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.     

合成异丙苯固定床鼓泡反应器模拟

建立了分子筛催化剂上合成异丙苯固定床鼓泡反应器的双区数学模型，经实际运转数据验证，说明该模型是适宜的。以此模型考察了进料方式、外循环以及进料苯烯比的影响，给出了反应器内的温度分布，并提出了固定床鼓泡反应器的改进方案。     

A fundamental CFD study of the gas–solid flow field in fluidized bed polymerization reactors

A Eulerian–Eulerian model incorporating the kinetic theory of granular flow was applied to describe the gas–solid two-phase flow in fluidized bed polymerization reactors. The model parameters were examined, and the model was validated by comparing the simulation result with the classical calculated data. The effects of distributor shape, solid particle size, operational gas velocity and feed manner on the flow behavior in the reactor were also investigated numerically. The results show that with the increase of solid particle diameter, the bubble numbers decrease and the bubble size increases, resulting in a smaller bed expansion ratio. Bed expansion ratio increases with increasing the gas inlet velocity. Moreover, the final fluidized qualities are almost the same for the plane distributor case and the triangle distributor case. There exists a tempestuous wiggle from side to side in the bed at the continuous feed manner, which could not be obtained at a batch feed manner.     

基于Aspen Plus的焦炉煤气甲烷化工艺模拟及分析

焦炉煤气作为优质的二次能源,利用焦炉煤气甲烷化合成天然气(SNG)是焦炉煤气资源化利用的最佳方式。借助Aspen Plus软件,采用BWRS状态方程,设定主要工艺参数,对绝热式三段固定床焦炉煤气甲烷化工艺进行模拟计算分析,通过调节循环率和水蒸汽添加量控制反应器出口温度,模拟结果与实际试验数据较吻合,证明模拟可靠。考察了循环率、分流率、原料气组成、进口气压力和空速对反应器出口温度和组成的影响,结果表明循环率和分流率对反应器出口温度和转化率影响明显。     

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.     

Dynamic simulation of a cascade fluidized-bed membrane reactor in the presence of long-term catalyst deactivation for methanol synthesis

In this work, a dynamic model for a cascade fluidized-bed hydrogen permselective membrane methanol reactor (CFBMMR) has been developed in the presence of long-term catalyst deactivation. In the first catalyst bed, the synthesis gas is partly converted to methanol in a water-cooled reactor, which is a fluidized-bed. In the second bed, which is a membrane assisted fluidized-bed reactor, the reaction heat is used to preheat the feed gas to the first bed. This reactor configuration solves some observed drawbacks of new conventional dual type methanol reactor (CDMR) and even fluidized-bed membrane dual type methanol reactor (FBMDMR) such as pressure drop, internal mass transfer limitations, radial gradient of concentration and temperature in both reactors. A dynamic two-phase theory in bubbling regime of fluidization is used to model and simulate the proposed reactor. The proposed model has been used to compare the performance of a cascade fluidized-bed membrane methanol reactor with fluidized-bed membrane dual-type methanol reactor and conventional dual-type methanol reactor. The simulation results show a considerable enhancement in the methanol production due to the favorable profile of temperature and activity along the CFBMMR relative to FBMDMR and CDMR systems.     

Effect of recycling the unconverted residue on a hydrocracking catalyst operating in an ebullated bed reactor

The effect of recycling the unconverted bottom on catalyst deactivation as a way to improve the hydrocracking conversion of heavy oil was analyzed using the experimental information obtained in a steady-state ebullated bed reactor. The recycle contained different amounts of partially converted (aged) material. Four sets of experiments were performed to demonstrate that after five passes through the reactor, the reactivity of the unconverted material decreased by 15% and its impact on catalyst deactivation increased by 30%. The results indicated that the higher the conversion, the lower is the reactivity and the higher is the catalyst deactivation. The production of an insoluble and refractory to convert material imposes a limit on the recycling benefit.     

四氢萘加氢裂化集总模型的建立与考察

选用国产３８２５加氢裂化催化剂，利用ＷＦ８０００Ａ型连续流动固定床微型反应器，以四氢萘为模型化合物，研究了重质馏分加氢型裂化集总动力学，根据原料，生成物的性质和沸点差异，建立了四氢萘加氢裂化七集总反应网络。     

