Catalytic Hot Gas Cleaning of Fuel Gas from an Air-Blown Pressurized Fluidized-Bed Gasifier

Catalytic ammonia decomposition and tar reduction by a Ni catalyst were studied using a feed gas from a pilot-scale pressurized fluidized-bed gasifier. Tests were conducted in a tubular fixed-bed reactor with a space time of about 3 s at 800−900 °C and 12 atm. Ammonia removals of 35−95% and light tar conversions of 90−95% were observed. The amount of the light hydrocarbons was found to have a negative effect on the ammonia decomposition. An ammonia concentration in the fuel gas, gas residence time, and catalytic bed temperature also had a significant influence on the ammonia removal efficiency. After the catalyst, CO 2 and CO approached equilibrium values, but the content of H 2 and H 2 O was lower because of reactions with tar. The heating value of the fuel gas remained the same. The gasification efficiency increased by about 10%, mainly because of catalytic tar cracking. Deactivation of the catalyst was not observed in the fuel gas containing 50−150 ppm H 2 S and about 10 g/Nm 3 tar.