Energy, exergy, economic and environmental (4E) analysis of an integrated process combining CO2 capture and storage, an organic Rankine cycle and an absorption refrigeration cycle

In order to reduce the cost of CO2 capture and storage, and promote the application of this technology in the coal chemical industry, we propose an integrated process combining an organic Rankine cycle, an absorption refrigeration cycle, and the purification of syngas from coal. Its purpose is to make efficient use of the waste heat produced in the manufacture of natural gas from coal, converting it into available energy, such as electric energy and cold energy, so as to save energy and reduce emissions. At the same time, the integration process can effectively improve the efficiency of energy use. Based on an accurate model, a simulation of the entire process is established, and the process is then analyzed from the aspects of energy, exergy, economy, and the environment. The thermal efficiency of the organic Rankine cycle, and the coefficient of performance of the absorption refrigeration cycle, are 0.148 and 0.1058, respectively. The result of an exergy analysis shows that the exergy efficiency of the waste heat utilization system is 42.88%. The integration process can greatly reduce the operational cost of CO2 capture and storage, making it 81% lower than that of the basic process. The results of a life-cycle assessment show that the integration process has good environmental benefits, with a total equivalent CO2 emission of 2.03 kg CO2-eq/t. The integration process is of great significance for CO2 capture and storage in the coal chemical industry, and for the optimization and improvement of other processes by making use of low grade waste heat.