scholarly journals Solar Carbo-Thermal and Methano-Thermal Reduction of MgO and ZnO for Metallic Powder and Syngas Production by Green Extractive Metallurgy

Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 154
Author(s):  
Srirat Chuayboon ◽  
Stéphane Abanades
Keyword(s):  
Solar Energy ◽  
Total Pressure ◽  
Extractive Metallurgy ◽  
Thermal Reduction ◽  
Operating Conditions ◽  
Equilibrium Analysis ◽  
Metallurgical Process ◽  
Solid Carbon ◽  
Solar Reactor ◽  
Reaction Extent

The solar carbo-thermal and methano-thermal reduction of both MgO and ZnO were performed in a flexible solar reactor operated at low pressure through both batch and continuous operations. The pyro-metallurgical process is an attractive sustainable pathway to convert and store concentrated solar energy into high-value metal commodities and fuels. Substituting fossil fuel combustion with solar energy when providing high-temperature process heat is a relevant option for green extractive metallurgy. In this study, a thermodynamic equilibrium analysis was first performed to compare the thermochemical reduction of MgO and ZnO with solid carbon or gaseous methane, and to determine the product distribution as a function of the operating conditions. The carbo-thermal and methano-thermal reduction of the MgO and ZnO volatile oxides was then experimentally assessed and compared using a directly irradiated cavity-type solar reactor under different operating conditions, varying the type of carbon-based reducing agent (either solid carbon or methane), temperature (in the range 765–1167 °C for ZnO and 991–1550 °C for MgO), total pressure (including both reduced 0.10–0.15 bar and atmospheric ~0.90 bar pressures), and processing mode (batch and continuous operations). The carbo-thermal and methano-thermal reduction reactions yielded gaseous metal species (Mg and Zn) which were recovered at the reactor outlet as fine and reactive metal powders. Reducing the total pressure favored the conversion of both MgO and ZnO and increased the yields of Mg and Zn. However, a decrease in the total pressure also promoted CO2 production because of a shortened gas residence time, especially in the case of ZnO reduction, whereas CO2 formation was negligible in the case of MgO reduction, whatever the conditions. Continuous reactant co-feeding (corresponding to the mixture of metal oxide and carbon or methane) was also performed during the solar reactor operation, revealing an increase in both gas production yields and reaction extent while increasing the reactant feeding rate. The type of carbon reducer influenced the reaction extent, since a higher conversion of both MgO and ZnO was reached when using carbon with a highly available specific surface area for the reactions. The continuous solar process yielded high-purity magnesium and zinc content in the solar-produced metallic powders, thus confirming the reliability, flexibility, and robustness of the solar reactor and demonstrating a promising solar metallurgical process for the clean conversion of both metal oxides and concentrated solar light to value-added chemicals.

Effect of Cameralike Aperture in Quest for Maintaining Quasi-Constant Radiation Inside a Solar Reactor

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Nesrin Ozalp ◽  
Anthony Toyama ◽  
Jayakrishna Devanuri ◽  
Reza Rowshan ◽  
Yasser Al-Hamidi
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Operating Conditions ◽  
Solar Flux ◽  
Process Efficiency ◽  
Distribution Model ◽  
Internal Temperature ◽  
Aperture Diameter ◽  
Small Surface ◽  
Solar Reactor

Solar reactors can convert intermittent solar radiation into storable chemical energy in the form of fuels that are transportable. In order to use solar energy as a source of high temperature process heat in a solar reactor, incident radiation needs to be concentrated over a small surface area, the inlet of which is called the aperture. The image of the incoming solar radiation over the aperture can be approximated by a Gaussian distribution where the solar radiation inside the reactor varies by the peak value and aperture size. Due to the transient nature of solar energy, there is a critical need for proper control to maximize system efficiency under field conditions. The objective of this paper is to present numerically proven advantages of having a camera-like variable aperture, one that is sensitive to natural variations in solar flux, and having the ability to shrink or enlarge accordingly in order to maintain quasi-constant radiation inside the reactor. Since the internal temperature has a major impact on reactant to product conversion efficiency, by maintaining the temperature constant, process efficiency is kept high. By maintaining the internal temperature despite transient operating conditions, the system can maintain peak performance through a wider insolation range than fixed aperture systems. Our numerical results from optical, thermodynamic, and flow dynamic simulations led us to develop a computational two dimensional heat transfer distribution model inside the reactor in order to validate our optical results. The combined simulation results show that correctly varying the aperture diameter with respect to transient incoming solar flux densities facilitates the maintenance of quasi-constant temperature distributions inside the reactor.

