| The NOx from the coal-fired power plant has caused serious environmental pollution, and it has brought the human production and life inconvenient. An economy and high efficiency technology to control the NOx emission is urgently to research and develop. Preliminary study suggests that the calcium based organic salt can removal the SO2and NOx simultaneously, and the application of the technology is wide. But the research is still in its beginning stage, and the reaction characteristic and the function of it is not deep enough understanding. Therefore, it needs to start from the basic research of the technology, to provide the theoretical guidance for its industrial application.Calcium propionate is taken as research object and denitration characteristics of which in the flue gas and during the coal combustion are investigated in this paper. And then, the software is used to simulate the calcium propionate denitration process for the exploration of the denitration mechanism.In order to simulate the boiler reburning zone condition, a hot state denitration experimental device is constructed. On this device, the denitration characteristics of calcium propionate are investigated. Raising temperature, reducing the initial oxygen concentration, increasing the reburning fuel fraction (Rff) and extending the residence time can enhance the de-nitric efficiency effectively. The de-NOx efficiency of CP which is higher than75%can achieved at1273K, with reburning fuel fraction, initial O2concentration and residence time keep at25.99%,3%and0.72s respectively.The characteristics of calcium propionate during the coal combustion are experimental studied, and results show that in the early stages of the combustion the release of NO is promoted with adding calcium propionate, but after that it is inhibited. At1373K, the efficiency of44.8%can be got with Ca/S=2. The result of thermogravimetry shows that the properties of combustion are improved with the addition of CP.Based on the characteristics of calcium propionate pyrolysis exhalation pentanone organic gases and the effect of CaO on denitration by CHi is weak, coupling pentanone combustion model and small molecular hydrocarbon denitration model, establish a new model to describe the calcium propionate denitration process. The contrast of calculated results and experimental results in typical working condition parameters as temperature, the concentration of oxygen and the reburning fuel fraction proves the accuracy of the denitration model, and the error less than5percent points under the condition of appropriate denitration.Use the established pentanone denitration mechanism to simulate various factors on pentanone denitration and to analyse the denitration mechanism. And the results show that the pentanone denitration efficiency first increases then decreases, the optimum "temperature window" for denitration is1223-1473K; the excess air coefficient keeps at about0.5is benefit for NO reduction, too high or low all lowers denitration efficiency; increase the pentanone adding amount can enhance the denitration efficiency effectively, but pentanone to NO mole ratio higher than2.0the growth is slowing. The elementary reaction of H+O2(?)O+OH and H+O2(+M)(?)HO2(+M) which have an important impact on nitric reduction by pentanone. More active radicals, like OH, H, HCCO, HCN are the important middle products which influence the de-NOx process seriously.Add the mechanism of sulfur dioxide, sodium salt and ferric salt to pentanone denitration mechanism to simulate the influence rule of them. Under the appropriate condition SO2can promote NO removal process. The concentration of SO2increases every1000×10"6, the de-NOx efficiency increases by2percent point approximately. The material of HOSO and HOSO2as the most important intermediate products which promote the consume of active radicals as OH, H et al. and the increase the denitration efficiency. In contrast, the additives of NaOH and Fe(CO)5promoting effect is much more apparent. With adding50×10-6concentration of NaOH and Fe(CO)5, the de-NOx efficiency increases5.0～6.0and10.0～14.0percent point respectively. The additives can consume the excess active radicals like OH, H et. Al., which can delay the oxidation of CHi and improve the de-NOx efficiency. |
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