Boudouard Gasification Reactivity Of Coal-derived Carbon And Its Electrochemical Performance Of DC-SOFC

Coal is the most abundant and the cheapest fossil fuel on the earth,accounting for about 30 % of the world's primary energy and supplying 40 %of the world's electricity.With the development of modern society,human's demand for electricity is gradually increasing.However,the traditional coal-fired power generation method has a low conversion efficiency and releases large amounts of carbon dioxide and other pollutants.Together with the limitation of fossil fuels,the efficient and clean utilization of coal is now a boring issue to be solved.Fuel cell is the new generation of power generation technology with high efficiency and low emission,which is of great significance to solve China's energy shortage and environmental pollution problem.Solid oxide fuel cell(SOFC)is a power generation device that directly converts the chemical energy of fuel into electricity without burning.Because fuel cell is not limited by the Carnot cycle,the energy conversion efficiency is high;because the fuel does not go through the combustion process,it is environmentally friendly;it is quiet and has low noise due to the absence of moving components.The most notable feature of SOFCs is the fuel diversity.Fuels,such as hydrogen,natural gas,water gas,methanol,gasoline and solid coal et al.,can be used for SOFCs.Especially,solid carbon fuel has the characteristics of high energy density,high safety,easy transportation and storage.Moreover,the single exhaust carbon dioxide from direct carbon solid oxide fuel cell is susceptible to enrichment and reduction.Therefore,the direct carbon solid oxide fuel cell(DC-SOFC)has attracted more and more attention.Coal char is a type of high-calorific value solid carbon obtained from pyrolysis and is a suitable fuel for direct carbon solid oxide fuel cells.Coal char is mainly composed of fixed carbon,ash,moisture and volatile matters.It has been shown that certain components of the ash play the inhibitory effect on the reverse Boudouard reaction of coal char,and that theseinhibitors can be removed by acid treatment.Therefore,the effects of ash removal of coal char on the electrochemical performance of solid oxide fuel cells were investigated by treating coal char with non-oxy acid HF,HCl or their mixture(HF + HCl).The results show that the content of silicon and aluminum oxide suppressing the reverse Boudouard reaction was greatly reduced after the treatment of HF + HCl,and the reverse Boudouard reaction temperature was reduced from 845 ? to 799 ?.The peak power density increased from 67.4 mW cm-2 to 110.2 mW cm-2;the utilization of activated coal char was 1.2 times of that of coal char.The reverse Boudouard reaction is a key reaction closely related to the electrochemical performance of direct carbon solid oxide fuel cells,and the introduction of catalysts can effectively improve the reverse Boudouard reaction rate.Steel slag is an industrial solid waste that occupying a lot of land and causes water and air pollution.The recycling of steel slag not only can protect the environment,but also can make full use of natural resources.Herein the catalytic effect of steel slag treated by acid-dissolving and alkali-precipitating on the reverse Boudouard reaction was studied.The decomposition of steel slag mineral phase released the oxides of Fe,Ca,Mg and other elements,that improved the reverse Boudouard reactivity.The results show that the acid-activated steel-slag catalyst reduced 240 ? of the initial temperature of the reverse Boudouard reaction of coal char,and increased 4 times of the CO producing rate.For the electrochemical performance,the acid-activated steel-slag catalyst enhanced the peak power density of the cell at 850 ? from 67.4 mW cm 2 to 193.6 mW cm 2,and improved the fuel availability from 41.48 % to 79.68 %.