Effect of Camera-Like Aperture in Quest for Maintaining Quasi-Constant Radiation Inside a Solar Reactor

2010 ◽  
Author(s):  
Nesrin Ozalp ◽  
Anthony Toyama ◽  
D. Jaya Krishna ◽  
Reza Rowshan ◽  
Yasser Al-Hamidi
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Operating Conditions ◽  
Solar Flux ◽  
Process Efficiency ◽  
Distribution Model ◽  
Peak Performance ◽  
Aperture Diameter ◽  
Small Surface ◽  
Solar Reactor

Solar reactors can convert intermittent solar radiation into storable chemical energy in the form of fuels that are transportable. In order to use solar energy as a source of high temperature process heat in a solar reactor, incident radiation needs to be concentrated over a small surface area, the inlet of which is called the aperture. The image of the incoming solar radiation over the aperture can be approximated by a Gaussian distribution where the solar radiation inside the reactor varies by the peak value and aperture size. Due to the transient nature of solar energy, there is a critical need for proper control to maximize system efficiency under field conditions. This paper provides numerically proven advantages of having a camera-like variable aperture, one which is sensitive to natural variations in solar flux, and having the ability to shrink or enlarge accordingly in order to maintain quasi-constant radiation inside the reactor. Our numerical results from optical, thermodynamic, and flow dynamic simulations led us to develop a computational two dimensional heat transfer distribution model inside the reactor in order to validate our optical results. The simulation results show that a changing aperture diameter with respect to a changing incoming solar flux density facilitates keeping quasi-constant and homogenous temperature distributions inside the reactor. Since the temperature has a major impact on reactant to product conversion efficiency, by keeping the temperature constant, process efficiency is kept high. By maintaining the internal temperature despite variable operating conditions the system can maintain peak performance through a wider insolation range than fixed aperture systems.

Monte Carlo Heat Transfer Modeling of a Particle-Cloud Solar Reactor for SnO2 Thermal Reduction

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
H. I. Villafán-Vidales ◽  
C. A. Arancibia-Bulnes ◽  
S. Abanades ◽  
D. Riveros-Rosas ◽  
H. Romero-Paredes
Keyword(s):  
Monte Carlo ◽  
Power Distribution ◽  
Particle Temperature ◽  
Average Diameter ◽  
Thermal Reduction ◽  
Particle Cloud ◽  
Operational Conditions ◽  
Solar Reactor ◽  
Concentrated Solar Energy ◽  
Reaction Extent

A directly irradiated cavity solar reactor devoted to the thermal reduction of SnO2 particle-cloud is studied numerically by using the Monte Carlo method. The steady-state model solves the radiation and convection heat transfers in the semitransparent particle suspension and the chemical reaction. It was used to predict the temperature distribution and the reaction extent inside the cavity, as well as the theoretical thermochemical efficiency for different operational conditions. The simulations assume that the reactor contains a nonuniform size suspension of radiatively participating reacting SnO2 particles. The model takes into account the radiative characteristics of the particles, as well as the directional characteristics of the power distribution of the incoming concentrated solar energy. The particle concentration, the particle size, and the length of the reactor are varied. Results show that the particle temperature and the yield of the endothermic reaction are higher when the reactor is fed with a cloud of particles with average diameter of 20 μm. The maximal thermochemical efficiency reached is 10%, which corresponds to an optimal optical thickness of around 2.

scholarly journals Non-Stoichiometric Redox Active Perovskite Materials for Solar Thermochemical Fuel Production: A Review

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 611 ◽  
Author(s):  
Anita Haeussler ◽  
Stéphane Abanades ◽  
Julien Jouannaux ◽  
Anne Julbe
Keyword(s):  
Carbon Dioxide ◽  
Solar Energy ◽  
Energy Conversion ◽  
Operating Conditions ◽  
Solar Fuel ◽  
Fuel Production ◽  
Concentrated Solar Energy ◽  
Redox Active ◽  
Conversion Rates ◽  
Wide Range

Due to the requirement to develop carbon-free energy, solar energy conversion into chemical energy carriers is a promising solution. Thermochemical fuel production cycles are particularly interesting because they can convert carbon dioxide or water into CO or H2 with concentrated solar energy as a high-temperature process heat source. This process further valorizes and upgrades carbon dioxide into valuable and storable fuels. Development of redox active catalysts is the key challenge for the success of thermochemical cycles for solar-driven H2O and CO2 splitting. Ultimately, the achievement of economically viable solar fuel production relies on increasing the attainable solar-to-fuel energy conversion efficiency. This necessitates the discovery of novel redox-active and thermally-stable materials able to split H2O and CO2 with both high-fuel productivities and chemical conversion rates. Perovskites have recently emerged as promising reactive materials for this application as they feature high non-stoichiometric oxygen exchange capacities and diffusion rates while maintaining their crystallographic structure during cycling over a wide range of operating conditions and reduction extents. This paper provides an overview of the best performing perovskite formulations considered in recent studies, with special focus on their non-stoichiometry extent, their ability to produce solar fuel with high yield and performance stability, and the different methods developed to study the reaction kinetics.

