Effect of homogeneous and heterogeneous reactions on the dispersion of a solute in the laminar flow between two plates

1972 ◽  
Vol 330 (1580) ◽  
pp. 59-63 ◽  
Keyword(s):  
Diffusion Coefficient ◽  
Rate Constant ◽  
Reaction Rate ◽  
Heterogeneous Reaction ◽  
Reaction Rate Constant ◽  
Heterogeneous Reactions ◽  
Parallel Plates ◽  
Homogeneous And Heterogeneous Reactions ◽  
First Order Chemical Reaction ◽  
Taylor Diffusion

The paper presents an analytical solution for the dispersion of a solute in a liquid flowing between two parallel plates in the presence of an irreversible first-order chemical reaction. The effects of both homogeneous and heterogeneous reactions on the dispersion are studied under isothermal conditions. It is found that for homogeneous reaction in the bulk of the liquid, the effective Taylor diffusion coefficient decreases with increase in the reaction rate constant. Further for heterogeneous reaction at the catalytic walls, Taylor diffusion coefficient is also found to decrease with increase in the wall catalytic parameter for fixed reaction rate constant corresponding to the bulk reaction.

Estimation of the catalyst pellet activity distribution from zero order kinetic data

1987 ◽  
Vol 52 (10) ◽  
pp. 2426-2437 ◽  
Author(s):  
Alena Brunovská ◽  
Josef Horák
Keyword(s):  
Diffusion Coefficient ◽  
Rate Constant ◽  
Kinetic Data ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Zero Order ◽  
Simultaneous Estimation ◽  
Activity Distribution ◽  
Catalyst Pellet ◽  
The Mean

In this paper a method of simultaneous estimation of the catalyst pellet activity distribution, the mean reaction rate constant, and the diffusion coefficient from kinetic data is described. As kinetic data measurements of outlet concentration from laboratory continuous stirred tank reactor vs feed rate for zero order reaction is used. The estimation technique is verified on simulated data. The mean reaction rate constant is estimated from the region of investigated dependence in which reactant penetrates into the whole catalyst pellet. The value of the effective diffusion coefficient and the activity distribution are estimated from the regime in which the reactant penetrates into the part of the pellet only.

scholarly journals Effects of stabilized Criegee Intermediates (sCI) on the sulfate formation: A case study during summertime in Beijing-Tianjin-Hebei (BTH), China

2019 ◽  
Author(s):  
Lang Liu ◽  
Naifang Bei ◽  
Jiarui Wu ◽  
Suixin Liu ◽  
Jiamao Zhou ◽  
...  
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Heterogeneous Reaction ◽  
Reaction Rate Constant ◽  
So2 Emissions ◽  
So2 Oxidation ◽  
Formation Pathway ◽  
Criegee Intermediates ◽  
Sulfate Formation ◽  
Stabilized Criegee Intermediates

Abstract. Sulfate aerosols exert profound impacts on climate, ecosystem, visibility, and public health, but the sulfate formation pathway remains elusive. In the present study, a source-oriented WRF-Chem model is applied to simulate a persistent air pollution episode from 04 to 15 July 2015 in Beijing-Tianjin-Hebei (BTH), China to study contributions of four pathways to the sulfate formation. When comparing simulations to measurements in BTH, the index of agreement (IOA) of meteorological parameters, air pollutants and aerosol species generally exceeds 0.6. On average in BTH, the heterogeneous reaction of SO2 involving aerosol water and the SO2 oxidation by OH constitutes the two most important sulfate sources, with a contribution of about 35 %–38 % and 33 %–36 % respectively. The primary emission accounts for around 22 %–24 % of sulfate concentrations due to high SO2 emissions. The SO2 oxidation by stabilized Criegee Intermediates (sCI) also plays an appreciable role in the sulfate formation, with a contribution of around 9 % when an upper limit of the reaction rate constant of sCI with SO2 (κsCI + SO2 = 3.9 × 10−11 cm3 s−1) and a lower limit of the reaction rate constant of sCI with H2O (κsCI + H2O = 1.97 × 10−18 cm3 s−1) are used. Sensitivity studies reveal that there still exist large uncertainties in the sulfate contribution of the SO2 oxidation by sCI. The sulfate contribution of the reaction is decreased to less than 3 % when κsCI + SO2 is decreased to 6.0 × 10−13 cm3 s−1. Furthermore, when κsCI + H2O is increased to 2.38 × 10−15 cm3 s−1 based on the reported ratio of κsCI + SO2 to κsCI + H2O (6.1 × 10−5), the sulfate contribution becomes insignificant, less than 2%. Further studies need to be conducted to better determine κsCI + SO2 and κsCI + H2O to evaluate effects of the sCI chemistry on the sulfate formation.

