The Kinetics of the Reduction of Lead Monoxide by Hydrogen

1962 ◽  
Vol 15 (1) ◽  
pp. 40 ◽  
Author(s):  
RV Culver ◽  
IG Matthew ◽  
ECR Spooner
Keyword(s):  
Gas Flow ◽  
Reduction Rate ◽  
Gas Flow Rate ◽  
Initial Value ◽  
Lead Monoxide ◽  
Partial Pressures ◽  
Steady Rate ◽  
Rate Period ◽  
Kinetics Of ◽  
Rate Controlling Step

The rate of reduction of fused lead monoxide particles in a differential reactor with H2-N2 and H2-H2O mixtures has been measured by absorbing the H2O of reaction or chemically analysing the product, Pb-PbO. After falling from a high initial value, the reduction rate remains virtually constant until 40-50% of the PbO has been reduced, and then slowly declines. The rate of reduction is independent of the gas flow rate from 5-151. S.T.P./min and not markedly influenced by variations in particle size from -36+52 to -7+10 mesh B.S.S. With H2-N2 mixtures the rate of reduction of PbO at 575 and 675 �C is proportional to pH2, and with H2-H2O mixtures at 575 �C it is proportional to pH2/(1+0.5pH2O), where pH2, and pH2O are the partial pressures of H2 and H2O, respectively. The activation energy for reduction with H2-N2 and H2-H2O mixtures over the temperature range 475-775 �C is 39 kcal/g-mole. Chemisorption of H2 on the PbO appears the most likely rate controlling step at the Pb-PbO interface. Rates of reduction over the steady rate period, k0, are correlated by the expression k0=f(R)[pH2/(1+0 5 pH2O)] exp(-39 000/RT), where f(R) is a parameter related to particle shape and size.

Mass Transfer Coefficients during Steel Decarburization in a RH Degasser

2008 ◽  
Vol 273-276 ◽  
pp. 679-684
Author(s):  
Roberto Parreiras Tavares ◽  
André Afonso Nascimento ◽  
Henrique Loures Vale Pujatti
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Gas Flow ◽  
Vacuum Chamber ◽  
Volumetric Mass Transfer Coefficient ◽  
Gas Flow Rate ◽  
Rh Process ◽  
Kinetics Of

The RH process is a secondary refining process that can simultaneously attain significant levels of removal of interstitial elements, such as carbon, nitrogen and hydrogen, from liquid steel. In the RH process, the decarburization rate plays a very important role in determining the productivity of the equipment. The kinetics of this reaction is controlled by mass transfer in the liquid phase. In the present work, a physical model of a RH degasser has been built and used in the study of the kinetics of decarburization. The effects of the gas flow rate and of the configurations of the nozzles used in the injection of the gas have been analyzed. The decarburization reaction of liquid steel was simulated using a reaction involving CO2 and caustic solutions. The concentration of CO2 in the solution was evaluated using pH measurements. Based on the experimental results, it was possible to estimate the reaction rate constant. A volumetric mass transfer coefficient was then calculated based on these rate constants and on the circulation rate of the liquid. The logarithm of the mass transfer coefficient showed a linear relationship with the logarithm of the gas flow rate. The slope of the line was found to vary according to the relevance of the reaction at the free surface in the vacuum chamber. A linear relationship between the volumetric mass transfer coefficient and the nozzle Reynolds number was also observed. The slopes of the lines changed according to the relative importance of the two reaction sites, gas-liquid interface in the upleg snorkel and in the vacuum. At higher Reynolds number, the reaction in the vacuum chamber tends to be more significant.

Investigation of the Mechanism and Growth Kinetics of Homoepitaxial 4H-SiC Growth Using CH3Cl Carbon Precursor

2006 ◽  
Vol 527-529 ◽  
pp. 171-174 ◽  
Author(s):  
Huang De Lin ◽  
Jeffery L. Wyatt ◽  
Yaroslav Koshka
Keyword(s):  
Growth Rate ◽  
Gas Flow ◽  
Linear Trend ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Gas Flow Rate ◽  
Flow Conditions ◽  
Precursor Decomposition ◽  
Carrier Gas Flow ◽  
Kinetics Of

