Heuristic evolutionary synthesis with non-sharp separators

If, in undertaking a process separation task, such as separating the constituent minerals of an ore to the most profitable extent, we allow limited separation in each process unit (as against requiring a “perfect split”), the number and connection of the units have to be found. Here it is done by building up the required flowsheet unit by unit, stopping when further addition does not increase the profit. Recycle of streams is allowed, the extent being controlled by an arbitrary parameter over which a search may be made.Simulation is sequential modular, with convergence and the necessary process optimization of each intermediate flowsheet carried out by infeasible path successive quadratic programming.As heuristics guide the construction, “good”, not necessarily “the best”, flowsheets are obtained, which may be further ranked, such as by controllability and/or process flexibility.The approach is here developed for “homogeneous” flowsheets (all process units identical), with minerals flotation separation as an example, using a very simple first-order kinetic flotation model. While countercurrent circuits are synthesized as limiting cases of the heuristics, flowsheets more profitable than these are also obtained. The paper reviews critically the heuristics and their application.     

Evolutionary search for an optimal limiting process flowsheet

The depth-first heuristic search for a process flowsheet proposed earlier by the authors is now extended to generate good (optimal) limiting process flowsheets. A look-back strategy follows the initial look-ahead procedure to eliminate the fragmentation of process tasks. Then an evolutionary search improves the process structure by eliminating the earlier dependence on the order of consideration of individual product goals followed by the implementation of by-product recycling to reduce raw material consumption. In recycling, preference is given either to those by-product streams requiring the smallest changes to the current flowsheet or to those which maximize the mass of recycled streams. Six look-back heuristics and three evolutionary rules are described.Examples of evolutionary structure generation are chosen from the production of multicomponent hydrocarbon mixtures and the production of monochlorodecane.     

Automated synthesis of steady-state continuous processes using reinforcement learning

Automated flowsheet synthesis is an important field in computer-aided process engineering.The present work demonstrates how reinforcement learning can be used for automated flowsheet synthesis without any heuristics or prior knowledge of conceptual design.The environment consists of a steady-state flowsheet simulator that contains all physical knowledge.An agent is trained to take discrete actions and sequentially build up flowsheets that solve a given process problem.A novel method named SynGameZero is developed to ensure good exploration schemes in the complex problem.Therein,flowsheet synthesis is modelled as a game of two competing players.The agent plays this game against itself during training and consists of an artificial neural network and a tree search for forward planning.The method is applied successfully to a reaction-distillation process in a quaternary system.     

An efficient tearing algorithm based on minimum sum of weights

A simple but efficient tearing algorithm for decomposition of chemical process flowsheets is described. It does not involve the use of signal flow diagrams or manipulation of any matrices. All the streams are assigned definite weights and the cut-set of tear streams is found by minimizing the sum of weights. The algorithm is equally efficient when arbitrary weights are assigned.     

A heuristic approach for petrochemical plant layout considering steam pipeline length

Plant layout design affects both investment and performance of a factory. To maximize the economic benefits of a petrochemical factory, a large number of factors must be considered simultaneously, such as material flow, heat flow and safety. However, conventional principles for plant layout design and optimization do not involve the heat flow, resulting in higher construction investment. To solve this problem, a new heuristic approach is proposed in this paper based on the current layout design principles. Both material flow (pipelines for process streams) and heat flow (pipelines for steam) are considered. Three optimization methods with different objective functions are used to optimize the layout. The application of proposed approach is illustrated with a case study. The optimal scheme and pipeline networks can be obtained, and the pipeline length is reduced significantly.     

分离五组分含复杂精馏塔流程的研究

以年费用为目标函数，对22个分离5组分混合物的精馏流程进行了研究．除了简单塔的14个序列之外，还包含8个含复杂塔（侧线汽提和／或侧线精馏塔）的流程.以不同的物系在不同的进料组成下，对流程的分离费用进行实例研究，通过分析得出构造含复杂塔精馏流程的实用规则.     