scholarly journals Effect of Electric Field on Dispersion of a Solute in an MHD Flow through a Vertical Channel With and Without Chemical Reaction

2016 ◽  
Vol 21 (3) ◽  
pp. 683-711
Author(s):  
J.C. Umavathi ◽  
J.P. Kumar ◽  
R.S.R. Gorla ◽  
B.J. Gireesha
Keyword(s):  
Diffusion Coefficient ◽  
Chemical Reaction ◽  
Short Circuit ◽  
Vertical Channel ◽  
Volumetric Flow Rate ◽  
Mhd Flow ◽  
Heterogeneous Reactions ◽  
Parallel Plates ◽  
Short Circuits ◽  
Taylor Diffusion

Abstract The longitudinal dispersion of a solute between two parallel plates filled with two immiscible electrically conducting fluids is analyzed using Taylor’s model. The fluids in both the regions are incompressible and the transport properties are assumed to be constant. The channel walls are assumed to be electrically insulating. Separate solutions are matched at the interface using suitable matching conditions. The flow is accompanied by an irreversible first-order chemical reaction. The effects of the viscosity ratio, pressure gradient and Hartman number on the effective Taylor dispersion coefficient and volumetric flow rate for an open and short circuit are drawn in the absence and in the presence of chemical reactions. As the Hartman number increases the effective Taylor diffusion coefficient decreases for both open and short circuits. When the magnetic field remains constant, the numerical results show that for homogeneous and heterogeneous reactions, the effective Taylor diffusion coefficient decreases with an increase in the reaction rate constant for both open and short circuits.

scholarly journals Effects of stabilized Criegee intermediates (sCIs) on sulfate formation: a sensitivity analysis during summertime in Beijing–Tianjin–Hebei (BTH), China

2019 ◽  
Vol 19 (21) ◽  
pp. 13341-13354 ◽  
Author(s):  
Lang Liu ◽  
Naifang Bei ◽  
Jiarui Wu ◽  
Suixin Liu ◽  
Jiamao Zhou ◽  
...  
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Heterogeneous Reaction ◽  
Reaction Rate Constant ◽  
So2 Oxidation ◽  
Formation Pathway ◽  
Criegee Intermediates ◽  
Sulfate Formation ◽  
Total Sulfate ◽  
Stabilized Criegee Intermediates

Abstract. Sulfate aerosols have profound impacts on the climate, ecosystem, visibility, and public health, but the sulfate formation pathway remains elusive. In the present study, a source-oriented WRF-Chem model is applied to simulate a persistent air pollution episode from 4 to 15 July 2015 in Beijing–Tianjin–Hebei (BTH), China, to study the contributions of four pathways to sulfate formation. When comparing simulations to measurements in BTH, the index of agreement (IOA) of meteorological parameters, air pollutants, and aerosol species generally exceeds 0.6. On average in BTH, the heterogeneous reaction of SO2 involving aerosol water and the SO2 oxidation by OH constitutes the two most important sulfate sources, with a contribution of about 35 %–38 % and 33 %–36 %, respectively. Primary sulfate emissions account for around 22 %–24 % of the total sulfate concentration. SO2 oxidation by stabilized Criegee intermediates (sCIs) also plays an appreciable role in sulfate formation, with a contribution of around 9 % when an upper limit of the reaction rate constant of sCIs with SO2 (κsCI+SO2=3.9×10-11 cm3 s−1) and a lower limit of the reaction rate constant of sCIs with H2O (κsCI+H2O=1.97×10-18 cm3 s−1) are used. Sensitivity studies reveal that there are still large uncertainties in the sulfate contribution of SO2 oxidation by sCIs. The sulfate contribution of the reaction is decreased to less than 3 % when κSCI+SO2 is decreased to 6.0×10-13 cm3 s−1. Furthermore, when κsCI+H2O is increased to 2.38×10-15 cm3 s−1 based on the reported ratio of κSCI+H2O to κSCI+SO2 (6.1×10-5), the sulfate contribution becomes insignificant at less than 2 %. Further studies need to be conducted to better determine κsCI+SO2 and κsCI+H2O to evaluate the effects of sCI chemistry on sulfate formation.

