Supercritical water oxidation products

Reaction vessels for supercritical water oxidation must be highly corrosion resistant because of the aggressive nature of supercritical water and oxidation reaction products at extreme temperatures and pressures. Supercritical oxidation of PCBs and some chlorinated hydrocarbons can be difficult... 

Hydrothermal oxidation (HO) [also called supercritical water oxidation (SeWO)] is a reactive process to convert aqueous wastes to water, CO2, O2, nitrogen, salts, and other by-products. It is an enclosed and complete water treatment process, making it more desirable to the public than incineration. Oxidation is rapid and efficient in this one-phase solution, so that wastewater containing 1 to 20 wt % organics may be oxidized rapidly in SOW with the potential for higher energy efficiency and less air pollution than in conventional incineration. Temperatures range from about 375 to 650°C and pressures from 3000 to about 5000 psia. 

Figure ES-2 is a block diagram of the Eco Logic technology process. The primary treatment destroys the agent and the energetic materials by hydrolysis with caustic or water. Flowever, the hydrolysis products (hydrolysates) must be further treated prior to final disposal. For this secondary step, Eco Logic proposes to use a transpiring-wall supercritical water oxidation (SCWO) reactor design. The following major operations are included ...

Reviewed previous SCWO research with model pollutants and demonstrated that phenolic compounds are the model pollutants studied most extensively under SCWO conditions Studied supercritical water oxidation of aqueous waste Explored reaction pathways in SCWO of phenol Studied catalytic oxidation in supercritical water Explored metal oxides as catalysts in SCWO Studied decomposition of municipal sludge by SCWO Investigated the SCWO kinetics, products, and pathways for CH3- and CHO-substituted phenols Determined oxidation rates of common organic compounds in SCWO... 

Martino, C.J. and Savage, P.E., Supercritical water oxidation kinetics, products, and pathways for CH3 and CHO-substituted phenols, Indust. Eng. Chem. Res., 36, 1391-1400, 1997. 

Radio frequency heating, 500 Steam stripping, 500 Vacuum extraction, 500 Aeration, 501 Bioremediation, 501 Soil flushing/washing, 502 Surfactant enhancements, 502 Cosolvents, 502 Electrokinetics, 503 Hydraulic and pneumatic fracturing, 503 Treatment walls, 505 Supercritical Water Oxidation, 507 Solid Solution Theory, 202 Solubility products, 48-53 Metal carbonates, 433-434 Metal hydroxides, 429-433 Metal sulfides, 437 Sorption, 167 See Adsorption Specific adsorption, 167 See Chemisorption Stem Layer, 152-154 Sulfate, 261... 

More polymerization reactions carried out at supercritical conditions, select biomass conversion supercritical fluid technologies for hydrogen production, wider use of supercritical water oxidation processes, portfolio of self-assembly applications, a spate of opportunities in process intensification, many supercritical fluid aided materials synthesis applications, and numerous reactions for synthesis of specialty chemicals are expected for years to come. 

A variety of chemical and biological reactions involving supercritical fluid technology are being explored and developed. They include polymerization reactions, biomass conversion, hydrogen production, applications of supercritical water oxidation, self-assembly applications, synthesis of specialty chemicals, manufacture of materials with tailored properties, and much more. These developments and new ones are expected to mature and be commercially deployed in years to come. 

The aim of supercritical water oxidation is to have complete oxidation, with no products of incomplete combustion remain in solution. 

It would be particularly useful with a feed consisting of products from a previous detoxification step the detoxified material would be in dilute aqueous solution, the form required for supercritical water oxidation. 

The reaction is carried out in a 0.478 cm i.d. Inconel 625 reactor at 960 to 1,100 bar and 380° to 450°C with approximately one minute of residence time. Treatment at these conditions is often called supercritical water oxidation (SCWO) however, since the critical parameters of the PBX-9404 hydrolysis product mixture are unknown, the treatment may or may not be above the critical parameters for the hydrolysate. Therefore, the more general term hydrothermal treatment is used in this case. 

By using an excess of water, also reaction products of a supercritical water oxidation can be forecast. 

The calculations have been done not only for stoechiometric combustion conditions, but also for negative oxygen balances, which are relevant for partial combustion conditions and for thermal decomposition reactions. By taking into account an excess of water, also the reaction products of a supercritical water oxidation can be calculated. 

Critical curves in water-salt system are extended usually toward temperatures higher than the critical temperature of water hence a high-temperature shift of immiscibility region upon addition of salt is a common phenomenon. It was mentioned in (Krader and Franck, 1987 Smits et al., 1997b,c) that this phenomenon is similar to the salting-out effect of ions observed in water-nonpolar gases mixtures at ambient conditions, and the electrolytes could be regarded as an anti-solvent for the volatile reactants and reaction products in supercritical water oxidation processes. 

Ding, Z., Aki, S. and Ahraham, M. (1995). Catalytic supercritical water oxidation Phenol conversion and product selectivity. Environ. Sci. TechnoL, 29, pp. 2748-2753. 

Lin, K. and Wang, H. (1999). Shape selectivity of trace by-products for supercritical water oxidation of 2-chlorophenol effected by CuO/ZSM-48, Appl. Catal. B Environ, 22, pp. 261-267. 

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