Showing papers on "Wet oxidation published in 1992"

Chloride interference in the analysis of dissolved organic carbon by the wet oxidation method

Abstract: The presenoe of Cl - in concentrations greater than 0.02 M is shown to interfere with the analysis of aqueous DOC concentrations by the wet oxidation method of analysis when a reaction time of 5 min is employed. Chloride competes with DOC for S 2 O 8 2- lowering the overall oxidation efficiency. The resulting HOCl from the oxidation of Cl - reacts with DOC, producing significant amounts of chlorinated intermediate compounds in addition to CO 2 .

Wet oxidation of GeSi at 700 °C

Abstract: About 500‐nm‐thick films of Ge0.36Si0.64 and Ge0.28Si0.72 grown epitaxially on (100)Si have been oxidized at 700 °C in wet ambient. A uniform GexSi1−xO2 oxide layer forms with a smooth interface between it and the unoxidized GexSi1−x layer below. The composition and structure of that layer remains unchanged as monitored by backscattering spectrometry or cross‐sectional transmission electronic microscopy. The oxide of both samples grows as square root of oxidation duration. The parabolic rate constant increases with the Ge content and is larger than that for wet oxidation of pure Si at the same temperature. The absence of a regime of linear growth at this relatively low temperature indicates a much enhanced linear rate constant.

Process for treatment of wastewater containing inorganic ammonium salts

Abstract: A process for treating an aqueous wastewater containing ammonium compounds. The process comprises the steps of preheating a liquid influent and introducing the preheated influent, an oxygen-containing gas an the wastewater into a reaction vessel for undergoing wet oxidation. An oxidized effluent is then withdrawn from the reaction vessel, which includes a gas phase containing ammonia and carbon dioxide and a liquid phase containing the ammonium compounds. The temperature of the effluent is then reduced to a temperature sufficient to condense a substantial portion of the ammonia into the liquid phase, and afterwards the remaining gas phase containing a substantial portion of the carbon dioxide is separated from the resulting liquid phase. Either prior to or subsequent to the separation the pH of the liquid phase is adjusted to a level whereby a substantial portion of the ammonia remains in the liquid phase when the liquid phase is subsequently subjected to an elevated temperature above the boiling point of water and the water content of the pH-adjusted liquid phase is then reduced by evaporation.

Wet oxidation process for ACN waste streams

Abstract: A process is disclosed which limits the corrosion of the materials of construction of a wet oxidation system treating wastewaters. The process is particularly useful in the wet oxidation treatment of ammonium sulfate containing wastes such as acrylonitrile wastewaters. The wastewater is mixed with an oxygen containing gas such that a substantial residual oxygen gas concentration is maintained from before the stream-gas mixture is heated for wet oxidation until after the oxidized stream-gas mixture is cooled and separated. Preferably, in the treatment of acrylonitrile waste water the shutdown procedure comprises cooling said waste stream by introducing an aqueous liquid substantially free of organic impurities and containing a basic material.

Spent caustic treatment

Abstract: A process is provided for treating a sulfide-containing alkaline aqueous effluent to improve its environmental acceptability, which comprises: (a) intimately mixing a water-immiscible solvent, such as a pyrolysis gasoline, therewith for a sufficient time to extract polymerizable hydrocarbon compounds and/or other compounds which may cause fouling of downstream plant, (b) allowing the solvent phase and the aqueous phase to separate, (c) removing the solvent phase, and (d) subjecting the separated aqueous phase to an oxidation treatment which oxidizes sulfide ions to environmentally acceptable sulfur acid ions, particularly sulfate ions, e.g. a wet air oxidation process. The invention has been particularly developed for treating spent caustic which has been used to scrub gases produced by cracking for ethylene production. Such effluents have been found to cause fouling of the oxidation plant and the Applicants have found that this is due to polymerizable hydrocarbons. Furthermore they have found that prolonged contact times between a readily available solvent and the effluent can ensure that the fouling problem is cured.

Oxidation behaviour of the sintered Si3N4-Y2O3-Al2O3 system

Abstract: The oxidation behaviour of silicon nitride composed of Si3N4, Y2O3, Al2O3, AlN and TiO2 was investigated in dry and wet air at 1100–1400 °C. The oxidation rates were confirmed to obey the parabolic law. An activation energy of 255 kJ mol−1 was calculated from the Arrhenius plots of the results of oxidation in an air flow. In still air the oxidation rate was larger than that in an air flow, but the oxidation rate in flowing air was not affected by the air flow rate. α-cristobalite and Y2O3·2SiO2 were formed in oxidized surface layers. These crystal phases increased with increasing oxidation temperature. In particular, a higher content of α-cristobalite was obtained in still air oxidation. The existence of water vapour in flowing air greatly promoted the oxidation.

