Oxidation of Industrial Dyeing Wastewater by Supercritical Water Oxidation in Transpiring‐Wall Reactor

Huang

et al. 2014

AMR

Supercritical water oxidation (SCWO) is an alternative to effectively dispose many varieties of organic wastewaters. In this article, a high concentration pesticide wastewater with very complicated components was handled by SCWO in a batch experimental plant at 25 MPa, 410–580 °C within the oxidant coefficient of 1.1–4.0 and the residence time of 1.0–10.0 min. The results show that reaction temperature, oxidant coefficient, residence time can improve XCOD(removal efficiency of chemical oxygen demand) of reactor effluent. XCODreaches up to 99.89% at 550 °C, 25 MPa with the oxidant coefficient of 3.0 and the residence time of 5.0 min, and the corresponding COD concentration is 73 mg/L. Residence time indicates a relatively more important influence on COD1at higher reaction temperatures and OCs. Furthermore, possible reaction pathways for SCWO of organic matters in the pesticide wastewater were also proposed primarily.

Section: Resultssupporting

confidence: 92%

“…The former transforms organic matters in the wastewater into smaller gaseous hydrocarbons [32]. Gong et al [31] found that CO 2 , CO and N 2 were the main gaseous products. N, introduced from the waste or air, is transformed into N 2 or N 2 O, whereas N 2 O can be catalytically converted to N 2 [43].…”

mentioning

confidence: 99%

Removal of Organic Matters in Pesticide Wastewater by Supercritical Water Oxidation

Huang

et al. 2014

AMR

“…In this work, we mainly investigated the effects of temperature and OR on pollutant removal. This was mainly based on the following considerations: For the pressure, many related studies reported that the effects of pressure on pollutant removal are minimal at the pressure range of 23–30 MPa. ,, In the following study, the pressure was kept at 25 MPa. For the reaction time, because the experiments were performed in a batch reactor, the reaction time at the desired temperature and pressures was not easy to control accurately at several seconds compared with the continuous operation adopted in industry. , We did not study the effects of reaction time on pollutant removal in this study.…”

Section: Resultsmentioning

confidence: 99%

Oxidative Degradation of Lurgi Coal-Gasification Wastewater with Mn₂O₃, Co₂O₃, and CuO Catalysts in Supercritical Water

et al. 2012

Ind. Eng. Chem. Res.

Lurgi coal-gasification wastewater was degraded in supercritical water using Mn2O3, Co2O3, and CuO as catalysts. The experiments were performed in a batch reactor at temperatures of 380–460 °C and oxygen ratios of 1.5–3.5. The results involved evaluation of TOC and NH3–N removal efficiencies; detection of the main products in the effluent; XRD, SEM, and BET analyses of the catalysts; and detection of metal ions leached from the catalysts. Maximum TOC and NH3–N removals were found with Co2O3 catalyst at 460 °C and OR = 3.5. The effluent quality could meet class-I criteria of the Integrated Wastewater Discharge Standard (GB 8978-1996). The catalytic effects on pollutant removal were in the order Co2O3 > Mn2O3 > CuO. The major phase of Mn2O3 transformed into MnO2 with a decreasing BET surface area at 460 °C and an oxygen ratio of 3.5. Serious Cu-ion leaching occurred during the process and intensified with increasing temperature.

“…This is not propitious to the oxidation of LCWG in supercritical water. On the other hand, the rate constant of oxidation reaction increased with the increasing pressure [9]. This is in favor of removing pollutants.…”

Section: Introductionmentioning

confidence: 92%

Supercritical Water Oxidation of Lurgi Coal Gasification Wastewater and Evaluation of the Combined Process with Gasification

et al. 2012

AMR

Degradation of Lurgi coal gasification wastewater in supercritical water was investigated in a batch reactor, and a combined process of supercritical water oxidation (SCWO) and gasification was put forward to utilize the material and energy in SCWO effluent. The technical feasibility and economy were evaluated. In the SCWO process, when operated at condition of 500 °C, 25 MPa, oxygen ratio of 3.5 and residence time of 15 min, the concentrations of COD, NH3-N and volatile phenol in effluent reduced to 27, 11 and 0.4 mg/L, respectively, where the removal efficiencies were 99.81%, 99.85% and 99.99%, accordingly. The effluent could reach national discharge standard I (GB 8978-1996), and can be used as the gasification agents of gasifier via a pressure reducer. For a single Lurgi gasifier, the combied process could save 23 t/h of steam and 1550 kg/h of O2, which is equal to 4996 yuan/h.