Parametric behavior of a CO2 capture process: CFD simulation of solid-sorbent CO2 absorption in a riser reactor

The National Energy Technology Laboratory as well as other institutions are developing a variety of technology concepts as alternatives to liquid-amine based absorption processes for post-combustion CO2 capture from large sources such as utility power generation facilities. At low temperature, many of these advanced dry processes are based upon sorbents composed of supported polyamines. In the dry-sorbent process, CO2 from flue gas is absorbed in one reactor, followed by separation of the carbonated particles from the de-carbonated flue gas and in a second reactor the sorbent is regenerated, creating a concentrated stream of pure CO2 for sequestration. In this work, the adsorber performance is simulated using multiphase computational fluid dynamics with chemistry and heat transfer. The three-dimension geometry is based on the lower mixing section of a riser from a recently operated CO2 capture test unit. An eight point test matrix was used to explore the behavior and performance of the riser adsorber with respect to solids circulation rate, gas flow rate and heat removal. It is shown that CO2 adsorption increases with an increase in the solids flow, decreases for an increase in the gas flow. The reactor performance can be summarized as a function of the molar sorbent to CO2 ratio entering the reactor with an R2 value of 0.9985.