Showing papers in "Chemical Engineering & Technology in 2011"
TL;DR: The structure of lignin suggests that it can be a valuable source of chemicals, particularly phenolics as discussed by the authors, but it is the major challenge for converting it into value-added chemicals.
Abstract: The structure of lignin suggests that it can be a valuable source of chemicals, particularly phenolics. However, lignin depolymerization with selective bond cleavage is the major challenge for converting it into value-added chemicals. Pyrolysis (thermolysis), gasification, hydrogenolysis, chemical oxidation, and hydrolysis under supercritical conditions are the major thermochemical methods studied with regard to lignin depolymerization. Pyrolytic oil and syngases are the primary products obtained from pyrolysis and gasification. A significant amount of char is also produced during pyrolysis. Thermal treatment in a hydrogen environment seems very promising for converting lignin to liquid fuel and chemicals like phenols, while oxidation can produce phenolic aldehydes. Reaction severity, solvents, and catalysts are the factors of prime importance that control yield and composition of the product.
1,185 citations
TL;DR: In this article, the authors reviewed equipment design parameters and energy requirements in relation to initial and final particle sizes, bulk density, and moisture content in biomass, and provided an overview of equipment parameters and requirements.
Abstract: Biofuel technology seems to be a promising method for economically and environmentally prospective treatments of lignocellulosic wastes from various branches like food processing, forestry, or agriculture. Factors like the lignin content, crystallinity of cellulose, and particle size, limit the digestibility of hemicellulose and cellulose present in lignocelluloses. Biomass size reduction is a mechanical treatment process which due to increasing of the accessible surface area and decreasing of cellulose crystallinity improves the digestibility and the conversion of saccharides during hydrolysis. Informations about equipment design parameters and energy requirements are reviewed in relation to initial and final particle sizes, bulk density, and moisture content in biomass.
229 citations
TL;DR: In this paper, a methodology for the synthesis of gold nanoparticles with controlled size and shape and exceptional colloidal stability is presented, which requires no external energy input and employs commercially available polymers, e.g., poly(ethylene oxide) containing Pluronics or Poloxamers.
Abstract: Gold nanoparticles exhibit novel optical and catalytic properties, are nontoxic and biocompatible, and attract considerable interest in a range of applications, e.g. photonics, diagnostics, and therapeutics. The morphology (size and shape) of the nanoparticles and their surface/colloidal properties are very important in the various applications. A methodology for the synthesis in aqueous media of gold nanoparticles with controlled size and shape and exceptional colloidal stability is reviewed. This methodology is based on designer polymers that can exhibit multiple functions on the basis of the polymer intramolecular and supramolecular organization. In addition to being water based, this methodology requires no external energy input and employs commercially available polymers, e.g., poly(ethylene oxide) containing Pluronics or Poloxamers, resulting in low cost and potential environmental benefits.
206 citations
TL;DR: In this paper, the influence of an ingredient, here lignin, on carbonization was studied, with the focus being not only on the composition but also on the structure of the product formed.
Abstract: Hydrothermal carbonization is an attractive process for converting biomass with high water content into different products. The requirements on the products, which may be soil improvement or substitution of lignite or carbon black, are opposed to biomass as a feedstock that has a very complex and variable composition. The goal of this work was to study the influence of an ingredient, here lignin, on carbonization, with the focus being not only on the composition but also on the structure of the product formed.
121 citations
TL;DR: In this paper, an optimization study was performed for a Lurgi methanol synthesis reactor using the commercial process simulator Aspen Plus, coupled with a steady-state model of the methanoline synthesis reactor.
Abstract: Methanol is an important chemical with the potential to become an alternative fuel. An optimization study was performed for a Lurgi methanol synthesis reactor using the commercial process simulator Aspen Plus. The optimization routine is coupled with a steady-state model of the methanol synthesis reactor. Syngas inlet temperature, steam drum pressure, and cooling water volumetric flow rate were optimized so that methanol production in the reactor outlet was maximized. The methanol yield increased by 7.04 %.
93 citations
TL;DR: An overview of technologies for fossil fuel-fired power plants with drastically reduced CO2 emissions is given in this paper, where post-combustion capture using reactive absorption is discussed in some detail.
