REDUCTION OF NOX EMISSIONS FROM COAL POWER PLANTS

Reduction of NOx Emissions from Coal Power Plants

Reduction of NOx Emissions from Coal Power Plants

Introduction

The threat of increased global warming has subjected the use of fossil fuels to increasing scrutiny in terms of greenhouse gas and pollutant emissions. As a result, the use of renewable and sustainable energy resources, such as biomass, for electricity production has become increasingly attractive. The use of dedicated biomass feedstocks for electricity generation could help reduce the accumulation of greenhouse gases because carbon dioxide is consumed during plant growth. The agricultural and wood products industries generate large quantities of biomass residues that could also provide fuel for electricity production. Increasing the use of such fuels could alleviate the burdens and environmental consequences of waste disposal in the agricultural and wood products industries. Landfill lifetimes could be extended and methane and CO2 production from biomass decomposition would be avoided.

Reduction of NOx emissions from coal power plants

One solution is replacing conventional burners with low-NOX burners, which improve mixing and allow greater adjustment. Conventional burners consist of a port that forces a mixture of pulverized coal and air into the furnace. Only limited adjustment of the burner tip and air mixture is provided. A typical low-NOX burner includes a custom coal tip and a dual air register. Major adjustments include outer air register, inner air register, and burner tip position.

NOX emissions also can be reduced by introducing overfire air (OFA) to the burner configuration. This method provides one or two rows of air inlet ports to the wall above the burner grid. Combining low-NOX burners and OFA configurations is a common solution to reducing NOX emissions. The effectiveness of a given proposed configuration must be analyzed and tested to achieve optimum results. The initial capital investment to build new biomass power plants to increase the percentage of biomass power is high. Cofiring biomass with coal in coal-fired power plants is a lower capital cost option for increasing the use of biomass to produce electricity. Coal-fired power plants are used to produce most of the electricity in the United States. If biomass were cofired at low percentages in these plants, the use of biomass for power production could dramatically increase. Cofiring biomass and coal takes advantage of the high efficiencies obtainable in coal-fired power plants. Fuel diversity is another advantage of biomass/coal cofiring which reduces the need for a constant supply of biomass that would be required in a biomass power plant. Cofiring biomass and coal is also a viable way to manage the increasing emissions of greenhouse gases and other pollutants from power generating facilities.

Biomass and coal have fundamentally different fuel properties. For instance, biomass is a more volatile fuel and has higher oxygen content than coal. In general, biomass contains less sulfur than coal, which translates into lower sulfur emissions as higher blending ratios of biomass are used. Wood fuels generally contain very little ash (1% or less); consequently, increasing the ratio of wood in biomass/coal blends can reduce the ...