Journal of The Chinese Institute of Chemical Engineers最新文献

A user-friendly simulator based on a comprehensive computer model for slurry bubble column reactors (SBCRs) for Fischer–Tropsch (F–T) synthesis, taking into account the hydrodynamics, kinetics, heat transfer, and mass transfer was developed. The hydrodynamic and mass transfer data obtained in our laboratories under typical F–T conditions along with those available in the literature were correlated using Back Propagation Neural Network and empirical correlations with high confidence levels. The data used covered wide ranges of reactor geometry, gas distributor, and operating conditions. All reactor partial differential equations, equation parameters and boundary conditions were simultaneously solved numerically.

The simulator was systematically used to predict the effects of reactor geometry (inside diameter and height) as well as superficial gas velocity and catalyst concentration on the performance of a large-scale SBCR provided with cooling pipes and operating under F–T conditions with cobalt-supported catalyst and H₂/CO = 2. The performance of the SBCR was expressed in terms of CO conversion, liquid hydrocarbon yield, catalyst productivity, and space time yield. The simulator was also used to optimize the reactor geometry and operating conditions in order to produce 10,000 barrels/day (bbl/day) of liquid hydrocarbons.

This paper details a unique, automated filtration apparatus and the newly developed Filter Design Software (FDS) which facilitates equipment selection, scale-up and simulation through an integrated experimental and theoretical approach.

By way of example, experimental data were obtained with the apparatus over constant, variable and stepped pressure regimes. Inherent suspension properties were maintained throughout by utilising a computer-controlled pressure regulator and cake formation was monitored by micro-pressure transducers capable of providing up to seven independent measures of liquid pressure within 3.3 mm of the filter medium surface. For constant pressure and moderately compressible talc cakes the liquid pressure increased with cake height in a non-linear manner and generally exhibited a concave profile. When a pressure step was applied following a period of constant pressure filtration, the cake structure typically required up to 30 s to reach a new pseudo-equilibrium state. During this time the reciprocal filtrate flow rate vs. filtrate volume plot was non-linear and the liquid pressures in the cake increased rapidly before remaining nearly constant. When the cake was thicker or the pressure step larger, the liquid pressure measured closer to the filter medium remained either constant following the increase in pressure or increased slowly over the 360 s duration of the pressure step which indicates potential difficulties with the stepped pressure test.

The filtration data were analysed using FDS to obtain scale-up coefficients and the impact of using incorrect scale-up coefficients on likely filter performance at the process scale is shown. The simulation capabilities of FDS are also highlighted through a case study in which, by way of example, the influence of crystal formation and other operating parameters on the filter cycle for a pharmaceutical product are shown. Simulations quantify how crystal form can detrimentally influence all phases of a cycle and lead to, for instance, slower filtration and wetter filter cakes.

Cone beam X-ray microtomography (XMT) instrumentation is a state-of-the-art non-invasive technology now used for several years to describe important characteristics of packed particle beds in three-dimensional (3D) detail. Many process engineering operations involve the transport of fluid in porous media. It is well known that the flow in porous media depends on the geometric properties of the pore network structure and in this regard X-ray microtomographic imaging captures the porous network structure of opaque packed particle beds which is later used for fluid flow analysis. The coupling of XMT 3D imaging with a novel fluid flow simulation method, known as the lattice-Boltzmann model (LBM), allows for direct local flow determination and micro-permeability calculations for complex porous structures. In this paper the methodology is briefly explained, implementations for some practical problems are addressed, the application of the technique from results for packed particle beds of interest are presented, and a comparison with experimental data is made.

The authors have successfully developed novel efficient and cost-effective sorbents for mercury removal from coal combustion flue gases. These sorbents were evaluated in a fixed-bed system with a typical PRB subbituminous/lignite simulated flue gas, and in an entrained-flow system with air simulating in-flight mercury capture by sorbent injection in the ductwork of coal-fired utility plants. In both systems, one of the novel sorbents showed promising results for Hg⁰ removal. In particular, this sorbent demonstrated slightly higher efficiencies in Hg⁰ removal than Darco Hg-LH (commercially available brominated activated carbon) at the similar injection rates in the entrained-flow system. The other novel sorbent showed excellent Hg⁰ oxidation capability, and may enable coal-fired power plants equipped with wet scrubbers to simultaneously control their mercury and sulfur oxides emissions. In addition, fixed-bed results for this sorbent showed that co-injection of a very small amount (∼10%) of raw activated carbon could eliminate almost all of the mercury generated by reactions of Hg⁰ with the sorbent.

