Experimental study on the load response rate under the dynamic combined combustion of PC coal and CFB coal in a CFB boiler

Abstract

The load response rate of the circulating fluidized bed (CFB) boiler is low for its great thermal inertia. In order to increase its load response rate, a new dynamic combined combustion technology featuring co-combustion of CFB coal and pulverized coal (PC) with high gross calorific value (GCV) is put forward. This combined combustion system was set up on a 240 t/h CFB boiler, and PC coal spraying positions, heating values, and heat ratios were evaluated for their effects on load response rate and combustion performance of the CFB boiler. When PC coal is fed from the secondary air pipes, the relative load change rates (RLCRs) exceed 2.0%/min and meet the requirement RLCR for power dispatching (1.5%/min), and the maximum RLCR is 3.69%/min. Moreover, the weighted average of carbon in residue decreases, and the original NOX emission of CFB boiler increases less than 40 mg/Nm3. Results indicate that the dynamic combined combustion of CFB coal and PC coal with higher GCV fed through secondary air pipes in CFB boiler is a feasible technology to increase its relative load response rate.