Optimisation of the operation variables of a supercritical water oxidation process

2000 ◽  
Vol 42 (5-6) ◽  
pp. 107-113 ◽  
Author(s):  
M.J. Cocero ◽  
D. Vallelado ◽  
R. Torio ◽  
E. Alonso ◽  
F. Fdez-Polanco
Keyword(s):  
Organic Compounds ◽  
Removal Efficiency ◽  
Residence Time ◽  
Supercritical Water ◽  
Water Oxidation ◽  
Isopropyl Alcohol ◽  
Reaction Medium ◽  
Supercritical Water Oxidation ◽  
Operation Conditions ◽  
Wide Range

The unique physical-chemical properties of water above its critical point (374.2°C and 22.1 MPa) makes supercritical water (SCW) an effective reaction medium for oxidation of organic compounds. Gases and many organic compounds are miscible in SCW, so reaction between oxygen and waste is carried out without interface transport constraints. Supercritical water oxidation (SCWO) can give high destruction efficiencies for a wide variety of hazardous wastes, at low reactor residence times. To study the SCWO, experiments were carried out in a pilot plant equipped with a pressure shell and cooled wall reactor. Effect of operation variables: oxidant excess, reaction temperature and residence time, is studied in order to optimise the contaminant removal efficiency. Aqueous solutions of isopropyl alcohol were used as feed. No effect of air excess and residence time higher than 1 minute on removal efficiency was found, so exclusive dependence of temperature is concluded. Whereas temperature is above 650°C, reactor can work in a wide range of operation conditions with destruction efficiency over 99%. In addition, operation at optimal conditions is reported, using 10%(w) isopropyl alcohol – 1%(w) aniline as feed. Removal efficiencies higher than 99.9% and nitrite-nitrate concentrations less than 10 ppm were obtained.

Dioxin Destruction by Supercritical Water Oxidation

2013 ◽  
Vol 864-867 ◽  
pp. 1709-1712 ◽  
Author(s):  
Qi Cheng Zhao ◽  
Xu Dong ◽  
Ming Hui Zhou ◽  
Jing Chang Wang
Keyword(s):  
Organic Compounds ◽  
Aromatic Compound ◽  
Residence Time ◽  
Supercritical Water ◽  
Water Oxidation ◽  
Supercritical Water Oxidation ◽  
Common Component ◽  
Initial Concentration ◽  
Promising Technology ◽  
Temperature And Pressure

Dioxin is a typical aromatic compound and also a common component of the wastewater from the manufacture of dye, rubber, drug, plastic, paint, etc. The supercritical water oxidation (SCWO) has been recognized as promising technology for waster treatment, and The organic compounds can be decomposed completely in a few minutes.The experiments are conducted at an initial concentration 0.012 mol/l for Dioxin and an excess multiple 10 for H2O2. The effects of the residence time, temperature and pressure on Dioxin destruction rate are examined.

scholarly journals Supercritical water oxidation for the destruction of hazardous waste: better than incineration

2015 ◽  
Vol 373 (2057) ◽  
pp. 20150013 ◽  
Author(s):  
Bushra Al-Duri ◽  
Faihan Alsoqyani ◽  
Iain Kings
Keyword(s):  
Supercritical Water ◽  
Water Oxidation ◽  
Isopropyl Alcohol ◽  
Flow Reactor ◽  
Plug Flow ◽  
Reaction Medium ◽  
Supercritical Water Oxidation ◽  
Split Ratio ◽  
N Removal ◽  
Better Than

Supercritical water oxidation (SCWO) is an advanced process mainly employed for the treatment of hazardous stable wastes, otherwise treatable by incineration. It is based on the unique properties of water above its critical point ( T c =675 K, P c =22.2 MPa), making it a superior reaction medium for the destruction of all organics in the presence of oxygen. This work presents preliminary laboratory scale studies on SCWO of nitrogen (N)-containing hazardous hydrocarbons, with a view to enhancing the process performance, using available reagents and non-complex reactor design. This article investigates the destruction of dimethylformamide (DMF), carried out in a continuous (plug flow) reactor system. SCWO of DMF was enhanced by (i) a split-oxidant system, where stoichiometric oxidant was divided between two inlet ports at various ratios and (ii) the addition of isopropyl alcohol (IPA) as a co-fuel, premixed with the feedstock. Testing a range of temperatures, initial DMF concentrations, oxidant ratios, IPA ratios and oxidant split ratios, selected results were presented in terms of % total organic carbon and % N removal. Reaction kinetics were studied and showed a dramatic decrease in the activation energy upon adding IPA. Split-oxidant-feeding enhancement depended on the split ratio and secondary feed position.

