Stages of combustion of gaseous fuel in a fluidised bed reactor (A - Combustion over the fluidized bed’s surface, Regime A, Tbed = 200°C, the edges of the reactor is not visible, B - Combustion in a bubble leaving the fluidized bed, Regime B, Tbed = 710°C, C - Combustion inside the fluidized bed. Regime C, Tbed = 870°C, D - Combustion inside the fluidized bed, Regime C, Tbed = 920°C.