Research And Application Of Using Chlorine Dioxide For Odor Control Of Atmospheric Effluents In The Kraft Mill

A lot of malodorous gases were generated in the production process of kraft pulp mill, including hydrogen sulfide, methyl mercaptan, dimethyl sulfide and dimethyl disulfides. In this paper, chemical oxidation techniques was employed that hydrogen sulfide and methyl mercaptan were oxidized to odorless or low odor substances by the chlorine dioxide with strong oxidation characteristics.This technology had low running costs, simple operation and also reduced the capital investment because the existing equipment of the plant just needs a slightly modification before it was put into use to deal with the odors. The main findings are as follows:1. A suitable experimental device was designed in this research project. The experimental device consisted of chlorine dioxide atomization device, the reactor of TRSs and chlorine dioxide, alkaline absorber and tail gas absorption devices.2. To prevent pollution caused by the unreacted chlorine dioxide discharged into the atmosphere, the chlorine dioxide absorb effect of sodium hydroxide solution, sodium sulfide solution, sodium hydroxide and sodium sulfide mixed solution, and sodium thiosulfate solution were studyed contrastively. According to the needs of the experiment, the experimental results determined that the mixed alkaline absorption solution was compositioned by5g/L sodium hydroxide and5g/L sodium sulfide,and the concentration of sodium thiosulfate was0.3mol/L.3. The optimal conditions of the technology which using chlorine dioxide to remove hydrogen sulfide were:molar ratio1:9, reaction temperature40℃, pH value of chlorine dioxide2.0, the reaction time2.4min, sodium thiosulfate concentration0.3mol/L. Under these conditions, hydrogen sulfide removal rate was77.93%. And the experiment under the optimized conditions with mixed alkaline as the absorbent, hydrogen sulfide removal rate could reach99.40%.4. The optimal conditions of molar ratio1:2.5, reaction temperature40℃, pH value of chlorine dioxide2.0, the reaction time2.4min, sodium thiosulfate concentration0.3mol/L, were used chlorine dioxide to remove methyl mercaptan. Under these conditions, methyl mercaptan removal rate was73.19%. And the experiment under the optimized conditions with mixed alkaline as the absorbent, methyl mercaptan removal rate could reach99.80%.