Process intermediate storage operational

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. 

Whether parallel operations, larger or smaller items of equipment, and intermediate storage should be used can only be judged on the basis of economic tradeoffs. However, this is still not the complete picture as far as the batch process tradeoffs are concerned. So far the batch size has not been varied. Batch size can be varied as a function of cycle time. Overall, the variables are... 

Batch processes can be synthesized by first synthesizing a continuous process and then converting it to batch operation. A Gantt (time-event) diagram can be used to identify the scope for improved equipment utilization and the need for intermediate storage. 

Minimize or eliminate in-process inventory of hazardous material, including inventory in the processing equipment as well as in tanks. Elimination of intermediate storage tanks will likely require improvements in the reliability of the upstream and downstream operations. 

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... 

Intermediate storage tanks will normally be needed to smooth out fluctuations in column operation and process upsets. These tanks should be sized to give sufficient hold-up time for smooth operation and control. The hold-up time required will depend on the nature of the process and on how critical the operation is some typical values for distillation processes are given below ... 

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. 

In addition to the primary processes, the following secondary processes are present in all three companies maintenance, quality and logistics. These processes together with the primary process constitute the operational process, where the initial data for this study was collected. The maintenance process performs scheduled and unscheduled maintenance activities at the different technical installations. The quality process takes samples at different points in the primary process to check the intermediate or final product according to product specifications. The logistic process takes care of the material flow and storage of materials. 

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