Catalytic Bubble Model:  Bubble Growth with an Interfacial Chemical Reaction

2004 ◽  
Vol 43 (16) ◽  
pp. 4476-4482 ◽  
Author(s):  
Moshe Favelukis ◽  
Gregory S. Yablonsky
Keyword(s):  
Chemical Reaction ◽  
Bubble Growth ◽  
Interfacial Chemical Reaction

Kinetics Calculation of the Non-isothermal Reduction of Pellet

2016 ◽  
Vol 35 (5) ◽  
pp. 507-514 ◽  
Author(s):  
Liu Yingli ◽  
Wang Jingsong ◽  
Guo Wentao ◽  
Dong Zeshang ◽  
Xue Qingguo
Keyword(s):  
Blast Furnace ◽  
Chemical Reaction ◽  
Gas Diffusion ◽  
Exponential Factor ◽  
Isothermal Method ◽  
Solid Diffusion ◽  
Initial Stage ◽  
Interfacial Chemical Reaction ◽  
Oxygen Blast ◽  
In The Beginning

AbstractThe reduction tests of pellet were carried out from room temperature to 1,373 K in the condition of traditional blast furnace (TBF) and oxygen blast furnace (OBF) by thermogravimeter measurement. The apparent activation energy E, pre-exponential factor A and the controlling steps of reaction were determined by the non-isothermal method of Coats–Redfern. In the condition of TBF, the reduction is controlled by solid diffusion to interfacial chemical reaction at initial stage, and gas diffusion at final stage. In the condition of OBF, the controlling step switched from solid diffusion to gas diffusion + interfacial chemical reaction in the beginning and the interfacial chemical reaction at the late stage. Meanwhile, the transition temperature points of the controlling step were predicted. The transition temperatures are 750℃ and 900℃ in TBF and 630℃ (earlier 120℃ than in TBF) and 900℃ (after the insulation) in OBF.

Investigation of the Interfacial Reaction between Optical Glasses and Various Protective Films and Mold Materials

2010 ◽  
Vol 297-301 ◽  
pp. 808-813 ◽  
Author(s):  
Choung Lii Chao ◽  
Cheng Bang Huo ◽  
Wen Chen Chou ◽  
Tzung Shian Wu ◽  
Kung Jeng Ma ◽  
...  
Keyword(s):  
Chemical Reaction ◽  
Optical Glass ◽  
Free Form ◽  
Molding Process ◽  
Glass Molding ◽  
Optical Glasses ◽  
Interfacial Chemical Reaction ◽  
Protective Gas ◽  
Coating Design ◽  
Almost All

The glass molding process (GMP) is regarded as a very promising technique for mass producing high precision optical components such as spherical/ aspheric glass lenses and free-form optics. However, only a handful of materials can sustain the chemical reaction, mechanical stress and temperature involved in the glass molding process. Besides, almost all of these mold materials are classified as hard-to-machine materials. This makes the machining of these materials to sub-micrometer form accuracy and nanometer surface finish a rather tough and expensive task. As a result, making mold life longer has become extremely critical in the GMP industry. The interfacial chemical reaction between optical glass and mold is normally the main reason for pre-matured mold failure. This research aimed to investigate the interfacial chemical reaction between various optical glasses, different anti-stick coating designs and several mold materials. The results showed that glass composition, coating design (composition, microstructure, thickness), environment (vacuum, air or in protective gas), reaction temperature and time could all have profound effects on the interfacial chemical reaction. Based on the results, a design developed specially for certain glasses is more likely to be the viable way of optimizing the effect of the protective coating.

Some regularities of bubble growth under chemical reaction

1979 ◽  
Vol 11 (1) ◽  
pp. 15-19
Author(s):  
V. A. Kirillov ◽  
V. P. Patskov
Keyword(s):  
Chemical Reaction ◽  
Bubble Growth

scholarly journals Reduction of New Zealand Titanomagnetite Ironsand pellets in H2 Gas at High Temperatures

2021 ◽  
Author(s):  
Ao Zhang
Keyword(s):  
Activation Energy ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Reduction Rate ◽  
Shrinking Core Model ◽  
Reduction Degree ◽  
Single Interface ◽  
Interfacial Chemical Reaction ◽  
Shrinking Core ◽  
Rate Limiting

