SCALE-UP OF HOLLOW FIBER REACTOR SYSTEMS

Hollow fiber reactors have been developed for many biochemical and biomedical applications. In the study of these reactor systems, we have used single fiber reactors as a prototype for the larger hollow fiber cartridges. Experiments using single fibers have been conducted to obtain conversion data for reactor scale-up. We present a model for predicting conversions in bench-scale hollow fiber cartridges using these single fiber data. The model is compared to experimental conversion data and is shown to be a valuable design tool.     

Nutrient and metabolite gradients in mammalian cell hollow fiber bioreactors

This work has investigated high density CRL-1606 hybridoma cell culture in the shell-side of ultrafiltration hollow fiber bioreactors. Oxygen depletion was measured in the recycle stream, and has been identified as the critical, axial scale-limiting factor in these reactors. The composition of the extracapillary space has been studied by rapidly freezing these reactors in liquid nitrogen to recover samples of the shell-side environment. The accumulation of inhibitory metabolites should have only a marginal impact on growth and product formation of this hybridoma cell line. Oxygen depletion is expected to be the major limiting factor for both the axial and radial scale-up of hollow fiber bioreactors.     

Retrofitting of Fixed-Bed Heterogeneous Reactors for Glucose Isomerization

A retrofitting strategy is proposed here that can enhance the conversion level while significantly reducing the pressure drop in fixed-bed glucose isomerization reactors. The proposed strategy utilizes hollow support matrix for enzyme immobilization instead of commonly used solid spherical support. The absence of core in hollow catalytic support helps to lower diffusional resistances, thus ensuring a better utilization of the catalytic material. This leads to higher conversion in the reactor. Moreover, the use of hollow packing yields high bed void fraction, which helps to substantially lower the pressure drop. Specifying the proposed hollow support matrix as being either cylindrical or ring shaped, a rigorous heterogeneous model for the glucose isomerization reactor is developed here. The model validity is first tested by using reported experimental data for spherical support. Using the present model, the reactor performance can be optimized in terms of shape parameters of the proposed hollow support for enzyme immobilization.     

Oxyfuel combustion using a catalytic ceramic membrane reactor

Membrane catalytic combustion (MCC) is an environmentally friendly technique for heat and power generation from methane. This work demonstrates the performances of a MCC perovskite hollow fibre membrane reactor for the catalytic combustion of methane. The ionic–electronic La_0.6Sr_0.4Co_0.2Fe_0.8O₃₋ (LSCF6428) mixed conductor, in the form of an oxygen-permeable hollow fibre membrane, has been prepared successfully by means of a phase-inversion spinning/sintering technique. For this process polyethersulfone (PESf) was used as a binder, N-methyl-2-pyrrollidone (NMP) as solvent and polyvinylpyrrolidone (PVP, K16-18) as an additive. With the prepared LSCF6428 hollow fibre membranes packed with catalyst, hollow fibre membrane reactors (HFMRs) have been assembled to perform the catalytic combustion of methane. A simple mathematical model that combines the local oxygen permeation rate with approximate catalytic reaction kinetics has been developed and can be used to predict the performance of the HFMRs for methane combustion. The effects of operating temperature and methane and air feed flow rates on the performance of the HFMR have been investigated both experimentally and theoretically. Both the methane conversion and oxygen permeation rate can be improved by means of coating platinum on the air side of the hollow fibre membranes.     

中空纳米材料功能化及在催化反应中的应用

近年来,中空纳米材料以其独特的结构和优异的性能,在许多学科研究中引起了广泛的关注。中空纳米结构具有高的比表面积、明确的活性中心、有限的孔隙空间和可调的传质速率,可在光催化、电催化、均相、非均相等多种催化反应中作为催化剂、载体和反应器。基于最先进的合成方法和表征技术,研究者们致力于中空纳米材料有目的功能化,以用于研究催化机理和复杂的催化反应。本文综述了如何构筑纳米反应器以实现更高活性和选择性的催化反应。尤其是关于中空纳米材料的表面功能化策略,具体包括形貌和组成改性、包封、多壳层构筑、单原子位点设计、表面分子工程化等五大部分,为中空纳米材料功能化变为有效催化剂的合理设计和开发提供了理想的模型。     

Computational scheme for the calculation of molecular weight distributions for nylon 6 polymerization in homogeneous,continuous-flow stirred-tank reactors with continuous removal of water

An efficient computational scheme has been established for obtaining the molecular-weight distributions (MWDs) for Nylon 6 polymerization in homogeneous, continuous-flow stirred-tank reactors (HCSTRs) with water vaporization. A three-step procedure is used: the moment equations are solved by a sequential application of Brown's algorithm, the moments so calculated are used to give an empirical Flory-Schultz distribution and, finally, this empirical distribution is used as a starting guess in Brown's algorithm applied to species mass-balance equations to give the exact MWD. The moment-closure approximations normally used for hutch reactors have been found to work equally well with HCSTRs for residence times of industrial significance.     

