Steady-state multiplicity analysis of two-stage-riser catalytic pyrolysis processes

New two-stage-riser fluidized catalytic pyrolysis (TSRFCP) for maximizing propylene yield technology is considered as an efficient route to moderate the propylene demand/supply gap and to lower the propylene price. The possibility of existence of complex nonlinear behavior associated with the TSRFCP process puts limitations on the supervision of this system. Based on the developed and validated model for the TSRFCP process, this paper focuses on the elucidation of multiple steady states and relevant (in) stability characteristic over a wide range of operating condition. First, graphic analysis of heat generation/removal curves demonstrates that the TSRFCP process has at least one steady state and a maximum of three output steady states under the considered operating conditions and uncertainties such as cooling water flow rates and Conradson carbon residue. Then, operating maps revealing topologies between important input and output variables can disclose detailed nonlinear behavior (input/output multiplicity). Moreover, depending on the choice of the input variable and the relevant operating/design condition, input multiplicity may exist. In short, these results can guide the succeeding control structure selection for realistic TSRFCP processes.     

ENERGY SYSTEM INTEGRATION OF CHEMICAL PROCESSES

A combined approach of thermodynamic analysis and mixed-integer linear programming is presented for performing structural and parameter optimization in the integration of energy system of chemical processes. Tnermodynamic analysis is used to set up a superstructure configuration of energy system in order to reduce the space of search. The application of the combined approach is illustrated by a revamping integration of a large existing energy system in a refinery complex.     

TS法的改进及其在求解化工优化问题中的应用

TS算法属于现代优化算法,是局部领域搜索法的推广,常用于求解组合优化问题.利用TS法搜索过程的有向性和能够跳离局部最优解的特点,对其进行了改造,以适应求解连续变量化工优化问题.首先,根据化工优化问题变量的特性,提出了一种简便的邻域映射方案,并改进了迭代过程中自适应因子的下降函数;进一步分析对比了禁忌步数、自适应因子和初始解等参数对于优化结果的影响.然后通过算例和换热网络优化问题的求解,表明改造后的TS法在求解连续变量化工优化问题中的有效性,及其在化工优化领域的发展价值.     

STEADY STATE MULTIPLICITY FEATURES OF ETHYLENE OXIDATION ON PLATINUM FOIL

The catalytic oxidation of ethylene to carbon dioxide in excess air has been studied atsteady state.The catalyst temperature was measured for various feed temperature and concentration.The bifurcation diagrams Which describe the dependence of the catalyst temperature on the feed gastemperature were obtained for different ethylene concentrations in the feed gas.The ignition and ex-tinction temperatures were found out and the unique and multiple steady state regions could bedetermined from these diagrams.The experimental results can be satisfactorily explained by thecatastrophe theory and singularity theory.According to the steady state multiplicity features an at-tempt to discriminate the competitive kinetic models was made for the reaction.     

铂催化剂上乙烯和一氧化碳同时氧化反应多定态特性的实验研究

对铂催化剂上乙烯和一氧化碳同时氧化反应多定态特性的实验研究结果表明：在实验条件下体系最多存在有两个稳定的定态,随乙烯和／或一氧化碳浓度的增加,系统的点火温度升高,熄火温度下降,存在多定态的操作参数区域增大;在较高的乙烯和／或一氧化碳浓度条件下,系统将出现自持,实验观测不到熄火现象。通过对体系多定态特性的分析可知,同时氧化反应体系的多定态特性并不等于两个单独氧化反应体系多定态特性的简单迭加,在两个反应之间,除了热量的相互作用外,还存在着动力学抑制作用。     

煤化学净化的新发展—温和化净化

煤的深度净化需利用化学净化方法，但传统的化学净化方法反应条件苛刻，操作成本十分昂贵，过程的经济性抑制了这些方法的工业化。本文介绍几种该领域最新开发的煤的温和化净化方法，这些新方法的独特性是温和化、高效率、高选择性。有趣的是这些新方法大部分采用有机溶剂抽提煤，溶剂均可通过简单的物理方法加以回收、重新利用。这使得这些新方法在经济上更具吸引力。     