In this work, the mechanism of the epitaxial growth of 4H SiC using CH3Cl as the carbon source gas was investigated. The experiments were conducted with a H2 carrier gas flow rate reduced in comparison to the standard conditions used for device-quality, full-wafer C3H8 growth. Low-H2 conditions have been found favorable for investigating the differences between the two gas systems. A non-linear trend of the growth rate dependence on CH3Cl flow was observed. This dependence was quantitatively different for C3H8 growth, which serves as an indication of different kinetics of CH3Cl and C3H8 precursor decomposition, as well as differences in Si droplet formation and dissociation. The maximum growth rate that we were able to achieve was by a factor of two higher for the CH3Cl precursor than for the C3H8 precursor at the same temperature and flow conditions. The growth on lower off-axis angle substrates produced surface morphology degradation similar for both CH3Cl and C3H8 precursor systems.

The effect of gas flow rate on the oxidation kinetics of zirconium

1969 ◽  
Vol 3 (6) ◽  
pp. 377-380 ◽  
Author(s):  
L.P. Srivastava ◽  
T.F. Archbold
Keyword(s):  
Flow Rate ◽  
Oxidation Kinetics ◽  
Gas Flow ◽  
Gas Flow Rate ◽  
Kinetics Of

scholarly journals Kinetics of extracting magnesium from prefabricated pellets by silicothermic process under flowing argon atmosphere

2020 ◽  
pp. 31-31
Author(s):  
J.-H. Guo ◽  
D.-X. Fu ◽  
J.-B. Han ◽  
Z.-H. Ji ◽  
Z.-H. Dou ◽  
...  
Keyword(s):  
Diffusion Process ◽  
Atmospheric Pressure ◽  
Gas Flow ◽  
Continuous Production ◽  
Reduction Rate ◽  
Reduction Process ◽  
Control Step ◽  
Isothermal Kinetic ◽  
Carrier Gas Flow ◽  
Kinetics Of

The Pidgeon process is the main extraction method of magnesium, but its continuous production cannot be achieved due to the switch between vacuum and atmospheric pressure. Therefore, it is vital to realize continuous extraction of magnesium under atmospheric pressure. In this paper, the process of extracting magnesium from prefabricated pellets in flowing argon was proposed. The isothermal kinetic analysis of the reduction process was carried out, the results showed that the reduction process was controlled by diffusion process in 1 h, and the apparent activation energy of extracting magnesium from prefabricated pellets in flowing argon was 218.75 kJ/mol. Then the influence of experimental factors on the reduction rate was explored, including briquetting pressure, carrier gas flow rate, ferrosilicon content, reaction temperature and time. Through analysis and calculation, it was concluded that the main control step of diffusion process was silicon diffusion.

Mathematical modeling of aluminum degassing by the impeller injector technique validated by a physical modeling

2014 ◽  
Vol 1611 ◽  
pp. 49-54 ◽  
Author(s):  
M. Hernández-Hernández ◽  
W. F. Cruz-Mendez ◽  
C. Gonzalez-Rivera ◽  
M. A. Ramírez-Argáez
Keyword(s):  
Mathematical Model ◽  
Physical Model ◽  
Gas Flow ◽  
Process Analysis ◽  
Liquid Aluminum ◽  
Bubble Diameter ◽  
Operating Parameter ◽  
Gas Flow Rate ◽  
The Mathematical Model ◽  
Kinetics Of

ABSTRACTA mathematical model is developed to describe deoxidation of water in a physical model of a batch aluminum degassing reactor equipped with the rotor-injector technique, assuming that deoxidation kinetics of water is similar to dehydrogenization of liquid aluminum. Degassing kinetics is described by using mass transport and mass balance principles by assuming that degassing kinetics can be characterized by a mass transfer coefficient, which depends on the process variables. The transport coefficient and the average bubble diameter are estimated with correlations reported in the literature for similar gas-injection systems. The water physical model helped to validate the mathematical model and to perform a process analysis by varying: 1) Gas flow rate (20 and 40 l/min); and 2) Impeller’s angular velocity (290 and 573 rpm). Results from the model agree well with measurements of deoxidation kinetics at low impeller rotating speeds. At high rotating speeds the model is still valid but less reliable because it does not take into account the formation of the vortex at the free surface. Nevertheless, the model provides predictions of the influence of every operating parameter and it can be used as a good approximation for real systems.

scholarly journals Kinetic Aspects of Phosphorus Removal from Electromagnetically Levitated 600 MPa Steel Droplets

