Dynamic optimization of membrane dual-type methanol reactor in the presence of catalyst deactivation using genetic algorithm

This paper presents a study on optimization of a membrane dual-type methanol reactor in the presence of catalyst deactivation. A theoretical investigation has been performed in order to evaluate the optimal operating conditions and enhancement of methanol production in a membrane dual-type methanol reactor. A mathematical heterogeneous model has been used to simulate and compare the membrane dual-type methanol reactor with conventional methanol reactor. An auto-thermal dual-type methanol reactor is a shell and tube heat exchanger reactor which the first reactor is cooled with cooling water and the second one is cooled with synthesis gas. In a membrane dual-type reactor the wall of the tubes in the gas-cooled reactor is covered with a pd–Ag membrane, which is only hydrogen-permselective. The simulation results have been shown that there are optimum values of reacting gas and coolants temperatures to maximize the overall methanol production. Here, genetic algorithms have been used as powerful methods for optimization of complex problems. In this study, the optimization of the reactor has been investigated in two approaches. In the first approach, the optimal temperature profile along the reactor has been studied and then a stepwise approach has been followed to determine the optimal profiles for saturated water and gas temperatures in three steps during the time of operations to maximize the methanol production rate. The optimization methods have enhanced 5.14% and 5.95% additional yield throughout 4 years of catalyst lifetime for first and second optimization approaches, respectively.     

Mathematical modeling and optimization of cyclohexane dehydroalkylation with methanol over platinum-, gallium-, and phosphorus-containing pentasil

Mathematical modeling and theoretical optimization have been carried out for methylcyclohexane dehydroalkylation with methanol over platinum-, gallium-, and phosphorus-containing pentasil in a sectionalized adiabatic reactor with intermediate heat removal and sectional methanol feeding.     

A pseudo-dynamic optimization of a dual-stage methanol synthesis reactor in the face of catalyst deactivation

This paper presents an optimization investigation on methanol synthesis reactor in the face of catalyst deactivation using multi-objective genetic algorithms. Catalyst deactivation is a challenging problem in the operation of methanol synthesis reactor and has an important role on productivity of the reactor. Therefore, determination of the optimal temperature profile along the reactor could be a very important effort in order to cope with catalyst deactivation. Our previous studies clarify the benefits of a two-stage reactor over a single stage reactor. In this study, an optimal temperature trajectory is obtained for each stage of the corresponding two-stage reactor. Here, steady state optimization is performed in six different activity levels by maximizing the yield and minimizing the temperature of the first stage of the reactor. Multi-objective genetic algorithms are used to solve this two-objective optimization. The set of optimal solutions obtained for six activity levels represents an optimal temperature trajectory for each stage, which has been extended and proposed as a dynamic optimization. This optimization resulted in an additional 3.6% yield, during the course of 4-year process.     

厌氧氨氧化结构体、形态与功能

厌氧氨氧化工艺是一种新型废水生物脱氮工艺,已成为环境工程领域的研究热点并得到广泛应用。厌氧氨氧化颗粒污泥床反应器是一种高效生物反应器,以颗粒污泥形态存在的生物相是这种反应器高效工作的必要基础。在颗粒污泥床反应器中,生物相由大到小可依次分为污泥床体、颗粒污泥以及功能菌群。综述了厌氧氨氧化结构体的形态和功能及其与装置工况的密切关系,以期为反应器的实时优化和过程控制提供指导。     

日产千吨两段径向间接换热式氨合成塔系统的模拟及操作优化

从系统角度出发，运用系统观念对氨合成塔进行了模拟和优化。认为ＴｏｐｓΦｅＳ－２００型氨合成塔是由反应床和换热器组成的不可再分块，并针对实际生产操作时的特点，较为详细地考察了入塔温度、氢氮比和冷却气体分率对整个合成塔性态的影响，在此基础上对合成塔作了优化研究，为合成氨装置的操作提供依据。     

Modeling, simulation and control of a methanol synthesis fixed-bed reactor

In this paper, the dynamic behavior and control of the low pressure methanol synthesis fixed bed reactor have been investigated. For simulation purpose, a heterogeneous one-dimensional model has been developed. First, the reactor simulation is carried out under steady-state condition and the effects of several parameters such as shell temperature, feed composition (especially CO₂ concentration) and recycle ratio on the methanol productivity and reactor temperature profile are investigated. Using the steady state model and a trained feedforward neural network that calculates the effectiveness factor, an optimizer which maximizes the reactor yield has been developed. Through the dynamic simulation, the system open loop response has been obtained and the process dynamic is approximated by a simple model. This model is used for the PID controller tuning and the performances of fixed and adaptive PID controllers are compared for load rejection and set point tracking. Finally the proposed optimizer is coupled with a controller for online optimization and hot spot temperature protection.     