基于化学和毒性分析的焦化废水生物处理技术的比较分析

采用传统的活性污泥(CAS)和新型生物处理技术垂直折流生化处理技术(VTBR)对实际焦化废水进行了试验室处理研究,从COD、挥发酚、有机组分等化学指标和生物毒性指标对2种工艺的处理效果进行了比较评价。结果表明,发光细菌为受试生物的毒性试验,以发光强度抑制率表征VTBR、CAS出水的毒性分别为-21.2%±9.8%、12.1%±23.7%;以藻类为受试生物的毒性试验,VTBR和CAS出水对小球藻在24 h和48 h的生长抑制率无明显差异;VTBR对废水的COD、挥发酚及毒性有机物的处理效果均优于CAS,这也表明VTBR可以作为传统生物处理过程的替代工艺之一,用来解决传统生物处理工艺对毒性去除效果不理想的问题,进而减少生化出水对接受水体的生态风险。     

ON THE STABILITY OF SOME CHEMICAL PROCESSES VIA THE THEORY OF POSITIVE SYSTEMS

In this paper, an analysis of some chemical process systems is carried out using the theory of positive linear systems. Some potential simplification in the analysis of the dynamic behavior of the system is possible using this approach, and rapid qualitative predictions can be made.     

ON THE PARAMETER-SPACE CLASSIFICATION OF THE DYNAMIC BEHAVIOR OF A CONTINUOUS MICROBIAL FLOW REACTOR

Recently Agrawal et al.¹ classified the dynamic behavior of continuous stirred tank fermentor for the Monod's model and the two parameter hump function model with variable yield coefficient in the parameter space. We employed the more general three parameter substrate inhibition model which includes the Monod's model as a limiting case, derived the boundary equations which rigorously divide the parameter space of different dynamic behavior, and showed the interesting phenomenon that a limit cycle suddenly vanished for the slight change in the Damköhler number by computer simulation.     

Multiplicity Regions in a Moving‐Bed Reactor: Bifurcation Analysis,Model Extension,and Application for the High‐Temperature Pyrolysis of Methane

This paper reports studies on the bifurcation analysis and the generation of regions of multiplicity in the operation of moving‐bed reactors. The studies were first carried out for a generalized model, which allows the investigation of the effect of various scenarios, such as changes in heat capacity or the number of moles with reaction, as well as the previously unstudied equilibrium and allothermic reactions. The insights gained from this extension were then applied to an actual reaction, namely the high temperature pyrolysis of methane.     

MODELING AND PREDICTIVE CONTROL OF MIMO NONLINEAR SYSTEMS USING WIENER-LAGUERRE MODELS

In this work, a Weiner-type nonlinear black box model was developed for capturing dynamics of open loop stable MIMO nonlinear systems with deterministic inputs. The linear dynamic component of the model was parameterized using orthogonal Laguerre filters while the nonlinear state output map was constructed either using quadratic polynomial functions or artificial neural networks. The properties of the resulting model, such as open loop stability and steady-state behavior, are discussed in detail. The identified Weiner-Laguerre model was further used to formulate a nonlinear model predictive control (NMPC) scheme. The efficacy of the proposed modeling and control scheme was demonstrated using two benchmark control problems: (a) a simulation study involving control of a continuously operated fermenter at its optimum (singular) operating point and (b) experimental verification involving control of pH at the critical point of a neutralization process. It was observed that the proposed Weiner-Laguerre model is able to capture both the dynamic and steady-state characteristics of the continuous fermenter as well as the neutralization process reasonably accurately over wide operating ranges. The proposed NMPC scheme achieved a smooth transition from a suboptimal operating point to the optimum (singular) operating point of the fermenter without causing large variation in manipulated inputs. The proposed NMPC scheme was also found to be robust in the face of moderate perturbation in the unmeasured disturbances. In the case of experimental verification using the neutralization process, the proposed control scheme was found to achieve much faster transition to a set point close to the critical point when compared to a conventional gain-scheduled PID controller.     

