Energy, exergy and environmental (3E) analysis of the existing CHP system in a petrochemical plant

In this paper an existing combined heat and power (CHP) system in a Petrochemical Plant is analyzed in terms of energy, exergy and environmental (3E) aspects. The system includes steam generators, turbo-generators and a steam distribution network for steam consumers. The system was simulated using Cycle Tempo software. The simulation revealed that the energy, exergy, heat and total efficiencies are %8.22, %7.87, %48.92 and %56.8, respectively. Based on the results, the main exergy destruction is related to boilers, steam pressure reduction stations (HPS/MPS-MPS/LPS) and turbo-generators, respectively. Regarding the high temperature of the exhaust gases from the boilers, adding an economizer stage can increase the efficiency of the boiler and decrease the rate of CO2 production. In addition, the off-grid network of the studied petrochemical complex has also caused stumbling blocks. In order to increase the efficiency of the cycle, eliminating the exergy waste, and connecting to the nation-wide power network, it is recommended that a gas turbine and an HRSG be used instead of the boilers. This way, all the waste related to the boilers and pressure reduction stations will be minimized. Moreover, the risk of plant trip and the shut-down of all the process production lines will be solved.