Study Of The Application Of Liquefied Coalbed Methane By Pressure Swing Adsorption With Pressure Energy Recovery

In order to improve the utilization rate of energy in pressure swing adsorption process, this paper researched the applications of liquefied coalbed methane by pressure swing adsorption with pressure energy recovery technology. The pressure energy recovery system was designed and simulated by the process simulation software of Aspen Hysys. The turbine, which was the critical equipment of pressure energy recovery system, was designed and calculated. Finally, the economy of the pressure energy recovery system was analyzed. The main research contents are as follows:1. The method of pressure energy recovery was proposed. The relief valve was replaced by the expansion machine to recovery the pressure energy of the top gas. This paper discussed to conversion of the recovery pressure energy into shaft power and cold energy. The shaft power could be used for power generation and coaxially driving booster. And the cold energy could be used for the feed gas pre-cooling, which could reduce the cooling capacity required for liquefied cryogenic.2. The pressure energy recovery system was simulated by the process simulation software of Aspen Hysys. The performance was compared between the old system and the pressure energy recovery system. Results showed that the pressure energy recovery method could effectively reduce the power consumption of the system. Total power consumption of compressor could be reduced by 50%. Consumption of cooling water was reduced by 40% and the unit power consumption of liquefaction was reduced 7%.3. The impacts of the intake air quantity, adsorption pressure, expansion pressure and the content of nitrogen on the performance of pressure energy recovery system were studied. Results indicated that the increase of intake air quantity and expansion pressure led to a rise of total compressor power consumption. The rise of adsorption pressure and the content of nitrogen would reduce the total compressor power consumption, unit product liquefaction power consumption, pre cooling temperature and heat exchange area. The unit power consumption of the liquefaction increased with the rise of expansion pressure.4. The type of expansion machine was selected and the thermodynamic parameter of expansion machine was calculated according to the simulation results and technical requirements. The calculation results showed that the isentropic efficiency of turbine was up to 86.16%, which met the requirement of pressure energy recovery. The calculated and simulated shaft powers were 39.8kW and 38.23 kW respectively, which led to a relative error of 3.9%.5. The economic evaluation of pressure energy recovery system was analyzed. Results showed that if the operating rate per year was 94%, the power generation of 1,910,000 kW·h, refrigerating capacity of 1,990,000 kW and net annual earning of 1,144,500 yuan could be obtained, which could save standard coal quantity for 638.0 t/a and reduce emission of CO2, SO2, and NOx for 1658.8 t/a, 9.8 t/a, and 4.6 t/a respectively. And the payback period is about 3.08 years.