Energy Network Integration And Life Cycle Assessment Of Coal Chemical Looping Combustion Power Plant

The problem of increasing CO₂ emissions from fossil-fueled power generation systems needs to be addressed.Chemical looping combustion（CLC）presents a very promising CO₂ reduction technology,which can beapplied to work towards a new near-zero emission power generation system.This study established and validated a model of 600 MW chemical looping combustion power plant with CO₂ capture,which is composed of four sub-systems,namely chemical looping combustion（CLC）,heat recovery steam generator（HRSG）,steam turbine power generation（ST）and CO₂ capture（CC）.Reactor temperature,mass ratio of oxygen carrier to coal and the circulation ratio of CO₂ were investigated to obtain optimal operating conditions and parameters of the chemical looping combustion power plant.The results show the optimal operation parameters are that,when the carbon capture rate is90%,the carbon dioxide cycle ratio is 0.65,the air reactor temperature is 1223 K,the fuel reactor temperature is 1157 K,and the mass ratio of oxygen carrier to coal is 55.The exergy efficiency of chemical looping combustion sub-system was 71.70%,CO₂ concentration in fuel reactor is nearly 100%,net power generation efficiency is 34.80%（HHV）.The heat exchange network wasdesigned and optimized using combined pinch and exergy analysis for matching and optimizing the different energy levels and heat recovery.It was concluded that when the minimum temperature difference is 10 K,the heat exchange network system is optimal.The total exergy loss of heat exchange network is 246.32 MW.The exergy analysis included the exergy destruction and distribution of the total plant.The exergy efficiency of the subsystems is 70.51%（CLC）,74.76%（ST）,86.69%（HRSG）and 95.46%（CC）,respectively.The techno-economic performance of the chemical looping combustion power plant has been evaluated.Results exhibit that the net energy efficiency of the chemical looping combustion power plant is 34.80%,which is 2.40%higher than the reference power plant（32.40%）with the same CO₂ capture ratio（90%）.The CLC power plant also provides a lower cost of electricity of 0.74 CNY（Chinese Yuan）/k Wh and less coal consumption with 381 g/k Wh,which are lower than that of the ethanolamine（MEA）-based power plant（0.86 CNY/k Wh and 408 g/k Wh）.Compared to the traditional ultra-supercritical coal power plants,the new power plant saved investment of 39.13%,the CO₂ emission reduced by 9.68%,the cost and energy penalty of CO₂ capture decreased by32.05%due to the intrinsic nature of in-suit CO₂ capture in CLC technology as well as the minimized exergy loss during the combustion process.The life cycle assessment of coal chemical looping combustion power plant including resource and energy consumption,environmental potential,life cycle cost and sustainable index of power plant also have been investigated.The evaluation results were compared to the four main clean coal power generation power plants:ultra-supercritical coal-fired power plant（USC）,ultra-supercritical coal-fired power plant with CCS（USC-CCS）,integrated gasification combined cycle power plant（IGCC）and integrated gasification combined cycle power plant with CCS（IGCC-CCS）.The weighted environmental impact potential of IGCC,USC-CCS,USC and IGCC-CCS are 29.49%,33.15%,33.49%and38.92%,all of which are higher than that of CLC（0.99 milliequivalent）,respectively.Energy payback ratio of CLC power plant were 12.73%,16.46%and 26.40%greater than those of IGCC,USC-CCS and IGCC-CCS power plants.The life cycle cost of CLC（0.987 g/k Wh）was 14.84%lower than USC-CCS power plant,and 4.15%lower than IGCC-CCS power plant.Sustainability of CLC power plant（SIPP=1.46）were 40.83%and 43.03%higher than those of USC-CCS and IGCC-CCS power plant.Results showed that coal chemical looping combustion power plant has obvious advantages in the aspects of environment protection,resource and energy consumption,as well as life cycle cost and sustainability compared to USC-CCS and IGCC-CCS power plants.