<p><b>To reduce the emission of carbon dioxide (CO2) from industrial ironmaking in New Zealand (NZ), it is proposed to perform direct reduction (DR) of NZ titanomagnetite ironsand pellets using H2 gas. In this thesis, the H2 reduction behaviour of pellets made from the NZ ironsand are examined. The aim of the thesis is to understand the reduction mechanism, and develop an analytical kinetic model to describe the reduction progress with time. This has been addressed through a series of reduction experiments in H2 gas. The overall reduction kinetics are examined in a Thermogravimetric analysis system (TGA); the phase evolution during reduction is measured by an in-situ neutron diffraction (ND) method; and the evolution of pellet- and particle-scale morphologies are analysed by scanning electron microscopy (SEM) of quenched samples. Based on the analysis of results from these experiments, the mechanism of the reduction is found to be adequately described by a single interface shrinking core model (SCM). </b></p><p>Two different types of pellet are considered in this work: Ar-sintered pellets were sintered in an inert atmosphere to produce pellets containing mainly titanomagnetite (TTM). Pre-oxidised pellets were sintered in air to produce pellets containing mainly titanohematite (TTH). The reduction rate of both types of pellets is found to increase with reduction temperature, H2 gas flow rate, and H2 gas concentration. Above 1143 K, it is found that both types of pellets present a similar reduction rate, while below 1143 K, the reduction of pre-oxidised pellets is much faster than that of Ar-sintered pellets. For both pellets, the maximum reduction degree can reach ~97%. After complete reduction, metallic Fe coexists with other unreduced Fe-Ti-O phases (FeTiO3, TiO2 or pseudobrookite (PSB)/ferro-PSB), which is consistent with the observed reduction degree of < 100%. </p><p>During reduction of both types of pellets, any TTH present is rapidly reduced first. After this step, TTM is then reduced to FeO, with Ti becoming enriched in the remaining unreduced TTM. FeO is further reduced to metallic Fe, which makes up to ~90% reduction degree. Eventually Ti-enrichment of the TTM leads to a change in the reduction pathway and it instead directly converts to metallic Fe and FeTiO3. Above ~90% reduction degree, reduction of the remaining Fe-Ti-O phases occurs (leading to the formation of TiO2 or PSB/ferro-PSB). </p><p>The enrichment of Ti in TTM which accompanies the generation of FeO is substantially different from conventional non-titaniferous ores. This enrichment is confirmed by EDS-maps of the particles and stoichiometric calculations of the molar fraction Ti within the TTM phase. This enrichment effect changes the morphology of FeO in the particles, leading to the formation of FeO channels surrounded by Ti-enriched TTM. </p><p>At the pellet-scale, both types of pellets present a single interface shrinking core phenomenon at higher temperatures. Metallic Fe is generated from pellet surface with a reaction interface moving inwards. However, at lower temperatures this pellet-scale interface becomes less defined in the pellets. Instead, particle-scale reaction fronts are observed. </p><p>A single interface shrinking core model (SCM) is shown to successfully describe the reduction of pellets for reduction degrees < ~90% at all temperatures studied. However, at reduction degrees > ~90% this model fails. This is attributed to the change in reaction mechanism required to reduce the residual Fe-Ti-O phases that remain dispersed throughout the whole pellet at this stage of the reaction. The single interface SCM indicates that the reduction rate of the Ar-sintered pellets is controlled by the interfacial chemical reaction rate. However, two different temperature regimes are identified. Above 1193 K, the activation energy is calculated to be 41 ± 1 kJ/mol, but below 1193 K the calculated activation energy increases to 89 ± 5 kJ/mol. This change in activation energy appears to be associated with the change of the rate-limiting reaction from FeO → metallic Fe to TTM → FeO. By contrast, the pre-oxidised pellets exhibit mixed control at 1043 K, where a role is played by both the interfacial chemical reaction rate and the diffusion rate through the outer product layer. However, at temperatures of 1143 K and above, the pre-oxidised pellets also exhibit interfacial chemical reaction control, with a single activation energy of 31 ± 1 kJ/mol, which again seems to be consistent the rate-limiting reaction being FeO → metallic Fe. </p><p>In summary, the findings in this thesis contribute to understanding of the reduction of NZ ironsand pellets in H2 gas, and establish a kinetic model to describe this process. In the future, this information will be applied to develop a prototype H2-DRI shaft reactor for NZ ironsand pellets. </p>

Running droplet of interfacial chemical reaction flow

Soft Matter ◽  
2012 ◽  
Vol 8 (22) ◽  
pp. 5988 ◽  
Author(s):  
Xi Yao ◽  
Hao Bai ◽  
Jie Ju ◽  
Ding Zhou ◽  
Jing Li ◽  
...  
Keyword(s):  
Chemical Reaction ◽  
Interfacial Chemical Reaction
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