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Pervaporative aroma recovery during beverage processing

Karlsson, Hans O E (1996)
Abstract (Swedish)
Popular Abstract in Swedish

I denna studie har de grundläggande aspekterna på mass- och värmetransport i membrantekniken pervaporation studerats. Speciell tonvikt har lagts vid pervaporations användbarhet i samband med aromämnesåtervinning.



Masstransporten i pervaporation påverkas av ett yttre masstransport- motstånd kallat koncentrationpolarisation. Detta fenomen kan orsaka att fluxen av de selektivt permeerade ämnena ofta minskas med flera tiotals procent om förhållandena i feedflödet är ogynnsamma. Närvaron av ett visst aromämne i den blandning som pervaporeras tycks inte påverka masstransporten av andra ämnen i blandningen. Detta beror främst på de mycket låga koncentrationer som aromämnena normalt... (More)
Popular Abstract in Swedish

I denna studie har de grundläggande aspekterna på mass- och värmetransport i membrantekniken pervaporation studerats. Speciell tonvikt har lagts vid pervaporations användbarhet i samband med aromämnesåtervinning.



Masstransporten i pervaporation påverkas av ett yttre masstransport- motstånd kallat koncentrationpolarisation. Detta fenomen kan orsaka att fluxen av de selektivt permeerade ämnena ofta minskas med flera tiotals procent om förhållandena i feedflödet är ogynnsamma. Närvaron av ett visst aromämne i den blandning som pervaporeras tycks inte påverka masstransporten av andra ämnen i blandningen. Detta beror främst på de mycket låga koncentrationer som aromämnena normalt har i drycker. Dock kan närvaron av andra ämnen som finns i högre koncentrationer i blandningen, t.ex. etanol, i vissa fall påverka masstransporten av aromämnen. Temperaturen som processen utförs vid är en mycket viktig parameter för hur processen uppför sig. Den viktigaste effekten syns på fluxen som ökar exponentiellt med temperaturen, vilket är viktigt för kostnaderna för processen. Många aromämnen är dock temperaturkänsliga och den slutliga processtemperaturen måste därför vara en avvägning mellan processekonomi och aromämnenas temperaturkänslighet. Det membranmaterial som används är avgörande för processens användbarhet för aromåtervinning. Ett antal olika kommersiella membran finns tillgängliga, och speciellt tre tycks vara lämpliga för aromåtervinning.



Eftersom det sker en fasändring när ämnen transporteras från den vätskeformiga feeden till det gasformiga permeatet förbrukar pervaporationsprocessen värme. Värmetransporten i processen kan beskrivas på ett liknande sätt som masstransporten beskrivs.



Resultaten från datorsimuleringar av storskaliga pervaporationsanläggningar för aromåtervinning visar att pervaporation kan användas för aromåtervinning. För fyra av de fem aromämnen, för vilka simuleringar gjorts, är återvinningsgraden mycket hög. Både drifts- och investeringskostnader är starkt beroende av vilket membranmaterial som används i processen. Används membran som ger höga flux är kostnaderna lägre medan aromåtervinningen är sämre. (Less)
Abstract
In this study, the fundamental mass and heat transfer properties of the membrane separation process called pervaporation were investigated. The suitability of pervaporation for aroma compound recovery was especially evaluated.



The mass transfer in pervaporation is affected by an external mass transfer resistance in the liquid feed boundary layer, i.e. the concentration polarization phenomenon. The fluxes of the selectively permeated compounds can often be reduced by several tens of percent if the feed flow characteristics are unfavourable. The presence of a certain aroma compound in the pervaporated mixture does not seem to affect the mass transfer of other compounds in the mixture. This behaviour is mainly due to the... (More)
In this study, the fundamental mass and heat transfer properties of the membrane separation process called pervaporation were investigated. The suitability of pervaporation for aroma compound recovery was especially evaluated.



The mass transfer in pervaporation is affected by an external mass transfer resistance in the liquid feed boundary layer, i.e. the concentration polarization phenomenon. The fluxes of the selectively permeated compounds can often be reduced by several tens of percent if the feed flow characteristics are unfavourable. The presence of a certain aroma compound in the pervaporated mixture does not seem to affect the mass transfer of other compounds in the mixture. This behaviour is mainly due to the normally very low concentrations of aroma compounds in beverages. The presence of other compounds, e.g. ethanol, at high concentrations in the separated mixture seems, in some cases, to affect the mass transfer of the aroma compounds. The temperature at which the pervaporation process is carried out strongly affects the performance of the process. The most important effect of the process temperature is, however, that mass fluxes increase exponentially as the temperature increases, a fact which is important for process economics. However, some aroma compounds are heat sensitive and the actual process temperature is therefore a trade-off between process economics and the heat sensitivity of aroma compounds. The membrane material used in pervaporation determines, to a large extent, the performance of the process. A number of commercially available membranes exist, and three appear to be suitable for aroma recovery.