Solar Gasification of Biomass: A Molten Salt Pyrolysis Study

2004 ◽  
Vol 126 (3) ◽  
pp. 850-857 ◽  
Author(s):  
Roman Adinberg ◽  
Michael Epstein ◽  
Jacob Karni
Keyword(s):  
Solar Energy ◽  
Molten Salt ◽  
Operating Conditions ◽  
Thermochemical Conversion ◽  
Salt Medium ◽  
Feasible Option ◽  
Temperature Liquid ◽  
Set Up ◽  
Biomass Particles ◽  
Pyrolysis Of Biomass

A novel solar process and reactor for thermochemical conversion of biomass to synthesis gas is described. The concept is based on dispersion of biomass particles in a molten inorganic salt medium and, simultaneously, absorbing, storing and transferring solar energy needed to perform pyrolysis reactions in the high-temperature liquid phase. A lab-scale reactor filled with carbonates of potassium and sodium was set up to study the kinetics of fast pyrolysis and the characteristics of transient heat transfer for cellulose particles (few millimeters size) introduced into the molten salt medium. The operating conditions were reaction temperatures of 1073–1188 K and a particle peak-heating rate of 100 K/sec. The assessments performed for a commercial-scale solar reactor demonstrate that pyrolysis of biomass particles dispersed in a molten salt phase could be a feasible option for the continuous, round-the-clock production of syngas, using solar energy only.

scholarly journals Solar Metallurgy for Sustainable Zn and Mg Production in a Vacuum Reactor Using Concentrated Sunlight

2020 ◽  
Vol 12 (17) ◽  
pp. 6709 ◽  
Author(s):  
Srirat Chuayboon ◽  
Stéphane Abanades
Keyword(s):  
Carbon Black ◽  
Metal Oxides ◽  
Activated Charcoal ◽  
Carbothermal Reduction ◽  
Total Pressure ◽  
Operation Mode ◽  
Inert Atmosphere ◽  
Pure Metal ◽  
Reactor Outlet ◽  
Reaction Extent

Solar carbothermal reduction of volatile metal oxides represents a promising pyro-metallurgical pathway for the sustainable conversion of both metal oxides and sunlight into metal commodities and fuels in a single process. Nevertheless, there are several scientific challenges in discovering suitable metal oxides candidates for the ease of oxygen extraction from metal oxides to enhance the reaction extent and in designing reactors for the efficient absorption of incident solar radiation to minimize losses. In this study, ZnO and MgO were considered as volatile metal oxides candidates, and their reaction behaviors were studied and compared through gas species production rate, metal oxides conversion, and yield. A solar reactor prototype was developed to facilitate solar carbothermal reduction of ZnO and MgO with different reducing agents comprising activated charcoal and carbon black. The process was operated in a batch operation mode under vacuum and atmospheric pressures to demonstrate the flexibility and reliability of this system for co-production of metals (Zn/Mg) and CO. As a result, decreasing total pressure enhanced conversion of ZnO and MgO, leading to increased Zn and Mg. However, in the case of ZnO, CO yield decreased with decreasing total pressure at the expense of favored CO2 as a result of the decrease of residence time. In contrast, CO2 formation was negligible in the case of MgO, and CO yield thus increased with decreasing pressure. Using activated charcoal as the reducing agent exhibited better conversion of both ZnO and MgO than carbon black thanks to the higher available specific surface area for chemical reactions. MgO and ZnO conversion above 97% and 78%, respectively, and high-purity Mg and Zn content were accomplished, as evidenced by the recovered products at the reactor outlet and filter containing pure metal. In addition, Mg product exhibited strong oxidation reactivity with air, thus requiring inert atmosphere for the handling of Mg-rich powders to avoid direct exposure to air.

scholarly journals Investigating the In-Flow Characteristics of Multi-Operation Conditions of Cross-Flow Fan in Air Conditioning Systems

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 959
Author(s):  
Weijie Zhang ◽  
Jianping Yuan ◽  
Qiaorui Si ◽  
Yanxia Fu
Keyword(s):  
Pressure Distribution ◽  
Flow Rate ◽  
Total Pressure ◽  
Air Conditioning ◽  
Pressure Pulsation ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Operating Conditions ◽  
Aerodynamic Noise ◽  
Cross Flow Fan