Abstract: An overview of technologies for fossil fuel-fired power plants with drastically reduced CO2 emissions is given. Post-combustion capture, pre-combustion capture, and oxyfuel technology are introduced and compared. Current research results indicate that post-combustion capture may lead to slightly higher losses in power plant efficiency than the two other technologies. However, retrofitting of existing plants with oxyfuel technology is complex and costly, and retrofitting of pre-combustion capture is not possible. On the other hand, post-combustion capture can be retrofitted to existing power plants with only minimal effort. Based on the mature technology of reactive absorption, it can be implemented on a large scale in the near future. Therefore, post-combustion capture using reactive absorption is discussed here in some detail.
93 citations
79 citations
TL;DR: In this article, the economics of a modular chemical plant are compared with those of a traditional large-scale plant by investigating the net present value, and the authors present a more efficient concept for fast growing products or products with volatile demands.
Abstract: Modular plants consist of modules that autonomously operate parts of the plant. These modules are technically and organizationally limited areas of the plant that fulfill defined tasks. Starting with these modules, companies can create capacity either by equaling up modules from general structures or by numbering up equipment. Here, the economics of a modular chemical plant are compared with those of a traditional large-scale plant by investigating the net present value. The modular plant presents a more efficient concept for fast growing products or products with volatile demands. This is because the market impact during operation is more important than the preceding influence of the investment. In those cases, the effects of flexibility surpass the effects of scale.
76 citations
TL;DR: The liquid-liquid slug flow capillary microreactor offers an excellent mass transfer performance for extraction and biphasic reactions, in combination with a simple phase separator based on wettability discrimination between the two liquids, it provides a powerful tool for process intensification and microscale processing as mentioned in this paper.
Abstract: The liquid-liquid slug flow capillary microreactor offers an excellent mass transfer performance for extraction and biphasic reactions. In combination with a simple phase separator based on wettability discrimination between the two liquids, it provides a powerful tool for process intensification and microscale processing. By new visualization techniques, the interfacial surface and slug vortex structures dictating inter- and intraphase mass transfer have been revealed to be more complex than previously assumed. Suspending fine catalyst particles in one phase of a two-phase slug flow is an effective technique for using heterogeneous catalysts in microreactors, owing to the very good mass transfer characteristics and because catalyst recovery becomes simply a matter of separating the catalyst carrier phase from the reaction medium. To exploit the performance attributes of capillary microreactors at higher throughputs, distributor and control strategies for parallelisation were developed to provide a flow distribution uniform to within 1 % or less.
76 citations
TL;DR: In this paper, a series of insoluble heteropolytungstate salts, CsxH3−xPW12O40 (x = 1-3), were prepared and applied to the selective hydrolysis of microcrystalline cellulose to sugars in the aqueous phase.
Abstract: A series of insoluble heteropolytungstate salts, CsxH3–xPW12O40 (x = 1–3), were prepared and applied to the selective hydrolysis of microcrystalline cellulose to sugars in the aqueous phase. CsxH3–xPW12O40 were active toward the hydrolysis of cellulose into total reducing sugars (TRS) and glucose, which are the important products for the application for biofuels. The conversion of cellulose and total yield for the main products increased with increasing acidity of the catalyst. Cs1H2PW12O40 exhibited the best catalytic activity in terms of the conversion of cellulose and yields for TRS and glucose, while Cs2.2H0.8PW12O40 showed the highest selectivity for TRS and glucose.
59 citations
TL;DR: Pore network modeling is now a well-established and successful technique for understanding and predicting a wide range of drying features as mentioned in this paper, with special focus on the effect of liquid films and wettability.
Abstract: Pore network modeling is now a well-established and successful technique for understanding and predicting a wide range of drying features. This paper presents an overview of recent works with special focus on the effect of liquid films and wettability. The capability of pore network models is also illustrated through a discussion of the classical drying curve of capillary porous media, which is divided into three main periods. Some open problems and future prospects are discussed.
TL;DR: In this article, an electrospray crystallization method was proposed for creating high-quality submicron-sized crystals of the energetic material cyclotrimethylene trinitramine (RDX).
