Conjugate mass transfer for the removal of hydrogen sulfide gas circulating in a slit microchannel on a homogeneous biofilm under the influence of the Damköhler number

2020 ◽  
Author(s):  
Wenceslao Bonilla-Blancas ◽  
Agustin Mora-Ortega ◽  
Federico Mendez
Keyword(s):  
Mass Transfer ◽  
Hydrogen Sulfide ◽  
Damkohler Number ◽  
Damköhler Number

Mass transfer and biodegradation of PAH compounds from coal tar

1994 ◽  
Vol 30 (7) ◽  
pp. 61-70 ◽  
Author(s):  
A. Ramaswami ◽  
S. Ghoshal ◽  
R. G. Luthy
Keyword(s):  
Mass Transfer ◽  
Aqueous Phase ◽  
Coal Tar ◽  
Damkohler Number ◽  
Damköhler Number ◽  
Biological Phenomena ◽  
Physico Chemical ◽  
Mass Transfer Processes ◽  
Polycyclic Aromatic ◽  
Competitive Substrate

This study examines the role of physico-chemical mass transfer processes on the rate of biotransformation of polycyclic aromatic hydrocarbon (PAH) compounds released from non-aqueous phase liquid (NAPL) coal tar present at residual saturation within a microporous medium. A simplified coupled dissolution-degradation model is developed that describes the concurrent mass transfer and biokinetic processes occurring in the system. Model results indicate that a dimensionless Damkohler number can be utilized to distinguish between systems that are mass transfer limited, and those that are limited by biological phenomena. The Damkohler number is estimated from independent laboratory experiments that measure the rates of aqueous phase dissolution and biodegradation of naphthalene from coal tar. Experimental data for Stroudsburg coal tar imbibed within 236μm diameter silica particles yield Damkohler numbers smaller than unity, indicating, for the particular system under study, that the overall rate of biotransformation of naphthalene is not limited by the mass transfer of naphthalene from coal tar to the bulk aqueous phase. There is a need for investigation of mass transfer for larger particles and/or other PAH compounds, and study of microbial rate-limiting phenomena including toxicity, inhibition and competitive substrate utilization.

Evaluation of the One-Well Uranium Leaching Test: Restoration

1982 ◽  
Vol 22 (01) ◽  
pp. 141-150 ◽  
Author(s):  
Muhammad I. Kabir ◽  
Larry W. Lake ◽  
Robert S. Schechter
Keyword(s):  
Acid Leaching ◽  
Leach Solution ◽  
Damkohler Number ◽  
Damköhler Number ◽  
Well Spacing ◽  
Number Of Factors ◽  
Well Pattern ◽  
Mineralized Zone ◽  
Selection Of

Abstract In-situ leach mining for uranium is an emerging technology. Currently, the selection of a well pattern designed to recover mineral values is governed primarily by arguments based on hydrological considerations. The effects of well pattern and well spacing on uranium recovery and oxidant utilization are considered in this paper. As expected, formation permeability heterogeneities and anisotropies are found to be important issues requiring careful consideration, however, it also is shown that chemical factors cannot be ignored. In particular, it is shown that the oxidant efficiency and the produced uranium solution concentrations are sensitive to the presence of other minerals competing with uranium for oxidant. If the Damkohler number for competing minerals, which measures the speed of the reaction, exceeds that for uranium, the competing mineral will have to be oxidized completely to recover a large proportion of the uranium. If the Damkohler number is smaller, it may be possible to achieve considerable selectivity for uranium by adjusting the well spacing. It also is shown that the oxidant efficiency is generally highest for well patterns that give streamlines of roughly equal length and that there is a minimum distance between injection and production wells to utilize oxidant most advantageously. Introduction In-situ solution mining is a process whereby uranium is recovered from permeable sandstone bodies by injecting and producing a leach solution through an array of wells penetrating the mineralized zone. It appears to have broad application and in many situations offers both economic and environmental advantages. The processes may be classified generally as acid or alkaline, but the general features of both are the same. The insoluble uranium in the mineralized zone is in the +4 state of oxidation. To be mobilized, the uranium must be oxidized to the +6 state and complexed either with sulfate in the case of acid leaching or carbonate in the case of alkaline leaching to form highly soluble uranyl sulfates or carbonates. The leach solutions, therefore, contain an oxidant (oxygen, hydrogen peroxide, ferric cations, sodium hyperchlorite, etc.) together with a complexing agent (anion). The choice of leach solution depends on a number of factors including selectivity and injectivity. For example, formations containing more than 1 wt% carbonates are not likely to be candidates for acid leaching because of the large acid requirement and because of permeability loss due to precipitation of calcium sulfate. It is the purpose of this paper to consider the technical factors (as opposed to economic) that govern the choice of well pattern to be used for leaching. The discussion is structured so that the conclusions apply to both alkaline and acid lixiviants and to any oxidant, although an occasional reference to a particular oxidant may appear. Considerable use is made of the computer simulator previously reported. The computational details are available in that paper. A number of factors that pertain to the selection of a well pattern are considered. It is shown that the effectiveness of the oxidant - i.e., the uranium recovered per unit of oxidant injected - is related to the well pattern, to the reaction rates, and to the permeability variations, especially if the formation is anisotropic. Furthermore, the spacing between wells is related to reactions with oxidizable minerals that compete for oxidant. These considerations can be quantified to some extent by studying linear systems. Linear Flow Systems SPEJ P. 132^