Corrosion control for wet oxidation systems

Abstract: A process for controlling corrosion in a wet oxidation system by controlling the operating pH range within the system is described. A pH operating range is selected within which corrosion to the wet oxidation system is minimized. The pH within the wet oxidation system is monitored and a pH adjusting material is added to the waste material being treated to maintain the system pH within the selected pH operating range, thus minimizing corrosion.

Wet oxidation of amorphous Si‐Ge layer deposited on Si(001) at 800 and 900 °C

Abstract: Amorphous Si0.56G0.44 films were deposited on (001)Si by electron beam evaporation in a vacuum having a base pressure of 10−7 Torr. They were then wet oxidized at 800 and 900 °C in an open tube furnace for various times. Cross (x)‐sectional and plan view transmission electron microscope techniques were employed to characterize the samples. At 800 °C, 30 min of wet oxidation produced a continuous polycrystalline Si‐Ge layer, whereas 60 min of wet oxidation produced a discontinuous polycrystalline layer. After 100 min of wet oxidation at 800 °C, the Si‐Ge layer was almost completely oxidized and no observable evidence of the epitaxial Si‐Ge layer was found. Wet oxidation at 900 °C for 10 min produced a bilayer structure; one epitaxial and one polycrystalline layer separated by a contamination layer initially present on the substrate prior to deposition. A mostly epitaxial Si‐Ge layer was obtained after 30 min of wet oxidation at 900 °C. These results will be discussed in terms of a previously suggested epit...

High temperature wet oxidation using sintered separators

Abstract: A system for effective utilization of reaction heat and in sit separation of solid and gaseous products in wet oxidation of waste and wastewater. This invention does not require special preheaters for preheating feed streams, therefore reducing the possibility of scale and char formation in the heat exchange zone. The cold feed stream is introduced into the reactor with part of the effluent which has been recycled through a high temperature pumping means to form a hot, near critical oxidant-containing mixture. The cold feed is directly heated up by the oxidant-containing mixture. The reaction mixture is separated by in situ crossflow filtration elements, including sintered material. Catalyzed reactions and sintered material gas separation are also described.

Chemical oxidation--technologies for the nineties : proceedings of the First International Symposium, Chemical Oxidation: Technology for the Nineties, Vanderbilt University, Nashville, Tennessee, February 20-22, 1991

Abstract: 1. The Role of Chemical Oxidation in Wastewater Treatment Processes 2. Chemical Oxidation of Aromatic Compounds: Comparison of H2O2, KMnO4 and O3 for Toxicity Reduction and Improvements in Biodegradability 3. Hydrogen Peroxide in Advanced Oxidation Processes for Treatment of Industrial Process and Contaminated Groundwater 4. Treatment of Contaminated Soils Using Catalyzed Hydrogen Peroxide 5. Hydrogen Peroxide and Environmental Immediate Response 6. Practical Applications of Hydrogen Peroxide for Wastewater Treatment 7. NOx Removal in the Stainless Steel Pickling Industry with Hydrogen Peroxide 8. Hydrogen Peroxide Pretreatment of Inhibitory Wastestream - Bench-Scale Treatability Testing to Full-Scale Implementation: A Case History 9. Cyanide Detoxification with Peroxygens 10. Advanced Chemical Oxidation of Contaminated Water Using the perox-pureTM Oxidation System 11. Design of Completely Mixed Ozonation Reactors 12. Ozonation of Volatile and Semi-Volatile Compounds for Groundwater Remediation 13. Effects of Chemical Oxidation on Anaerobic Treatment of Phenols 14. Redox Reactions and the Analytical Chemistry of Chlorine Dioxide and Ozone 15. Chlorine Dioxide 16. The Interactive Effect of Chlorite, Copper and Nitrite on Methemoglobin Formation in Red Blood Cells of Dorset Sheep 17. The Chemistry of Permanganate in Degradative Oxidations 18. Uses of KMnO4, H2O2 and ClO2 in Wastewater Applications 19. Electrochemical Oxidation of Phenolic Compounds from Dilute Aqueous Solutions 20. Water Treatment by Heterogeneous Photocatalysis 21. Photocatalytic Oxidation Process for the Treatment of Organic Wastes 22. Supercritical Water Oxidation 23. Reactions of Organic Compounds with Supercritical Water Involving Chemical Oxidation 24. The Application of Wet Air Oxidation to the Treatment of Spent Caustic Liquor