Abstract: Nano- and submicron-sized crystals are too small to contain inclusions and are, therefore, expected to have a higher internal quality compared to conventionally sized particles (several tens to hundreds of microns). Using electrospray crystallization, nano- and submicron-sized crystals can be easily produced. With the aid of electrospray crystallization, a mist of ultrafine solution droplets is generated and subsequent solvent evaporation leads to crystallization of submicron-sized crystals. Using cyclotrimethylene trinitramine (RDX) solutions in acetone, the conditions for a stable and continuous jet were established. At relatively small nozzle diameters and relatively low potential differences, hollow spheres of RDX crystals were observed. At a higher nozzle diameter and potential difference and in the region of a continuous jet, RDX crystals with an average size of around 400nm could be produced. In order to test the quality of the submicron-sized energetic material, impact and friction sensitivity tests were carried out. The test results indicate that the submicron-sized product had reduced friction sensitivity, indicating a higher internal quality of the crystalline product. Electrospray crystallization is proposed as a method for creating high-quality submicron-sized crystals of the energetic material cyclotrimethylene trinitramine (RDX). The friction sensitivity of the obtained unagglomerated submicron-sized crystals was lower than that of conventional RDX, indicating that they have a better internal quality. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
TL;DR: In this article, a pilot polygeneration process of a 75th -1 circulating fluidized bed (CFB) boiler combined with a moving bed coal pyrolyzer was developed based on laboratory-scale experimental results.
Abstract: A pilot polygeneration process of a 75th –1 circulating fluidized bed (CFB) boiler combined with a moving bed coal pyrolyzer was developed based on laboratoryscale experimental results. The process operation showed good consistency and integration between boiler and pyrolyzer. Some critical operating parameters such as hot ash split flow from the CFB boiler to the pyrolyzer, mixing of hot ash and coal particles, control of pyrolysis temperature and solid inventory in the pyrolyzer, and pyrolysis gas clean-up were investigated. Yields of 6.0wt-% tar and 8.0wt-% gas with a heating value of about 26MJm –3 at 600 °C were obtained. Particulate content in tar was restrained less than 4.0wt-% by using a granular filter of the moving bed. Operation results showed that this pilot polygeneration process was successfully scaled up.
TL;DR: In this paper, ETP and ETS esters were synthesized as novel solid-liquid phase change materials (PCM) by means of the direct esterification reaction of the erythritol with palmitic and stearic acids.
Abstract: Erythritol tetrapalmitate (ETP) and erythritol tetrastearate (ETS) were synthesized as novel solid-liquid phase change materials (PCM) by means of the direct esterification reaction of the erythritol with palmitic and stearic acids. The ETP and ETS esters were characterized chemically using FT-IR and 1H NMR techniques. The energy storage properties of the esters were determined by DSC analysis. The results indicated that the ETP and ETS esters synthesized as novel solid-liquid PCMs are promising materials for thermal energy storage applications at large scale such as solar energy storage, building heating or cooling, indoor temperature controlling, and production of smart textile and insulation clothing.
TL;DR: In this article, the authors developed and analyzed a method for the design of model predictive controllers for dividing wall columns, which can offer enormous energy savings compared to common distillation columns and configurations.
Abstract: The technology of dividing wall columns can offer enormous energy savings compared to common distillation columns and configurations. The technology of model predictive control is also advantageous since such a controller minimizes the future deviation of the predicted controlled variable from the reference point. The practical application of model predictive controllers for dividing wall columns is still limited due to limited experience with high interactions among the process variables. The scope of this work is the development and analysis of a method for the design of model predictive controllers for dividing wall columns. An experimental investigation verifies the practicability of the applied approach. The methods generated are transferable to other applications. Thus, the industrial acceptance of model predictive controllers for dividing wall columns is enhanced.
TL;DR: In this paper, the effect of microchannel geometry on high-pressure dispersion and emulsification was investigated and it was demonstrated that high pressure losses focused at a small channel length and high velocity gradients lead to high stress intensities and, in consequence, to low particle or droplet sizes.
Abstract: Experimental investigations of the effect of microchannel geometry on high-pressure dispersion and emulsification were carried out. Customized microchannels of varying geometric principles were fabricated in silicon and steel. In order to characterize the process efficiency of microchannel geometries, the effects of the process parameters (mean velocity, Reynolds number, and local pressure drop) were examined and correlated to the dispersion and emulsification results. It is demonstrated that high pressure losses focused at a small channel length and high velocity gradients lead to high stress intensities and, in consequence, to low particle or droplet sizes. Thus, 2D orifices were successfully further improved regarding their process efficiency by adding a third-dimension constriction.
