+ and Cd2+ ions were found to be 101 and 162 mg g-1, respectively. The chemically modified R-granules showed an increased removal efficiency of almost 20% for the examined metals, and the results were almost identical to those of S-granules. Ion-exchange and complexation with extracellular polymeric substances were the predominant mechanisms involved in Ni2+ and Cd2+ loading onto the granules. XPS and FTIR techniques revealed that hydroxyl, carboxyl and amide groups in the S-granules, while carboxyl and hydroxyl groups of polysaccharides in R-granules were mainly associated with binding to Ni2+ and Cd2+. XPS data also exhibited that the oxygen atom in peptide bonds interacted more with heavy metals than the nitrogen atom.



Dynamic membrane filtration: formation, filtration, cleaning and applications

2017-06-29T07:30:18.345127-05:00

In this review, the applications of Dynamic membrane (DM) filtration and factors that affect its formation, filtration and cleaning are introduced. Dynamic membrane has been studied widely in wastewater treatment in recent years. DM formation method and mechanism are explained. In detail, effects of supporting material, deposited material, formation pressure, and pH on the DM formation are discussed. And the effects of operation pressure, aeration intensity, cross-flow velocity, temperature, and other parameters are evaluated in the DM filtration process. Different DM cleaning strategies are reviewed. The applications of DM in municipal wastewater, surface water, oily water, industrial wastewater, sludge treatment, and microalgae harvesting are discussed. Finally, the possible future research directions and some guidelines for DM technology are given.



Location and Network Planning for Modular Container Plants in the Process Industry

2017-01-23T09:10:35.847732-05:00

The application of mobile production units enables the production close to the customers or the raw materials source. The choice of location depends on the demand and requirements of the customers and their geographical distribution. Therefore, economic and qualitative evaluation criteria have to be considered. A method to develop a modular production network, validated in a case study, is presented in this paper.



A Comparative Study of Fuzzy Techniques to Handle Uncertainty: An Industrial Grinding Process

2016-02-03T11:10:07.34826-05:00

The deterministic optimization models for chemical processes assume perfect information, i.e., the system parameters involved in the models should have fixed values. However, the knowledge about these parameters is often either not easy to obtain or, if available, subjected to uncertainty involved in determining them (e.g. experiments, regression etc.). The optimization results obtained using these deterministic models are, therefore, not robust to uncertainties in the parameters of the system. In this work, fuzzy based approaches, e.g. fuzzy chance constrained programming (FCCP) and fuzzy expected value model (FEVM), have been applied to a multi-objective optimization problem of the industrial grinding process to carry out the uncertainty analysis and the results are compared with respect to the power of risk averseness adopted in the approaches used. These methods assume the uncertain parameters as fuzzy numbers and membership function is used to represent the degree of uncertainty in them. The extent of constraint satisfaction due to the presence of uncertain parameters can be accommodated assuming credibility of constraint satisfaction under FCCP framework whereas the robust set of parameters in the FEVM approach is determined by considering the expectation terms for objectives and constraints. Moreover, the issue of nonlinear relation of uncertain parameters has been handled by adopting simulation based approaches while computing the credibility. The results obtained by FCCP technique show how the presence of uncertainty leads to an operating zone of varied risk appetite of a decision maker by using different uncertain measures such as credibility, possibility and necessity. These approaches are very generic and can be adopted for the study of parametric sensitivity for any process model in a novel manner.



Improvement of Bio-crude Oil Yield and Phosphorus Content by Hydrothermal Liquefaction Using Microalgae

2017-09-19T06:08:33.754974-05:00

Hydrothermal liquefaction (HTL) is a thermal depolymerization process used to convert wet biomass such as microalgae into bio-crude oil. Four main products, gas, bio-crude oil, an aqueous phase, and solid residue, are generated through HTL. In this study, various HTL conditions were investigated to enhance the phosphorus content in the aqueous phase as well as the yield of bio-crude oil. Tetraselmis sp. was used as the microalgae feedstock, and the product yields according to catalyst type were explored. The phosphate ion (PO43−) content in the aqueous phase was significantly enhanced when acetic acid was added because of the effect of pH. In addition, it was found that both the bio-crude oil yield and the ammonium ion content could be increased by recycling the post-HTL aqueous phase, while the phosphate content was not. Biofuels produced by microalgae may help to solve the environmental problems associated with the use of fossil fuels. Various hydrothermal liquefaction conditions were investigated for the conversion of wet microalgal biomass into bio-crude oil, with the goal of increasing the phosphorus content in the aqueous phase and the bio-crude oil yield.



An Eulerian-Eulerian Computational Approach for Simulating Descending Gas-Liquid Flows in Reactors with Solid Foam Internals

2017-09-19T04:45:29.133877-05:00

Chemical reactors with new types of packings, such as metallic and ceramic open-pore foams, have become subjects of scientific and engineering interest in the past decades. For trickle bed reactors, the new packing types provide favorable conditions, such as high specific surface area and low pressure drop, which are believed to contribute to an intensification of mass and heat transfer. Here, an attempt was made to model and predict the flow pattern and liquid distribution in a trickle bed reactor with solid foams, using computational fluid dynamics. A three-dimensional model based on the relative permeability approach was adopted, where gas and liquid phases flow co-currently downwards through a reactor with SiSiC ceramic foams as internals. The influence of both mechanical and capillary dispersion was included and studied in detail for foams of two different pore densities and for different initial distribution patterns. A three-dimensional computational fluid dynamics model based on a relative permeability approach was developed in order to simulate the flow through a reactor with ceramic foams as internals. The influence of capillary and mechanical dispersion forces on the liquid distribution was also discussed in detail. The results were validated against experimental data.



Meniscus Asymmetry and Chemo-Marangoni Convection in Capillaries

2017-09-15T02:25:44.687248-05:00

A liquid-liquid system inside a capillary in which an interfacial reaction leads to in situ production of a surfactant was studied experimentally. The resulting chemo-Marangoni convection induces periodic spreading-dewetting cycles in laboratory experiments. By selected experiments in microgravity, the individual phenomena of the system dynamics could be isolated. The spreading-dewetting cycles result from a complex interplay between the decrease in interfacial tension due to the production of surfactant, the chemo-Marangoni convection, and the gravity-driven deformation of the meniscus shape. Marangoni convection is relevant to mass transfer in capillary microreactors. In an experimental capillary setup, surfactant was produced by an interfacial reaction. The resulting chemo-Marangoni convection induced spreading-dewetting cycles. The meniscus deformation is reduced in microgravity, but still exists.



Performance Testing of Hydrodesulfurization Catalysts Using a Single-Pellet-String Reactor

2017-09-14T06:25:29.830882-05:00

Small-scale parallel trickle-bed reactors were used to evaluate the performance of a commercial hydrodesulfurization catalyst under industrially relevant conditions. Catalyst extrudates were loaded as a single string in reactor tubes. It is demonstrated that product sulfur levels and densities obtained with the single-pellet-string reactor are close to the results obtained in a bench-scale fixed-bed reactor operated under the same conditions. Moreover, parallel single-pellet-string reactors show high reproducibility. To study the hydrodynamic effects of the catalyst-bed packing, the catalyst-bed length was varied by loading different amounts of catalysts, and crushed catalyst was also loaded. The hydrodesul-furization of gasoil is a key process in refineries. Small-scale parallel trickle-bed reactors have been used to evaluate the performance of a commercial hydrodesulfurization catalyst under industrially relevant conditions. Catalyst extrudates were loaded as a single string in reactor tubes. The hydrodynamic effects of the catalyst-bed packing were also studied.



Urea Decomposition in Selective Catalytic Reduction on V2O5/WO3/TiO2 Catalyst in Diesel Exhaust

2017-09-12T07:41:27.63564-05:00

Selective catalytic reduction (SCR) of NOx by AdBlue and NH3 on monolithic V2O5/WO3/TiO2 catalyst was studied under flow conditions realistic for diesel exhaust. The tests provided same standard and fast SCR for AdBlue and NH3 from 150 to 350 °C. For standard urea-SCR, axial concentration profiles were checked by monoliths with different lengths evidencing incomplete conversion of urea and isocyanic acid at low temperatures. But SCR was not clearly affected by under-stoichiometric NH3 as substantiated by kinetic analysis. However, above 250 °C, SCR was limited by internal mass transport indicated by Weisz-Prater criterion and lower activation barrier. Formation of deposits was investigated at 175 °C and below showing some urea around the nozzle, whereas cyanuric acid and biuret additionally formed around the catalyst. Selective catalytic reduction (SCR) and NOx storage reduction catalysts are well-known means for the reduction of nitrogen oxides in diesel exhaust. SCR on a traditional monolithic V2O5/WO3/TiO2 catalyst with urea as reducing agent is investigated with major focus on the interaction of SCR reaction and urea conversion over the length of the catalyst at realistic Reynolds numbers.



