Performance of a Cu-Fe-based oxygen carrier combined with a Ni-based oxygen carrier in a chemical-looping combustion process based on fixed-bed reactors

2018 ◽  
Vol 8 (3) ◽  
pp. 542-556 ◽  
Author(s):  
Qiang Tian ◽  
Lixin Che ◽  
Bin Ding ◽  
Qianwei Wang ◽  
Qingquan Su
Keyword(s):  
Oxygen Carrier ◽  
Combustion Process ◽  
Fixed Bed ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Fixed Bed Reactors

Chemical-looping combustion — a thermodynamic study

2008 ◽  
Vol 222 (6) ◽  
pp. 1005-1019 ◽  
Author(s):  
N R McGlashan
Keyword(s):  
Heat Exchange ◽  
Redox Reactions ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Reduction Process ◽  
Equilibrium Temperature ◽  
Working Fluid ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Ic Engine

The poor performance of internal combustion (IC) engines can be attributed to the departure from equilibrium in the combustion process. This departure is expressed numerically, as the difference between the working fluid's temperature and an ideal ‘combustion temperature’, calculated using a simple expression. It is shown that for combustion of hydrocarbons to be performed reversibly in a single reaction, impractically high working fluid temperatures are required — typically at least 3500 K. Chemical-looping combustion (CLC) is an alternative to traditional, single-stage combustion that performs the oxidation of fuels using two reactions, in separate vessels: the oxidizer and reducer. An additional species circulates between the oxidizer and reducer carrying oxygen atoms. Careful selection of this oxygen carrier can reduce the equilibrium temperature of the two redox reactions to below current metallurgical limits. Consequently, using CLC it is theoretically possible to approach a reversible IC engine without resorting to impractical temperatures. CLC also lends itself to carbon capture, as at no point is N2 from the air allowed to mix with the CO2 produced in the reduction process and therefore a post-combustion scrubbing plant is not required. Two thermodynamic criteria for selecting the oxygen carrier are established: the equilibrium temperature of both redox reactions should lie below present metallurgical limits. Equally, both reactions must be sufficiently hot to ensure that their reaction velocity is high. The key parameter determining the two reaction temperatures is the change in standard state entropy for each reaction. An analysis is conducted for an irreversible CLC system using two Rankine cycles to produce shaft work, giving an overall efficiency of 86.5 per cent. The analysis allows for irreversibilites in turbine, boiler, and condensers, but assumes reactions take place at equilibrium. However, using Rankine cycles in a CLC system is considered impractical because of the need for high-temperature, indirect heat exchange. An alternative arrangement, avoiding indirect heat exchange, is discussed briefly.

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.

Chemical-looping combustion of methane with CaSO4 oxygen carrier in a fixed bed reactor

2008 ◽  
Vol 49 (11) ◽  
pp. 3178-3187 ◽  
Author(s):  
Qilei Song ◽  
Rui Xiao ◽  
Zhongyi Deng ◽  
Huiyan Zhang ◽  
Laihong Shen ◽  
...  
Keyword(s):  
Oxygen Carrier ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Caso4 Oxygen Carrier

Producing Hydrogen and Power Using Chemical Looping Combustion and Water-Gas Shift

2009 ◽  
Vol 132 (3) ◽  
Author(s):  
Niall R. McGlashan ◽  
Peter R. N. Childs ◽  
Andrew L. Heyes ◽  
Andrew J. Marquis
Keyword(s):  
Gas Turbines ◽  
Oxygen Carrier ◽  
Combustion Process ◽  
Water Gas Shift ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Operating Pressure ◽  
Overall Efficiency ◽  
Water Gas ◽  
Steam Cycle

A cycle capable of generating both hydrogen and power with “inherent” carbon capture is proposed and evaluated. The cycle uses chemical looping combustion to perform the primary energy release from a hydrocarbon, producing an exhaust of CO. This CO is mixed with steam and converted to H2 and CO2 using the water-gas shift reaction (WGSR). Chemical looping uses two reactions with a recirculating oxygen carrier to oxidize hydrocarbons. The resulting oxidation and reduction stages are preformed in separate reactors—the oxidizer and reducer, respectively, and this partitioning facilitates CO2 capture. In addition, by careful selection of the oxygen carrier, the equilibrium temperature of both redox reactions can be reduced to values below the current industry standard metallurgical limit for gas turbines. This means that the irreversibility associated with the combustion process can be reduced significantly, leading to a system of enhanced overall efficiency. The choice of oxygen carrier also affects the ratio of CO versus CO2 in the reducer’s flue gas, with some metal oxide reduction reactions generating almost pure CO. This last feature is desirable if the maximum H2 production is to be achieved using the WGSR reaction. Process flow diagrams of one possible embodiment using a zinc based oxygen carrier are presented. To generate power, the chemical looping system is operated as part of a gas turbine cycle, combined with a bottoming steam cycle to maximize efficiency. The WGSR supplies heat to the bottoming steam cycle, and also helps to raise the steam necessary to complete the reaction. A mass and energy balance of the chemical looping system, the WGSR reactor, steam bottoming cycle, and balance of plant is presented and discussed. The results of this analysis show that the overall efficiency of the complete cycle is dependent on the operating pressure in the oxidizer, and under optimum conditions exceeds 75%.

Nanostructure Oxygen Carrier Used in Chemical Looping Combustion Process—A Review

2016 ◽  
Vol 22 (4) ◽  
pp. 717-721
Author(s):  
Mansing M Badadare ◽  
Naina M Adbale ◽  
R. B Khomane ◽  
Ganesh R Kale
Keyword(s):  
Oxygen Carrier ◽  
Combustion Process ◽  
Chemical Looping Combustion ◽  
Chemical Looping

Study of a Cu-Based Oxygen Carrier Based on a Chemical Looping Combustion Process

2015 ◽  
Vol 29 (6) ◽  
pp. 3933-3943 ◽  
Author(s):  
Xiaoming Zheng ◽  
Qingquan Su ◽  
Wanliang Mi
Keyword(s):  
Oxygen Carrier ◽  
Combustion Process ◽  
Chemical Looping Combustion ◽  
Chemical Looping
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