Multipurpose Batch Research Articles

Design, synthesis and scheduling of multipurpose batch plants via an effective continuous-time formulation

Design, synthesis and scheduling issues are considered simultaneously for multipurpose batch plants. An earlier proposed continuous-time formulation for scheduling is extended to incorporate design and synthesis. Processing recipes are represented by the State-Task Network (STN). The superstructure of all possible plant designs is constructed according to the potential availability of all processing/storage units. The proposed model takes into account the trade-offs between capital costs, revenues and operational flexibility. Computational studies are presented to illustrate the effectiveness of the proposed formulation. Both linear and nonlinear models are included, resulting in MILP and mixed-integer nonlinear programming (MINLP) problems, respectively. The MILP problems are solved using a branch and bound method. Globally optimal solutions are obtained for the nonconvex MINLP problems based on a key property that arises due to the special structure of the resulting models. Comparisons with earlier approaches are also presented.

An Improved RTN Continuous-Time Formulation for the Short-term Scheduling of Multipurpose Batch Plants

This paper presents an improved general mathematical programming formulation for optimal scheduling of batch processes based on the resource−task network (RTN) representation. The formulation uses a continuous-time representation and results in a mixed integer linear programming problem. It is a relaxation of the problem presented by Schilling (Schilling, G. Optimal Scheduling of Multipurpose Plants. Ph.D. Thesis, University of London, London, U., K., 1997). By allowing, if possible, finite storage within the processing tasks resource equipments of the involved raw materials and/or products, the proposed approach leads to simpler and less degenerate mathematical models. These models can be solved in significantly less CPU time, when compared to other RTN continuous-time formulations. Three published example problems are presented to illustrate the effectiveness of the proposed formulation. Finally, we show that the STN-based continuous-time scheduling formulation of Ierapetritou and Floudas (Ierapetritou,...

Primat der Chemie – Produktion in Mehrzweck-Batch-Anlagen

Multipurpose batch technology suits the thermodynamic prejudice of the organic chemist's understanding of chemical processes when he is faced with the challenge of scale-up. He is convinced that the kinetic aspects of the process can be mastered with a standardized approach. This concept allows the development of a scaleable process with reasonable effort to the point that makes the production of the first few kilograms of a new chemical entity feasible. This aspect is of paramount importance in the production of pharmaceutical fine chemicals when availability of the required amounts for clinical trials is the key factor to success. Furthermore such a process usually makes commercial production of ton quantities economical with acceptable costs.The number of available process technologies for the production of organic fine chemicals in ton quantities is limited. The driving factors are not only the time and resources needed for process development but also future production costs. Any cost savings in future production must give an acceptable return on the investment of process development. A multi-step synthesis requires a range of diverse production technologies with differences in yield over time and volume. Development of continuous processes in dedicated plants is rarely an alternative to batch technology. Furthermore at the time when process development for a dedicated plant should start, reliable information on required future quantities is not available.Objective of any process development is therefore the diligent use of the advantages of batch technology. This demands not only the knowledge of the pitfalls of this approach but also the flexibility to consider alternatives where required.

Retrofit design of multipurpose batch plants with multiple production routes

This work analyzes possible alterations of configuration of an existing multipurpose batch plant for which new production targets and selling profits have been specified. New equipment can be added to the batch plant in the form of a retrofit in order to become a more economical and optimal design. The retrofit problem is posed as a mixed-integer formulation (MILP). The application of the proposed model is illustrated using three examples where can be verified that the method is efficient and of easy application, when compared of the others strategies to solve the retrofit problem.

Planejamento e programação da produção em plantas multipropósito operando em batelada na indústria química

Neste artigo, considera-se o problema de programação da produção a curto prazo em plantas químicas multipropósito operando em batelada, em que a produção da planta é determinada pela demanda a ser atendida. Nesta situação, a capacidade da planta não está bem definida porque depende do mix de produção. Propõe-se uma fase de planejamento que tem como objetivo a determinação do número de bateladas de cada tarefa necessárias para atender a produção, bem como a respectiva janela de tempo de processamento. Estas janelas permitem a análise do carregamento dos processadores e da factibilidade do plano, ou seja, o atendimento das datas de entrega, através de ferramentas desenvolvidas na área de Busca Orientada por Restrições. Esta análise é feita para uma atribuição fixa de tarefas a processadores introduzida pelo usuário. O sistema fornece informações para orientar o usuário na criação de diferentes cenários de atribuição. O resultado da fase de planejamento é formado por um conjunto de janelas de processamento que diminuem sensivelmente a dimensão do problema de programação da produção, como é discutido para duas abordagens: programação mista (Mixed Integer Linear Programming - MILP) e Simulated Annealing.