The basis of the heat transfer in pervaporation is the change in state that permeants are subjected to as they are transported from the liquid feed to the vapour permeate. The pervaporation process consequently consumes heat, and the heat transfer in the process can be described in a similar way as for the mass transfer.



Computer simulations of the behaviour of large-scale pervaporation units for aroma recovery indicate that pervaporation could be used as a technique for aroma recovery. For four of the five aroma compounds investigated the recovery degrees are very high. Both the investment and running costs for a pervaporative aroma recovery unit are extremely dependent on the choice of membrane material. High-flux membranes give lower costs but poorer process performance. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Dr Wijmans, Johannes G, Membrane Technology and Research, Inc., Menlo Park, CA, USA
publishing date
type
Thesis
publication status
published
subject
keywords
membranes, pervaporation, aroma compounds, mass transfer, heat transfer, theory, simulations, Food and drink technology, feasibility, aroma recovery, Livsmedelsteknik
pages
228 pages
publisher
Food Technology, Engineering and Nutrition, Lund University
defense location
Lecture hall C, Center for Chemistry and Chemical Engineering
defense date
1996-09-27 10:15
external identifiers
  • Other:ISRN: LUTKDH(TKLT-1022)1-228
language
English
LU publication?
no
id
4cafd188-3d33-4db6-865b-d2f4b140d92a (old id 27624)
date added to LUP
2007-06-05 14:28:00
date last changed
2016-09-19 08:45:05
@misc{4cafd188-3d33-4db6-865b-d2f4b140d92a,
  abstract     = {In this study, the fundamental mass and heat transfer properties of the membrane separation process called pervaporation were investigated. The suitability of pervaporation for aroma compound recovery was especially evaluated.<br/><br>
<br/><br>
The mass transfer in pervaporation is affected by an external mass transfer resistance in the liquid feed boundary layer, i.e. the concentration polarization phenomenon. The fluxes of the selectively permeated compounds can often be reduced by several tens of percent if the feed flow characteristics are unfavourable. The presence of a certain aroma compound in the pervaporated mixture does not seem to affect the mass transfer of other compounds in the mixture. This behaviour is mainly due to the normally very low concentrations of aroma compounds in beverages. The presence of other compounds, e.g. ethanol, at high concentrations in the separated mixture seems, in some cases, to affect the mass transfer of the aroma compounds. The temperature at which the pervaporation process is carried out strongly affects the performance of the process. The most important effect of the process temperature is, however, that mass fluxes increase exponentially as the temperature increases, a fact which is important for process economics. However, some aroma compounds are heat sensitive and the actual process temperature is therefore a trade-off between process economics and the heat sensitivity of aroma compounds. The membrane material used in pervaporation determines, to a large extent, the performance of the process. A number of commercially available membranes exist, and three appear to be suitable for aroma recovery.<br/><br>
<br/><br>
The basis of the heat transfer in pervaporation is the change in state that permeants are subjected to as they are transported from the liquid feed to the vapour permeate. The pervaporation process consequently consumes heat, and the heat transfer in the process can be described in a similar way as for the mass transfer.<br/><br>
<br/><br>
Computer simulations of the behaviour of large-scale pervaporation units for aroma recovery indicate that pervaporation could be used as a technique for aroma recovery. For four of the five aroma compounds investigated the recovery degrees are very high. Both the investment and running costs for a pervaporative aroma recovery unit are extremely dependent on the choice of membrane material. High-flux membranes give lower costs but poorer process performance.},
  author       = {Karlsson, Hans O E},
  keyword      = {membranes,pervaporation,aroma compounds,mass transfer,heat transfer,theory,simulations,Food and drink technology,feasibility,aroma recovery,Livsmedelsteknik},
  language     = {eng},
  pages        = {228},
  publisher    = {ARRAY(0xa490b48)},
  title        = {Pervaporative aroma recovery during beverage processing},
  year         = {1996},
}