Showing papers on "Wet oxidation published in 1991"

Generalized kinetic model for wet oxidation of organic compounds

Abstract: A generalized kinetic model for wet oxidation (WO) of organic compounds was developed based on a simplified reaction scheme considering acetic acid as the rate-limiting intermediate. The selectivity of product vs. intermediate formations was quantified by the ratio of the two reaction rate constants. This point selectivity α may be used to characterize the “strength” of the feed stream to be treated. This global model was validated using WO kinetic data reported for temperatures ranging from 150°C to 550°C and pressures varying from 20 bar to 440 bar. Organic conversions predicted by this model, as compared to other models, more accurately reflect the actual performance of WO processes. The model has practical validity for a variety of organic compounds, wastewaters and sludges in both subcritical and supercritical water oxidation processes.

Electrochemical waste water treatment using high overvoltage anodes Part II: Anode performance and applications

Abstract: The performance of highly doped SnO2 anodes for the oxidative treatment of biologically refractory waste water was compared with PbO2 and Pt. The oxidation of a wide range of organic compounds proceeds with an efficiency which is about 5 times higher than with platinum anodes. The oxidation efficiency was found to be independent of the pH of the water. In chloride containing media, SnO2 anodes produce less chlorine gas than platinum anodes and hence show less potential to form hazardous chlorinated organic by-products. The design of a simple plate-and-frame reactor with undivided cells for waste water treatment using SnO2 anodes was based on two experimental findings: (a) no interference of the cathode with the oxidation has been found: (b) the rate of oxidation is not limited by mass transfer, indicating the participation of homogeneous reactions in the overall oxidation. The new anode material reduces the specific energy requirement of electrochemical oxidation of organics in waste water to 30 to 50 kWh kg−1 of COD removed. This makes the process an interesting alternative to chemical oxidation using oxidants such as ozone and hydrogen peroxide, or wet oxidation using oxygen at elevated temperature and pressure.

Oxidation of Si1−xGex alloys at atmospheric and elevated pressure

Abstract: The oxidation of alloys of Si1−xGex differs significantly from that of pure Si in both the thermodynamics of the process and in the kinetics of the oxidation reaction. In this paper these fundamental differences are explored and are used to explain experimental observations of Si1−xGex oxidation that are presented herein and elsewhere in the literature. Alloys of Si1−xGex (with x=5.4, 11.6, and 17 at. %) approximately 200 nm thick were oxidized using the following two processes: (i) dry oxygen at 680 atm at a temperature of 550 °C and (ii) conventional, 1‐atm steam at 800 °C. The wet oxidation conditions were chosen to produce an oxide thickness comparable (≊100 nm for xGe=11.6 at. %) to that obtained during high‐pressure oxidation at 550 °C. Auger sputter depth profiling, x‐ray photoelectron spectroscopy (XPS), and cross‐sectional transmission electron microscopy were used to characterize the as‐grown oxides. XPS studies reveal that high‐pressure oxides formed from alloys of Si1−xGex chemically incorpora...

Caustic sulfide wet oxidation process

Abstract: A process for treatment of caustic sulfide liquor by wet oxidation in a nickel-based alloy system 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 nickel-base alloy system.

Method for starting up and controlling operating temperature of a wet oxidation process

Abstract: A method for starting up and controlling the temperature of a wet oxidation process in which a heat exchanger (30) employing superheated steam is used to initially heat a waste stream introduced into a wet oxidation reaction vessel (38) for start up and then to subsequently adjust the temperature of the waste stream, after it is preheated by the effluent from the reaction vessel, to a level suitable to maintain steady state operation of the reaction vessel.

Thermal oxidation of amorphous ternary Ta36Si14N50 thin films

Abstract: The oxidation kinetics of reactively sputtered amorphous Ta36Si14N50 thin films are studied in dry and wet ambient in the temperature range of 650-850-degrees-C by backscattering spectrometry, Dektak profilometer, and x-ray diffraction analyses. The dry oxidation is well described by a parabolic time dependence which corresponds to a process controlled by the diffusion of the oxidant in the oxide. The growth of the oxide in wet ambient is initially very rapid and then proceeds linearly which means that the process is reaction limited. Both oxidation rates are thermally activated. The activation energies are 2.0 eV for dry and 1.4 eV for wet ambient. The pre-exponential factors are 0.17 x 10^(16) angstrom 2/min and 7.4 x 10^(8) angstrom/min, respectively. Both the dry and wet oxidation of the amorphous ternary Ta36Si14N50 film result in the formation of an x-ray amorphous Ta14Si5.5O80 layer.

Apparatus for wet oxidation

Abstract: The apparatus (1) for wet oxidation is pre-assembled with its individual units, namely a high-pressure pump (2), a heat exchanger (3), a reactor (4) for the actual wet oxidation and a compressor (5) for feeding an oxygen/gas mixture, in one or two supporting flames and is accommodated in such a manner that its dimensions and its overall weight allow it to be transported on a road and/or rail vehicle, there advantageously being provided two such supporting flames in the form of standard containers (8 and 9), of which one may contain the reactor (4), divided into individual tube sections (6), and the heat exchanger (3), and the other may contain the remaining units, so that the entire apparatus can be pre-assembled into virtually operational condition and the two containers simply have to be set up, joined together and connected on site. Wet oxidation can thus be carried out even where relatively small quantities of medium are to be purified.

