Retrofitting Strategy and Operating Technology of Pure Burning Zhundong Coal in a 135 MW Circulating Fluidized Bed Boiler

Abstract

Zhundong coal is rich of alkali metals, and coal ash contains large amounts of Na and K element, which can easily lead to slagging and contamination problems, and affect the normal operation of the boiler. This paper focused on the slagging characteristics of the 2×135 MW circulating fluidized bed (CFB) boilers in the actual operation burning Zhundong coal, and proposed the corresponding renovation plan and operation technology through mechanistic analysis. The results show that increasing the gas velocity at the separator inlet can improve the separation efficiency and circulating rate; increasing the area of platen heating surface and improving the efficiency of separator help to achieve the cooling of the furnace chamber; diluting alkali metal content with pulverized coal boiler ash can reduce the formation of alkali metal sulfate. After the optimization, the target boiler was put back into operation at the original load for about 8 months. The comparison with the operation effect before modification shows that the staining and slagging problems are significantly improved while burning pure Jundong coal at high efficiency and low cost, which verifies the feasibility of the proposed technical solution and also provides a reference for other Jundong coal utilization engineering projects.

Keywords

• circulating fluidized bed (cfb) boiler
• zhundong coal
• contamination
• slagging
• cyclone efficiency improvement