Identification of aggregate resource and job set characteristics for predicting job set makespan in batch process industries

We study multipurpose batch process industries with no-wait restrictions, overlapping processing steps, and parallel resources. To achieve high utilization and reliable lead times, the master planner needs to be able to accurately and quickly estimate the makespan of a job set. Because constructing a schedule is time consuming, and production plans may change frequently, estimates must be based on aggregate characteristics of the job set. To estimate the makespan of a complex set of jobs, we introduce the concept of job interaction. Using statistical analysis, we show that a limited number of characteristics of the job set and the available resources can explain most of the variability in the job interaction.

Scheduling multipurpose batch process industries with no-wait restrictions by simulated annealing

Scheduling problems in multipurpose batch process industries are very hard to solve because of the job shop like processing structure in combination with rigid technical constraints, such as no-wait restrictions. This paper shows that scheduling problems in this type of industry may be characterized as multiprocessor no-wait job shop problems with overlapping operations. A simulated annealing algorithm is proposed that obtains near-optimal solutions with respect to makespan. This paper shows that the no-wait restrictions require several adaptations of the neighborhood structure used by simulated annealing. The performance of the algorithm is evaluated by scheduling industrial instances from a multipurpose batch plant in the pharmaceutical industry. Our results indicate that simulated annealing consistently gives better results for a number of realistic instances than simple heuristics within acceptable computation time.

Short-term planning and scheduling in multipurpose batch chemical plants: a multi-level approach

This paper deals with short-term planning/scheduling problems when the product demands are driven by customer orders. This type of problem is, in general difficult to be solved, once the orders are subject to changes in short periods. In this paper is proposed a multi-level decomposition procedure, containing at least two levels. At the planning level, demands are adjusted, a raw material delivery plan is defined and a capacity analysis is performed. Therefore, time windows for each operation are defined. At the scheduling level, an MILP model is developed. In order to reduce scheduling problem dimension, it is performed an analysis of equipment contention profile, enabling to model only situations where a decision variable is requested.

An investigation on integration of aggregate production planning, master production scheduling and short-term production scheudling of batch process operations through a common data model

A prototype system has been developed by integrating two higher-level hierarchical production planning application programs (aggregate production plan (APP), master production schedule (MPS)) using a common data model integration approach into an existing planning system for short-term scheduling and supervisory batch management which was originally proposed and developed by Richard, J. G., Macchietto, S. & Shah, N. (1999). Integrated decision support in flexible multipurpose plants. Computers & Chemical Engineering, 23, S539–S542. The hierarchical production planning system has been modelled and validated around an industrial scenario concerning multi-site, multipurpose batch process operations making household chemicals from start to transportation to regional warehouses. This preliminary work suggests that the idea of integrating software applications through a common data model, which was originally described by Stanley, G. M. (1994). The emerging trend towards knowledge-based frameworks for computer-integrated manufacturing. Advances in Instrumentation & Control, 49, 1121–1133 and further developed by Rickard, J. G., Macchietto, S. & Shah, N. (1999). Integrated decision support in flexible multipurpose plants. Computers & Chemical Engineering, 23, S539–S542 is feasible. However further research work, improvements and validations are required using varieties of industrial batch process operations and distribution problems to prove its viability.

Utilization of processing time windows to enhance planning and scheduling in short term multipurpose batch plants

The problem considered is short term scheduling in multipurpose batch plants when the main objective is adherence to due dates. The solution approach contemplates a two-phase procedure. The planning phase consists of processing time-windows for all the necessary batches to meet the products' demand. This information is extensively uses in the scheduling phase. Three approaches are considered in the last phase, a MILP formulation using uniform discrete time representation; constrained based search (CBS) and simulated annealing (SA). And assessment is made of these techniques in heavily constrained problems and how these approaches deal with equipment units sharing and constraints imposed by material balances and storage conditions. The advantages of the two-phase approach are shown in each case with illustrative examples.