scholarly journals Supercritical Water Oxidation of 3-Methylpyridine with Propylene Glycol

2021 ◽  
Vol 33 (7) ◽  
pp. 1573-1578
Author(s):  
Falah Kareem Hadi Al-Kaabi ◽  
Bushra Al-Duri ◽  
Iain Kings
Keyword(s):  
Propylene Glycol ◽  
Removal Efficiency ◽  
Supercritical Water ◽  
Water Oxidation ◽  
Isopropyl Alcohol ◽  
Flow Reactor ◽  
Hydroxyl Groups ◽  
Supercritical Water Oxidation ◽  
Toc Removal ◽  
Positive Effect

The destruction of 3-methylpyridine by supercritical water oxidation (SCWO) using propylene glycol (PG) and isopropyl alcohol (IPA) as co-fuels in a plug flow reactor was carried out. Hydrogen peroxide was the oxygen source. All the experiments were carried out at 25 MPa and a range of temperatures from 425-525 ºC. The residence times range from 6 s to 14 s. Results were presented in terms of total organic carbon (TOC) as a function of time with various process parameters. The findings support the positive effect that propylene glycol has on the destruction of 3-methylpyridine, where TOC removal is ≥ 97.5% at 525 ºC and 14 s. The maximum TOC removal efficiency is 93% at 425 ºC, 14 s, and the [propylene glycol]/[3-methylpyridine]o ratio of 3. The removal efficiency of nitrogen in the presence of propylene glycol reaches 89% at 525 ºC and 10 s. The oxidant ratio also has a positive effect on the removal of TOC in the three systems. Addition of propylene glycol causes a significant development in the ratio at 425 ºC, more so than when isopropyl alcohol was added. This is due to two hydroxyl groups in propylene glycol oxidation that enhance the reaction by generating various free radicals.

Effect of Buoyancy on Heat Transfer in Supercritical Water Flow in a Horizontal Round Tube

2005 ◽  
Vol 127 (8) ◽  
pp. 897-902 ◽  
Author(s):  
Majid Bazargan ◽  
Daniel Fraser ◽  
Vijay Chatoorgan
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Water Oxidation ◽  
Local Heat Transfer ◽  
Heat Fluxes ◽  
Supercritical Water Oxidation ◽  
Transfer Coefficients ◽  
Horizontal Pipe ◽  
Free Region ◽  
Wide Range

Heat transfer to supercritical water and buoyancy∕natural convection effects are becoming increasingly important areas of research due to current trends in nuclear reactor design and supercritical water oxidation facilities. A pilot-scale supercritical water oxidation loop was constructed at the University of British Columbia. For this work, the facility was used to study the relative importance of buoyancy effects on supercritical water flowing in a horizontal pipe. Local heat transfer coefficients at the top and bottom surfaces of the horizontal test section were systematically measured over a wide range of conditions at supercritical pressures between 23 to 27 MPa, uniform heat fluxes were up to 310kW∕m2, and the mass flux ranged from 330 to 1230kg∕m2s. It was found that neglecting buoyancy effects could cause large discrepancies between the predictions of available empirical correlations and the experimental data. The data was used to assess available criteria for the buoyancy-free region during horizontal supercritical fluid flows. The criterion of Petukhov and Polyakov, which, for the range of parameters in this study, was found to be accurate in predicting the onset of buoyancy effects. The experimental investigation is confined to supercritical flows with heat addition only. Hence, no heat loss conditions at supercritical temperatures were investigated.

Modeling of Non-catalytic Supercritical Water Oxidation of Phenol

2015 ◽  
Vol 10 (4) ◽  
pp. 243-251 ◽  
Author(s):  
S.M. Ghoreishi ◽  
S.M. Shariatmadar Mortazavi ◽  
Ali Hedayati
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Concentration ◽  
Residence Time ◽  
Supercritical Water ◽  
Water Oxidation ◽  
Phenol Concentration ◽  
Supercritical Water Oxidation ◽  
Effective Parameters ◽  
Numerical Predictions ◽  
Phenol Conversion

Abstract The non-catalytic supercritical water oxidation (SCWO) of phenol was modeled using Gopalan-Savage and Thornton-Savage global and network rates. Comparison of experimental data for the phenol conversion with the numerical predictions of this study indicated very close compatibility. Applying the validated model, the phenol conversion and selectivity of various products were studied as a function of effective parameters such as feed phenol concentration, reactor residence time, feed temperature, and feed oxygen concentration. The results of modeling analysis show that an appropriate elevated temperature range (460°C < T <500°C) and long residence time (≈90 s) reduce the concentration of hazardous products (i.e., dimers, dibenzofuran, dibenzo-p-dioxin) and maximize the selectivity of environmental benign products such as water and carbon dioxide. Also, high oxygen concentration (≈0.01 mol/L) increase water and carbon dioxide yield. Moreover, high feed phenol concentrations cause a shortcoming for the SCWO system in terms of phenol conversion and selectivity of desirable environmental products. As a consequence, the feed phenol concentration of ≤2 × 10−3 mol/L is recommended as the appropriate condition.

