Pilot-Scale Experimental Study on Impacts of Biomass Cofiring Methods to NOx Emission from Pulverized Coal Boilers—Part 2: NOx Reduction Capability through Reburning versus Cofiring

In this study the NOx reduction capability of reburning three biomasses (i.e., wood pellet, torrefied biomass, and empty fruit bunch) via 12 cases (i.e., four reburning ratios for every biomass) is investigated in a 1 MWth-scale pilot-scale furnace. These reburning cases are compared with 12 cofiring cases presented in the Part 1 paper on a consistent basis. It is found that, for every cost to purchase and prepare biomass, reburning technology provides significantly better NOx abatement performance than cofiring (up to 3.4 times). NOx reduction effectiveness as high as 4.9 could be achieved by reburning, which means the percent of NOx abatement could be 4.9 times higher than the percent of reburning ratio. It is found that the highest NOx reduction per thermal unit of biomass happens at the lowest reburning ratio, and increasing the reburning ratio leads to a reduction in NOx abatement effectiveness in an exponential decay manner. Unlike cofiring technology, reburning was found to have little dependence on the fuel characteristics, such as fuel ratio or fuel-N, when it comes to NOx abatement potential.