Comparison of Chemical-Looping with Oxygen Uncoupling and Chemical-Looping Combustion Technology Reaction Mechanism

2014 ◽  
Vol 955-959 ◽  
pp. 2261-2266
Author(s):  
Xiao Ning Gao ◽  
Hui Min Xue ◽  
Yuan Li ◽  
Xue Feng Yin
Keyword(s):  
New Technologies ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
High Efficient ◽  
Direct Separation ◽  
Fuel Reactor ◽  
Combustion Technology

In order to reduce the emission of CO2and control the global greenhouse effect, the paper introduces and compares two new technologies named chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) that are both high-efficient and clean. Through comparative analysis, CLC has been widely studied because of its direct separation of CO2, reduction loss of the heat, improvement of energy efficiency and avoiding of the generation of fuel type NOxin the combustion process. Besides the current research for metal oxygen carrier, there are some scholars find various non-metal oxygen carriers that have the better performance in CLC. But the study on reactors of CLC is still not mature, especially the solid fuel reactor, which is different from CLOU. In a certain sense, CLOU is an improved technology based CLC, besides the bove advantages, it also can react with coal directly. Many scholars use coal as fuel in the fluidized bed by the technology of CLOU, and the results of them are feasible. So from this perspective, CLOU technology has more broad prospects than CLC in the China.

Review of Computational Fluid Dynamics Studies on Chemical Looping Combustion

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Yali Shao ◽  
Ramesh K. Agarwal ◽  
Xudong Wang ◽  
Baosheng Jin
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Flow Process ◽  
Gas Leakage ◽  
Fuel Reactor ◽  
Energy Penalty

Abstract Chemical looping combustion (CLC) is an attractive technology to achieve inherent CO2 separation with low energy penalty. In CLC, the conventional one-step combustion process is replaced by two successive reactions in two reactors, a fuel reactor (FR) and an air reactor (AR). In addition to experimental techniques, computational fluid dynamics (CFD) is a powerful tool to simulate the flow and reaction characteristics in a CLC system. This review attempts to analyze and summarize the CFD simulations of CLC process. Various numerical approaches for prediction of CLC flow process are first introduced and compared. The simulations of CLC are presented for different types of reactors and fuels, and some key characteristics including flow regimes, combustion process, and gas-solid distributions are described in detail. The full-loop CLC simulations are then presented to reveal the coupling mechanisms of reactors in the whole system such as the gas leakage, solid circulation, redox reactions of the oxygen carrier, fuel conversion, etc. Examples of partial-loop CLC simulation are finally introduced to give a summary of different ways to simplify a CLC system by using appropriate boundary conditions.

scholarly journals Comparison of oxygen carriers for chemical-looping combustion

2006 ◽  
Vol 10 (3) ◽  
pp. 93-107 ◽  
Author(s):  
Marcus Johansson ◽  
Tobias Mattisson ◽  
Anders Lyngfelt
Keyword(s):  
Fossil Fuels ◽  
Oxygen Carrier ◽  
High Reactivity ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Reducing Conditions ◽  
Different Temperatures ◽  
Combustion Technology ◽  
Separation Of Co2

Chemical-looping combustion is a combustion technology with inherent separation of the greenhouse gas CO2. This technique involves combustion of fossil fuels by means of an oxygen carrier which transfers oxygen from the air to the fuel. In this manner a decrease in efficiency is avoided for the energy demanding separation of CO2 from the rest of the flue gases. Results from fifty oxygen carriers based on iron-, manganese- and nickel oxides on different inert materials are compared. The particles were prepared using freeze granulation, sintered at different temperatures and sieved to a size 125-180 mm. To simulate the environment the particles would be exposed to in a chemical-looping combustor, reactivity tests under alternating oxidizing and reducing conditions were performed in a laboratory fluidized bed-reactor of quartz. Reduction was performed in 50% CH4/50% H2O while the oxidation was carried out in 5% O2 in nitrogen. In general nickel particles are the most reactive, followed by manganese. Iron particles are harder but have a lower reactivity. An increase in sintering temperatures normally leads to an increase in strength and decrease in reactivity. Several particles investigated display a combination of high reactivity and strength as well as good fluidization behavior, and are feasible for use as oxygen carriers in chemical-looping combustion.

