BREWING
membrane housing. Dealcoholisation is carried out in three steps.
Step 1: Pre-concentration In pre-concentration the beer is pro- cessed through the membrane hous- ing removing ethanol and water. This step continues until a target volume reduction is achieved. This step will not reduce the ethanol concentration suf - ciently so a dia ltration step is employed Step 2: Dia ltration Dia ltration is the ltration under dilution and involves the addition of demin- eralised DAL to the feed stream. The process increases permeate ux and hence movement of the target solute across the membrane. Effectively you are washing the ethanol out of the beer. The volume of water added at the dia ltration step is equal to the volume of uid lost across the membrane as permeate so the volume in the system remains the same as after the precon- centration step. Step 3: Alcohol adjustment Dilution water is then added to the process tank to adjust the beer to the target ABV. The concentration of etha- nol in the permeate is not high enough (as low as 1% ABV) for sale without further processing but it can be used for alcoholic soft drinks. Operating costs for membrane systems tend to be higher than for thermal sys- tems. The water used to beer produced ratio is 2.5:1 all of which has to be chilled, deaerated, demineralised and ul- timately disposed of as process ef uent. Adnams mitigates this to a degree by using this cooled water for wort cooling and in its distillery. Energy costs are also signi cant with large motors on high- pressure pumps and cooling costs to keep beer temperature during processing. Additionally, membranes are relative- ly new technology so still expensive and require replacement more frequently than components in a non-mechanical thermal system. Although membrane systems do not subject the beer to thermal load there is still a signi cant impact on the avour of the beer processed. Molecules other than water and ethanol are rejected through the membrane. Changes in avour compounds caused by the membrane dealcoholisation are shown bin Table 2. As with thermal dealcoholisation there is a signi cant loss of aroma compounds and while this is slightly lower with mem-
The Alfa Laval De-alcoholisation Module enables breweries to produce non-alcohol or very low alcohol beer without facing the heavy capital investments typically required for such applications. The cost- and energy-ef cient de-alcoholisation concept provides chilled low-alcohol beer below 0.05% alcohol by volume. This is achieved by an innovative combination of diverse technologies, from beer degassing and culinary steam generation to vacuum stripping and alcohol condensing, which work in tandem as an integrated system. The system also produces a condensate stream composed of water, stripped alcohol and other volatiles that can be reused for ethanol production and concentration of aroma volatiles. © Alfa Laval.
than that of the osmotic pressure (in practice vastly greater). In the case of beer dealcoholisation, this is in essence applying pressure to a stream of beer to push the ethanol (and water) through a membrane which is selectively permea- ble for these molecules. Unlike standard dead-end mem- brane ltration the liquid bring pro- cessed runs parallel to the RO mem- brane which reduces fouling. The AFB is retained within the equipment and called the retentate while the ethanol, water and some vola- tiles are rejected across the membrane and termed the permeate. Selection of membranes for membrane dealcoholi- sation plants is critical. As well as the appropriate pore size for the molecules to be rejected the hydrophobicity/hydrophilicity of the membrane is also important to avoid fouling and rejection of molecules you want in the retentate. GEA and Alfa Laval sell similar mem- brane dealcoholisation plants. The Alfa Laval unit uses nano ltration whereas the GEA plant uses RO. These are skid
water and alcohol
Water and alcohol crossing the membrane
mounted, fully automated and almost plug and play units, carrying cleaning in place equipment. Additional plant required is, as a minimum, a receiving and recirculation vessel and facility to produce demineralised deaerated water. The bene t over thermal dealco- holisation is that they operate at a low temperature and hence contribute no thermal load. They are also designed to t into existing cellars so are smaller in size and certainly in height than thermal units. The GEA AromaPlus RO plants are used commercially at Adnams Brewery in Southwold UK and Kloster Andechs Brauerei in Germany. The unit at Adnams is operated at 0 ° C. Membrane dealcoholisation plants operate in a loop from and to the beer process tank. Pumps on the skid maintain a pressure of 30-40 bar in the
5 ● BREWER AND DISTILLER INTERNATIONAL
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