Showing papers on "Wet oxidation published in 1993"

Two-stage subcritical-supercritical wet oxidation

Abstract: A two-stage wet oxidation process for COD removal from high strength wastewater is disclosed. The wastewater stream is treated in a first stage subcritical wet oxidation zone at temperatures between about 250° and 374° C. to remove a substantial portion of the COD. Subsequently, all or a portion of the first stage oxidized waste stream is treated in a second stage supercritical wet oxidation zone at temperatures of 374° to about 600° C. to remove any remaining COD content. Both stages of wet oxidation treatment are carried out at essentially the same system pressure.

Wet oxidation of aqueous streams

Abstract: This invention relates to improved wet oxidation process for the destruction of organic components in a wastewater stream contaminated with inorganic salts. In wet oxidation, the wastewater stream is contacted with an oxygen-containing water stream at elevated temperatures and pressures. The improvement for treating aqueous wastewater streams contaminated with inorganic salts wherein the organic contaminants are present in an amount from about 0.5 to 2% by weight resides in oxidizing the organic components in a tubular reactor at a temperature ranging from 325° C. to not more than 370° C. and a pressure ranging from 220 to 345 bar. The oxidation reaction is carried out in a reaction time of 5 minutes or less.

Wet oxidation of nitrotoluenesulfonic acid: some intermediates, reaction pathways, and byproduct toxicity

Abstract: Wet air oxidation (WAO) is effective in the oxidation of 5-nitro-o-toluenesulfonic acid (NTSA); the WAO reaction is first-orde rwith respect to NTSA. Sulfur intially present is almost stoichiometrically converted to sulfate. A significant amount of nitrogen gas and ammonium are present in the reactor off gas and WAO effluent, respectively. No NO x or SO x is detected. Proposed reaction pathways are presented for the WAO of NTSA, based on the intermediates and end products identified. NTSA concentration up to 150 mg/L does not show inhibitory effects on enriched Nitrosomonas. However, WAO-treated NTSA does show some adverse effect on the nitrite production capability of the Nitrosomonas, thus indicating that same byproducts formed during WAO of NTSA may be more toxic than NTSA itself

Low temperature caustic sulfide wet oxidation process

Abstract: A process for treatment of caustic sulfide liquor by wet oxidation in a ferrous-based alloy system at temperatures less than about 175° C. is described. The liquor is first analyzed for alkalinity consuming species and for nonsulfidic alkalinity. If excess alkalinity consuming species is present compared to nonsulfidic alkalinity, then additional nonsulfidic alkalinity is added to the raw liquor such that excess alkalinity is present during wet oxidation treatment, thus preventing excessive corrosion to the ferrous-base alloy system.

Wet air oxidation of trinitrotoluene manufacturing red water

Abstract: An effective use of the wet air oxidation (WAO) process at a temperature of 340°C and 0.8 MPa P O2(25°C) to treat diluted trinitrotoluene (TNT) red water was previously demonstrated. This study presents the results of a 1-hour WAO of red water at temperatures ranging from 200° to 320°C, and P O2 from 0.13 to 1.31 MPa, in terms of contaminant reduction and intermediate appearance. Also, comparison is made between the toxicity of the raw and the WAO-treated red water on two biological systems. Results show the WAO removal efficiency to be a function primarily of temperature and, to a lesser extent, of P O2 . Acetic acid and 1,3-dinitrobenzene (DNB) accumulated at lower temperatures

Nitrotoluenesulfonic acid : UV, IR, and NMR properties and rate studies of wet air oxidation

Abstract: Environmental fate of aromatic sulfonates is relatively unknown. We report the findings of wet air oxidation (WAO) of several sulfonic compounds, specifically 5-nitro-o-toluenesulfonic acid (NTSA). WAO is effective in the oxidation of NTSA, a compound similar in structure to dinitrotoluenesulfonates which are major components of TNT red water. The WAO reaction is first-order with respect to NTSA; the order with respect to oxygen pressure is 0.6. The activation energy is approximately 21 kcal/mol. The reaction rate is significantly enhanced with the addition of 5 mg/L Cu(II) catalyst. The effect of initial pH on rate of NTSA oxidation is complex. Higher reaction rates are observed both at low and high pH's, with a better overall rate being achieved at low pH. Some properties of NTSA (e.g., UV, IR, and NMR) were obtained to provide additional information

