Study On Flue Gas Denitration Of Fe II (NTA)-coal Slurry Method In The Presence Of SO 2 . 101677245

The nitrogen oxide in coal-fired flue gas is mainly NO which is almost insoluble in water or alkaline solution. So ferrous chelates are used to absorb NO. Although the ferrous chelate FeII(NTA) can increase the removal efficiency of NO, the F(II) can be easily oxidized to Fe(III) by O2 in flue gas. Because FeIII(NTA) is not capable of binding NO, the denitration efficiency decreases quickly. Researches have showed that coal pyrite can be leached by oxidant, produing ferrous iron which is just the desired ion in NO removal with FeII(NTA).In this study, a bubbling reactor was used as the absorbing equipment. NO, SO2, N2 and O2 were used to simulate flue gas. The coal powder of particle size fraction of 200~450?m was used to prepare the slurries in which the FeII(NTA) concentration was 10 mmol/L. The function of coal pyrite was studied in the process of absorbing NO with FeII(NTA) in the presence of SO2. The effects of the inlet gas concentrations(O2, NO and SO2), reaction temperature and pH were examined on the NO removal efficiency, the ferrous ion concentration, the fraction of iron leached, etc. The liquid products of denitrification were also measured.Experimental results showed that the removal efficiency of NO increased with decreasing O2 concentration and with increasing concentrations of NO and SO2. As the reaction proceeded, the fraction of leached iron increased continuously, and it increased with increasing concentrations of O2, SO2, and NO. Experimental results also showed that too high or too low pH value was unfavourable to the absorption of NO. As the pH value was less than about 6, the removal efficiency of NO, the concentration of ferrous ion, and the fraction of leached iron increased with the increase of pH, reached the maxima at about pH 6, then decreased with further increase of pH. Similarly, as the reaction temperature is less than about 60 ?, the NO removal efficiency, the ferrous ion concentration, and the fraction of leached iron increased with increasing temperature, reached the maxima at about 60 ?, and then tended to decrease as the temperature further increased. It was deduced that the effects of slurry pH and reaction temperature on NO removal efficiency etc. were related to their influences on the capacity of FeII(NTA) to complex NO and on its regeneration rate. Experiments under different experimental conditions all showed that the iron leaching process could be described by the reaction-controlled shrinking core model. The measured liquid denitrification products showed that the removed NO was mainly converted to ammonia. The sum of ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen basically balanced with the amount of NO removed.