SCWO
1)Applied Thermal Engineering
Volume 26, Issue13 September 2006, Pages 1385-1392 /
Supercritical water oxidation improvements through chemical reactors energy integration
Abstract
Supercritical Water Oxidation (SCWO) is the process of complete destruction of toxic and hazardous organic wastes in a compact, totally enclosed system through oxidation in water brought to temperatures and pressures above its critical point: 374 °C and 218 atm. At these conditions, organic materials, gases and water form a new phase, completely mixed, that provides the environment for a rapid and complete oxidation. Typical products from a SCWO process include carbon dioxide, water, and inorganic salts or acids. SCWO advantages include very high destruction efficiencies, low NO_x and SO_x occurrence, no dioxins or furans, totally contained process, no smokestack, relatively low temperature operation, and compact size. The chemical reactors energy integration (CREI) concept focuses on, simultaneously, the entropy generation reduction of both chemical reactor network (CRN) and heat exchanger networks (HEN) and the search for possibly new operating conditions for some of the reactors (if not all) to accomplish this goal. The basic idea of CREI is to replace each of the reactors of the CRN with a corresponding virtual heat exchanger, having the chemical reaction enthalpy as thermal load, thus creating a virtual HEN. Then, combine this VHEN and the existing HEN into an extended system, which will be the object of the pinch analysis. Care should be taken that the virtual heat exchanger system produces the same amount of entropy as the replaced chemical reactor.
Pinch and CREI analysis were applied to SCWO process and the suitable network configuration and operating conditions were found to achieve the minimum entropy generation.
2) Fluid Phase Equilibria
Volume 244, Issue 1 , 5 June 2006, Pages 78-85
Bubble points of the systems isopropanol–water, isopropanol–water–sodium acetate and isopropanol–water–sodium oleate at high pressure
Abstra
Supercritical water oxidation (SCWO) is a powerful technology for destroying organic wastes with high removal effiiencies. Corrosion and salt deposition are the main challenges for the industrial development of the SCWO process. In SCWO heteroatoms are oxidized until high oxidation states: oxides, acids or salts. If there are enough cations, the heteroatoms precipitate as salts and eventually can be recovered. Cations can be introduced in the system by adding organic salts to the feed. The organic part of the salt is oxidized to CO₂ and water, and the cations remain free to join the free anions and precipitate as inorganic salts. The thermodynamic study of this system it is very interesting for future modeling of the SCWO process.
Bubble points of the systems isopropanol (IPA)–water, IPA–water–sodium acetate and IPA–water–sodium oleate were determined in the temperature range (396 and 460 K), pressures higher than 0.35 MPa, with IPA concentrations lower than 5 mol% and salt concentrations of 5 and 8.2 mol% for sodium acetate, and 0.11 and 0.25 mol% for sodium oleate. Bubble points were determined using a Cailletet apparatus that operates with the synthetic method.
As expected, the vapor pressure of the system increases as IPA concentration is increased, and in general decreases when salt concentration increases. The measured vapor pressures of mixtures of water and IPA were consistent with literature data.
   The experimental data were correlated using the Anderko–Pitzer EoS, which was specially developed for water–salt systems at high temperatures and pressures. Densities and vapor pressures of IPA and the experimental data presented in this work were used for obtaining the parameters of the EoS in the range of pressure and temperature of the data. In the range of temperature and concentration considered, the average deviations between experimental and calculated vapor pressures were %ΔP = 1.18% for the system IPA–water, %ΔP = 4.03% for the system IPA–water–NaAc and %ΔP = 2.77% for the system IPA–water–NaOl
3) Chemosphere Volume 62, Issue 5 , February 2006, Pages 827-832
Phosphorus release from ash, dried sludge and sludge residue from supercritical water oxidation by acid or base
Abstract
Leaching of ash and dried sewage sludge were investigated and compared with the leaching results of sludge residue from supercritical water oxidation (SCWO). This article focuses on how the composition of ash and sludge residues influences the extraction of phosphate and heavy metals and if different treatment temperatures of the sludge effect the leachability. Results showed that acid leaching gave a higher release of phosphate than alkaline leaching for all ash and sludge residue samples. Also, alkaline leaching dissolved phosphate with a lower metal contamination than acid leaching. Furthermore, it was found that iron had a low release at both alkaline and acid leaching from ash and from SCWO residue.