A Continuous Process for the Purification of Terpenyl Amines Using a Reversible Acid-Base Reaction

2017-09-12T05:00:24.2808-05:00

The reversible reactive extraction of long-chain terpenyl amines (TPAs) using organic acids as reactive extractants was investigated. The scope of suitable acids has been extended and semicontinuous and continuous experiments were performed to prove the applicability of this concept. High extraction yields could be achieved using a variety of acids in batch and semicontinuous experiments. Furthermore, the recovery and separation of the extracted TPAs from the extractant phase has been studied. The TPAs can be recovered in high yields and purities by simple means of process parameter changes. The proposed process allows the separation and purification of TPAs in high yields and purities without the creation of salts or other chemical by-products. Resource-efficient separation techniques are an important process in the chemical industry. The reversible reactive extraction of long-chain amines, here terpenyl amines, in batch as well as in (semi)continuous operation was investigated in detail. The scope of suitable acids was extended and the reversibility of the reaction yielding terpenyl amines in high purity could be demonstrated.



Heterogeneously Catalyzed Hydrogenation of Supercritical CO2 to Methanol

2017-09-12T04:45:32.959382-05:00

Interest in energy storage technologies is still increasing in times of excess of electricity generated by wind farms or solar plants. A key part of the energy storage technologies plays the efficient conversion of H2 and CO2 from renewable resources. Here, the process conditions for continuous catalytic hydrogenation of CO2 to CH3OH under supercritical conditions over lab-synthesized Cu/ZnO/Al2O3 catalysts were investigated. A possible in situ phase separation of reaction products within the reactor due to the higher densities of the reaction mixture by the higher pressure could affect the kinetics and simplify downstream processing. The combination of thermodynamic studies and catalytic performance tests for CO2 hydrogenation under supercritical conditions is discussed and a process concept is presented. Efficient conversion of H2 and CO2 from renewable resources plays a crucial role in energy storage technologies. Process conditions for continuously catalytic hydrogenation of CO2 to CH3OH under supercritical conditions over self-made Cu/ZnO/Al2O3 catalysts were investigated. Higher H2 concentrations, respectively higher H2/CO2 ratios, lead to an increased selectivity of CH3OH.



Gas-Solid Drag Coefficient for Ordered Arrays of Monodisperse Microspheres in Slip Flow Regime

2017-09-11T10:39:47.171569-05:00

Numerous analytical and numerical correlations for the drag force of particles in packed arrays are not applicable to microspheres because of the invalidity of the no-slip assumption at a solid wall. The slip flow through assemblages of spheres is investigated by the lattice Boltzmann method (LBM). Three periodic arrays of static and monodisperse particles, i.e., a simple cubic, a body-centered cubic, and a face-centered cubic array, each with a relatively wide range of solid volume fraction, are considered. The LBM is validated for the slip flow over a single unbounded sphere and the continuum flow through spheres in a simple cubic array. The LBM results agree well with the experimental and numerical data in the literature. Simulations of slip flow through the three ordered arrays of spheres are performed. The effects of solid volume fraction and slip are both quantified within the developed drag laws. The effect of slip on the gas-solid drag force of particles in a packed particle array is still not well understood. The lattice Boltzmann method was applied to investigate the microflow through spheres in periodic arrays in order to quantify the impact of the solid volume fraction and Knudsen number by formulating an innovative drag correlation.



Velocity Uniformity of Microchannels in a Laminated-Sheet Structure Under Parallel and Series Methods

2017-09-11T10:24:25.942343-05:00

An integral microchannel device is generally formed by lamination of multiple microchannel sheets. Uniform velocity distribution among the microchannels in each sheet shows a large influence on the device's performance. The effects of microchannel and manifold structure on the velocity uniformity in each sheet with different structural parameters under parallel and series laminated structures are investigated. For the laminated-sheet structure where each sheet has the same structural parameters, a more uniform velocity distribution exists as compared to where the structural parameters are different. There exists a direct correlation between the velocity values in each sheet and structural parameters, whereas an inverse correlation is found under series laminated structure. The performance of a laminated microchannel device is significantly influenced by the velocity uniformity in each microchannel sheet. Five microchannel sheets with different structural parameters are laminated together by parallel or series method. The impact of the microchannel and manifold structures on the velocity uniformity in each sheet under both laminated methods was evaluated.



CO2 Absorption and Regeneration Using Amines with Different Degrees of Steric Hindrance

2017-09-11T10:22:13.871691-05:00

The influence of steric hindrance in amines upon different characteristics in carbon dioxide chemical absorption, namely, absorption rate, carbon dioxide loading, and regeneration degree, has been analyzed. Aqueous solutions of monoethanolamine, 1-amino-2-propanol, and 2-amino-2-methyl-1-propanol were used to compare their behavior during carbon dioxide absorption. The presence of one or two methyl groups on the carbon next to the amino group produced changes in the analyzed parameters. In addition, the influences of the gas-flow rate and amine concentration on the chemical solvent behavior were studied to improve the mass transfer under different experimental conditions. Carbon dioxide separation by chemical-absorption processes can be used to reduce toxic emissions and enhance carbon dioxide purification. Solutions of sterically hindered amines can be used for this purpose. The influence of steric hindrance in amines on absorption rate, carbon dioxide loading, and regeneration degree during carbon dioxide chemical absorption has been studied.



Transesterification of Canola Oil to Biodiesel Using CaO/Talc Nanopowder as a Mixed Oxide Catalyst

2017-09-11T10:13:54.406052-05:00

A series of heterogeneous catalysts including different molar ratios of CaO/talc was synthesized to study the transesterification reaction of canola oil and methanol under different reaction conditions. Characterization and kinetic results revealed that the activity of this catalyst was enhanced due to the increase of CaO/talc molar ratio value leading to an improvement in the biodiesel production. Moreover, the effect of various parameters on the activity of the undertaken catalysts was studied in order to determine the optimum process conditions. Leaching measurements and the durability of the CaO/talc catalyst under several reaction cycles were evaluated and proved it to be a stable catalyst. Talc nanopowder is a promising heterogeneous catalyst support for transesterification. CaO/talc catalysts were synthesized by a simple wet impregnation method. CaO/talc and CH3OH/oil molar ratios and catalyst amount were optimized. The 3CaO-1talc catalyst achieved higher catalytic activity compared to conventional CaO catalysts and showed a good durability for up to five catalytic cycles.



Development of a Robust Fixed-Bed Reactor Model for Supercritical Citral Hydrogenation

2017-09-08T06:21:53.760953-05:00

The hydrogenation of citral in a fixed-bed reactor by using supercritical carbon dioxide was studied. A numerical model was set up by using the commercial software Aspen Custom Modeler®. By applying literature experimental data, a parameter estimation for the kinetic parameters was carried out. A good fit was reached with the presented model. Furthermore, a sensitivity analysis was performed. The influence of process pressure, inlet CO2 and H2 concentration, and catalyst particle size on conversion, reactor length, space time yield, yield of the intermediate product 3,7-dimethyl-2-octenal, and pressure drop was investigated. Numerical models allow optimization of process parameters for improved performance. Experimental data from the literature are applied in a numerical model for supercritical citral hydrogenation in a fixed-bed reactor to estimate the kinetic parameters. The influence of process parameters on conversion, reactor length, space time yield, yield of the intermediate product 3,7-dimethyl-2-octenal, and pressure drop is discussed.



Esterification of Palm Fatty Acid Distillate Using a Sulfonated Mesoporous CuO-ZnO Mixed Metal Oxide Catalyst

2017-09-07T11:31:13.821135-05:00

A nanocrystalline mesoporous CuO-ZnO hollow sphere was successfully fabricated by the hydrothermal method. The nanocomposite was formed in the presence of polyethylene glycol as a dispersant and D-glucose as a template. The mesoporous CuO-ZnO catalyst was further functionalized with benzenesulfonic acid to catalyze the esterification of palm fatty acid distillate (PFAD). The physicochemical, textural, structural, and thermal properties of the mesoporous CuO-ZnO mixed-oxide catalysts were evaluated. The modified mesoporous catalyst possessed unique textural properties. With a Cu/Zn atomic ratio of 1.0 the best catalytic activity through PFAD esterification was achieved. The optimum reaction conditions in terms of methanol/PFAD molar ratio, catalyst concentration, reaction temperature, and reaction time were determined. A sulfonated mesoporous CuO-ZnO catalyst was synthesized for the production of biodiesel from free fatty acid feedstocks. The modified CuO-ZnO mesoporous catalyst possessed unique textural properties with high specific surface area and better total acid density which helps in the conversion process. More than 96 % of biodiesel yield was attained under optimum reaction conditions.



Dropwise Condensation on Advanced Functional Surfaces – Theory and Experimental Setup

2017-09-06T09:26:20.955074-05:00

Compared to filmwise condensation on conventional condenser surfaces, heat transfer can be significantly enhanced by tuning the wettability of the surface to promote dropwise condensation. Following rapid advances in surface engineering, the last years have seen an unprecedented interest in dropwise condensation research. This brief review highlights recent advances in theory and experimental investigation regarding dropwise condensation on smooth hydrophobic surfaces, micro- and nanostructured superhydrophobic surfaces, biphilic surfaces with patterned wettability, and lubricant-infused surfaces. Research on dropwise condensation has gained a lot of traction in recent years. This review provides an overview on emerging approaches for surface functionalization and the corresponding wetting properties that promote dropwise condensation. The implications for enhanced heat transfer and advances in heat transfer modeling are also discussed.



