Hydrodynamic simulation of fuel-reactor in chemical looping combustion process

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 Simulation of a 10 kW Gas-Fueled Chemical Looping Combustion Unit

Chemical looping combustion is one novel technology for controlling CO2 emission with a low energy cost. Due to a lack of understanding of the detailed and micro behavior of the CLC process, especially for a three dimensional structure, numerical simulations are carried out in this work. The configuration is built according to the experimental unit and gaseous fuel is used in this work. A two-fluid model considering heterogeneous reactions is established, and the flow behaviour and reaction characteristics are obtained. The temperature in the air reactor increases with height owing to the exothermic reaction of the xidation of the oxygen carrier, while the temperature in the fuel reactor decreases with height due to the endothermic reaction. The oxidation level of the oxygen carrier is obtained by simulation, which is hard for measurement, and the difference between the inlet and outlet is 0.065. The influences of the operating temperature and injection rate of fuel are presented to understand the performance of the system. The highest fuel conversion rate reaches 0.92 under high operating temperature. The numerical results are helpful for acquiring insight on the flow and reactive behaviour of CLC reactors.

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.