Study On Catalytic Hydrogasification Of Corn Char To Methane By Fe-CaO Catalyst

Natural gas has high energy density.However,in recent years,the growth of China’s natural gas production has not matched the growth of natural gas consumption,and the gap between supply and demand has become more obvious,which has also threatened our country’s energy security.Biomass can be pyrolyzed into biochar,and then the biochar can be further hydrogasification to produce methane.Char hydrogasification has broad application prospects and is a new way to make up for the shortage of natural gas supply in China.The catalyst is the core of the catalytic hydrogasification of biochar to produce methane,and it is also a hot spot of current research.Previous studies have found that Fe-CaO has significant economic advantages and catalytic effect,but at the same time there are still some problems need to be solved in the application of char catalytic hydrogasification,such as inert carbon.The reaction of carbon and H2 to CH4 occurred in the hydrogasification process,and O was not involved in the reaction formula.However,it was found that the O in char has an effect on the hydrogasification reaction,there is a lack of research in the literature that considers unreacted carbon from the perspective of O.The methanation reaction uses CO2 as the raw material,and increases the utilization and conversion of CO2,which can obtain low-carbon and clean natural gas resources.Therefore,in this paper,corn char and Fe-CaO catalyst are taken as the main research objects.The flow rate of the outlet gas is analyzed,and the change of carbon conversion rate is explored.Trace CO2(introduced O element)is added into the reaction system,hoping to reduce the amount of unreacted carbon,increase the conversion rate of char hydrogasification and increas the utilization and conversion of CO2.Finally,the kinetics of char hydrogasification to methane is discussed.The following conclusions are obtained:(1)In the hydrogasification of corn char,after 1%-5%CO2(0.5-2.5 mL/min)is introduced at 800℃,the CH4 yield increases from 76.6%(0%CO2)to 103.8%(1%CO2)and 157.8(5%CO2).After 1%-4%CO2 is introduced,the maximum generation rate of CH4 is significantly reduced,and the maximum generation rate of CH4 at 5%CO2 is close to that without CO2.CO2 inhibits the hydrogenation of the highly active carbon in char in the early stage of the reaction.After stabilization,the rate of CH4 generation when CO2 is introduced is significantly higher than that without CO2,and the rate of CH4 generation increases slightly with the increase of CO2 concentration,1.79 mL/min for 1%CO2 and 2.76 mL/min for 5%CO2.However,after stabilization,the formation of CH4 mainly comes from the CO2 methanation reaction,not the char hydrogasification.The reaction network of char hydrogasification in the presence of CO2 is far more complicated than expected.(2)After removing the effects of CO2 methanation,the generation rate and yield of CH4 at 800℃ decrease.After a long time reaction,the final carbon conversion rate slightly increases due to the by-product CO.At 700℃,the reaction degree of char is low.The generation of CH4 is mainly due to the CO2 methanation reaction.A small part of CH4 generate through the action of char and CO2.The rate of CH4 generation and CH4 yield increase slightly,and the carbon conversion rate increases due to the by-product CO,but all are less than the situation of 800℃.CO2 inhibits char hydrogasification,and the O in CO2 fails to enter the char structure and the O content in char is not changed.(3)In the experiment of char hydrogasification with trace CO2,char and H2 quickly generate CH4.The reaction of CO2 and the loaded char also promote the increase of the rate of CH4 generation,and the methanation of CO2 makes CH4 generation stably in the later stage of the reaction.The CO2 methanation can be detected only after the reaction has proceeded for at least 60 minutes.At this time,the CO2 is almost completely converted.Although CO2 is not conducive to char hydrogasification,the methanation of CO2 mainly occurs in the later stage of the reaction,and the reaction conversion rate is very high,which is a way to increase the conversion and utilization of CO2.(4)According to the reaction phenomenon,the carbon in char is divided into high-active carbon and low-active carbon,and their kinetic model are established.The reaction rate expressions are obtained through the experimental data,and the model is tested under different hydrogen partial pressures.