Study On Thermal Effects Of Cu-Fe-based Oxygen Carriers In Lignite Chemical-looping Gasification Process

Chemical-looping gasification technology,as a new type of gasification technology,is a method developed based on chemical-looping combustion and applied to the gasification of solid fuel coal,biomass and so on.In the process of chemical-looping gasification,the pyrolysis and gasification of solid fuels requires a large amount of heat.If the operation of gasification system relies only on the heat given off by the oxidation of the oxygen carrier in the air reactor to maintain the operation of the system,the limited heat-carrying capacity of the oxygen carrier will lead to a significant increase in the circulation of the oxygen carrier,and increase the cost of operation and maintenance of the gasification system.In this paper,Cu-Fe-based oxygen carriers in the lignite chemical-looping gasification process were used to improve the energy distribution of the gasification system by taking advantage of the feature that the Cu-based components exothermic in the reduction process.Cu-Febased oxygen carriers can also be used in the efficient production of hydrogen-rich syngas.The factors influencing the gasification process of chemical-looping gasification were studied in this paper.In order to better study the reaction properties of Cu-Fe-based oxygen carriers and their thermal effects,this paper firstly analyzed and simulated the lignite chemical-looping gasification process by using thermodynamic calculation methods and Aspen Plus software.The lignite chemical-looping gasification model was constructed in Aspen Plus software by using the Gibbs free energy minimization principle.The product law and energy balance relationship between reactors in the lignite chemical-looping gasification process were analyzed in this part.The results shows that hydrogen-rich syngas can be efficiently produced using Cu-Fe based composite oxygen carriers.The copper-iron ratio of complex oxygen carriers,the equivalent ratio of oxygen carriers,the vapor flow rate and the reaction temperature can influence the process of gasification of chemical-looping to produce syngas.Increasing the copper-iron radio and oxygen-carrier equivalent ratio in oxygen carriers can effectively reduce the heat requirements of fuel reactor and gasification reactor.Especially,under the simulated conditions,when the copper-iron ratio of the oxygen carrier rises from1:9 to 5:5,the circulating ratio of the gasification system decreases from 65.07 to 4.21.Based on computational simulations,chemical-looping gasification experiments were carried out on a small fixed-bed laboratory device built by using lignite coal from Inner Mongolia as raw material to investigate the factors influencing the chemical-looping gasification process.The results show that Cu-Fe-based oxygen carriers have excellent reactivity in the lignite chemical-looping gasification process and can be efficient conversion of lignite with vapor as gasification medium to improve the quality of syngas.Increasing the oxygen carrier equivalent ratio,the vapor flow rate,and the temperature can be effective in increasing the carbon conversion rate of lignite.Decreasing the oxygen-carrier equivalent ratio,increasing the vapor flow rate and temperature can increase the gasification efficiency of chemical-looping gasification systems.In order to reveal the thermal effects of the reduction process of oxygen carriers,the reduction process of Cu-Fe-based oxygen carriers under different reduction conditions was studied on a small fixed-bed laboratory device.The thermal effects of Cu-Fe-based oxygen carriers were studied by observing the temperature change inside the reaction device and the energy change relationship of the reaction system.Cu-Fe-based oxygen carriers can release heat during the gasification reaction of lignite chemical-looping gasification in the process of lignite co-reduction.The thermal effects can be more obvious with the increase of the radio of Cu.In particular,when the copper-iron ratio in the oxygen carrier is 5:5,the energy released by the reduction process can maintain the energy requirements of the system in the experimental system to some extent.