Cross-flow fans are widely used in numerous applications such as low-pressure ventilation, household appliances, laser instruments, and air-conditioning equipment. Cross-flow fans have superior characteristics, including simple structure, small size, stable airflow, high dynamic pressure coefficient, and low noise. In the present study, numerical simulation and experimental research were carried out to study the unique secondary flow and eccentric vortex flow characteristics of the internal flow field in multi-operating conditions. To this end the vorticity and the circumferential pressure distribution in the air duct are obtained based on the performed experiments and the correlation between spectral characteristics of multiple operating conditions and the inflow state is established. The obtained results show that when the area of the airflow passage decreases while the area of the eccentric vortex area gradually increases, then the airflow of the cross-flow fan decreases, the outlet expands, and the flow pattern uniformity reduces. It was found that wakes form in the vicinity of the blade and the tail of the volute tongue, which generate pressure pulsation, and aerodynamic noise. The pressure distribution along the inner circumference shows that the total minimum pressure appears in the eccentric vortex near the volute tongue and the volute returns near the zone. Moreover, it was found that the total pressure near the eccentric vortex is significantly smaller than that of the main flow zone. As the flow rate decreases, the pressure pulsation amplitude of the eccentric vortex region significantly increases, while the static and total pressure pulsation amplitudes are gradually increased. Close to the eccentric vortex on the inner side of the blade in the volute tongue area, total pressure is low, total pressure on the outside of the blade is not affected, and pressure difference between the inner and outer sides is large. When the flow rate of the cross-flow fan is 0.4 Qd, there is no obvious peak at the harmonic frequency of the blade passage frequency. This shows that the aerodynamic noise is caused by the main unstable flow.

Uniquely Designed Solar Tube in a Natural/Forced Mini-Water Heating System

2018 ◽  
Author(s):  
Amanie N. Abdelmessih ◽  
Siddiq S. Mohammed
Keyword(s):  
Solar Energy ◽  
Forced Convection ◽  
Solar Power ◽  
Heating System ◽  
Operating Conditions ◽  
Water Heating ◽  
Solar Water Heating ◽  
Solar Water ◽  
Water Heaters ◽  
Solar Water Heating System

Solar power is a clean source of energy, i.e. it does not generate carbon dioxide or other air pollutants. In 2017, solar power produced only 0.6 percent of the energy used in the United States, according to the Energy Information Administration. Consequently, more solar energy should be implemented, such as in solar water heaters. This research took place in Riverside, Southern California where there is an abundance of solar energy. In house uniquely designed and assembled solar tubes were used in designing a mini solar water heating system. The mini solar water heating system was set to operate under either natural or forced convection. The results of running the system under forced convection then under natural convection conditions are reported and discussed in the article. In addition, comparison of using two different solar water storage systems are reported: the first was water; the second storage medium was a combination of water and gravel. Since water heaters are extensively used for residential purposes, this research mimicked the inefficiencies in residential use and is compared with ideal operating conditions. The performance of the different cases studied is evaluated.

Probabilistic and Numerical Modelling of a Lobed Mixer at Windmilling Conditions

2013 ◽  
Author(s):  
Maxime Lecoq ◽  
Nicholas Grech ◽  
Pavlos K. Zachos ◽  
Vassilios Pachidis
Keyword(s):  
Flow Field ◽  
Response Surface ◽  
Gas Turbine ◽  
Pressure Loss ◽  
Total Pressure ◽  
Engine Performance ◽  
Operating Conditions ◽  
Total Pressure Loss ◽  
Operating Point ◽  
Mixing Losses

Aero-gas turbine engines with a mixed exhaust configuration offer significant benefits to the cycle efficiency relative to separate exhaust systems, such as increase in gross thrust and a reduction in fan pressure ratio required. A number of military and civil engines have a single mixed exhaust system designed to mix out the bypass and core streams. To reduce mixing losses, the two streams are designed to have similar total pressures. In design point whole engine performance solvers, a mixed exhaust is modelled using simple assumptions; momentum balance and a percentage total pressure loss. However at far off-design conditions such as windmilling and altitude relights, the bypass and core streams have very dissimilar total pressures and momentum, with the flow preferring to pass through the bypass duct, increasing drastically the bypass ratio. Mixing of highly dissimilar coaxial streams leads to complex turbulent flow fields for which the simple assumptions and models used in current performance solvers cease to be valid. The effect on simulation results is significant since the nozzle pressure affects critical aspects such as the fan operating point, and therefore the windmilling shaft speeds and air mass flow rates. This paper presents a numerical study on the performance of a lobed mixer under windmilling conditions. An analysis of the flow field is carried out at various total mixer pressure ratios, identifying the onset and nature of recirculation, the flow field characteristics, and the total pressure loss along the mixer as a function of the operating conditions. The data generated from the numerical simulations is used together with a probabilistic approach to generate a response surface in terms of the mass averaged percentage total pressure loss across the mixer, as a function of the engine operating point. This study offers an improved understanding on the complex flows that arise from mixing of highly dissimilar coaxial flows within an aero-gas turbine mixer environment. The total pressure response surface generated using this approach can be used as look-up data for the engine performance solver to include the effects of such turbulent mixing losses.

Sign in / Sign up

Export Citation Format

Share Document