Synthesis of safe operating procedure for multi-purpose batch processes using SMV

Symbolic model verifier (SMV), an automatic error finding system, is developed and applied to various chemical processing systems to test their safety and feasibility. In this paper, we adopted SMV to synthesize error-free operating schedules in multi-purpose batch processes. The strength of this method is to synthesize a feasible sequence and to verify its safety simultaneously. Here, we propose two algorithms. One is to find embedded errors in operating sequences such as violating intermediate storage tank policies and unavailability due to sudden operating condition changes or insufficient production recipes. The other is the completion time algorithm to make sure that a makespan and a final operating sequence are obtained without errors. The proposed algorithm identifies errors and finds a minimum makespan and an operating sequence. Computation tree logic (CTL) embedded in SMV is extensively used to describe the situation of unsafe conditions and time related conditions for the final makespan. As a result of applying the algorithms to multi-purpose chemical processes, this approach finds a makespan and error-free operating schedules successfully. This combined synthesis and verification method also reduces the computation time and verifies operating schedules efficiently compared with the previously published algorithms.

Scheduling of non-sequential multipurpose batch processes under finite intermediate storage policy

In this study, we present a mathematical model for optimal scheduling of non-sequential multipurpose batch processes under finite intermediate storage (FIS) policy. In non-sequential multipurpose batch processes, the production routes of products may be different from one another and may be in opposite direction. Consequently, in order to reduce idle time of units and to raise the efficiency of process, we have to make operation sequences of products in each unit different by considering the production route of each product. For the formulation of this problem, we represented the starting and finishing time of a task in each unit with two coordinates. One is based on products, and the other is based on operation sequences. Then, we matched the variables used in the two coordinates into one with binary variables and logical constraints. We formulated this problem as an MILP model. Compared with Jung, J. H., Lee, H., Yang, D. R. and Lee, I. (1994) [Completion times and optimal scheduling for serial multi-product processes with transfer and setup times in zero wait (ZW) policy. Computers & Chemical Engineering, 18(6), 537] and Kim, M. S., Jung, J. H. and Lee I. (1996) [Optimal scheduling of multiproduct batch processes for various intermediate storage policies. Industrial Engineering & Chemical Research, 27, 1840] who used an MINLP model for multiproduct scheduling problems, we su9ggest an MILP model, even though we handle sequence dependent setup times in multipurpose processes. Therefore, the proposed model can guarantee the optimality of the solutions. We applied this model to two examples to show the effectiveness of the model. The MILP solver we used to solve these problems is GAMS/ OSL and H/W is IBM RS/6000 (model 350).

Scheduling of the batch annealing process — deterministic case

This study addresses the short-term scheduling problem for the batch annealing process in the heat treatment of steel coils. Scheduling in the batch annealing process has the following objective: determine the optimal movement plan for satisfying high utilization of shared equipment (a crane, furnaces, and coolers) among parallel bases. This process is a multipurpose batch plant which may contain re-entrant flows in the batch annealing cycles and units in parallel, including sequence-dependent setup time and transfer time. A novel mixed-integer linear programming (MILP) model for the scheduling of the batch annealing process is proposed. For large size problems of the batch annealing process, a scheduling solution can be obtained by using a novel algorithm. Although this procedure does not guarantee optimality of the solution, the computational efficiency was improved and feasible solutions for large problems can be obtained in a reasonable CPU time. Application of the proposed model and algorithm is illustrated with several example problems including a problem that consists of 29 pieces of equipment and up to 24 bases.

A new strategy for temperature control of batch reactors: experimental application

In this paper, a new strategy for temperature control of multipurpose batch reactors using a cascaded model based control is presented. This strategy is based on the use of the thermal flux as the manipulated variable. At each sampling time, the master controller computes the thermal flux to be exchanged between the reactor content and the thermal fluid flowing inside the jacket. This information is then used to determine the right fluid and to evaluate the opening value of the control valve. For this purpose a physical modelling of the thermal system has been developed. Finally, the control valve opening degree is computed and applied to the plant.

