Mass Transfer in Multiphasic Gas/Liquid/Liquid Systems. KLa Determination Using the Effectiveness-Number of Transfer Unit Method

Abstract

The Effectiveness-Number of Transfer Unit method (ε-NTU method) was applied to determine the overall mass transfer coefficient, KLa, of operating gas-liquid absorbers treating Volatile Organic Compounds (VOCs). This method requires the knowledge of the operating conditions (gas flow rate, QG; liquid flow rate, QL; scrubber volume V), the measurement of gaseous concentrations at the inlet, CGin, and at the outlet, CGout, of the contactor (in order to determine the effectiveness of the absorber ε) and the calculation of the Henry coefficient of the VOC between the gas and the liquid phases (HVOC). Coupled with the “equivalent absorption capacity” concept, the ε-NTU method was used to determine KLa of absorbers contacting a gas and a mixture of water and a Non Aqueous Phase, successfully. The method, validated from literature data for configurations countercurrent scrubbers and stirred tank reactors, could be used to simply determine the overall mass transfer coefficient of systems for which the standard KLa determination methods still remain non-reliable or inaccurate (viscous solvents, mixture of immiscible liquids, fermentation broths…).

KLa Determination Using the Effectiveness-NTU Method: Application to Countercurrent Absorbers in Operation Using Viscous Solvents for VOCs Mass Transfer

“…Moreover, the calculation procedure highlights the fact that the K L a mainly depends on the H VOC ( Figure 5). Such an expected result was consistent with the mathematical expression of the K L a given in Equation (14).…”

“…In such a case, the main difficulty lies in the knowledge of the H VOC . As a result, the ε-NTU method must be combined with the "equivalent absorption capacity" concept [12,13], thereby enabling calculation of the physical properties of the mixture [14].…”

“…As observed, the experimental data are diversified in terms of solvent used, solutes to be transferred (i.e., various H VOC values), and operating conditions. From the absorption efficiency values reported in these studies, the NTU and K L a values were calculated using Equations (19) and (14), respectively.…”

Volatile organic compounds absorption in a structured packing fed with waste oils: Experimental and modeling assessments

“…The experimental values of the overall volumetric mass transfer coefficients in the liquid phase K L a° were deduced from the experimental removal efficiencies E G and the absorption factor A considering the HTU-NTU method considering gas and liquid plug-flows at counter-current and at steady-state (Biard et al, 2018;Dumont, 2018;Rodriguez Castillo et al, 2019).…”

Experimental Study on Spray Breakup in Turbulent Atomization Using a Spiral Nozzle

“…Gas scrubbers are rather complicated devices, in which the polluted air is cleaned using a sprayed liquid, mostly various aqueous solutions depending on the gas to be removed. This includes, for example, CO 2 and VOC removal [1][2][3], flue gas desulphurization [4][5][6], and ammonia separation [7]. Last but not least, scrubbing systems have widely been recognized in separation of particulate matter [8][9][10][11][12], the release of which is due mostly to various combustion processes [13][14][15] and, for example, comminution technologies [16,17].…”