Development of a Low-NO_x Emission Slagging Combustor

ABSTRACT

A vertical slagging combustor has been developed for use with pulverized coal, coal/water mixtures, coal ash and sewage sludge ash. Primary air is supplied from the top of the combustor through a swirler and secondary air is tangentially injected into the combustor from the upper side. The secondary air produces a stronger swirl pattern than the primary air. The flow pattern in the combustor is optimized for high slag capture and combustion efficiency by controlling the ratio of primary air to secondary air. Two-stage combustion is employed to produce low NO_x emissions. Slag capture and combustion efficiencies for pulverized coal and coal/water mixtures are 90-99%. The minimum value of NO_x emissions is approximately 150-200 ppm, corrected to 6% O2

This slagging combustor has many possible applications including use as a gasifier for a scrap melter. The reducing gas produced by the slagging combustor is injected into the scrap melter, along with oxygen, in order to melt the scrap. It is also possible to use this slagging combustor for the slagging of coal ash and sewage sludge ash in order to safely and economically dispose of the ash. The slag capture rate is over 95% for ash. The slag shows no leaching of harmful substances such as mercury, chromium, lead, cadmium, arsenic, cyanogen or PCB

Key Words:

• NO_x
• Slagging Combustor
• Coal Water Mixture
• Pulverized Coal
• Sewage Sludge
• Heavy Metals