Simulation of ethylene epoxidation in a multitubular transport reactor

It has been demonstrated that increased yields of ethylene oxide are obtained with a fixed-bed reactor operating with multiple injection of oxygen and cyclic adsorption-desorption of the desired reaction product. In certain conditions, this reactor simulates the operation of a larger two-tube transport reactor; the latter reactor may, in turn, be used to simulate large-scale commercial multitubular transport reactors. The small fixed-bed reactors may also be used for optimization of the process. The reaction of ethylene epoxidation on a silver catalyst is a good illustration of the advantages of a multitubular transport reactor and of this new method of simulation and optimization.     

Photochemical Production of Vitamin D2, Scale‐up and Optimization

An effective low cost method for the photochemical production of vitamin D₂ has been studied, including a 200 L batch photoreactor and a continuous reactor. Following optimization of the irradiation time (550 min), initial concentration of ergosterol (1.4 mg/mL) and the number of lamps employed (16) for the batch reactor, the conversion of ergosterol is ca. 50 %, and the selectivity yield of pre‐vitamin D₂ is ca. 84 %. The corresponding data for the continuous reactor are 73 % and 62 %, respectively.     

基于CSTR的反应器网络综合双层优化算法

反应器网络综合问题一般都是复杂的非线性规划问题,在分析基于全混流反应器的反应器网络模型特点的基础上,提出了求解该模型的双层优化算法. 通过将反应器网络综合非线性规划问题分解为物流流量和反应器体积空间的线性优化和浓度空间的优化搜索问题,降低了所求解问题的规模和难度,同时利用全局优化算法进行浓度空间的优化搜索,提高了求得全局最优解的概率. 实例研究表明,双层优化算法可以更准确地给出最优的反应器网络结构以及网络中反应器的类型和大小.     

Multiobjective optimization of an industrial styrene monomer manufacturing process

Multi-objective optimization of the operation and design of a styrene manufacturing process has been studied with the elitist non-dominated sorting genetic algorithm (NSGA-II). In the first part, the study focused on bi-objective optimization and comparative analysis of three different styrene reactor designs—the single-bed, the steam-injected and the double-bed reactors. The objectives were to simultaneously maximize styrene flow rate and styrene selectivity. In the second part, on the other hand, a tri-objective optimization study was performed involving the entire manufacturing process consisting of the reactor, heat-exchangers and separation units. Only the double-bed reactor was considered in this study for maximizing the styrene flow rate and selectivity and minimizing the total heat duty required by the manufacturing process. Results are presented and discussed in detail.     

Impinging zone reactor and its mathematical model for ozonation of waste water

The impinging zone reactor combines the high shear associated with gas‐liquid co‐injection and the impingement of two jet streams to bring about high intensity mixing in a power efficient manner. The reactor has been field tested and proven to be effective and economical for ozonation of wastewater to reduce COD (Chemical Oxygen Demand) and color. A reactor mathematical model has been developed based on fundamental principles where ozone self‐decomposition in water and mass transfer enhancement due to fast reactions are explicitly considered. The model is especially useful for reactor scale‐up design and optimization.     

