scholarly journals An inverse problem in estimating simultaneously the non-linear reaction rates for a fixed-bed reactor

2015 ◽  
Vol 39 (8) ◽  
pp. 2217-2233
Author(s):  
Cheng-Hung Huang ◽  
Bo-Yi Li
Keyword(s):  
Inverse Problem ◽  
Fixed Bed ◽  
Reaction Rates ◽  
Fixed Bed Reactor ◽  
Linear Reaction ◽  
Non Linear

Modeling of Low-Temperature Reduction of Metal Oxide in Hydrogen Treatment System for Severe Accidents in Nuclear Power Plants

2020 ◽  
Author(s):  
Kotaro Nakamura ◽  
Masashi Tanabe ◽  
Satoru Abe ◽  
Takashi Mawatari ◽  
Takao Nakagaki
Keyword(s):  
Water Vapor ◽  
Metal Oxide ◽  
Nuclear Power ◽  
Elevated Temperatures ◽  
Fixed Bed ◽  
Reaction Rates ◽  
Numerical Calculations ◽  
Treatment System ◽  
Fixed Bed Reactor ◽  
Hydrogen Treatment

Abstract At the Fukushima Daiichi nuclear power plant, zirconium in the fuel rod cladding reacted with water vapor at elevated temperatures due to a loss of cooling water, resulting in the production of a large amount of hydrogen. This hydrogen leaked from the reactor vessel and accumulated in the top of reactor building, eventually leading to an explosion. A hydrogen treatment system that re-oxidizes hydrogen to water vapor is one of the effective methods to prevent such an explosion. A prominent re-oxidation method is via a fixed bed reactor packed with metal oxide pellets. The advantages of this method are its relatively fast oxidation rate without external oxygen/air injection. In this study, experiments and complementary numerical calculations were performed on the hydrogen re-oxidation reaction by metal oxides. The oxidation of hydrogen by copper oxide is modeled by 5 interacting, elementary reactions consisting of 6 chemical species. Experiments were performed using two packed bed set-ups, with measurement of inlet/outlet gas composition and pre/post-analysis of solid composition used to determine constants of the individual reaction rates for numerical calculations. From these reaction constants, the temporal behavior of the outlet gas was predicted.

scholarly journals Condensation By-Products in Wet Peroxide Oxidation: Fouling or Catalytic Promotion? Part II: Activity, Nature and Stability

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 518 ◽  
Author(s):  
Asunción Quintanilla ◽  
Jose L. Diaz de Tuesta ◽  
Cristina Figueruelo ◽  
Macarena Munoz ◽  
Jose A. Casas
Keyword(s):  
Catalyst Deactivation ◽  
Fixed Bed ◽  
Reaction Rates ◽  
Fixed Bed Reactor ◽  
Intrinsic Activity ◽  
Peroxide Oxidation ◽  
Air Oxidation ◽  
Carbonaceous Deposits ◽  
Wet Peroxide Oxidation ◽  
By Products

The deposition of condensation by-products onto the catalyst surface upon wet peroxide and wet air oxidation processes has usually been associated with catalyst deactivation. However, in Part I of this paper, it was demonstrated that these carbonaceous deposits actually act as catalytic promoters in the oxygen-assisted wet peroxide oxidation (WPO-O2) of phenol. Herein, the intrinsic activity, nature and stability of these species have been investigated. To achieve this goal, an up-flow fixed bed reactor packed with porous Al2O3 spheres was used to facilitate the deposition of the condensation by-products formed in the liquid phase. It was demonstrated that the condensation by-products catalyzed the decomposition of H2O2 and a higher amount of these species leads to a higher degree of oxidation degree The reaction rates, conversion values and intermediates’ distribution were analyzed. The characterization of the carbonaceous deposits on the Al2O3 spheres showed a significant amount of condensation by-products (~6 wt.%) after 650 h of time on stream. They are of aromatic nature and present oxygen functional groups consisting of quinones, phenols, aldehydes, carboxylics and ketones. The initial phenol concentration and H2O2 dose were found to be crucial variables for the generation and consumption of such species, respectively.

