Swing Adsorption Reactor Cluster (SARC) in Post Combustion CO2 Capture: Multistage Fluidization Effect on Heat Transfer and Reactor Performance

1. Introduction

The SARC concept is an adsorption-based technology that aims at minimizing the energy penalty of post combustion CO₂ capture. It consists of a cluster of multistage fluidized bed reactors running simultaneously and alternating sorbent carbonation and regeneration steps to ensure steady state processing of a flue gas stream. Heat is transferred from carbonation to regeneration using a heat pump that can work very efficiently if the temperature difference between the two stages is minimized by applying a partial vacuum in the regeneration step.

A multistage fluidized bed reactor configuration was proposed for the SARC reactor to simultaneously achieve high heat transfer and maximize CO₂ uptake by the sorbent [1]. Heat transfer tubing, containing the heat pump working fluid, transfers heat between the reactors in the cluster. Competitive CO₂ energy penalty could be achieved using the SARC concept applied to a coal-fired power plant .[2]

2. Methods and results

The multistage fluidized bed reactor results in a low solid back mixing, helping achieving a better performance in terms of CO₂ capture as compared to single stage fluidized bed [1]. A multistage fluidized bed reactor with 10 cm ID was therefore designed and being constructed, with different internal/mesh dividing the reactor in four separate stages. Additionally, the reactor will be embedded with heat transfer surfaces in each stage, wherein heat pump working fluid will be used for heating and cooling the sorbent. The performance of Polyethyleneimine (PEI) sorbent in terms of CO₂ working capacity will be studied in this multistage reactor with different internals segregating each stage. Moreover, the effect of multistage fluidized bed on heat transfer rate at various stages will be evaluated and compared.

The results will indicate the gain in CO₂ uptake during carbonation step by using multistage fluidized bed because of the reduction in solid back mixing. Further, the optimal type of partition between the four reactor stages will be identified. Partitions should have large enough openings to allow individual particles to pass through (to avoid blockage), but the openings should still be small enough to prevent large-scale back mixing flow patterns from developing. Finally, the effect of multistage fluidized bed on heat transfer rate at each stage will set a basis for the demonstration of the complete SARC cycle.

References

1. Zaabout, A., et al., Thermodynamic assessment of the swing adsorption reactor cluster (SARC) concept for post-combustion CO₂ capture. International Journal of Greenhouse Gas Control, 2017. 60: p. 74-92.
2. Cloete, S., et al., The effect of sorbent regeneration enthalpy on the performance of the novel Swing Adsorption Reactor Cluster (SARC) for post-combustion CO₂ capture. Chemical Engineering Journal, 2018.