scholarly journals Oxidation kinetics of YBaCo 4 O 7+ δ and substituted oxygen carriers

2018 ◽  
Vol 5 (6) ◽  
pp. 180150
Author(s):  
Limin Hou ◽  
Qingbo Yu ◽  
Kun Wang ◽  
Qin Qin ◽  
Mengqi Wei ◽  
...  
Keyword(s):  
Oxidation Process ◽  
Solid Phase ◽  
Oxygen Carrier ◽  
Xrd Analysis ◽  
Phase Changes ◽  
Oxygen Absorption ◽  
Oxygen Carriers ◽  
Isothermal Tg ◽  
Primary Particles ◽  
Kinetics Of

In this paper, the relaxation kinetics of the oxidation process of the YBaCo 4 O 7+ δ , Y 0.95 Ti 0.05 BaCo 4 O 7+ δ and Y 0.5 Dy 0.5 BaCo 4 O 7+ δ oxygen carriers is studied with isothermal reaction data. XRD analysis for fresh samples shows that all the samples have YBaCo 4 O 7+ δ structure. Scanning electron microscopy images of samples show that the samples consist of porous agglomerates of primary particles. Isothermal TG experiments are conducted with temperatures of 290°C, 310°C, 330°C and 350°C, respectively. It is found that the Avrami-Eroféev model describes solid-phase changes in the oxygen absorption process adequately. The results show that the distributed activation energies of the oxidation process obtained by the Avrami-Eroféev model are 42.079 kJ mol −1 , 42.944 kJ mol −1 and 41.711 kJ mol −1 for the YBaCo 4 O 7+ δ , Y 0.95 Ti 0.05 BaCo 4 O 7+ δ and Y 0.5 Dy 0.5 BaCo 4 O 7+ δ oxygen carriers, respectively. The kinetic model was obtained to predict the oxygen carrier conversion of oxygen absorption for different time durations. The kinetic parameters obtained here are quite vital when this material is used in reactors.

scholarly journals Study on the thermal kinetics of anthracite oxidation induced by water and associated pyrite

2020 ◽  
Author(s):  
Caiping Wang ◽  
Xiadan Duan ◽  
Zujin Bai ◽  
Yang Xiao ◽  
Jun Deng
Keyword(s):  
Coal Sample ◽  
Spontaneous Combustion ◽  
Oxidation Process ◽  
Great Influence ◽  
Oxygen Absorption ◽  
Heating Rates ◽  
Temperature Oxidation ◽  
Mechanism Model ◽  
Gain Stage ◽  
Kinetics Of

Abstract Pyrite and water in coal have considerable influence on coal spontaneous combustion and threaten the safety of mine production gravely. To reveal the influence mechanism of water and associated pyrite on oxidation kinetics of coal–oxygen composite reaction, the pyrite of 0%, 1%, 2%, 4%, 6% and the moisture of 1%, 5%, 10%, 15% and 20% were mixed with the coal samples to obtain 25 coal samples. Thermogravimetric analysis technology was conducted to explore the changes of mass and characteristic temperatures of coal samples treated with water and associated pyrite during the low–temperature oxidation, and kinetic analysis of the oxidation process was discussed based on multiple heating rates(5 °C/min, 10 °C/min and15 °C/min).The results show that water and associated pyrite had a great influence on coal in oxygen absorption and weight gain stage ( T 3 ~ T 5 ), and there was a proportion range with the largest synergistic oxidation contribution. The apparent activation energy of the coal sample appeared changes, but the mechanism model did not, indicating that water and pyrite could affect the oxidation process of the coal sample externally. When water and associated pyrite exhibit synergistic interaction, there have a range that water was 10~15% and associate pyrite was 2~4% had the largest promotion and contribution to anthracite oxidation. The results have important scientific value and practical guiding significance for the further study on prediction, prevention and control of high sulfur anthracite spontaneous combustion.

Effect of Fuel and Oxygen Carriers on the Hydrodynamics of Fuel Reactor in a Chemical Looping Combustion System

2013 ◽  
Author(s):  
Atal B. Harichandan ◽  
Tariq Shamim
Keyword(s):  
Oxygen Carrier ◽  
Bubble Formation ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Calcium Sulfide ◽  
Oxygen Carriers ◽  
Fuel Reactor ◽  
Gas Interactions ◽  
Kinetics Of ◽  
Good Agreement

The hydrodynamics of fuel reactor in a chemical looping combustion (CLC) system has been analyzed by using a multiphase CFD-based model with solid-gas interactions and chemical reactions. In this paper, the fuel reactors of two CLC systems are numerically simulated independently by using hydrogen with calcium sulfide as oxygen carrier, and methane with nickel as oxygen carrier in similar conditions. Kinetic theory of granular flow has been adopted. Conservation of mass, momentum and species equations, and reaction kinetics of oxygen carriers are used for the numerical calculation. The present results obtained are in good agreement with the experimental and numerical results available in open literature. The bubble hydrodynamics in both the fuel reactors are analyzed. The salient features of bubble formation, rise and burst are prominent in hydrogen-fueled reactor as compared to methane-fueled reactor. The fuel conversion rate is found to be larger in the case of hydrogen-fueled reactor.

