Study on the carbon evolution laws and carbon accounting methods of coal-fired boilers under deep peaking

Abstract

The power grid needs to rapidly modify its power output to counterbalance the variable nature of new energy generation. This necessitates enhanced deep-peaking capabilities in coal-fired boilers. This research investigates the CO2 emission evolution in a 330 MW tangentially fired pulverized coal boiler under varying loads, secondary air distributions, and coal blending to elucidate the CO2 emission evolution dynamics of coal-fired boilers. A comprehensive three-dimensional model of the gas-solid two-phase flow in the furnace, coupled with the coal-firing chemical reactions, is established. Finally, a novel carbon accounting method is proposed, which enhances the accuracy of carbon emission results under various conditions. Results indicate that as the load decreases, combustion becomes progressively less complete. At a 30 % load reduction, carbon conversion into CO2 is minimized, and the amounts of CO and unburned carbon in the fly ash peak. Using equal air distribution and layering coal blending—inferior in layers A, B, and C; general in D; and superior in E—across five burners enhances CO2 production under low-load conditions. Consequently, the levels of CO and unburned carbon in the fly ash are reduced. These research findings serve as a reference for precise accounting of boiler carbon emissions.