Modeling of Multiproduct Batch Plants

This is the inverse of the resource requirement problem. The objective is to determine the production capability of an existing plant given a typical product mix and time horizon. Capacity analysis models must account for resource sharing among the processes of the various products, consider downtime for hofidays, equipment preventive maintenance, and changeover activities, and consider other constraints that limit production capacity. 

The above applications require plant models at different levels of detail. Long term capacity analysis requires the least detail in recipe representation. Typically, the recipe of a batch process is represented with a small number of activities occupying key equipment that is likely to limit production. Long term planning utilizes models with a detail similar to those of capacity analysis. Short term planning and scheduling require more detailed models that account for the ntihzation of all main equipment and the critical auxiliary equipment (i.e., those with high utilization that 

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The approaches and tools utilized for modeling and scheduling of multiproduct batch plants vary widely. A possible grouping of the approaches based on tools utilized follows ... 

It is evident from the foregoing description and diagrams shown in Fig. 1,7a, b that multipurpose batch chemical plants are more complex than multiproduct batch plants. This complexity is not only confined to operation of the plant, but also extends to mathematical formulations that describe multipurpose batch plants. Invariably, a mathematical formulation that describes multipurpose batch plants is also applicable to multiproduct batch plants. However, the opposite is not true. It is solely for this reason that most of the effort in the development of mathematical models for batch chemical plants should be aimed at multipurpose rather than multiproduct batch plants. 

I. E. (1997) A mixed-integer linear programming model for shortterm scheduling of single-stage multiproduct batch plants with parallel lines. Ind. Eng. 

The MINLP model for the retrofit design of a multiproduct batch plant takes the following form ... 

The short-term scheduling problem of a multiproduct batch plant with uncertain product demands is addressed in this article. The problem is modelled using a two-stage stochastic approach maximising the expected profit and integrating inventory costs and penalties for production shortfalls. Additionally, risk is controlled using a recently developed methodology. 

Cerda, J. Henning, G.P. and Grossmann, I.E., 1997, A Mixed - Integer Linear Programming Model for Short -Term Scheduling of Single Stage Multiproduct Batch Plants with Parallel Lines, Ind. Eng. Chem. Res., 36, 1695. 

Whatever the case of batch plants, either of multiproduct or multipurpose nature, few works have addressed the retrofit problem compared with the batch plant design problem. Most of the mathematical formulations used to model the retrofit problem usually lead to optimization-oriented problems. It must be also emphasized that scheduling is intrinsically associated with batch plant design/retrofit, and is part and parcel of the formulation of both issues. It can be considered as a sub-problem of the design/retrofit problem. As highlighted in the compared formulation of these companion problems, the retrofit problem appears to be a more constrained problem. Yet, the basic solution strategy involves the same mathematical approaches and tools. 

Previous chapters described modehng of individual operations, such as distillation, crystallization, filtration, etc. Batch process simulation combines multiple processing steps in order to model a complete batch process or even a multiproduct plant. 

BATCHES and Aspen Batch Process Developer can be used to model multiple batches of multiple products. However, they take a long time to generate solutions because they do detailed material and energy balances for all the simulated batches. Furthermore, these tools cannot easily accormt for equipment failures, delays, work shift patterns, downtime for equipment maintenance, holidays, etc. Consequently, they cannot be used for day-to-day scheduling of multiproduct plants. 

Batch production is considered by the first seven approaches shown in Table 4.2. Timpe and Kallrath (2000) propose a time-discrete MILP for the IPPSP with multiple production sites/plants, multiple production modes, intermediate storages, sales points, and transports between sites, storages, and sales points. The model uses different time scales for production and sales planning which allows a more precise planning of production. In a production period, a site can produce in different modes whereby changeover times and costs are considered. To store intermediate and raw materials, one-product and multiproduct tanks are available and an assignment of products to tanks is implemented. The... 

Batch process simulation is a computer modeling technique used for the design, analysis, and optimization of batch manufacturing processes. Batch process manufacturing is practiced in industries that produce low-volume, high-value products such as pharmaceuticals, fine chemicals, biochemicals, food, consumer products, etc. Most batch manufacturing facihties are multiproduct plants that produce a variety of products. 

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