The difference in composition of ash and sludge residue samples had no significant influence on release of phosphate at high concentrations of acid. Phosphate release from ash, dried sludge at 300 °C and SCWO residue showed similar results at 1 M acid leaching. However, it seems to be easier to release phosphate from the SCWO residue than from the ash at low acid concentrations. SCWO residue showed higher release than the other ashes at 0.5 M HCl. Results for alkaline leaching showed higher release from ash at 1 M NaOH than from SCWO residue or from dried sludge at 300 °C. The leaching of phosphate from dried sludge seems to be temperature dependent, as the dried sludge treated at higher temperature showed less release of phosphate. It was found that the pre-treatment of the ash may be important for better release of phosphate.
4) Chemosphere. 2006 Feb;62(5):827-32. Epub 2005 Jun 20.
Phosphorus release from ash, dried sludge and sludge residue from supercritical water oxidation by acid or base.
  Leaching of ash and dried sewage sludge were investigated and compared with the leaching results of sludge residue from supercritical water oxidation (SCWO). This article focuses on how the composition of ash and sludge residues influences the extraction of phosphate and heavy metals and if different treatment temperatures of the sludge effect the leachability. Results showed that acid leaching gave a higher release of phosphate than alkaline leaching for all ash and sludge residue samples. Also, alkaline leaching dissolved phosphate with a lower metal contamination than acid leaching. Furthermore, it was found that iron had a low release at both alkaline and acid leaching from ash and from SCWO residue. The difference in composition of ash and sludge residue samples had no significant influence on release of phosphate at high concentrations of acid. Phosphate release from ash, dried sludge at 300 degrees C and SCWO residue showed similar results at 1M acid leaching. However, it seems to be easier to release phosphate from the SCWO residue than from the ash at low acid concentrations. SCWO residue showed higher release than the other ashes at 0.5M HCl. Results for alkaline leaching showed higher release from ash at 1M NaOH than from SCWO residue or from dried sludge at 300 degrees C. The leaching of phosphate from dried sludge seems to be temperature dependent, as the dried sludge treated at higher temperature showed less release of phosphate. It was found that the pre-treatment of the ash may be important for better release of phosphate.
5)J Environ Sci Health A Tox Hazard Subst Environ Eng. 2006;41(8):1559-68.
Destruction of OPA from munitions demilitarization in supercritical water oxidation: kinetics of total organic carbon disappearance.
The destruction of OPA from munitions demilitarization has been accomplished in supercritical water oxidation (SCWO) with oxygen as oxidant in an isothermal continuous-flow reactor. The experiments were conducted at a temperature of 689-887 K and a fixed pressure of 25 MPa, with a residence time that ranged from 7 s to 14 s. The destruction efficiency was measured by total organic carbon (TOC) conversion. At the reaction condition, the initial TOC concentrations of OPA were varied from 1.41 mmol/L to 19.57 mmol/L and the oxygen concentrations were varied from 15.03 mmol/L to 81.85 mmol/L. Experimental data showed that all the TOC conversions were >80% under the above experimental conditions. The kinetics of TOC disappearance, which is essential for the design, optimization, and control of reliable commercial SCWO reactor was developed by taking into account the dependence of the oxidant and TOC concentration on the reaction rate. A global TOC disappearance rates expression was regressed from the data of 38 experiments, to a 95% confidence level. The resulting activation energy was determined to be 44.01 +/- 1.52 kJ/mol, and the pre-exponential factor was (1.67 +/- 0.45) x 10(2) L(1.14) mmol(-0.14) s(-1). The reaction orders for the TOC and the oxidant were 0.98 +/- 0.01 and 0.16 +/- 0.02, respectively.
