Abstract
Concentrated animal feeding operations (both slaughter and dairy cattle) lead to land, water, and air pollution if waste storage and handling systems are not effectively managed. At the same time, cattle biomass (CB), which includes both slaughter/feedlot biomass (FB) and dairy biomass (DB), have the potential to be a source of green energy at coal-fired power plants. Part I presented results on NOx reductions with pure FB or Coal: FB blends as reburn fuels. Part II deals with results from reburning with pure DB or Coal: DB blends as reburn fuels. A mixture of NG with a small amount of NH3 was used to generate the baseline NOx of 400–420 ppm (or 185–194 g/GJ). NOx emissions were found to be reduced by as much as 96% when reburning with FB. The effects of reburn fuel type, equivalence ratio (ERRBZ) in the reburn zone, vitiated air, several injection configurations of reburn fuel and initial NO concentrations on NOx emissions were investigated. The ERRBZ shows a significant effect on the NOx reduction. The 20% heat input by reburning was the better operating condition for the long-term operation due to its ash production. The results reveal that reburn with DB fuels is an effective technology for NOx emission control when the initial NOx emission is higher than 275 ppm (or 127 g/GJ or 0.3 lb/MMBtu).
Highlights
Introduction and Literature ReviewAccepted: 1 November 2021Electric power utilities consume 80% of the one billion tons of coal produced annually [1]
To enhance NOx reduction, meet the NOx emission requirements for coal-fired utilities and help dairy industries dispose of feedlot animal waste or dairy biomass (DB), the current study focuses on developing an energy conversion technology using DB as a reburn fuel
The primary fuel fired in the main burner zone is natural gas (NG), and the reburn fuels considered for current experiments are: Texas Lignite Coal (TXLC), Low Ash Partially Composted
Summary
Electric power utilities consume 80% of the one billion tons of coal produced annually [1]. Renewable alternative fuels have been experimented either as co-fired fuels or as reburn fuels. In co-firing, the renewable fuel is mixed with coal and fired in existing pulverized coal-fired boiler burners. Usually natural gas (NG) as a reburn fuel (RF) is injected downstream of coal-fired boiler burners to reduce NOx generated by coal burners {list of Acronyms at end of Text}. A conventional, upward-fired coal-fired burner with reburn fuel injection along with overfire air (OFA) is presented in Figure 1 [2]. Due to the increasing cost of NG ($5.02/GJ or $5.30/MMBtu as of 2021), alternate fuels including coals are being used as reburn fuels. Biomass fuels have attracted close attention in recent years due to growing energy needs, federal mandates to use renewable fuels and shrinking fossil fuel supplies.
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