GB2457186A

GB2457186A - Installation for the distillation of drinking alcohol,especially whiskey

Info

Publication number: GB2457186A
Application number: GB0908324A
Authority: GB
Inventors: Daniel Bethge; Paul Hildenbrand; John Ross; Conn Lynch
Original assignee: GEA Wiegand GmbH; William Grant and Sons Ltd
Current assignee: GEA Wiegand GmbH; William Grant and Sons Ltd
Priority date: 2006-10-18
Filing date: 2007-10-18
Publication date: 2009-08-12
Anticipated expiration: 2027-10-18
Also published as: DE102006049175A1; GB2457186B; WO2008046633A1; DE102006062885A1; WO2008046626A2; EP2079538B1; BRPI0718474A2; WO2008046626A3; RU2440410C2; JP4773563B2; GB2457187A; RU2009118391A; GB0908324D0; JP2010506574A; EP2079538A1; PL2079538T3; GB2457187B; GB0908325D0; BRPI0718474B1

Abstract

The invention relates to an installation for the distillation of drinking alcohol, especially whiskey, comprising two distillation columns (5a,73) stripping the crude alcohol vapors from the fermented mash and a rectification column (17a) increasing the alcohol content of the crude alcohol. At least a part of the crude alcohol vapors of a first distillation column (5a) is condensed in an evaporator, especially a falling film evaporator (39a), thereby producing low pressure water vapor from the distiller's wash or expansion vapors from the distiller's wash, the pressure and/or temperature thereof being increased in a mechanical condenser (49a) and being fed to the second distillation column (73) stripping the alcohol vapors from the fermented mash, to heat the same. The energy requirement of the distillation installation can therefore be reduced. Since the mechanical condenser does not condense alcoholic vapors but water vapor, the condenser (49) does not require an explosion-protected design.

Description

Plant for the distillation of potable alcohol, in particular whisky

Description

The invention relates to a plant for the distillation of potable alcohol, in particular whisky from fermented mash.

Conventional distillation plants for potable alcohol, in particular whisky, drive the alcohol out of fermented and therefore alcohol-containing mash by means of a distillation column, also referred to as a mash column.

The preheated, liquid mash is fed to the distillation column in an upper region. The heat energy required for the distillation is fed to the distillation column in the bottom region, for example by directly blowing in fresh steam or indirectly via a reboiler heated by vapour of a further stage of the distillation plant, i.e. a heat exchanger, through which the spent mash collecting in the bottom region of the distillation column is subjected to a forced circulation. Usually, the reboiler of the distillation column is heated by top vapour of a rectification column increasing the alcohol content of the crude alcohol taken off in the distillation column.

The rectification column is usually operated at slightly superatmospheric pressure and at a higher top temperature than the distillation column operated at reduced pressure, so that the heat energy of the top vapour of the rectification column is as a rule sufficient for heating the distillation column. Here, the rectification column is heated by fresh steam.

Conventional distillation plants for potable alcohol require a comparatively large amount of external energy for the distillation process. In addition, the energy balance for the distillation plant must be carefully tailored if sensory changes of the potable alcohol ar to be avoided. A change in the taste of the potable alcohol may occur, for example, on local overheating of the alcohol product stream. Thus, the top of the distillation column contains, for influencing the sensory properties of whisky, a copper packing which reacts chemically with the alcohol vapour and the reaction properties of which change in a temperature-or pressure-dependent manner.

Depending on the column temperature, there is a possibility of crack reactions, through which constituents, for example of the spent mash, are converted into readily volatile substances which can enter the crude alcohol.

It is an object of the invention to provide a plant for the distillation of potable alcohol, in particular whisky, which operates in an energy-efficient manner without influencing the sensory properties of the potable alcohol.

The invention starts from a plant for the distillation of potable alcohol, in particular whisky, from fermented mash, comprising: * at least one distillation column taking off alcohol vapour from the fermented mash, * a condenser arrangement condensing at least a part of the alcohol vapour and * a rectification column which increases the alcohol concentration and the top vapour of which heats a reboiler of the distillation column.

