Wet oxidation

About: Wet oxidation is a research topic. Over the lifetime, 3094 publications have been published within this topic receiving 61536 citations.

Treatment of combined bleach plant effluents via wet oxidation over a Pd-Pt-Ce/alumina catalyst

Abstract: Supported Pd-Pt-Ce/alumina catalyst showed promising activity over traditional iron oxide, zinc oxide-type, oxidation catalysts for the treatment of pulp mill effluents. However, hot solution coupled with chlorine ions in the oxidation medium not only requires special process equipment but also often leads to catalyst deactivation due to metal leaching of catalyst. Dissolution of catalyst in the reaction medium also requires a further process step to remove the toxic metal ions from the treated stream. To address these problems, we proposed a combined treatment approach for catalytic oxidation of the bleach plant effluents from a softwood kraft pulp mill. Experimental study indicated metal leaching from catalyst can be significantly reduced even avoid with the combined stream at temperatures ranging from 403 to 443 K and at 1.5 MPa in a slurry reactor. Pd-Pt-Ce/alumina catalyst showed promising activity for wet catalytic oxidation of the combined streams. At 443 K and 1.5 MPa, 65% total organic carbon (TOC) and 99% color were removed after 3 h treatment, while only 10% TOC and 79% color reduction were achieved without catalyst at the same experimental conditions. Another advantage with combined treatment approach is that that cheap ferrous-based alloy may be used as construction material for process equipment. Based on the experimental results, implications for process development are discussed.

Oxidation Behavior of High-speed Steels in Dry and Wet Atmospheres

Abstract: The oxidation behavior of high-speed steel (HSS), which is used as the work rolls in hot strip mills, was examined under both wet and dry oxidation conditions. In a dry atmosphere, carbides as well as the martensite matrix were oxidized, while only the matrix was oxidized in the wet atmosphere. After dry oxidation, the M 2 C-, M 6 C- and M 7 C 3 -type carbides maintained their original shapes, while the MC-type carbides were oxidized into parallelepiped (orthorhombic) crystals. The parallelepiped oxides were easily removed from the sample surface due to their low adhesion strength. Double-layered oxides were formed after oxidizing the matrix, in dry as well as wet atmospheres. The outer layer showed a dense structure after dry oxidation, while a columnar and porous layer was formed in the wet atmosphere. In the early stages of oxidation, the high-speed steels oxidized following the parabolic rate law in both the dry and wet atmospheres. The parabolic weight change transformed to a linear one, when the oxide thickness was >1.3 μm by dry oxidation. The transition to a linear weight change was not observed in the wet oxidation. It is believed that, in a dry atmosphere, cracks occurred due to stress accumulation in the oxide layer, while the porous oxide layer hindered crack formation during wet oxidation.