SELECTION OF OPTIMAL VOC-CONDENSATION SYSTEMS

With increasingly stringent environmental regulations governing plant emissions of volatile organic compounds (VOCs,'' there is a growing need for robust procedures for the design of optimal VOC recovery processes. One of the more recently incorporated VOC recovery techniques is condensation. VOC-condensation processes use liquid refrigerants to reduce the temperature of the emission stream(s) to the level necessary for the VOC to condense out of the stream(s). This paper presents a three-stage technique for synthesizing refrigeration systems for VOC-condensation processes. The first stage introduces the novel concepts of stacked-temperature diagram (STD) and minimum utility stacked-temperature diagram (MUSTD). These concepts are coupled with a linear optimization, program to develop the refrigeration network for VOC condensation that results in the minimum operating cost. The second stage minimizes the fixed cost of the refrigeration network by allowing the determination of the minimum number of refrigeration units that can realize the minimum operating cost solution found in stage one. The third stage allows the design of the minimum-annualized cost network (MACNET) by examining tradeoffs between operating and fixed cost. This three-stage approach allows the design of a refrigeration network for VOC-condensation processes that results in the minimum annualized cost to the company. A case study is solved to indicate the benefits of the three-stage design procedure.