Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Batch Scheduling Problems

Single Parallel Multiproduct Multipurpose (flow-shop) (job-shop) [Pg.165]

2 Classification of Batch Scheduling Problems 165 (1) Process topology [Pg.165]

Dedicated Shared storage units storage units [Pg.165]

Another important aspect of process flow requirements is reflected in inventory policies. These often involve finite and dedicated storage, although frequent cases include shared tanks as well as zero-wait, non-intermediate and unlimited storage policies. Material transfer is often assumed to be instantaneous, but in some cases such as in pipeless plants delay is significant and must be accounted for. [Pg.166]

Perhaps a major factor is the handling of batches. For instance, pharmaceutical plants usually handle fixed sizes for which integrity must be maintained (no mix-ing/splitting), while solvent or polymer plants handle variable sizes that can be split and mixed. Similarly, different requirements on processing times can be found in different industries depending on process characteristics. For example pharmaceutical applications might involve fixed times due to FDA regulations, while solvents or polymers have times that can be adjusted and optimized with process models. [Pg.166]


Having presented the general features of typical batch scheduling problems we introduce a roadmap that describes the main features of current optimization... [Pg.166]

In addition to the time representation and material balances, scheduling models are based on different concepts or basic ideas that arrange the events of the schedule over time with the main purpose of guaranteeing that the maximum capacity of the shared resources is never exceeded. As can be seen in Figure 8.5 and Table 8.1, we classified these concepts into five different types of event representations, which have been broadly utilized to develop a variety of mathematical formulations for the batch scheduling problem. Although some event representations are more... [Pg.168]

A simpler and general discrete time scheduling formulation can also be derived by means of the Resource Task Network concept proposed by Pantelides [10], The major advantage of the RTN formulation over the STN counterpart arises in some problems involving many identical pieces of equipment. In these cases, the RTN formulation introduces a single binary variable instead of the multiple variables used by the STN model. The RTN-based model also covers all the features at the column on discrete time in Table 8.1. In order to deal with different types of resources in a uniform way, this approach requires only three different classes of constraints in terms ofthree types of variables defining the task allocation, the batch size, and the resource availability. Briefly, this model reduces the batch scheduling problem to a simple resource balance problem carried out in each predefined time period. [Pg.173]

In most chemical batch scheduling problems the underlying data is not exactly known at the time the schedule has to be generated. Typical sources of uncertainties are (1) failures of reactors, equipment, and resources, (2) varying processing times, (3) varying product qualities, and (4) varying customer s demands. [Pg.185]

This algorithm has been successfully applied to chemical batch scheduling problems [13-17]. [Pg.200]

Consider the batch scheduling problem that is given through the STN shown in Figure 11.10, which is an extension of the work by Papageorgiou and Pantelides (1996). [Pg.317]

From the STN representation, we can go to a mathematical formulation of the batch scheduling problem. This class of optimization models is called mixed-integer linear programs (MILPs). [Pg.518]

In addition to the elimination of partial solutions on the basis of their lower-bound values, we can provide two mechanisms that operate directly on pairs of partial solutions. These two mechanisms are based on dominance and equivalence conditions. The utility of these conditions comes from the fact that we need not have found a feasible solution to use them, and that the lower-bound values of the eliminated solutions do not have to be higher than the objective function value of the optimal solution. This is particularly important in scheduling problems where one may have a large number of equivalent schedules due to the use of equipment with identical processing characteristics, and many batches with equivalent demands on the available resources. [Pg.282]

In addition to their ability to capture the multidimensionality of batch operations, another advantage of mathematical programming techniques is the flexibility and adaptability of the performance index, i.e. the objective function. In a design problem, the objective function can take a form of a capital cost investment function. In a scheduling problem it can be minimization of makespan, maximization of throughput, maximization of revenue, etc. In this chapter, the objective function will either... [Pg.84]

A natural progression from the scheduling of zero effluent operations is the derivation of a formulation that synthesises batch plants operating in the zero effluent mode of operation. The problem to be solved is slightly different to the general scheduling problem addressed in the formulation presented previously. [Pg.187]

During normal operation of the copper plant, there are a number of regular maintenance jobs that need to be planned. They are included in the scheduling problem as additional jobs that have given release dates and due dates. These maintenance jobs can mostly be performed only when a unit is empty and not in use. The optimization approach finds the best location for each maintenance job with the least impact on production throughput and, furthermore, modifies the batch recipes such that there will be a suitable break in the operation for the equipment that must be maintained. [Pg.104]

The real-word case study considered here is the production of expandable polystyrene (EPS). Ten types of EPS are produced according to ten different recipes on a multiproduct plant which is essentially operated in batch mode. In this section, the multiproduct plant, the production process and the scheduling problem are presented. [Pg.138]

The scheduling problem is complicated by the fact that the coupled production of grain size fractions and the mixing in the finishing lines prohibit a fixed assignment of recipes to products. Furthermore, there is neither a fixed assignment of storage tanks nor of polymerization reactors to batch processes. [Pg.141]

It is the objective of this paper to provide a comprehensive review of the state-of-the art of short-term batch scheduling. Our aim is to provide answers to the questions posed in the above paragraph. The paper is organized as follows. We first present a classification for scheduling problems of batch processes, as well as of the features that characterize the optimization models for scheduling. We then discuss representative MILP optimization approaches for general network and sequential batch plants, focusing on discrete and continuous-time models. Computational... [Pg.163]

Having introduced a general road map for classifying problems and models for batch scheduling we present a brief review on the specific models that have been proposed in the literature (for model details see Mendez et al. [6]). ... [Pg.172]


See other pages where Batch Scheduling Problems is mentioned: [Pg.30]    [Pg.271]    [Pg.98]    [Pg.137]    [Pg.164]    [Pg.181]    [Pg.344]    [Pg.15]    [Pg.256]    [Pg.474]    [Pg.474]    [Pg.9]    [Pg.181]    [Pg.183]    [Pg.183]    [Pg.196]    [Pg.30]    [Pg.271]    [Pg.98]    [Pg.137]    [Pg.164]    [Pg.181]    [Pg.344]    [Pg.15]    [Pg.256]    [Pg.474]    [Pg.474]    [Pg.9]    [Pg.181]    [Pg.183]    [Pg.183]    [Pg.196]    [Pg.162]    [Pg.272]    [Pg.280]    [Pg.287]    [Pg.316]    [Pg.511]    [Pg.11]    [Pg.98]    [Pg.103]    [Pg.142]    [Pg.142]    [Pg.144]    [Pg.159]    [Pg.163]    [Pg.165]    [Pg.168]    [Pg.169]    [Pg.171]   


SEARCH



Batch scheduling

Scheduling problem

© 2024 chempedia.info