DME synthesis and cyclohexane dehydrogenation reaction in an optimized thermally coupled reactor

This paper presents a study on optimization of DME synthesis and cyclohexane dehydrogenation in a thermally coupled reactor. A steady-state heterogeneous model has been performed in order to evaluate the optimal operating conditions and enhancement of DME and benzene production. In this work, the catalytic methanol dehydration to DME is coupled with the catalytic dehydrogenation of cyclohexane to benzene in a heat exchanger reactor formed of two fixed beds separated by a wall, where heat is transferred across the surface of tube. The optimization results are compared with corresponding predictions for a conventional (industrial) methanol dehydration adiabatic reactor operated at the same feed conditions. The differential evolution (DE), an exceptionally simple evolution strategy, is applied to optimize thermally recuperative coupled reactor considering DME and benzene mole fractions as the main objectives. The simulation results have been shown that there are optimum values of initial molar flow rate and inlet temperature of exothermic and endothermic sides to maximize the objective function. The results suggest that optimal coupling of these reactions could be feasible and beneficial and improves the thermal efficiency of process. Experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.     

Globally optimal reactor network synthesis via the combination of linear programming and stochastic optimization approach

Reactor network synthesis based on superstructure optimization is often a complex non-linear programming problem (NLP), which is very difficult to solve by means of the traditional optimization approaches. To solve this problem, a double-level new optimization method which combines linear programming and stochastic optimization approach is proposed in this paper. In addition, a superstructure network that includes continuous stirred-tank reactor (CSTR) and plug flow reactor (PFR) which is approximated as a series of CSTRs is constructed. By the proposed method and the superstructure network, the NLP is divided into a linear programming in flow rate and reactor volume space, and a stochastic optimization problem in concentration space. We solve two cases to illustrate the feasibility of the proposed method. The results show that this new optimization method can reduce the scales and difficulties of the problem and give more suitable structure of the reactor network, as well as better reactor size than those reported in the literature.     

A novel approach to the design and operation scheduling of heterogeneous catalytic reactors

A number of studies have been conducted to reduce the overall level of catalyst deactivation in heterogeneous catalytic reactors, and improve the performance of reactors, such as yield, conversion or selectivity. The methodology generally includes optimization of the following: (1) operating conditions of the reaction system, such as feed temperature, normal operating temperature, pressure, and composition of feed streams; (2) reactor design parameters, such as dimension of the reactor, side stream distribution along the axis of the reactor beds, the mixing ratio of inert catalyst at each bed; and (3) catalyst design parameters, such as the pore size distribution across the pellet, active material distribution, size and shape of the catalyst, etc. Few studies have examined optimization of the overall catalyst reactor performance throughout the catalyst lifetime, considering catalyst deactivation. Furthermore, little attention has been given to the impact of various configurations of reactor networks and scheduling of the reactor operation (i.e., online and offline-regeneration) on the overall reactor performance throughout the catalyst lifetime. Therefore, we developed a range of feasible sequences of reactors and scheduling of reactors for operation and regeneration, and compared the overall reactor performance of multiple cases. Furthermore, a superstructure of reactor networks was developed and optimized to determine the optimum reactor network that shows the maximum overall reactor performance. The operating schedule of each reactor in the network was considered further. Lastly, the methodology was illustrated using a case study of the MTO (methanol to olefin) process.     

Effective design of photocatalytic reactors: influence of radiative transfer on their performance

The role of radiative transfer on a photocatalytic reaction occurring in an annular reactor has been investigated by modeling the degradation of chloroform contaminating the processed aqueous stream. From the analysis of the resulting effects it is apparent that the crucial factor in assessing the performance of the reactor is the distribution of radiant energy absorption rate which, in turn, depends on the mass of catalyst and on the way it is dispersed within the reactor. An optimization of the reactor is conceivable through a proper selection of the catalyst dispersion.     

Heterogeneous Catalytic Reactor Design with Non‐Uniform Catalyst Considering Shell‐Progressive Poisoning Behavior

