Research Into Wet Ammonia-based Desulfurization And Denitration Of Sintering Flue Gas Simultaneously Aided By Photo-catalyzing From Ferric Oxalate

With the increasingly stringent emission standards of SO₂ and NO_x,the simultaneous desulfurization and denitrification technology has become a new development trend in the field of flue gas purification.The previous research of our group indicated that Fe?II?EDTA-Na2C2O4 compound absorption liquid supplemented with light had a certain regeneration effect on Fe?II?EDTA.In this paper,the research into photo-catalyzing aided simultaneous desulfurization and denitrification of sintering flue gas based on ferric oxalate was investigated.It has carried on the beneficial exploration for the industrial application base of this method.Firstly,the formation of ·OH radical in UV/ferric oxalate system under different parameters was studied by violet spectrophotometry.The results indicated that UV light and ferric oxalate were the necessary conditions for the production of ·OH,[Fe3+] and[C2O42-],p H value,system components were the main factors affecting the rate of radical production.When the p H was 4,the concentration of [Fe3+] was changed in the range of200⁴00umol·L-1,the concentration of [C2O42-] was changed in the range of200⁹00umol·L-1,the production rate of ·OH increased with the increase concentration of [Fe3+] and [C2O42-].When the p H value changed in the range of 2⁶,the formation of·OH increased first and then decreased,and the maximum value was found when the p H value was 3.O₂ contributed to the generation of ·OH radical.The presence of Fe?II?EDTA?NO?consumed the ·OH radicals.UV/C2O42-,UV/Fe2+/C2O42-and UV/Fe3+/C2O42-systems had a positive synergistic effect on the regeneration of Fe?II?EDTA denitration rich solution,after 60 min of photocatalytic regeneration,the removal efficiency of NO recovered from 20.7%,18.8% and 19% to 28.9%,55% and61.1%,respectively.Secondly,the denitrification experiment in UV/Fe?II?EDTA/ferric oxalate system was studied.Experimental results indicated that the adequate reaction mode for this system was to add Na2C2O4 and Fe SO4 independently into NO-absorbed solution.Moreover,the regeneration efficiency was better in acidic solution than that in alkaline solution.Further,the denitrification efficiency of the regenerated absorption solution increased first and then decreased with the concentrations of Na2C2O4 and Fe SO4 increasing.Oxygen showed a positive synergistic effect in photocatalytic regeneration process.The denitrification efficiency of the regenerated absorption solution increased with the concentration of Fe?II?EDTA increasing.SO₂ could promote the removal efficiency of NO.The absorbed NO could be converted into NO-3,and also formed Fe?OH?3 sediment.Under the conditions of Fe?II?EDTA concentration of 0.01mol·L-1 and temperature of 50 ?,the optimum p H value was 5.3,and the optimum concentrations of Na2C2O4 and Fe SO4 were 0.06mol·L-1 and 0.02 mol·L-1,respectively.The denitrificationefficiency of regenerated absorption solution was about 60%.Thirdly,the research into simultaneous desulfurization and denitrification in UV/NH₃·H₂O/Fe?II?EDTA/ferric oxalate system were carried out.The results showed that NH₃·H₂O/Fe?II?EDTA absorption solution had good denitrification ability as well as strong desulfurization ability.Under the synergistic effect of iron oxalate and absorption system,the denitrification efficiency could be restored from about 20% to 52%,desulfurization efficiency could be restored from 40% to 80%.The regeneration efficiency was better when the p H value was 4.35 and 5.20.The optimal concentration ratio of Na2C2O4 to Fe SO4 was 3:1.Keeping the optimum concentration ratio and increasing the total concentration of iron oxalate,the efficiency of the regenerated absorbent solution increased first and then decreased.The highest concentrations of Na2C2O4 and Fe SO4 for regeneration desulfurization and denitration efficiency were0.09mol·L-1 and 0.03 mol·L-1.The concentration of NO had a significant influence on NO removal,but it had no obvious influence on SO₂ removal.The SO₂ concentration had an influence on both NO and SO₂ removal.O₂ could promoted the desulfurization and denitrification efficiency of the regenerated absorption liquid.Under anaerobic condition,the maximum efficiency of NO and SO₂ could be restored to about 51% and 80%,respectively.Under the condition of 12% oxygen,the maximum efficiency of NO and SO₂ could be restored to about 62% and 90%,respectively.In summary,this research established a mild photo-assisted low-temperature wet ammonia simultaneous desulfurization and denitrification process by sacrificing photosensitivity ligands from iron oxalate to regenerate denitrified complexants.Further,it was a new method for synergetic treatment of flue gas multi-pollutants in a wet way.