scholarly journals Solar-Driven Thermochemical Water-Splitting by Cerium Oxide: Determination of Operational Conditions in a Directly Irradiated Fixed Bed Reactor

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2451 ◽  
Author(s):  
Lucía Arribas ◽  
José González-Aguilar ◽  
Manuel Romero
Keyword(s):  
Water Splitting ◽  
Cerium Oxide ◽  
Radiation Power ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Solar Simulator ◽  
Operational Conditions ◽  
Concentrated Solar Energy ◽  
Production Of Hydrogen ◽  
Temperature Levels

Concentrated solar energy can be transformed into electricity, heat or even solar fuels, such as hydrogen, via thermochemical routes with high exergetic efficiency. In this work, a specific methodology and experimental setup are described, developed to assess the production of hydrogen by water splitting making use of commercial cerium oxide, ceria (CeO2), in a solarized reactor. A fixed bed reactor, directly irradiated by a 7 kWe high flux solar simulator (HFSS) was used. Released H2 and sample temperature levels were continuously monitored. Three tests were carried out consisting of three consecutive redox cycles each, with irradiances in the range of 1017–2034 kWm−2. It was necessary to achieve a compromise between sample temperatures (higher temperatures lead to higher reduction rates) and sample stability, since absorbed radiation can degrade a sample at lower temperature (1280–1480 °C) than in a conventional infrared oven (T > 2000 °C). Irradiating the surface of the sample with an irradiance of 2034 kWm−2 (270 W of total radiation power) during 9.5 min eventually degraded the sample, resulting in a conversion into stoichiometrically reduced oxide (Ce2O3) of 11%. A similar conversion was achieved (9.7%) after 2 min of irradiation at 270 W (100% of radiation), but without irreversibly damaging the sample.

An Anaerobic Fixed Bed Reactor with a Porous Ceramic Carrier

1989 ◽  
Vol 21 (4-5) ◽  
pp. 77-86 ◽  
Author(s):  
Mitsuo Kawase ◽  
Tadashi Nomura ◽  
Tsuyoshi Majima
Keyword(s):  
Loading Rate ◽  
Unit Area ◽  
Porous Ceramic ◽  
Fixed Bed ◽  
Anaerobic Treatment ◽  
Fixed Bed Reactor ◽  
Operational Conditions ◽  
Treatment Performance ◽  
Fixed Bed Reactors ◽  
Highly Loaded

To date, a large number of studies on anaerobic fixed bed reactors have been reported, but there have been few studies on the application of this technology to thermophilic anaerobic treatment. One of the reasons for the small number of applications is the difficulty of attaching thermophilic anaerobic organisms to carriers. The study reported in this paper was conducted to examine the thermophilic treatment performance of an anaerobic fixed bed reactor containing a porous ceramic carrier (‘microbe immobilized ceramic', MIC) developed for the immobilization of anaerobic organisms. When boiled soybean wastewater (55,000 mg/l COD) was treated anaerobically at a high temperature (54°C) in a reactor where 31% of the volume was filled with the MIC carrier, it was found that highly loaded operation with up to 65 kg COD/m3/d was possible. The COD load per unit area of carrier surface under these operational conditions reached 0.397 kg COD/m3/d, and the performance of the reactor was excellent. Stable anaerobic treatment was achieved when the COD loading rate fluctuated from 26 to 51 kg COD/m3/d.

SER Process Variable Evaluation for the Production of Hydrogen using Calcined Dolomite

2011 ◽  
Vol 14 (2) ◽  
pp. 121-126
Author(s):  
A. Lopez-Ortiz ◽  
V. Collins-Martinez ◽  
D. P. Harrison
Keyword(s):  
Fixed Bed ◽  
Catalyst Particle ◽  
Process Variable ◽  
Fixed Bed Reactor ◽  
Particle Sizes ◽  
Gas Composition ◽  
Co2 Diffusion ◽  
Production Of Hydrogen ◽  
Kinetic Effects ◽  
Co2 Absorbent

Reaction performance of the sorption enhanced reforming (SER) process for the production of hydrogen was studied using commercial dolomite as inexpensive solid CO2 absorbent. The combined reforming, shift, and CO2 separation reactions were studied using a laboratory-scale fixed-bed reactor as a function of temperature, feed gas composition, dolomite type, and dolomite and catalyst particle sizes. Reactor was loaded with a mixture of calcined dolomite (≈ 23g) and a commercial reforming catalyst (NiO/Al2O3, ≈ 10g). Temperature was varied from 550 to 650°C at 15 atm. Feed gas composition was varied from 6 to 20% CH4/balance N2 and steam, with a feed H2O/CH4 ratio = 4. Two sources of dolomite were used; Rockwell and Stonelite. Particle sizes of dolomite and catalyst were 75>dp>150 μm and 300>dp>425 μm, respectively and were inversely varied. Results show that at 550°C Ca(OH)2 formation is possible, thus reducing the available CaO for carbonation, negatively affecting the performance of the SER system, while 650°C reached the SER thermodynamic equilibrium (TE). The use of dolomite approached the TE of the feed gas compositions studied, disregarding of its source. Kinetic effects observed in the tests suggest that small dolomite and large catalyst particles favor the decrease of CO2 diffusion effects.