The Treatment of Concentrated Landfill Leachate from Membrane-Based Processes by Supercritical Water Oxidation

2014 ◽  
Vol 522-524 ◽  
pp. 560-564 ◽  
Author(s):  
Yan Meng Gong ◽  
Shu Zhong Wang ◽  
Yan Hui Li
Keyword(s):  
Residence Time ◽  
Supercritical Water ◽  
Landfill Leachate ◽  
Water Oxidation ◽  
Batch Reactor ◽  
Oxygen Demand ◽  
Ammonia Nitrogen ◽  
Supercritical Water Oxidation ◽  
N Removal ◽  
Varied Temperature

Supercritical water oxidation (SCWO) of concentrated landfill leachate has been carried out in a batch reactor in fluidized bed sand bath, operated under varied temperature (450-600 °C), pressure (23-29 MPa), residence time (5-20 min) and oxidation coefficient (1.5-3.0). The experimental results indicated that temperature and oxidation coefficient had significant influences on the oxidation reaction, whereas the pressure and residence time were not crucial factors. The chemical oxygen demand (COD) and ammonia nitrogen (NH4-N) removal efficiencies could reach up to 99.23% and 98.64% at 600 °C, 25 MPa and 5 min with a oxidation coefficient of 2, respectively, and the effluents could be discharged harmlessly.

Modeling of a Porous Reactor for Supercritical Water Oxidation by a Residence Time Distribution Study

2003 ◽  
Vol 42 (10) ◽  
pp. 2122-2130 ◽  
Author(s):  
E. Fauvel ◽  
C. Joussot-Dubien ◽  
E. Pomier ◽  
P. Guichardon ◽  
G. Charbit ◽  
...  
Keyword(s):  
Residence Time ◽  
Supercritical Water ◽  
Water Oxidation ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Supercritical Water Oxidation ◽  
Distribution Study

Removal of Organic Matters in Pesticide Wastewater by Supercritical Water Oxidation

2014 ◽  
Vol 955-959 ◽  
pp. 2340-2348 ◽  
Author(s):  
Dong Hai Xu ◽  
Shu Zhong Wang ◽  
Chuan Bao Huang ◽  
Xing Ying Tang ◽  
Yang Guo ◽  
...  
Keyword(s):  
Chemical Oxygen Demand ◽  
Residence Time ◽  
Supercritical Water ◽  
Water Oxidation ◽  
Oxygen Demand ◽  
Reaction Pathways ◽  
Experimental Plant ◽  
Supercritical Water Oxidation ◽  
High Concentration ◽  
Organic Matters

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.

Parameter Optimization of Municipal Sludge Treated by Supercritical Water Oxidation Process

2014 ◽  
Vol 1010-1012 ◽  
pp. 693-698
Author(s):  
Mei Gao ◽  
Shu Zhong Wang ◽  
Hong Ma
Keyword(s):  
Total Nitrogen ◽  
Residence Time ◽  
Reaction Temperature ◽  
Supercritical Water ◽  
Water Oxidation ◽  
Oxidation Process ◽  
Removal Rate ◽  
Supercritical Water Oxidation ◽  
Municipal Sludge ◽  
Optimum Reaction

Supercritical water oxidation process can effectively degrade the total nitrogen in municipal sludge. In order to obtain the optimum parameters of municipal sludge treated by supercritical water oxidation, this article selected the total nitrogen removal rate as the evaluation value, and used response surface methodology to optimize the parameters of sludge treatment by supercritical water oxidation, the parameters including temperature, pressure, residence time and oxidation coefficient. The results show that the reaction temperature, pressure and residence time exist interaction, and the influence degree of parameters is: pressure > reaction temperature > reaction retention time; The optimum reaction conditions are as follows: reaction temperature 539 °C, pressure 27 MPa, residence time 434 s, and oxidation coefficient 2.16, under these conditions, the total nitrogen decreasing efficiency can reach 74.12%.

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