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1460
Author(s):  
Qi Jiang ◽  
Guifang Zhang ◽  
Yindong Yang ◽  
Alexander McLean ◽  
Lei Gao
Keyword(s):  
Gas Phase ◽  
Flow Rate ◽  
Phosphorus Removal ◽  
Gas Flow ◽  
Electromagnetic Levitation ◽  
Effect Of Temperature ◽  
Gas Flow Rate ◽  
Electromagnetically Levitated ◽  
Rate Controlling Step ◽  
Good Agreement

A kinetic model was developed to study the dephosphorization of 600 MPa steel droplets under electromagnetic levitation conditions. The relationships which were derived from the model between dephosphorization and the influence of temperature and gas flow rate were in good agreement with experimental data. Both temperature and gas flow rate were conducive to the evaporation of phosphorus, with the effect of temperature having a greater influence than that of the gas velocity. The results show that the rate-controlling step for the dephosphorization process was diffusion within the gas phase. This work aims to provide a theoretical basis for process optimization during the dephosphorization of 600 MPa steel.

scholarly journals A Kinetic Comparison between Laboratory and Industrial Scales in the Copper Blowing Process

2009 ◽  
Vol 2009 ◽  
pp. 1-5
Author(s):  
A. Roselló ◽  
J. Martínez ◽  
F. Carrillo
Keyword(s):  
Oxygen Pressure ◽  
Gas Flow ◽  
Reaction Rate ◽  
Operation Time ◽  
Gas Flow Rate ◽  
Melt Temperature ◽  
Desulfurization Rate ◽  
Flow Rates ◽  
Peirce Smith Converter ◽  
Kinetics Of

An experimental investigation into the oxidation kinetics of molten sulfide has been conducted at laboratory scale to provide information concerning the influence of the gas feed (flow and oxygen pressure) and melt temperature on the desulfurization rate. Data showed that the reaction rate was strongly dependent on the gas flow rate and significantly from oxygen pressure, whereas the influence of temperature was negligible. The variation of the sulfur conversion with the operation time was similar to that found in industrial trials when “white metal” was blown to blister copper in a Peirce-Smith converter. A unique equation for both scales could be established. This correlation made it possible to calculate the operation time in the converter at different gas flow rates and oxygen enrichments.

Effect of Humidity on Carbon Monoxide Desorption Kinetics

2014 ◽  
Vol 11 (4) ◽  
Author(s):  
F. Dundar ◽  
A. Pitois ◽  
A. Pilenga ◽  
G. Tsotridis
Keyword(s):  
Carbon Monoxide ◽  
Gas Flow ◽  
Platinum Catalyst ◽  
Kinetic Constant ◽  
Pem Fuel Cells ◽  
Desorption Kinetics ◽  
Gas Flow Rate ◽  
Desorption Kinetic ◽  
Negative Effect ◽  
Kinetics Of

The kinetics of carbon monoxide desorption on a platinum catalyst under humidified conditions were investigated with the steady state isotropic transient kinetic analysis (SSITKA) method. The effect of the humidity level on desorption kinetics was quantified. The carbon monoxide (CO) desorption kinetic constant was calculated regardless of the gas flow rate. The kinetic constant dropped up to 58% with the increasing relative humidity. The negative effect of humidity in terms of CO poisoning for PEM fuel cells was determined.

Oxygen partial pressures; control, variation, and measurement in quench furnaces at one atmosphere total pressure

1974 ◽  
Vol 39 (305) ◽  
pp. 580-586 ◽  
Author(s):  
Gordon M. Biggar
Keyword(s):  
Oxygen Pressure ◽  
Atmospheric Pressure ◽  
Total Pressure ◽  
Gas Flow ◽  
Careful Analysis ◽  
Gas Mixture ◽  
Gas Flow Rate ◽  
Partial Pressures ◽  
Control Variation ◽  
Made In

SummaryOxygen partial pressures in atmospheric-pressure quench furnaces were found to vary by as much as 0·5 in log fo2 when changes were made in gas flow rate and direction suggesting that careful analysis of the gas mixture supplied to a furnace is not a guarantee of the oxygen pressure that a sample in the furnace will attain. The use of magnesiowüstite compositions, with variable oxygen contents, as indicators of oxygen pressure is described.

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