Effect of Mo and Ce Additives on Redox Behavior for Hydrogen Storage and Release of Iron Oxide Mediums

2012 ◽  
Vol 554-556 ◽  
pp. 616-619
Author(s):  
Young Ho Kim ◽  
Eun Jee Kang ◽  
Su Gyung Lee ◽  
Hyo Sub Kim ◽  
Chu Sik Park
Keyword(s):  
Iron Oxide ◽  
Hydrogen Storage ◽  
Water Splitting ◽  
Atmospheric Pressure ◽  
Hydrogen Reduction ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Redox Behavior ◽  
Good Material ◽  
Reduction And Oxidation

The hydrogen reduction and water-splitting oxidation for hydrogen storage and release on the iron oxide mediums with Ce, Mo or Ce-Mo additives were carried out using a fixed bed reactor at atmospheric pressure. A sole Ce additive was an outstanding material for the improvement of the reactivity in the reduction and oxidation of iron oxide medium, even though the medium with Ce was easily deactivated during repeated cyclic reactions due to sintering. A sole Mo additive was a good material for the improvement for the durability. In the mediums with the Ce-Mo additives, therefore, the degree of deactivation and the reactivity of the mediums were gradually decreased with the increase of the amount of Mo. Among the iron oxide mediums with Ce-Mo additives, a FeCeMo-5 medium exhibited the good durability while the maintaining the considerable reactivity during the cyclic reactions.

Production of Hydrogen and Syngas via Steam Gasification of Glycerol in a Fixed-Bed Reactor

2008 ◽  
Vol 49 (1-2) ◽  
pp. 59-67 ◽  
Author(s):  
T. Valliyappan ◽  
D. Ferdous ◽  
N. N. Bakhshi ◽  
A. K. Dalai
Keyword(s):  
Fixed Bed ◽  
Steam Gasification ◽  
Fixed Bed Reactor ◽  
Production Of Hydrogen

Field application of a planted fixed bed reactor (PFR) for support media and rhizosphere investigation using undisturbed samples from full-scale constructed wetlands

2015 ◽  
Vol 72 (4) ◽  
pp. 553-560 ◽  
Author(s):  
A. B. Barreto ◽  
G. R. Vasconcellos ◽  
M. von Sperling ◽  
P. Kuschk ◽  
U. Kappelmeyer ◽  
...  
Keyword(s):  
Constructed Wetlands ◽  
Mobile Device ◽  
Fixed Bed ◽  
Field Application ◽  
Full Scale ◽  
Fixed Bed Reactor ◽  
Environmental Research ◽  
Operational Conditions ◽  
Undisturbed Samples ◽  
Real Scale

This study presents a novel method for investigations on undisturbed samples from full-scale horizontal subsurface-flow constructed wetlands (HSSFCW). The planted fixed bed reactor (PFR), developed at the Helmholtz Center for Environmental Research (UFZ), is a universal test unit for planted soil filters that reproduces the operational conditions of a constructed wetland (CW) system in laboratory scale. The present research proposes modifications on the PFR original configuration in order to allow its operation in field conditions. A mobile device to obtain undisturbed samples from real-scale HSSFCW was also developed. The experimental setting is presented with two possible operational configurations. The first allows the removal and replacement of undisturbed samples in the CW bed for laboratory investigations, guaranteeing sample integrity with a mobile device. The second allows the continuous operation of the PFR and undisturbed samples as a fraction of the support media, reproducing the same environmental conditions outside the real-scale system. Investigations on the hydrodynamics of the adapted PFR were carried out with saline tracer tests, validating the proposed adaptation. Six adapted PFR units were installed next to full-scale HSSFCW beds and fed with interstitial liquid pumped from two regions of planted and unplanted support media. Fourteen points were monitored along the system, covering carbon fractions, nitrogen and sulfate. The results indicate the method as a promising tool for investigations on CW support media, rhizosphere and open space for studies on CW modeling, respirometry, kinetic parameters, microbial communities, redox potential and plant influence on HSSFCW.