Enriched Air or Pure Oxygen as Oxidant for Gas-to-Liquid Process with Microchannel Reactors

2017-09-06T09:22:36.677487-05:00

The syngas production step is one of the most costly steps in a gas-to-liquid plant. Commonly, oxygen is used as an oxidant in the reforming step. However, through the introduction of microchannel reactors, the use of enriched air may be justified. The merits of using enriched air versus pure oxygen are analyzed by utilizing an autothermal reformer, with microchannel reactors in the once-through Fischer-Tropsch (FT) step. Pure oxygen is provided by a cryogenic air separation unit (ASU) and enriched air by use of air separation membranes. Pure oxygen requires a smaller FT reactor volume, which means lower reactor costs at the expense of having a costly cryogenic ASU to produce pure oxygen. The operating cost of the ASU is lower than that of the air membrane, but the installed cost is higher. Syngas preparation in a gas-to-liquid plant requires a reforming step usually using oxygen as oxidant. Here, enriched air or pure oxygen are compared as such. Due to safety and space issues related to the use of a cryogenic air separation unit offshore, the only viable option is the use of enriched air, whereas in an onshore setting, the use of oxygen is more attractive.



Application of Microwave Irradiation for Preparation of a KOH/Calcium Aluminate Nanocatalyst and Biodiesel

2017-09-06T03:00:42.749286-05:00

Microwave combustion was applied for the fabrication of KOH/calcium aluminate for microwave-enhanced biodiesel production. The effect of calcium nitrate and potassium hydroxide dosages on the properties and activities of samples was assessed. When the Ca/Al ratio was increased, the activity was enhanced probably due to the transformation of the sample to an active mayenite structure. The activity of the sample was reduced by a higher KOH loading as a result of covering the surface and porosity of the support by potassium components. The optimum sample was utilized in the transesterification reaction by two heating systems where the microwave irradiation reduced the reaction time drastically as compared to the conventional heating system. The sample converted canola oil to methyl ester nearly completely and showed high stability via calcination after each usage. Microwave chemistry is increasingly applied, e.g., in heterogeneous catalyst preparation. KOH/calcium aluminate as a strong solid-base catalyst for microwave-enhanced biodiesel production was synthesized by microwave combustion. The effects of CaO and KOH dosages and calcination temperature on the structure and performance of the nanocatalysts was evaluated.



Experimental Investigation on Gas-Solid Behavior in Fluidized Beds with Superfine Particles

2017-09-05T12:00:28.587619-05:00

Fluidized beds are commercially utilized in gas-solid contacting processes such as the fluid catalytic cracking (FCC) process. Attempts have been made for bubbling fluidized beds to enhance the gas exchange between the bubble phase and the emulsion phase as well as to increase bubble holdup. Low-density superfine particles 5070S were selected with average diameters of about 10 μm. Unlike agglomerate particulate fluidization of superfine particles on which other researchers have reported, the smaller bubbles, whose diameter is less than 10 mm, uniformly dispersed in the whole bed. Additionally, the gas exchange rate with 5070S became larger than with the FCC particles. Such a unique gas-solid behavior is probably due to the proper density difference between particle aggregate and fluidizing gas. Fluidized beds are widely used in gas-solid contacting processes, but the gas exchange between bubble phase and emulsion phase still is not optimized. The possibility of applying low-density microparticles for a gas-solid fluidized-bed reactor with higher contact efficiency is demonstrated. Hollow borosilicate glass microparticles were successfully employed as superfine particles for fluidization.



Multi-objective Optimization-Tool for the Universal Application in Chemical Process Design

2017-09-05T09:00:47.697717-05:00

A universally applicable procedure for multi-objective optimization of chemical processes is developed. A set of known methods and procedures is adapted, combined with newly developed concepts, and integrated into the developed optimization tool, namely, the Adv:ProcessOptimizer. It allows for efficient, comfortable, and robust optimization of a process which is modeled in one of the various linked commercial simulation tools. As a result, the application of the process design with an overlaid optimization is easily accessible for academia and process industry. The industrial styrene process was optimized in order to validate the method. The results show a very densely and mostly equally crowded Pareto front and considerable savings in investment as well as operating costs compared to two reference designs. The multi-objective optimization of processes is an important field of current research activities in academia and industry. A universally applicable, efficient, and robust optimization tool, the Adv:ProcessOptimizer, was developed. The industrial styrene process was optimized in order to validate the method by comparing the achieved optimization results with reference designs from literature.



Analysis of In Situ Microscopy Images of Flocculated Sediment Volumes

2017-09-01T05:05:23.893924-05:00

An in situ microscopy method was employed to study the sediment volumes that result from batch settling of polymer-flocculated kaolin suspensions. Statistical methods were applied including chord length distributions, perimeter-based fractal dimension of the void areas, white area image ratio, and gray level co-occurrence (GLCM) features. Several GLCM features have a good linear relationship with aggregation state, and the parameters of aggregate and void chord distributions can be interpreted to help explain the flocculation results. The methods applied here are suggested for the measurement of the aggregation state or relative aggregate volume on bench or industrial scale when the settled suspension interface is not available, such as in a continuous process or reaction. In situ nondestructive methods to determine properties of aggregates in networked suspensions are rare. The correlation between statistical image features and aggregation state in polyacrylamide-flocculated kaolin suspensions is evaluated by comparing microscopic images of the settled bed of aggregates with the accurately measured bed height to determine the sediment volume.



Coke Slurries with Improved Higher Heating Value and Good Processability via Particle Shape Design

2017-08-31T01:35:46.917902-05:00

Coke-water slurries can be used as biogenic intermediates in conversion of residual biomass into high value fuels such as liquefied petroleum gas or synthetic natural gas. The effect of particle size and shape on the flow behavior of slurries including coke particles obtained from fast pyrolysis was investigated. Particles were shaped in a planetary ball mill and equivalent sphere diameter and circularity were used to characterize size and shape. An increased circularity resulted in a strong decrease in slurry viscosity. Accordingly, a higher mass fraction of particles can be mixed into the slurry, thus, increasing the higher heating value while still preserving good processing properties. The effect of particle size and shape on the flow behavior of carbonaceous slurries is investigated. With increasing circularity, as obtained by particle milling, a strong decrease of slurry viscosity is achieved. Accordingly, a higher mass fraction of the treated particles can be mixed into the slurry, thus, increasing the higher heating value while still preserving good processing properties.



Asymmetrical Microchannel Emulsification Plates for Production of Small-Sized Monodispersed Emulsion Droplets

2017-08-29T11:20:44.37312-05:00

Monodispersed emulsion droplets have promising advantages in food, pharmaceutical, and chemical industries. Previous microchannel emulsification (MCE) plates having the capacity of generating small-sized droplets exhibited very low droplet productivity since these plates operate at a low dispersed-phase flow rate and with a relatively small number of microchannels. An innovative MCE plate with 176 176 circular asymmetric through-holes was manufactured, which is comprised of a series of discrete outlets on each microchannel line with an effective cross-sectional area of 1 cm2. The newly fabricated MCE plate is capable to produce monodispersed emulsion droplets with small Sauter mean diameters. Microchannel emulsification is a progressive technique for production of monodispersed emulsion droplets with great potential in food, pharmaceutical, and chemical industries. An asymmetrical straight-through microchannel emulsification plate for generation of small uniform droplets with higher productivity was designed, intended for mass production of monodispersed small-sized droplets.



Effects of Solids Concentration and Underflow Diameter on the Performance of a Newly Designed Hydrocyclone

2017-08-21T08:20:26.972788-05:00

Solid-liquid and liquid-liquid separations in a hydrocyclone are versatile and require low maintenance costs. The demand for process improvement and cost reduction has motivated numerous optimization studies. The performance of a newly designed hydrocyclone is evaluated. The proposed device was obtained by application of differential evolution techniques and is called optimized thickening hydrocyclone (OTH). The OTH provides promising results, leading simultaneously to low Euler numbers and high solids concentrations of the underflow streams. Compared to the conventional Rietema hydrocyclone, it shows higher efficiency and better thickening power. The effects of solids concentration and underflow diameter on the performance of the OTH are quantified and a design equation for this device is proposed. Hydrocycloning is considered a versatile and simple process with low acquisition and maintenance costs. The effect of solids concentration and underflow diameter on the performance of a hydrocyclone with optimized geometry is evaluated. The optimized thickening hydrocyclone provides lower energy consumption, higher efficiency, and a better thickening power compared to a traditional hydrocyclone.



Extended Elution by Characteristic Point Method for Characterization of Protein Ion-Exchange Adsorption

2017-08-11T04:45:47.855598-05:00

An adequate characterization of adsorption isotherms is mandatory for chromatographic process development. Here, the elution by characteristic point (ECP) is a suitable method with low consumption of material and time. However, the ECP method requires a highly ideal behavior of the measured system. An innovative extended ECP approach is presented to characterize a non-ideal system by the example of protein ion-exchange adsorption. A marker, here bovine hemoglobin, is used to quantify all non-idealities, e.g., convection, dispersion, or low number of theoretical plates. The system signal of the marker is used to compensate the system signal of the interesting solute, here bovine serum albumin. The resulting isotherm agrees well with the control results of a validated static approach. For development of chromatographic processes, suitable characterization of adsorption isotherms is compulsory. An innovative extended elution by characteristic point (ECP) method is presented as a rapid approach for the characterization of bovine serum albumin adsorption onto Q Sepharose FF. The proposed method has high potential for screening, requiring only small amounts of solute and adsorbent.



