Design an Industrial Refrigeration System A Novel Use of HYSYS by K. Hing Pang California Polytechnic University, Pomona

Industrial refrigeration systems such as those present in an ethylene plant or an ammonia plant are designed based on the demand of refrigerant in the process. Once the duties of the heat exchangers and the temperatures of the refrigerant are specified, the refrigeration system consisting of compressors, condensers and flash drums can be designed. Process simulators such as Provision or Aspen can be used to design the refrigeration system by using feed-forward or feed-back controllers to determine required refrigerant flow rates and the resulting compressor capacities. This technique often results in many control loops, each requiring many iterations to converge. This paper is the result of a senior project (1) undertaken by a chemical engineering senior at Cal Poly, Pomona. It describes how HYSYS has been used successfully to design a refrigeration system with 4 compressors, 13 heat exchangers and 4 flash drums without resorting to numerous control and recycle loops. The intent of this paper is not to provide a rigorous comparison between simulators, but to focus on a special technique used for solving industrial refrigeration design problems. It is expected that the same technique can be applied to other utility systems.

What is an industrial refrigeration system?

An ethylene manufacturing process usually consists of a hot section and a cold section. The primary equipment in the hot section is the pyrolysis furnace in which hydrocarbons are cracked at temperatures in excess of 1000o F to form ethylene and a slate of byproducts including methane, ethane, propylene, C4’s and C5 and heavier hydrocarbons. The cold section consists of a series of distillation columns, flash drums and exchangers which separate pure ethylene from the byproducts. The cold section operates under cryogenic conditions with temperatures ranging from -160o F to -25o F. Refrigerants, usually ethylene and/or propylene of several temperature levels, are used as coolants in exchangers and condensers.............