Experimental and Numerical Investigations in a Gas-Fired Boiler With Combustion Stabilizing Device

The combustion stability has a significant influence on safety and reliability of a gas-fired boiler. In this study, a numerical model was first established and validated to investigate the effect of combustion stabilizing device on flow and combustion characteristics of 75 t/h blast furnace gas (BFG) and coke oven gas (COG) mixed-fired boiler. The results indicated that the device coupled with four corner burners enables the flame to spin upward around its side surface, which facilitates heat exchange between BFG and the device. Under stable combustion condition, the combustion stabilizing device can be used as a stable heat source and enhance heat exchange in the furnace. Then, to obtain optimal COG ratio, combustion process of different blending ratios were experimentally investigated. The experimental results revealed that the energy loss due to high exhaust gas temperature is relatively high. COG ratio should be set up taking into account both boiler efficiency and NOX emissions. When COG blending ratio is maintained about 20%, the thermal efficiency of the boiler is 88.84% and the NOX concentration is 152 mg/m(3) at 6% O-2, meeting NOX emissions standard for the gas boiler.