Synthesis of Polyoxymethylene Dimethyl Ethers Catalyzed by Pyrrolidinonium-Based Ionic Liquids

2017-08-11T02:30:45.490661-05:00

Polyoxymethylene dimethyl ethers (PODEn) are widely applied as diesel additives in engines. Ionic liquids (ILs) replace traditional liquid acids as catalysts in chemical processes. A series of pyrrolidinonium-based Brønsted acidity ILs were synthesized, investigated, and employed as catalysts for the synthesis of PODEn from methylal and trioxane for the first time. The Hammett function values were measured to uncover the connection between catalytic performance and acidity-activity of the ILs considered. The optimal experimental conditions for the synthesis of PODEn were determined. The maximum values of both the conversion of raw material and the selectivity of PODE3–8 were obtained with 1-octyl-2-pyrrolidinonium trifluoromethanesulfonate ([NOP][TFO]) as the catalyst. [NOP][TFO] provides greater selectivity of PODE3–4 than the traditional catalysts such as H2SO4 and CF3SO3H. Polyoxymethylene dimethyl ethers (PODEn) are environmentally friendly additives for diesel which improve the thermal efficiency of diesel and reduce the emission of particular materials. A series of pyrrolidinonium-based Brønsted acidity ionic liquids were successfully synthesized and applied as catalysts for the synthesis of PODEn from methylal and trioxane for the first time.



Experimental and Numerical Study of Grinding Media Flow in a Ball Mill

2017-08-07T12:21:32.66204-05:00

An experimental and numerical study on the grinding media dynamics inside a baffled ball mill under different solid-flow regimes, namely, cascading, cataracting, and centrifuging, is described. The Eulerian approach was used for all simulations and the boundary condition at the drum wall was investigated by means of the specularity coefficient parameter. This effort is an important approach in representing the particle-wall interaction in a ball mill. The restitution coefficient of the balls was experimentally measured using a video camera, and its influence was evaluated by comparing the numerical and experimental outcome of flow patterns. The simulations results proved that the specularity and restitution coefficients effects at the drum wall were more evident at high rotational speeds. In order to properly assess particle movements in a ball mill, the choice of a suitable wall boundary condition is of fundamental importance. The grinding media dynamics in a ball mill with lifters was analyzed experimentally and numerically. Under cascading, cataracting, and centrifuging solid-flow regimes, the effects of specularity and restitution coefficients were evaluated.



Slurry Utilization and Impact of Mixing Ratio in Biogas Production

2017-08-03T06:00:25.808327-05:00

The anaerobic conversion of waste to biogas in a biogas digester is influenced by a number of factors including mixing ratios, type of substrate, temperature, organic loading rate, pH, and carbon/nitrogen ratio. The appropriate mixing ratio of water and animal waste leads to effective biogas yield. Different mixing ratios proposed in literature for various animal waste for improving biogas yield are reviewed. Characterization and application of animal slurry, the choice of animal slurry as suitable feedstock for biogas production, the storage of animal slurry, the agitation process of slurry as well as mixing ratios of animal slurry are evaluated. Animal manure is a key organic matter with potential to produce renewable fuels through anaerobic digestion and reducing greenhouse gas emissions, especially methane. The usage of animal slurry for producing biogas and fertilizer is reviewed. Anaerobic conversion of waste to biogas in biogas digesters is influenced by various factors. The mixing ratio of waste and water is a decisive factor.



Design and Control Comparison of Alternative Separation Methods for n-Heptane/Isobutanol

2017-08-03T04:25:32.869311-05:00

The binary mixture of n-heptane and isobutanol forms an azeotrope at atmospheric pressure, with a composition of 66.9 mol % n-heptane and a temperature of 364 K. Several methods of separation are possible. This study compares the steady-state economics and the dynamic controllability of three alternative separation techniques: a two-column extractive distillation process, a two-column pressure-swing distillation process, and a single column with a refrigerated condenser. Three methods for separating the azeotropic n-heptane/isobutanol system are compared in a quantitative economic and controllability study: a two-column extractive distillation process, a two-column pressure-swing distillation process, and a single column with a refrigerated condenser. Lower capital investment and simplicity of design and operation mark the single column as the best alternative.



Optimization of Settling Behavior for an Efficient Solvent-Extraction Process for Biobased Components

2017-08-03T04:25:25.426768-05:00

Extraction is a downstream process option in biobased processes. Because knowledge of phase-separation behavior is essential for designing efficient separation processes, this study investigates the settling and coalescence behavior of biobased extraction systems by using a standard laboratory-scale settling cell. The influence of different buffer media and Escherichia coli cells on coalescence was determined for the reactive extraction of hexane-1,6-diamine with isostearic acid and di(2-ethylhexyl)phosphoric acid by using kerosene and oleyl alcohol as diluents. As a result, an increasing pH value of the buffer significantly increases the settling time. The presence of E. coli cells hinders phase separation of the investigated systems, in particular, with dispersed organic phases. The design of efficient separation systems requires knowledge of phase-separation behavior. Factors that influence the settling and coalescence behavior of biobased extraction systems by using a standard laboratory-scale settling cell are discussed. Key interdependent process parameters include pH, amount of reactive extractant, direction of dispersion, and phase ratio.



Length-to-Diameter Ratio of Extrudates in Catalyst Technology: III. Catalyst Breakage in a Fixed Bed

2017-08-02T09:10:22.638341-05:00

A correlation is demonstrated to predict the reduction in the mean length-to-diameter ratio of catalyst extrudates by breakage due to stress in a fixed bed. The stress can be caused either by the reactor load or it can be externally applied as in the bulk crush strength measurement. The strength characteristic of particular interest here is the extrudate bending strength characterized by the Euler-Bernoulli modulus of rupture. The balance of the bending strength to the applied stress leads to a new dimensionless group. Extrudates in a fixed bed start to break above a specific critical stress, and their mean length-to-diameter ratio then becomes linearly proportional to this dimensionless group to the power one-third. The modulus of rupture is able to tie the resilience to breakage of extruded catalysts to the severity of the compressive load in a fixed bed. The bending strength further permits to predict the formation of fines during comminution. The analysis shows that a dimensionless group is at the core of the breakage behavior of the catalyst.



Kinetics of CO2 Adsorption/Desorption of Polyethyleneimine-Mesoporous Silica

2017-08-01T06:07:16.358307-05:00

The kinetics of adsorption of CO2 on solid sorbents based on polyethyleneimine/mesoporous silica (PEI/MPS) was studied by following the mass gain during CO2 flow. Linear (PEI-423) and branched (PEI-10k) polymers were studied. The solid sorbents were synthesized by impregnating the PEI into MPS foam. The kinetics of adsorption was fitted with a double-exponential model. In contrast, the desorption process obeyed first-order kinetics. The activation energy of desorption of PEI-423 was lower than that of PEI-10k, presumably because the branched polymer required more energy to expose its nitrogen to CO2. To increase the CO2 sorption capacity, the MPS was treated with nonionic surfactant materials prior to impregnation with PEI. This also lowered the maximum sorption temperature and desorption activation energies. Increasing levels of CO2 emissions from natural gas streams and burned fossil fuels are a serious environmental concern. Therefore, removal of CO2 is necessary. A kinetic investigation of CO2 adsorption/desorption has been carried out on sorbents with and without surfactants. Unlike most of the previous kinetic treatments reported, the present model aims to specifically distinguish between surface and bulk adsorption processes.



Thermal Conductivity Measurement of Bulk Solids

2017-07-28T03:55:33.7295-05:00

The coefficient of thermal conductivity of particulates and powders is of great importance in process engineering. The prediction of thermal properties of powders using empirical equations is still difficult due to the wide range of specific attributes. This article describes a new measurement methodology for a laboratory device that can be used to determine the thermal conductivity of bulk solids. The presented results show that the created device is highly applicable in industrial practice. It is possible to examine the coefficient of thermal conductivity depending on the sample temperature, the granulometry results and the morphological composition, the moisture content, the degree of consolidation, and other variables that may enter into the entire process and affect it significantly. Knowledge of thermal properties is a key part of process-based systems for the cooling or heating of particulates. Accurate measurement and characterization of the thermal conductivity of bulk materials can pose a number of problems. An experimental device was assembled for measuring the thermal conductivity coefficient k of bulk solids used in processes requiring knowledge of this physical quantity.



CO2 Methanation on Nickel Catalysts Supported on Mesoporous High-Surface-Area MgSiO3

2017-07-26T06:26:19.045641-05:00

Nickel catalysts prepared on high-surface-area mesoporous MgSiO3 were synthesized and applied in methanation of CO2. N2 adsorption analysis confirmed the presence of the mesoporous structure on the synthesized samples and revealed that the increase in nickel content resulted in a shift of the pore size distributions to smaller pore sizes. Temperature-programmed reduction analysis illustrated an improvement in reducibility of the catalysts by a higher nickel content. Catalytic results indicated enhanced CO2 conversion with the increase in nickel percentage up to 15 wt %. The catalysts with higher percentage of nickel provided lower CO2 conversion and CH4 selectivity. The %15Ni/MgSiO3 catalyst exhibited high catalytic stability under optimized conditions. For methanation of CO2, catalysts with high catalytic activity and stability at low and high temperatures are required. Nanostructure magnesium silicate with high surface area was synthesized hydrothermally as support for the preparation of nickel-based catalysts in CO2 methanation. A %15Ni/MgSiO3 catalyst exhibited high catalytic activity and stability in methanation reaction.



