Nitrogen oxide (NOx) emission reduction during pellet induration by fuel addition to the green pellets and decreased excess air
A research project was undertaken to determine if coal addition to fluxed-magnetite prefired pellets would reduce nitrogen oxide (NOx) emissions during pellet induration. Iron-oxidation-rate tests, coal-oxidation-rate tests and calcinations-rate tests were conducted in a laboratory furnace to determine the amount of coal necessary to provide adequate heat for limestone calcination without producing detrimental effects to magnetite oxidation. Pilot-scale pot-grate tests were then performed both with and without coal in the prefired pellets to verify pellet-quality parameters and nitrogen oxide emissions. The off-gas during each pot-grate test was analyzed for NOx, CO2, CO, SO and O2. There was approximately a 10% reduction in NOx emissions with coal addition during the normal pot-grate firing cycle. There was a 75% reduction in NOx emissions during firing cycles that used 25% to 75% excess air during firing rather than the normal 300% excess air.
Key worrdsTaconite processing Pellet induration Nitogen oxide emmisions Coal addition
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