The fuel staging combustion technology is a promising low NOx combustion technology for coal-fired boiler. In order to reduce NOx emissions, the burners of a 600MWe coal-fired boiler are retrofitted in which methane gas is selected as a secondary fuel for re-combustion. The CFD models of combustion process are built to investigateeffects of the methane gasratio on combustion process and NOx emissions. A total of 4 cases are numerically studied, including the pure coal combustion case, the coal combustion with 7.5%, 10%, 12.5% of methane gas re-combustion cases respectively. The results show that the re-combustion of methane can reduce the temperature at primary combustion zone, but increase the temperatures at the re-combustion area and the furnace outlet. The NOx concentration at the furnace outlet reduces with the increasing methane gas ratio.Methane re-combustion can greatly benefit to the NOx emissions reduction.
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