Oxygen consumption test to evaluate the diffusive flux into reactive tailings: interpretation and numerical assessment

2011 ◽  
Vol 48 (6) ◽  
pp. 878-890 ◽  
Author(s):  
Mamert Mbonimpa ◽  
Michel Aubertin ◽  
Bruno Bussière
Keyword(s):  
Oxygen Consumption ◽  
Reaction Rate ◽  
Oxygen Flux ◽  
Test Duration ◽  
Oxidation Reactions ◽  
Relative Precision ◽  
Numerical Assessment ◽  
Sulphide Tailings ◽  
Numerical Parametric Study ◽  
Interpretation Method

The oxygen consumption (OC) test is conducted on sulphide tailings by measuring the decline of oxygen concentration in a closed headspace, at the top of a cylinder, as a result of diffusion and oxidation reactions. For a short-duration test, the measurements may be interpreted using a simplified analytical method based on modified Fick’s laws, which provides the combined value of the effective oxygen diffusion (De) and reaction rate (Kr) coefficients of the tailings. This lump value can be used to evaluate the steady-state oxygen flux entering the exposed sulphide tailings. In this paper, a numerical parametric study is performed to investigate the effect of test duration and headspace height, h, on results obtained from OC tests. The assessment also considers tailings with different values of De and Kr. The results indicate that the simplified interpretation method usually tends to underestimate the surface oxygen flux, in proportions that depend on the testing conditions. Results from this study can be used to estimate the relative precision of the oxygen flux for specific conditions, thus helping practitioners decide how to best interpret testing measurements for a given application.

Analytical Formulas for In-Situ Combustion

SPE Journal ◽  
2011 ◽  
Vol 16 (03) ◽  
pp. 513-523 ◽  
Author(s):  
A.A.. A. Mailybaev ◽  
J.. Bruining ◽  
D.. Marchesin
Keyword(s):  
Oxygen Consumption ◽  
High Temperature ◽  
Heat Wave ◽  
High Temperature Oxidation ◽  
Reaction Rate ◽  
Temperature Oxidation ◽  
Light Oil ◽  
Oil Components ◽  
Combustion Regimes

Summary There is a renewed interest in using combustion to recover medium- or high-viscosity oil. Despite numerous experimental, numerical, and analytical studies, the mechanisms for incomplete fuel combustion or oxygen consumption are not fully understood. Incomplete oxygen consumption may lead to low-temperature oxidation reactions downstream. This paper shows that these features emerge in a relatively simple 1D model, where air is injected in a porous medium filled with inert gas, water, and an oil mixture consisting of precoke, medium oil, and light oil. Precoke is a component that is dissolved in the oil but has essentially the same composition as coke. At high temperatures, precoke is converted to coke, which participates in high-temperature oxidation. At high temperatures, medium-oil components are cracked, releasing gaseous oil. Light-oil components and water are vaporized. The model possesses an analytical solution, which was obtained by a concept introduced by Zeldovich et al. (1985). This concept, which underlies most analytical approaches such as the reaction-sheet approximation and large-activation-energy asymptotics, entails that reaction can occur only in a very small temperature range because of the highly nonlinear nature of the Arrhenius factor. For a temperature below this range, the reaction rate is too slow, and for temperatures above this range, the reaction rate is so fast that either the fuel or oxygen concentrations become zero. The model results, in the absence of external heat losses, show that there are two combustion regimes in which coke or oxygen is partially consumed. In one regime, the reaction zone moves in front of the heat wave; whereas, in the other regime, the order of the waves is reversed. There are also two combustion regimes in which the coke and oxygen are completely consumed. Also, here the reaction zone can move in front of or at the back of the heat wave. Each combustion regime is described by a sequence of waves; we derive formulas for parameters in these waves. We analyze our formulas for typical in-situ-combustion data and compare the results with numerical simulation. The main conclusion is that mainly two key parameters (i.e., the injected oxygen mole fraction and the fuel concentration) determine the combustion-front structure and when either incomplete oxygen consumption or incomplete fuel consumption occurs in the high-temperature oxidation zone.

scholarly journals Body size and temperature effects on standard metabolic rate for determining metabolic scope for activity of the polychaete Hediste (Nereis) diversicolor