The Optimization of an Ammonia Synthesis Reactor Using Genetic Algorithm

2009 ◽  
Vol 6 (1) ◽  
Author(s):  
Mohammad Taghi Sadeghi ◽  
Azam Kavianiboroujeni
Keyword(s):  
Genetic Algorithm ◽  
Ammonia Synthesis ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Ammonia Production ◽  
Dimensional Model ◽  
Reactor Performance ◽  
One Dimensional ◽  
Operational Conditions ◽  
Quench Temperature

An industrial ammonia synthesis reactor was studied in order to optimize its operational conditions by means of increasing overall ammonia production. A heterogeneous, one-dimensional model and a two-dimensional rigorous model were utilized to evaluate the process behavior. The simulation results of the two models were compared with data from an industrial ammonia plant. The one-dimensional model was found to be adequate for optimization purposes. Applying the Genetic Algorithm (GA) as a powerful method for complex problems, the model was employed to optimize the reactor performance in varying its quench flows. The optimal temperature profile along the fixed bed reactor was studied by changing independent variables including the quench temperature and the quench flow rates. Optimization results show that the optimum quench temperature is about 615°K and that the optimum quench flows can enhance ammonia production rate by 3.3%.

scholarly journals Prediction of the fixed-bed reactor behavior for biotransformation with parallel enzyme deactivation using dispersion model: A case study on hydrogen peroxide decomposition by commercial catalase

2019 ◽  
Vol 21 (4) ◽  
pp. 106-115
Author(s):  
Ireneusz Grubecki ◽  
Katarzyna Kazimierska-Drobny
Keyword(s):  
Hydrogen Peroxide ◽  
Dispersion Model ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Transfer Model ◽  
Hydrogen Peroxide Decomposition ◽  
Economic Point ◽  
Operational Conditions ◽  
Enzyme Deactivation ◽  
Peroxide Decomposition

Abstract The problems of process costs and pollution of residual waters in the textile industry require increasing attention due to the new ecological regulations and also those resulting from an economic point of view. Hence, the behavior of non-isothermal fixed-bed reactor applied for hydrogen peroxide decomposition by immobilized Terminox Ultra catalase attached onto the outer surface of glass beads was studied to determine the operational conditions at which hydrogen peroxide decomposition is most effectively. A dispersion model for bioreactor applied in this work, and verified experimentally, took into account the coupled mass and heat balances as well as the rate equation for parallel enzyme deactivation. The effect of feed temperature, feed flow rate, feed hydrogen peroxide concentration, and diffusional resistances were analysed. In the calculations the global effectiveness factor based on the external mass-transfer model developed previously was employed to properly predict the real bioreactor behavior.

scholarly journals Encapsulated catalase from Serratia genus for H2O2 decomposition in food applications

2018 ◽  
Vol 20 (4) ◽  
pp. 39-43 ◽  
Author(s):  
Katarzyna Czyzewska ◽  
Anna Trusek
Keyword(s):  
High Activity ◽  
Fixed Bed ◽  
Industrial Applications ◽  
Fixed Bed Reactor ◽  
Reactor Performance ◽  
Operational Conditions ◽  
H2o2 Decomposition ◽  
Wide Range ◽  
Immobilized Catalase ◽  
Food Applications

Abstract The recombinant catalase isolated from a psychrotolerant microorganism belonging to Serratia genus exhibits a high activity in a wide range of pH. Due to a great catalytic potential in operational conditions, it can be used in various industrial applications whereby it acts as a hydrogen peroxide scavenger. To reduce the cost of biocatalyst the enzyme encapsulation into a hydrogel structure was proposed. The obtained results showed a high activity of encapsulated catalase in acidic conditions (pH in range 4.4 - 6.6) and at low temperatures (6-15°C). Moreover, immobilized catalase exhibited a high stability in natural media, especially in milk. Its activity during peroxide decomposition in milk, the possibility of re-using, as well as the fixed bed reactor performance confirmed wide application possibilities. High values of enzyme and substrate concentrations led to the beads burst due to rapid oxygen diffusion from the capsules, thus they are limited.

Steam Gasification of Biochar Derived from Fast Pyrolysis for Hydrogen-Rich Gas Production

2013 ◽  
Vol 830 ◽  
pp. 477-480 ◽  
Author(s):  
Wei Qing Zeng ◽  
Ling Jun Zhu ◽  
Qi Wang
Keyword(s):  
Carbon Number ◽  
Fast Pyrolysis ◽  
Fixed Bed ◽  
Gas Production ◽  
Steam Gasification ◽  
Fixed Bed Reactor ◽  
Hydrogen Yield ◽  
Low Carbon ◽  
Production Of Hydrogen ◽  
Pyrolysis Of Biomass

Steam gasification of biochar from fast pyrolysis of biomass was conducted in a fixed bed reactor. The experiments were carried out at temperature of 700, 750, 800 °C with steam flow rate of 0.1 g/min and reaction time of 3 h. The gas products mainly included H2, CO, CO2and some hydrocarbons with low carbon number. The results showed that the conversion of biochar at 700, 750, 800 °C was 68, 78, 96 wt%, respectively, and high gasification temperature favored the production of hydrogen-rich gases. The hydrogen yield increased with temperature rising and reached the maximum of 35.70 mol/kg with a hydrogen concentration of 74 V% at 800 °C.

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