SYNTHESIS OF SEPARATION SYSTEM FLOWSHEETS

A hierarchical decision procedure for the synthesis of separation system flowsheets for vapor-organic liquid-aqueous liquid-solid mixtures is proposed. An expanded set of synthesis rules that can be used to obtain a first design is discussed, but the final goal of the procedure is to generate a complete list of separation alternatives (by changing the decisions) that when coupled with short-cut screening techniques, can be used to identify the best few process flowsheets. The procedure is based on a decomposition of the separation system synthesis problem by phase splitting into a vapor recovery system, a solid recovery system, and liquid separation systems. A general superstructure presented for these subsystems includes all of the common unit operations for petrochemical processes. The procedure focuses on the development of a complete flowsheet for the separation system: which separation system recycle loops (in contrast to reactor system recycle loops) are required as well as interactions among separation subsystems and those between the separation system and remainder of the process. An example presented illustrates the procedure, and the opportunities for pollution prevention at the source are noted.