Beer still

Lambic Beer. Lambic beer is made in Brussels and is one of the few top-fermented beers still brewed in Belgium. It is made from 60% badey... 

Doubler. A doubler is a pot still used to redistill whiskey and low wines from a beer still. The low wines are fed into the doubler where they are redistilled by way of steam enclosed in a scroll at the bottom of the still. The bottoms, the organic components remaining at the bottom of the still, are... 

The finished beer (final grain residue alcohol mixture) is ultimately agitated to resuspend its solids, and transferred to the beer well storage vessel for holding until it is pumped to the beer still. Distillers try to minimize aeration at this point to avoid formation of excessive aldehydes. 

From the beer well, the residue—alcohol suspension passes through a preheater where it is warmed by heat transfer from the vapors leaving the still. The preheated beer is then ready for distillation. The condensate from the preheater is returned to the beer still. 

Bourbon Distillation. The basic distillation system for the production of bourbon and other straight whiskeys consists of a beer still and a beer heater, thumper, or doubler (Fig. 4). The whiskey still consists of between 14 and 21 stripping trays. The upper portion of the still is fitted with either a bubble cap section or a section packed with copper rings to enhance the removal of unwanted flavors and ethyl carbamate precursors. The reduction of carbamate precursors requires strict adherence to a cleaning protocol with a 5% caustic solution as often as twice a week. 

In the United States alcohol is distilled and rectified from its wash by means of continuous stills. In smaller establishments all non-volatile materials and a substantial portion of the water are removed in a so-called beer still, Figure 20. On account of the partial rectification in the preheater the distillate from a 6% beer will frequendy run as high as 40 to 60 per cent alcohol. The crude alcohol is neutralized with some suitable alkali such as soda ash, and then purified and concentrated in an intermittent still, Figure 21. Assuming that the feed runs as high as 60 per cent alcohol, the feed is diluted so as to reduce the con-... 

Fig. 20.—Beer Still. (Redrawn from Robinson s Fractional Distillation. Courtesy McGraw-Hill Book Co., Inc.)...

The operation of the beer still shown in Figure 20 is performed as follows The alcoholic feed is supplied by a constant level feed tank A containing a ball float which controls a steam... 

Energy consumption in the beer still increases as its distillate composition gets closer to the azeotrope. On the other hand, energy consumption in the azeotropic-recovery column section of the process decreases as the feed to this section becomes richer in ethanol. It appears that this fundamental trade-off has not been studied in the literature. 

A pioneering paper by Ryan and Doherty explored several alternative heterogeneous azeotropic configurations using benzene as the entrainer. They examined two- and three-column flowsheets and concluded that the three-column flowsheet with a preconcentrator (beer still), an azeotropic column, and a recovery column was the economic optimum. They used approximate ternary diagram methods of analysis. 

Figure 6 in the Ryan-Doherty paper shows a binary feed composition to the azeotropic column of about 88 mol% ethanol. There is no discussion in the paper of the impact of this parameter on the optimum design. Fairly detailed information is given for the azeotropic column and the recovery column, but essentially nothing is provided about the beer still. 

The 88 mol% ethanol concentration is quite close to the azeotropic composition of 90mol%. Energy consumption in the beer still could be reduced by designing for ethanol concentrations further away from the azeotropic composition. However, lower ethanol concentrations in the feed to the azeotropic column will increase energy consumption in the azeotropic column. Clearly, there is an optimum beer still distillate composition. 

Other papers have also arbitrarily assumed beer still distillate compositions. For example, Martinez et al. specify a beer still feed flow rate of45.36 kmol/h with 10 mol% ethanol. Then they set the beer still distillate flow rate at 5.41 kmol/h. With negligible losses of ethanol in the bottoms, the distillate composition is 4.536/5.41 = 0.838, which is about 6 mol% away from the azeotropic composition. Li and Bai select an 85 mol% distillate. 

The feed of fermentation broth is assumed to be lOOOkmol/h with a composition of 5 mol% ethanol and 95 mol% water. The two design specifications in the beer still are a bottoms ethanol concentration of 50 ppm (molar) and a distillate ethanol concentration that is set for the three cases 75, 80, and 85 mol% ethanol. The variables that are manipulated to achieve these two specifications are the distillate flow rate and the reflux ratio. 

Tables 17.2 and 17.3 give results for the 80 and 75mol% cases. Since the beer still distillate composition is moved further from the azeotropic composition, energy and capital costs decrease, as does the optimum nmnber of stages. It is clear that lower beer still distillate compositions reduce costs in the beer stUl. In the next section, we see what the effect is in the azeotropic and recovery columns.

The beer still considered in the previous section can be optimized in isolation given a specified distillate composition. The downstream columns do not affect the beer still since there is no recycle back to it. However, the other two columns must be optimized together because of the recycle of the recovery column distillate back to the azeotropic column and the recycle of the organic phase from the decanter back to the azeotropic column. 

Beer still distillate (Dl) was fed on Stage 15 of a 32-stage azeotropic column. 

The azeotropic column feed flow rate was adjusted from that used in the previous study (216 kmol/h) to correspond to the 1000 kmol/h of fermenter broth fed to the beer still used in the present study. With a distillate composition of 85 mol% ethanol, this feed flow rate is 62.44 kmol/h. With this flow rate and with the number of trays and feed locations stated above, the reboiler duty (QR2) in the azeotropic column is 1.597 MW and the reboiler duty in the recovery column is 0.7122 MW. 

Remember that these results are for an 85 mol% ethanol beer stiU distillate. Combining all three columns is considered in the next section. We assume that the optimum numbers of stages in the azeotropic and recovery columns do not change significantly as the beer still distillate composition varies over the range of 75-85 mol% ethanol. 

The optimum beer still designs with their associated capital and energy costs are now combined with the azeotropic and recovery column designs for the three values of beer... 

The beer still distillate flow rate decreases slightly as distillate composition is increased but less organic reflux (R2) is required. This reduces reboiler duty in the azeotropic column (QR2). However, the reboiler duty in the beer still (QRl) increases as distillate composition is increased, as does the optimum number of stages in the beer still (NTl). So, beer still capital and energy costs increase while those costs in the azeotropic column decrease. 

The net result of all these effects on the total capital cost is an increase with increasing beer still composition. The net result of all these effects on the total energy cost is a minimum at a beer still composition of 80mol% ethanol. Total annual cost also is minimized at 80mol% ethanol. 

Benzene has been used in the cases studied in the previous sections. To see the effect of entrainer choice, the same basic process configuration was examined with cyclohexane substituted for benzene. The beer still is not affected. The number of stages and feed locations in the other two columns are kept the same as those used for benzene. The specifications are the same except that the 0.2 mol% impurity in the ethanol product stream is now cyclohexane. 

Beer still distillate composition, 80mol% ethanol azeotropic column, 62 stages 2 atm recovery column,... 

Optimization of the Beer Still (Preconcentrator) / 459 Optimization of the Azeotropic and Recovery Columns / 460... 

A7. Beer stills are distillation columns that process the raw feed from fermentation. This feed... 

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