Effect of Acetonitrile-Based Crystallization Conditions on the Crystal Quality of Vitamin D3

2017-07-26T02:16:04.777914-05:00

To design an integrated continuous crystallization setup that is directly coupled to a photochemical synthesis in flow, the crystallization of vitamin D3 was studied in detail. Because of the high solubility of the vitamin in the reaction solvent tert-butylmethyl ether, a solvent swap to acetonitrile was necessary. While other methods use a multistep procedure, with the proposed approach, crystalline vitamin D3 can be obtained within one crystallization step. The influence of crystallization parameters, such as the initial concentration of vitamin D3, stirring as well as cooling temperature, rate, and time, on the obtained results in terms of yield, crystal shape, polymorphism, and particle size distribution are discussed in detail. The crystallization process of vitamin D3 and the way how to directly obtain different qualities and types of crystal polymorphs are still not well understood. All relevant crystallization process conditions were evaluated and an integrated continuous crystallization setup directly coupled to a photochemical synthesis in flow was applied to study the crystallization of vitamin D3 in detail.



Simulation of a Bubble Column by Computational Fluid Dynamics and Population Balance Equation Using the Cell Average Method

2017-07-25T07:36:03.598316-05:00

An axisymmetric computational fluid dynamics (CFD) simulation coupled with a population balance equation (PBE) has been applied in simulating the gas-liquid flow in a bubble column with an in-house code. The novel feature of this simulation is the application of the cell average method in a CFD-PBE coupled model for the first time. The predicted results by this method are compared with those by the traditional fixed pivot method and experimental data. For both methods, the simulated results are in reasonable agreement with the reported experimentally measured values. However, the bubble size distributions determined by the cell average method are slightly better than those found by means of the fixed pivot method, i.e., the latter provides a smaller peak value and a wider bubble size distribution, and the probability density function of large bubbles is higher. The population balance equation (PBE) is increasingly utilized with computational fluid dynamics (CFD) to account for the effects of bubble size distribution on the hydrodynamic behavior of multiphase systems. A complete CFD-PBE coupled simulation on the gas-liquid system in a bubble column realized the first application of the cell average method to such a coupled model.



Development of a Model for Water Scrubbing-Based Biogas Upgrading and Biomethane Compression

2017-07-18T06:55:30.067272-05:00

Biomethane is an easily storable, renewable energy source that is applicable to the sectors electricity, heat, and transport. It is mostly obtained from biogas by different upgrading technologies. At present, the most common technology is water scrubbing because of its reliability and simplicity. A methodology for designing as well as for evaluating and optimizing water scrubbing plants including biomethane compression is introduced. To demonstrate possible applications of this methodology, a zero-emission water scrubbing process characterized by under-pressure regeneration of washing water is modeled and investigated by a sensitivity analysis.A methodology for design, evaluation, and optimization of water scrubbing plants including biomethane compression is introduced. A water scrubbing system including washing water regeneration by under-pressure desorption and biomethane compression is modeled and investigated. This system configuration can be operated with zero emissions when the CO2-rich gas from the desorption column is utilized.



Thermodynamic Properties of Ionic Semiclathrate Hydrate Formed with Tetrabutylammonium Propionate

2017-07-17T08:50:29.229935-05:00

The phase equilibrium temperature and dissociation heat of tetrabutylammonium propionate (TBAPr) hydrate are reported. TBAPr hydrate is a type of ionic semiclathrate hydrates and also could potentially be used as thermal energy storage material. The temperature-composition phase diagram of the TBAPr hydrate was determined in a defined range of mass fractions. Considering the dissociation heat of differential scanning calorimetry (DSC) measurements, multiple peaks of heat flow were observed in the TBAPr-water system at the TBAPr mass fraction lower than 0.35, and there was a single peak at the mass fraction higher than 0.37. Ionic semiclathrate hydrates are considered as promising thermal energy storage materials for energy derived from renewable energy technologies. The phase equilibrium temperature and dissociation heat of tetrabutylammonium propionate hydrate were determined in order to evaluate its suitability as thermal energy storage material for air conditioning of data centers.



Process Intensification of n-Butane Oxidation to Maleic Anhydride in a Millistructured Reactor

2017-07-06T05:37:31.246183-05:00

The oxidation of n-butane to maleic anhydride over an industrial vanadyl pyrophosphate oxide catalyst was investigated experimentally in millistructured reactors with varying slit widths to investigate the process intensification potential of this reaction. Although the smaller reactor behaved isothermally, even in the presence of high n-butane concentrations, moderate hot spots never exceeding more than 15 K above the salt bath temperature occurred in the larger catalyst channel. After exposure to high n-butane concentrations, a certain amount of catalyst deactivation was observed, which could be partly restored through reoxidation with pure oxygen. The reactor-specific maleic anhydride productivities obtained are much larger than those in conventional multitubular reactors. Micro- and millistructured reactors are a promising technology for the purpose of process intensification. Results are presented for the highly exothermic, heterogeneously catalyzed, gas-phase oxidation of n-butane over a commercial vanadyl pyrophosphate oxide catalyst conducted in the explosive regime. Reactor productivities can be significantly increased compared with those of multitubular reactors.



CO2 Capture from Air Using Amine-Functionalized Kaolin-Based Zeolites

2017-06-28T01:50:38.19231-05:00

Several inexpensive zeolites such as ZSM-5 (MFI), zeolite Y (FAU), and SAPO-34 (CHA) were developed from kaolin clay and applied for CO2 capture from air. These molecular sieves were functionalized with tetraethylenepentamine (TEPA) in order to further improve their CO2 capacity. The obtained kaolin-based zeolites exhibited similar properties than those of zeolites prepared with other sources. They also revealed a bimodal pore network consisting of both micropores and mesopores. The effect of amine loading on CO2 capture was investigated and the results demonstrated that TEPA-modified zeolite Y with 10 wt % TEPA had a higher capacity than other zeolites due to its larger mesopore volume. The presence of mesopores in the zeolite Y framework facilitated a better accessibility of CO2 molecules to the amine sites. The development of bimodal pore-network zeolites from a cheap and abundant source such as kaolin clay is of practical importance in various processes related to separation and catalysis. Different zeolites were synthesized from kaolin clay and evaluated for CO2 adsorption from air. The subsequent functionalization of these materials is largely dependent on their porosity and pore network.



Biodiesel Purification Using Polymeric Nanofiltration Composite Membranes Highly Resistant to Harsh Conditions

2017-06-23T04:15:19.431551-05:00

Biodiesel as alternative for conventional diesel fuel is mainly produced by the catalytic reaction of triglycerides with an alcohol. In this work, the purification of biodiesel was carried out with two lab-made solvent-resistant composite nanofiltration membranes of poly(vinylidene difluoride) (PVDF) as support and poly(dimethylsiloxane) as coating layer. Biodiesel was obtained from the esterification of partially refined soy oil with bioethanol (EtOH) and NaOH as catalyst. The best biodiesel purification performance was achieved with the PVDF-12SI membrane reaching high retention of glycerol, total glycerides, and soap. PVDF-SI membranes were found to have an excellent stability for biodiesel permeation, achieving a flux recovery ratio of EtOH as high as 0.94 after twenty cycles of use. Nanofiltration polymeric membranes are considered as a feasible and efficient way for the purification of biodiesel. Two lab-made solvent-resistant composite nanofiltration membranes were evaluated for optimum purification performance, achieving high retention of glycerol, total glycerides, and soap. The membranes exhibit a high stability even under harsh conditions.



Hydrodynamics and Mass Transfer of Gas-Liquid and Liquid-Liquid Taylor Flow in Microchannels

2017-06-07T04:00:29.285959-05:00

Hydrodynamics and mass transfer of both gas-liquid and liquid-liquid Taylor flow simulation in microchannels are reviewed. Theoretical approaches for description of hydrodynamic parameters and mass transfer characteristics are corroborated by comparison with available experimental results. Similarities and peculiarities of liquid-liquid flows versus gas-liquid Taylor flows in capillaries are discussed. Tools of mass transfer intensification of gas-liquid and liquid-liquid Taylor flow in microchannels are analyzed and optimal process conditions for gas-liquid Taylor flows are evaluated. A review is given on mathematical modeling of hydrodynamics and mass transfer of gas-liquid and liquid-liquid Taylor flows in microchannels by means of a theoretical approach using classical equations and modern formulae necessary to close the model. The state of the art of process intensification in mini- and microchannels and optimal process conditions for gas-liquid Taylor flows are evaluated.



