Computational fluid dynamics based retrofits to reheater panel overheating of No. 3 boiler of Dagang Power Plant

摘要

The commercially available CFD package, FLUENT was utilized to numerically diagnose the metal surface overheating issues of the reheater pendants that exist in the full-scale No. 3 boiler of Dagang Power Station, Tianjing, China. Some factors that may affect the velocity and temperature distributions at the section of the final reheater inlet (final superheater outlet) had been taken into account when the designated coal was burned, such as the quantity and fashion of counter-flow in the operation, the pressure difference in the air box, and the downward inclination of the secondary air injection. The basic conclusion is that some corresponding measures must be taken to rebuild the flow field constructions in order to effectively avoid the boiler reheater and superheater pendant metal overheatings. To obtain detailed background, eight reformation cases were arranged on the main field influencing reasons to retrofit this boiler numerically. Compared to the base case A, all the reformation cases had some emendatory effects to the flow and temperature distributions. The most outstanding among the reformations was case I, where the secondary air (OFA and the upper secondary air of D primary air burner) was operated with counter-flow with a downward angle, and the pressure difference in the air box was increased. Case I can more efficiently modify the velocity and temperature deviations in the overheating place of case A to ensure the furnace will operate within stable and safe conditions. Much better flow field is built by case I and it is recommended for the final operation when the BCD grinder combination is in service. Undoubtedly, these conclusions are of value to the other units of this power plant, and also to other power plant furnaces throughout China with similar construction and capacity.