Simultaneous Desulfurization And Denitrification Of Sintering Gas By Using Ammonia/Fe~Ⅱ EDTA Solution

In order to control sintering flue gas to pollute the environment, desulfuration and denitration technology have been widely studied by experts at home and abroad. But at present independent desulfuration and denitration is main technology, which is circumscribed.Firstly, according to thermodynamic analysis and chemical stoichiometry, the feasibility of desulfuration and denitrification in ammonia wet was analyzed and the desulfuration and denitrification process in NH3·H2O-FeⅡEDTA system came forward. Finally, the independent reaction equation and the relation between reaction temperature and balance branch pressure of SO2and NO were determined. The result showed that rising reaction temperature went against desulfuration and denitrification reaction.In a batch bubbling-absorber, the desulfurization and denitrification efficiencies of independent desulfuration by ammonia, independent denitration by Fe"EDTA and simultaneous desulfuration and denitration by ammonia containing Fe"EDTA have been researched. It turned out that when the concertration of NH3-NH4+was2.14mol/L,complexing agent concentration was0.01mol/L and the absorption solution initial pH value was6.5, reaction temperature was50℃, independent desulfuration efficiency could be kept above95%during80min and denitration efficiency could be kept above40%during40min.When simultaneous desulfuration and denitration by ammonia containing Fe"EDTA was studied, denitration efficiency in absorbent increased significantly with the concentration of NH3-NH4+increasing as the concentration of NH3-NH4+was less than2.14mol/L.The denitration efficiency was restrained by more SO42-ions in solution because more SO42-would occupy some Fe"EDTA ligand. The chemical reactions of NH3removing SO2and Fe"EDTA removing NO both were exothermic reactions so higher temperature was not beneficial to simultaneous desulfurization and denitration. The composition forms of FeⅡEDTAin solution were relative to pH value. When pH value was about6, association constants of Fe2+and EDTA got the largest14.25. The efficiency of denitration increased with the concentration of Fe"EDTA increasing until the concentration of Fe"EDTA up to0.03mol/L, and then the efficiency of denitration increased slowly. Compared with the other complexants, Fe"EDTA was selected as the optimum complexant mixed with ammonia solution. According to experimental results, the optimum factors of the researched system for desulufurization and denitration simultaneously by ammonia solution mixed with Fe"EDTA were the concentration of NH3-NH4-of2.14mol/L, aqueous absorbent temperature of50℃, initial pH value of6.5, and Fe"EDTA concentration of0.03mol/L, which desulufurization and denitration efficiency got100%and69%respectively. When14%O2was added to simulate flue gas, the denitration efficiency could be kept at about70%.In a double-stirred reactor, SO2and NO absorption rates have been investigated. The results showed that the SO2absorption rate was proportional to the NH3-NH4+concentration. The NO absorption rate increased nearly invariable as the NH3-NH4+concentration rises above2.14mol/L. The SO2absorption rate increased quickly when the Fe"EDTA concentration was below0.03mol/L and increased slowly above0.03mol/L. The NO absorption rate increased more than3times when the Fe"EDTA concentration increased from0.01mol/L to0.05mol/L. With the temperature increasing, the SO2absorption rate and the NO absorption rate both increased. The pH value affected SO2and NO absorption rates greatly. SO2coexisting with NO in the feed gas streams favorably affected the NO absorption. NO inlet concentration in the feed gas streams made a neglectful effect on SO2absorption rate. Improving oxygen content and gas flow were adverse to SO2and NO absorption rates. The reactions between Fe"EDTA and NO were determined as pseudo-first-order reaction. The relationship between the enhancement factor and square root of the concentration of Fe"EDTA was linear and the value was E=230431CBL1/2(R=0.9899).The forward second-order rate constant for the complexation of NO was k2=1.40x108L/(mol·s)...