Determination And Bioreduction Of Chelate Complexes In NO_x Scrubber Solution

The emission of large quantity of nitrogen oxides will not only do harm to human health but also cause environmental pollution. For the thermal power plants take a great share of the whole countries'emission of Nitrogen oxides, the NOx removal from its flue gas have become a hot research spot. Considering the disadvantages of conventional technologies, a newly chemical absorption-biological reduction integrated approach to remove the NOx from flue gas is employed. This technology is supposed to have a promising future for its advantages such as high removal efficiency, low cost and no secondary pollution and so on. As part of the research on this newly technology, factors influence the determination of chelate complexes in Nox scrubber solution and features of its microbial reduction by a mixed culture of DN-2 and FR-2 had been discussed in this dissertation.After studying the impact of wavelength, standing time and the pH value on the spectrophotometric determination of Fe(II)EDTA-NO, a conclusion has been achieved and that is the optimal determining condition was at an absorption wavelength of 438nm, while the pH between 5.23-8.07 and operating time within one minute.The complexing agent EDTA do have a impact on the determination of ferrous and ferric iron and their best determine condition in our system was at an absorption wavelength of 510nm with 2.5ml chromogenic reagent and stand for 30 minutes in a waterbath while the pH value between 5.23-5.7.In the situation of the bioreactor with a regular concentration of Fe(II)EDTA-NO(1-2mM), the addition of NH4C1 doesn't make much difference in the removal efficiency. Take both the cost and removal efficiency into consideration, NH4Cl won't be added during the regular running states of the bioreactor.In the series of experiments on the features of microbial reduction of chelate complexes in Nox scrubber solution with different proportion of Fe(Ⅱ)EDTA-NO and Fe(Ⅲ)EDTA, some main conclusions have been achieved as followed. The reduction of Fe(II)EDTA-NO can be completed within 10 hours and the removal rates improved as the initial concentration of Fe(Ⅱ)EDTA-NO increased. However, only 60% of Fe(Ⅲ)EDTA can be reduced within 10 hours and its removal rates declined to a minimum of only 20～30 percent as the initial concentration of Fe(Ⅱ)EDTA-NO increased. The increase of initial concentration of Fe(Ⅱ)EDTA-NO caused a delay of the exponential growth phase of the microorganism. The pH value decreased from 7 to 5.2 as the reduction of Fe(Ⅱ)EDTA-NO within 10 hours. When the initial concentration of Fe(Ⅱ)EDTA-NO is within 1.4～3mM, the amount of ferrous iron increased rapidly in the first 10 hours and achieved a share of 90% of the total iron in the system after about 22 hours, while within 3.2.～5.7mM, the amount of ferrous iron increased a little in the first 10 hours and hardly increased in the next few hours.