1,2-Dichloroethane production by two-step oxychlorination reactions in a fluidized bed reactor

The reaction characteristics of two-step oxychlorination to produce 1,2-dichloroethane as a feedstock of PVC production were determined in a fluidized bed reactor. The effects of superficial gas velocity and gas composition on the reactivity and fluidization stability have been determined to find the optimum operating conditions in the continuous fluidized bed reactor system. It has been found that the average ethylene conversion is 94% with ethylene dichloride (EDC) selectivity of 97-98%, the average HCl conversion is 97.4%, the solid reactant conversion is 54% and a solid inventory ratio for the optimum reaction conversion is 3.3 in the process.     

流化床乙烯氧氯化制二氯乙烷催化剂研究进展

聚氯乙烯(PVC)是由氯乙烯单体聚合而成,乙烯氧氯化制氯乙烯工艺是目前世界上广为采用的氯乙烯单体制备方法。乙烯氧氯化制二氯乙烷是乙烯法生产聚氯乙烯的关键步骤,其核心是乙烯氧氯化制二氯乙烷催化剂。介绍了近年来用于流化床乙烯氧氯化反应的催化剂的开发应用现状和发展趋势。     

Modelling fast pyrolysis of biomass in a fluidized bed reactor

A compartmental one-dimensional model of a fluidized bed pyrolytic converter of biomass is presented. Reference conditions are those of non-catalytic fast pyrolysis of biomass in a shallow fluidized bed with external regeneration of the bed material. The fate of biomass and of the resulting char has been modelled by considering elutriation of biomass and char particles, char attrition as well as bed drain/regeneration. The course of primary and secondary pyrolitic reactions is modelled according to a semi-lumped reaction network using well-established kinetic parameters taken from the literature. A specific focus of the present study is the role of the heterogeneous volatile–char secondary reactions, whose rate has been modelled by borrowing a kinetic expression from the neighbouring area of tar adsorption/decomposition over char. The results of computations highlight the relevance of heterogeneous volatile–char secondary reactions and of the closely associated control of char loading in the bed. The sensitivity of the reactor performance to char elutriation and attrition, to proper management of bed drain/regeneration, and to control of gas phase backmixing is demonstrated. Model results provide useful guidelines for optimal design and control of fluidized bed pyrolyzers and pinpoint future research priorities.     

新型氧气法乙烯氧氯化催化剂研究

采用共沉淀法制备流化床氧气法乙烯氧氯化制二氯乙烷催化剂。该催化剂以氯化铜为主要活性组份，加入助催化剂氯化钾，其性能较目前使用的进口催化剂有明显改进，催化剂的活性和选择性提高，C₂H4直接深度氧化副反应得到抑制。     

Modelling and simulation of a coal gasification process in pressurized fluidized bed

A coal gasification mathematical model that can predict temperature, converted fraction and particle size distribution for solids have been developed for a high pressure fluidized bed. For gases in both emulsion and bubble phase, it can predict temperature profiles, gas composition, velocities and other fluid-dynamic parameters. In the feed zone, it could be considered a Gaussian distribution or any other distribution for the solid particle size. Experimental data from literature have been used to validate the model. Finally, the model can be used to optimize the gasification process changing several parameters, such as excess of air, particle size distribution, coal type and reactor geometry.     

Modeling of biomass devolatilization in a fluidized bed reactor

A simple model that simulates a single biomass particle devolatilization is described. The model takes into account the main physical and chemical factors influencing the phenomenon at high temperatures (>700 K), where the production of gaseous components far outweighs that of liquids. The predictions of the model are shown to be in good agreement with published data. The model is then applied to the devolatilization of biomass in a fluidized bed, in which attention is focused on heat transfer, particle mixing and elutriation, and gas production. Predictions on the overall devolatilization time for a biomass particle are compared with experimental results obtained in a fluidized bed reactor in which the process was monitored by continuous measurement of the bed pressure. Good correspondence of predicted with calculated values was obtained, supporting the validity of the many approximations made in the derivation of the governing relationships for the pyrolysis process.     

流化床中甲烷芳构化过程

在石英流化床反应器中研究了无氧条件下甲烷直接催化转化制备芳烃的过程.发现催化剂的诱导期长短、甲烷的总转化率与温度、甲烷分压及甲烷空速相关.在973 K下,液体产品中苯的选择性与萘的选择性随着催化剂的失活呈现不同的变化趋势.所得主要技术指标（甲烷转化率、苯的收率与选择性等）与固定床微型反应器中的结果相近.还研究了催化剂上的积炭对甲烷转化率、催化剂失活的影响,为将来的进一步研究提供了基础.     