An Experimental and Theoretical Study of Heat Conduction and Vulcanization of Rubber Compounds in Molds

1987 ◽  
Vol 60 (1) ◽  
pp. 140-158 ◽  
Author(s):  
Dancheng Kong ◽  
James L. White ◽  
Frederick C. Weissert ◽  
Nobuyuki Nakajima
Keyword(s):  
Heat Conduction ◽  
Curing Kinetics ◽  
Damkohler Number ◽  
Fourier Number ◽  
Fundamental Study ◽  
Damköhler Number ◽  
Rubber Compounds ◽  
Cure Temperature ◽  
Black Other ◽  
Kinetics Of

Abstract A fundamental study on curing of rubber compounds in molds is presented. We have measured the thermal conductivity of a range of rubber compounds determining the influence of carbon black, other fillers, and oil. The heats of reaction associated with the curing kinetics of model compounds were measured. A mathematical model is proposed to predict the temperature profiles for curing a reactive slab. This involves inclusion of an energy generation rate, which depends on time and temperature. This is expressed through a Damkohler number. Solutions of the heat conduction equation are interpreted in terms of the Fourier number and the Damkohler number. Calculations are carried out using experimentally determined thermal conductivities and curing kinetics. Thick parts are shown to heat up more slowly (associated with the Fourier number) and to show greater overshoots of cure temperature (associated with the Damkohler number).

A General Study of Counterflow Diffusion Flames for Supercritical CO2 Combustion

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
K. R. V. Manikantachari ◽  
Scott Martin ◽  
Ramees K. Rahman ◽  
Carlos Velez ◽  
Subith Vasu
Keyword(s):  
Prandtl Number ◽  
Supercritical Co2 ◽  
Diffusion Flames ◽  
Lewis Number ◽  
Dilution Effect ◽  
Scalar Dissipation ◽  
Damkohler Number ◽  
Nonpremixed Combustion ◽  
Flame Thickness ◽  
Damköhler Number

Abstract A counterflow diffusion flame for supercritical CO2 combustion is investigated at various CO2 dilution levels and pressures by accounting for real gas effects into both thermal and transport properties. The UCF 1.1 24-species mechanism is used to account the chemistry. The nature of important nonpremixed combustion characteristics such as Prandtl number, thermal diffusivity, Lewis number, stoichiometric scalar dissipation rate, flame thickness, and Damköhler number are investigated with respect to CO2 dilution and pressure. The results show that the aforementioned parameters are influenced by both dilution and pressure; the dilution effect is more dominant. Further, the result shows that Prandtl number increases with CO2 dilution and at 90% CO2 dilution, the difference between the Prandtl number of the inlet jets and the flame is minimal. Also, the common assumption of unity Lewis number in the theory and modeling of nonpremixed combustion does not hold reasonable for sCO2 applications due to large difference of Lewis number across the flame and the Lewis number on the flame drop significantly with an increase in the CO2 dilution. An interesting relation between Lewis number and CO2 dilution is observed. The Lewis number of species drops by 15% when increasing the CO2 dilution by 30%. Increasing the CO2 dilution increases both the flow and chemical timescales; however, chemical timescale increases faster than the flow timescales. The magnitudes of the Damköhler number signify the need to consider finite rate chemistry for sCO2 applications. Further, the Damköhler numbers at 90% sCO2 dilution are very small; hence, laminar flamelet assumptions in turbulent combustion simulations are not physically correct for this application. Also, it is observed that the Damköhler number drops nonlinearly with increasing CO2 dilution in the oxidizer stream. This is a very important observation for the operation of sCO2 combustors. Further, the flame thickness is found to increase with CO2 dilution and reduce with pressure.

Effect of Damkohler Number and Non-Unity Lewis Number on a Laminar Diffusion Flame

2003 ◽  
Author(s):  
Bassem H. Ramadan
Keyword(s):  
Diffusion Flame ◽  
Rectangular Channel ◽  
Flame Structure ◽  
Lewis Number ◽  
Damkohler Number ◽  
Laminar Diffusion Flame ◽  
Damköhler Number ◽  
Laminar Diffusion ◽  
Adi Schemes ◽  
Steady Laminar

The effect of the Damkohler number (Da) and non-unity Lewis number on a two-dimensional, steady, laminar diffusion flame anchored by a dividing plate in a rectangular channel was considered. The governing equations were solved numerically, using the SIMPLE and ADI schemes. The results for non-unity Lewis number were compared with those for a unity Lewis number, and Da a was also varied in order to determine their effect on the flame structure. The results show that an increase in the Da causes the flame to exist closer to the trailing edge of the divider and to increase the reactivity. A non-unity Lewis number creates a non-symmetrical flame by forcing the flame to exist on the fuel side.

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