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Virginia Tech

1. Teye, Frederick David. Continuous flash extraction of alcohols from fermentation broth.

Degree: MS, Biological Systems Engineering, 2009, Virginia Tech

A new method of in situ extraction of alcohols from fermentation broth was investigated. The extraction method exploited the latent advantages of the non-equilibrium phase interaction of the fluid system in the flash tank to effectively recover the alcohol. Carbon dioxide gas ranging from 4.2L/min to 12.6L/min was used to continuously strip 2 and 12% (v/v) ethanol solution in a fermentor with a recycle. Ethanol and water in the stripped gas was recovered by compressing and then flashing into a flash tank that was maintained at 5 to 70bar and 5 to 55 °C where two immiscible phases comprising CO2-rich phase (top layer) and H2O-rich phase (bottom layer) were formed. The H2O-rich bottom layer was collected as the Bottoms. The CO2-rich phase was continuously throttled producing a condensate (Tops) as a result of the Joule-Thompson cooling effect. The total ethanol recovered from the extraction scheme was 46.0 to 80% for the fermentor containing 2% (v/v) ethanol and 57 to 89% for the fermentor containing 12% (v/v) ethanol. The concentration of ethanol in the Bottoms ranged from 8.0 to 14.9 %(v/v) for the extraction from the 2 %(v/v) ethanol solution and 40.0 to 53.8 %(v/v) for the 12% (v/v) fermentor ethanol extraction. The Bottoms concentration showed a fourfold increase compared to the feed. The ethanol concentration of the Tops were much higher with the highest at approx. 90% (v/v) ethanol, however the yields were extremely low. Compression work required ranged from 6.4 to 20.1 MJ/kg ethanol recovered from the gas stream in the case of 12% (v/v) ethanol in fermentor. The energy requirement for the 2% (v/v) extraction was 84MJ/kg recovered ethanol. The measured Joule-Thompson cooling effect for the extraction scheme was in the range of 10 to 20% the work of compressing the gas. The lowest measured throttle valve temperature was -47 °C at the flash tank conditions of 70bar and 25 °C. Optimization of the extraction scheme showed that increasing the temperature of the flash tank reduced the amount of ethanol recovered. Increasing the pressure of the flash tank increased the total ethanol recovered but beyond 45bar it appeared to reduce the yield. The 12.6L/min carbon dioxide flow rate favored the high pressure(70bar) extraction whiles 4.2L/min appeared to favor the low pressure(40bar) extraction. The studies showed that the extraction method could potentially be used to recover ethanol and other fermentation products. Advisors/Committee Members: Agblevor, Foster Aryi (committeechair), Zhang, Chenming Mike (committee member), Achenie, Luke E. K. (committee member).

Subjects/Keywords: saturation temperature; equilibrium; Flashing; Bottoms; Tops; critical pressure; gas partition; Joule-Thompson coefficient; critical temperature; isothermal flash tank; throttling; saturation pressure

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APA (6th Edition):

Teye, F. D. (2009). Continuous flash extraction of alcohols from fermentation broth. (Masters Thesis). Virginia Tech. Retrieved from

Chicago Manual of Style (16th Edition):

Teye, Frederick David. “Continuous flash extraction of alcohols from fermentation broth.” 2009. Masters Thesis, Virginia Tech. Accessed January 25, 2021.

MLA Handbook (7th Edition):

Teye, Frederick David. “Continuous flash extraction of alcohols from fermentation broth.” 2009. Web. 25 Jan 2021.


Teye FD. Continuous flash extraction of alcohols from fermentation broth. [Internet] [Masters thesis]. Virginia Tech; 2009. [cited 2021 Jan 25]. Available from:

Council of Science Editors:

Teye FD. Continuous flash extraction of alcohols from fermentation broth. [Masters Thesis]. Virginia Tech; 2009. Available from: