New advances in agitation technology for exothermic reactions in very large reactors

Organic reactions, such as polymerisations, often require precisely controlled homogeneous reaction conditions in order to achieve high product quality, minimise waste or rework, and therefore reduce environmental impact. Many such processes were originally manufactured in moderately sized reactors with a height-diameter ratio of around 1. Operators have subsequently driven up their production rates by intensifying the reaction and by increasing the reactor size (and often increased the reactor's height-diameter geometry) in response to the economic requirement for world-scale manufacturing plants.However, as reaction intensities and reactor sizes increase, product quality can be affected due to poorer homogeneity, since reaction rates are faster but bulk mixing is slower. This can lead to a “Limit to Scale” beyond which product quality is unacceptable. Better bulk mixing within very large reactors would increase the Limits to Scale.Laboratory trials were undertaken to compare the homogeneity achieved by different impeller configurations in a model of a typical large reactor. This leads to a new agitator design concept, which achieves rapid mixing in large vessels with high height-diameter ratios using a series of impellers that produce a narrowly confined axial flow, effectively a virtual draft tube, in the centre of the reactor. Fluid returns to the top of the reactor near the walls creating a loop flow pattern within the reactor, effectively an “internal loop reactor”. CFD simulations of the reactor were undertaken to better understand the hydrodynamics, and were validated against experimental results.     

N-乙烯基己内酰胺的合成

乙炔为乙烯化剂,分别在500 mL搅拌釜式反应器、500 mL塔式反应器和8 000 mL喷射环流反应器中,研究了N-乙烯基己内酰胺(NVCL)的合成。用己内酰胺(CL)和KOH制得己内酰胺钾盐为催化剂,添加助催化剂18-冠醚-6,以乙炔和己内酰胺为原料,常压法合成NVCL。粗产品经减压蒸馏及进一步精馏分离得到质量分数98%的NVCL。用FTIR、GC/MS对它的结构进行了测试和表征。研究结果表明,釜式反应器中CL转化率为30.5%时,NVCL选择性为73.4%;塔式反应器中CL转化率为31.4%时,NVCL选择性为79.2%;喷射环流反应器中CL转化率为56.7%时,选择性达85.6%。抑制反应过程中物料的黏稠化是制约合成放大成功的关键因素。     

环管反应器内传热过程的数值模拟

为了对环管反应器内传热规律进行研究,在Euler-Euler双流体动量传递模型和环管反应器聚合传质模型的基础上,考虑了环管反应器内传热过程,建立了环管反应器传热数学模型,对工业烯烃聚合环管反应器内流动、传热和传质及聚合反应过程进行了研究。反应器内浆液温度的模拟值与工业现场值吻合,说明所建立的环管反应器传热数学模型是有效的。模拟结果表明,环管反应器温度与物料浓度存在不均匀分布。在上升段,温度分布呈中心对称,在弯管段不再呈中心对称,下降段的温度因弯管段的不均匀分布而不再呈中心对称分布;随着浆液入口速度或入口固体颗粒相体积分数的增加,环管反应器上升直管段,弯管段以及下降直管段温度降低;管壁冷却水温度不同,对环管反应器内冷却能力也不同,在反应器内相同的释放热量情况下,冷却水温度越低,对反应器内物料的冷却能力就越强。     

Microfluidic dual loops reactor for conducting a multistep reaction

Precise control of each individual reaction that constitutes a multistep reaction must be performed to obtain the desired reaction product efficiently. In this work, we present a microfluidic dual loops reactor that enables multistep reaction by integrating two identical loop reactors. Specifically, reactants A and B are synthesized in the first loop reactor and transferred to the second loop reactor to synthesize with reactant C to form the final product. These individual reactions have nano-liter volumes and are carried out in a stepwise manner in each reactor without any cross-contamination issue. To precisely control the mixing efficiency in each loop reactor, we investigate the operating pressure and the operating frequency on the mixing valves for rotary mixing. This microfluidic dual loops reactor is integrated with several valves to realize the fully automated unit operation of a multistep reaction, such as metering the reactants, rotary mixing, transportation, and collecting the product. For proof of concept, CdSeZn nanoparticles are successfully synthesized in a microfluidic dual loops reactor through a fully automated multistep reaction. Taking all of these features together, this microfluidic dual loops reactor is a general microfluidic screening platform that can synthesize various materials through a multistep reaction.

