Batch processes conceptual design

The goal of a conceptual design for a continuous process is to select the process units and the interconnections between these units, identify the dominant design variables and estimate the optimum design conditions, and identify the process alternatives and find the best four or so alternatives. For batch processes, we must also decide which units should be batch and which should be continuous, whether or not some process operations should be carried out in the same process unit or separate units, whether or not parallel units should be used, and how much intermediate storage is required. Thus, batch processes require more decisions to fix the structure of the flowsheet (there are more alternatives to consider). Since there are many situations in which it must be decided whether to develop a batch or a continuous process, both procedures should be present in a general conceptual design code, whereas the current trend is to develop separate codes for batch processes. 

With the exception of combustion technology the data base is far from this ideal prospective processes range in development status from conceptual designs through 10 gram batch process scale to 20 tpd process development or demonstration units. 

A conceptual design for a demonstration base-hydrolysis/hydrothermal processing unit would consist of two 210-L batch reactors for hydrolysis treatment followed by a 38-L/hr continuous hydrothermal processing unit. The unit is sized to treat an excess HE stream from Pantex of 36 kg/day. 

As aforementioned, the market demand for products manufactured through batch processes is usually variable. At the stage of conceptual design of a batch plant, it is almost impossible to obtain precise information on the future product demand over the lifetime of the plant. However, decisions must be made on the plant capacity. For this reason, design is generally performed with product portfolio and production scheme that are representative of the future product list, but it must be highlighted that the operated plant will probably have to be managed with other product candidates. The capacity of the plant should be able... 

Since the retrofit problem can be viewed as a particular case of the design problem with specific constraints that capture the existing situation of the plant, the conceptual batch process retrofit problem proposed by Reklaitis (1989) can be decomposed into four decision levels. 

Flowsheets for processes are sometimes generated without following the hierarchy of properties described previously. As an example, Siirola [20] proposed a reactive-distiUation solution to make methyl acetate. Unit operations that combine the property differences present abrupt departures from common methodologies. With the advent of various pieces of equipment, such as differential side-stream feed reactors (i.e., semicontinuously fed batch reactors), continuous evaporator-reactors (e.g., wiped-film evaporators), and reactive distillation columns, one can consider these unit operations in the development of conceptual designs. As an example, Doherty and Malone [21] have presented systematic methods for reactive distillation design. 

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