Process intermediate storage operational philosophy

Process Intermediate Storage Operational Philosophy The New Operational Philosophy... 

Chapter 3 presents a synthesis technique for multipurpose batch plants and further introduces an unexplored operational philosophy so called Process Intermediate Storage (PIS) operational philosophy. 

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 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. 

The ZW, FW, and UW are in most instances a consequence of product stability. In a situation where the intermediates are unstable, it is always advisable to proceed with the subsequent step(s) in the recipe as soon as the intermediates are formed, hence the ZW operational philosophy. Due to its nature, ZW does not require any dedicated storage for the intermediates and could be depicted by a flowsheet similar to that shown in Fig. 1.3. On the other hand, the intermediate could be partially stable and only commence decomposition after a certain period. In this case storage time has to be finite in order to prevent formation of unwanted material, hence the FW operational philosophy. The UW operational philosophy is applicable whenever the intermediates are stable over a significantly longer time than the time horizon of interest. In both FW and UW operational philosophies, storage of intermediates can either be within the processing equipment or dedicated storage unit. 

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... 

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