No intermediate storage

In the analysis, synthesis and optimization of batch plants complexity arises from the various operational philosophies that are inherent in time dependent processes. In a situation where the intermediate is allowed to wait in the same unit from which it is produced until the next unit is available, the operational philosophy is commonly known as no intermediate storage (NIS) operational philosophy. This philosophy is depicted in Fig. 1.3. NIS operational philosophy is usually adopted if operational space is of essence, since intermediate storage tanks can occupy considerable area. 

The above mass balance constraints suffice for the case where there is no intermediate storage available for wastewater. The mass balance constraints necessary for the case where there is a central storage vessel available for wastewater are presented in the following section. 

The dispersion agents are produced in two stirred tank reactors with a capacity of two (Dl) and four (D2) batches along with two (Dl) and four (D2) storage tanks with a capacity of one batch each. The organic phase is produced in one out of two stirred tank reactors with a capacity of one organic phase batch each no intermediate storage is provided for the organic phase. 

No Intermediate Storage (NIS) the material is stable but no storage vessel is available. However, it may reside temporarily in the equipment unit, which has been used for the active section of the process. In that case, the process unit is used for storage which can be viewed as detrimental to process profitability. 

H3- Multiproduct campaign H4- No intermediate storage H5- No reuse of equipment except for the case of consecutive tasks H6- Processing time is a function of the batch size H7- Production demands are treated revenue. ... 

The so-called zero-wait transfer policy is used when a batch at any stage is immediately transferred to the next stage because there is no-intermediate storage vessel available or when it cannot be kept in the current vessel. This policy is extremely restrictive. The other extremum is the unlimited intermediate storage policy, where a batch can be stored without any capacity limit in a storage vessel. Finally, there is a transfer option called no-intermediate storage, which allows the batch to be kept inside the vessel. Normally, the zero-wait transfer reqnires the longest CT. In practice, plants normally have a mixtnre of the three transfer policies. 

The problem formulation considers a flexible flow line with alternative processing routes for each product. For each route and product an ordered set of stages is given that the product must visit. The product must be processed by at most one machine in each of such stages and it bypasses the other stages that are not in the route. This formulation also considers limited or no intermediate storage space between the stages. 

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