A special method has been devised to measure yield stress of biosolids material or cake. A material with yield stress is placed in a container initially resting on its base. By slowly rotating the container 90° incrementally under “quasi-equilibrium”, the profile of the material is reformed in which the height is deeper on one end and shallower on the opposite end. To measure material with low yield stress, an immiscible lighter liquid is introduced with the material fully immersed in the pool of the lighter liquid and the above procedure is repeated. Also the dimension of the side of the container should be much greater that of the base. Despite the yield stress of the material is small the interface profile between the lighter liquid and the material can be established under reduced weight due to buoyancy force of the lighter liquid. The measured material profile is compared with the theoretical prediction based on a model assuming the material establishes a hydrostatic equilibrium in its final position with the container resting on its side. The effective density used in the test is the density difference between the lighter liquid and the material, which can be made small, catered for measuring material with very low yield stress.

The new method was used to measure xanthan gum with low yield stress with magnitude less than 1 Pa. The cross sectional shape of the container affects the measurement and the subsequent interpretation. Both rectangular and cylindrical geometries have been investigated and both give comparable yield stress for the xanthan gum being tested. The proposed method is attractive for providing reasonable and accurate measurement despite its simplicity.

Performing water gas shift (WGS) reaction efficiently is critical to hydrogen purification for fuel cells. In our earlier work, we proposed a CO₂-selective WGS membrane reactor, developed a one-dimensional non-isothermal model to simulate the simultaneous reaction and transport process and verified the model experimentally under an isothermal condition. Further modeling investigations were made on the effects of several important system parameters, including inlet feed temperature, inlet sweep temperature, feed-side pressure, feed inlet CO concentration, and catalyst activity, on membrane reactor performance. The synthesis gases from both autothermal reforming and steam reforming were used as the feed gas. As the inlet feed temperature increased, the required membrane area reduced because of the higher WGS reaction rate. Increasing the inlet sweep temperature decreased the required membrane area more significantly, even though the required membrane area increased slightly when the inlet sweep temperature exceeded about 160 °C. Higher feed-side pressure decreased the required membrane area as a result of the higher permeation driving force and reaction rate. A potentially more active catalyst could make the membrane reactor more compact because of the enhanced reaction rate. The modeling results have shown that a CO concentration of less than 10 ppm is achievable from syngases containing up to 10% CO.

This paper presents a computational approach for designing, mixed fiber filter media for depth filtration. The goal is to find an optimum solution, given the range, for a set of design parameters: thickness of the media, diameter of microfiber, and diameter of nanofiber, surface area ratio of nanofiber to microfiber and mass of microfiber. The objective of this work is to develop a software program that can be used as an aid to accelerate filter design and reduce the number of laboratory experiments.

This program applies a Genetic Algorithm to search for an optimum filter media design based on quality factor which quantifies the filter performance. A user friendly computer program is developed that provides inputs, outputs and controls to design a filter media. The program provides a starting point for constructing filter media for testing and design for particular applications.

Anion exchange membranes were prepared in the laboratory by polymerizing chloromethylstyrene with the crosslinking reagent divinylbenzene, coated on polypropylene nonwoven fabric using the paste method, and then immobilized with trimethyl and tributyl amine in a quaternarization process. The properties of these membranes were characterized in terms of ion-exchange capacity and SEM image. The kinetics of allylation of phenol was also investigated in an organic and alkaline aqueous solution in a vertical membrane reactor. The operating conditions, such as reaction temperature, kind of membrane (two laboratory- and one commercially prepared), and concentration ratio of reactants were established to achieve the optimum condition.

With a static type equilibrium cell and the pressure decaying method, the solubility of ethylene in a mixture of 2,2,4-trimethylpentane and 1-octene was measured in the temperature range of 323.15–423.15 K, pressure range of 5–25 bar, and 1-octene concentration from 0 to 85 wt%. The experimental results show that the solubility of ethylene in a 2,2,4-trimethylpentane and 1-octane mixture increases with system pressure but decreases with system temperature.

The experimental solubility data were also expressed in the vapor–liquid equilibrium relationship and correlated by the bubble pressure calculation using the Peng–Robinson equation of state (PR EOS) incorporated with the van der Waals one-fluid and the Zhong–Masuoka mixing rules. Among the deviations between the experimental and correlated results, the largest value of average absolute relative deviation is 1.73% for pressure at 423.15 K and that of average absolute deviation is 0.0024 mol fraction for vapor composition at 373.15 K by the Zhong–Masuoka mixing rule.