scholarly journals Carbothermic Reduction of Zinc Containing Industrial Wastes: A Kinetic Model

2021 ◽  
Author(s):  
M. Leuchtenmueller ◽  
C. Legerer ◽  
U. Brandner ◽  
J. Antrekowitsch
Keyword(s):  
Mass Transfer ◽  
Zinc Oxide ◽  
Kinetic Model ◽  
Large Scale ◽  
Industrial Wastes ◽  
Oxide Reduction ◽  
Transfer Coefficients ◽  
Metallothermic Reduction ◽  
Metal Bath ◽  
Zinc Recovery

AbstractEffective recycling of zinc-containing industrial wastes, most importantly electric arc furnace dust, is of tremendous importance for the circular economy of the steel and zinc industry. Herein, we propose a comprehensive kinetic model of the combined carbothermic and metallothermic reduction of zinc oxide in a metal bath process. Pyro-metallurgical, large-scale lab experiments of a carbon-saturated iron melt as reduction agent for a molten zinc oxide slag were performed to determine reaction constants and accurately predict mass transfer coefficients of the proposed kinetic model. An experimentally determined kinetic model demonstrates that various reactions run simultaneously during the reduction of zinc oxide and iron oxide. For the investigated slag composition, the temperature-dependent contribution of the metallothermic zinc oxide reduction was between 25 and 50 pct of the overall reaction mechanism. The mass transfer coefficient of the zinc oxide reduction quadrupled from 1400 °C to 1500 °C. The zinc recovery rate was > 99.9 pct in all experiments.

Mass Transfer Coefficients for a Bingham Fluid and Water With and Without Anti-Foam Agents

2008 ◽  
Author(s):  
Robert A. Leishear ◽  
Hector N. Guerrero ◽  
Michael L. Restivo ◽  
David J. Sherwood
Keyword(s):  
Mass Transfer ◽  
Yield Stress ◽  
Large Scale ◽  
Volumetric Flow Rate ◽  
Bingham Fluid ◽  
Superficial Velocity ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Bingham Plastic ◽  
Single Pipe

The equations describing mass transfer coefficients are rather concise, but experimental data is required to determine the coefficients. Here, mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and a Bingham plastic fluid, referred to as AZ101 simulant. The Bingham fluid differed from water since it required an applied yield stress to initiate flow. Newtonian fluids, like water, have a zero yield stress. Each of the fluids was saturated with oxygen, and the oxygen was removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single pipe which was co-axial to the column. The decrease in oxygen concentration was recorded, and the oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Mass transfer data for 24 different test conditions were determined. Superficial sparging velocities of 2, 5, and 10 mm/second were applied to each of the simulants at three different column fill levels, where the superficial velocity is defined as the average volumetric flow rate divided by the liquid surface area in the column. Mass transfer coefficient test results are presented herein for each test combination of superficial velocity and fluid level.

scholarly journals Mass Transfer Coefficients for a Non-Newtonian Fluid and Water With and Without Antifoam Agents

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Robert A. Leishear ◽  
Hector N. Guerrero ◽  
Michael L. Restivo ◽  
David J. Sherwood
Keyword(s):  
Mass Transfer ◽  
Nuclear Waste ◽  
Large Scale ◽  
Test Results ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Transfer Rates ◽  
Mass Transfer Processes ◽  
Fluid Levels ◽  
Oxygen Measurements

Mass transfer rates were measured in a large scale system, which is consisted of an 8.4 m tall by 0.76 m diameter column, containing one of the three fluids: water with an antifoam agent, water without an antifoam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated and due to flammability concerns, oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from the solution as air bubbled up or sparged through the solution from the bottom of the column. Air sparging was supplied by a single tube, which was co-axial to the column; the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2 mm/s, 5mm/s, and 10 mm/s were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels.

scholarly journals Extraction of Clove and Vetiver Oils with Supercritical Carbon Dioxide: Modeling and Simulation

2007 ◽  
Vol 1 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Julian Martínez ◽  
Paulo T.V. Rosa ◽  
M. Angela A. Meireles
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Large Scale ◽  
Raw Material ◽  
Feed Ratio ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Extraction Curve ◽  
Kinetics Of

The kinetics of supercritical fluid extraction (SFE) of clove and vetiver oils using carbon dioxide as solvent was studied, in order to establish an efficient method to predict extraction curves on large scale. The mass transfer model of Sovová was used to adjust the experimental SFE data, which were obtained at 100 bar and 35 °C for clove and 200 bar and 40 °C for vetiver, using extraction columns of different geometry and solvent flow rates. Some other process parameters, such as bed density and porosity, solvent to feed ratio and solvent velocity were kept constant from one experiment to another, in order to verify if the mass transfer coefficients adjusted by the model varied. The results show that the model of Sovová was able to predict an overall extraction curve for clove from data obtained with twenty times less raw material, since the mass transfer coefficients remained the same and the predicted curves were similar to the observed ones. For vetiver, the simulation was not as effective, probably due to the effects of transport properties on the process.