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5675 ◽  
Author(s):  
Helena Lopes Galasso ◽  
Marion Richard ◽  
Sébastien Lefebvre ◽  
Catherine Aliaume ◽  
Myriam D. Callier
Keyword(s):  
Oxygen Consumption ◽  
Body Size ◽  
Metabolic Rate ◽  
Growth Rates ◽  
Reaction Rate ◽  
Specific Growth ◽  
Standard Metabolic Rate ◽  
Metabolic Scope ◽  
Specific Growth Rates ◽  
Arrhenius Temperature

Considering the ecological importance and potential value of Hediste diversicolor, a better understanding of its metabolic rate and potential growth rates is required. The aims of this study are: (i) to describe key biometric relationships; (ii) to test the effects of temperature and body size on standard metabolic rate (as measure by oxygen consumption) to determine critical parameters, namely Arrhenius temperature (TA), allometric coefficient (b) and reaction rate; and (iii) to determine the metabolic scope for activity (MSA) of H. diversicolor for further comparison with published specific growth rates. Individuals were collected in a Mediterranean lagoon (France). After 10 days of acclimatization, 7 days at a fixed temperature and 24 h of fasting, resting oxygen consumption rates (VO2) were individually measured in the dark at four different temperatures (11, 17, 22 and 27 °C) in worms weighing from 4 to 94 mgDW (n = 27 per temperature). Results showed that DW and L3 were the most accurate measurements of weight and length, respectively, among all the metrics tested. Conversion of WW (mg), DW (mg) and L3 (mm) were quantified with the following equations: DW = 0.15 × WW, L3 = 0.025 × TL(mm) + 1.44 and DW = 0.8 × L33.68. Using an equation based on temperature and allometric effects, the allometric coefficient (b) was estimated at 0.8 for DW and at 2.83 for L3. The reaction rate (VO2) equaled to 12.33 µmol gDW−1 h−1 and 0.05 µmol mm L3−1 h−1 at the reference temperature (20 °C, 293.15 K). Arrhenius temperature (TA) was 5,707 and 5,664 K (for DW and L3, respectively). Metabolic scope for activity ranged from 120.1 to 627.6 J gDW−1 d−1. Predicted maximum growth rate increased with temperature, with expected values of 7–10% in the range of 15–20 °C. MSA was then used to evaluate specific growth rates (SGR) in several experiments. This paper may be used as a reference and could have interesting applications in the fields of aquaculture, ecology and biogeochemical processes.

scholarly journals Studies of Jet Thermal Stability in a Flowing System

1992 ◽  
Author(s):  
S. P. Heneghan ◽  
C. R. Martel ◽  
T. F. Williams ◽  
D. R. Ballal
Keyword(s):  
Thermal Stability ◽  
Oxygen Consumption ◽  
Jet Fuel ◽  
Total Carbon ◽  
Threshold Temperature ◽  
Jet Fuels ◽  
Test Duration ◽  
Fuel Temperature ◽  
Test Rig ◽  
Carbon Deposits

A flowing, single-pass heat exchanger test rig, with a fuel capacity of 189 litres, has been developed to evaluate jet fuel thermal stability. This so called, “Phoenix Rig” is capable of supplying jet fuel to a 2.15 mm I.D. tube at a pressure up to 3.45 MPa, fuel temperature up to 900K, and a fuel-tube Reynolds number in the range 300–11,000. Using this test rig, fuel thermal stability (carbon deposition rate), dissolved oxygen consumption, and methane production were measured for three baseline jet fuels and three fuels blended with additives. Such measurement were performed under oxygen-saturation or oxygen-starved conditions. Tests with all of the blended fuel samples showed a noticeable improvement in fuel thermal stability. Both block temperature and test duration increased the total carbon deposits in a nonlinear fashion. Interestingly, those fuels that need a higher threshold temperature to force the consumption of oxygen exhibited greater carbon deposits than those that consume oxygen at a lower temperature. These observations suggested a complicated relationship between the formation of carbon deposits and the temperature-driven consumption of oxygen. A simple analysis, based on a bi-molecular reaction rate, correctly accounted for the shape of the oxygen consumption curve for various fuels. This analysis yielded estimates of global bulk parameters of oxygen consumption. The test rig yielded quantitative results which will be very useful in evaluating fuel additives, understanding the chemistry of deposit formation, and eventually developing a global chemistry model.

