A novel use of a computer simulator to design an industrial refrigeration system

Industrial refrigeration systems such as those present in an ethylene plant oran ammonia plant are designed based on the demand of refrigerant in the associated processes. 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 byusing feed-forward or feed-back controllers to determine required refrigerant flowrates and the resulting compressor capacities. This technique often results in many control loops, each requiring many iterations to converge. This paper describes a novel technique in which HYSIS, a process simulator is used to design a complex refrigeration system without resorting to numerous control and recycle loops. The same technique can be applied to the design of steam systemsin which specified amounts of steam at different pressure levels are demanded.These steam systems are often used for heating as well as providing power to compressors and pumps in a process plant.