Supercritical Water Oxidation For The Destruction Of Aniline Wastewater

At present, organic pollution has become the primary problem endangering the earth's environment. Particularly, severe environmental pollution just like aniline, which seriously affected on human health, has attracted a lot of concerns. Therefore, the study of wastewater treatment will be the typical practical significance.Supercritical Water Oxidation(SCWO) is a highly effective technology for the decomposition of hazardous compounds. When exceeding critical point of water(Tc=374℃,Pc=22.1MPa),the values of density, dielectric constant, hydrogenous bond and ionic product of water drop down, supercritical water acts as a non-polar solvent of high diffusivity and excellent transport properties. The SCWO process that is based on the special physical properties of supercritical water has a great many of advantages. According to the characteristic of supercritical water, this paper described the feature of the supercritical water oxidation, at meantime the supercritical water oxidation of high concentration organic wastewater and reaction dynamics research are reviewed.On these bases, using the advanced intermittence reaction experiment device of SCWO, the oxidation of aniline wastewater which produced in phosgene production and 2,4-DAT were carried out at different conditions. The results concluded that:1.High concentration organic wastewater could be treated effectively by Supercritical water oxidation,In experimental conditions, the CODCr removal rates of two kinds of wastewater reached up to 96.17% and 99.38%, which under the National emission standard. The result showed that SCWO is a high-efficiency water treatment technique.2.The reaction temperature, pressure, water retention time, oxidant amount, PH value and the choice of catalysts are the main factors in reactions.The CODcr removal rate of organic pollutants will increase with the increment to f reaction temperature, pressure, residence time, concentration of oxidants or added some catalysts.Among these factors, the temperature, residence time, and oxidant content on the influence of CODCr removal, PH value of reaction effects are relatively weak.3.The global kinetics for 2,4-diaminotoluene under SCWO was described with the thermodynamic PR equation and a power-law equation. The activation energy of oxidative degradation Ea=63.1±1.67kJ/mol, pre-exponential factor A=10371±012. The reaction of SCWO is 1.143 order in COD and 0.376 order in oxidant. The residual standard deviation of regression in the global kinetics is relatively small, and XC(Removal efficiency) from calculated was more in line with the experimental date. Under 385-420℃,26MPa, the oxidation reaction rate equation follows: r=103.71exp(-(63.1)/(RT))[C]1.143[O]0.3764.After the treatment by supercritical water oxidation, the degradability of the organic pollutant would be greatly increased.5.In process of experiments, the appearing of corrosion problems produced negative effects in sealing performance, resulting in leaking a small excitant odour of ammonia; At meantime, salt sediment problem would build up the ceramic tube so we should take some measures to prevent it.