A computational fluid dynamics design of a carbon dioxide sorption circulating fluidized bed

Abstract

A kinetic theory based hydrodynamic model with experimentally determined sorption rates for reaction of CO 2 with K 2 CO 3 solid sorbent is used to design a compact circulating fluidized bed sorption-regeneration system for CO 2 removal from flue gases. Because of high solids fluxes, the sorber does not require internal or external cooling. The output is verified by computing the granular temperatures, particle viscosities, dispersion, and mass transfer coefficients. These properties agree with reported measurement values except the radial dispersion coefficients, which are much higher due to the larger bed diameter. With the solid sorbent prepared according to published information, the CO 2 removal percentage at the riser top is 69.16%. To improve the CO 2 removal, an effort is needed to develop a better sorbent or to simply lower the inlet gas velocity to operate in a denser mode, leading to a larger system. Also, the effect of temperature rise on the removal efficiency is investigated.

Carbon dioxide capture using solid sorbents in a fluidized bed with reduced pressure regeneration in a downer

“…Due to the high-circulation rates, the temperature of the solid sorbent rises only at 4 C. This is similar to the study of Chalermsinsuwan et al 14 This small rise in the solid and gas temperatures keeps the sorption capacity of the solid sorbent relatively constant. The heat of reaction captured in the solid sorbent from the sorber-riser is recovered in the regeneratordowner.…”

“…The energy requirement topic is a main issue for this article. Chalermsinsuwan et al 14 showed that the system performance decreases with increasing operating temperature difference between sorber-riser and regenerator-downer. Additionally, the smaller the difference of temperature, the smaller the minimum required power for regeneration process.…”

“…The study of Chalermsinsuwan B et al 14 showed that circulating fluidized beds (CFB) can be used effectively for CO2 sorption from the flue gases generated by conventional coal fired power plants. However, the solid flow patterns in the sorber section for the CFB showed some fluctuation of the gas and solid flows which allow some of the untreated flue gases to channel through the sorber section.…”

“…[14][15][16][17][18][19][20] In this study, the alkali-based sodium carbonate (Na 2 CO 3 ) is chosen as the solid sorbent because its CO 2 sorption capacity is high and its required vacuum pressure for regeneration at low temperature is reasonable. 17 Additionally, the sodium carbonate (Na 2 CO 3 ) is nontoxic, low cost and fairly easy to obtain.…”

The generality of the standard 2D TFM approach in predicting bubbling fluidized bed hydrodynamics

“…Despite numerous uncertainties still remaining in terms of hydrodynamic modelling, significant research efforts have recently been invested in extending the KTGF to reactive flows [11][12][13][14][15]. Incorporation of chemical reactions significantly increases the complexity of the system due to the close coupling between hydrodynamics and chemical kinetics [16] and, due to this close coupling, predictions of overall reactor performance are highly dependent on accurate simulation of the underlying hydrodynamics.…”