Dual Role of Perovskite Hollow Fiber Membrane in the Methane Oxidation Reactions

2016 ◽  
pp. 385-430
Author(s):  
Serbia M. Rodulfo-Baechler
Keyword(s):  
Carbon Dioxide ◽  
Methane Oxidation ◽  
Partial Oxidation ◽  
Hollow Fiber Membrane ◽  
Hollow Fibre ◽  
Dual Role ◽  
Partial Oxidation Of Methane ◽  
Oxygen Flux ◽  
Oxidation Reactions ◽  
Oxidation Of Methane

The Mixed Ionic and Electronic Conducting (MIEC) membrane reactors are of interest because they have the potential to produce high purity oxygen from air at lower costs and provide a continuous oxygen supply to reactions or/and industrial processes. The study of the dual role oxygen flux and catalytic performance of the unmodified and Ni-coated La0.6Sr0.4Co0.2Fe0.8O3-d hollow fibre membranes (LSCF6428 HFM) in the methane oxidation reactions (i.e., partial oxidation of methane and methane combustion) by using air on lumen side and methane on shell side are shown in this chapter. The LSCF6428 HFM participates not only in the oxygen flux but also in the methane conversion to C2. A Ni-coated LSCF6428 HFM under lean O2/CH4 gradient (i.e., 0.5) showed the production of syngas, carbon dioxide and C2 products in agreement with the thermodynamic calculation. At rich O2/CH4 gradient (i.e., 1.0), the formation of carbon dioxide was facilitated. The main catalytic pathway at lean O2/CH4 gradient and H2 reduction treatment was partial oxidation of methane to C2 and syngas.

Gas-phase oxidation of hexene-1

1958 ◽  
Vol 244 (1238) ◽  
pp. 345-354 ◽  
Keyword(s):  
Oxygen Consumption ◽  
Gas Phase ◽  
Maximum Rate ◽  
Reaction Rate ◽  
Pressure Change ◽  
Early Stages ◽  
Unusual Form ◽  
Phase Oxidation ◽  
Rate Of Oxygen Consumption ◽  
Gas Phase Oxidation

An investigation has been made of the oxidation of hexene-1 at 263°C. The unusual form of dependency of reaction rate on hydrocarbon pressure obtained when the maximum rate of pressure change is used as a measure of reaction rate is explained by the fact that much of the oxygen is consumed before the maximum rate of pressure change is attained. This, and the observation that the maximum rate of oxygen consumption exhibits a different dependence on hexene concentration compared with the maximum rate of pressure change confirm that maximum rate of pressure change is an invalid measure of reaction rate. Analyses have been made for certain intermediates and products throughout the course of the reaction, and it has been possible to explain many of the experimental features in terms of ideas previously propounded. A decrease in pressure which in many experiments precedes the rapid increase in pressure is attributed to polymerization reactions which predominated over oxidative degradations in the early stages of the reaction, particularly when the olefin is present in excess.

Studies of Jet Fuel Thermal Stability in a Flowing System

1993 ◽  
Vol 115 (3) ◽  
pp. 480-485 ◽  
Author(s):  
S. P. Heneghan ◽  
C. R. Martel ◽  
T. F. Williams ◽  
D. R. Ballal
Keyword(s):  
Thermal Stability ◽  
Oxygen Consumption ◽  
Bimolecular Reaction ◽  
Jet Fuel ◽  
Total Carbon ◽  
Threshold Temperature ◽  
Test Duration ◽  
Fuel Temperature ◽  
Test Rig ◽  
Carbon Deposits

A flowing, single-pass heat exchanger test rig, with a fuel capacity of 189 liters, has been developed to evaluate jet fuel thermal stability. This “Phoenix Rig” is capable of supplying jet fuel to a 2.15 mm i.d. tube at a pressure up to 3.45 MPa, fuel temperature up to 900 K, and a fuel-tube Reynolds number in the range 300–11,000. Using this test rig, fuel thermal stability (carbon deposition rate), dissolved oxygen consumption, and methane production were measured for three baseline jet fuels and three fuels blended with additives. Such measurement were performed under oxygen-saturation or oxygen-starved conditions. Tests with all of the blended fuel samples showed a noticeable improvement in fuel thermal stability. Both block temperature and test duration increased the total carbon deposits in a nonlinear fashion. Interestingly, those fuels that need a higher threshold temperature to force the consumption of oxygen exhibited greater carbon deposits than those that consume oxygen at a lower temperature. These observations suggested a complicated relationship between the formation of carbon deposits and the temperature-driven consumption of oxygen. A simple analysis, based on a bimolecular reaction rate, correctly accounted for the shape of the oxygen consumption curve for various fuels. This analysis yielded estimates of global bulk parameters of oxygen consumption. The test rig yielded quantitative results, which will be very useful in evaluating fuels additives, understanding the chemistry of deposit formation, and eventually developing a global chemistry model.

