Production campaign

From diese various estimates, die total batch cycle time t(, is used in batch reactor design to determine die productivity of die reactor. Batch reactors are used in operations dial are small and when multiproducts are required. Pilot plant trials for sales samples in a new market development are carried out in batch reactors. Use of batch reactors can be seen in pharmaceutical, fine chemicals, biochemical, and dye industries. This is because multi-product, changeable demand often requues a single unit to be used in various production campaigns. However, batch reactors are seldom employed on an industrial scale for gas phase reactions. This is due to die limited quantity produced, aldiough batch reactors can be readily employed for kinetic studies of gas phase reactions. Figure 5-4 illustrates die performance equations for batch reactors. 

Subcase bl This case is encountered, for example, when batch records from different production campaigns are compared and the same number of samples was analyzed in each campaign. (Note under GMP, trend analysis has to be performed regularly to stop a process from slowly, over many batches, drifting into a situation where each parameter on its own is within specifications, but collectively there is the risk of sudden, global loss of control. Catastrophe theory has gained a foothold in physical and biological literature to describe such situations cf. Section 4.14.)... 

Rows 1-7, item Titr 0.5% subtracted typical of temporary change in the production process, calibration procedure, or analytical method, especially if values 1-7 were obtained in one production campaign or measurement run. 

Finally, in multipurpose plants compounds, which can be deposited in various places (e.g. corners, zones near sealings) in equipment, can contaminate products of the subsequent batch. Therefore, all equipment must be thoroughly cleaned before the next production campaign starts. Contaminants can be formed in the process, sometimes at ppm level, and be recycled with streams of solvents and/or reactants. Hence, the influence of recycling on process performance indices must be included in the program of laboratory studies, at least in their final stage. 

Intermediate storage de-couples the process into periodically operated subprocesses in the sense that each of the subprocesses can be operated with its own limiting cycle time and batch size. If the storage capacity is sufficiently large to accommodate the intermediate product of an entire production campaign, then the subprocesses can be operated completely independently. Alternatively, the storage capacity can be selected so that it de-couples the... 

Single-product campaigns. When solving Eqn. 7.4-31 the following time constraint must be taken into account for overlapping operation ... 

The criterion for optimal design is the same as that for single-product campaigns. The horizon constraint (7.4-34) is reformulated in that the cycle times are defined differently. Assuming UIS policy, this constraint for mixed-product campaigns is given by ... 

Approximate equipment sizing. There are many combinations of equipment units that meet the requirements concerning the functions of all equipment units and the time horizons for all products. Based on the Flatz (1980) concept, a simple procedure is presented to determine feasible equipment sizes that meet all requirements for plants operated in a single-product campaign mode (no process overlapping). The procedure is illustrated in Fig. 7.4-10. 

Long production campaigns are involved and limiting cycle times are used as reasonable approximations of reality. 

The total production time for single production campaigns is given by ... 

Optimal schedules are given in Table 7.4-20. Clearly, for cleaning times of five hours, single-product campaigns are the best solution of the scheduling problem, while for zero cleaning times (theoretical case) mixed-product campaigns would be best. 

An alternative production schedule can be suggested by following a mixed-product campaign, as illustrated in Figure 14.18b. Alternating between batches of Product 1 and Product 2 in Figure 14.14b allows the cycle time to be reduced to 45 h and the makespan to be reduced to 51 h. 

Figure 14.18 Single versus mixed-product campaigns for three batches each of two products.

The following process is proposed for the production of Product C. For the scheduling of the production campaign, overlapping is allowed and a zero-wait transfer is applied for storage policy. The process is represented in Figure 14.28. 

After the total amounts of production for each product have been determined, these amounts are split in the second step into an optimal number of production campaigns for each product according to the relevant constraints and cost. 

The main focus of the optimization process in PP/DS is the determination of production campaigns. On the basis of the results determined in SNP optimization, a detailed schedule which considers additional resources and products is created. This schedule is fully executable and there is no need for manual planner intervention, even though manual replanning and adjustments are fully supported within the PP/DS module. An executable plan can only be ensured by considering additional complex constraints in PP/DS optimization. These additional constraints include ... 

Campaign processes have also variable production time. Different to continuous production, campaign production is related to multi-purpose assets, where different processes and products can run on the same production resource and change-over decisions between campaigns need to be taken. Finally, batch processes have a defined lot size, start and end time of production as well as throughput. 

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