The Performance Research on Reaction of Fe2O3/Al2O3 Oxygen Carrier and CO in Chemical-Looping Combustion Process

2012 ◽  
Vol 550-553 ◽  
pp. 974-978
Author(s):  
Wen Yan Li ◽  
Xing Lei Liu ◽  
Qiu Luan Chen ◽  
Feng Ming Chu
Keyword(s):  
Oxygen Carrier ◽  
Combustion Process ◽  
Kinetic Mechanism ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Novel Technology ◽  
Mechanism Function ◽  
Tg And Dtg ◽  
Performance Research

Chemical-looping combustion (CLC) is a novel technology, which has inherent property of separating the greenhouse gas CO2, which uses oxygen carriers to transfer oxygen for combustion from air to fuel. The reactivity of Fe2O3/Al2O3 oxygen carrier was assessed by measuring their ability to oxidize CO. The kinetics and mechanism of oxygen carrier have been studied by TG and DTG techniques. The kinetic mechanism function of the reaction between Fe2O3/Al2O3 and CO has been built using the Coats-Redfern equation.

Computational Fluid Dynamics Modeling of Chemical Looping Combustion Process with Calcium Sulphate Oxygen Carrier

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Baosheng Jin ◽  
Rui Xiao ◽  
Zhongyi Deng ◽  
Qilei Song
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Combustion Products ◽  
Calcium Sulphate ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Dynamics Modeling ◽  
Fuel Reactor

To concentrate CO2 in combustion processes by efficient and energy-saving ways is a first and very important step for its sequestration. Chemical looping combustion (CLC) could easily achieve this goal. A chemical-looping combustion system consists of a fuel reactor and an air reactor. Two reactors in the form of interconnected fluidized beds are used in the process: (1) a fuel reactor where the oxygen carrier is reduced by reaction with the fuel, and (2) an air reactor where the reduced oxygen carrier from the fuel reactor is oxidized with air. The outlet gas from the fuel reactor consists of CO2 and H2O, while the outlet gas stream from the air reactor contains only N2 and some unused O2. The water in combustion products can be easily removed by condensation and pure carbon dioxide is obtained without any loss of energy for separation.Until now, there is little literature about mathematical modeling of chemical-looping combustion using the computational fluid dynamics (CFD) approach. In this work, the reaction kinetic model of the fuel reactor (CaSO4+ H2) is developed by means of the commercial code FLUENT and the effects of partial pressure of H2 (concentration of H2) on chemical looping combustion performance are also studied. The results show that the concentration of H2 could enhance the CLC performance.

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.

The Preparation Methods of Fe2O3/Al2O3 Oxygen Carriers and their Chemical Looping Combustion Performance

2013 ◽  
Vol 724-725 ◽  
pp. 1145-1149 ◽  
Author(s):  
Zi Song Liu ◽  
Yong Gang Wei ◽  
Kong Zhai Li ◽  
Hua Wang ◽  
Xing Zhu ◽  
...  
Keyword(s):  
High Selectivity ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Preparation Methods ◽  
Air Atmosphere ◽  
Infrared Gas Analyzer ◽  
Structure And Activity

60wt%Fe2O3/Al2O3oxygen carriers were prepared by different methods and characterized by means of XRD, H2-TPR, infrared gas analyzer. The effects of preparation methods on the structure and activity of Fe2O3/Al2O3oxygen carriers for chemical looping combustion of methane were also investigated. The factors on the selectivity of CO2in the chemical looping combustion process at different reaction temperatures were discussed. Methane can be quickly converted to CO2and H2O with high selectivity at 850°C for 15 min. After redox cycling in alternant methane/air atmosphere for 30 times, the formation of CO2was enhanced, indicating higher activity of oxygen carrier after the redox experiment.

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.

Study and Improvement of the Regeneration of Metallic Oxides Used as Oxygen Carriers for a New Combustion Process

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Sebastien Roux ◽  
Ammar Bensakhria ◽  
Gerard Antonini
Keyword(s):  
Oxygen Carrier ◽  
Combustion Process ◽  
Reactive Oxygen ◽  
Chemical Looping Combustion ◽  
Regeneration Ability ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Air Oxidation ◽  
Metallic Oxide ◽  
Metallic Oxides