Completion times algorithm and optimal scheduling of single line multi-purpose batch process

For study of engineering facts, generally the operation of batch plants was classified into two types. One is the operation of multi-product batch process which produce multiple products with the same processing paths, the other is that of multi-purpose batch process which produce multiple products through the different production routes ( Reklaitis, (1990)). Also, according to Voudouris (1996), the multi-purpose batch plants are divided into two categories, sequential plants and non-sequential batch plants. In this paper we develop the completion times algorithm of nonsequential multi-purpose batch plants which have one unit in each stage under UIS policy. We also propose an efficient scheduling method for those plants. The proposed scheduling method composed two step approaches. In the first step, modified-RAES heuristics for initial solution of multi-purpose batch process scheduling was developed. At the second step, we suggested the Modified Simulated Annealing (MSA) method with adjusting parameters of Simulated Annealing (SA) by Ku and Karimi (1991). To evaluate the performance and efficiency of this study, we have tested about 200 problems and could get the outperformed results.

Modeling the supervising control of a multipurpose batch plant operated by activity

The aim of this work is to present a model to represent the supervisory control structure organized by activities of an order driven multipurpose batch plant. In this control structure each activity of the plant has its own supervisory control and all of them are coordinated by a supervisory control structure at the level of orders. In this work we present a framework to represent the supervising control of an order driven multipurpose batch plant operated by activities. The framework is based on a strategy that uses Petri nets to describe and analyze the supervising control. This strategy permits to automate the modeling of the supervising control. Based on this framework we developed a supervising control support system (SCSS) of an order driven multipurpose batch plant operated by activities.

A retrofit design strategy for multipurpose batch plants

This study addresses the general problem of multipurpose batch plants retrofitting. A two-stage methodology, previously developed in our laboratory, is proposed to solve the retrofit problem in which the AD-HOC discrete-event simulator is used to evaluate the different batch plant configurations proposed, at an upper level, by a genetic algorithm. In this paper, we will present the different steps of the algorithm. Our approach will be illustrated by an example inspired by Fuchino et al. (1994), a problem proposed by Bernal-Haro et al. (1997) and, finally, an industrial size one involving 10 products and 9 stages.

Time windows for short term planning in multipurpose batch plants

A planning approach is presented for short term mode of operation in multipurpose batch plants. Planning output is given in the form of processing time windows for intermediate products. Time windows are established from the time profile demand of final products and raw materials availability plan input by the user. Equipment units capacity analysis is used to assure a feasible situation and an acceptable plant loading.

Modeling of the supervisory control system of a multipurpose batch plant

A supervisory control of a multipurpose batch plant supervises that the plant is operated according to the schedule of production orders set by the scheduling module. The supervisory control depends on the plant topology, which is not defined a priori but generated while scheduling the production orders. This requires that the supervisory control system be able to generate the control structure after the generation of plant topologies. In the first part of this work we present a framework to represent the supervisory control of an order driven multipurpose batch plant. The framework is based on a strategy that uses Petri nets to describe and analyze the supervisory control of a process. This strategy permits the automation of the modeling of the supervisory control. Based on this framework we developed a supervisory control support system (SCSS) of an order driven multipurpose batch plant. In the second part of this work we present a description of an object oriented analysis and design of this SCSS.

Mixed-Integer Linear Programming Model for Short-Term Scheduling of a Special Class of Multipurpose Batch Plants

In this paper, a mathematical formulation for the short-term scheduling of a sequential multipurpose batch plant is proposed. The scheduling problems of the multipurpose batch plants under a mixed product campaign (MPC) are addressed here. A mixed-integer linear programming (MILP) model is developed based on the time slot, which is used to determine the production sequence and the production path of each batch. In order to reduce the search space, we propose a heuristic method that relies on the use of preordering constraints. Application of the preordering constraints to the proposed MILP model reduced the computational time required by more than 40%. The proposed model is extended to sequential multipurpose batch plants with parallel units.