Scrubbing of CO₂ Greenhouse Gases, Accompanied by Precipitation in a Continuous Bubble-Column Scrubber

Abstract

A continuous bubble-column scrubber that absorbs carbon dioxide (CO2) gas using an alkaline solution under a pH-stat condition was used to explore the effects of the pH of the solution, gas concentration, gas-superficial velocity, and liquid-flow rate on the absorption rate and volumetric mass-transfer coefficient of CO2. When the scrubbing factor was evaluated, this scrubber outperformed other scrubbers. Correlations of local volumetric mass-transfer coefficients with process variables are presented here and the gas−liquid interfacial area and individual mass-transfer coefficient are discussed to provide insight into the mass-transfer mechanism. Investigation of the liquid-side mass transfer coefficient revealed that the k L/[OH−]0.5 value was a constant, thus demonstrating that the system obeyed second-order kinetics. Evidence also shows that liquid-side resistances are within the range of 27%−99%, indicating that gas-side mass-transfer resistance cannot be neglected in some cases. This implies that the absorption mechanism is flexible and can be shifted by adjusting the process parameters.

Conversion of calcium sulphide to calcium carbonate during the process of recovery of elemental sulphur from gypsum waste

“…The dissolution of gaseous CO 2 in solution is generally the first rate-limiting step in direct carbonation reactions [27], but it can be enhanced by increasing the CO 2 flow rate [28] when working at atmospheric pressure and thereby ensuring that excess carbonate ions are present relative to calcium ions. However, a further increase of the flow rate to more than 29.33 ℓ CO 2 /min/kg CaS r had little effect on the overall reaction time (Table 5 and Figure 6).…”

A Study on CO2 Absorption in Bubble Column Using DEEA/EEA Mixed Solvent

“…In order to further determine the mass-transfer coefficient, it was assumed that two-film model was used to describe CO2 mass transfer (Chen et al, 2008). Thus, the overall mass-transfer coefficient can be expressed as follows:…”

“…The results can provide references for bubble column design. The bubble column features simple structure, easy operation, cost efficiency and excellent scrubbing factor as compared with other scrubbers (Chen et al, 2008;Lin et al, 2003;Sauer and Hempel, 1987;Aroonwilas et al, 1999), without mechanical heat production. Thus, recovery of CO2 using bubble columns can reduce costs and save energy.…”

Absorption of Carbon Dioxide in a Bubble-Column Scrubber

“…In addition to these methods, the absorption of carbon dioxide in an alkaline solution with crystallization has also been adopted to explore the removal of carbon dioxide from waste gas (Chen et al, 2008). This approach, with the production of carbonate by means of reactive crystallization, has been found to be effective.…”

“…Due to this, they found packed bed with structured packing (Aroonwilas & Tontiwachwuthiku, 1997) gives a higher overall mass-transfer coefficient as compared with other scrubbers. On the other hand, Chen et al (2008) found that the performance of scrubber could be estimated by using scrubbing factor, a definition of removal of 1 mole CO 2 gas per mole of absorbent and per liter of scrubber. In this manner, a bubble-column scrubber is the first choice.…”