Effect of iron additives on nitrogen reduction and denitrification of long flame coal during pyrolysis and combustion

The nitrogen oxide (NOx) emitted from coal combustion causes serious pollution to the ecological en-vironment,and the direct combustion of household coal accounts for more than 50% of the total emission of coal pollutants.Based on this,it was proposed to achieve the ultra-low emission of NOx through two-step coupling of “pyrolysis nitrogen reduction+combustion denitrification”.The pyrolysis and combustion experiments of coal and metal auxiliary (FeCl3) were carried out in a tubular furnace,and the migration rules of nitrogen in the “pyrolysis and combustion” process were systematically studied by such factors as iron load,pyrolysis temperature and combustion temperature,and the action mechanism of iron auxiliary was discussed.The results showed that when the load ratio of iron additives is 0.5% and the pyrolysis temperature is 1 000 ℃,the nitrogen removal effect is the best,the nitrogen removal rate increases from 66.6% to 93.6%.After high temperature pyrolysis,the iron in coke mainly exists in the forms of Fe2O3,Fe3O4 and α-Fe,these iron phases can catalyze the conversion of more nitrogen-containing compounds into pollution-free N2.At the same time,the increase in temperature is also conducive to the removal of NOx in the combustion process of clean fuel.When the combustion temperature is 1 000 ℃ and the additive load is 0.5%,NOx emission is 116.68 mg/cm3,which is 46.7% less than the NOx emission from raw coal combustion.High temperature is conducive to NOx removal.When the combustion tem-perature is 1 100 ℃,NOx emissions are reduced by 46.7%.Fe2O3 formed in the combustion process has a certain catalytic effect on the reduction reaction of NOx,CO and C,and can catalyze the conversion of NO formed in the combustion process into N2.By adding iron additives in one step,the effects of reducing nitrogen and burning denitrification in two steps were achieved.