Patent GB-700362-A (GB)
Title: Purifying fermentation alcohol by distillation
IPC: B01D3/00
Filed: 1950-11-17
Abstract: <PICT:0700362/III/1> <PICT:0700362/III/2> In a process for the purification of fermentation alcohol by extractive distillation in the presence of a substantial concentration of an aqueous dilution agent whereby impurities are removed in an overhead fraction taken from the distillation column and a dilute aqueous solution of (partly or wholly) purified ethanol is withdrawn at or near the base of the column, the rate of supply of heat to the column, is correlated with the strength of the dilute aqueous purified ethanol in a manner defined by an area of a graph which accompanies the Specification, and the rate of supply of water to column and the reflux ratio are defined by means of another graph.  The dilute aqueous ethanol is rectified in a second column to give either a high purity spirit ethanol or a whisky product.  Fermented mash containing 8.25 per cent. ethanol by volume, and volatile impurities (aldehydes, esters, light fusel oil, and amyl alcohols) amounting to about 0.084 per cent., is fed at the rate of 1700 lbs. per hour and at 90 DEG F. through inlet 11 (Fig. 4) into column 10 which contains 50 plates. The column is supplied through inlet 12 with 2.4 lbs. of open steam per lb. of ethanol in the mash; and 1.26 lbs. of water at 100 DEG F. are introduced into the column through inlet 13.  The temperature of the upper section of the column is maintained at 185 DEG F. (760 mm.), and that at the base at 209.6 DEG F. (900 mm.).  The vapours taken overhead, which contain about 99.7 per cent. of the volatile impurities in the mash, are condensed in condensers 15 and 17; and CO2 is released through vent 19.  The condensate is passed to decanter 22, where it separates into an oil layer which is withdrawn through line 23, and a water layer.  The bottoms which collect at the base of column 10 contain 2.04 mol. per cent. ethanol; and this is introduced through line 26 into column 27, which is supplied with steam through inlet 28. Purified and concentrated ethanol is withdrawn from column 27 through line 39 which is connected to the 4th, 5th or 6th plate below the top of the column.  A heads cut (about 3 per cent. by weight of the product withdrawn through line 39) is taken off through line 29 and condensed in condensers 30 and 32.  The condensate is recycled to column 10 through line 35.  Fusel oil is taken off from the side of column 27 just above the feed inlet, and is passed through lines 38 and 35 to column 10.  The bottoms withdrawn from the base of column 27, is rejected.  A whisky product may be obtained using the apparatus shown in Fig. 7 wherein a beer still 42, having a feed line 43, precedes the extractive distillation column 10.  A fraction containing 1 to 3 per cent. by weight of the total alcohol and rich in aldehydes is taken off from the head of the beer still through line 57.  The wines are drawn off from the upper part of the beer still and passed to column 10 through line 46.  A fraction rich in aldehyde and very light esters is removed from the head of column 10 through line 58; and a fraction of undesirable impurities may be removed from the upper part of the column through line 63.  A fraction may be removed from near the top of column 10 through line 61, and introduced into the rectifying column 27 at a few plates above the feed thereto of the bottoms from column 10.  The whisky product may be taken off through line 59 on from a point several plates below the top of column 27.  Several additional steam inlets 62, 62a, and 62b are provided for the extractive distillation column 10.