Chemical-looping combustion process: Kinetics and mathematical modeling

Chemical-looping combustion holds significant promise as one of the next generation combustion technology for high-efficiency low-cost carbon capture from fossil fuel power plants. For thorough understanding of the chemical-looping combustion process and its successful implementation in CLC based industrial scale power plants, the development of high-fidelity modeling and simulation tools becomes essential for analysis and evaluation of efficient and cost effective designs. In this paper, multiphase flow simulations of coal-direct chemical-looping combustion process are performed using ANSYS Fluent CFD code. The details of solid-gas two-phase hydrodynamics in the CLC process are investigated by employing the Lagrangian particle-tracking approach called the discrete element method (DEM) for the movement and interaction of solid coal particles moving inside the gaseous medium created due to the combustion of coal particles with an oxidizer. The CFD/DEM simulations show excellent agreement with the experimental results obtained in a laboratory scale fuel reactor in cold flow conditions. More importantly, simulations provide important insights for making changes in fuel reactor configuration design that have resulted in significantly enhanced performance.

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Multiphase CFD Modeling for a Chemical Looping Combustion Process (Fuel Reactor)

Chemical Engineering & Technology ◽

10.1002/ceat.200800341 ◽

2008 ◽

Vol 31 (12) ◽

pp. 1754-1766 ◽

Cited By ~ 44

Author(s):

Z. G. Deng ◽

R. Xiao ◽

B. S. Jin ◽

Q. L. Song ◽

H. Huang

Keyword(s):

Combustion Process ◽

Cfd Modeling ◽

Chemical Looping Combustion ◽

Chemical Looping ◽

Fuel Reactor ◽

Multiphase Cfd

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Chemical-looping combustion — a thermodynamic study

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/09544062jmes790 ◽

2008 ◽

Vol 222 (6) ◽

pp. 1005-1019 ◽

Cited By ~ 23

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.

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Review of Computational Fluid Dynamics Studies on Chemical Looping Combustion

Journal of Energy Resources Technology ◽

10.1115/1.4048680 ◽

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.

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Characterization for Disposal of the Residues Produced by Materials Used as Solid Oxygen Carriers in an Advanced Chemical Looping Combustion Process

Applied Sciences ◽

10.3390/app8101787 ◽

2018 ◽

Vol 8 (10) ◽

pp. 1787

Author(s):

Adriana Carrillo ◽

Carmen Forero

Keyword(s):

Manganese Oxides ◽

Negative Impact ◽

Low Cost ◽

Combustion Process ◽

Chemical Looping Combustion ◽

Chemical Looping ◽

Oxygen Carriers ◽

Additional Energy ◽

General Terms ◽

Solid Oxygen

Chemical looping combustion (CLC) is a technology that is part of the capture and storage of CO2 through the combustion with solid oxygen carriers (OCs). It is considered an energy-efficient alternative to other methods, since it is a technology that inherently separates CO2 and has the advantage of not requiring additional energy for this separation. The key to the performance of CLC systems is the OC material. Low-cost materials, i.e., natural minerals rich in metal oxides (chromite, ilmenite, iron, and manganese oxides) were used in this investigation. These may contain traces of toxic elements, making the carrier residues hazardous. Therefore, the oxidized and reduced-phase residues of six OCs, evaluated in a discontinuous batch fluidized bed reactor (bFB) using methane and hydrogen as the reducing gas, were characterized by several techniques (crushing strength, SEM, XRD, and XRF). The researchers found that, in general terms, the residues present a composition very similar to that reported in the fresh samples, and although they contain traces of Ba, Cu, Cr, Ni or Zn, these compounds do not migrate to the leachate. It was mainly found that, according to the current regulations, none of the residues are classified as toxic, as they do not exceed the permissible limits of metals (100 and 5 mg/L for Ba and Cr, respectively), with 3.5 mg/L the highest value found for Ba. Thus, they would not have a negative impact on the environment when disposed of in a landfill.

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