TL;DR: In this paper, a microwave-cavity perturbation method is proposed in which electromagnetic waves are excited by probe feeds and the reflected signals are measured at distinct resonance frequencies, the reflection coefficient shows a pronounced minimum These resonance frequencies depend almost linearly on the NH 3 loading of a zeolite-based SCR catalyst.
Abstract: Exhaust gas aftertreatment systems, which reduce nitrogen oxide emissions of heavy-duty diesel engines, commonly use a selective catalytic reduction (SCR) catalyst Currently, emissions are controlled by evaluating NO x or NH 3 in the gas phase downstream the catalyst and calculating the NH 3 loading via a chemical storage model Here, a microwave-cavity perturbation method is proposed in which electromagnetic waves are excited by probe feeds and the reflected signals are measured At distinct resonance frequencies, the reflection coefficient shows a pronounced minimum These resonance frequencies depend almost linearly on the NH 3 loading of a zeolite-based SCR catalyst Since the NH 3 loading-dependent electrical properties of the catalyst material itself are measured, the amount of stored ammonia can be determined directly and in situ The cross-sensitivity towards water can be reduced almost completely by selecting an appropriate frequency range
TL;DR: In this article, the aggregation of crystals within a flow tube was observed based on data extracted from images of the bypassing population, and the analysis of images of bypassing crystals allows for the acquisition of rich datasets both in terms of the variety of shape descriptors and number of particles.
Abstract: The aggregation of crystals within a flow tube was observed based on data extracted from images of the bypassing population. The experiments were conducted under different conditions, namely the flow rate and the particle concentration have been varied simultaneously and two different solvents were used in which the aggregation extent was found to be different under otherwise constant conditions. The analysis of images of bypassing crystals allows for the acquisition of rich datasets both in terms of the variety of shape descriptors and number of particles. This amount of data enables the determination of at least bivariate number distributions of high accuracy with simple histograms. The interpretation of the data is further improved with kernel histograms with which also higher-dimensional volume distributions can be obtained in good quality based on relatively few data points. Indeed, the isosurfaces of 3D distributions turned out to be helpful for inspection of the acquired data.
TL;DR: In this paper, the main aim was to recover and purify high value-added organic compounds (organic acids) from lignin and inorganic compounds by combining membrane filtration, acid precipitation and cooling crystallization.
Abstract: Separation of organic and inorganic compounds from black liquor was investigated. Black liquor from the pulp and paper industry contains hundreds of different compounds and several high-value organic chemicals are formed during alkaline pulping. These organic compounds can be used in the fine chemicals, pharmaceutical and food industries. The main aim of this study was to recover and purify high value-added organic compounds (organic acids) from lignin and inorganic compounds by combining membrane filtration, acid precipitation and cooling crystallization. The effect of membrane filtration on the efficiency of precipitation and crystallization was also studied. A number of separation methods were studied under a variety of operating conditions. The results showed that a combination of membrane separation and crystallization is an efficient method for recovering and purifying valuable organic compounds in black liquor. The amount of major impurities in black liquor could be reduced significantly.
TL;DR: In this paper, the effects of swirls on the mass flow rates and on the natural gas velocity and temperature in a supersonic separator were numerically studied using the Reynolds stress model.
Abstract: The effects of swirls on the mass flow rates and on the natural gas velocity and temperature in a supersonic separator were numerically studied using the Reynolds stress model. An experimental system was set up with moist air as working fluid. The results showed that high swirl strengths decreased the mass flow rates through the supersonic separator. An increase in swirl strength resulted in a reduction and non-uniform radial distribution of the gas Mach number at the nozzle exit. With moderate swirls, low temperature (–60 °C) and a strong centrifugal field (5 · 106 m s–2) are obtained to condense and separate water and heavy hydrocarbons from natural gas. The experimental results agreed with the simulations demonstrating that strong swirls decreased the mass flow rate.
TL;DR: In this article, the authors developed a platform for high-throughput experimentation on spray drying, in which individual droplets are dispensed and dried on a flat surface, and a dispensing process is used that is able to dispense viscous liquids and generate small droplets (dp?>?150?µm).