Numerical calculation of parameters of an ensemble of particles in a perfectly mixed fluidized-bed reactor

The problem of numerical calculation of parameters (mass; fractional makeup; entrainment, settling, and discharge flow rates) of the solid phase in a perfectly mixed fluidized bed of reacting particles in flow and batch reactors and in a system of two flow-coupled reactors is considered. A system of equations is suggested for solving this problem for an arbitrary particle size distribution in the feed stream and for an arbitrary dependence of the shrinkage or growth of the particles on their diameter. Expressions for calculating the mass and fractional makeup of the dispersed material at the induction stage have been obtained. Calculation of parameters of an ensemble of particles in a recycle reactor is described. The particular cases of flow and batch reactors and a system of two flow-coupled reactors have been considered for different dependences of the transformation rate of the particles on their size at an arbitrary fractional makeup of the feed stream.     

新型固定床加氢反应器内构件的研究与应用

叙述了抚顺石油化工研究院(FRIPP)开发的固定床加氢内构件,包括内置集垢器、喷嘴式分配器、旋叶式冷氢箱,主要介绍了其结构及工作原理,并且在国内应用的效果.该内构件技术能保证直径3400 mm柴油加氢反应器的径向温差小于2℃.     

A Review of Process Aspects and Modeling of Ebullated Bed Reactors for Hydrocracking of Heavy Oils

The main characteristics of ebullated bed reactors have been reviewed in this work. Key factors of the application of these reactors to hydrocracking of heavy petroleum fractions, such as sediments formation, catalyst attrition and catalyst deactivation, have been clearly discussed. Mathematical representation of ebullated bed systems has been organized into hydrodynamics, scaling down and reactor modeling. Only a few reports dealing with the topic of this review were found in the literature, which employ different levels of sophistication to establish the model equations. These literature reports were summarized and properly discussed, from which it has been recognized that modeling of ebullated bed reactors is a complex task and deserves more attention.     

Modeling of Radial Flow Reactors of Oxidative Reheat Process for Production of Styrene Monomer

Styrene plays an important role in industrial production plants due to its increasing use in the production of various products. Thus, availability of a simulating program for styrene monomer reactors is of major importance in reducing the problems of a styrene unit. In oxidative reheat technology, styrene monomer is produced from ethylbenzene dehydrogenation in radial flow reactors in the presence of the generated heat from hydrogen oxidation reaction. In this article mass, energy and momentum equations on radial direction are developed for styrene monomer reactors. Required kinetic rates and parameters have been adopted from the literature [1,2]. Then, by means of experimental data from industrial reactors and sequential quadratic programming (SQP) methods, suitable kinetic parameters are obtained. Comparison of simulator prediction data with industrial ones show that the simulation has been achieved adequately.     

膜萃取的应用研究

膜萃取是膜分离与液－液萃取相结合的一种新型分离技术。本文综述了膜萃取在金属萃取、有机物萃取、生化产物及药物萃取以及膜萃取生物降解反应器和酶膜反应器等方面的研究,讨论了膜萃取付诸实施的关键。指出,当前膜萃取过程付诸实施的关键是膜材料的开发和传质的强化并提出中空纤维膜萃取器是实现膜萃取的重要装置。     

Tube-wall reactor modelling for multiple reaction networks with non-linear kinetics and volume change

Tube-wall reactors are gaining importance for highly exothermic and fast chemical reactions because of their simple construction and improved temperature control. A generalized mathematical model of the non-isothermal annular tube-wall reactors for simultaneous catalytic reactions with mixed type non-linear reaction kinetics and volume change is developed. Numerical solutions of two-dimensional component transfer equations, heat transfer equation and fluid flow equation may be obtained with appropriate boundary conditions using a recently developed orthogonal collocation method for annular geometries. The model has been successfully applied to the tube-wall reactors for the Fischer-Tropsch Synthesis. Comparison between model predictions and previous experimental results is good.     

The prediction of the performance of simple catalytic reactors for Fischer-Tropsch type catalytic polymerization reactions

Kinetic equations based on the Schultz-Flory theory and simple power law kinetics for the product distributions are used in a special class of catalytic polymerization reactions of which Fischer-Tropsch reactions form a sub-class. These kinetic equations are tested using selectivities obtained from the literature and at SASOL. The equations are mathematically tractable and allow the integration of the material balance equations in isothermal reactors. The result is a fairly simple model which may be used in the design and characterization of such reactors.     

