| In the paper, the transformation of NOx and heavy metal mercury, both of emission status and of control technologies, the factors affecting removal of NO during Selective non-Catalytic Reduction (SNCR) process and mercury speciation, and both of research status of numerical simulation during coal-fired process were reviewed. On this basis, a set of test bench of level tubular resistance furance was builded which met the experimental research,and properties of removal of NO during SNCR process and transformation of mercury speciation were investigated. The results showed that with the rise of temperature, the efficiency of denitration and of conversion of elemental mercury were firstly rising and then dropping, and both existed an optimal temperature. Denitrification rate and conversion efficiency of mercury increased with the increase of holding time, while denitrification rate decreased continuously and conversion efficiency of mecrcury rised constantly with the increase of the concentration of oxygen in the flue gas. When it come to the increase of the mole ratio of NH3/NO (NSR value), denitrification rate and the quantity of escaped ammonia were both increased continuouly. With respective of increase of the amount of hydrochloric acid gas, the conversion efficiency of mercury speciation increased accordingly. In addition, the conversion rate by the chlorination influence on the elemental mercury was more obviously significant than that by the influence of oxygen oxidation.Experimental results of combining SNCR denitration and transformation of mercury speciation also found that, between low temperature paragraph of 400℃650℃, the effeciency of denitration changed smoothly with the changes of temperature; and the effeciency of denitration was rising with the rise of oxygen concentration, the maximum effeciency of denitration of which reached 36.2%. During the combined reaction, the maximum effeciency of conversion of elemental mercury and denitration were both reduced. According to the impact characteristics of NO and heavy metal mercury about NH3/HCl from coal-fired flue gas, the orthogonal experiment of multi-factors were researched, with the aim of researching the degree of influence of four factors, such as temperature, NSR value, oxygen concentration and the amount of HCl, on the efficiency of denitration and of conversion of mercury speciation.The impacts of the NSR value, the amount of HCl in the SNCR removal of NO and transformation of mecury speciation as well as temperature field and concentration field of the model were simulated with the software CHEMKIN 4.1 and FLUENT 6.2. The calculated results of thermodynamic equilibrium showed that NOx in the flue gas were mainly in the form of NO while NO2 and N2O were relativly small. The amount of HgO was always very small and the main outcomes were HgCl2 at a lower temperature while Hg was the main outcome at a higher temperature. In addition, the temperature range of the conversion from Hg to HgCl2 become higher with the increase of the amount of HCl in the flue gas and the temperature range of HgCl2 stability phase become wider. The results of reaction kinetics simulation showed that with the increase of reaction temperature, the concentration of NO in the outlet of the reactor was firstly down and then come up and the concentration of NH3 went down continuously. Under the condition of the same value of NSR, the maximum removal efficiency of NO increased along with the rise of the initial concentration of NO. The concentration of NO in the outlet of the reactor continuouly declined, while the concentration of NH3 in the outlet of the reactor sharply increased when the value of NSR was up. The content of HgO went up when the amount of oxygen in the flue gas rised. In the same way, the content of HgCl2 went up when the amount of HCl rised. The maximum conversion efficiency of elemental mercury occured at the temperature of 700K and it could reach above 80%. In addition, the content of HgCl2 accouted for a large proportion of the conversion efficiency of mercury. The results of the numerical simulation showed that they matched well with the most conclusions obtained from experimental research. |
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