Batch stripping of flavour active compounds from beer: Effect of dry matter and ethanol on equilibrium and mass transfer in a packed column
Ammari, Ali ; Schroën, Karin - \ 2019
Food and Bioproducts Processing 118 (2019). - ISSN 0960-3085 - p. 306 - 317.
Alcohol - CO - Equilibrium - Ester - Henry's law constant - Mass transfer coefficient
Physiochemical similarities of volatile compounds and their interactions with the beer matrix are the main challenging factors in selective separation of ethanol for the production of non-alcoholic beer and removal of excess (off-)flavours produced during fermentation, such as isoamyl acetate. In this paper, we are especially interested in the effect of beer dry matter, a complex mixture of carbohydrates and proteins, and of ethanol on flavour behaviour during treatment with a packed bed column using CO2 as a stripping agent. By analysing the gas phase at different dry matter concentrations, we observed that its’ presence is a facilitating factor for ethyl acetate and isoamyl acetate release, whereas isoamyl alcohol is retained in the liquid phase. These effects are a result of combined mass transfer effects and affinity for carbon dioxide, which are both affected by the presence of ethanol in the feed stream. Mass transfer analysis of isoamyl alcohol and ethanol revealed that the resistance is not controlled by their solubility in water but the affinity to CO2.
Development of ammonia mass transfer coefficient models for the atmosphere above two types of the slatted floors in a pig house using computational fluid dynamics
Rong, L. ; Aarnink, A.J.A. - \ 2019
Biosystems Engineering 183 (2019). - ISSN 1537-5110 - p. 13 - 25.
Airflow pattern - Ammonia emission - CFD - Mass transfer coefficient - Pig houses
Ammonia emissions from animal production systems are a concern due to their potential adverse effects on the environment. It is important for governments to adjust their policies to control ammonia emissions from animal production. To evaluate and quantify emission factors, process-based modelling is a cost-effective procedure, particularly due to the complex and diverse transfer chains. During the modelling process, ammonia mass transfer coefficient is one of the key parameters to be determined. However, inconsistencies are found in widely used expressions for mass transfer coefficients in ammonia volatilization models. This study used CFD simulations to derive the mass transfer coefficients above metal and concrete slatted floor in an experimental pig houses with 12 full-scale pig pens. Five ammonia mass transfer coefficient models were selected for comparison with the models derived from CFD simulations. It was noticed that the models derived from wind tunnel/flux chamber experiments usually predicted lower values of ammonia mass transfer coefficients compared to the models developed from full-scale measurements and/or numerical modelling. Care is needed to extrapolate the relationships developed under controlled laboratory conditions to the commercial barns. The results indicated also that the ammonia mass transfer coefficient relies heavily on the airflow patterns which could be affected by the ventilation systems, location of the inlet and outlets, internal partitions, floor types etc. This makes it very difficult to present a universal ammonia mass transfer coefficient model for pig houses.