6)The Journal of Supercritical Fluids
Volume 37, Issue 1 , February 2006, Pages 94-101
Supercritical water oxidation of o-dichlorobenzene: degradation studies and simulation insights
Abstract
Supercritical water oxidation (SCWO) of an aromatic chlorinated species, o-dichlorobenzene (o-DCB), is studied using a tubular flow reactor. o-DCB is often found in chemical waste streams and is similar to polychlorinated biphenyls (PCBs), an acute environmental hazard, in its physical–chemical properties. The experiments focus chiefly on the effect of temperature on the degradation efficiency of the SCWO process. Experiments are also performed for subcritical conditions. Molecular Dynamics simulations of OH radical and phenol in water are carried out in order to estimate the diffusion-controlled limit of the reaction between aromatic species and hydroxyl radical in aqueous solution. It is speculated that high diffusivity of the reacting species is a major factor responsible for high degradation efficiency of oxidation reactions in supercritical water.
7) Solid State Communications
Volume 138, Issue 6 , May 2006, Pages 314-317
High Curie temperature in B-site ordered Sr₂CrWO₆ epitaxial thin films
^aDepartment of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK
^bDepartment of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 3QZ, UK
^cCentre for Science at Extreme Conditions and School of Chemistry, University of Edinburgh, King's Building, Mayfield Road, Edinburgh EH9 3JZ, UK
Received 15 December 2005;  accepted 26 January 2006.  by T.T.M. Palstra.  Available online 14 February 2006.
Abstract
Epitaxial and c-axis oriented double perovskite Sr₂CrWO₆ thin films were prepared on SrTiO₃ (100) and LaAlO₃ (100) substrates by pulsed-laser deposition. Structural, magnetic and transport properties were found to be sensitive to the gas conditions employed during the deposition. A small amount of oxygen along with Ar during the deposition was found to be essential for B-site ordering; such films displayed lattice parameters close to the bulk value and display ferromagnetic metallic behavior. The Curie temperature observed above 500 K in these films is higher than bulk Sr₂CrWO₆ samples. Films grown without oxygen were observed to have long c-parameter and no B-site ordering; they were non-magnetic and semiconducting.
8)Water Research
Volume 40, Issue 11 June 2006, Pages 2093-2112
Review
A review of secondary sludge reduction technologies for the pulp and paper industry
^aPaprican, 570 St. John's Boulevard, Pointe-Claire, Que., Canada H9R 3J9
Received 20 April 2004;  revised 14 April 2005;  accepted 4 April 2006.  Available online 15 May 2006.
Abstract
The broader application of the activated sludge process in pulp and paper mills, together with increased production, have amplified sludge management problems. With sludge management costs as high as 60% of the total wastewater treatment plant operating costs, and increasingly stringent environmental regulations, it is economically advantageous for pulp and paper mills to reduce their biosolids production. In order to provide a state-of-the-art review of secondary sludge reduction technologies, we have considered the scenarios of lower sludge production through process modifications, and waste-activated sludge reduction through post-treatment. A critical evaluation of all candidate reduction technologies indicates that sludge reduction through treatment process changes appears more appealing than post-treatment alternatives. The former approach offers a clear advantage over the latter in that the treatment process changes reduce sludge production in the first place, thus decreasing sludge management cost. Although it is technically feasible to eliminate the need for sludge disposal, it is unlikely to be economically feasible at this time.
9) Applied Thermal Engineering
Volume 26, Issue 13 , September 2006, Pages 1339-1344
Recent advances on heat, chemical and process integration, multiobjective and structural optimisation
Abstract
This editorial is introducing and providing an overview of a special issue dedicated to the 7th conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction—PRES 2004. It contains six selected papers covering various fields of applied thermal engineering focusing on recent development of various different features of heat, chemical and process integration in various applications ranging from natural gas and CO₂ capture, through heat-integrated distillation columns, multipurpose batch plants to steel production. Another four selected papers are presenting novel approaches multiobjective and structural optimisation of pulp and paper industry, distributed and district heating, thermal sludge processing and fuel cells applications.
