Mixed intermediate storage operational

The other operational philosophies that are generally encountered are the mixed intermediate storage (MIS), zero-wait (ZW), finite wait (FW) as well as the unlimited wait (UW) operational philosophies. The MIS philosophy is encountered in a situation where at least 2 of the aforementioned operating philosophies coexist in one process. It is indeed very seldom in most practical applications to have only one philosophy throughout the operation. A combination of different philosophies in often the case. 

These operational policies are not generally taken unilaterally they are generally mixed, which means that the aforementioned operating philosophies coexist in one process, leading to the mixed intermediate storage (MIS) strategy. These situations may correspond to the stable, unstable or stable in limited time namre of the intermediate product as illustrated in... 

If the reaction is to be performed in a continuous setting, two separate sets of equipment are required and must be operated simultaneously. Compositions are then obtained by mixing the necessary streams belonging to each structure in the appropriate proportions. By comparison, if it is desired to perform the same task under batch conditions, an identical outcome may be achieved by two serial operations together with intermediate storage of material used in mixing processes. Hence, it may turn out that a single set of reactive equipment is sufficient to achieve the same result. 

A non-periodic plant operating mode defined over a given time horizon is considered. Mixed storage policies, shared intermediated states, material recycles and multipurpose batch plant equipment units with continuous sizes, are allowed. 

Continuous mixing is the preferred option for processes where throughput is high, space is a constraint, storage of intermediates must be avoided, or the material has a tendency to segregate. A continuous mixer can be a low-cost and rehable option if the operating variables are appropriately controlled. Selection of batch versus continuous mixing has been discussed in Section 15-9. 

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