Kinetic Investigations of a Two-Step Thermochemical Water-Splitting Cycle Using Mixed Iron Oxides Fixed on Ceramic Substrates

2008 ◽  
Author(s):  
Martina Neises ◽  
Martin Roeb ◽  
Martin Schmu¨cker ◽  
Christian Sattler ◽  
Robert Pitz-Paal
Keyword(s):  
Activation Energy ◽  
Hydrogen Production ◽  
Metal Oxide ◽  
Water Splitting ◽  
Iron Oxides ◽  
Reaction Rate ◽  
Solar Furnace ◽  
Solar Irradiation ◽  
Test Rig ◽  
Kinetics Of

A two-step thermochemical cycle for solar hydrogen production using mixed iron oxides as the metal oxide redox system has been investigated. A reactor concept has been developed in which the metal oxide is fixed on multi-channelled honeycomb ceramic supports capable of adsorbing solar irradiation. In the solar furnace of DLR in Cologne coated honeycomb structures were tested in a solar receiver-reactor with respect to their water splitting capability and their long term stability. The concept of this new reactor design has proven feasible and constant hydrogen production during repeated cycles has been shown. For a further optimization of the process and in order to gain reliable performance predictions more information about the process especially concerning the kinetics of the oxidation and the reduction step are essential. To examine the kinetics of the water splitting and the regeneration step a test rig has been built up on a laboratory scale. In this test rig small coated honeycombs are heated by an electric furnace. The honeycomb is placed inside a tube reactor and can be flushed with water vapour or with an inert gas. A homogeneous temperature within the sample is reached and testing conditions are reproducible. Through analysis of the product gas the hydrogen production is monitored and a reaction rate describing the hydrogen production rate per gram ferrite can be formulated. Using this test set-up, SiC honeycombs coated with a zinc-ferrite have been tested. The influences of the water splitting temperature and the water concentration on the kinetics of the water splitting step have been investigated. A mathematical approach for the reaction rate was formulated and the activation energy was calculated from the experimental data. An activation energy of 110 kJ/mole was found.

Solar Hydrogen Production by a Two-Step Cycle Based on Mixed Iron Oxides

Solar Energy ◽  
2005 ◽  
Author(s):  
Martin Roeb ◽  
Christian Sattler ◽  
Ruth Klu¨ser ◽  
Nathalie Monnerie ◽  
Lamark de Oliveira ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Solar Energy ◽  
Metal Oxide ◽  
Iron Oxides ◽  
Operating Conditions ◽  
Solar Furnace ◽  
Solar Irradiation ◽  
Redox Systems ◽  
Solar Hydrogen ◽  
Solar Hydrogen Production

A very promising method for the conversion and storage of solar energy into a fuel is the dissociation of water to oxygen and hydrogen, carried out via a two-step process using metal oxide redox systems such as mixed iron oxides, coated upon multi-channeled honeycomb ceramic supports capable of absorbing solar irradiation, in a configuration similar to that encountered in automobile exhaust catalytic converters. With this configuration, the whole process can be carried out in a single solar energy converter, the process temperature can be significantly lowered compared to other thermo-chemical cycles and the re-combination of oxygen and hydrogen is prevented by fixing the oxygen in the metal oxide. For the realization of the integrated concept, research work proceeded in three parallel directions: synthesis of active redox systems, manufacture of ceramic honeycomb supports and manufacture, testing and optimization of operating conditions of a thermochemical solar receiver-reactor. The receiver-reactor has been developed and installed in the solar furnace in Cologne, Germany. It was proven that solar hydrogen production is feasible by this process demonstrating that multi cycling of the process was possible in principle.

Solar Hydrogen Production by a Two-Step Cycle Based on Mixed Iron Oxides

2005 ◽  
Vol 128 (2) ◽  
pp. 125-133 ◽  
Author(s):  
Martin Roeb ◽  
Christian Sattler ◽  
Ruth Klüser ◽  
Nathalie Monnerie ◽  
Lamark de Oliveira ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Solar Energy ◽  
Metal Oxide ◽  
Iron Oxides ◽  
Operating Conditions ◽  
Solar Furnace ◽  
Solar Irradiation ◽  
Redox Systems ◽  
Solar Hydrogen ◽  
Solar Hydrogen Production