A novel methodology has been developed to design an optimum heterogeneous catalytic reactor, by considering non‐uniform catalyst pellet under shell‐progressive catalyst deactivation. Various types of non‐uniform catalyst pellets are modelled in combination with reactor design. For example, typical non‐uniform catalyst pellets such as egg‐yolk, egg‐shell and middle‐peak distribution are developed as well as step‐type distribution. A progressive poisoning behavior is included to the model to produce correct effectiveness factor from non‐uniform catalyst pellet. As opposed to numerical experiment with limited type of kinetic application to the model in the past, this paper shows a new methodology to include any types of kinetic reactions for the modeling of the reactor with non‐uniform catalyst pellet and shell‐progressive poisoning. For an optimum reactor design, reactor and catalyst variables are considered at the same time. For example, active layer thickness and location inside pellet are optimised together with reactor temperature for the maximisation of the reactor performance. Furthermore, the temperature control strategy over the reactor operation period is added to the optimization, which extends the model to three dimensions. A computational burden has been a major concern for the optimization, and innovative methodology is adopted. Application of profile based synthesis with the combination of SA (Simulated Annealing) and SQP (Successive Quadratic Programming) allows more efficient computation not only at steady state but also in dynamic status over the catalyst lifetime. A Benzene hydrogenation reaction in an industry scale fixed‐bed reactor is used as a case study for illustration.     

3D CFD Simulation of Reaction Cells,Cooling Cells,and Manifolds of a Flatbed Reactor for CO2 Methanation

The methanation of CO₂ has attracted great interest in recent years as a technology to generate renewable synthetic natural gas and to recycle CO₂ from different sectors. The actual development state of a flatbed reactor for the methanation of pure stoichiometric feed gas is presented. Additionally, computational fluid dynamics (CFD)-based design strategies are introduced which can be applied for the development and optimization of different processing units. The results of the reactor development demonstrate a good heat exchange and flow distribution in the reactor.     

工艺调度对乙炔加氢反应器优化运行策略的影响分析

乙炔加氢反应器是乙烯工业中用于除去高浓度乙烯流中的少量乙炔的重要装置,该装置一般持续运行较长时间,期间反应器内催化剂活性逐渐降低,直至活性难以满足工艺要求。乙炔加氢反应器全周期操作优化一般是针对装置的一个再生周期进行的,在装置运行周期内应按照操作优化方案进行。但是,在实际工业过程中,为了满足临时的工艺调度需求,乙炔加氢反应器在按照操作优化方案运行一定时间后,需要在剩余的运行周期内临时改变操作方案,这给操作优化问题带来了更多变化和挑战。基于裕量估计和慢时变系统的控制优化框架,研究了这类在运行周期中临时改变操作优化方案的全周期动态优化问题。改变操作优化方案的方式包括：变更运行周期、追求经济效益最大化和变更优化目标、追求运行周期最大化。通过对这两种改变操作优化方案的分析,发现前者变更的运行周期越接近原定运行周期,全周期总经济效益越高,后者切换时刻越早,反应器能维持的运行周期越长,但二者的全周期经济效益均不及原操作优化方案,临时的工艺调度对乙炔加氢反应器的全周期优化运行总体上是不利的。     

乳酸连续化发酵进展

对一些新型的乳酸连续化发酵装置,包括恒浊器、两级恒化器、两级固定床、两级膜细胞循环反应器、三相流化床-电渗析、塑料支持生物膜反应器及相应的发酵条件进行了综述;讨论了连续化发酵的控制(无反馈控制、反馈控制)、数学模型、最优化方法;并分析了不同连续化发酵装置的优缺点及前景.     

A comparison of conventional and optimized thermally coupled reactors for Fischer–Tropsch synthesis in GTL technology

In this research, the conditions at which a thermally coupled reactor – containing the Fischer–Tropsch synthesis reactions and the dehydrogenation of cyclohexane – operates have been optimized using differential evolution (DE) method. The proposed reactor is a heat exchanger reactor consists of two fixed bed of catalysts separated by the tube wall with the ability to transfer the produced heat from the exothermic side to the endothermic side. This system can perform the exothermic Fischer–Tropsch (F–T) reactions and the endothermic reaction of cyclohexane dehydrogenation to benzene simultaneously which can save energy and improve the reactions' thermal efficiency. The objective of the research is to optimize the operating conditions to maximize the gasoline (C₅⁺) production yield in the reactor's outlet as a desired product. The temperature distribution limit along the reactor to prevent the quick deactivation of the catalysts by sintering at both sides has been considered in the optimization process. The optimization results show a desirable progress compared with the conventional single stage reactor. Optimal inlet molar flow rate and inlet temperature of exothermic and endothermic sides and pressure of exothermic side have been calculated within the practicable range of temperature and pressure for both sides.