Parametric study on the production of phosphoric acid by the dihydrate process

In this work a computer program has been developed to simulate a three-CSTR pilot plant leaching process of phosphate rock with sulfuric acid for the production of phosphoric acid and precipitation of calcium sulfate dihydrate as a byproduct. The simulation model has been examined with real experimental data obtained from the Jordan Phosphate Mines Company (JPMC), a phosphoric acid pilot plant at Rusaifa, Jordan. The predicted results are in very good agreement with the experimental data with a relative absolute error of less than 3.5%.A parametric study has been made to find the optimum operating conditions of the pilot plant for a given phosphate rock feed flow rate, chemical composition, and particle size distribution. The effect of varying reactor(s) temperature, sulfuric acid feed rate, agitator–impeller speed, ratio of slurry recycle to feed rate, and ratio of return acid to feed rate have been investigated. A reactor temperature of 80°C, slurry recycle to feed ratio of 80, and return acid to feed ratio of 2.5 have been found to give best results. The optimum conditions for sulfuric acid feed rate and agitator speed are determined only from power limitations and economics of the plant itself.     

Comprehensive Fischer–Tropsch reactor model with non-ideal plug flow and detailed reaction kinetics

This paper presents a detailed first principle Fischer–Tropsch reactor model including detailed heat transfer calculations and detailed reaction kinetics. The model is based on a large number of components and chemical reactions. The model is tuned to a fixed bed nearplug flow reactor but can also be applied to slurry and micro-channel reactors.The presented model is based on a cascade of ideally stirred reactors. This modelling approach is novel for Fischer–Tropsch reactors and has the advantage of being able to represent none-ideal reactors. Using a large number of components and reactions makes it possible to better represent the product slate than with conventional modelling based on distribution models.The results of the simulations emphasise that temperature control is important. Global conversion and product yields are dependent on operating conditions especially the temperature. The model is used to calculate the dimensions of an industrial reactor from a laboratory scale reactor.     

An optimisation approach for increasing the profit of a commercial VGO hydrocracking process

In this paper, an optimisation approach is proposed to increase the profit of a commercial hydrocracking unit called Isomax. To represent the system, a full‐lump kinetic model incorporating the flow rate of fresh vacuum gas oil (VGO), bed temperatures, recycle flow rate and the catalyst life is developed. This model is capable of predicting the yield of all products, and it improves with respect to the previous works by considering LPG and light gases, fresh VGO and recycle streams as separate lumps. After developing and validating the model, the profit function of the plant, including the value of the products, fresh feed and hydrogen, as well as energy expenses, is optimised by manipulating the bed temperatures, flow rate of fresh VGO and combined feed ratio (CFR) whilst all process limitations and operating constraints are taken into account. During two years of study and considering all mechanical and operational constraints, the results confirm that the decision variables, generated by the optimisation package, can increase the gross profit of the Isomax process to about 8.17%, which is equal to $5.6 million of net profit annually. © 2012 Canadian Society for Chemical Engineering     

Multiple steady states in adiabatic tubular reactors with recycle

In this paper numerical and pseudo-analytical methods of determining the regions of MSS in adiabatic tubular reactors with recycle are presented. These methods are valid for the general case when not only R independent reactions occur but the feed flow rate in the reactor is also a function of the recycle ratio.     

STRONG沸腾床示范装置工业应用

随着原油重质化程度的不断加深,沸腾床渣油加氢技术成为了炼厂提高渣油附加值的重要手段。抚顺石油化工研究院开发的STRONG沸腾床渣油加氢成套技术无需使用传统沸腾床技术中的高温高压循环泵及配套设备,提高了反应体系的稳定性与反应器空间利用率,降低了投资。首套采用STRONG沸腾床技术的工业化装置累计平稳运行8000 h,540℃+单程转化率达到了78%以上。     

Modeling and analysis of the Lurgi‐type methanol to propylene process: Optimization of olefin recycle

This work proposed a strategy to improve the yield of light olefins of industrial methanol to propylene process by reducing the olefins recycled back into the main reactor and appending an olefin cracking reactor. The heterogeneous fixed‐bed model was employed to simulate the reactors with a robust mathematical procedure developed to determine the reactor configuration and the recycle flow rates of the olefins. Two methods were proposed for the modulation: the recycle ratio and species of the olefins, respectively. Results show that the yield of C₂–C₃ olefins can be improved up to 70% from the basement of about 60% when the ratio is reduced from 100% to less than 23% or when only butene apart from pentene and hexene is recycled back into the main reactor, and the latter method is more effective as its catalyst requirement is seven times less than the former's in the appended cracking reactor. © 2016 American Institute of Chemical Engineers AIChE J, 63: 306–313, 2017     

流化床冷凝模式操作与乙烯聚合过程的研究Ⅱ露点提高组分对流化床反应器运行状态的影响

以Ｕｎｉｐｏｌ气相法乙烯聚合工艺作为流化床反应器冷凝模式操作的一个实例,通过模拟计算考察了在不同的操作负荷下,进反应器的循环物流的露点、组成和温度对反应器运行状态的影响,并对反应器运行的稳定性作了初步探讨。     