10)The Journal of Chemical Physics -- 14 January 2006
J. Chem. Phys. 124, 024507 (2006) (9 pages)
Spatial hydration structures and dynamics of phenol in sub- and supercritical water
The hydration structures and dynamics of phenol in aqueous solution at infinite dilution are investigated using molecular-dynamics simulation technique. The simulations are performed at several temperatures along the coexistence curve of water up to the critical point, and above the critical point with density fixed at 0.3  g/cm³. The hydration structures of phenol are characterized using the radial, cylindrical, and spatial distribution functions. In particular, full spatial maps of local atomic (solvent) density around a solute molecule are presented. It is demonstrated that in addition to normal H bonds with hydroxyl group of phenol, water forms -type complexes with the center of the benzene ring, in which H₂O molecules act as H-bond donor. At ambient conditions phenol is solvated by 38 water molecules, which make up a large hydrophobic cavity, and forms on average 2.39 H bonds (1.55 of which are due to the hydroxyl group-water interactions and 0.84 are due to the complex) with its hydration shell. As temperature increases, the hydration structure of phenol undergoes significant changes. The disappearance of the -type H bonding is observed near the critical point. Self-diffusion coefficients of water and phenol are also calculated. Dramatic increase in the diffusivity of phenol in aqueous solution is observed near the critical point of simple point-charge-extended water and is related to the changes in water structure at these conditions. ©2006 American Institute of Physics
11)Journal of Electrostatics
Volume 64, Issue 6 , June 2006, Pages 416-421
Decoloration of azo dye by a multi-needle-to-plate high-voltage pulsed corona discharge system in water
^aSchool of Environmental and Biological Science and Technology, Dalian University of Technology, Dalian 116024, PR China
^bInstitute of Electrostatics and Special Power, Dalian University of Technology, Dalian 116024, PR China
 Abstract
The decoloration efficiency of azo dye (Acid Orange 7, AO7) using a multi-needle-to-plate high-voltage pulsed corona discharge system was investigated in this paper. The effect of several parameters, including peak pulse voltage and pulse frequency of the discharge system, initial pH and electrical conductivity of the dye solution, mode of needle electrode distribution and gas flow rate on the decoloration rate of the dye wastewater was reviewed. The results obtained show that the pulsed discharge system with a multi-needle-to-plate electrode could dispose azo dye wastewater efficiently. The decoloration rate increased with an increase in applied peak pulse voltage and pulse frequency. Decoloration was more efficient in the acidic solution, and the decoloration rate displayed no marked change under solutions of differing electrical conductivity. For the case in which we example the effect of gas flow rate on the decoloration efficiency of Acid Orange solution, we found that better decoloration efficiency occurred using the seven-needle-to-plate discharge system, which had more discharge anodes.
12)Fuel
Volume 85, Issue 3 , February 2006, Pages 367-373
Catalytic denitrogenation of hydrocarbons through partial oxidation in supercritical water
Abstract
In this work, the denitrogenation of hydrocarbons under supercritical water oxidation environment was investigated in a rotated bomb reactor at 623–723 K and 25–35 MPa over sulfided NiMo catalyst. Quinoline was used as a model nitrogen-containing compound. A high reduction of total nitrogen up to about 85% was obtained. The denitrogenation pathway is composed of two consecutive steps: in situ H₂ generation and the hydrogenation of quinoline. The hydrogenation mechanism of quinoline varies with reaction temperature because of the participation of supercritical water in HDN step. The strong adsorption of quinoline and its hydrogenation intermediates on catalyst surface has an adverse influence on total nitrogen reduction rate.

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