The fuel staging combustion technology is a promising low NOx combustion\ntechnology for coal-fired boiler. In order to reduce NOx emissions, the burners\nof a 600 MWe coal-fired boiler are retrofitted in which methane gas is selected\nas a secondary fuel for re-combustion. The CFD models of combustion\nprocess are built to investigate effects of the methane gasratio on combustion\nprocess and NOx emissions. A total of 4 cases are numerically studied, including\nthe pure coal combustion case, the coal combustion with 7.5%, 10%,\n12.5% of methane gas re-combustion cases respectively. The results show that\nthe re-combustion of methane can reduce the temperature at primary combustion\nzone, but increase the temperatures at the re-combustion area and\nthe furnace outlet. The NOx concentration at the furnace outlet reduces with\nthe increasing methane gas ratio. Methane re-combustion can greatly benefit\nto the NOx emissions reduction.
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