A recycle reactor for measuring hydrogen isotope exchange kinetics under vapour phase and trickle bed conditions

A recycle reactor system has been developed to measure the activities of catalysts for isotope exchange between hydrogen gas and water vapour. To allow testing of reasonably large quantities of catalysts, the reactor was operated with a high recirculating flow of hydrogen gas passing through a saturator to provide the water vapour required for the reaction. In this mode of operation, only a small spiking gas flow was required as feed compared to the very high feed flow that would be required for once-through operation. The reactor was also operated as a trickle bed by recirculating the saturator water. By testing catalysts under both vapour and trickle bed modes, it was possible to investigate the effect of trickling water over the catalyst on the catalytic activity. Kinetic exchange rates under vapour phase operation were calculated from both plug flow and well-mixed reactor models. The former model was found to be the appropriate one for the ranges of operating conditions investigated. However, for trickle bed operation, the well-mixed reactor model was found to be the suitable one. Vapour phase and trickle bed tests done with random bed and structured bed catalysts indicated that the gas phase isotope exchange reaction was not impaired by the presence of liquid water in the reactor.     

Dynamics and stability of ethylene polymerization in multizone circulating reactors

Multizone circulating bed reactors (MZCR) have the exclusive characteristics of producing polymers of different molecular weights in a single particle. Traditional fluidized bed reactors, on the other hand, can produce only one kind of molecular weight with relatively narrow distribution. A dynamic model for the MZCR is used to illustrate the basic dynamic behavior of the new reactor design used for polyethylene production. The model is used to study the copolymerization of ethylene with butene. Several parameter sensitivity analyses are performed to show the computer-simulated time responses for reactor temperature, number-average molecular weight, weight-average molecular weight, catalyst feed rate and the monomer/comonomer concentration along the reactor length. At certain operating conditions dynamic instability is observed and the results for the effect of cooling water temperature, catalyst feed rate, monomer and comonomer initial feed concentration on the reactor temperature and polymer molecular weight reveal that the system is very sensitive to disturbances in the heat exchanger coolant temperature. Also, at some operating conditions, the reactor temperature oscillates above the polymer melting temperature. Temperature runaway above polymer softening point is a serious problem which may cause polymer melting and hence reactor shutdown. The oscillatory behavior of the reactor temperature necessitates a suitable temperature control scheme to be installed.     

A dynamically distributed reactor model for identifying the flow fields in industrial loop propylene polymerization reactors

The use of distributed parameter model is becoming a common approach for simulating liquid–solid flow in loop polymerization reactors. However, there are still several issues with it. One of them is the absence of modeling of distributed pressure, as no thermodynamic state‐equation is incorporated into the model. In this work, inner pressure of the reactor was associated with temperature using a thermodynamic state‐equation for high‐pressure liquid. The thermodynamic state‐equation was solved together with a dynamically distributed reactor model based on the mass, energy, and momentum conservation as well as polymerization kinetics to predict the dynamic trajectories of component concentration, temperature, pressure, and bulk mass velocity in the reactor. Industrial steady‐state data were used for model validation. The application of the model was demonstrated by simulating the effect of recycle ratio on the above distributed reactor parameters. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

丙烯氯醇化反应过程的模型化

将单塔自然液相循环的丙烯氯醇化反应器视为两个串联的鼓泡塔 ,在两塔分别进行溶氯和氯醇化反应 .在对反应机理和宏观动力学进行探讨的基础上 ,建立了反应器的一维定态模型 .通过流程模拟 ,研究了操作参数对反应结果的影响 .结果表明 ,所建立的一维定态模型能正确描述重要操作参数的影响规律     

A model predictive formulation for control of open-loop unstable cascade systems

Cascade control is commonly used in the operation of chemical processes to reject disturbances that have a rapid effect on a secondary measured state, before the primary measured variable is affected. In this paper, we develop a state estimation-based model predictive control approach that has the same general philosophy of cascade control (taking advantage of secondary measurements to aid disturbance rejection), with the additional advantage of the constraint handling capability of model predictive control (MPC). State estimation is achieved by using a Kalman filter and appending modeled disturbances as augmented states to the original system model. The example application is an open-loop unstable jacketed exothermic chemical reactor, where the jacket temperature is used as a secondary measurement in order to infer disturbances in jacket feed temperature and/or reactor feed flow rate. The MPC-based cascade strategy yields significantly better performance than classical cascade control when operating close to constraints on the jacket flow rate.