Wirbelschicht-Prozesse für die Chemieund Hütten-Industrie,die Energieumwandlung und den Umweltschutz

Fluidized bed processes for the chemical and metallurgical industries, energy conversion, and pollution control . This article presents a review of, and selection criteria for, gas/solids reactors with the aid of examples of industrially operating fluidized bed processes. The choice of optimum reactor design with regard to flow and reaction conditions, heat and mass transfer, grain size, and retention time of solids and gas is considered. In conclusion, various processes are described in terms of several process flowsheets.     

Expertensysteme – ein Hilfsmittel der Prozeß-Synthese

Expert systems for process syntheses . Commercial programs used in computer-aided development of chemical processes need a process flowsheet as starting point. Preparation of flowsheets is based largely on human experience, an uncertain kind of knowledge expressed by heuristic rules. These rules are recognized as true and advantageous in most cases without having the validity of a law. Logic programming languages derived from research on artificial intelligence are proven tools for handling heuristics with so-called “expert systems”. The flowsheets proposed by the expert system reduce all theoretically possible results to a few structures. The example of structuring distillation sequences illustrates what can be expected using an “expert system” in the area of “problem solving” by comparing its proposed sequences with optimized problems.     

Graphical approach to minimum flowrate targeting for partitioning water pretreatment units

Pretreatment is often necessary when the fresh water available to industrial plants is impure, and when some processes are particularly sensitive to contaminants. Partitioning processes such as membrane separation units are often used for such applications. However, the use of pretreatment units adds to capital and operating costs for a water system. Hence, it is of interest to develop design procedures to minimize the cost for such system. This work presents a graphical pinch analysis approach for targeting minimum flowrate of partitioning water pretreatment systems in single component problem. The approach determines how product and reject streams from the treatment unit can be allocated, along with bypassed freshwater, to satisfy multiple process sinks with their respective flowrate and purity requirements. Hypothetical case studies are presented to illustrate the approach, and generalized design principles based on pinch analysis heuristics are drawn from the examples.     

Prosyn—an MINLP process synthesizer

This paper reports the development of the program PROSYN, an automated implementation of the modelling/decomposition (M/D) strategy by Kocis and Grossmann (Computers chem. Engng 13, 797–819, 1989) for the MINLP optimization of process flowsheets. A systematic procedure is first presented for the decomposition of general superstructures of process flowsheets that avoids the optimization of units with zero flow. A model for simultaneous optimization and heat integration is also proposed that can account for area and energy considerations. Finally, a computer implementation is described that is suitable for the complex logic involved in the M/D strategy for the synthesis and heat integration of process flowsheets. Examples are presented to illustrate each of these points, as well as the performance of PROSYN.     

Extractive Distillation Systems Involving Complex Columns with Partially Coupled Heat and Material Flows

A method based on the representation of flowsheets as graphs is proposed to synthesize flowsheets of extractive distillation of multicomponent azeotropic mixtures in complex columns with partially coupled heat and material flows. It is shown that the flowsheets constructed can provide a significant decrease in the energy consumption for separation because the process becomes structurally closer to thermodynamically reversible distillation.     

复杂化工过程系统的能值计算方法

针对复杂过程系统的生态化设计,研究系统内部及输出流股能值的计算策略和方法。基于系统能量或质量流程图,确定系统内外的能流、物流的分布和能量分配系数,通过建立复杂系统能值计算的循迹法,确定系统各种输入能值在系统内的分配,解决复杂系统内部联结各单元的流股能值准确计算问题。基于该方法,对玉米燃料乙醇生产过程系统进行了能值分析和评价。     

