| ClO2 is a highly efficient green oxidant, it has been successfully applied in the field of water treatment. But ClO2 application in the field of desulfurization and denitration process is still at the experimental research stage, the mechanism、process、process conditions and ClO2 solution supply method of ClO2 solution desulfurization and denitration are needed to research furtherly. Under laboratory conditions, based on the lower cost of ClO2 solution with the sodium chlorate and hydrochloric acid, the text used it to desulfurize and denitrate. The oxidising properties、efficiency and influence factors of NO and SO2 removal by ClO2 solution were studied firstly, then the mechanism of desulfurization and denitration by ClO2 solution was analyzed, finally through the design of ClO2 oxidant supply system, and using it in the desulfurization and denitration process of the coal-fired boiler flue gas to examine the actual engineering application effect of desulfurization and denitration, it could provide reference for application of the chlorine dioxide liquid denitration. The main research contents and results were as follows:(1)The change of redox potential of ClO2 solution with temperature (T), concentration (c)、pH were investigated With ORP (Oxidation-Reduction Potential) meter, results showed that redox potential of ClO2 solution increased with the increase of ClO2 concentration or liquid-gas ratio, and it decreased with the increase of concentration or pH, including the influence of pH and concentration of ClO2 was larger, the influence of temperature was relatively small, ClO2 solution has high oxidation ability under the conditions of pH=3～5、T =20℃、c=200mg/L, the redox potential is between 0.76～0.92V.(2) Using a lab-scale spray desulfurization and denitration devicethe, the influence of concentration of ClO2 solution(c)、concentration of gas、pH、packing height (h), temperature, liquid gas ratio (L/G) to desulfurization and denitration rate by ClO2 solution were investigated, the better desulfurization and denitration condition was pH=4, T=20℃, h=25 cm、L/G=20L/m3, under the condition ofc=100mg/L, NO(268mg/m3) removal rate was 98%; under the condition ofc=200mg/L, SO2(1143mg/m3) removal rate was 99.8%. When ClO2 solution was used to desulfurize and denitrate at the same time, the SO2 removal rate was higher than NO generally, and the NO removal rate was lower than NO alone.(3)Results of the mechanism on desulfurization and denitration of ClO2 solution show that NO can be oxidized by ClO2 solution and converted into NO3-, and the NOx of high oxidation state oxidized by ClO2 can also be absorbed by NaOH solution and converted into NO2- and NO3-; SO2 can be oxidized by ClO2 solution and converted into SO42-, and the SOx of high oxidation state oxidized by ClO2 can also be absorbed by NaOH solution and converted into SO32- and SO442-.(4) In the engineering application, the continuous ClO2 oxidant supply system was applied to desulfurize and denitrate, firstly the cheap calcium alkali liquor was used to remove SO2 of the flue gas, the rate was above 99%. The ClO2 solution of 200～500 mg/L、pH=5.5-7 were used to oxidize NO(212-229 mg/Nm3) and absorb with Sodium alkali under the condition of the gas flow velocity is 2～2.5 m/s、temperature is 50～60℃, the efficiency was between 80.4～88.8% from the flue gas which contains 229～239mg/m3 of NOx. The residual NOx in purified flue gas is below 46 mg/m3, and it can achieve discharge standards. |
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