Prediction of the Induced Gas Flow Rate from a Self‐Inducing Impeller with CFD

The complex task of describing computationally two‐phase turbulent flows in aerated stirred‐tank reactors was overcome by proposing that the gas flow rate in the hollow impeller can be estimated from single‐phase flow simulations of the liquid phase in the reactor: the pressure at the impeller surface obtained from liquid phase simulations can be related to the gas induction rate. A commercial lab‐scale reactor with a radial six‐bladed hollow impeller was chosen for the study. To validate the presented methodology, the induced gas flow rate was measured experimentally from the tracking of the position of bubbles in a dynamic sequence of flow images. Notwithstanding the simplifications assumed in the presented CFD methodology, good agreement has been obtained between numerical results and experiments.     

气固两相流内中空多孔催化剂性能的数值模拟

气固流态化过程中流体和颗粒分别聚集,形成稀密两相,严重限制其传质效率和反应速率的提高。针对此问题,本工作设计了一种中空多孔结构的催化剂颗粒,通过模拟方法研究该颗粒对稀密两相气相传质与反应的影响,及其在稀密相间转换的时间尺度。结果表明,一定的流动强度时,在颗粒稀密相转换的时间尺度内,中空多孔结构的颗粒能够有效地在稀相存储反应气体,并在密相释放,为密相提供额外的反应气体,增强体系的整体反应效率。当催化反应速率高于传质速率时,在所研究的流动条件下中空多孔颗粒体系的反应效率比实心球形颗粒体系高出26.92%~29.55%。可以预见在稀密相分布更广的大型气固流化床反应器中,中空多孔结构的催化剂颗粒能够更为有效地提高反应器的整体效率。     

Comprehensive modeling and CFD simulation of absorption of CO2 and H2S by MEA solution in hollow fiber membrane reactors

A comprehensive mathematical model has been developed for the simulation of simultaneous chemical absorption of carbon dioxide and hydrogen sulfide by means of Monoethanolamine (MEA) aqueous solution in hollow fiber membrane reactors is described. In this regard, a perfect model considering the entrance regions of momentum, energy, and mass transfers was developed. Computational Fluid Dynamics (CFD) techniques were applied to solve governing equations, and the model predictions were validated against experimental data reported in the literature and excellent agreement was found. Effects of different disturbances on the dynamic behavior of the reactor were investigated. Moreover, effects of various parameters such as wetting fraction, gas and liquid inlet velocities, inlet temperature of the solvent, MEA concentration, and CO₂ and H₂S compositions were carefully studied. It was found that for large values of gas velocity or small values of liquid velocity, the thermal energy equation can play an important role in the model predictions. © 2013 American Institute of Chemical Engineers AIChE J 60: 657–672, 2014     

A Novel Radial‐Flow,Spherical‐Bed Reactor Concept for Methanol Synthesis in the Presence of Catalyst Deactivation

A radial‐flow, spherical‐bed reactor concept for methanol synthesis in the presence of catalyst deactivation, has been proposed. This reactor configuration visualizes the concentration and temperature distribution inside a radial‐flow packed bed with a novel design for improving reactor performance with lower pressure drop. The dynamic simulation of spherical multi‐stage reactors has been studied in the presence of long‐term catalyst deactivation. Model equations were solved by the orthogonal collocation method. The performance of the spherical multi‐stage reactors was compared with a conventional single‐type tubular reactor. The results show that for this case study and with similar reactor specifications and operating conditions, the two‐stage spherical reactor is better than other alternatives such as single‐stage spherical, three‐stage spherical and conventional tubular reactors. By increasing the number of stages of a spherical reactor, one increases the quality of production and decreases the quantity of production.     

A Modeling Approach to Reaction of Non-Newtonian Fluids in Tubular Reactor

The treatment of non-Newtonian fluids in tubular reactors is frequently encountered in industries, which may be studied by mathematical modeling. The modeling of endothermic reactions of non-Newtonian fluids in tubular reactors with radial dispersion has been done for Ostwald-de-Waele power law fluids. The coupled mass balance, heat balance and velocity equations have been dealt with. The model is solved using finite difference numerical methods. The effect of variation in the dimensionless parameters of the model has also been studied. In addition, the rheological parameter n also affects the reactor performance as well as the velocity profile. An increase in n leads to higher velocity distortion and a decrease in conversion and temperature.