Batch Chemical Plants Research Articles

A general algorithm for short-term scheduling of batch operations—I. MILP formulation

A general framework for handling a wide range of scheduling problems arising in multiproduct/multipurpose batch chemical plants is presented. Batch processes involving a variety of complexities are represented using a state-task network. The novel feature of this representation is that both the individual batch operations (“tasks”) and the feedstocks, intermediate and final products (“states”) are included explicitly as network nodes. Processes involving sharing of raw materials and intermediates, batch splitting and mixing and recycles of material, can be represented unambiguously as such networks. The short-term scheduling problem is formulated as a mixed integer linear program (MILP) based on a discrete time representation. Flexible equipment allocation, variable batchsizes and mixed intermediate storage policies involving both dedicated and multipurpose storage vessels are taken into account. Limited availability of raw materials, both at the start and during the time horizon of interest, is accommodated. Product deliveries may take place at any time during the horizon, and the amounts involved may be either fixed or variable. The use of utilities by the various tasks may vary over the task processing time, and may be constant or proportional to the batchsize. The availability and/or cost of utilities may vary over the time horizon of interest. The objective function is the maximization of a profit function involving the value of the products, and the cost of raw materials, utilities and material storage. The formulation may result in MILPs involving large numbers of binary variables. Issues pertaining to the efficient solution of these problems are discussed in Part II of this paper.

A general algorithm for short-term scheduling of batch operations—II. Computational issues

The first part of this paper (p. 211) presented a general mathematical framework for describing a wide variety of scheduling problems arising in multiproduct/multipurpose batch chemical plants. The problem is formulated as a large mixed integer linear programming model (MILP). We describe a variety of techniques that exploit the characteristics of the problem in order to reduce the amount of computation required. These include reformulation of some of the constraints, derivation of an alternative and much more compact linear programming relaxation of the MILP, and reduction of the non-integrality of the solutions of relaxed LPs through their a posteriori analysis. The combination of the three measures results in a significant improvement in computational performance without compromising the optimality of the solution obtained. A case study is presented to illustrate the applicability of the method to the scheduling of multipurpose plants under a variety of operational constraints.

Retrofitting a general multipurpose batch chemical plant

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRetrofitting a general multipurpose batch chemical plantSavoula Papageorgaki and Gintaras V. ReklaitisCite this: Ind. Eng. Chem. Res. 1993, 32, 2, 345–362Publication Date (Print):February 1, 1993Publication History Published online1 May 2002Published inissue 1 February 1993https://doi.org/10.1021/ie00014a012RIGHTS & PERMISSIONSArticle Views59Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (4 MB) Get e-Alerts Get e-Alerts

A new approach for determination the horizon constraints for design problem of multipurpose batch chemical plants

Referring to the multiperiod design model of multipurpose batch chemical plants, a novel approach for determination of the equivalent horizon constraints based on graph theory, and in particular, on obtaining a family of maximum independent vertex sets, is considered. A suitable method to find a family of maximum independent vertex sets, is proposed.

A new approach for determination the horizon constraints for design problem of multipurpose batch chemical plants

A new approach for determination the horizon constraints for design problem of multipurpose batch chemical plants

Automatic Synthesis of Chemical Batch Plant Procedures: A Qualitative Process-Centered Approach

This paper describes a system for the synthesis of batch operating procedures that is based on an “process-centered” qualitative modeling approach and MILP optimization. The concept of the Operation Procedures Network (OPNet) is introduced to describe the possible abstract (i.e. hardware independent) processing paths leading to the desired goal from a given starting scenario. The solution method is hierarchically organized into: (1) OPNnet generation, (2) its translation into a mixed integer parametric model (now hardware specific), (3) the “optimal” solution of this MIP problem, and (4) determining the sequence of simple operator actions required to carry out the processing tasks.