Wet oxidation via two-phase flow reactors and high mass-transfer regimes

Abstract: This paper describes an approach based in the creation of a high interfacial area flow regime via a jet mixer. The latter is a device that permits the dispersion of the liquid phase into fine droplets. The establishment of a mist-type two-phase flow leads, in a few minutes, to rapid oxidation of the organic compounds in a kinetically controlled regime. A compact oxidation technology based on jet mixers and tubular reactors in thus achieved. The results obtained with prototype phenolic and glycol solutions and, also, with industrial wastewaters are discussed.

Catalytic wet air oxidation in the presence of hydrogen peroxide

Abstract: Wet air oxidation of chlorophenols has been examined at a range of temperatures (60-200°C), with and without added hydrogen peroxide, and in the presence or absence of a series of catalysts containing oxides of Mn, Cu, or Fe, alone or supported on SiO 2 or Al 2 O 3 . In the absence of hydrogen peroxide Mn-containing catalysts are effective, at higher temperatures. In the presence of hydrogen peroxide catalysts containing each metal are effective, and at lower temperatures.

Fluorine‐enhanced oxidation of polycrystalline silicon and application to thin‐film transistor fabrication

Abstract: The kinetics of the fluorinated oxidation of polycrystalline silicon thin films has been investigated and compared to the (100) single‐crystal silicon case. The growth of silicon dioxide was performed at oxidation temperatures down to 650 °C in dry ambients, which was made possible by fluorine‐induced oxidation enhancement; growth rates in the presence of fluorine additions approach those of wet oxidation. Silicon dioxide films grown on polycrystalline silicon were found to be thicker by about 10%–20% compared to films grown on (100) single‐crystal silicon oxidized under the same conditions. The application of fluorinated gate oxides in the fabrication of n‐channel polycrystalline silicon thin‐film transistors was found to improve the effective electron mobility.

Oxidation of Sintered Aluminum Nitride by Oxygen and Water Vapor

Abstract: Oxidation behavior of sintered AlN by oxygen and water vapor was studied at 1400°C for the purpose of surface treatment. The partial pressure of oxygen, Po2 was controlled at 10-10 and 10kPa, and that of water vapor, PH2O was changed at 5.0×10-2 to 8.5kPa. The oxidation product detected by XRD was α-Al2O3. Oxidation rate was increased with increasing PH2O. The weight gain with time by oxygen was parabolic, and that by water vapor was linear. The Al2O3 layer formed by the oxidation of sintered AlN with oxygen was relatively dense, and coherent. The oxidation kinetics were discussed using the mixed-control rate equation on the basis of unreacted-core model.

Oxidation Behaviour of Graphite /B4C/SiC/ZrB2 Composite in Dry and Moist Atmospheres

Abstract: High temperature oxidation tests from 600 to 1400°C were carried out for graphite/B4C/SiC/ZrB2 composite in different atmospheres such as dry air, dry oxygen and moist air with different moisture contents. From weight change, SEM observation, change of surface roughness and X-ray diffraction of the sample before and after the oxidation, it was found that the oxidation behaviour depends strongly on the nature of oxide layer formed on the surface by oxidation, and that the nature of the oxide layer depends on the temperature and time of oxidation, the oxygen partial pressure, and moisture content. The oxide layer was found to consist of mainly a B2O3-SiO2 glass phase, rich in B2O3 at low temperatures and rich in SiO2 at high temperatures. Active oxidation was observed at about 1100°C in dry air, at about 900°C in dry oxygen and moist air. Particularly, in the presence of moisture, oxidation proceeded extensively and sample was oxidized deeply from the surface to the inside through the less protective layer. An excellent protective layer formed at 1200°C oxidation and it protected the sample from further oxidation under all conditions examined.

Wet oxidation system startup process

Abstract: The invention is a process for starting up a wet oxidation system using essentially pure oxygen for oxidation of a concentrated wastewater. Flow of startup water and air is established through the wet oxidation system at an elevated temperature and pressure. An incremental increase in flow of oxygen and wastewater to the system commences while simultaneously an incremental decrease in flow of startup water and air occurs, raising system temperature in a controlled fashion. The incremental changes in flows are repeated until the wastewater and pure oxygen have reached about 100 percent of selected operating flows, the startup water and air flows have decreased to zero, and the system has attained the selected operating temperature, while maintaining a selected oxygen residual in the offgases.

