Study On Mass Tranfer And Kinetics Of Absorption Of NO Into Ferrous Chelate Aqueous Solution And Dissimilatory Reduction Of Fe～Ⅲ With Microorganisms

The combustion of fossil fuels generates SO2 and NOX pollutants which cause air pollution and acid rain. Conventional flue gas desulfurization (FGD) scrubbers involve limestone processes, which are efficient for controlling SO2 emission, but are incapable of removing almost water-insoluble nitric oxide.The newly proposed and adopted method in our work for NOX removal from flue gas, i.e. metal chelate absorption combined with microbial reduction, is deemed as a promising method. As part of this work, in this paper, the NO absorption capacity by Ferrous Cysteine (Fe" (CyS)2)solution was studied in an absorber with a sieve plate. The effects of the rate of Fe" /CySH, the concentration of SO32", and the concentration of O2 in the simulated flue gas were examined. The mass transfer and kinetics of the absorption of NO in aqueous ferrous cysteine solutions have been analyzed in a double-stirred reactor. A comparison was made between NO absorption by Fe" (CyS)2 and Fe" (EDTA). And dissimilatory reduction of Fe111 (EDTA) with microorganisms in the system of nitric oxide removal by metal chelate absorption was probingly investigated. The aim of this work was to provide a new method and some fundamental data for NOX removal from flue gas. The main experimental results were as follows:The NO absorption capacity by Ferrous Cysteine (Fe" (CyS)2)solution was studied in an absorber with a sieve plate. The effects of the rate of Fe" /CySH, the concentration of SO32", and the concentration of O2 in the simulated flue gas were examined. The results showed that reasonable absorption amount could economically be achieved when Fe" CySH was kept at 1:4. With the increase of [SO32"] in the solution, the absorption capacity would be improved. When SO32-/ Fe" (CyS)2 was 1:1,the absorption amount increased by 50%. 5.5% O2 in the simulated flue gas reduced the absorption amount of NO by80% and SO32- in the solution could efficiently inhibited the oxidation of absorbents. It was proved that the absorption capacity of NO by Fe" (CyS)2 was a little bigger than Fe" (EDTA).The mass transfer and kinetics of the absorption of NO into aqueous ferrous cysteine solutions have been studied in a double-stirred reactor. And the effects of the concentration of SO32-, and the concentration of O2 in the simulated flue gas were examined. Compared with Fe" (EDTA), the NO absorption rate by Fe" (CyS)2 is lower in the oxygen-free condition while much higher with certain- percent oxygen in the simulated flue gas. The reactions between Fe" (CyS)2 and were determined as pseudo-first-order reaction. The forward second-order rate constant for the complexation of NO to Fe" (CyS)2 was 1.18 X 108 L/mol s at pH 8.0 and 50癈. Three kinds of theoretical models were applied in this reaction and got the same enhancement factors, i.e. E= Y . A comparison was made between the experimental enhancement factor and the data calculated from the models, the maximum error was less than 13%, which is permitted in the research of gas-liquid reaction.In the system of nitric oxide removal from the flue gas by metal chelate absorption, it is anobstacle that ferrous absorbents are easily oxidized by oxygen in the flue gas to ferric counterparts, which is not capable of binding NO. By adding iron metal or electrochemical method, FeIII (EDTA) can be reduced to FeIII (EDTA). However, there are various drawbacks associated with these techniques. The present work involves an investigation of dissimilatory reduction of Fe (EDTA) with microorganisms in the system of nitric oxide removal by metal chelate absorption. Ammonium salt was used to be as the nitric source instead of nitrate, which inhibited the reduction of Fe due to the competition between the two electron acceptors. Supplemental glucose and lactate stimulated the formation of Fe" more than ethanol as the carbon sources. The microorganisms cultured at 50C was not very sensitive to the other experimental temperature, the reduction percentage of Fe varied little with the temperature range of 30~50C. Concentrated Na2CO3 was adde...