Feedback linearizing control of a fluidized bed reactor

The design of an adaptive nonlinear controller for the control of a fluidized bed reactor is derived by using exact linearization techniques. Reset action and parameter adaptation are used to make more robust the precise compensation of nonlinear terms, which is called for in the linearization technique. A nonlinear antiwindup mechanism is introduced to handle reset windup problem and to provide fast response without large overshoot. Simulation results show that the proposed adaptive controller guarantees good setpoint tracking. The developed estimation algorithm allows accurate estimation of the parameters for which the regressor component is not zero.     

流化床与沸腾床内部微生物群落演变与分析

用流化床反应器和沸腾床反应器处理焦化废水,对两种反应器运行效能及微生物群落变化进行对比研究。结果表明,提高污泥负荷后流化床COD去除率优于沸腾床反应器。提高进水污泥负荷对沸腾床内微生物的冲击更大,致使其种群丰富程度下降明显。研究结果证明,流化床在宏观去除率、维持菌种丰富度方面具有较大优势。     

厌氧流化床处理红霉素废水的研究

研究了中温(33～35℃)条件下,厌氧流化床(AFB)反应器处理红霉素废水的运行特性.结果发现:进水COD为6 900 mg/L、HRT为4.4 h时,COD、BOD的去除率分别达到了76.6%、65.9%.最后利用Garrett-Sawyer关系式求出了难生物降解的有机物浓度,并利用Monod模型对实验结果进行了动力学分析,得出了红霉素废水中温条件下厌氧消化过程的基质降解规律.     

Modelling of circulating fluidized bed combustion of a char

The combustion of a char in the 41 mm ID riser of a laboratory circulating fluidized bed combustor has been investigated at different air excesses and rates of solids (char and sand) circulating in the loop. Riser performance was characterized by an axial oxygen concentration profile as well as by the overall carbon content and particle size distribution. The proposed model accounts for carbon surface reaction, intraparticle and external diffusion, and attrition. External diffusion effects were relevant in the riser dense region where char was potentially entrapped in large clusters of inert solids. Experimental data and results of the model calculations are in satisfactory agreement.     

Gas mixing in a turbulent fluidized bed reactor

A series of experiments has been conducted to study mixing and hydrodynamic behaviour of a downward facing sparger in a turbulent fluidized bed reactor. Using pressure measurement techniques, two flow discharge modes were identified around the sparger by injecting a gas tracer into the bed. These are bubbling and jetting conditions. Experimental results show that, under bubbling conditions, bubbles tend to keep their identity, while under jetting conditions a highly turbulent heterogeneous area is formed around the injection point. Due to attrition and erosion of internal heating or cooling surfaces in industrial reactors, the dominant discharge mode is the bubbling pattern. Therefore, in this investigation, the bubbling pattern is studied by measuring the radial and axial dispersion of gas tracer injected to a hot fluidized bed reactor of 20 cm diameter of FCC and sand particles. A three‐phase model is also proposed in order to predict the mixing length. In addition, the effect of sparger configuration on tracer gas mixing was examined for FCC particles.     

Development of a three-phase fluidized bed reactor with enhanced oxygen transfer

A three-phase fluidized bed reactor (TFBR) was developed in this study with the objective to achieve high rates of oxygen transfer from the gas to the liquid phase in the presence of fluidized solid particles. With 2.9 m height, 0.605 m diameter, and a short residence time of 8 h, the TFBR is particularly suitable for industrial applications such as aerobic biodegradation of high-strength wastewaters including refractory compounds. Experiments with tap water and air show that the TFBR enables complete fluidization. With the water and air superficial velocities in the respective ranges of 0.005–0.203 and 0.8–2.0 cm/s, the volumetric oxygen transfer coefficient is 2.3 × 10⁻² s⁻¹, which is higher than that obtained in similar experimental studies on oxygen transfer carried out in the past. These results suggest that the developed TFBR could be very effective in industrial applications where short hydraulic time and high gas-to-liquid mass transfer rates are desirable.     

Hydrodynamic study of a toroidal fluidized bed reactor

Hydrodynamic behavior of a newly developed toroidal fluidized bed reactor is studied in this work. The reactor has a gas distributor consisting of angled blades in an annular ring at the reactor bottom. The driving force for particles to move over the distributing blades comes from the velocity head of gas jets accelerated upon entering the blade spacing. Relevant hydrodynamic behaviors are measured with various inert materials in a pilot scale 400-mm toroidal fluidized bed reactor. The observed hydrodynamic behavior is found to be essentially predictable at ambient temperature by conventional hydrodynamic models. Fine particle tracking on the reactor wall is clearly observed through oxidation of zinc dross at a bed temperature of around 1120°C, and is simulated on the basis of a simplified mathematical model. Hydrodynamic issues, such as particle flying trajectory and retention time in the reactor, are discussed based on the developed model.     