Offshore Floating Packed-Bed Reactors: Key Challenges and Potential Solutions

2017-05-16T04:33:44.505082-05:00

The influence of floating vessel motions on the hydrodynamic behavior of multiphase flows in porous media was studied using a hexapod ship motion emulator with an embarked packed column. The response of gas-liquid distribution, pressure drop, liquid saturation, and flow regime transition to column inclinations and roll motions was compared to those of the corresponding static vertical and inclined configurations. Two-phase flow patterns in terms of local liquid saturation distribution were visualized online by means of a capacitance wire-mesh sensor positioned firmly on the floating packed bed. The hydrodynamic performance of packed beds under roll motion deviates strongly from that of the static beds, indicating that the known characteristics of the conventional land-based trickle-bed reactors cannot be transposed on a one-to-one basis for design and scale-up of the floating reactor configurations. Packed beds are embarked on mobile offshore platforms for onboard treatment and refining of hydrocarbons extracted from undersea reservoirs. The effects of offshore floating platform motions on the hydrodynamic behavior of multiphase flows in porous media were investigated. Ship rolling motions cause periodic gas-liquid segregation and induce transverse displacements in two-phase flow packed beds.



Cover Picture: Chem. Eng. Technol. 9/2017

2017-08-24T13:02:43.111406-05:00

Image of multicolored broken glass. Copyright: riccardo livorni@Shutterstock



Editorial Board: Chem. Eng. Technol. 9/2017

2017-08-24T13:02:53.027024-05:00




Overview Contents: Chem. Eng. Technol. 9/2017

2017-08-24T13:02:51.607704-05:00




Highlights: Chem. Eng. Technol. 9/2017

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Particle and Powder Technology – Industry Meets Science at PARTEC

2017-08-24T13:02:51.830326-05:00

No abstract.



Process Chain for the Fabrication of Nanoparticle Polymer Composites by Laser Ablation Synthesis

2017-04-06T07:56:04.292174-05:00

Nanoparticle polymer composites are of growing interest due to their unique properties. However, conventional composite synthesis methods usually require several process steps including steps for cleaning and improving the particle-matrix dispersion. As an alternative, laser ablation synthesis can be used to prepare tunable composite materials. This method enables an easy process chain, without the need of additional steps. In this status report, the process chain of laser-based pre-series fabrication of nanocomposites is visualized, and the increase of the method's technology readiness level is demonstrated. The process steps are demonstrated from the synthesis of the colloid to applicable functional products. The advantages of using laser ablation for nanocomposite synthesis are highlighted. Laser ablation synthesis is presented as an alternative route to prepare tunable composite materials. The process chain of laser-based pre-series fabrication of nanocomposites is illustrated and the increase of the technology readiness of this method is demonstrated. The process steps are presented starting from the synthesis of the colloid to applicable functional products.



Population Balance Equation of Cohesive Particle Flow in a Circulating Fluidized Bed

2017-05-11T08:35:37.13601-05:00

A novel model coupled with a population balance equation is adopted for simulating the aggregation process and flow behavior of cohesive powders in a full-loop circulating fluidized bed. The agglomerate diameter is calculated according to the change of particle number by a population balance equation which is solved as a part of computational fluid dynamics simulation. The solid pressure and viscosity are redefined by taking the effect of interparticle force into consideration based on the kinetic theory of granular flow. Simulation results of time-averaged solid volume fraction and diameter of agglomerate are predicted by a numerical method and are in reasonable agreement with experimental data. The variation of mass flux, solid pressure, and viscosity under different operating conditions are analyzed based on the proposed model. Aggregation process analysis is essential to predict the flow behavior of agglomerates for better design and operation of circulating fluidized beds. An innovative model coupled with a population balance equation is applied to simulate the flow of cohesive powders in a full-loop circulating fluidized bed and opens a further perspective to solve the problem with population change in such systems.



Dynamics of Capillary Wetting of Biopolymer Powders

2017-07-25T08:00:27.485684-05:00

The rehydration behavior of biopolymer powders was investigated. Problems that arise during powder rehydration, e.g., floating and formation of particle aggregates, are mainly attributed to the dynamics of capillary water uptake. Common methods for analysis are too slow to assess the fast changes and do not allow conclusions about causal relationships. For a more detailed understanding, relevant powder properties were investigated. Results show that viscosity development in the rehydration liquid as well as swelling, and in particular their dynamics, are crucial for powder rehydration. The dynamic capillary rise was modeled based on the Washburn equation and results were linked to the physical powder characteristics. The approach allows the evaluation, whether viscosity or swelling effects lead to a critical rehydration behavior. Food powders are generally rehydrated before further industrial processing or consumption. Rehydration of biopolymer powders was studied with special focus on their physical properties. Methods to investigate the dynamic wetting situation were developed. A volume-of-fluid approach was used to simulate powder rehydration, integrating results from physical characterization.



Enhancement of the Mechanical Properties of Nanoparticulate Thin Coatings via Surface Modification and Cross-Linking Additive

2017-08-02T03:10:52.362484-05:00

The application of modified Al2O3 nanoparticles for thin coatings is investigated to improve especially the mechanical characteristics by cross-linking the particles using an additive, together with the formulation parameters as well as the cross-linking kinetics. In general, the experiments demonstrate that the mechanical properties, like hardness and scratch resistance, can be enhanced via particle surface modification in combination with a cross-linking additive. Specifically, the optimal additive concentration was determined in order to obtain coatings with improved mechanical and constant optical properties. These results were related to the structure formation and cross-linking behavior. Mechanisms were identified for this series of experiments to explain how the particles bond with each other and how the coating structure is formed by using different additive ratios. The beneficial effect of modified alumina nanoparticles in combination with a cross-linking additive to produce thin coatings with enhanced mechanical properties like hardness as well as higher scratch resistance is evaluated. Mechanisms regarding particle networking as well as coating structure formation were identified in dependency of the additive ratio.



Colloidal Stability of Metal Nanoparticles in Engine Oil under Thermal and Mechanical Load

2017-08-08T02:15:44.328515-05:00

Extended colloidal stability and high dispersion degree of nanolubricants are required to avoid nanoparticle deposition in combustion engines and to reduce friction and wear. The simple and rapid one-step technique of pulsed laser ablation in liquids is employed to synthesize precursor-free and highly dispersed gold nanoparticles in lubricants while the colloidal stability is measured by optical spectroscopy and transmission electron microscopy. A remarkable colloidal stability is determined under engine-like and ambient conditions for nine months in terms of constant primary particle size. In contrast to additive-free oils, almost no agglomeration is observed, which might be attributed to the attachment of engine oil additives or pyrolyzed/oxidized molecules to the nanoparticles preventing attractive nanoparticle interactions. Nanolubricants with prolonged colloidal stability and high dispersion degree are essential to avoid nanoparticle deposition in combustion engines and to diminish friction and wear. Highly dispersed nanolubricants are synthesized in one step by pulsed laser ablation of gold in engine oil and show remarkable stability without agglomeration formation even under harsh engine-like conditions.



Separation Characteristics of Crystalline Amino Acids with Regard to the Modularization Idea

2017-08-03T04:25:54.188026-05:00

In the chemical and pharmaceutical industry, a fast and efficient market launch is important to withstand global competition. Apart from the innovation of new products, the development of an appropriate production line is time-consuming. Modularization can accelerate the design and commissioning of a production plant. Herein, representative of a pharmaceutical process, the production, precisely the solid-liquid separation, of amino acids is considered. Therefore, the separation behavior of different amino acid systems and variations within solid systems are examined. With this information, a production plant is designed and differences regarding the amino acid systems are identified. Modularization of functional operation units in process development is a promising approach for the acceleration of the time to market in the chemical and pharmaceutical industries. Therefore, different types of amino acids are considered with regard to their separation behavior to investigate the applicability of this approach in solid-liquid separation.



Crystal Population Growth in a Continuous Helically Coiled Flow Tube Crystallizer

2017-08-10T00:50:20.444076-05:00

A helically coiled flow tube crystallizer was investigated as a novel device for the shape-selective generation of crystals with potassium alum as the model solid. The shape evolution of the crystal population was analyzed for growth-dominated seeded cooling crystallization. The macro-mixing behavior was characterized by residence time distribution measurements for the fluid phase and the crystals. At the crystallizer outlet, a flow-through microscope was used to analyze the crystal size and shape distribution, where the 3D shape of individual crystals was estimated from 2D projections. The experiments showed a separation of the particle population according to the crystal size. This process allows the controlled shaping of crystals under continuous operating conditions. The shape of a crystal strongly affects its properties. A helically coiled tube crystallizer was investigated for shape-selective crystal growth, using a flow-through microscope to analyze the crystal size and shape distribution for potash alum. Residence time distribution measurements showed separation according to particle size. Larger crystals were found to travel faster than small crystals.



Multiscale Simulation with a Two-Way Coupled Lattice Boltzmann Method and Discrete Element Method

2017-08-10T05:11:29.655006-05:00

Simulations are helpful to better understand the dynamics and interactions of large numbers of particles and fluid in processes that occur in chemical or process engineering. Depending on whether the suspension is dense, dilute or semi-dilute, the particles and fluid can be mutually affected. Here, a lattice Boltzmann method for the fluid is combined with a discrete element method for the particles which were treated as point particles. Both are two-way coupled by drag forces, based on momentum exchange. Single-particle sedimentation is chosen as a first validation example for one- and two-way coupling. For dense suspensions, contact forces are necessary and a scenario for two colliding particles is verified before the simulation of a multiparticle block is performed. Simulations are a valuable tool to better understand how particles behave in fluids in chemical and process engineering. Particle concentration can differ widely within the simulation domain. A lattice Boltzmann method is two-way coupled with a discrete element method for the particles treated as point particles. Two-way coupling is validated in the case of single-particle sedimentation.