Scheduling of multipurpose batch chemical plants. 1. Formation of single-product campaigns

The single-product campaign formation problem is defined and a mixed integer nonlinear programming (MINLP) formulation is presented. The difficulties encountered in solving this formulation are discussed, a decomposition strategy to solve the problem is presented, and the effectiveness of the solution procedure is illustrated with an example

Scheduling of multipurpose batch chemical plants. 2. Multiple-product campaign formation and production planning

The single-product campaign formation decomposition algorithm, which is presented in part I, is extended to identify dominant multiple-product campaign based on the same linear dominance property used by Mauderli and Rippin. A production planning formulation for multipurpose batch plants is presented that selects from the set of previous by identified dominant campaigns and accounts for changeover and startup times of the production lines in each campaign. The dominant campaigns are then identified for the example multipurpose plant from Mauderli and Rippin, and several production planning problems are solved to illustrate the improvement in plant performance using the optimal dominant campaigns compared with the campaigns identified by Mauderli and Rippin

Equipment arrangement for batch plants in multi-floor buildings with integer programming.

In the planning of multi-floor chemical batch plants, consideration of various preferences about equipment arrangement is necessary because of the amount of manual operation involved. These preferences are generally expressed as equations that change with conditions, and it is not easy to find the optimum equipment arrangement. In this proposed method for equipment arrangement, “components,” the elements of arrangement, are made up of equipment units of common size or parts of large ones, and are respectively assigned to “positions” given at each floor. Preferences are expressed as items that are weighted according to preferable configurations between components. The objective function is the summation of weights of unsatisfied preferences. This problem is represented by an integer programming model resulting from the input of many considerations, including for example the introduction of dummy variables. An explanation of the formulation and its effectiveness is illustrated by example problems.

The design of flexible chemical plants by the application of interval mathematics

Reliable methods for the design of multiproduct batch chemical plants under uncertainty are expensive in computing time. Useful practical results can be obtained more speedily by the application of interval optimization. In a two-stage procedure for optimal design under uncertainty the inner optimization, comprising a stochastic linear program, is replaced by a linear interval optimization procedure. The influence of both more and less optimistic design stategies and of various problem parameters in the resulting designs is presented.

Scheduling for multipurpose batch chemical plants

The present paper is concerned with planning problems in multipurpose batch chemical plants. Concepts and solution proposals are presented for rough and fine planning with the help of Gantt chart drawing. The aim is to simulate and assess the consequences of decisions and to establish proposals for solution and aspects of implementation as well as to establish real orders for work. The consideration of specified restrictions for the model and their realization on a low cost microcomputer is described. In long-term and short-term planning of multipurpose plants for the production of fine chemicals, complicated scheduling problems occur. It is shown that even for complicated models the computer aided establishment of Gantt charts using a low- cost micro-computer is possible.

An integrated approach to computer-aided operation of batch chemical plants

The design and implementation of a computer-based system which integrates planning and plant control of batch chemical plants is presented. Such a system is required so that the full benefits of computer-aided operation, increased production, improved product quality and reduced operating costs may be realized. A functional analysis of the operational requirements of batch plants indicate that a hierarchical and distributed system is favoured. A new operational activity, batch management, is defined which provides the necessary integration by coordinating the activities of the planning and control levels. Batch management allows the control level activities to be driven by events at the planning level such as changes in product demands. It also provides a feedback path from the control level back up to the planning level so that the inherent variability of batch processes can be accounted for and overcome. This is achieved by dynamic, on-line rescheduling. A very general implementation of this design is described. The implementation is centred around a real-time database and permits the operation of a wide range of processes including multiproduct, multipurpose plants with both serial and parallel lines, intermediate storage, shared utilities, etc. To demonstrate its effectiveness, two applications are presented, one in conjunction with an on-line, real-time control system, and the other with an off-line discrete event simulator. The significant benefits achieved in terms of improved operation are discussed.

Optimal design of multi-purpose batch chemical plants

A new solution method has been developed for the optimal design of multi-purpose batch chemical plants. The minimum capital investment cost serves for the optimality criterion. The algorithm is built upon two decomposition stages: a combinatorial step allowing the use of some heuristics and a nonlinear programming stage. A quasi-optimal solution is guarantied.

