Preparation And Performance Research Of Catalyst For Methanation Of Biomass Fuel GAS

Producting biomass fuel gas through gasification has great economic and social benefits.It can not only reduce the pollutant emission of biomass combustion, but also improve the gas source structure of city gas, and ease the energy supply problem. However, biomass syngas of lower heat value and higher CO concentration should be adjusted through the water gas shift reaction and methanation reaction. With the biomass gasification produced gas as feed gas, the effect of operating conditions on industrial catalysts, the influences of component contents and preparation condition on catalyst as well as as the affecting factors on direct methanantion were studied.TB113 catalyst and HTJ-103TH catalyst were chosen for the water gas shift reaction and methanation, and the influence of operation conditions and promoters on catalyst was studied respectively. The water gas shift reaction based on TB113 catalyst was carried out and the results showed that the CO conversion increased with temperature and steam to gas ratio increasing, space velocity and catalyst charge effected the reaction by changing residence time and diffusion velocity, adding 10%wt CuO as promoter improved the catalyst activity. The HTJ-103TH was sdudied for methanation and the results indicated that with the temperature increasing from 300℃ to 500℃, and the space velocity increasing from 2000h-1 to 7000h-1, the CO conversion of methanation decreased, the mole ratio of H2/CO and CO2 contents in the feed gas increased with CO conversion of water gas shift reaction increasing, and it would reduce methanation reaction degree.Catalyst with 10%wt Mo also showed better activity.Based on the study of the industry catalysts, Fe/γ-Al2O3 water gas shift reaction catalyst, mafnetite and Ni/γ-Al2O3 methanation catalyst were prepared. Preparation conditions and component of catalyst were studied. It was found that water gas shift reaction catalyst with 50%wt Fe content had good activity and the second component Cu, Mn, Ni could improve the CO conversion. Mafnetite with the particle size range in 0.25-0.45mm can aslo be used as water gas shift reaction catalyst and adding Fe was good for the catalytic activity.Ni/γ-Al2O3 with 25%wt Ni content and calcinated at 450℃ showed higher surface area, better activity and stability. The second metal components Mn and Fe can obviously increase the CH4 concentration in the product. Catalyst made through coimpregnation had better activity and Mn impregnated first would improved CH4 selectivity.During the study of Ni/γ-Al2O3, it was found that the methanation had catalyzed the water gas shift reaction. As direct methanation has lots of advantages such as reducing energy consumption, simplifying processes and saving equipment investment. Direct methanation based on Ni-Mn/γ-Al2O3 was investigated and the results indicated that the catalyst could catalyze methanation as well as water gas shift reaction.When the mole ratio of H2/CO was lower than 2, moderate of moisture in the biomass syngas would improve CO conversion and CH4 concentration in the product. As the water gas shift reaction and methanation would reduce energy efficiency, the conversion of these reactions should be controlled at 20%-30% and 40%-50% respectively when the mole ratio of H2/CO was 1.5.