String of discs contactor apparatus for CO2 absorption

https://doi.org/10.1016/j.cesx.2019.100032

“The CO₂ absorption rate of unloaded amine solutions was measured using the string of discs contactor illustrated in Fig. 2. The apparatus, previously explained by Gondal et al. (2015b), is placed in a heating chamber and consist of a glass column with 43 discs. Each disc has a diameter of 1.5 cm and a thickness of 4 mm. This gives a column height of 64.5 cm and a total mass transfer area of 0.0219 m². The apparatus is designed for atmospheric pressures and temperatures up to 70 °C.”

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Fig. 2. Experimental set-up of the string of discs contactor. The figure is retrieved from Hartono et al. (2009).

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During operation, the inlet gas composition, containing N₂ and CO₂, was set by a mass flow controller and, with a gas flow rate of around 3 m³/hr, it was counter-currently contacted with the falling amine solution with a liquid rate of around 60 mL/min. At this liquid rate, a ripple-free and uniform film covered the surface of the discs. The inlet and outlet temperatures of the liquid and gas phase were registered by k-type thermocouples and the pressure was measured by a DP cell from Druck. The outlet CO₂ gas concentration was monitored by an IR CO₂ analyser and to avoid water condensation in the analyser, the gas was first cooled to around 10–15 °C before it was passed to the analyser. The IR analyser was calibrated before and after the experiment, and both calibrations were used in the calculation.

For each amine solution, the CO₂ absorption flux was measured for five different temperatures in the range of 29–63 °C. For each temperature, around 5 L of solution was pumped through the system and re-used for the next temperatures. The temperature and CO₂ concentration were recorded every 10 s and when stable conditions were maintained for at least 5 min (by visual inspection), the experiment was terminated. After each temperature, a liquid sample was taken for CO₂ and amine analysis to ensure that the experiments were operated with sufficient CO₂ driving force and to ensure that the amine concentration was not depleted by the reaction. The CO₂ concentration was determined by total inorganic carbon (TIC) analyses using TOC-L provided by Shimadzu and the amine content was determined by titrating with 0.2 N H₂SO₄ (Ma’mun et al., 2006). In all samples, the analysed CO₂ content was low (i.e. in the range of 0.004 to 0.025 mol_CO2/mol_amine) and therefore assumed to be in an acceptable range with respect to the used driving force of 0.18–0.24 kPa CO₂.”