In Japan, combustion modification and SCR process are widely applied for NO control in thermal power plants. By combustion modification, 50-70% of NOx can be reduced to 40-60 ppm for gas-fired, 80-120ppm for oil-fired and 150-200ppm for coal-fired boilers. Recently, in-furnace NOx reduction techniques such as IFR, three-stage combustion are also developed. When further NOx reduction is needed, flue gas treatment technologies such as SCR should be used. Simultaneous SO2 and NOx control processes using activated char or electron beam being developed for cost reduction. NOx control technologies may become more important in many countries to solve acid rain problem.
