Study Of The Corrosion Of The Equipmental Materials In The SCWO Treatment Of HNS Wastewater

SCWO'S reaction of decomposition of organic pollutants for the corrosion of reactor and other equipment is very serious[1,2], especially in response to material flow containing Cl, F, Br and other halogens, and P, S and other elements, it will Promote the intensification of the corrosion rate[3,4].The reactor has been reported that the formation of corrosion of equipment have uniform corrosion, pitting, selective dissolution of alloys, stress corrosion and intergranular corrosion. Corrosion will produce two issues[5]: Firstly, when the effluent contains some of the metal ions may affect the quality of treatment; Secondly, the over-corrosion will affect the pressure system to work properly. Because of material corrosion problems, so that a wider use of the environmental protection technology can be limited[6,7].Therefore, corrosion-resistant materials research becomes extremely important to the SCWO reactor system.To elect the best corrosion-resistant material of the SCWO reactor that deal with HNS wastewater, We make a related corrosion experiment about it.The corrosion tests using the semi-continuous SCWO equipment of the environmental protection technology Co., Ltd. Of Sanmenxia HD, In the semi-continuous SCWO's device, Put the following five materials: stainless steel 316L, 304, Hastelloy C-276 nickel-based alloys, Inconel 625 nickel-based alloys, nickel-base alloy 600 in the form of the coupon linked to the wire in the reaction vessel, Treat the HNS wastewater, And study their corrosion at the same time and oxygen, And on the conditions of the super-critical temperature at 470℃and 570℃; By the orthogonal test of the reaction temperature, time and pressure factors to serve the optimum conditions; Observed the reactor discharge area of the corrosion and test the water pH, salt; According to the corrosion to analyz the corrosion mechanism of materials.The results show that in the supercritical state the five materials produce different degrees of corrosion, and the temperature increase ,The corrosion worse. Compar the corrosion of materials of the two temperature,we can draw the order of corrosion resistance material is: Inconel 625> Hastelloy C-276> Inconel 600> stainless steel 316L> stainless steel 304; in oxygen 1.8MPa (excess) cases, COD's Removal rate increas with the temperature, pressure and residence time, the optimum condition for the reaction is 560℃, 27Mpa, 30S, the COD's removal rate was above 99%; The reaction's main area is the top and bottom; the essence of the SCWO is the acid and alkali's recovery process; the corrosion mechanism of the stainless steel and nickel based alloys is: in the oxidation of high temperature and pressure's medium, stainless steel and nickel-based alloy occurred passivation Phenomenon, is too passive, And the high concentrations of organic compounds in supercritical oxidation system, the decomposition of hydrogen ions, anions such as the surface oxides and other corrosion products generated by chemical dissolution, resulting in stainless steel and nickel-based alloys and other metal matrix of power occurs Chemical corrosion.