Development and testing of an interconnected multiphase CFD-model for chemical looping combustion

CFD Modelling of the Fuel Reactor of a Chemical Loping Combustion Plant to Be Used with Biomethane

To realize a carbon negative power production technology, it is interesting the option of coupling a Chemical Loping Combustor to a gas turbine. The development of this technology foreseen in the project GTCLC-NEG has some technical barriers, the most important of which is the operation of the chemical looping combustor at high temperature and high pressure conditions. To overcome these limits CFD modeling can be performed to optimize the behavior of the combustor and its design process. This work models the FUEL reactor of a chemical looping combustion plant working in batch mode and based on the reactor available at the Instituto de Carboquimica in Zaragoza, Spain. It is used an oxygen carrier mainly based on 60% mass Fe2O3 and 40% mass Al2O3. Biomethane is fed to the bottom of the fluidized bed with different velocities and mass flows and the composition of the gases at the outlet of the fuel reactor is measured. The results show that it is possible to model a 2 min duration reduction cycle by running the model for a time comprised between a minimum of 4 h and a maximum of 2 days of simulation. Another important result is the modeling of the chemical reactions happening in the reactor. Kinetics is modelled based on Activation energy (66 kJ/mol) and Pre-exponential factor (4.34 × 101 m3n mol−n s−1). The simple kinetic scheme gives reasonable first approximations and can be used to determine the duration of the reaction, the composition of the exhaust gases and the biofuel conversion.

Numerical Investigation of Solid-Fueled Chemical Looping Combustion Process Utilizing Char for Carbon Capture

The in-depth understanding of the gas–solid flow and reaction behaviors, and their coupling characteristics during the chemical looping combustion (CLC) process has the guiding significance for the operation and optimization of a chemical looping combustor. A three-dimensional numerical model is applied to investigate the char-fueled CLC characteristics in a fuel reactor for efficient CO2 separation and capture. Simulations are carried out in a bubbling fluidized bed fuel reactor with a height of 2.0 m and a diameter of 0.22 m. The initial bed height is 1.1 m, and hence the height–diameter ratio of the slumped bed is five. The oxygen carrier is prepared with 14 wt% of CuO on 86 wt% of inert Al2O3. In the process of mathematical modeling, a Eulerian-Eulerian two-fluid model is adopted for both of the gas and solid phases. Gas turbulence is modeled on the basis of a k–ε turbulent model. The reaction kinetics parameters are addressed based upon previous experimental investigations from literature. During the simulation, the gas–solid flow patterns, composition distributions, and reaction characteristics are obtained. Moreover, the effects of solids inventory and fluidizing number on the reaction performance are elucidated in-depth. The results have shown that the reaction rates have close relationship with the flow patterns and the distributions of gas concentrations. Compared to the steam-char gasification over sand, the application of char-fueled CLC can effectively promote the conversion of gasification products. In addition, higher CO2 concentration at the outlet can be achieved by increasing the initial solids inventory or decreasing the fluidizing number. Some calculated values are verified by the previous data, indicating that the current three-dimensional models are reasonable to study the process mechanism of char-fueled CLC.

Uniform-Design-Based Optimization for Fuel Reactor of Chemical Looping Combustion

The thermo-chemical performance of fuel reactor (FR) for chemical looping combustion (CLC) changes with operating parameters. It is essential to optimize these operating variables to achieve the best reactor performance. Based on well-verified computational fluid dynamics (CFD) simulation, uniform design method is employed to study the influence of totally n operating variables each with m levels. With respect to the FR experiments by Son and Kim (2006)(in which fuel is pure methane, and oxygen carrier is the mixture of NiO and Fe2O3 supported by bentonite), the uniform design method has been adopted to optimize the yield of CH4 to CO2. Optimum operating condition (NiO percentage in the activated oxygen carrier of 100 %, reaction temperature of 1123 K, particle diameter of 100 μm, inlet gas velocity of 0.0125 m/s, and solid inventory in FR of 0.51 kg) is obtained, and the dependence of CO2 yield on five operating variables is approximated by the second-order polynomial model based on the uniform design method. The most critical parameter is identified as reaction temperature.

Multi-scale study of hydrodynamics in an interconnected fluidized bed for the chemical looping combustion process

The variation range of bubble diameter in the FR is narrow compared to that in the AR.