## 1 Introduction  
Absorption is a separation process used to capture many gases--such as CO\({}_{2}\)--which, when released into the atmosphere, contributes to the increase of global warming. The absorption technology for CO\({}_{2}\) capture mainly consists of the absorber column and the regeneration unit. The absorber column can be a plate column or packed column. The absorbent enters the absorber from the top, and the waste gas containing CO\({}_{2}\) enters the absorber from the bottom. The gas and liquid phases come into contact with each other on the trays or packing. The trays or packing material increase the gas-liquid interface, which increases mass and heat transfer between the contact phases. The CO\({}_{2}\) component passes from the gas phase to a liquid phase and is then absorbed. Knowledge of the hydrodynamic properties of trays is necessary for the design and operation of absorption columns because they control the liquid height on the trays and affect the pressure drop, tray efficiency, and flow conditions on the trays ([PERSON], et al., 1999) [1]. In the literature, various studies can be found on the influence of the inlet gas flow on the hydrodynamic characteristics and mass transfer in gas-liquid systems. Some studies discuss the influence of gas velocity on froth height and the height of clear liquid on the trays. [PERSON] (1984) [2] tested the effect of gas velocity on the height of clear liquid for three sieve trays. They plotted the height of the clear liquid versus the flow ratio \(\Psi^{0.25}\), they found that the height of the clear liquid was proportional to the flow ratio for froth regime. However, for the spray regime, they stated that the dependence of clear liquid height on the flow ratio group could not be detected. [PERSON] (1984) [2] also investigated the influence of liquid and gas rates on the clear liquid height by using a valve tray with a weir height of 25 mm. They established that the clear liquid height increases with liquid volume, where the clear liquid height decreases with increasing superficial air velocity. [PERSON], [PERSON] et al. (1988) [3] explored the effect of the superficial velocity of gas on the interfacial area in two different gas-liquid systems CO\({}_{2}\)-DEA and CO\({}_{2}\)-NaOH. The experiment was carried out in a laboratory column equipped with cross-flow sieve trays. They found that the total interfacial area increased when the superficial velocity was increased. [PERSON] (1999) [1] stated that the liquid height depends on the gas and liquid loads, gas and liquid properties, and some geometrical parameters such as the height and length of the weir, free hole area, hole diameter, etc. [PERSON], [PERSON] et al. (2001) [4] investigated the hydrodynamics of a sieve tray column for reactive distillation. The author observed that the clear liquid decreased significantly when the superficial velocity of the gas increased between 0.4-1 m/s. [PERSON] et al. (2001) [5] determined the height of froth and the height of clear liquid on dual-flow trays with 20% free area; the authors stated that there is a strong relationship between the height of froth and the height of clear liquid, as the height of froth increases when the height of clear liquid increases. The authors noted that the height of the clear liquid increases with the vapour velocity. [PERSON], [PERSON] et al. (2010) [6] studied hydraulic parameters such as dry pressure drop in a column with a diameter of 1.22 m. The column has two sieve trays and two chimney trays; the author observed that the pressure drop increases when the Fs factor is increased. Their experiments were conducted in a round tower with a diameter of 1.22 m for the air/water system; The author observed that the height of the clear liquid decreases as the velocity of the gas increases. [PERSON] et al. (2015) [7] reviewed experimental measurements of hydrodynamic and interface parameters performed on two pilot-scale rectangular valve tray columns.