Numerical investigation of temperature distribution in the furnace of a coal fired grate boiler in part load conditions

Abstract

Gas temperature distribution along the grate length in part load conditions is expected to be non-uniform and vary significantly from the nominal. The objective of this work was to simulate the combustion process inside the furnace of a WR-25 coal fired grate boiler at two part load conditions. The results obtained were then compared to on-site temperature profile measurements taken 0.8, 2 and 3.5 meters above the grate level. Numerical analysis was performed using a commercial CFD (computational fluid dynamics) code. Boundary conditions at the grate-freeboard interface were calculated with a black-box type model. Off-design air distribution along the grate was taken into account based on real unit inspection. Model predictions demonstrated a good overall qualitative match with measured temperature profiles, but a quantitative comparison shows a need for improvements in the modeling. It was also shown that more attention needs to be paid to the modeling of soot, as it has a major impact on predicted temperatures.