MODELING AND PREDICTIVE CONTROL OF MIMO NONLINEAR SYSTEMS USING WIENER-LAGUERRE MODELS

In this work, a Weiner-type nonlinear black box model was developed for capturing dynamics of open loop stable MIMO nonlinear systems with deterministic inputs. The linear dynamic component of the model was parameterized using orthogonal Laguerre filters while the nonlinear state output map was constructed either using quadratic polynomial functions or artificial neural networks. The properties of the resulting model, such as open loop stability and steady-state behavior, are discussed in detail. The identified Weiner-Laguerre model was further used to formulate a nonlinear model predictive control (NMPC) scheme. The efficacy of the proposed modeling and control scheme was demonstrated using two benchmark control problems: (a) a simulation study involving control of a continuously operated fermenter at its optimum (singular) operating point and (b) experimental verification involving control of pH at the critical point of a neutralization process. It was observed that the proposed Weiner-Laguerre model is able to capture both the dynamic and steady-state characteristics of the continuous fermenter as well as the neutralization process reasonably accurately over wide operating ranges. The proposed NMPC scheme achieved a smooth transition from a suboptimal operating point to the optimum (singular) operating point of the fermenter without causing large variation in manipulated inputs. The proposed NMPC scheme was also found to be robust in the face of moderate perturbation in the unmeasured disturbances. In the case of experimental verification using the neutralization process, the proposed control scheme was found to achieve much faster transition to a set point close to the critical point when compared to a conventional gain-scheduled PID controller.     

多产品间歇化工过程最优设计的研究——启发法

修正了modi等人提出的多产品间歇化工过程最优设计的混合整数非线性规划(MINLP)模型,使之不仅允许中间贮罐的存在,还可调整以同步或异步方式操作的平行单元数.还提出了对以上模型求解的启发算法,其特点是对决策变量的初值要求低,计算速度快,所需内存小,与严格的数学规划法相比较,其相对误差小于1%.以实例说明了方法的有效性.     

VARTM用酚醛树脂的化学流变特性及模型分析

研究了一种新型的用于真空辅助树脂传递模塑成型工艺(VARTM)酚醛树脂的流变特性。根据实测等温粘度曲线,采用双阿累尼乌斯模型,建立了用于真空辅助树脂传递模塑成型工艺(VARTM)酚醛树脂的化学流变特性模型方程,分析表明模型拟合与实验结果之间具有较好的一致性,这为有效地预测RTM树脂的低粘度工艺窗口、合理制定复合材料成型工艺参数提供了必要的科学依据。     

热处理过程对Ni/Al2O3界面化学状态的影响

对用射频磁控溅射法形成的单晶及多晶Ａｌ２Ｏ３与Ｎｉ界面的化学状态进行研究。离子减薄结合Ｘ射线光电子能谱方法原位对界面电子态研究表明：未经对热处理的界面没有化学状态的变化。Ｎｉ／Ａｌ２Ｏ３（０００１）界面经退火处理后界面处Ｎｉ有多种结合态存在。Ｎ２气保护下在４００℃和８００℃对Ｎｉ／Ａｌ２Ｏ３（多晶）样品保温３０ｍｉｎ,Ｎｉ,Ａｌ化学状态变化虽不明显,但高温（８００℃）处理导致Ｎｉ向Ａｌ２Ｏ３基片内     

反向映射主成分分析方法在化工建模中的应用

基于多元统计中常用的主成分分析方法,提出了反向映射主成分分析的数据处理方法及数学分析,并通过建立重油加氢裂化反应器压降模型的实例将其与其他化工中常用的建模方法进行了比较。     

DESIGN OF RECOMBINANT PROTEIN PRODUCTION PROCESSES

A model-aided process design and supervision technique is proposed. Its efficiency is demonstrated by a nontrivial example, the development of a production process for the light chain of the antibody MAK33. This protein was expressed by the genetically modified E. coli B pUBS520 p12023 bacteria under the control of the tac promoter where lactose was used for induction. It is shown in this example that data from a few experiments are sufficient to develop a satisfactory production process. The development of process models, which are prerequisite for a systematic optimization of protein production processes, as well as their use for the determination of quasi-optimal feed-forward control profiles, is discussed. Model-supported closed-loop control is shown to lead to another improvement. Further performance enhancements can be obtained by changing the operational mode from the usually employed fed-batch procedure to a repeated fed-batch mode.     

DESIGN OF RECOMBINANT PROTEIN PRODUCTION PROCESSES

A model-aided process design and supervision technique is proposed. Its efficiency is demonstrated by a nontrivial example, the development of a production process for the light chain of the antibody MAK33. This protein was expressed by the genetically modified E. coli B pUBS520 p12023 bacteria under the control of the tac promoter where lactose was used for induction. It is shown in this example that data from a few experiments are sufficient to develop a satisfactory production process. The development of process models, which are prerequisite for a systematic optimization of protein production processes, as well as their use for the determination of quasi-optimal feed-forward control profiles, is discussed. Model-supported closed-loop control is shown to lead to another improvement. Further performance enhancements can be obtained by changing the operational mode from the usually employed fed-batch procedure to a repeated fed-batch mode.