Expansion characteristics of an anaerobic fluidized bed reactor with internal biogas production

More realistic dynamic bed‐expansion experiments using a three‐phase anaerobic fluidized bed reactor (AFBR) with and without internal biogas production were conducted for the establishment of correlation equations for the mean volume ratio of wakes to bubbles (k). A predictive model was also developed for the expansion characteristics of the three‐phase AFBR with internal biogas production. The predicted bed‐expansion heights (H_GLS) deviated by only ±10% from the experimental measurements for the three‐phase AFBR. According to the modeling results, if a three‐phase AFBR is loaded into a carrier with low specific gravity (dry density of carrier, ρ_md = 1.37 g cm^?3; wet density of carrier, ρ_mw = 1.57 g cm^?3) and operated at a high superficial liquid velocity (u_l = 4.0 cm s^?1), the ratio of H_GLS to H_LS at a high superficial gas velocity (u_g = 1.5 cm s^?1) can reach as high as 271%. A higher fluidized‐bed height has a greater effect on the bed‐expansion behavior because of the decrease in liquid pressure (surrounding gas bubbles) along the fluidized‐bed height. From parametric sensitivity analyses, H_GLS is most sensitive to the parameter reactor width (X), especially within a small ΔX/X₀ range of ±10%; sensitive to ρ_mw, diameter of the carrier, ρ_md and total mass of carrier and least sensitive to u_l, biofilm thickness and u_g. Copyright © 2005 Society of Chemical Industry     

A mathematical model for a biological fluidized bed reactor

A physical model is given in the present report for representing a three-phase biological fluidized bed reaction system which consists of microorganism-coated particles, waste water and air. The system is assumed to be well fluidized. The physical model can be represented by two differential equations describing, respectively, the substrate axial dispersion and diffusion/reaction. Numerical values of the physical parameters are selected from the literature or estimated from semi-empirical equations. The governing system equations are solved by an iterative finite-difference scheme. The theoretical predictions are compared with several experimental measurements and the agreement between them found to be very good, validating the physical model reported here.     

Continuous ethanol fermentation using immobilized yeast in a fluidized bed reactor

Continuous ethanol fermentation of glucose using fluidized bed technology was studied. Saccharomyces cerevisiae were immobilized and retained on porous microcarriers. Over two-thirds of the total reactor yeast cell mass was immobilized. Ethanol productivity was examined as dilution rate was varied, keeping all other experimental parameters constant. Ethanol yield remained high at an average of 0.36 g ethanol g^?1 glucose (71% of theoretical yield) as the dilution rate was increased stepwise from 0.04 h^?1 to 0.14 h^?1. At a dilution rate of 0.15 h^?1, the ethanol yield steeply declined to 0.22 g ethanol g^?1 glucose (44% of theoretical yield). The low maximum percentage of theoretical yield is primarily due to an extended mean cell residence time, and possibly due to the inhibitory effect of a high dissolved carbon dioxide concentration, enhanced by the probable intermittent levels of low pH in the reactor. Constant ethanol production was possible at a high glucose loading rate of 840 g dm^?3 day^?1 (attained at a dilution rate of 0.14 h^?1). Although the highest average ethanol concentration (97.14 g dm^?3) occurred at the initial dilution rate of 0.04 h^?1, the peak average ethanol production rate (2.87 g (g yeast)^?1 day^?1) was reached at a greater dilution rate of 0.11 ^h-1. Thus, the optimal dilution rate was determined to be between 0.11 h^?1 and 0.14 h^?1. Ethanol inhibition on yeast cells was absent in the reactor at average bulk-liquid ethanol concentrations as high as 97.14 g dm^?3. In addition, zero-order kinetics on ethanol production and glucose utilization was evident.     

三氯氢硅合成流化床反应器工艺改造

针对三氯氢硅生产过程中存在的流化床反应器指形管磨损漏油问题,通过对布风板改造、指形管改造、消除局部涡流、监测漏油等措施,收到了良好的效果。     

流化床电化学反应器研究进展

流化床电化学反应器是一种三维颗粒电极反应器,以其比表面积大、传质速率高而备受关注。就流化床电化学反应器在导电机理、数学模型、结构放大以及应用领域的研究现状和进展进行了综述,阐明了该类反应器开发、设计和模型化方面存在的问题,并提出了研究方向。