Cross-flow filtration apparatus and method

Abstract: Apparatus and methods utilizing cross-flow filtration under supercritical conditions for water to separate/filter a feed stream or reaction mixture, remove oxides or other solids from fluids, and/or separate ion species (e.g., ions, electrolytes, or salts). Cross-flow filtration may be utilized in combination with wet oxidation of waste and wastewaters to remove organic and inorganic materials.

Method for co-processing organic wastes and spent nitric acid wash water

Abstract: A process is disclosed for co-processing spent nitric acid wash water with organic or biological wastes under wet oxidation conditions whereby the nitrogen content of the waste and the chemical oxygen demand and the nitrogen content of the nitric acid wash water and of the organic or biological wastes are significantly reduced. The nitric acid wash water is the waste stream generated by descaling wet oxidation reactors used for the treatment of organic or biological wastes, especially municipal wastes. The process of this invention can be carried out in conventional above ground equipment or in a subterranean, down-hole reactor having a vertical configuration which utilizes gravitational forces to provide a high pressure reaction environment. The nitric acid wash water and organic wastes are reacted with an oxidant at a temperature greater than 150° C. and a pressure suffient to keep water in the liquid state. The nitric acid wash water is mixed with the organic waste or is introduced through the oxidant (preferably gaseous oxygen) inlet in such a manner that gas with water vapor and the remaining acid provides a liquid film so there are essentially no "dry spots" in the oxidant inlet lines.

Investigation of the oxidation kinetics of CoSi2 on (111)Si by transmission electron microscopy

Abstract: Transmission electron microscopy has been applied to study oxidation kinetics of CoSi2 on silicon for both dry and wet oxidation. Care was taken to determine the activation energies of oxidation in the temperature and time regime where the islanding of CoSi2 does not occur. For dry oxidation, activation energies for parabolic and linear growth were found to be 1.91 and 2.01 eV (±0.1 eV), respectively. For wet oxidation, activation energies for parabolic and linear growth were found to be 1.75 and 1.68 eV (±0.1 eV), respectively. The activation energy of the parabolic rate constant is substantially different from those obtained previously. The difference is attributed to the occurrence of islanding during oxidation in the previous study. A comparison of oxidation kinetics of CoSi2, NiSi2, TiSi2 on silicon with pure silicon substrates indicated that the oxidation kinetics are practically the same for CoSi2 and NiSi2 in the parabolic growth regime, but substantially different from those of TiSi2 on silicon a...

Wet oxidation of ammonium salt containing liquors

Abstract: This is a process for wet oxidation of an ammonium salt containing waste liquor which prevents plugging of the vapor-carrying lines of the wet oxidation system. The vapor-carrying lines are maintained in an unobstructed condition by adding sufficient liquid water to dissolve condensed ammonium salt which can plug these lines. This provides for safe operation of the wet oxidation system.

Wet oxidation system—process concept to design

Abstract: A wet oxidation process was developed to treat waste water from an organic nitration process. The waste water contained EPA listed priority pollutants including dinitrotoluene, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 4,6-dinitro-ortho-cresol and phenol. The process design was based on experimental data generated in both batch and continuous laboratory and pilot scale reactors and in cooperation with university researchers, a private development company and an engineering company. Process variables included temperatures between 250 and 500 C, pressures in the 23,000–28,000 kPa (3,450–4,000 psi) range and residence times between 1 and 7 minutes. The final design was a tubular reactor operating at temperatures slightly below the critical temperature for water and short residence times. Destruction efficiencies for most of the priority pollutants were greater than 99% and final concentrations were below those specified by EPA regulations.

