Heat Treatment Of Biomass Fuels And Their Efficient Utilization In Direct Carbon Fuel Cells

Direct Carbon Solid Oxide Fuel Cell(DC-SOFC)can use all kinds of solid carbon as fuel,and directly convert the chemical energy from carbon fuel into electric energy.Since this process does not exist combustion and heat engine,it is not restricted by Carnot cycle and has the characteristics of clean and efficient.DC-SOFC can use biomass carbon derived from agricultural and forestry wastes or domestic wastes as fuel.These renewable energy sources are recyclable and inexhaustible,which conform to the principles of circular economy and sustainable development in China.In order to increase the utilization of biomass fuel in DC-SOFC,the discharge mode was improved,DC-SOFC discharging by constant resistance mode is proposed.One-time toothpick and waste carton were used as DC-SOFC carbon source.The feasibility of using waste resources as DC-SOFC fuel and the step-by-step utilization of related additional products were considered.When DC-SOFC oxidant is changed from static air to flowing oxygen,the maximum output power density is increased.DC-SOFC discharging by constant resistance mode,compared with the frequently used constant current mode,this new constant resistance mode can improve the fuel utilization of the cell.When the cell is discharged in constant current mode,the reduction of the specific surface area of carbon fuel will lead to insufficient supply of CO gas in the cell,and ultimately the discharge current can not be maintained.When the discharge voltage of the cell drops to 0 V,there will still be a small amount of residual carbon fuel.In contrast,constant resistance mode for discharging,the load resistance of the external circuit is unchanged,discharge current existed with terminal voltage of the cell,which can fully convert the internal carbon fuel and improve the fuel utilization of the cell.The heat treatment experiment of one-time toothpick as fuel shows that increasing the heat treatment temperature of fuel can increase the fuel utilization of cell,thus prolonging the discharge time of cell.Experiment on different current discharges shows that the mismatch between the electrochemical reaction rate on the anode and the reverse Boudouard reaction rate on the carbon fuel leads to different discharge voltage platforms under conditions of different discharge current.The maximum output power density and discharge capacity of DC-SOFC fueled by 0.2 g pyrolytic carbon from waste carton can reach up to 307 mW cm~-22 and 658 C at850?.Infrared spectroscopy and Raman spectroscopy analysis show that tar produced during pyrolysis of waste carton contain many organic functional groups and tar could be used as chemical raw materials.After discharge of cell,there are many elements and inorganic salts in the residual ash,which has potential to be used as fertilizer.The carton pyrolysis process and its product used as DC-SOFC fuel realize efficient utilization of waste resource,which has the advantages of economy and environmental protection.Natural loading catalysts in carbonized carton can promote the reverse Boudouard reaction rate and further optimize the performance of DC-SOFC.When the oxidant of the DC-SOFC changed from static air to flowing pure oxygen,the maximum power density of DC-SOFC fueled by powdered activated carbon with Ag-SSZ composite electrode and SSZ as electrolyte was improved by 89%from 124mW cm~-22 to 234.4 mW cm~-22 at 800?.