Saving Energy by Exergetic Analysis of MTP Process Refrigeration System

The exergetic analysis is a tool that has been used successfully in many studies aiming a more rational energy consumption to reduce the cost of processes. With this analysis, it is possible to perform an evaluation of the overall process, locating and quantifying the degradation of exergy. This paper applies exergy approach for analyzing the heat exchanger network design and refrigeration of MTP process. For this purpose, the behavior of some industrial processes and refrigeration cycle with propylene refrigerant has been investigated by exergy method. The equations of exergy destruction and exergetic efficiency for main components such as compressors, heat exchangers and expansion valves were studied. A specified section of propylene recovery unit with its refrigeration cycle has been simulated to perform the exergy analysis. Adding a new valve with optimum pressure drop according to process constraints and an expander results in high performance of multistream heat exchanger, saving cold utility consumption, using excess heat of the process section, and low required compression power (in the refrigeration section) which are the most important characteristics of the proposed configuration. Results show that the annual profit reaches 4.3 %.