Method of preparing antimony doped semiconductor with intrinsic gettering

Abstract: A method of preparing semiconductor wafers with intrinsic gettering capability, comprises the steps of: carrying out a high temperature wet oxidation on a doped semiconductor wafer for between about 20 to 60 minutes to form an initial oxidation layer; heating said wafer at a moderate temperature in an inert atmosphere for about 1 to 4 hours to initiate formation of crystal nuclei; ramping up the temperature in said inert atmosphere to a temperature of at least about 850° C. at a rate of about 1°-10° C./min.; and subsequently carrying out well diffusion on the wafer at a temperature of at least about 1000° C.

Treatment of high concentration ammonia waste liquid

Abstract: PURPOSE:To provide a method for treating various kinds of high concentration ammonia waste waters which is desirable viewed in the light of environment and heat balance and whose treatment efficiency is high and which is easily put to practical use when a high concentration ammonia waste liquid is treated. CONSTITUTION:A zeolite regeneration 38 or a sewage sludge dehydration filtrate 43 which is a high concentration ammonia waste liquid is mixed with sewage sludge 42 by an appropriate amount, and catalytic wet oxidation treatment is applied to the minute to remove ammonia. This method is made fundamental. Besides, a method where both electrodialysis treatment and ammonia stripping treatment are jointly used and a method where after a soluble magnesium salt or a soluble cobalt salt is added to adjust the liquid to pH 8-10, a soluble phosphate is added by an appropriate amount and mixed, causing crystallization where ammonia in the solution is crystallized as insoluble crystal to be performed, allowing the crystal to be removed by sedimentation and separation are provided.

Influence of Surface Oxides of Carbonaceous Adsorbent on Liquid-Phase Desorption Characteristics of Aromatic Compound

Abstract: The influence of surface oxides of carbonaceous adsorbent on the liquid-phase desorption characteristics of aromatic compounds was experimentally determined. Although the amount adsorbed on activated carbon, graphite and activated carbon fiber is decreased by wet oxidation, the desorption characteristics are improved. Ethanol regeneration was applied to oxidized carbon and carbon fiber. Ethanol gives the high regeneration ratio for the compounds substituted by electron-attacking groups. However, the regeneration ratio by ethanol is low for the compounds substituted by electron-donating groups. It was found that the regeneration ratio by ethanol is improved by wet oxidation except adsorption of amino compounds.

Wet oxidation of non water – soluble polymers

Abstract: Wet oxidation is beginning to be used world‐wide to treat organic liquid municipal and industrial wastes. As the degradation of plastics is an environmental concern, the objective of this study is to determine the ability of wet oxidation to oxidize solid wastes such as polystyrene or polyethylene. Oxidation efficiency is found to depend on temperature, residence time and to a lesser extent on the initial oxygen pressure. A COD reduction close to 100% is obtained after four hours of reaction at 320°C or after one hour at 280°C with a catalyst. During degradation, there is formation of a refractory intermediate: acetic add, which limits the oxidation rate. Its concentration could be reduced by raising the temperature or by using a catalyst which inhibits its production.

Process for the recovery of processing chemicals from the black liquor in the production of cellulose by organo-solvent processes

Abstract: In order to recover inorganic chemicals from waste liquors in cellulose manufacturing processes it is proposed to separate the alkali or alkaline earth from the organic components by partial or complete oxidation in the aqueous phase with air and/or oxygen. Before this oxidation process, it is possible to separate the lignin in the black liquor by acidification and precipitation with a mineral acid, the resins by extraction and the demi-celluloses by ultra-filtration, whereupon the residual organic substances still remaining in solution are oxidised. Wet oxidation is possible such that the carboxylic acids, especially the acetic acid, is not burned as well and can be separated by crystallisation after caustification. The chemical solution thus freed of organic substances can be returned to the liquor by caustification and made available in the cellulose production cycle.