Abstract: The basis for the development of a platform for high-throughput experimentation on spray drying is formed. To mimic the drying of single droplets during spray drying, individual droplets are dispensed and dried on a flat surface. A dispensing process is used that is able to dispense viscous liquids and generates small droplets (dp?>?150?µm). The dispensed droplet size for varying liquids could be accurately described with a predictive model based on Bernoulli's law. The drying of droplets is monitored with a camera and modeled with mass balance equations. Finally, a Sherwood correlation is derived to describe the mass transfer between the sessile droplet and the drying air.
TL;DR: In this paper, a coupled discrete element method-computational fluid dynamics (DEM-CFD) simulations have been performed to study the fluid and particle dynamics in a fluidized-bed granulator on the scale of individual particles.
Abstract: Coupled discrete element method-computational fluid dynamics (DEM-CFD) simulations have been performed to study the fluid and particle dynamics in a fluidized-bed granulator on the scale of individual particles. Simulation of the gas and particle dynamics is combined with heat and mass transfer mechanisms, as the moisture distribution is a key parameter for the functionality of a fluidized-bed spray granulator. The model allows monitoring the moisture content and temperature of each individual particle as well as the temperature and humidity of the surrounding gas phase. A novel modeling approach is presented to describe the process dynamics of a fluidized bed in full detail for a reference time interval using coupled DEM-CFD simulations. The motion profile of gas and particles is extrapolated to larger time scales and used for the calculation of heat and mass transfer. Through this multiscale approach, a step forward is taken towards a physically based description of the microprocesses in granulation.
TL;DR: In this paper, the feasibility and efficiency of wet-nanogrinding of three drug substances (miconazole, itraconazoles, etravirine) with similar elastic and plastic properties proved primarily on the adequate electrostatic and steric stabilization of the nanoparticles and the specific energy input.
Abstract: The feasibility and efficiency of wet-nanogrinding of three drug substances (miconazole, itraconazole, etravirine) with similar elastic and plastic properties proved to depend primarily on the adequate electrostatic and steric stabilization of the nanoparticles and the specific energy input. Particle stabilization was provided by sodium dodecyl sulfate (SDS) and hydroxypropylcellulose. The specific energy input was defined by the grinding time, grinding bead size, and stirrer tip speed. Miconazole and itraconazole exhibited similar milling behavior, whereas etravirine nanosuspensions revealed agglomerates and increasing viscosity with increasing specific energy input. Agglomeration and viscosity increase were successfully counteracted by increasing the SDS concentration in the nanosuspension from 0 to 0.125 %. Under the provision of proper particle stabilization, the three drug substances could be nanosized to a mean size of ∼ 130 nm, with 90 % of all particles being smaller than ∼ 250 nm.
TL;DR: In this article, the residence time distribution (RTD) characteristics of three microreactors containing different passive mixing structures, namely, a three dimensional serpentine structure, a split-and-recombine structure and a staggered herringbone structure, were investigated and compared.
Abstract: The residence time distribution (RTD) characteristics of three microreactors containing different passive mixing structures, namely, a three dimensional serpentine structure, a split-and-recombine structure and a staggered herringbone structure, were investigated and compared. An experimental input-response technique was applied which required deconvolution of the measured data by modeling of the RTD. The proposed technique provides useful information on optimized application and operation of microfluidic devices. The serpentine reactor and the split-and-recombine reactor show improvement in RTD behaviour, i.e., narrowing of RTD curves, at Re-numbers > 30 due to effective transversal mixing and therefore reduced axial dispersion. In the case of the staggered herringbone structure, dead volumes could be observed which considerably affect the RTD.
TL;DR: In this article, the most important features of sprays emerging from different atomizers are discussed, and a well-mixed jet with little segregation of fine and large particles occurs, while a much stronger interaction of gas and spray takes place in the case of large spray angles as, e.g., produced by rotary atomizers.
Abstract: The spraying system is responsible for the particle formation and spray pattern. The most important features of sprays emerging from different atomizers are discussed. In the case of pneumatic atomizers the entrainment is low and a well-mixed jet with little segregation of fine and large particles occurs. A much stronger interaction of gas and spray takes place in the case of large spray angles as, e.g., produced by rotary atomizers. To some extent the particle morphology is known to depend on the drying speed and thus on the entrainment.
