Numerical Simulation of Low-Frequency Surge of Double-Outlet Return Valve for CFB Boiler

In the actual operation of the 350-MW supercritical CFB boiler, low-frequency surge of the return valve occurs, causing cracks in the insulation layer castable inside the return valve and affecting the normal and safe operation of the boiler. The computational particle fluid dynamics (CPFD) numerical simulation method was adopted to determine the optimal operation condition of the return valve through the analysis of fluidized air (u(f)), loose air (u(s)) and return air (u(r)). The results show that a stable material seal is formed in the return valve if u(f) is 16 m/s. When u(s) varies from 0.05 to 0.10 m/s, the material circulation efficiency is higher. And the optimal range of u(r) is 1.0 similar to 1.5 m/s.