Method and system for oxidation processing

Abstract: PURPOSE: To provide method and system for allowing wet oxidation processing under reduced pressure. CONSTITUTION: The oxidation processing system comprises a furnace 1 for oxidizing an object W under high temperature, means 13 for reducing the pressure in the furnace 1, a burner 23 disposed on the outside of the furnace 1 in order to burn hydrogen gas and oxygen gas to produce steam, a steam supply line 24 communicating the burner 23 and the furnace 1, and a throttling section 46 provided in the steam supply line 24 in order to produce pressure difference between the burner 23 side and the furnace 1 side. This structure ensures stabilized combustion in the burner 23 thus allowing wet oxidation under reduced pressure. COPYRIGHT: (C)1995,JPO

Purification of salt containing waste water by wet oxidation at supercritical conditions

Abstract: In the process according to the invention for the purification of salt-laden waste water by wet oxidation of organic constituents at supercritical conditions, the reaction is carried out in the form of a flame (5). The supercritical zone is enclosed by a subcritical jacket stream (4) formed from cooling water. At one end of the reactor (1) designed as a cylindrical pressure vessel at least one burner nozzle (2) and at least one annular cooling water feed position (48) surrounding the burner nozzle are provided; at the other end, at least one collective exit position (160) for cooling water, reaction products and, in particular, precipitated salts are arranged. Because of the jacket stream, there are no blockages due to salts; corrosion problems are substantially neutralised.

Two-stage wet oxidation process for treating wastewater

Abstract: A two-stage wet oxidation process for COD removal from high strength wastewater is disclosed in which the wastewater stream (10) is treated in a first stage subcritical wet oxidation zone (20) at temperatures between about 250o and 374oC to remove a substantial portion of the COD, and, subsequently, all or a portion of the first stage oxidized waste stream is treated in a second stage supercritical wet oxidation zone (28) at temperatures of 374o to about 600oC to remove any remaining COD content. Both stages of wet oxidation treatment are carried out at essentially the same system pressure.

Formation of Germanium Dioxide During Wet Oxidation of Si0.5 Ge0.5 Alloy

Abstract: The oxidation of Si 0.5 Ge 0.5 alloy has been investigated over the temperature range 800 to 1000°C . The composition of the oxide layers has been determined by 1.5 MeV Rutherford backscattering spectroscopy (RBS), infrared transmission spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). During the initial stage of oxidation, as the temperature ramps up in an oxidising ambient both Si and Ge are oxidized to form a mixed oxide in the region near the surface. Upon further oxidation, at temperatures higher than 900°C and times longer than 5 minutes, the Ge atoms are ejected by the growing oxide layer, which has the composition of Si0 2 , and accumulate in the underlying alloy, which becomes rich in Ge.The surface oxide layer remains unchanged. The proportion of Ge0 2 in the near surface region, determined from IR spectra, decreases when the temperatures increases from 800°C to 1000°C. It is concluded that at 800°C Ge atoms are insufficiently mobile to be ejected from the growing oxide and both matrix species ( Si and Ge ) have equal probabilities of oxidation leading to the formation an oxide of composition Si 0.5 Ge 0.5 O 2 . Supporting experiments confirm that Ge0 2 in the surface layer is formed during warm up of the samples oxidized at 900 and 1000°C.

Treatment for waste water containing inorganic sulfur-containing compound

Abstract: PURPOSE:To make highly harmless the sulfur component contained in waste water by a simple process wherein waste water containing a compound containing inorg. sulfur whose apparent oxidation number is below +6 is subjected to wet oxidation using molecular oxygen at 350 deg.C or lower under pressure holding a liquid phase. CONSTITUTION:The pressure of waste water sent from a line 8 is raised to 9kg/cm and air supplied from a line 9 is raised in pressure by a compressor 5 to be mixed with the waste water in a ratio of O2/TOD=1.2. This gas-liquid mixture is heated to 150 deg.C by a heat exchanger 2 through a line 10 and introduced into a wet oxidizing tower 1 to be subjected to oxidation treatment. The treated water is cooled by the heat exchanger 2 through a line 11 to enter a gas-liquid separator 4 and held to a constant level and pressure by a liquid level controller LC and a pressure controller PC. As a result, treated water wherein CODCr is 5200mg/l or less, sulfide sulfur is 600mg/l or less and a thiosulfate ion is 3000mg/lor less is obtained.

