Process Simulation And Exergoeconomic Analysis For Chemical Looping Carbon Dioxide Capture And In-situ Reforming With Syngas Production

Mitigating the effects of global warming on ecosystems has become a pressing concern.Significantly lowering CO₂ levels in the atmosphere and its marine carbon reserves,as well as transitioning from a fossil to a low-carbon economy,are critical steps toward addressing this environmental challenge.Carbon dioxide capture and utilization（CCU）technologies are critical in reducing CO₂ emissions and mitigating climate change.Currently,CCU technologies face issues of independent capture and utilization,high energy consumption,and high cost.Due to its low cost and easy product separation,the chemical looping CO₂ capture and in-situ reforming process is considered to be an efficient technology for achieveing integrated CO₂ capture and utilization.However,the thermodynamic properties and cost formation mechanism of this process are not yet clarified,which has become one of the problems affecting its popularization and application.Therefore,based on the theory of the second law of thermodynamics,tech-economic evaluation,and exergoeconomic analysis,this paper builds a system process model,implements auto-thermal operation and heat integration optimization,investigates the source of system thermodynamic irreversibility,evaluates the system’s economic cost formation mechanism,analyzes the influence of the system’s internal component interaction on thermodynamics and economics,and serves as an important reference for the performance optimization of the chemical looping carbon dioxide capture and in-situ reforming process.When the molar ratio of CO₂:Fe₂O₃:CH₄ is maintained at 1:3.8:12.92～1:4.2:14.87,the chemical looping carbon dioxide capture and in-situ reforming process can achieve heat balance among three reactors,which would realize efficient auto-thermal operation.When the minimum molar ratio is used for the system operating condition,three different cases of heat integration for the splitting of streams based on the maximization of heat exchange are studied and compared after heat integration,where case 1 is for the splitting of syngas stream,case 2is for the splitting of methane and syngas streams and case 3 is for the splitting of the air stream.The result shows that case 1 has the highest saving potential of 92.62%.From conventional exergy analysis,by comparing to the base case,the total exergy destruction of three heat integration cases is reduced by 32.78%,32.80%,and 30.72%,respectively,which is derived from the reduction of exergy destructions from heat exchangers.Meanwhile,their exergy efficiency is increased by 4.03%,4.02%,and 3.75%,respectively.Compared with other heat integration cases,case 1 shows the best performance on energy-saving effect and effective energy utilization rate.The tech-economic evaluation shows that the investment cost of the reforming reactor under the base case accounts for the largest proportion.However,the total investment cost of the system increases after heat integration:case 1>case 2>case 3,and the maximum investment cost of the component become heat exchangers.Conventional exergoeconomic analysis indicates that the unit product exergy cost of the heat integration case system increases when compared to the base case.Moreover,the unit product exergy cost of case 3 is the smallest.According to the exergoeconomic factor,indicates that regardless of thermal integration,the cost associated with exergy destruction of the air reactor is always the component that has the greatest impact on the product exergy cost of the system.However,the component of investment cost has the greatest impact on the product exergy cost of the system,which will be converted from the reforming reactor to a methane heater and heat exchangers.Due to the fact that the sufficient heat exchange of the stream will increase the heat exchange areas,therefore,the investment cost of the heat exchangers are increased,which in turn affects the product exergy cost of the system.As indicated from advanced exergy analysis,the potential increase of exergy efficiency by improving the components is greater than by the interaction between components in all heat integration cases,where case 3>case 2>case 1.When the components are improved,case 1 and case 2 should give priority to the air reactor,reforming reactor,and heat exchanger（CHAI）,while case 3 should give priority to the reforming reactor,air reactor,and heat exchanger（AIAI）.From advanced exergoeconomic analysis,in order to reduce the cost associated with exergy destruction of the system,it should focus on improving the efficiency of components.The priority of component improvement in case 1 and case 2 are:reforming reactor>air reactor>carbonator,and the priority of component improvement in case 3 is:reforming reactor>carbonator>air reactor.Therefore,improving the performance of the air reactor and reforming reactor through heat integration of carbon dioxide capture and in-situ reforming system can not only improve the exergy efficiency of the system but also reduce the cost associated with exergy destruction of the system,which provides a theoretical reference for strengthening system design and optimization.