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Blocking and copolymer heterogeneity in anionic copolymerization in industrial reactors

An analysis is given of the effect of reactor design on the variation of composition and extent of blocking in anionic copolymerization. Batch, pipeline, continuous stirred tank (CSTR), and recycle reactors are contrasted. Specifically, alkyl lithium-polymerized butadiene–styrene and alkyl sodium-polymerized p-methylstyrene–styrene are contrasted to the products of copolymerization of the same monomers by free-radical mechanism. It is shown for both systems that considerably more extensive blocking occurs in a batch reactor when the anionic polymerization mechanism is used. The free-radical copolymers, unlike the anionic copolymers, exhibit compositional heterogeneity in a batch reactor. Carrying out the polymerization reaction in a pipeline reactor gives results equivalent to the batch reactor if there is plug flow. However, if a parabolic profile exists in the reactor, there will be significantly increased compositional drift in the copolymer product and a broadened molecular weight distribution, with little effect on blocking. Recycle reactors, including the recirculating loop variety, seem effective in decreasing blocking. The extent of blocking may be considerably decreased in a wellmixed continuous stirred tank reactor. However, poor mixing will greatly increase both the extent of blocking and the compositional heterogeneity of the product.     

Analysis and performance of a countercurrent moving-bed chromatographic reactor

A theoretical and experimental investigation of a countercurrent moving-bed chromatographic reactor is the subject of this paper. In this reactor a reversible heterogeneous reaction takes place on catalyst particles passing downward through an upcoming gas stream. The behaviour of an ideal reactor model was examined for different values of feed concentrations and reactor length. It is predicted that reaction and separation can be achieved simultaneously and that under appropriate operating conditions, a reactor fed at the bottom with the species more favoured by thermodynamic equilibrium can lead to 100% product purity with overall conversions lower than a conventional fixed bed reactor. The effect of nonidealities on the reactor performance is also discussed. Finite adsorption and axial dispersion have a generally deteriorating effect on overall conversion and product purity. An improved reactor configuration with a bottom stripping section is suggested. Its operating conditions can be tailored so that predicted performance exceeds that of a fixed bed both in yield and product purity. The hydrogenation of mesitylene with excess hydrogen over a Pt on alumina catalyst was used for an experimental investigation of the reactor. The experiments, performed in a 1/2″ i.d., 7′ long column, resulted in products of higher purity than the equilibrium prediction, and overall conversions comparable to a fixed bed reactor.     

Modeling and simulation of an industrial slurry-phase catalytic olefin polymerization reactor series

In the present study, a comprehensive mathematical model is developed to simulate the dynamic behaviour of an industrial slurry-phase olefin catalytic polymerization loop reactor series. More specifically, the effects of various operating conditions on the dynamic reactor behaviour (i.e., reaction temperature and pressure, inflow rates of catalyst, monomers and diluent, etc.) as well as the on the molecular and rheological polyolefin properties (i.e., M_n, M_w, MWD, complex viscosity, etc.) are fully assessed. According to the proposed modeling approach, each loop reactor (i.e., consisting of the loop reactor and the settling legs) is modeled as an ideal CSTR in series with a semi-continuous product removal unit. Dynamic macroscopic mass species and energy balances are derived to calculate the dynamic evolution of the concentrations of the various molecular species as well as of temperature profiles and heat removal in the two loop reactors. The polymer molecular properties (i.e., number- and weight-average molecular weights and molecular weight distribution) are determined by employing a generalized multi-site, Ziegler–Natta (Z–N) kinetic scheme in conjunction with the well-known method of moments. All the thermodynamic calculations, regarding the equilibrium species concentration in the various phases (i.e., solids and liquid), are carried out using the Sanchez–Lacombe Equation of State (S–L EOS). It is shown that the proposed comprehensive model is capable of simulating the dynamic operation of an industrial slurry-phase cascade-loop reactor series under different plant operating policies (i.e., start-up, grade transition, etc.).     

环路反应装置与搅拌釜装置生产十二烷基二甲基叔胺的比较

给出了采用自行开发的胺化催化剂在环路反应装置和搅拌釜装置中生产十二烷基二甲基叔胺的中试结果 ,在相同催化剂下 ,与搅拌釜相比环路反应装置反应时间可缩短 5 0 %以上 ,反应选择性提高 1% ,具有明显的经济效益     

A homogeneous-heterogeneously catalysed reaction system in a loop reactor

Catalytic three-phase reactions including homogeneous liquid-phase steps were simulated in a loop reactor. The loop reactor consisted of a reaction vessel, an external loop as well as an ejector. The loop reactor was modelled using tanks-in-series or alternatively, axial dispersion models. Kinetics of the reductive alkylation of aromatic amines, which was determined from the experiments in a laboratory autoclave, was used for verifying the reactor model and for concentration profile simulations in the loop reactor.     