Treatment of waste water containing metal cyan complex ion

Abstract: PURPOSE:To perfectly and inexpensively decompose cyan by subjecting a cyan compd., a nitrogen compd. or the like in waste water to wet oxidation treatment in the presence of oxygen and separating and removing sludge and/or metal components from the treated soln. and adding sulfuric acid, sulfur or the like to the treated soln. before applying wet oxidation treatment thereto. CONSTITUTION:The cyan-containing waste water from a waste water storage tank 1 is mixed with the oxygen-containing gas from a compressor 22 to be supplied to a primary reaction tower 5. The quantity of oxygen added to this waste water is set to below theoretical oxygen quantity necessary for decomposing a cyan compd., a nitrogen compd. or the like into harmless products. The treated soln. issued from the reaction tower 5 is sent to a gas-liquid separator 6 through a heat exchanger 3 and a cooling tower 7 and the separated liquid phase component 10 is separated into a primary treated soln. 12 and a solid 3 by a solid-liquid separator 11 and a part of the primary treated soln. 12 is allowed to meet with the treated soln. of the reaction tower 5 and the remainder thereof is sent to an intermediate storage tank 16 and mixed with sulfuric acid supplied from a sulfuric acid storage tank 14. The resulting soln. mixed with oxygen-containing gas is sent to a secondary reaction tower 20 packed with a catalyst and subjected to wet oxidation treatment.

Development of the Monolith Froth Reactor for Catalytic Wet Oxidation of CELSS Model Wastes

Abstract: The aqueous phase oxidation of acetic acid, used as a model compound for the treatment of CELSS (Controlled Ecological Life Support System) waste, was carried out in the monolith froth reactor which utilizes two-phase flow in the monolith channels. The catalytic oxidation of acetic acid was carried out over a Pt/Al2O3 catalyst at temperatures and pressures below the critical point of water. The effect of externally controllable parameters (temperature, liquid flow rate, distributor plate orifice size, pitch, and catalyst distance from the distributor plate) on the rate of acetic acid oxidation was investigated. Results indicate reaction rate increased with increasing temperature and exhibited a maximum with respect to liquid flow rate. The apparent activation energy calculated from reaction rate data was 99.7 kJ/mol. This value is similar to values reported for the oxidation of acetic acid in other systems and is comparable to intrinsic values calculated for oxidation reactions. The kinetic data were modeled using simple power law kinetics. The effect of "froth" feed system characteristics was also investigated. Results indicate that the reaction rate exhibits a maximum with respect to distributor plate orifice size, pitch, and catalyst distance from the distributor plate. Fundamental results obtained were used to extrapolate where the complete removal of acetic acid would be obtained and for the design and operation of a full scale CELSS treatment system.

Nanometer-Scale Oxide Particles in Gesi Films Grown by Wet Oxidation

Abstract: Amorphous GeSi films with different thicknesses and oxygen contents were electron beam evaporated onto Si(100) wafers and wet oxidized at 900 °C for 30 min. If there was no oxygen in the as-deposited film, an epitaxial GeSi film would be grown after wet oxidation. For the samples with oxygen, epitaxial growth broke down when the thickness of the epitaxy exceeded about 200 A and polycrystalline GeSi films were formed. A dedicated STEM (scanning transmission election microscope) was used to characterize the sample after oxidation. STEM BF (bright field), ADF (annular dark field), and energy filtered images revealed the presence of small oxide particles in the polycrystalline GeSi films. X-ray microprobe analysis with a windowless detector was employed to identify the oxide particles. The failure of the epitaxy is explained by the random nucleation and growth of GeSi grains on the oxide particles.