Spent-fuel dry-bath oxidation testing

Abstract: Multiple samples of moderate-burnup pressurized water reactor (PWR) and boiling water reactor (BWR) spent fuel are oxidized in controlled atmosphere dry baths at 175, 130, and 110{degrees}C. The atmosphere consists of air humidified to a dew point of either {minus}55 or +80{degrees}C. These tests are run for up to 18.8 kh. In this paper, the weight gain data from these tests are analyzed using a mathematical model incorporating the assumption that oxidation occurs by rapid grain-boundary oxygen diffusion, followed by oxidation of the individual fuel grains. The BWR fuel appears to oxidize slightly faster than PWR fuel, and the data suggest a possible increase in oxidation rate in moist air. Reasonable agreement is observed between the oxidation rate constants obtained in these long-term test and prior short-term thermogravimetric analysis oxidation tests.

Wet Oxidation of Epitaxial Ge.36Si.64 on (100)Si

Abstract: The thermal oxidation of epitaxial Ge.36Si.64 on (100)Si is investigated experimentally for a wet ambient at 700°C and 1000°C. A pure silicon dioxide layer with pile-up of Ge behind the oxide is formed at 1000°C. At 700°C, however, both Ge and Si are oxidized. The Ge is included uniformly into the oxide layer without changing the initial Ge/Si ratio. The result at 1000°C follows the thermodynamical picture which predicts the same result at 700°C also, contrary to observation. The different result at 700°C is due to kinetic constraints which can be explained by different activation energies for the rate of the oxidation reaction and for the Ge or Si diffusivities in GeSi.

Treatment of waste water from methacrylic acid producing plant

Abstract: PURPOSE:To efficiently treat waste water contg acetic acid and aldehydes from a methacrylic acid producing plant by wet-oxidizing the org substances in the waste water with fed gas contg molecular oxygen at a specified temp under a specified pressure CONSTITUTION:Waste water contg acetic acid and aldehydes sent from a methacrylic acid producing plant to a line 13 is sent to a heat exchanger 5, preheated and fed into a wet oxidation reactor 1 packed with a solid catalyst Gas contg molecular oxygen fed from a line 14 is compressed with a compressor 6 and fed into reaction tubes 11 in the reactor 1 through a line 19 In the reactor 1, the org substances in the waste water are wet oxidized with the fed gas at <=370 degC under the pressure required to maintain the liq phase of the waste water

Treatment of waste water containing sulfur-containing compound

Abstract: PURPOSE:To make harmless waste water containing a sulfur-containing com pound by a simple treatment process wherein the sulfur-containing compound in the waste water is decomposed by subjecting waste water to wet oxidation using molecular oxygen at 350 deg.C or lower under pressure holding a liquid phase in the presence of a solid catalyst. CONSTITUTION:Waste water sent from a line 8 is raised to 9kg/cm in pressure 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 O/TOD=1.2. This gas-liquid mixture is introduced into a heat exchanger 2 through a line 10 to be heated to 150 deg.C and introduced into a wet oxidizing tower 1. The waste water passed through the palladium titanium-zirconia oxide catalyst received in the wet oxidizing tower 1 is subjected to oxidation treatment and cooled by the heat exchanger 2 through a line 11 to be sent to a gas-liquid separator 4. The constant level of the waste water is held in the gas-liquid separator 4 by a liquid level controller LC and constant pressure is held by a pressure controller PC.

Wet oxidation decomposition of organic solvent

Abstract: PURPOSE:To rapidly and efficiently execute an oxidation decomposition treatment without separating a liquid org. compd. of a low sp. gr. to two layers by mixing an org. solvent and an oxidizing agent by ultrasonic oscillation and bringing the mixture into contact with a catalyst, thereby effecting the oxidation decomposition reaction. CONSTITUTION:The liquid org. compd. 1 supplied from supply tanks 4a, 4b and an aq. oxidizing agent soln. 2 join to each other midway in the piping and are mixed by the ultrasonic oscillation of an ultrasonic chamber A, by which the soln. is mixed to an emulsion state. The emulsion is supplied to a decomposition reaction chamber B. The liquid mixed in the above-mentioned ultrasonic chamber A is joined with the above-mentioned decomposition reaction chamber B in which diluting water is previously charged. This liquid is heated, is maintained in a boiling state and is stirred by a stirring vane 7. The oxidation decomposition reaction is effected in this way. The formed gaseous components are treated in a discharge treating system C via a cooler 8. The liquid org. compd. of the low sp. gr. is rapidly subjected to the oxidation decomposition treatment in this way without being separated to the two layers.

Defect Centers Formed During Wet Oxidation of Si-Ge/Si Heterostructures

Abstract: Germanium incorporated oxide films formed by wet oxidation of SiGe substrates have been studied using Electron Paramagnetic Resonance. SiGe layers 400 nm thick were prepared by molecular beam epitaxy and oxidized in a steam ambient at 900° C. After a 10 Mrad x-ray irradiation, an oxide defect with a zero crossing at g=1.995 is observed. Comparison of the spectrum with that obtained from Ge-doped silica suggests that the defect observed in the thin film is an oxygen vacancy related defect, a Ge E' center.

Device for wet oxidation

Abstract: The device (1) for wet oxidation with its individual units, that is a high pressure pump (2), a heat exchanger (3), a reactor (4) for the actual wet oxidation and a compressor (5) for feeding an oxygen/gas mixture is preassembled in one or two carrying frames and is housed in such a manner that their dimensions and their total weight permit transport on a road vehicle and/or rail vehicle, two of such carrying frames being expediently provided as standard containers (8 and 9), one of which can contain the reactor (4) divided into individual tube pieces (6) and the heat exchanger (3) and the other of which can contain the remaining units, so that a preassembly of the whole device is possible in almost operational condition and that at the site of use it is only necessary for both containers to be installed, joined together and connected up. A wet oxidation can thus be carried out even with low quantities of medium to be purified.