Study On Polygeneration System CCS Life Cycle Assessment And System Integration

Stepping into 21st century, the climate problems due to greenhouse gas are paid more attention to. The research on sustainable energy power systems has been one of the most important directions, and its related critical science problems have also been the frontier and focus.Supported by the National Natural Science Foundation of China and National Key Projects Fund, based on coal-based polygeneration system of chemical production and power generation,the assessment methodology about carbon life cycle is investigated, which includes CO2 capture, transportation and storage (CCS) during energy utilization; the thermodynamic performance, CO2 abatement and economic performance of polygeneration system are comprehensively evaluated;a polygeneration system of methanol production and power generation with CO2 recovery based on coke oven gas and coal-gasified syngas is proposed;and CCS life cycle of coal-based synthetic fuel production via polygeneration system is analyzed from the viewpoints of thermodynamics and economics.Based on the second law of thermodynamics, the carbon life cycle during coal-based energy utilization is analyzed,and exergy penalty and cost of CO2 avoided in the life cycle are proposed as the criteria on CO2 avoided penalty. Firstly, through exergy balance analysis of the life cycle, the irreversibility of processes and the CO2 avoided exergy penalty are disclosed, and the total exergy penalty for CO2 avoided is analyzed.We can find that the main part of the exergy penalty in the life cycle is caused by the energy penalty of CO2 capture. Secondly, by analyzing the cost penalty for CO2 avoided in the life cycle, the main reason for cost penalty is found to be the energy penalty of CO2 capture.As a result, it is critical to reduce the energy penalty for cost penalty decrement. Lastly, based on the cost penalty analysis, the reduction potential of the cost penalty with technology development is analyzed with learning curve analysis.The economic performance of the coal-based polygeneration system of methanol and power production is analysis. Comprehensive considering the thermodynamic performance, the cost saving and cost penalty for CO2 avoidance are analyzed.Through system integration, the polygeneration system can achieve about 10% installed capital cost saving and 13% primary energy saving.Trading off both of the two results, the polygeneration system can achieve about 12% cost saving, in which,the improvement of thermodynamics performance plays an important role.Simultaneously, due to lower energy penalty, the polygeneration system can realize near zero economic penalty for CO2 avoidance. In addition, the learning curve analysis shows that the learning rate of CO2 avoided cost in polygeneration system is about 30%,which shows that the polygeneration system has much broader prospects.Based on the principle of integration between the clean fuel production and CO2 separation, a new polygeneration system of methanol and power production is proposed according to the characteristics of energy level and the syngas composition of coke oven gas and coal-based synthetic gas. In this system, the utilization of higher temperature sensible thermal energy of the coal-based syngas is integrated with the partial methane-steam reforming, through which, the exergy destruction of the reforming process is mostly reduced,and the cascade utilization of chemical energy and syngas component reasonable transformation is achieved.Through capturing CO2 after methanol integration with lower energy consumption,it achieves integration between clean energy production and CO2 separation.Furthermore, the characteristics law of thermodynamic performance of the system is expressed via exergy balance analysis and graphic exergy analysis method.The results show that the polygeneration system can realize 70% CO2 avoidance and also achieve more than 5% energy saving compared with the single-product systems, including IGCC system and coal-based methanol single-product system,which realized energy and environment coordination.The CCS life cycle of synthetic fuel production via the coal-based polygeneration system is analyzed from the viewpoint of thermodynamics and economics.Compared with the life cycle of traditional coal-based methanol production, in the polygeneration system life cycle, both of the exergy consumption and cost of methanol production can save 10%,and CO2 emission can be avoided 60～70%.With learning curve analysis, the polygeneration system can achieve the methanol cost learning rate 11%.Furthermore, compared with the life cycle of crude oil-based vehicle fuel production, the methanol production by polygeneration system shows its advantages on CO2 control and economic performance.These results show that it is strategically significant to utilize efficient and economical synthetic fuel production system,which can ease vehicle fuel shortage, reduce the environmental pressure during energy utilization and decrease the dependence on crude oil import.