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…).
Highlights
The removal of volatile organic compounds (VOCs) in air can be achieved using bioscrubbers.some VOCs are poorly soluble in water leading to mass transfer limitations
The overall mass transfer coefficient, KL a, cannot be determined by the current methods available in the literature because they are usually based on the measurement of VOC concentration in the liquid phase
Authors reported that results were not significant: when the silicone oil volume fraction was doubled, efficiency was improved by only 3%
Summary
The removal of volatile organic compounds (VOCs) in air can be achieved using bioscrubbers. The overall mass transfer coefficient, KL a, cannot be determined by the current methods available in the literature because they are usually based on the measurement of VOC concentration in the liquid phase. These methods are not relevant for mixtures of NAP and water and there is always a need to develop a simple, standard and reliable method for KL a determination adapted to multiphasic gas/liquid/liquid systems. For this purpose, the Effectiveness—Number of Transfer Units (ε-NTU). It is demonstrated that the ε-NTU method can be applied successfully to the Stirred Tank Reactors (STR) configuration
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