| At present,the annual primary energy consumption is huge,resulting in an increase in carbon dioxide emissions and climate warming.The control and reduction of carbon dioxide emissions have an important impact on climate change.Biomass fuels have a wide range of sources and low prices.The use of biomass for chemical looping combustion has broad prospects.A new type of chemical looping combustion device is designed,which is characterized in that the fuel reactor side is composed of three reactors connected in series.The device can use the oxygen carrier waste heat for biomass gasification reaction,and gas fuel produced is reburned and exothermic,the thermal efficiency of the system is improved.To confirm the operating characteristics of the device,this paper designs the operating conditions based on the response surface method and conducts cold experiments.The results show that circulating flow rate increases with fluidizing wind speed,and is less affected by the opening rate of the air distribution plate and the biomass mass fraction.The air reactor pressure drop decreases with the increase of the air reactor wind speed.The fuel reactor pressure drop is mainly affected by the fuel reactor wind speed.Wind speed is higher,the pressure drop is greater.The increase of biomass mass fraction and the decrease air distribution plate opening rate also increase fuel reactor pressure drop.Cyclone separator pressure drop increases with air reactor wind speed,and decreases with fuel reactor wind speed increase and opening rate.The density of biomass particles and quartz sand particles are quite different,and different types of biomass have little effect on the circulating flow rate.To further clarify the device gas-solid flow characteristics,the CPFD calculation method is used to simulate and device basically reached a stable state after 5s.Particles at the air reactor shows "dilute up and concentrated down" in the axial direction,the high concentration area shows periodic changes at the bottom,and particles shows a "ring-core structure" in the radial direction.Particles axial velocity is divided into three parts.The velocity fluctuates at the 0.4m feed port and the 0.9m reducer,and the overall velocity rises with the acceleration of the fluidizing gas.The three beds on the fuel reactor side operate in series in coordination,which realize the particles normal circulation in the system and maintain dynamic stability.Under different wind speeds,the simulation results of reactor pressure drop are basically consistent with the experimental results.The maximum error is 4.6% and the decrease of the open cell ratio and the increase of the mass fraction will increase the overall pressure drop.The particles in the cyclone are in spiral motion,and the degree of wear is mainly determined by the air reactor fluidizing wind speed.The wall can be thickened at key locations to prevent damage.The opening rate and mass fraction have little effect on the pressure drop of the cyclone separator.During variable load operation,mainly adjusting the lower looping seal control system returned material volume.Increasing the return air and selecting appropriate discharge port position can effectively increase the circulating flow rate,otherwise,it reduce the flow rate.The selection of wind speed and the height of the discharge port can provide references for actual variable load operation. |
