Splitting Water and Carbon Dioxide via the Heterogeneous Oxidation of Zinc Vapor: Thermodynamic Considerations

2010 ◽  
Author(s):  
Luke J. Venstrom ◽  
Jane H. Davidson
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Carbon Monoxide ◽  
Reaction Path ◽  
Zinc Vapor ◽  
Complete Conversion ◽  
Heterogeneous Oxidation ◽  
Carbon Dioxide Splitting ◽  
Heat Recuperation ◽  
Splitting Water

The heterogeneous hydrolysis/oxidation of zinc vapor is proposed as a promising reaction path for the exothermic step in two-step Zn/ZnO solar thermochemical water and carbon dioxide splitting cycles. This approach circumvents mass transfer limitations encountered in the oxidation of solid or liquid zinc, promising rapid hydrogen/carbon monoxide production rates and complete conversion of zinc. In this paper, a parametric thermodynamic analysis is presented to quantify the penalty of generating zinc vapor as well as the benefit of achieving complete conversion of zinc via the heterogeneous oxidation of zinc vapor. The penalty for generating zinc vapor is a reduction in water splitting efficiency from 36% to 27% and a reduction in carbon dioxide splitting efficiency from 39% to 31%. However, with heat recuperation this penalty can be avoided. The benefit of completely converting zinc via the heterogeneous oxidation of zinc vapor is an increase in efficiency from ∼6% to 27% and 31% for water and carbon dioxide splitting, respectively.

Splitting Water and Carbon Dioxide via the Heterogeneous Oxidation of Zinc Vapor: Thermodynamic Considerations

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Luke J. Venstrom ◽  
Jane H. Davidson
Keyword(s):  
Carbon Dioxide ◽  
Reaction Times ◽  
Zinc Vapor ◽  
Complete Conversion ◽  
Heterogeneous Oxidation ◽  
Aerosol Reactors ◽  
Carbon Dioxide Splitting ◽  
Heat Recuperation ◽  
Cycle Efficiency ◽  
Splitting Water

The heterogeneous oxidation of zinc vapor is proposed as a promising reaction path for the exothermic step in the two-step Zn/ZnO solar thermochemical water and carbon dioxide splitting cycles. This approach circumvents mass transfer limitations encountered in the oxidation of solid or liquid zinc, promising rapid hydrogen and carbon monoxide production rates concurrent with a complete conversion of zinc to zinc oxide. In this paper, a parametric thermodynamic analysis is presented to quantify the benefit of achieving a rapid and complete conversion of zinc via the heterogeneous oxidation of zinc vapor. The conversion of zinc in polydisperse aerosol reactors has been limited to 20% for reaction times on the order of a minute, resulting in a cycle efficiency of ∼6%. The benefit of completely converting zinc via the heterogeneous oxidation of zinc vapor is an increase in efficiency to 27% and 31% for water and carbon dioxide splitting, respectively. The cycle efficiency could be higher if heat recuperation is implemented.

Heterogeneous oxidation of zinc vapor by steam and mixtures of steam and carbon dioxide

2018 ◽  
Vol 183 ◽  
pp. 223-230 ◽  
Author(s):  
Luke J. Venstrom ◽  
Paul Hilsen ◽  
Jane H. Davidson
Keyword(s):  
Carbon Dioxide ◽  
Zinc Vapor ◽  
Heterogeneous Oxidation

Mathematical Modeling of Heat and Mass Transfer Processes During Pyrolysis and Combustion of a Single Biomass Particle

2012 ◽  
Author(s):  
Y. Haseli ◽  
J. A. van Oijen ◽  
L. P. H. de Goey
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Carbon Monoxide ◽  
Water Vapor ◽  
Gas Phase ◽  
Combustion Process ◽  
Combustion Model ◽  
Gas Phase Reactions ◽  
Transfer Processes ◽  
Mass Transfer Processes

A detailed mathematical model is developed for simulation of heat and mass transfer processes during the pyrolysis and combustion of a single biomass particle. The kinetic scheme of Shafizadeh and Chin is employed to describe the pyrolysis process. The light gases formed during the biomass pyrolysis is assumed to consist of methane, carbon dioxide, carbon monoxide, hydrogen and water vapor with given mass fractions relevant to those found in the experiments of high heating conditions. The combustion model takes into account the reactions of oxygen with methane, hydrogen, carbon monoxide, tar and char as well as gasification of char with water vapor and carbon dioxide. Appropriate correlations taken from past studies are used for computation of the rate of these reactions. The model allows calculation of time and space evolution of various parameters including biomass and char densities, gaseous species and temperature. Different experimental data reported in the literature are employed to validate the pyrolysis and combustion models. The reasonable agreement obtained between the predictions and measured data reveals that the presented model is capable of successfully capturing various experiments of wood particle undergoing a pyrolysis or combustion process. In particular, the role of gas phase reactions within and adjacent to particle on the combustion process is examined. The results indicate that for the case of small particles in the order of millimeter size and less, one may neglect any effects of gas phase reactions. However, for larger particles, a combustion model may need to include hydrogen oxidation and even carbon monoxide combustion reactions.

Thermodynamic Analysis of the Ceria Redox Cycle With Methane-Driven Reduction for Solar Fuel Production

2014 ◽  
Author(s):  
Peter Krenzke ◽  
Jane Davidson
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Reduction Reaction ◽  
Liquid Fuels ◽  
Chemical Bonds ◽  
Redox Cycle ◽  
Low Oxygen ◽  
Fuel Production ◽  
Partial Pressures ◽  
Splitting Water

The nonstoichiometric cerium oxide (ceria) redox cycle is an attractive pathway for storing energy from concentrated sunlight in chemical bonds by splitting water and carbon dioxide. The endothermic reduction reaction (R1)CeO2-δox→CeO2-δed+Δδ2O2 is favored thermodynamically at high temperatures and low oxygen partial pressures, while the CO2 and H2O splitting reactions (R2, R3) are exothermic and favored at lower temperatures and higher oxygen partial pressures. The produced hydrogen and carbon monoxide, referred to collectively as syngas, are important feedstocks used in the synthesis of ammonia and liquid fuels.(R2)CeO2-δed+ΔδCO2→CeO2-δox+ΔδCO   (R3)CeO2-δed+ΔδH2O→CeO2-δox+ΔδH2

scholarly journals Controlled atmosphere GMAW welding of transportation vehicles and production machines parts made from 30MnB5 steel

2018 ◽  
Vol 216 ◽  
pp. 03001 ◽  
Author(s):  
Evgeny Ivanayskiy ◽  
Aleksei Ishkov ◽  
Aleksandr Ivanayskiy ◽  
Iakov Ochakovskii
Keyword(s):  
Mechanical Properties ◽  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Chemical Composition ◽  
Controlled Atmosphere ◽  
Shielding Gas ◽  
Reducing Atmosphere ◽  
Metal Composition ◽  
Gmaw Welding ◽  
Welding Materials

The paper studies the influence of shielding gas on the composition and the structure of weld joint metal of 30MnB5 steel applied in essential parts of automobiles and tractors. The welding was performed in inert, oxidizing and reducing atmospheres. It was established that TIG welding with argon used as shielding gas did not provide the required mechanical properties when using conventional welding materials. Carbon dioxide during MAG welding caused partial burning of alloying elements. Carbon monoxide used as shielding gas was proved to form reducing atmosphere enabling to obtain chemical composition close to the base metal composition. Metallographic examinations were carried out. The obtained results provided full-strength weld, as well as the required reliability and durability of welded components and joints.

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