A new combustion process called chemical-looping combustion, has been suggested as an energetically efficient method for separation and capture of the carbon dioxide, generated by the combustion of fossil's fuels. This process consists of a reversible combustion, based on successive fuel oxidation via the reduction of metallic oxide followed by its regeneration by air oxidation. The generated products are: the reduced oxygen carrier, which is regenerated in a second reactor by air and recycled, and a flue gas, mainly composed of CO2 and H2O, which could be separated by condensation.In chemical-looping combustion process, it is important that the metallic oxide, used as an oxygen carrier, has a high reactivity with the fuel and good regeneration ability. It should have also good mechanical characteristics, in order to avoid its attrition and agglomeration during the successive cyclic reactions.In this work, the reactivity study of various oxygen carriers was carried out, during ten successive oxidation and reduction cycles, using a thermal gravimetrical analysis apparatus. From the results obtained, two types of oxygen carriers were identified: very reactive oxygen carriers, with a decreasing of their reactivity during the successive cycles of reduction and oxidation, and oxygen carriers with low and constant reactivity during the successive cycles.In order to improve the capacity of regeneration of the reactive oxygen carrier, several mixtures were prepared by adding stable and non-reactive metallic oxide, which acts as binder or doping agent by the mechanical properties of the mixed oxygen carrier improvement.The results obtained showed that, for all mixtures prepared and tested, the addition of binders to the reactive metallic oxides improve their regeneration ability. The best results, concerning the reactivity and the regeneration performances, were obtained with Fe2O3 mixed with CaO, TiO2 or MgO, followed by NiO mixed with CaO or TiO2 and finally CuO mixed with TiO2 or MgO.

Optimizing the Fuel Reactor for Chemical Looping Combustion

2003 ◽  
Author(s):  
Juan Ada´nez ◽  
Francisco Garci´a-Labiano ◽  
Luis F. de Diego ◽  
Ainhoa Plata ◽  
Javier Celaya ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Oxygen Carrier ◽  
Bubble Diameter ◽  
Operating Conditions ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Solid Contact ◽  
Fuel Reactor ◽  
Contact Efficiency

A mathematical model for a bubbling fluidized bed has been developed to optimize the performance of the fuel reactor in chemical looping combustion systems. This model considers both the hydrodynamic of the fluidized bed (dense bed and freeboard) and the kinetics of the oxygen carrier reduction. Although the model is valid for any of the possible oxygen carriers and fuels, the present work has been focused in the use of a carrier, CuO-SiO2, and CH4 as fuel. The shrinking core model has been used to define the particle behavior during their reduction. The simulation of the fuel reactor under different operating conditions was carried out to set the operating conditions and optimize the process. The effect of different design or operating variables as the bed height, the oxygen carrier/fuel ratio, and the gas throughput was analyzed. Finally, a sensitivity analysis to the solid reactivity, the bubble diameter, and to the gas/solid contact efficiency in the freeboard was done. At vigorous fluidization, solid present in the freeboard can strongly contribute to the gas conversion in the fuel reactor. However, the gas/solid contact efficiency in this zone must be determined for each particular case.

Simulation of a New Chemical-Looping Combustion Process without Sulfur Evolution Based on Ca-Based Oxygen Carrier

2014 ◽  
Vol 12 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Hongjing Tian ◽  
Xiude Hu ◽  
Jing Chang ◽  
Mingdong Han ◽  
Guanglin Sun ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Operating Regime ◽  
Steam Gasification ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Combustion System ◽  
Reactor Temperature

Abstract Calcium sulfate (CaSO4) is a promising oxygen carrier for chemical-looping combustion system. The release of sulfurous gas in the circulating of Ca-based oxygen carrier is a crucial problem. In this paper, it is found that the released amount of sulfurous gas is greatly affected by the partial pressure of reductive gas. If the partial pressure of the mixed reductive gases, composed of H2 and CO, maintains higher than 40 kPa, the sulfurous gas can be completely eliminated even at the reacting temperature higher than 1,000°C. Therefore, a new chemical-looping combustion system based on CaSO4 and NiO oxygen carrier, without any sulfur evolution, is simulated using Aspen Plus software. In the system, the syngas is generated from the steam gasification of coal and reacts with CaSO4 and NiO consecutively. The sulfur release occurred in the circulating of Ca-based oxygen carriers can be prevented because the concentrations of CO and H2 keep higher than 45% in the presence of Ca-based oxygen carriers. The suitable operating regime, in which auto-thermally operating of the system, zero-sulfur release and easy sequestration of CO2 from the flue gas are realized, is proposed in this paper. The effects of fuel reactor temperature, air reactor temperature and the recycle rate of oxygen carrier on the released heat from the system and the concentration of CO2 and H2O are also studied in the paper.

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