Detoxification and recycling of wastewater by solar-catalytic treatment

1997 ◽  
Vol 35 (4) ◽  
pp. 149-156 ◽  
Author(s):  
H. Freudenhammer ◽  
D. Bahnemann ◽  
L. Bousselmi ◽  
S.-U. Geissen ◽  
A. Ghrabi ◽  
...  
Keyword(s):  
Fixed Bed ◽  
Textile Wastewater ◽  
Reaction Rates ◽  
Fixed Bed Reactor ◽  
Design Parameters ◽  
Joint Research ◽  
Technical Application ◽  
Great Opportunity ◽  
Joint Research Project ◽  
Catalytic Treatment

An introduction to a joint research project is given which deals with the technical application of solar photocatalysis for wastewater detoxification. A non-concentrating thin-film fixed-bed reactor (TFFBR) is used to study applications and areas where a solar-catalytic treatment or recycling of wastewater is possible. This reactor excels by its low cost and an easy-to-build construction using molecular oxygen in air as the oxidising agent. The design parameters of the reactor as well as the process itself have been determined from the reaction kinetics of a model substance, the hydrodynamics and the mass transfer. The treatment of different real wastewaters was successfully carried out, and biologically pre-treated textile wastewater maximum solar degradation rate was about 3 g COD h−1 m−2. A comparison of reaction rates with artifical and solar illumination shows the necessity of outdoor experiments. Due to the reaction rates observed, photocatalysis is suitable as the final stage of purification of biologically or physically pretreated wastewater and will offer a great opportunity for sunrich areas.

scholarly journals Performance of Alternative Methane Reforms Based on Experimental Kinetic Evaluation and Simulation in a Fixed Bed Reactor

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1479
Author(s):  
Augusto Knoelchemann ◽  
Deivson C. S. Sales ◽  
Marcos A. M. Silva ◽  
Cesar A. M. Abreu
Keyword(s):  
Comparative Evaluation ◽  
Carbon Deposition ◽  
Catalyst Deactivation ◽  
Fixed Bed ◽  
Reaction Rates ◽  
Fixed Bed Reactor ◽  
Methane Reforming ◽  
Kinetic Evaluation ◽  
Alternative Processes ◽  
Al2o3 Catalyst

A comparative evaluation of alternative methane reforming processes as an option to steam reforming was performed by carrying out simulations of operations in a fixed bed reactor with a Ni (4.8 wt.%/γ-Al2O3) catalyst at 1023 K under 1.0 bar. Methane reforms, including processing with carbon dioxide (DRM, CH4/CO2), autothermal reform (ATRM, CH4/H2O/O2), and combined reform (CRM, CH4/CO2/H2O/O2) had their operations predicted based on experimental data developed to represent their kinetic behavior, formalized with mechanisms and parametric quantifications. The performance of fixed bed reactor operations for methane conversions occurred with different reaction rates in the three alternative processes, and comparatively the orders of magnitude were 102, 10−1, and 10−4 in CRM, ATRM, and DRM, respectively. According to each process, the methane conversions were oriented towards the predominant productions of hydrogen or carbon monoxide, indicating the kinetic selectivities of H2, 86.1% and CO, 59.2% in CRM and DRM, respectively. Considering the possibility of catalyst deactivation by carbon deposition, its predicted yields are low due to the slow stages of its production and due to its simultaneous consumption through interactions with O2, CO2, and H2O, reflecting favorably in additional productions of H2 and CO.

