Hydrodynamic Characteristics Of Two-stage Chemical Looping Fuel Reactor To Intensify The Mixing And Separation Of Binary Solid Particles

Chemical looping combustion（CLC）,characterized by the merits of CO₂inherent separation and cascade utilization of energy,paves a new way for the clean,efficient utilization for fossil energy.It represents a brand-new field of energy and environment.Generally,an interconnected fluidized bed was adopted.However,the slower reaction rate between solid fuel and oxygen carrier particles,the mixing difficult of two high distinct particles and complicated separator for un-reacted char brings more challenges for designing chemical looping combustion reactor.To address above issues,a novel interconnected fluidized bed was proposed,and a cold setup was designed and erected.The mixing and segregation characteristic of solid fuel and oxygen carrier was investigated systematically,which will provide theoretical basis for hot device.In this paper,the proposed novel fuel reactor is designed to two stages,i.e.,fast mixing stage and separation stage of unreacted char.The intensified reaction and separation with simple structures was achieved in two stages,respectively.The jet feeding device at the bottom of designed fuel reactor can guarantee the excellent mixing and reaction between solid fuel and oxygen carrier.Based on the proposed concept,a cold model device was designed and built,and preliminary experiments were carried out using quartz sand as the bed material and air as the fluidizing gas.The results of 40min continuous operation and the pressure drop distribution indicated the dynamically stable operation of the system,which verifies the rationality of the proposed concept and design method.Using quartz sand as the bed material,a detailed study of the hydrodynamics characteristic in the novel interconnected fluidized bed was carried out.The solid content rate of the first-stage fuel reactor in the fast mixing reaction sectionε_s>0.15,which belongs to a high-density fluidized state,and the higher particle concentration strengthens the reaction between the oxygen carrier and the solid fuel.Further studies have shown that the particle concentration decreases with the increase of the superficial gas velocity,and increases with the increase of the loading capacity.The solid circulation rate increases with the increase of the superficial gas velocity and the loading capacity.Using ferrotitanium powder as the oxygen carrier,coal powder and birch powder as solid fuels,the particle mixing and separation characteristics in the cold model device were studied.The results show that with the increase of U_FR-1 and U_FR-2,the mixing indexes M₁ and M₂ both decrease.As the solid fuel-oxygen carrier ratio increases and the stabilization time increases,the mixing index will increase.A comparative study with the bubbling bed found that under the above operating conditions,the two-stage fuel reactor designed in this paper is superior to the bubbling bed in terms of mixing capacity.The experimental study of the separation characteristics shows that the separation efficiency gradually increases with the increase of U_FR-1 and U_FR-2.But U_FR-1 has a greater effect on the separation efficiency of the device.In addition,the separation efficiency increases as the solid fuel-oxygen carrier ratio increases.As the operating time increases from 5 minutes to 25 minutes,it gradually increases and then decreases.There is an optimal operating time.