Effect of Fuel and Oxygen Carriers on the Hydrodynamics of Fuel Reactor in a Chemical Looping Combustion System

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Atal Bihari Harichandan ◽  
Tariq Shamim
Keyword(s):  
Oxygen Carrier ◽  
Bubble Formation ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Fuel Reactor ◽  
Computational Fluid Dynamics Cfd ◽  
Gas Interactions ◽  
Kinetics Of ◽  
Good Agreement

The hydrodynamics of a fuel reactor in a chemical looping combustion (CLC) system is analyzed by using a multiphase two-dimensional computational fluid dynamics (CFD) model that involves solid–gas interactions and chemical reactions. The study compares the fuel reactors of two CLC systems numerically by using hydrogen with calcium sulfide as an oxygen carrier, and methane with nickel as an oxygen carrier in similar conditions. Kinetic theory of granular flow has been adopted. The model considers the conservation equations of mass, momentum and species, and reaction kinetics of oxygen carriers. The results obtained are in good agreement with the experimental and numerical results available in open literature. The bubble hydrodynamics in both the fuel reactors are analyzed. The salient features of the bubble formation, rise, and burst are more prominent in the hydrogen-fueled reactor as compared to the methane-fueled reactor. The fuel conversion rate is found to be larger for the hydrogen-fueled reactor.

scholarly journals Reduction and oxidation kinetics of NiWO4 as an oxygen carrier for hydrogen storage by a chemical looping process

RSC Advances ◽  
2021 ◽  
Vol 11 (47) ◽  
pp. 29453-29465
Author(s):  
P. E. González-Vargas ◽  
J. M. Salinas-Gutiérrez ◽  
M. J. Meléndez-Zaragoza ◽  
J. C. Pantoja-Espinoza ◽  
A. López-Ortiz ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Oxidation Kinetics ◽  
Oxygen Carrier ◽  
Reaction Scheme ◽  
High Potential ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Storage Density ◽  
Reduction And Oxidation ◽  
Kinetics Of

H2 storage of NiWO4 with a volumetric storage density of 496 g L−1 was studied and evaluated under a chemical looping reaction scheme by TGA. Results confirms the high potential of NiWO4 to current oxygen carriers reported in the literature.

Thermal Analysis of Ca1+xCu3Ti4O12+x Precursor in Nitrogen and Oxygen Environment at 1000 °C

2020 ◽  
Vol 1010 ◽  
pp. 268-273
Author(s):  
Julie Juliewatty Mohamed ◽  
Noruzaman Daud ◽  
Mohamad Johari bin Abu ◽  
Mohd Fariz Ab Rahman ◽  
Siti Roshayu binti Hassan ◽  
...  
Keyword(s):  
Mass Loss ◽  
Room Temperature ◽  
Single Phase ◽  
Xrd Analysis ◽  
Phase Changes ◽  
Oxygen Absorption ◽  
Atmospheric Gases ◽  
Scanning Calorimetry ◽  
Nitrogen Gas ◽  
Ca Ions

The thermal kinetic analyses are prepared on Ca1+xCu3Ti4O12+x powders using simultaneous thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) measurement in a dual atmospheric gases environment. Initially, the nitrogen gas flowed from room temperature to 1000 °C, and then the environment was shifted and hold for 1 hour with oxygen. The result shows that the TGA patterns of the temperature and mass loss are disorderly with x values. The mass loss % patterns slightly decreased with increased additional Ca-based element. The decreased of oxygen absorption as the values of x increased also can be explained by the reduction of single-phase CCTO structure when excess Ca ions. The DSC pattern shows two prominent endothermic peaks and two exothermic peaks that relate to the melting point of the reactant and crystalline phase changes of samples, while the significant endothermic peak at 1000 °C is corresponding to the formation of CCTO compounds as identified by XRD analysis.

scholarly journals The kinetics of solvent-mediated phase transformations

1985 ◽  
Vol 398 (1815) ◽  
pp. 415-428 ◽  
Keyword(s):  
Copper Phthalocyanine ◽  
Solid Phase ◽  
Metastable Phase ◽  
Phase Changes ◽  
Growth Time ◽  
Stable Phase ◽  
Surface Areas ◽  
Mechanistic Insight ◽  
Time Required ◽  
Kinetics Of

A number of mineralogical and synthetic precipitates undergo solid to solid phase changes via a solution phase. A review of the literature reveals a lack of both experimental data and a framework for its interpretation. A model is developed, for the case of a polymorphic phase transformation, which involves the dissolution of the metastable phase and growth of nuclei of the stable phase. The concepts of dissolution and growth time scales have been introduced and it is shown that their sum is the time required for the disappearance of the metastable phase. Mechanistic insight is best obtained by measure­ment of the supersaturation profile rather than conversion data. It is shown that such profiles are dominated by the plateau supersaturation, which is the point at which dissolution and growth are balanced. Its value is determined by the relative surface areas of the phases and their kinetic constants. The model has been successfully used to simulate available kinetic data for the α → β polymorphic transformation in copper phthalocyanine.

