Catalytic removal of NH3 by both unprocessed and H-2-reduced titanomagnetites (Fe2.9Ti0.1O4) from two gases has been experimentally investigated in a lab-scale fluidised bed reactor. The test gases include Ar gas as control and simulated producer gas from biomass steam gasification (H-2, CO, CO2 and CH4). In the test gases, the NH3 concentration was 2300 +/- 100 ppmv and the operation temperatures were varied from 500 to 850 degrees C. The experimental results show that in the control Ar gas, the H-2-reduced titanomagnetite had much higher activity than the unprocessed titanomagnetite to decompose NH3 at all of the temperatures tested, and the efficiency of NH3 removal increased with reaction temperature. The NH3 decomposition by the reduced titanomagnetite was 97.8% at 500 degrees C, 99.7% at 600 degrees C, and 100% at 750 and 850 degrees C, in comparison with corresponding values of 31.6%, 34.0%, 83.9% and 93.2% for the unprocessed titanomagnetite. Therefore, the H-2-reduced titanomagnetite was then employed to remove NH3 in the simulated producer gas in which the NH3 decomposition was 28.4 +/- 3.4%, 94.7 +/- 2.8% and 98.4 +/- 0.4%, respectively, at 500, 750 and 850 degrees C. In NH3 decomposition in the simulated gas, side reactions have been identified and analysed which played different roles at different temperatures and also affected the gas composition. At 500 degrees C, the carbon formation from the Boudouard reaction significantly suppressed the activity of the reduced titanomagnetite for NH3 decomposition.