The above object is achieved, according to the invention, in that the fermented mash can be fed tO two distillation columns which take off alcohol vapour from the fermented mash and feed the rectification column in parallel and of which a first distillation column is heated by means of the reboiler, preferably to a distillation temperature of not more than 85°C, the condenser arrangement comprises an evaporator utilizing the heat of condensation of at least a part of the alcohol vapour of the first distillation column for producing steam and the top vapour of the first distillation column can be fed to the evaporator of the condensation arrangement, and in that the steam can be fed via a mechanical compressor increasing the pressure and/or the temperature of the steam to a second of the two distillation columns for heating said column, the second distillation column being heated by the compressed steam of the mechanical compressor to a distillation temperature lower than the distillation temperature of the first distillation column.

In order to keep the energy requirement for the distillation plant particularly low, two distillation columns parallel on the product side but connected in series with respect to energy are provided. In this case, the fermented mash is fed to two distillation columns which feed the rectification column in parallel and of which a first distillation column is heated by means of the reboiler, preferably to a distillation temperature of not more than 85°C, and the top vapour of this first distillation column is fed to the evaporator of the condensation arrangement. In this embodiment, the second distillation column is heated by the compressed steam of the mechanical compressor to a maximum distillation temperature which is lower than the distillation temperature of the first distillation column. The top temperature of the warmer, first distillation column is expediently once again 55 to 70°C at a top pressure of about 0.5 bar. The second, colder distillation column is operated, for example, at a top temperature between 45 and 55°C and a top pressure between 0.25 and 0.35 bar.

owing to the lower top temperature and the lower top pressure of the colder distillation column, in this variant the pressure of the compressed steam which is to be produced by the mechanical compressor also decreases arid the temperature difference by which the compressor must increase the temperature of the steam is also smaller. Overall, the electrical energy to be applied for the compression is lower.

In such a distillation plant, not only the heat content of the top vapour of the rectification column but also the heat content of the top vapour taken off from the first distillation column and containing the crude alcohol is utilized for heating the second distillation column. The mechanical compressor increases the energy content or the condensation temperature of the alcohol vapour, which otherwise cannot be sufficiently utilized for heating the distillation column. What is important is that the energy required for this purpose can be provided simply and economically not in the form of fresh steam which is expensive to provide but in the form of electrical energy for the motor drive of the mechanical compressor. What is furthermore important is that the mechanical compressor does not compress the alcohol vapour directly but compresses steam which is produced indirectly by means of the evaporator. The compressor therefore need not be designed to be explosion-proof, which simplifies the design of the distillation plant.

The evaporator may be a forced-circulation evaporator.

However, a downf low evaporator is preferred since such an evaporator can be operated with a relatively small temperature difference of, for example, about 50 between the heating circulation temperature and the evaporator exit temperature, which increases the efficiency and the specific heat transfer.

The evaporator is expediently arranged in a forced circulation in which a liquid supplying the steam circulates. The liquid may be spent mash from the bottom region of the distillation column or flash vapour produced from the spent mash. Since the spent mash is taken off hot from the bottom region of the distillation column, the steam can be produced in an energy-efficient manner. In order to ensure that substances forming through denaturing reactions do not enter the alcohol vapour of the distillation column, exclusively preheated fresh water can be used to produce the steam. The circulation ioop preferably contains a separator which separates off the steam, for example in the form of a gravity separator, in order to keep solids of spent mash or other suspended substances out of the steam. The separator can also be used for producing flash vapour from spent mash.

This steam is preferably low-pressure steam having a pressure of 200 to about 250 mbar. The pressure of the steam is therefore about 60 to 80 mbar lower than the top pressure in the distillation column. The compressor increases the pressure of the steam to a value greater than the value of the top pressure, for example to 500 to 600 mbar. The compressor may be a customary compressor.

However, rotary vane compressors, such as fans for example, are also particularly suitable. Of course, the mechanical compressor may also comprise a plurality of mechanical compressor stages connected in series with one another.

The mechanical compressor increases not only the pressure of the steam but also the temperature thereof. In order to avoid overheating of the compressed steam to above the temperature required in the distillation column, cooling water may be mixed with the steam prior to compression.

The compressed steam is expediently blown directly into the bottom region of the distillation column.