烃类分离装置通用流程模拟系统

本文介绍“烃类分离装置通用流程模拟系统”的微机版本。该模拟程序进行流程的物料平衡和能量平衡计算,满足气体分离、乙烯等石油化工工业的工艺模拟需要。该模拟系统便于使用,具有灵活可变的结构。用户无需编写任何执行程序。对不同流程、程序会自动生成不同的执行程序。通常为进行模拟计算,仅需下述四方面的工作:①根据工艺流程图作出信息流程图;②对物流及单元过程分别编号;③输入工艺参数及初值;④执行运算。该模拟系统适用于IBM-XT,IBM-5550机及任何相当的微机。     

Automated Flowsheet Synthesis Using Hierarchical Reinforcement Learning: Proof of Concept

Recently we showed that reinforcement learning can be used to automatically generate process flowsheets without heuristics or prior knowledge. For this purpose, SynGameZero, a novel two-player game has been developed. In this work we extend SynGameZero by structuring the agent's actions in several hierarchy levels, which improves the approach in terms of scalability and allows the consideration of more sophisticated flowsheet problems. We successfully demonstrate the usability of our novel framework for the fully automated synthesis of an ethyl tert-butyl ether process.     

Simultaneous Measurement Bias Correction and Dynamic Data Reconciliation

The presence of measurement bias and random noise significantly deteriorates the information quality of plant data. Data reconciliation techniques for steady-state processes have been widely applied to processing industries to improve the accuracy and precision of the raw measurements. This paper develops an algorithm for simultaneous bias correction and data reconciliation for dynamic processes. The algorithm considers process model error as an important contributing factor in the estimation of the measurement bias and process state variables. It employs black-box models for the process as would be done when phenomenological models are difficult or impractical to obtain. Simulation results of a distillation column demonstrated that this algorithm effectively compensates constant and non-constant measurement biases yielding much improved reconciled values of process variables. It has computational advantages over previously proposed algorithms based on non-linear dynamic data reconciliation because an analytical solution is available when using linear process models to approximate the process.     

顺序流程乙烯装置冷区扩能改造方案探讨

乙烯装置分离冷区工艺流程复杂,技术难度高,是全装置工艺设计的关键.以某200 kt/a乙烯挖潜改造、1100 kt/a乙烯装置改造和1190 kt/a乙烯装置改造为例,着重论述了顺序分离流程冷区改造的工艺技术特点,对深冷及脱甲烷系统、制冷系统和碳二分离系统的工艺改造方案进行了说明,分析了各装置在具体改造方案上的工艺技术...     

Jenike型剪切测试仪在颗粒物料流动性测试中的应用

流动性测试能够准确地获得颗粒物料的相关特性,为设计颗粒物料处理工艺及设备提供准确可靠的依据。介绍了颗粒物料流动性的描述方法,以及用Jenike型剪切测试仪进行颗粒物料流动性测试的方法,分析了该测试试验存在的问题,并提出了解决方法,为颗粒物料流动性测试提供指导。     

聚合物精密挤出过程中挤出流量的在线测量及控制方法

介绍了以PLC为控制核心的聚合物精密挤出成型过程的参数测量控制系统,针对描述挤出过程稳定性指标的参数.挤出流量的测量进行了详细描述,根据控制精度和挤出制品的不同,可以分别采用齿轮泵转速测量法、失重计量加料法、制品外径测量法3种不同在线测量及相应的控制方法,同时从测量原理、测量精度及应用范围等方面进行比较分析.     

Separation sequencing. use of information distance

A fast process synthesis procedure is developed for generating preliminary separation schemes. The main approach is based on similarity indices obtained from chemical, physical and operating properties between two chemical species in a separation scheme. For the whole set of species, a similarity matrix results. On this basis, algorithms for classifying chemical species and generating separation sequences are developed. A distance between flowsheets is used in order to compare different separation schemes with one another or to some reference cases. The weights of the properties and heuristics are adjusted to account for well-known optimal cases. Changes in the number of considered separation properties and in their hierarchy are also used to improve the procedure. The algorithm requires very little calculation and can even be implemented by hand in the simplest cases. Extensions of the algorithm include the use of actual values of the separation properties instead of boolean ones and the generation of non-sharp flowsheets.