scholarly journals Substrate-Solvent Crosstalk – Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

2021 ◽  
Author(s):  
Rita N. Sales ◽  
Sam K. Callear ◽  
Pedro D. Vaz ◽  
Carla D. Nunes
Keyword(s):  
Ring Opening ◽  
Reaction Rate ◽  
Styrene Oxide ◽  
Oxidation Catalysis ◽  
Product Selectivity ◽  
Oxidation Reactions ◽  
Olefin Oxidation ◽  
Reaction Systems ◽  
Ring Opening Reaction ◽  
Oxide Conversion

In this work we explored how solvents can affect olefin oxidation reactions catalyzed by MCM-bpy-Mo catalysts and whether their control can be made with those players. The results of this study evidenced that polar and apolar aprotic solvents modulated the reactions in different ways. Experimental data showed that acetonitrile (aprotic polar) could hinder largely the reaction rate whereas toluene (aprotic apolar) did not. In both cases product selectivity at isoconversion was not affected. Further insights were obtained by means of neutron diffraction experiments, which confirmed the kinetic data allowing to propose a model based on substrate-solvent crosstalk by means of hydrogen bonding. In addition, the model was also validated in the ring-opening reaction (overoxidation) of styrene oxide towards benzaldehyde, which progressed when toluene was the solvent (reaching 31% styrene oxide conversion) but was strongly hindered when acetonitrile was used instead (reaching only 7% conversion), due to the establishment of H-bonds in the latter. Although this model was confirmed and validated for olefin oxidation reactions, it can be envisaged that it may also be applied to other catalytic reaction systems where reaction control is critical, while widening its use.

DBP formation in drinking water: kinetics and linear modelling

2008 ◽  
Vol 8 (2) ◽  
pp. 161-166 ◽  
Author(s):  
G. Della Greca ◽  
M. Fabbricino
Keyword(s):  
Experimental Data ◽  
Partition Coefficients ◽  
Reaction Rate ◽  
Oxidation Reactions ◽  
State Approximation ◽  
Steady State Approximation ◽  
Linear Modelling ◽  
Linear Differential ◽  
Original Approach ◽  
By Products

An original approach for modelling disinfection by-products formation in chlorinated water is proposed. Assuming a multi-step formation mechanism, and introducing partition coefficients to differentiate the various compounds formed as a consequence of halogen incorporation and oxidation reactions, a system of linear differential equations is obtained and solved in explicit terms. Two sets of solutions are derived: the first one assuming that the reaction rate is the same for all species included in the model, as a consequence of steady state approximation; the second one assuming that the reaction rate is different from one species to another. Experimental data, obtained varying reaction time and chlorine dose, are used to calibrate the two models. Statistic tests are also performed to compare the two sets of solutions and validate the assumed hypotheses.

scholarly journals Substrate–Solvent Crosstalk—Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 753-764
Author(s):  
Rita N. Sales ◽  
Samantha K. Callear ◽  
Pedro D. Vaz ◽  
Carla D. Nunes
Keyword(s):  
Ring Opening ◽  
Reaction Rate ◽  
Styrene Oxide ◽  
Oxidation Catalysis ◽  
Product Selectivity ◽  
Oxidation Reactions ◽  
Olefin Oxidation ◽  
Reaction Systems ◽  
Ring Opening Reaction ◽  
Oxide Conversion

In this work, we explored how solvents can affect olefin oxidation reactions catalyzed by MCM-bpy-Mo catalysts and whether their control can be made with those players. The results of this study demonstrated that polar and apolar aprotic solvents modulated the reactions in different ways. Experimental data showed that acetonitrile (aprotic polar) could largely hinder the reaction rate, whereas toluene (aprotic apolar) did not. In both cases, product selectivity at isoconversion was not affected. Further insights were obtained by means of neutron diffraction experiments, which confirmed the kinetic data and allowed for the proposal of a model based on substrate–solvent crosstalk by means of hydrogen bonding. In addition, the model was also validated in the ring-opening reaction (overoxidation) of styrene oxide to benzaldehyde, which progressed when toluene was the solvent (reaching 31% styrene oxide conversion) but was strongly hindered when acetonitrile was used instead (reaching only 7% conversion) due to the establishment of H-bonds in the latter. Although this model was confirmed and validated for olefin oxidation reactions, it can be envisaged that it may also be applied to other catalytic reaction systems where reaction control is critical, thereby widening its use.

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