The top temperature of the rectification column is expediently above 85°C, for example between 85 and 110°C, at a superatmospheric pressure between 1 and 3 bar. In order to reduce the energy requirement of the rectification column, the latter expediently has more than 50 trays, although the rectified potable alcohol is taken off here not via the top of the rectification column but in an upper region of the column located therebelow, in order to avoid enrichment with low-boiling constituents.

Of course, the condensation arrangement may comprise a heat exchanger downstream of the evaporator in the product stream of the alcohol vapour and intended for preheating the fermented mash to be fed to the distillation column, in order to be able to further utilize the heat content of the alcohol vapour of the distillation column which heats the evaporator. The alcohol product stream from the condensation arrangement can be fed to the distillation column and optionally to the rectification column as top ref lux.

Below, an example of embodiment of the invention is explained in more detail with reference to a drawing. Here:

Fig. 1 shows a diagram of a distillation plant intended for potable alcohol, in particular whisky, with an explanation for understanding the invention explained with reference to fig. 2, and Fig. 2 shows a diagram of a distillation plant set up according to the invention and comprising two distillation columns.

Firstly, some aspects which are important for understanding the distillation plants according to the invention which are shown in fig. 2 should be explained with reference to fig. 1, these aspects per se not forming part of the subject matter of the invention.

Fig. 1 shows a distillation plant for potable alcohol, in particular whisky, to which fermented, i.e. ethyl alcohol-containing, mash is fed from a previous stage 1 of the alcohol production process. The mash is heated in a preheater 3 to the distillation temperature of a distillation column 5 and fed via a pipe 7 of the distillation column 5, at a middle level but below a catalytic copper packing 9, to the distillation column 5.

The top region of the distillation column 5, often also referred to as a mash column, is indicated at 11.

The crude alcohol taken off as alcohol vapour from the top region 11 of the distillation column S is condensed in a multistage condenser arrangement 13 and passed as feed in liquid form by a conveying pump 15 to a rectification column 17 via a preheater 19 heating the crude alcohol to the rectification temperature of the rectification column 17. The rectification column 17 increases the alcohol content of the crude alcohol of the distillation column 5 to about 94% by volume. Stages for separating of f the fractions undesired in the potable alcohol (fusel oils) are present but not shown. The rectification column 17 discharges the potable alcohol end product at 21 from a column position below its top region 23.

Top vapour taken of f from the top region 23 of the rectification column 17 via a pipe 25 is fed to a reboiler 27 of the distillation column 5, which reboiler takes off spent mash occurring in the bottom region 33 of the distillation column 5 via a forced circulation 31 provided with a pump 29 and via a bottom region connection 35 and, after heating in the reboiler 27, recycles said spent mash to the bottom region 33 of the distillation column 5 for heating said column. The reboiler 27 at the same time forms the top condenser of the rectification column 17 and delivers reflux condensed from the top vapour via a pipe 37 to the top region 23 of the rectification column 17.

The distillation column S is operated at a slightly reduced pressure of about 300 to 500 mbar at a top vapour temperature between 55 and 70°C. The rectification column 17 operates at a slightly superatmospheric pressure of not more than 3 bar absolute and a top vapour temperature between 85 and 110°C. In general, in the case of mash raw materials having a relatively high protein content, such as for example rye, wheat, barley, etc., the temperature of the distillation column should not exceed 85°C. Under the operating conditions mentioned, the energy content of the top vapour of the rectification column 17 expediently heated by means of fresh steam is not sufficient for heating the distillation column 5 exclusively via the reboiler 27. The first stage of the condenser arrangement 13 is therefore formed as a falling-film evaporator 39 which vaporizes fresh water circulating in a forced circulation 43 provided with a pump 41. The fresh water is fed in at 45 in preheated form and leaves the falling- film evaporator 39 via a gravity separator 47 as low-pressure steam, which is blown directly into the bottom region 33 of the distillation column 5 via a mechanical compressor 49 with a pressure increased compared with the low-pressure steam and an increased temperature. The low-pressure steam has a pressure of about 200 to 250 mbar on the entrance side of the compressor 49, which is raised by the compressor 49 to an exit pressure between 500 and 600 mbar at a temperature between 70 and 90°C.