Diffusion Coefficient and Reaction Rate Constant of the SiH3Radical in Silane Plasma

1989 ◽  
Vol 28 (Part 2, No. 2) ◽  
pp. L325-L328 ◽  
Author(s):  
Naoshi Itabashi ◽  
Kozo Kato ◽  
Nobuki Nishiwaki ◽  
Toshio Goto ◽  
Chikashi Yamada ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Rate Constant ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Silane Plasma

scholarly journals Determination of exothermic batch reactor specific model parameters

2019 ◽  
Vol 292 ◽  
pp. 01063
Author(s):  
Lubomír Macků
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Specific Model ◽  
Reaction Rate Constant ◽  
Order Reaction ◽  
First Order Reaction ◽  
Model Parameters ◽  
Reactor Model ◽  
First Order

An alternative method of determining exothermic reactor model parameters which include first order reaction rate constant is described in this paper. The method is based on known in reactor temperature development and is suitable for processes with changing quality of input substances. This method allows us to evaluate the reaction substances composition change and is also capable of the reaction rate constant (parameters of the Arrhenius equation) determination. Method can be used in exothermic batch or semi- batch reactors running processes based on the first order reaction. An example of such process is given here and the problem is shown on its mathematical model with the help of simulations.

Performance of Photocatalytic Microfiltration with Hollow Fiber Membrane

2007 ◽  
Vol 544-545 ◽  
pp. 95-98 ◽  
Author(s):  
Jong Tae Jung ◽  
Jong Oh Kim ◽  
Won Youl Choi
Keyword(s):  
Heavy Metals ◽  
Humic Acid ◽  
Rate Constant ◽  
Hollow Fiber ◽  
Reaction Rate ◽  
Hollow Fiber Membrane ◽  
Membrane Surface ◽  
Reaction Rate Constant ◽  
Operational Parameters ◽  
Tio2 Particles

The purpose of this study is to investigate the effect of the operational parameters of the UV intensity and TiO2 dosage for the removal of humic acid and heavy metals. It also evaluated the applicability of hollow fiber microfiltration for the separation of TiO2 particles in photocatalytic microfiltration systems. TiO2 powder P-25 Degussa and hollow fiber microfiltration with a 0.4 μm nominal pore size were used for experiments. Under the conditions of pH 7 and a TiO2 dosage 0.3 g/L, the reaction rate constant (k) for humic acid and heavy metals increased with an increase of the UV intensity in each process. For the UV/TiO2/MF process, the reaction rate constant (k) for humic acid and Cu, with the exception of Cr in a low range of UV intensity, was higher compared to that of UV/TiO2 due to the adsorption of the membrane surface. The reaction rate constant (k) increased as the TiO2 dosage increased in the range of 0.1~0.3 g/L. However it decreased for a concentration over 0.3 g/L of TiO2. For the UV/TiO2/MF process, TiO2 particles could be effectively separated from treated water via membrane rejection. The average removal efficiency for humic acid and heavy metals during the operational time was over 90 %. Therefore, photocatalysis with a membrane is believed to be a viable process for humic acid and heavy metals removal.

Reaction rate constant of SO3+ NH3in the gas phase

1990 ◽  
Vol 95 (D9) ◽  
pp. 13981 ◽  
Author(s):  
Gaunlin Shen ◽  
Masako Suto ◽  
L. C. Lee
Keyword(s):  
Gas Phase ◽  
Rate Constant ◽  
Reaction Rate ◽  
Reaction Rate Constant

Prediction of Chemical Reaction Yield in a Microreactor and Development of a Pilot Plant Using the Numbering-Up of Microreactors

2010 ◽  
Author(s):  
Shigenori Togashi ◽  
Yukako Asano ◽  
Yoshishige Endo
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Chemical Reaction ◽  
Rate Constant ◽  
Pilot Plant ◽  
Reaction Rate ◽  
Main Product ◽  
Reaction Rate Constant ◽  
Reaction Yield ◽  
Production Scale

The chemical reaction yield was predicted by using Monte Carlo simulation. The targeted chemical reaction of a performance evaluation using the microreactor is the consecutive reaction. The main product P1 is formed in the first stage with the reaction rate constant k1. Moreover, the byproduct P2 is formed in the second stage with the reaction rate constant k2. It was found that the yield of main product P1 was improved by using a microreactor when the ratio of the reaction rate constants became k1/k2 >1. To evaluate the Monte Carlo simulation result, the yields of the main products obtained in three consecutive reactions. It was found that the yield of the main product in cased of k1/k2 >1 increased when the microreactor was uesd. Next, a pilot plant involving the numbering-up of 20 microreactors was developed. The 20 microreactor units were stacked in four sets, each containing five microreactor units arranged. The maximum flow rate when 20 microreactors were used was 1 × 104 mm3/s, which corresponds to 72 t/year. Evaluation of the chemical performance of the pilot plant was conducted using a nitration reaction. The pilot plant was found to capable of increasing the production scale without decreasing the yield of the products.

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