Analysis of process integration and intensification of enzymatic cellulose hydrolysis in a membrane bioreactor

Enzymatic cellulose hydrolysis has been studied for many years, generating rich literatures and knowledge in respect to the underlying reaction mechanism, reaction kinetics, and bioreactor systems. This paper attempts to offer some additional information and new understanding of how reaction kinetics and reactor productivity can be improved in a process involving simultaneous reaction and product separation using a purpose‐built membrane reactor with a single combined reaction zone and separation zone. Different operating strategies of batch, fed batch and continuous cellulose hydrolysis were investigated with intermittent or simultaneous removal of products (reducing sugars) to reduce enzyme inhibition and improve reactor productivity. The effect of continuous and selective product removal, reduced enzyme inhibition and higher enzyme concentration in retention were examined for the potential benefit in process integration and intensification in order to lower the high process cost of the enzymatic hydrolysis process, mainly due to slow reaction kinetics and expensive enzymes. A mathematical model was offered to account for the effect of selective product (reducing sugars) separation, permeate flux, reduced cellulase inhibition, dynamic structural change of the solid substrate and possible shear deactivation of the enzyme. Computer analysis was also carried out to analyse the quasi‐steady state of the reaction intermediates in order to gain an insight into the reaction mechanism in simultaneous reaction and separation systems. Some original analysis and simulation of the effect of membrane separation parameters on the overall reactor performance is offered, including the effect of membrane selectivity (rejection coefficient) and flux. Copyright © 2005 Society of Chemical Industry     

Spheripol工艺生产高抗冲聚丙烯

介绍了Spheripol工艺生产高抗冲聚丙烯产品的方法,采用两步复合工艺生产嵌段聚丙烯,第1步采用环管反应器进行丙烯液相均聚反应,第2步采用流化床反应器进行丙烯均聚物与乙烯单体气相共聚反应,即在气相反应器中,利用来自环管反应器中的均聚物的残余活性,加入乙烯和补充的丙烯及氢气实现乙-丙共聚,共聚物的生成使最终产品的抗冲性能大大提高,尤其是低温下的抗冲性能。     

Application of water vapor and hydrogen-permselective membranes in an industrial fixed-bed reactor for large scale methanol production

Coupling reaction and separation in a membrane reactor improves the reactor efficiency and reduces purification cost in the next stages. In this work a novel reactor consisting two membrane layers has been proposed for simultaneous hydrogen permeation to reaction zone and water vapor removal from reaction zone in the methanol synthesis reactor. In this configuration conventional methanol reactor is supported by a Pd/Ag membrane layer for hydrogen permeation and alumina-silica composite membrane layer for water vapor removal from reaction zone. In this reactor syngas is fed to the reaction zone that is surrounded with hydrogen-permselective membrane tube. The water vapor-permselective membrane tube is placed in the reaction zone. A steady state heterogeneous one-dimensional mathematical model is developed for simulation of the proposed reactor. To verify the accuracy of the model, simulation results of the conventional reactor is compared with the available plant data. The membrane fixed bed reactor benefits are higher methanol production rate, higher quality of outlet product and consequently lower cost in product purification stage. This configuration has enhanced the methanol yield by 10.02% compared with industrial reactor. Experimental proof-of-concept is needed to establish the safe operation of the proposed configuration.     

Optimization and simulation of the Sabatier reaction process in a packed bed

The Sabatier reaction in a testing packed bed was investigated experimentally and theoretically, and was used to convert waste carbon dioxide and hydrogen to provide needed water for closing the life‐support loop on orbit in space. A three‐dimensional model including fluid flow, gas dispersion, heat and mass transfer, and chemical reaction was developed by coupling some semi‐empirical correlated equations in chemical engineering science into computational fluid dynamics theory. Good agreements between the simulating results and experimental data for the effect of some parameters on reaction verified this model, for example, heat exchange between reactor and atmosphere, the material property of reactor, the catalyst deactivated and gas mass flux and so on. By using this model as the designing tools, an optimized packed bed is proposed. Compared with the testing packed bed, the relevant reactor length can be reduced from 220 to 150 mm with the same hydrogen conversion and lower pressure drop. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2879–2892, 2016     