In the illustrated example of embodiment, the mechanical compressor 49 comprises three mechanical compressor stages 51 increasing the pressure serially. In principle, however, a single compressor stage is sufficient provided that it meets the requirements with regard to the pressure increase and temperature increase. In order to avoid overheating of the compressed steam, additional water is optionally injected at the entrance of each compressor stage 51 from a source 53. The compressor 49 or its compressor stages 51 may be conventional compressors. Rotary vane compressors or fans are particularly suitable.

In principle, it is also possible to use other evaporator types instead of the falling-film evaporator 39. However, an advantage of the falling-film evaporator is its small temperature difference of, for example, 5°C between the entrance temperature of the top vapour of the distillation column 5 which is to be at least partly condensed and the exit temperature of the low-pressure steam. The energy content of the top vapour can be better utilized in this manner. The electrical energy required for the motor drive of the mechanical compressor 49 can be reduced in this manner. In principle, the mechanical compressor 49 could also be in the form of a steam jet compressor, which, however, would increase the effort involved in providing fresh steam, whereas the provision of electrical energy presents no problems.

Since the top vapour of the distillation column 5 is not completely condensed in the falling-film evaporator 39, the uncondensed vapour fraction is fed at 55 to the preheater 3 forming the second stage of the condensation arrangement 13, for preheating the mash. The exit vapour of the preheater 3 is finally fed to a main condenser 57 which forms the third stage of the condensation arrangement 13 and discharges the crude alcohol as liquid condensate for passing on to the rectification column 17.

The main condenser 57 is cooled by cooling water which is fed in at 59. The alcohol condensate of the main condenser 57 is combined with the alcohol condensate of the falling-film evaporator 39, taken off at 61, and the alcohol condensate of the preheater 3, taken off at 63.

The pressure in the distillation plant is adjusted by means of a vacuum pump 65 connected to the main condenser 57. It should also be stated that the crude alcohol condensate produced in the condensation arrangement 13 is also fed via a pipe 67 as retlux to the distillation column 5, in particular before it has passed through the preheater 19. The spent mash obtained in the distillation column 5 is discharged from the circulation loop 3]. of the reboiler 27 and, at 69, fed for further use, for example in a drying process for use as animal feed or the like. The separator 47 separates entrained liquid and droplets from the vapour, in order to ensure trouble-free operation of the compressor 49. The production of a slurry at 71 prevents lime deposits and the like in the downf low evaporator 39.

A distillation plant according to the invention is described below. Components having the same action are designated with the reference numerals of fig. 1 and provided with the letter a for distinction. For the explanation of the set-up and of the mode of action,

reference is made to the above description.

Fig. 2 shows a distillation plant which comprises a further distillation column 73 in addition to the distillation column 5a heating the falling-film evaporator 39a by means of its top vapour. The distillation columns 5a and 73 are connected in parallel with regard to the fermented mash fed in at la and preheated in the preheater 3a to the distillation temperature of the distillation columns 5a, 73. Regarding the energy recovery and heating, the distillation columns are connected in series and are operated at different top temperatures and top pressures. The "warmer" distillation column 5a is heated via its reboiler 27a and operated at a temperature between 55 and 70°C at a pressure of about 0.5 bar, relative to the top region ha. The "colder" distillation column receives the fermented mash from the preheater 3a, once again in its middle region, via a pipe 75, and is operated with a top temperature between 45 and 56°C at a pressure between 0.25 and 0.35 bar in its top region 77.

While the alcohol vapour taken of f from the top region ha of the distillation column 5a is at least partly condensed in the falling-film evaporator 39a and subsequently fed to the main condenser 57a via a pipe 79 for complete condensation to liquid crude alcohol, the alcohol vapour taken off from the top region 77 of the distillation column 73 is fed to the main condenser 57a after partial condensation in the preheater 3a.

In contrast to the distillation plant of fig. 1, the low-pressure steam produced in the falling-film evaporator 39a is fed, after the pressure increase and the temperature increase in the mechanical compressor 49a, not to the distillation column 5a heating the falling-film evaporator 39a but to the "colder" distillation column 73a for heating. The compressed steam is once again blown directly into the bottom region 81 of the distillation column 73. Since the distillation column 73 operates at lower pressure and lower distillation temperature than the distillation column 5a, the mechanical compressor 49a can be designed for a smaller pressure and temperature increase, which reduces the energy requirement.