Reduction Characteristic of CaSO4-CuO Combined Oxygen Carrier Under CO Atmosphere

2021 ◽  
Vol 72 (3) ◽  
pp. 122-135
Author(s):  
Kang Li ◽  
Min Zheng ◽  
Jingquan Wang ◽  
Jun Wu
Keyword(s):  
Reaction Temperature ◽  
Solid Phase ◽  
Oxygen Carrier ◽  
Reduction Reaction ◽  
Release Time ◽  
Oxygen Carriers ◽  
Main Metal ◽  
High Temperature Reaction ◽  
Caso4 Oxygen Carrier ◽  
The Individual

CaSO4 oxygen carrier is considered to be a potential oxygen carrier (OC) for Chemical Looping Combustion because of its high oxygen capacity and low price. But its reactivity is lower than the main metal oxide oxygen carriers, and it deactivates due to sulfur loss as well as sintering at high reaction temperatures above 920 ℃. To improve the performance of CaSO4-based oxygen carrier, small amounts of CuO particles were mixed mechanistically with CaSO4 particles to use as combined oxygen carrier in this work. The reduction reactions of CaSO4 oxygen carrier, CuO oxygen carrier and CaSO4-CuO combined oxygen carrier under CO atmosphere were investigated. The effects of reaction factors including reaction temperature, the oxygen-carrying ratio of CuO to CaSO4 and mass of oxygen carrier, on the reductions have been investigated in this study. XRD, SEM-EDS, BET and gas analyses were performed to investigate the variations of solid phase, element compositions in solid residual and sulfur release with reaction time. The results show that the addition of CuO increases the reactivity of the CaSO4-based oxygen carrier while also suppressing the release of the gas sulfur. For the individual reduction of CaSO4 by CO, with the increase of CaSO4 mass (500 - 1200 mg), CO2 yield also increases until 1000 mg stops and SO2 released rises remarkably; An increase in the reaction temperature aggravated the SO2 emission. The carbon dioxide generation efficiency also increases with an increase in temperature, but decreases when the temperature exceeds 950 ℃ due to sintering of the oxygen carrier particles; With respect to the reaction of CuO with CO, CO2 yield does not change significantly with increasing temperature, due to the sintering of the CuO oxygen carrier in a high temperature reaction environment;For the combined oxygen carrier: a.As the reduction reaction temperature increases, the reduction reaction performance of the combined oxygen carrier is enhanced within the reaction temperature range of 750~900℃. b. CaO the use of CuO additives not only improves the CO conversion rate, but also inhibits the release of gas sulfide. As the oxygen carrying fraction of CuO increases, SO2 released is reduced and the SO2 release time is delayed. What� more, the solid products after reduction reaction mainly contain CaS, CaO, CuO, Cu2O and CaSO4, and no copper sulfide is detected. c. When the oxygen-carrying ratio of CuO to CaSO4 is increasing from 15% to 20%, CO2 yield increases greatly.

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.

scholarly journals The Potential of Gas Switching Partial Oxidation Using Advanced Oxygen Carriers for Efficient H2 Production with Inherent CO2 Capture

2021 ◽  
Vol 11 (10) ◽  
pp. 4713
Author(s):  
Carlos Arnaiz del Pozo ◽  
Schalk Cloete ◽  
Ángel Jiménez Álvaro ◽  
Felix Donat ◽  
Shahriar Amini
Keyword(s):  
Partial Oxidation ◽  
Co2 Capture ◽  
Oxygen Carrier ◽  
H2 Production ◽  
Advanced Materials ◽  
Oxygen Carriers ◽  
Large Power ◽  
Steam Methane ◽  
Hydrogen Supply ◽  
Energy Penalty

The hydrogen economy has received resurging interest in recent years, as more countries commit to net-zero CO2 emissions around the mid-century. “Blue” hydrogen from natural gas with CO2 capture and storage (CCS) is one promising sustainable hydrogen supply option. Although conventional CO2 capture imposes a large energy penalty, advanced process concepts using the chemical looping principle can produce blue hydrogen at efficiencies even exceeding the conventional steam methane reforming (SMR) process without CCS. One such configuration is gas switching reforming (GSR), which uses a Ni-based oxygen carrier material to catalyze the SMR reaction and efficiently supply the required process heat by combusting an off-gas fuel with integrated CO2 capture. The present study investigates the potential of advanced La-Fe-based oxygen carrier materials to further increase this advantage using a gas switching partial oxidation (GSPOX) process. These materials can overcome the equilibrium limitations facing conventional catalytic SMR and achieve direct hydrogen production using a water-splitting reaction. Results showed that the GSPOX process can achieve mild efficiency improvements relative to GSR in the range of 0.6–4.1%-points, with the upper bound only achievable by large power and H2 co-production plants employing a highly efficient power cycle. These performance gains and the avoidance of toxicity challenges posed by Ni-based oxygen carriers create a solid case for the further development of these advanced materials. If successful, results from this work indicate that GSPOX blue hydrogen plants can outperform an SMR benchmark with conventional CO2 capture by more than 10%-points, both in terms of efficiency and CO2 avoidance.

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