Investigation of the oxidation kinetics of C54‐TiSi2 on (001)Si by transmission electron microscopy

Abstract: A transmission electron microscopy study of oxidation kinetics of C54‐TiSi2 for both dry and wet oxidation has been carried out. Precautions were taken to determine the activation energies of oxidation in the temperature and time regime where the islanding of TiSi2 did not occur. For dry oxidation, activation energies for parabolic and linear growth were found to be 1.97 and 2.50 eV (with an error bar of ±0.1 eV), respectively. On the other hand, activation energies for parabolic and linear growth were found to be 1.88 and 2.10 eV (with an error bar of ±0.1 eV), respectively, for wet oxidation. The activation energy of parabolic rate constant is seen to be substantially different from those obtained previously. The difference is attributed to the occurrence and absence of islanding during oxidation in the previous and present study, correspondingly. The closeness of linear activation energy of TiSi2 oxidation with that of pure silicon is thought to be due to the fact that both are related to the breaking ...

Oxidation of Semiconducting Iron Disilicide (β-FeSi2)

Abstract: Iron disilicide (β-FeSi2) has gained significant importance in recent years because of its semiconducting properties. The bandgap is reported to be direct with an energy of 0.85–0.89 eV, thus making the suicide a potential candidate for optical communications and detector applications. Compatibility with standard VLSI processing might involve a suicide thermal oxidation step. This work concerns the kinetics of both dry and wet oxidations of β-FeSi2. The oxide quality was characterized with respect to the electrical breakdown voltage. The results indicate an oxidation temperature dependence of the oxide quality and that dry oxidation yield higher breakdown voltage than wet oxidation. Structural and semiconducting suicide properties were investigated before and after oxidation. High energy implantation of xenon was used in a marker experiment to investigate a possible change of oxidation mechanism between dry and wet oxidation.

Decomposition of nitrophenol by wet oxidation in the presence of noble metal catalysts

Abstract: 水質汚染物質の一つであるニトロフェノールの湿式酸化分解について, 撹拌器付オートクレープを用いて150℃と200℃で検討を行った.ニトロフェノールはギ酸, 酢酸を含む低分子化合物に分解した.触媒は分解反応を促進させた.分解の評価指標としてのTOC除去率は150℃到達30分後でみると, チタニアに担持した白金触媒で70%であるのに対し, 触媒なしで0%であった.

Importance of sample preheating in oxidation of GexSi1−x

Abstract: Wet thermal oxidation at 1000 °C of a 470-nm-thick epitaxial Ge0.36Si0.64 layer on (100)Si produces oxides of different composition depending on the details of the oxidation procedure. When a cold sample is directly exposed to the hot steam, the surface layer of the oxide contains both Ge and Si. Only SiO2 forms if a preheated sample is exposed to the hot steam. The effect is not present for dry oxidation and is attributed to the known enhancement of the wet oxidation rate by Ge, coupled with the transient warm up of a sample when it is immersed cold in hot steam.

Effect of Water Vapor on High Temperature Oxidation of SiC

Abstract: High temperature oxidation of refractory-grade SiC was carried out in O2 and Ar atmospheres mixed with various concentrations of water vapor, and its oxidation behavior was followed mainly by using a mass-spectrometer. The results were as follows, (1) In the dry and wet O2 atmospheres, main gaseous products in the temperature-raising process up to 1400°C were CO and CO2 formed from the free carbon. Water vapor accelerated the oxidation of free carbon. On the other hand, in the successive soaking process at 1400°C, CO2 formed from SiC was a dominant product. The evolution behavior of CO2 during the soaking process was well fitted with the parabolic law and a positive tendency was observed between the parabolic rate constant and the water vapor content.(2) In the wet Ar atmospheres, CO, CO2 and H2 were evolved due to oxidation of the free carbon by water vapor in the temperature-raising process. The oxidation behavior of SiC in the soaking process changed with the water vapor content. At high water vapor contents, the passive oxidation took place, obeying the parabolic law and the parabolic rate constant increased in proportion to the content of water vapor. At the water vapor content as low as 0.6vol% H2O, however, the initial part of the reaction proceeded according to the active oxidation mechanism obeying the linear law. White spots observed on the surface of the sample after the active oxidation were composed of SiO2 fiber, which was presumably formed by the vapor phase reaction among SiO, CO and H2O.