Electrochemical Promotion Catalytic Oxidation of NO over Mn/TiO2 and Mn-Fe Catalyst

2011 ◽  
Vol 219-220 ◽  
pp. 1472-1476 ◽  
Author(s):  
Jing Hao Song ◽  
Xiao Long Tang ◽  
Hong Hong Yi ◽  
Ping Ning ◽  
Kai Li ◽  
...  
Keyword(s):  
Catalytic Oxidation ◽  
Fixed Bed ◽  
Input Voltage ◽  
Electrochemical Promotion ◽  
Reaction Rates ◽  
Electrochemical Reactor ◽  
No Oxidation ◽  
Fixed Bed Reactor ◽  
Fe Catalyst ◽  
Oxidation Of No

A new type electrochemical reactor was designed for electrochemical promotion catalytic oxidation of NO, which was a flat-plate fixed-bed reactor. The experimental results showed that the process of NO catalytic oxidation could be promoted though this electrochemical reactor with Mn/TiO2and Mn-Fe, which were two kinds of selected catalysts for NO oxidation. Approximately 70% NO could be converted to NO2at 50 °C when the input voltage of electrochemical reactor was 0.5v. Moreover, the reaction rates can be adjusted with the input voltage varying.

A Study of High-Pressure CO2 Recycling Using Pinewood Char Gasification

2013 ◽  
Author(s):  
Indraneel Sircar ◽  
Anup Sane ◽  
Jay Gore
Keyword(s):  
Experimental Data ◽  
Mass Loss ◽  
Large Scale ◽  
High Pressures ◽  
Fixed Bed ◽  
High Sensitivity ◽  
Reaction Rates ◽  
Fixed Bed Reactor ◽  
Loss Data ◽  
High Pressure Co2

Measurements of the reaction rates at high-pressures for gasification of low-ash pinewood char with CO2 are presented. A fixed-bed reactor operated at 1140–1260 K and 1–10 atm was utilized in the present study. Product gas sampling and gas chromatograph measurements enabled tracking of the gasification progress and mass loss data. The mass loss data are interpreted using the volumetric and non-reactive core models. Activation energy, collision frequency and reaction order are reported for each model. The experimental data show high sensitivity to temperature. The data also show an increase of the apparent gasification rates with higher CO2 pressures. Comparison of computed char conversion profiles and experimental data are discussed in the context of mass transport and effects on the gasification rates. The findings from this study have applications to gasification modeling and design of large-scale gasification systems.

scholarly journals Coal Chemical-Looping with Oxygen Uncoupling (CLOU) Using a Cu-Based Oxygen Carrier Derived from Natural Minerals

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1453 ◽  
Author(s):  
Ping Wang ◽  
Bret Howard ◽  
Nicholas Means ◽  
Dushyant Shekhawat ◽  
David Berry
Keyword(s):  
Solid Fuel ◽  
Low Cost ◽  
Oxygen Carrier ◽  
Fixed Bed ◽  
Xrd Analysis ◽  
Reaction Rates ◽  
Fixed Bed Reactor ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Redox Cycles

Chemical-looping with oxygen uncoupling (CLOU) is considered a promising technology to burn solid fuels with improved CO2 capture and has the potential to improve fuel conversion and reaction rates. Cu-based oxygen carriers (Cu-OC) are often used in solid fuel CLOU. This study focused on investigating Cu-OC derived from a natural mineral for solid fuel CLOU because of their potentially lower cost compared to synthetic OCs. Reactivity and recyclability of a natural ore-derived Cu-OC on coal char (Powder River Basin sub-bituminous coal) were studied at 900 °C in Ar and air using TGA-QMS and fixed-bed reactor-QMS for five cycles. Cu-OC was prepared by simply heating chalcopyrite in air. Chalcopyrite is one of the principle copper sulfide ores and one of the primary ores for copper. The prepared Cu-OC had primarily CuO and CuFe2O4 (CuOFe2O3) as active compounds based on XRD analysis and an oxygen capacity 3.3% from oxygen uncoupling. The carbon conversion efficiency Xc was 0.94 for reduction at a ratio of Cu-OC to char ϕ = 75 and the product gas was primarily CO2 with trace O2. The reactivities and the rates were similar for five redox cycles. These results indicate that the natural ore-derived material with low cost has potential as a competitive oxygen carrier in solid fuel CLOU based on its reactivity in this study.

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