Kinetics of ammonia decomposition in hot gas cleaning

Reduction in the amount of ammonia in fuel gas from biomass gasification wa s studied. Experiments were carried out in a fixed-bed reactor dt 200-1000 degrees C, 21 atm. A kinetic model for ammonia decomposition was developed. The partial pressure of hydrogen in the fuel gas was a key factor to model ammonia decomposition. Activation energies in the empty reactor, on carbon , and in a sand bed were similar, 130-140 kJ/mol. The frequency factors for carbon and sand were 10 times as large as for the empty reactor. The activ ation energy for a Ni-based catalyst was 111-113 kJ/mol. Carbon deposit dea ctivated the Ni-based catalyst. High temperature was found to be essential for avoiding carbon fouling and for achieving high ammonia removal efficien cy. Estimation of the ammonia reduction for fuel gas showed that a moderate amount of ammonia could be removed by use of the Ni-based pellets at 800 d egrees C.