A promising method for the conversion and storage of solar energy into hydrogen is the dissociation of water into oxygen and hydrogen, carried out via a two-step process using metal oxide redox systems such as mixed iron oxides, coated upon multi-channeled honeycomb ceramic supports capable of absorbing solar irradiation, in a configuration similar to that encountered in automobile exhaust catalytic converters. With this configuration, the whole process can be carried out in a single solar energy converter, the process temperature can be significantly lowered compared to other thermo-chemical cycles and the recombination of oxygen and hydrogen is prevented by fixing the oxygen in the metal oxide. For the realization of the integrated concept, research work proceeded in three parallel directions: synthesis of active redox systems, manufacture of ceramic honeycomb supports and manufacture, testing and optimization of operating conditions of a thermochemical solar receiver-reactor. The receiver-reactor has been developed and installed in the solar furnace in Cologne, Germany. It was proven that solar hydrogen production is feasible by this process demonstrating that multicycling of the process was possible in principle.

scholarly journals Photocatalyst Z-scheme system composed of a linear conjugated polymer and BiVO4 for overall water splitting under visible light

2020 ◽  
Vol 8 (32) ◽  
pp. 16283-16290 ◽  
Author(s):  
Yang Bai ◽  
Keita Nakagawa ◽  
Alexander J. Cowan ◽  
Catherine M. Aitchison ◽  
Yuichi Yamaguchi ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Metal Oxide ◽  
Visible Light ◽  
Water Splitting ◽  
Conjugated Polymer ◽  
Overall Water Splitting

A Z-scheme of a linear conjugated polymer photocatalyst and a metal oxide is able to facilitate overall water splitting without non-scalable sacrificial reagents showing potential for sustainable hydrogen production.

scholarly journals Analysis of the Kinetics of Swimming Pool Water Reaction in Analytical Device Reproducing Its Circulation on a Small Scale

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4820 ◽  
Author(s):  
Wojciech Kaczmarek ◽  
Jarosław Panasiuk ◽  
Szymon Borys ◽  
Aneta Pobudkowska ◽  
Mikołaj Majsterek
Keyword(s):  
Activation Energy ◽  
Water Quality ◽  
Rate Constant ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Small Scale ◽  
Pool Water ◽  
Swimming Pool Water ◽  
Kinetics Of ◽  
Analytical Device

The most common cause of diseases in swimming pools is the lack of sanitary control of water quality; water may contain microbiological and chemical contaminants. Among the people most at risk of infection are children, pregnant women, and immunocompromised people. The origin of the problem is a need to develop a system that can predict the formation of chlorine water disinfection by-products, such as trihalomethanes (THMs). THMs are volatile organic compounds from the group of alkyl halides, carcinogenic, mutagenic, teratogenic, and bioaccumulating. Long-term exposure, even to low concentrations of THM in water and air, may result in damage to the liver, kidneys, thyroid gland, or nervous system. This article focuses on analysis of the kinetics of swimming pool water reaction in analytical device reproducing its circulation on a small scale. The designed and constructed analytical device is based on the SIMATIC S7-1200 PLC driver of SIEMENS Company. The HMI KPT panel of SIEMENS Company enables monitoring the process and control individual elements of device. Value of the reaction rate constant of free chlorine decomposition gives us qualitative information about water quality, it is also strictly connected to the kinetics of the reaction. Based on the experiment results, the value of reaction rate constant was determined as a linear change of the natural logarithm of free chlorine concentration over time. The experimental value of activation energy based on the directional coefficient is equal to 76.0 [kJ×mol−1]. These results indicate that changing water temperature does not cause any changes in the reaction rate, while it still affects the value of the reaction rate constant. Using the analytical device, it is possible to constantly monitor the values of reaction rate constant and activation energy, which can be used to develop a new way to assess pool water quality.

N-Doped CsTaWO6 as a New Photocatalyst for Hydrogen Production from Water Splitting Under Solar Irradiation

2010 ◽  
Vol 21 (1) ◽  
pp. 126-132 ◽  
Author(s):  
Aniruddh Mukherji ◽  
Roland Marschall ◽  
Akshat Tanksale ◽  
Chenghua Sun ◽  
Sean C. Smith ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Solar Irradiation

Investigations of the Regeneration Step of a Thermochemical Cycle Using Mixed Iron Oxides Coated on SiSiC Substrates

2011 ◽  
Author(s):  
Martina Neises ◽  
Heike Simon ◽  
Martin Roeb ◽  
Martin Schmu¨cker ◽  
Christian Sattler ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Hydrogen Production ◽  
Laboratory Test ◽  
Iron Oxides ◽  
Small Scale ◽  
Thermochemical Cycle ◽  
Test Rig ◽  
Regeneration Time ◽  
Eds Analysis ◽  
Parametric Studies

A two-step thermochemical cycle for hydrogen production using mixed iron oxides coated on silicon carbide substrates has been investigated. The water-splitting step proceeds at temperatures between 800 and 1000 °C while for the regeneration step temperatures around 1200 °C are needed. A deactivation of the material resulting in a decrease of the hydrogen production within the first couple of cycles was observed in preceding tests. For detailed investigations of the system composed of the redox-material and the substrate small scale samples were tested in a laboratory test-rig. For identification of material changes the samples were investigated via XRD and SEM-EDS analysis. The analysis revealed the reasons for the deactivation of the redox-material. Through parametric studies the influence of the regeneration parameters, namely regeneration temperature and time on the hydrogen production was analysed. A model for the regeneration step was developed describing the performance of the regeneration step as a function of temperature and time and additionally as a function of total regeneration time, i.e. the cumulated time the sample has been regenerated.