Evaluation of Wall Thinning of PWR Feed Water Piping With the Coupled Model of Static Electrochemical Analysis and Dynamic Double Oxide Layer Analysis

2010 ◽  
Author(s):  
Masanori Naitoh ◽  
Shunsuke Uchida ◽  
Hidetoshi Okada ◽  
Taku Ohira ◽  
Seiichi Koshizuka
Keyword(s):  
Mass Transfer ◽  
Oxide Layer ◽  
Large Scale ◽  
Electrochemical Analysis ◽  
Turbulence Energy ◽  
Feed Water ◽  
Transfer Coefficients ◽  
Oxygen Injection ◽  
Mass Transfer Coefficients ◽  
Wall Thinning

In order to confirm applicability and accuracy of FAC evaluation methods based on the coupled FAC model of static electrochemical analysis and dynamic oxide layer growth analysis, wall thinning rates calculated with the proposed methods were compared with those measured for the secondary piping of a PWR plant. Flow turbulence at major parts of the system was calculated with 3D CFD codes and extrapolated to the very surface of piping wall to obtain mass transfer coefficients at boundary layers of the structure surfaces. Then, wall thinning rates were calculated with the coupled FAC model by applying the mass transfer coefficients. Major conclusions are as follows: 1) Flow distribution calculated with 3D CFD codes could be extrapolated by applying 2/7 power law of turbulence energy as a function of distance from the surface to those at the very surface of the piping to obtain a precise distribution of mass transfer coefficients. 2) Wall thinning rates calculated for large scale piping of a PWR by applying the obtained mass transfer coefficients agreed with the measured rates within a factor of 2. 3) As a result of demonstration of the FAC evaluation model, it was confirmed that suitable amount of oxygen injection into the feed water resulted sufficient mitigation of FAC without any serious adverse effect on steam generator tubing.

Effect of Blade Tip Clearance on Turbine Shroud Heat/Mass Transfer

2001 ◽  
Author(s):  
Dong Ho Rhee ◽  
Jong Hyun Choi ◽  
Hyung Hee Cho
Keyword(s):  
Mass Transfer ◽  
Heat Mass Transfer ◽  
Large Scale ◽  
Local Heat ◽  
Tip Clearance ◽  
Pressure Side ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Transfer Characteristics ◽  
Blade Tip

This study investigates the local heat/mass transfer characteristics on the stationary shroud with blade tip clearances for flat tip geometry. A large scale linear cascade is used and the relative motion between the blade and shroud is neglected in this study. A naphthalene sublimation method is employed to determine the detailed local heat/mass transfer coefficients on the shroud surface. The geometry of blade tip used in this study is flat and the tip clearance varies from 0.66% to 2.85% of the blade chord length. The flow enters the gap between the blade tip and shroud at the pressure side due to the pressure difference. Therefore, the heat/mass transfer characteristics on the shroud are changed significantly from those for no tip clearance. High heat/mass transfer region is observed along the pressure side of blade due to the entrance effect and the acceleration of the tip gap flow. Complex heat transfer patterns on the shroud are observed in the region where the blade tip and shroud are overlapped due to the flow separation and reattachment. Then, the heat/mass transfer coefficients on the shroud increase along the suction side of blade because tip leakage vortices are generated with interacting the main flow. The experimental results show that the heat/mass transfer characteristics are changed significantly with the gap distance between the tip of turbine blade and the shroud. However, the turbulence intensity of incoming flow has little influence on the heat/mass transfer coefficients on the shroud with tip clearance.

scholarly journals Adsorption for efficient low carbon hydrogen production: part 1—adsorption equilibrium and breakthrough studies for H2/CO2/CH4 on zeolite 13X

Adsorption ◽  
2021 ◽  
Author(s):  
Anne Streb ◽  
Marco Mazzotti
Keyword(s):  
Mass Transfer ◽  
Large Scale ◽  
Carbon Capture And Storage ◽  
Low Carbon ◽  
Transport Parameters ◽  
Transfer Coefficients ◽  
Predictive Capacity ◽  
Zeolite 13X ◽  
Lower Accuracy ◽  
Breakthrough Experiments

Abstract Reforming of fossil fuels coupled with carbon capture and storage has the potential to produce low-carbon H2 at large scale and low cost. Adsorption is a potentially promising technology for two key separation tasks in this process: H2 purification and CO2 capture. In this work, we present equilibrium adsorption data of H2 and CH4 on zeolite 13X, in addition to the already established CO2 isotherms. Further, we carry out binary (CO2–CH4) and ternary (H2–CO2–CH4) breakthrough experiments at various pressures and temperatures to estimate transport parameters, assess the predictive capacity of our 1D column model, and compare different multi-component adsorption models. CO2 adsorbs strongly on zeolite 13X, CH4 adsorbs less, and H2 adsorbs very little. Thus, H2 breaks through first, CH4 second (first in the binary breakthrough experiments) and CO2 last. Linear driving force (LDF) mass transfer coefficients are estimated based on a single breakthrough experiment and mass transfer is found to be fast for H2, slower for CH4, and slowest for CO2. The LDF parameters can be used in a predictive manner for breakthrough experiments at varying pressures, temperatures, flows, and, though with lower accuracy, even compositions. Heat transfer inside the column is described well with a literature correlation, thus yielding an excellent agreement between simulated and measured column temperatures. Ideal and real adsorbed solution theories (IAST and RAST, respectively) both model the observed breakthrough composition profiles well, whereas extended isotherms are inferior for predicting the competitive behavior between CH4 and CO2 adsorption. This study provides the groundwork necessary for full cyclic experiments and their simulation.

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