Virtual Characterization of Dense Granular Flow through a Vertically Rotating Feeding Experiment

2017-07-28T04:00:51.646455-05:00

The applicability of continuum granular flow models relies on the characterization of the macroscopic constituting relations of such models. Recent works have presented relations especially for the granular viscosity in certain well-defined experiments. Here, a different, highly dynamic, yet dense granular flow experiment using a vertically rotating feeding device with an off-centered rotating bottom opening together with an inverse problem approach of model essential parameters is described. For validation purposes, glass beads are used, even though the method is developed for a broader scope of materials. The same workflow is applied to a continuum and a discrete element method (DEM) model and results with a relative error in a comparable range are obtained. Numerical simulations help to predict, analyze, and optimize the granular flow. An approach to determine material parameters in a continuum and a discrete element method model are presented. Via an inverse problem approach, a viscosity prefactor in the continuum model or friction parameters in the discrete element method model by comparing mass flow rates are established.



Catalytic Pyrolysis of Bituminous Coal under Pyrolysis Gas over a Ni/MgO Catalyst

2017-05-31T08:30:45.133639-05:00

To improve the yield and quality of coal pyrolysis tar while using pyrolysis gas (PG), a Ni/MgO catalyst was introduced to catalyze the pyrolysis of bituminous coal under a PG atmosphere. The effects of pyrolysis temperature, gas flow rate, catalyst packing methods, and atmosphere composition on coal pyrolysis were investigated. The yield and quality of tar obtained from Shihezi (SHZ) bituminous coal pyrolysis under N2, PG, and PG over a Ni/MgO catalyst were found to vary with the increase of pyrolysis temperature. The catalyst packed in the upper layer results in higher tar yields, but mixing the catalyst and coal leads to an increase in the maltene yield. The components in PG improved the tar yield and tar quality. Finally, a higher tar yield can be obtained from SHZ coal pyrolysis under CO/H2, CO2/H2, and CO2/CH4 atmospheres using a Ni/MgO catalyst. It is feasible to improve the yield and quality of tar by recycling pyrolysis gas (PG) over a Ni/MgO catalyst during coal pyrolysis. Catalytic pyrolysis of Shihezi bituminous coal was done with a differently packed Ni/MgO catalyst under PG. A higher tar yield was obtained when the catalyst was packed in the upper layer. All PG components were favorable for improving tar yield and quality.



Photodegradation of Polymer Materials Used for Film Coatings of Controlled-Release Fertilizers

2017-05-31T08:31:02.338675-05:00

The photodegradation of three polymer materials was studied, i.e., polyolefin, polyurethane, and a copolymer of styrene, butyl acrylate, and methyl methacrylate (P(St-co-BA-co-MMA) latex). These polymers are mostly used as film-coating materials for producing controlled-release fertilizers. The P(St-co-BA-co-MMA) latex film degraded at the highest rate and the film surface became porous under UV irradiation. The weak cross-link chain in the latex film was broken and the connections between the microspheres were destroyed. A photo-oxidative aging reaction weakened the tenacity of the latex film, which resulted in the easy release of microspheres from the film, leading to a reduction in film thickness and film tensile strength. Threfore, P(St-co-BA-co-MMA) latex is a promising coating material for controlled-release fertilizers. P(St-co-BA-co-MMA) latex is a promising coating material for producing controlled-release fertilizers. Under ultraviolet irradiation, the latex film noticeably degraded and the surface became porous. After irradiation, the microspheres were easily released from the film, leading to loss of film mass, decrease in film thickness, and reduction in film tensile strength.



Chemically Treated Rice Husk Blends as Green Desiccant Materials for Industrial Application

2017-06-20T02:27:18.168819-05:00

The use of rice husks (RHs), treated RHs, and blends thereof as desiccants was studied. Bare RHs, treated RHs, and blends were characterized, and their water absorbances compared. Acid-treated RHs showed better moisture absorbance than alkali-treated RHs and hence were used to prepare blends. Moisture absorption of RH materials and silica gel were compared. Blends with a higher content of acid-treated RHs showed higher water and moisture absorbency. The moisture absorbency of the blends was enhanced, and they exceeded the silica-gel limit at 48 h of exposure time. The higher absorbency in blends with higher contents of acid-treated RHs is likely due to higher porosity and improved adhesion properties owing to surface OH groups. Moreover, RH blends require shorter regeneration times than silica gel. Desiccants mitigate undesirable side effects of moisture, such as corrosion, swelling, rust, and mold. Blends of raw and chemically treated rice husks (RHs) were investigated as green desiccants for industrial applications. Blends with higher contents of acid-treated RHs showed higher water and moisture absorbance, and they exceeded the silica-gel limit after 48 h of exposure time.



Comparison of the Performances of Different Reduced Forms of a Condenser Model

2017-06-20T04:48:46.013802-05:00

Symbolic manipulation uncovers hidden constraints for a model and facilitates model reduction for solution. The present work points out possible pitfalls of this procedure and finds possible solutions. The performances of different reduced forms of a condenser model are compared under step and impulse perturbations. The system does not need to be at steady state before perturbation. Some symbolically manipulated models cause inconsistent reinitialization and convergence and introduce significant computational errors. Physically unreasonable system behavior thus emerges, which worsens with increasing model complexity. Nevertheless, the less symbolically manipulated models present realistic and accurate behaviors. Another approach to model reduction is the reformulation of a model through a physical insight. A physically reformulated model proposed for the system leads to accurate and physically reasonable system behavior. To facilitate solution, different reduced forms of a condenser model are obtained by symbolic manipulations and physical reformulation. Their performances are compared for realistic initialization, evolution, and convergence under step and impulse perturbations. The performance worsens with increasing model complexity, but the less symbolically manipulated and physically reformulated models show accurate behaviors.



Improved Methodology for Absorption Measurements in Ionic Liquids with a Quartz Crystal Microbalance

2017-06-20T05:19:00.167543-05:00

The knowledge of vapor-liquid equilibrium data of mixtures with performance chemicals, such as ionic liquids (ILs), is highly important for technical applications. New insights into the utilization of quartz crystal microbalances (QCMs) for reliable absorption measurements in ILs are provided. The validity of the Sauerbrey equation for rigid films and bulk liquids is widely discussed in literature. This work shows how to ensure the validity of the Sauerbrey equation during absorption measurements in thin liquid films. Furthermore, the advantages of the employment of rough electrodes for absorption measurements within thin liquid films in comparison to polished ones are described in detail. Important recommendations in application of the QCM systems regarding gravimetric measurements are presented. The quartz crystal microbalance has gained increasing scientific interest, allowing precise detection of mass change per unit area in the range of a few nanograms per square centimeter. Reliable absorption measurements in ionic liquids were performed. Influencing factors and the resulting measures are discussed to ensure an accurate determination of the activity coefficient of gases.



Potential of On-Board Gasoline Upgrading for Enhancement of Engine Efficiency

2017-06-28T01:51:01.728849-05:00

Apart from the introduction of renewable fuels, improved engine efficiency is a useful strategy for the reduction of CO2 emission from vehicles. Therefore, this work deals with the catalytic on-board upgrading of commercial gasoline to enhance the content of aromatics, leading to improved knocking behavior to allow higher compression in the engine. Resulting from theoretical considerations and thermodynamic calculations, model mixtures with a higher aromatic content were prepared and analyzed towards their octane number. Engine tests with these mixtures show an enhancement of engine efficiency. Laboratory-scale catalytic reforming experiments demonstrated a relative increase of the aromatic content in the treated gasoline. The gaseous cracking products have good knocking behavior and could be routed to the engine as additional fuel. On-board upgrading of commercial gasoline is an interesting way to enhance motor efficiency and opens up possibilities to decouple the gasoline composition, which affects the operation of spark-ignition engines, from limits such as the content of aromatics given by fuel standards. Reforming experiments and engine tests are described to show improved engine efficiency by modified gasolines.



Mathematical Modeling and Simulation of Propylene Absorption Using Membrane Contactors

2017-06-23T04:05:50.001775-05:00

Separation of light olefin-paraffin mixtures having the same carbon number is one of the most energy-intensive separation processes in petrochemical industry. Gas-liquid membrane contactors as an alternative to conventional processes have gained increasing interest due to low energy consumption. A 2D comprehensive model was developed to predict the transport and chemical absorption of propylene in a cocurrent microporous membrane contactor. Formations of a complex between propylene and silver ion and dissolution of silver nitrate were considered. With increasing gas flow rate the system efficiency decreases due to the reduction of propylene residence time inside the contactor. As the absorbent amount increases in the tube, both propylene and complex penetrate more deeply into the liquid and a diffusion layer is formed near the gas-liquid interface. Gas-liquid membrane contactors are an energy-saving alternative to conventional processes for separation of light olefin-paraffin mixtures having the same carbon number. Such separation process using membrane technology is simulated by means of a computational fluid dynamics approach. Modeling and simulation can reduce the expense of process optimization at industrial scale.



