Assessment of CO2 capture by calcium looping (CaL) process in a flexible power plant operation scenario

• Development of dynamic model for the CO2 capture using calcium looping (CaL) process.
• Evaluation of CaL cycle dynamic behavior and model validation vs. experimental data.
• Evaluation of CO2 removal capacity during a ramp, step and sinusoidal input tests.

Among various carbon capture options, calcium looping (CaL) seems to be a promising method to reduce both energy and cost penalties for post-combustion CO2 capture compared to gas–liquid applications. In addition, assessment of dynamic performances of power plants with carbon capture is of great importance in the context of actual energy sector. This paper develops and evaluates, through dynamic modeling, the performances of CaL cycle operating in turbulent and fast fluidization regimes. CaL cycle has two independed circulated fluidized bed (CFB) reactors: the calciner, where CO2 is captured by reacting with CaO and the carbonator, where the CO2 is released and the sorbent is regenerated. Detailed mathematic models for both CaL cycle reactors were developed and simulated in dynamic conditions similar to the power plant cycling. The simulation results, in case of carbonator, were compared with experimental data published in literature and good quality prediction of CaL cycle was observed. In terms of CO2 capture efficiency, the sorbent capacity decreases significant with the number of cycles. The results proved that the height of the dense region decreases with increasing of the superficial velocity of the gas. The most part of the reactions takes place in the dense region; therefore, at smaller superficial gas velocities a higher carbonation degree can be achieved (more than 73%). The CO2 removal rate has been studied using a ramp, step and sinusoidal input tests to highlight the CaL transient response that occur in a real power plant due to load following operation.