Reducing Harmful Components Emission From Sintering Flue Gas By Ammonia-Fe(?)EDTA-Electrolysis Method

Sintering flue gas contains a lot of toxic or harmful substances such as heavy metals,dioxin,SO₂ and NO_X.SO₂ and NO_X from the sintering process respectively exceeded 85%and 40% of the total emission of Iron and Steel Industry,which results in the serious environmental pollution.Meanwhile,the sintering flue gas has the characteristics such as a large amount of flow rate,large fluctuation range of temperature and high moisture content,which causes that it is difficult to simultaneously remove SO₂ and NO_X.In this paper,a method of simultaneous desulfurization and denitrification by Ammonia-Fe???EDTA-Electrolysis is proposed and developed on the basis of the Ammonia desulfurization.At firstly,the laboratory-scale experiments were carried out to study the effects of the initial concentration of the complex agent,the liquid-gas ratio,pH value,electrolysis voltage and reducing agent addition on the desulfurization and denitrification efficiency.Then,the pilot-scale experiments were conducted to study the effects of the electrode type and structure of the electrolysis device on the removal efficiency of SO₂ and NO_X.Based on the optimal conditions obtained from the pilot and bench scale experiments,the experiment with the hot flue gas from a sintering plant was carried out.The main conclusions were the followings:The experimental results showed that as the initial concentration of Fe???EDTA increased from 0.01 mol/L to 0.07 mol/L,the desulfurization efficiencies were above 98% and the denitrification efficiency increased from 30%to 68%.The denireification efficiency would increase with the increase of the liquid-gas ratio at 8-20 L/m³ liquid-gas ratio,the desulfurization efficiencies were above 98%in this run.The maximum denitrification efficiency?about 60%?occurred at a liquid-gas ratio of 20L/m³.When pH value in the scrubbing solution was decreased from 8 to 4,the desulfurization efficiency was decreased from 98% to 60%,and the denitrification efficiency was also decreased from 58% to 35%.In the electrolysis voltage of 1.5?2.4 V,the desulfurization efficiency was independent with the voltage?about 98%?.The denitrification efficiency would increase with the increase of the voltage.While the denitrification efficiency reached 60% at 2.4 V electrolysis voltage.Besides,the addition of Na₂SO₃ as the reducing agent could further improve the denitrification efficiency,while the reducing agent addition had a limited effect on the desulfurization efficiency.In the pilot-scale test,the graphite rode,graphite plate,steel drums and U-shaped stainless steel tube electrode were compared.At the same time,the structure of electrolytic device was optimized.The experimental results showed that the graphite plate horizontal electrolytic tank was the best,and the desulfurization and denitrification efficiency were 98%and 40%,respectively.Based on the optimal parameters obtained from the pilot and bench scale experiments,the experiment with the hot flue gas from a sintering plant was carried out.The removal efficiency of SO₂ and NOX were 98%and 40%,and the concentration of SO₂ and NO_X at the outlet were below 200 mg/Nm³ and 300 mg/Nm³,which reached the standards of Chinese related Acts or Law.