Experimental study on variation characteristics of combustion heat load in circulating fluidized bed under fuel high-temperature preheating modification

Abstract

This study introduces an innovative application of fuel high-temperature preheating modification technology to circulating fluidized bed (CFB), intending to enhance the variable load rate of CFB and reduce its NOx emissions. The variable combustion heat load (CHL) experiments were conducted on a novel CFB experimental platform comprising a preheating modification device (PMD) and CFB. The findings indicate that implementing fuel high-temperature preheating modification technology allows the CFB to operate stably within the range of 30%–100% CHL while maintaining superior combustion efficiency. Moreover, it reduces NOx emissions by over 28% compared to conventional combustion. The decrease in NOx emissions can be attributed to the fuel's preheating modification process inhibiting NOx production and establishing conditions conducive to NOx reduction in CFB. Furthermore, after employing the fuel high-temperature preheating modification technology, the CHL change rate of CFB reached 1.79%/min and 2.27%/min for the transition from 50% CHL to 75% CHL and from 75% CHL to 100% CHL, respectively. These rates represent an increase of 1.59 and 1.80 times compared to the rates observed in conventional combustion processes. The increase in the CHL change rate of different CHL variation intervals is primarily due to the production of high-temperature coal gas and modified char following fuel preheating modification. High-temperature coal gas exhibits a rapid combustion rate, while modified char has a smaller particle size, more developed pore structure, and enhanced reactivity than raw coal.