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Organic Rankine Cycle for Waste Heat Recovery in a Refinery

Chen, Cheng-Liang, Li, Po-Yi, Le, Si Nguyen Tien
Industrial & Engineering Chemistry Research 2016 v.55 no.12 pp. 3262-3275
boiling point, case studies, chemistry, economic analysis, furnaces, heat recovery, industrial wastes, mathematical models, oils, pipes, power plants, sulfides
Waste heat recovery is one of the most important development fields for the organic Rankine cycle (ORC), where a low boiling point organic fluid is used as a working medium. The ORC can be applied to heat and power plants or to industrial and farming processes. Some heat sources, like hot exhausts from furnaces, which contain particles or sulfide might harm pipes of an evaporator. It is suggested to introduce water or heat transfer oil as an intermediate medium for aiming at recovery of waste heat. In this paper, a mathematical model is represented for integrating ORC with the heat transfer fluid circulated as an intermediate fluid for recovering waste heat from the background process. An ORC-integrated superstructure considering all possible matches of heat-exchange between waste hot process streams, circulating heat transfer fluid, and ORC is proposed. The superstructure also takes into account the possibilities of several sets of ORC and circulating heat transfer fluid. Based on this superstructure, the model is designed and formulated as a mixed-integer nonlinear programming (MINLP) problem. A high-level modeling system, General Algebraic Modeling System (GAMS) is employed for the sake of solving this MINLP model. A case study of crude preheat train is investigated to demonstrate the novel application of the proposed model for industrial waste heat recovery. Economic analysis shows less than two payback years for the installation of ORC on a typical crude preheat train for waste heat recovery.