Numerical investigation on co-combustion of sludge and coal in a 660 MW pulverized coal boiler

The co-combustion of sludge in coal-fired boilers, as a novel approach to sludge treatment, holds promising prospects for extensive application. The numerical simulation method is employed in this study to model the co-combustion of sludge in a 660 MW pulverized coal boiler at a power plant. By varying operational conditions, we thoroughly investigate the impact of sludge blending ratio, moisture content, and boiler load on combustion performance and pollutant emissions. The numerical investigation reveals that the impact on the boiler remains relatively insignificant when the blending ratio is below 10 %. However, surpassing a blending ratio of 10 % leads to a substantial reduction in temperature. Specifically, at a blending ratio of 20 %, there is an average temperature decrease of 9.3 K observed across each sections of the boiler. Moreover, as the blending ratio increases, there is a concurrent decline in SO₂ and NO_x levels, while CO exhibits an upward trend. Increasing the moisture content will result in a reduction in boiler temperature. In comparison to sludge with a 25 % moisture content, blending sludge with a 45 % moisture content will cause an average temperature decrease of approximately 10 K within the boiler. Augmenting the moisture content will diminish the concentrations of SO₂ and NO_x, while concurrently leading to an elevation in CO concentration (up to a maximum of 107.4 mg/Nm³). The internal temperature and outlet pollutant concentrations both escalate as the boiler load increases. Based on this study, the optimal sludge blending ratio is determined to be 10 %, accompanied by a moisture content of 35 %.