Minimizing the effects of batch process variability using online schedule modification

Using a fixed offline schedule to operate a batch chemical process, which is inherently variable in its processing times, can lead to both batches waiting for processing units to become available and increases in unit idle times. In this paper, the development of real-time online schedule modification techniques to minimize these effects of batch process variability is presented. Several schedule modification algorithms were developed and their performance in operating a simple flowshop system is shown. It was found that a predictive algorithm provided the best performance with definite improvements over operations that used the fixed offline schedule. This predictive algorithm, called the projected operation modification algorithm, estimates, from the current operation, the expected operation of the batch plant into the future, and searches for possible increases in wait times or idle times. Corrective action is then taken by changing the start times of the scheduled but not-yet-executing batches. The improvement in operation resulting from online schedule modification on a complex flowshop case study indicates that a more integrated approach to computer-aided operation of batch chemical plants, combining offline scheduling, process control, and online schedule modification, is needed.

On the design of multi-purpose batch chemical plants

An algorithm is proposed for the automatical design of large multi-purpose batch chemical plants. This first design is improved in an iterative process by alternatively evaluating the plant through the solution of the scheduling problem, and changing the plant.

Optimal assignment of products to equipment items in multi-purpose batch chemical plants

A subproblem of scheduling is considered; the optimal assignment of products to equipment items, neglecting the order and sequencing of processing steps. This problem arises, if differences exist in the suitability of equipment items for processing different kinds of processing steps. The optimal compromise between capacity and suitability must be determined. Further, the influence of earliest starting time and latest completion time and the use of additional tools of limited number for optimal assignment is considered. In all cases models are proposed, which transform the problem into a capacitated network, on which a Hitchcock transportation problem has to be solved. This enables the use of standard mathematical software.

Short-term scheduling for multiproduct batch chemical plants

A computer program is described for the short-term scheduling of multiproduct batch chemical plants. Given available equipment, product delivery dates and equipment requirements for each product, batches are sequenced to meet the delivery dates while taking account of penalties associated with product changeovers and storage costs. Precedence constraints are considered for intermediate products, as are constraints on the availability of shared resources which limit the operations that can be carried out in parallel.

On the solution of scheduling problems for multi-purpose batch chemical plants

A solution strategy for solving the scheduling problem in the case of multi-purpose batch chemical plants is described. The plant may contain several identical examples of any of the types of process unit. The problem is characterized by requirements such as —branching in batch and device —maintenance of a fixed time regime in the production of one batch —changeover times when products are changed, etc. The centre of the heuristic strategy of solution is an exact algorithm which examines whether or not a batch with a given starting time can be scheduled. The appropriate subprogram can be easily incorporated into programs realizing known heuristic scheduling principles, which were developed for solving simpler problems. Examples with 68 process units, 600 shits and 350 batches have been computed on a EC 1040 computer in 10–15 minutes.

Design and operation of multiproduct and multipurpose batch chemical plants. — An analysis of problem structure

The general structure of batch processing problems is reviewed. A classification scheme is presented which analyses the specification of the system components, -comprising product requirements, specification of process tasks and available equipment items, followed by consideration of constraints on system structure, problem definition and solution methods. A hierarchy of model types for batch units is proposed for use in different problem situations. Examples of the use of the scheme are provided by the classification and comparison of selected publications on batch processing and the scheme is also used to draw attention to potential areas for further work. Brief remarks are added on problem size and computational experience in different areas of batch processing.

Ergonomic Evaluation of Control Rooms: Two Case Studies

A research project was started to analyse the ergonomic aspects of control rooms in the (chemical) process industries. We want to prepare an ergonomic guide for designers of control rooms. Most recommendations in that guide wil emanate from field studies, i.e. evaluations of existinq control rooms. Two case studies of that kind are presented here. The methods of the evaluations, e.g. interviews and observations, will be explained. Results of both studies, one in a chemical batch plant and one in a chemical continuous-gas-liquid plant, are separately presented.