Hydrogen production via a two-step water splitting thermochemical cycle based on metal oxide – A review

2020 ◽  
Vol 267 ◽  
pp. 114860 ◽  
Author(s):  
Yanpeng Mao ◽  
Yibo Gao ◽  
Wei Dong ◽  
Han Wu ◽  
Zhanlong Song ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Metal Oxide ◽  
Water Splitting ◽  
Thermochemical Cycle

New Solar Water-Splitting Reactor With Ferrite Particles in an Internally Circulating Fluidized Bed

2007 ◽  
Author(s):  
Nobuyuki Gokon ◽  
Shingo Takahashi ◽  
Hiroki Yamamoto ◽  
Tatsuya Kodama
Keyword(s):  
Metal Oxide ◽  
Fluidized Bed ◽  
Water Splitting ◽  
Circulating Fluidized Bed ◽  
Thermal Reduction ◽  
Solar Irradiation ◽  
Solar Water Splitting ◽  
Oxide Particles ◽  
Efficient Heat Transfer ◽  
Reactor Operating

The thermal reduction of metal oxides as part of a thermochemical two-step water splitting cycle requires the development of a high temperature solar reactor operating at 1000–1500°C. Direct solar energy absorption by metal-oxide particles provides efficient heat transfer directly to the reaction site. This paper describes experimental results of a windowed thermochemical water-splitting reactor using an internally circulating fluidized bed of the reacting metal-oxide particles under direct solar irradiation. The reactor has a transparent quartz window on the top as aperture. The concentrated solar radiation passes downward through the window and directly heats the internally circulating fluidized bed of metal-oxide particles. Therefore, this reactor needs to be combined with a solar tower or beam down optics. NiFe2O4/m-ZrO2 (Ni-ferrite supported on zirconia) particles is loaded as the working redox material in the laboratory scale reactors, and thermally reduced by concentrated Xe-beam irradiation. In a separate step, the thermally-reduced sample is oxidized back to Ni-ferrite with steam at 1000°C. As the results, the conversion of ferrite reached about 44% of maximum value in the reactor by 1kW of incident solar power. The effects of preheating temperature and particle size of NiFe2O4/m-ZrO2 were tested for thermal reduction of internally circulating fluidized bed in this paper.

Simulation of a Solar Receiver-Reactor for Hydrogen Production

2009 ◽  
Author(s):  
Martina Neises ◽  
Felix Goehring ◽  
Martin Roeb ◽  
Christian Sattler ◽  
Robert Pitz-Paal
Keyword(s):  
Hydrogen Production ◽  
Solar Radiation ◽  
Thermal Behavior ◽  
Water Splitting ◽  
Solar Furnace ◽  
Small Scale ◽  
Mathematical Tool ◽  
Thermochemical Cycle ◽  
Set Up ◽  
Solar Receiver

The transient thermal behavior of two solar receiver-reactors for hydrogen production has been modeled using Modelica/Dymola. The simulated reactors are dedicated to carry out the same chemical reactions but represent two different development stages of the project HYDROSOL and two different orders of magnitude concerning reactor size and hydrogen production capacity. The process itself is a two step thermochemical cycle, which uses mixed iron-oxides as a redox-system. The iron-oxide is coated on a ceramic substrate, which is placed inside the receiver-reactor and serves on the one hand as an absorber for solar radiation and on the other hand as the reaction zone for the chemical reaction. The process consists of a water splitting step in which hydrogen is produced and a regeneration step during which the used redox-material is being reduced. The reactor is operated between these two reaction conditions in regular intervals with alternating temperature levels of about 800 °C for the water splitting step and 1200 °C for the regeneration step. Because of this highly dynamic process and because of fluctuating solar radiation during the day, a mathematical tool was necessary to model the transient behavior of the reactor for theoretical studies. Two models have been developed for two existing receiver-reactors. One model has been set up to simulate the behavior of a small scale test reactor, which has been built and tested at the solar furnace of DLR in Cologne. Results are very promising and show that the model is able to reflect the thermal behavior of the reactor. Another model has been developed for a 100 kWth pilot reactor which was set up at the Plataforma Solar de Almeri´a in Spain. This model is based on the first model but special geometrical features had to be adapted. With this model temperatures and hydrogen production rates could be predicted.

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