| Carbon dioxide capture and storage technology can effectively reduce global carbon dioxide emissions.As one of the key technologies for carbon dioxide capture and storage,oxy-fuel combustion has been recognized as an extremely promising technology for industrial applications.However,Its air separation produce oxygen unit has the disadvantages of high energy consumption and high economic cost,which seriously hinders the further commercialization of oxy-fuel combustion technology.Chemical looping air separation(CLAS)is considered as a novel and promising method for providing an efficient and economic oxygen supply for integration into oxy-fuel combustion power plants.In order to understand the process characteristics of CLAS,this study has develop a complex interconnected fluidized bed process model based on the fluidized bed CLAS experiment,identify the influences of operating parameters on system performance and optimize system thermodynamics performance.A new type of dual fast fluidized bed CLAS system has been proposed,which provides a theoretical basis and reference for the development of new CLAS technology.In the process developed model,a fast fluidized bed model and a bubbling fluidized bed model are used to respectively represent the oxidation reactor and the reduction reactor,also the fluidized bed hydrodynamics and the oxygen carrier redox reaction kinetics are considered to grasp the unique characteristics of CLAS process.The process simulation results are consistent with the experimental results,and the rationality of the developed process model is verified.Sensitivity analysis of operating parameters on CLAS system can be found that the high reduction temperature and high fluidizing gas flow rate can enhance oxygen carrier conversion and reduce energy penalty in the reduction reactor.The results of multi-variable optimization based on the minimum specific energy consumption illustrates that compared with the initial operating conditions,38.1%energy savings can be achieved and the optimal oxidation operating temperature,reduction operating temperature,air flow rate,and fluidizing gas flow rate are determined as 830℃,950℃,1133.7 L/h,and 58.4 L/h,respectively.To further improve the performance of the CLAS system and expand the scale of oxygen production,a dual fast fluidized bed reactor with an oxygen production of 1 t/h was designed for the CLAS process based on the design method of chemical looping fluidized bed reactor.According to the results obtained from the design,the process model 2.0 of the CLAS dual fast fluidized bed reactor was constructed,fully considering the characteristics of the dual fast fluidized bed,taking into account the heat exchange network of the cold and hot streams to improve the effective utilize of heat.The simulated results of the process model 2.0 show that the conversion ratio of the oxygen carrier reduction reach up to 67.3%,and the oxygen concentration at the outlet of the reduction reactor is close to the oxygen equilibrium concentration at the setting temperature.The oxygen carrier oxidation conversion ratio and outlet oxygen concentration of the oxidation reactor are determined as 87.3%and 13.5%,respectively.In addition,the specific energy consumption of the dual fast fluidized bed reactor CLAS process model 2.0 system is 18.54 kWh/m3.Compared with the fast-bubbling interconnected fluidized bed CLAS system,the oxygen carrier reduction conversion ratio and the energy performance of the system are significantly improved,which indicates that the new dual-fast fluidized bed reactor form is more suitable for the CLAS process. |
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