NITROGEN OXIDE (NOX) EMISSION REDUCTION DURING PELLET INDURATION BY FUEL-ADDITION TO THE GREEN-PELLETS AND DECREASED EXCESS AIR

摘要

A research project was undertaken to determine if coal addition tofluxed-magnetite pre-fired pellets would reduce nitrogen oxide (NO_x)emissions during pellet induration. Iron oxidation rate tests, coaloxidation rate tests and calcination rate tests were conducted in alaboratory furnace to determine the amount of coal necessary toprovide adequate heat for limestone calcination without producingdetrimental effects to magnetite oxidation. Pilot scale pot-grate testswere then performed with and without coal in the pre-fired pellets toverify pellet quality parameters and nitrogen oxide emissions. The offgasduring each pot-grate test was analyzed for NOx, CO_2, CO, SO_x,and O_2. There was approximately a ten percent reduction in NO_xemissions with coal addition during the normal pot-grate firing cycle.There was a 75% reduction in NO_x emissions during firing cycles thatused 25% to 75% excess air during firing rather than the normal 300%excess air.