Analysis of centrifugal annular reactor with radial flow

A model for centrifugal annular catalytic reactor is presented. The gas flows radially through the annulus while the inner cylinder is rotated to produce the centrifugal effect. A catalytic consecutive reaction takes place at the external surface of the annulus. The reactor is aimed to utilize the fact that heavier substances concentrate on the external walls of rotating reactors more than the lighter ones, so as to improve the conversion and yield of the desired intermediate product in consecutive reactions.The reaction performance is examined for various reaction kinetics, angular velocity and gas flow rate. The gas flow direction (inward or outward) is aIt is shown that for a given reaction and reactor geometry, an optimal angular velocity exists, where the reaction conversion is maximum. It is also sh     

Emulsion polymerization of vinyl acetate in a tubular loop reactor

A study was conducted on the emulsion polymerization of vinyl acetate using a loop reactor. Among the variables studied were the agitation, that is, the Reynold's number, and the effect of the presence of silver ions on the reaction rate. The molecular weight and molecular weight distribution of the polymer were determined as well as its particle size. The results are compared with earlier work done in a batch, a continuous tubular, and in a tubular loop reactor. © 1994 John Wiley & Sons, Inc.     

环路反应器工程研究

在冷态模型装置上了环路反应器的流体力学特性和化学反应特性,建立了喷嘴喉部两相流的速度与喷嘴结构和操作压力的函数。在流体力学中得到的最佳结构可用于反应器的优化设计,与搅拌反应釜的对比试验表明：环咱反应器的宏观化学速率优于搅拌反应器。     

Selective dimerisation of 1-butene in biphasic mode using buffered chloroaluminate ionic liquid solvents — design and application of a continuous loop reactor

The dimerisation of 1-butene using (cod)Ni(hfacac) as catalyst has been investigated in different chloroaluminate ionic liquids. Systems prepared by buffering an acidic ionic liquid with weak organic bases proved to be very suitable solvents for the reaction. The reaction takes place in biphasic reaction mode with facile catalyst separation and catalyst recycling. The high intrinsic dimer linearity of catalyst is maintained, but with significant enhancement of catalyst activity and of the selectivity to the dimer product over that observed in toluene solvent. For further investigation, a continuous reactor was designed. Our results in continuous mode show the general technical applicability of the selective Ni-catalysed dimerisation in chloroaluminate ionic liquids using a loop reactor concept.     

外环流氨化反应器数学模型及其放大

研究了外环流氨化反应器的流动模型、传质模型和放大规律 .结果表明 ,在工业条件下 ,此反应器中的液相流动接近于全混流 ,传质模型为kGa =0 61W0 3a q1 2a应用此模型已将反应器放大到年产 60kt固体磷酸一铵规模 .     

Optimal reaction conditions for the minimization of energy consumption and by‐product formation in a poly(ethylene terephthalate) process

We determined the optimal reaction conditions to minimize the energy cost and the quantities of by‐products for a poly(ethylene terephthalate) process by using the iterative dynamic programming (IDP) algorithm. Here, we employed a sequence of three reactor models: the semibatch transesterification reactor model, the semibatch prepolymerization reactor model, and the rotating‐disc‐type polycondensation reactor model. We selectively chose or developed the reactor models by incorporating experimentally verified kinetic models reported in the literature. We established the model for the entire reactor system by connecting the three reactor models in series and by resolving some joint problems arising when different types of reactor models were interconnected. On the basis of the simulation results of the reactor system, we scrutinized the cause and effect between the reaction conditions and the final quality of the polymer product. Here, we set up the optimization strategy by using IDP on the basis of the integrated reactor model, and the process variables with significant influence on the properties of polymer were selected as control variables with the help of a simulation study. With this method, we could refine the reaction conditions at the end of each iteration step by contracting the spectra of control regions, and the iteration process finally stopped when the profile of the optimal trajectory converged. We also took the constraints on the control variables into account to guarantee polymer quality and to suppress side reactions. Constituting six different strategies by setting weighting vectors differently, we examined the differences in optimal trajectories, the trend of optimality, and the quality of the final polymer product. For each of the strategies, we conducted the optimization to examine whether the number‐average degree of polymerization approached the desired value. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 993–1008, 2002