Radio Frequency-Based In Situ Determination of the Mass Loss of Supported Ionic Liquids

2017-06-07T04:15:21.883078-05:00

For technical applications of supported ionic liquids (ILs), the stability of the IL layers both with regard to thermal decomposition and to losses by evaporation is of great importance. An innovative radio frequency-based method is presented to determine the pore filling degree of supported ILs in situ and in a contactless way. As an example, the IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, which was supported on the internal surface of porous silica, was selected. The complex permittivity of the porous solid coated with the IL increases linearly with the IL pore filling degree. Therefore, the evaporation rate of the IL in a fixed bed could be measured in situ in the reactor. The stability of supported ionic liquids is important for technical applications regarding thermal decomposition and losses by evaporation. To overcome the disadvantages of state-of-the-art thermogravimetric analyses, an innovative radio frequency-based method to measure the pore filling degree as well as the evaporation rate of supported ionic liquids contactless and in situ is proposed.



Performance Improvement of a Sequencing Batch Reactor for Treating Tannery Wastewaters

2017-06-28T01:25:48.79486-05:00

Tannery wastewater has a high environmental impact due to its low biodegradability. Sequencing batch reactors (SBRs) are an established method for treating highly polluted wastewater. To minimize the hydraulic retention time (HRT) of the SBRs, various HRT values were tested and the best value was chosen according to the removal efficiency of the soluble chemical oxygen demand (COD). A series of experiments was then carried out with two cationic polyelectrolytes added to the system in two different modes to improve the effluent quality. Both modes were evaluated in terms of the soluble COD, suspended solid concentration, and turbidity of the final effluent. The results showed that reducing the HRT to two days did not diminish the COD removal efficiencies. Tannery wastewaters with high concentrations of organic matter, high salinity, and low biodegradability can have a significant environmental impact. The use of sequencing batch reactors to treat tannery wastewaters was investigated with the goal of minimizing the hydraulic retention time. Moreover, the addition of two cationic polyelectrolytes to improve effluent quality was studied.



Meta-Model-Based Calibration and Sensitivity Studies of Computational Fluid Dynamics Simulation of Jet Pumps

2017-07-17T08:20:56.360055-05:00

Calibration and sensitivity studies in the computational fluid dynamics (CFD) simulation of process equipment such as the annular jet pump are suitable for design, analysis, and optimization. The application of CFD for such purposes is computationally intensive. Hence, an alternative approach with kriging-based meta-models was utilized. Calibration via the adjustment of two turbulent model parameters, Cμ and C2ε , and likewise two parameters in the simulation correlation for Cμ was considered, while sensitivity studies were based on Cμ as input. The meta-model-based calibration aids exploration of different parameter combinations. Computational time was also reduced with kriging-assisted sensitivity studies which investigated the effect of different Cμ values on pressure distribution. Meta-models are approximate empirical models enabling fast analysis and optimization. Such meta-models were applied for enhanced exploration of turbulent model parameters in computational fluid dynamics studies of annular jet pumps. The results obtained could be highly valuable for future simulations being pivotal to optimization and input-output investigations.



Low-Temperature CO Methanation in Oil-Tempered Plate Reactors by Optimization of Catalyst Activation Conditions

2017-07-06T05:37:26.914639-05:00

Ni-catalyzed methanation has been discovered more than 100 years ago. Since then, many applications based on syngas – from coal or biomass – for the production of synthetic natural gas (SNG) have been established. Nevertheless, methanation still bears great potential for optimization. Especially for decentralized, biomass-based applications, decreased methanation temperatures and pressures are expected to lower the costs of the overall process. Consequently, it is necessary to obtain a catalyst that is highly active under such reduced reaction conditions. This objective was successfully reached by a systematic variation of reduction temperature, pressure, and hydrogen concentration under the aspects of the design of experiment within the catalyst activation process. The activation procedure of a commercial Ni/Al2O3 catalyst was optimized by a systematic variation of reduction temperature, pressure, and H2 concentration. Thereby, the objective to obtain a catalyst that is as active and selective as possible under mild methanation conditions was successfully reached. An innovative oil-tempered plate reactor was used for the experiments.



Preparation of High-Performance Membranes Derived from Poly(4-methyl-1-pentene)/Zinc Oxide Particles

2017-08-02T03:05:32.167847-05:00

The efficiency of gas separation by mixed-matrix membranes (MMMs) derived from poly(4-methyl-1-pentene) (PMP) filled by zinc oxide nanoparticles is investigated. The membranes are prepared by the solvent evaporation method. The zinc oxide nanoparticles are loaded at different weight percentages. The results reveal that adding zinc oxide nanoparticles at all loading percentages of the nanoparticles increases the selectivity of all gas pairs such as O2/N2, CO2/CH4, and CO2/N2. Furthermore, the CO2 permeability in PMP-zinc oxide MMMs was significantly improved when increasing the feed pressure. The addition of nanoparticles to polymeric precursors and the preparation of mixed-matric membranes are considered as suitable alternative to improve mechanical properties, transferability, and selectivity in commercial polymer membranes. The efficiency of gas separation by mixed-matrix membranes developed from poly(4-methyl-1-pentene) filled with zinc oxide nanoparticles is investigated.



Hydrogen Production from Bioethanol: Behavior of a Carbon Oxide Preferential Oxidation Catalyst

2017-07-06T05:37:23.501225-05:00

Hydrogen is recognized as a promising green energy source, particularly when used to feed a polymer electrolyte membrane fuel cell (PEMFC). Here, hydrogen was obtained by bioethanol steam reforming with CO and CO2 as primary sub products. Since the cell anode is extremely sensitive to poisoning with CO, water-gas shift (WGS) and carbon oxide preferential oxidation (COPROX) reactors were employed for hydrogen purification. Catalysts prepared by our lab were tested at pilot plant scale in both the reformer and COPROX unit, where different active phase distributions, stoichiometric excess of air, and reaction temperatures were tested. The use of two different COPROX units with intermediate air injection was also considered. The as-prepared catalysts showed good stability and performance. Hydrogen is a promising alternative energy source also used to feed polymer electrolyte membrane fuel cells. It was obtained by bioethanol steam reforming with CO and CO2 as primary sub products. An automated pilot plant for hydrogen production from bioethanol steam reforming was built and successfully operated which also may be suitable to test other catalysts and raw materials.



Biodiesel Production from Waste Frying Oil by Ultrasound-Assisted Transesterification

2017-07-12T08:55:18.889405-05:00

The production of biodiesel as renewable, easily biodegradable, and nontoxic alternative to fossil fuels is expensive when it is derived from virgin vegetable oils. In this study, waste frying oil was used to produce biodiesel by ultrasound-assisted transesterification. The reaction was carried out with methanol, and sodium hydroxide was used as catalyst. This method is an efficient, timesaving, and economically functional tool since the process can be carried out in a shorter reaction time, at lower temperature, and with a lower quantity of catalysts compared to other techniques. The biodiesel produced by this method was analyzed for its fatty acid methyl ester composition, density, moisture and volatile matter content, acid value, saponification value, iodine value, distillation curves, and cetane number. Since conventional syntheses of biodiesel are cost-intensive and time-consuming, ultrasound was applied in this study to improve the efficiency of the transesterification of waste frying oil into biodiesel. This process proved to be a suitable tool in biodiesel production since it is carried out in shorter time, at lower temperatures, and with lower catalyst quantity compared to other methods.



Characterization of Powder Layer Dustiness – Influence of the Deposit Thickness

2017-07-12T06:40:47.585706-05:00

The release of dust during powder processing is generally an undesired process and product property that needs to be controlled. Dustiness has so far been neglected to be appropriately addressed as a product property in application technology. To measure the redispersion of dust from a particle layer deposited on a surface, the redispersion dust in a double-pipe system (RDDS) device may be used that has been developed for controllable redispersion of deposited dust from surfaces. Different particulate deposits, varying the deposit morphology and thickness, have been generated here by means of an electrostatic precipitator. For different particulate test materials a significant influence of the powder layer formation on the powder redispersion and dustiness has been found. The dustiness of particulate layers and deposits is an important process-related product property within dispersed solids handling and processes. Investigations of the combination of the deposit thickness and the release of particles in the redispersion dust in a double-pipe system (RDDS) demonstrated a proper possibility to characterize the dustiness of powders.



Modeling and Optimization of Membrane Bioreactors and Moving Bed Biofilm Reactor-Membrane Bioreactors

2017-07-26T07:45:22.211995-05:00

A membrane bioreactor (MBR) and two hybrid moving bed biofilm reactor-membrane bioreactor systems (hybrid MBBR-MBRs) were studied in terms of the process modeling and operation optimization through different mathematical models for organic matter and nitrogen removal. A multiple linear regression method and a multivariable statistical analysis were applied. The process variables were hydraulic retention time, total biomass concentration, temperature, chemical oxygen demand of the influent, and total nitrogen of the influent. In general, the values of the coefficient of determination (R2) for the different model fittings were higher for the hybrid MBBR-MBR processes than those obtained for the MBR, which was probably attributable to the presence of suspended and attached biomass in the hybrid MBBR-MBR systems. Membrane bioreactors are becoming excellent alternatives for wastewater treatment, but further research into process modeling and optimization is needed. Here, mathematical models are described for organic matter and nitrogen removal and kinetic performance to allow optimization of a range of operational conditions for these systems.



Overview Contents: Chemie Ingenieur Technik 9/2017

2017-08-24T13:02:51.775058-05:00