TL;DR: In this paper, the effects of preparation-influencing parameters such as polymer concentration, thickness of casting solution, and type of solvent on morphology and performance of poly(vinylidene difluoride) (PVDF) microfiltration membranes for the treatment of emulsified oily wastewater were investigated.
Abstract: The effects of preparation-influencing parameters such as polymer concentration, thickness of casting solution, and type of solvent on morphology and performance of poly(vinylidene difluoride) (PVDF) microfiltration membranes for the treatment of emulsified oily wastewater were investigated. Flat-sheet membranes were prepared from a casting solution of polymer and additive in various solvents by immersing the prepared films in nonsolvent-containing mixtures of water and 2-propanol. The membranes were characterized using scanning electron microscopy. Increasing the polymer concentration and membrane thickness significantly affected the pore size, leading to permeate flux decrease. An attempt was made to correlate the effect of the solvent on membrane morphology and performance employing solubility parameters between solvent and nonsolvent).
TL;DR: In this article, the authors deal with the induction period in crystallization fouling on heat transfer surfaces and identify the factors influencing the induction time, experiments with calcium sulfate were performed on modified surfaces, the free surface energy, roughness and topography were determined by drop shape analysis and/or AFM.
Abstract: This work deals with the induction period in crystallization fouling on heat transfer surfaces. While the crystal growth period can be calculated, the influencing effects in the initial stage of crystallization fouling are not fully understood and quantified so far. To identify the factors influencing the induction time, experiments with calcium sulfate were performed on modified surfaces. As surface parameters the free surface energy, roughness and topography were determined by drop shape analysis and/or AFM. The visual information by microscopic studies with a SEM shows different behavior in the initial stage of crystallization on modified surfaces at constant process conditions. These microscopic findings could be verified with induction times of fouling experiments, leading to a prediction of the induction time based on surface parameters and supersaturation of the salt solution.
TL;DR: In this paper, a segmented flow tubular reactor (SFTR) was used for ultrafine CaCO3, BaTiO3, and nanosized ZnO from optimized minibatch conditions.
Abstract: The successful scale-out and process intensification using a segmented flow tubular reactor (SFTR) for ultrafine CaCO3, BaTiO3, and nanosized ZnO from optimized minibatch (20 mL) conditions is presented. The capacity of the SFTR in process intensification was demonstrated by producing ∼ 5 kg batches of BaTiO3 powders with excellent batch-to-batch reproducibility. The SFTR scale-out or numbering-up capacity was demonstrated for a nanostructured CaCO3 in 500 g batches by scaling-out from one to six segmented flow tubular reactors run in parallel (scale-out/-up ratio of 5000 compared to lab batch experiments). The SFTR was then used to demonstrate its potential for nanosized ZnO powders producing 50 g lots of these nanopowders in a continuous process, a scale-out/-up ratio of 250 compared to lab batch experiments without any loss of powder quality. The SFTR allows a precise control of precipitation conditions, leading to an excellent reproducibility in powder characteristics, and shows great promise as a simple production process of powders and advanced nanomaterials with highly controlled properties.
TL;DR: In this paper, the optimal geometry of the thermoplate with respect to heat transfer of the inside fluid that passes through the channel as a single phase was obtained by applying a hydro-form technique.
Abstract: A thermoplate is a heat transfer device consisting of two metallic sheets that are spot-welded according to an appropriate pattern over the whole surface area whereas the edges – except for connecting tubes – are continuously seam-welded. By applying a hydro-form technique, a channel having a complex geometry is established between the sheets. Such heat transfer devices are encountered in several areas of cooling and heating techniques and process technology, e.g. as condensers or evaporators. The objective of the described investigations was to numerically obtain the optimal geometry of the thermoplate with respect to heat transfer of the inside fluid that passes through the channel as a single phase. The numerical experiments show that the heat transfer potential of the thermoplate having a staggered arrangement of welding spots is markedly higher than that of a common flat channel, particularly at larger Reynolds numbers. The variations of the geometrical parameters show the potential for the heat transfer improvement in comparison to a corresponding parallel plate channel.