In the example of embodiment of fig. 1, the falling-film evaporator producing the low-pressure steam is fed by preheated fresh water. In the distillation plant of fig. 2, the low-pressure steam is produced from spent mash flash vapour which is obtained in a flash separator 47a located in the forced circulation 43a. For feeding the spent mash, the flash separator 47a is connected via a pipe 83 to the bottom region connection 35a of the distillation column 5a and via a pipe 85 to a bottom region connection 87 of the distillation column 73. The spent mash obtained in the distillation columns 5a and 73 is taken off from the flash separator 47a and fed at 69a for further use, for example once again to a drying process. Since the spent mash already preheated to the distillation temperature, or the vapour thereof, is used for producing the low-pressure steam, the energy requirement of the distillation plant is further reduced.

Of course, the falling-film evaporator 39a can also be fed in the example of embodiment of fig. 2 with preheated fresh water, as was described for the distillation plant of fig. 1. Alternatively, the falling-film evaporator 39 from fig. 1 can also be fed with spent mash and/or spent mash flash vapour of the distillation column 5.

The distillation column 73 also has, above the inflow pipe 75, a copper packing 87 similar to the copper packing 9a of the distillation column 5a. The reflux pipe 67a ensuring the ref lux of liquid crude alcohol to the distillation column 5a also supplies the distillation column 73 with alcohol ref lux.

The condensation arrangement 13a once again comprises three stages, the falling-film evaporator 39a forming the top condenser of the distillation column 5a and the preheater 3a forming the top condenser of the distillation column 73. The main condenser 57a is assigned jointly to the distillation columns 5a and 73.

Claims

Claims 1. Plant for distilling potable alcohol, in particular whisky from fermented mash, comprising at least one distillation column (5a) taking of f alcohol vapour from the fermented mash, a condenser arrangement (13a) condensing at least a part of the alcohol vapour and a rectification column (17a) which increases the alcohol concentration and the top vapour of which heats a reboiler (27a) of the distillation column (5) characterized in that the fermented mash can be fed to two distillation columns (5a, 73) which take off alcohol vapour from the fermented mash and feed the rectification column (17a) in parallel and of which a first distillation column (5a) is heated by means of the reboiler (27a), preferably to a distillation temperature of not more than 85°C, the condenser arrangement (l3a) comprises an evaporator (39a) utilizing the heat of condensation of at least a part of the alcohol vapour of the first distillation column (5a) for producing steam, and the top vapour of the first distillation column (5a) can be fed to the evaporator (39a) of the condensation arrangement (13a), and in that the steam can be fed via a mechanical compressor (49a) increasing the pressure and/or the temperature of the steam to a second (73) of the two distillation columns (5a, 73) for heating said column, the second distillation column (73) being heated by the compressed steam of the mechanical compressor (49a) to a distillation temperature lower than the distillation temperature of the first distillation column (5a).
2. Plant according to Claim 1, characterized in that the evaporator (39) is in the form of a falling-film evaporator.
3. Plant according to Claim 1 or 2, characterized in that fresh water, in particular preheated fresh water, or spent mash or spent mash flash vapour can be fed to the evaporator (39a) for producing the steam.
4. Plant according to Claim 3, characterized in that the mechanical compressor (49a) is connected via a separator (47a) separating of f the steam to a circulation (43a) passed through the evaporator (39a) and intended for fresh water or spent mash or spent mash flash vapour.
5. Plant according to any of Claims 1 to 4, characterized in that the mechanical compressor (49a) comprises a plurality of mechanical compressor stages connected in series.
6. Plant according to any of Claims 1 to 5, characterized in that the steam compressed by the mechanical compressor (49a) is fed directly to the distillation column (73).
7. Plant according to any of Claims 1 to 6, characterized in that the rectification temperature of the rectification column (17a) is higher than 85°C and the alcohol production stream can be fed to the rectification column (17a) via a preheating heat exchanger (19a).
8. Plant according to any of Claims 1 to 7, characterized in that the rectification column (17a) has more than 50 trays.
9. Plant according to any of Claims 1 to 8, characterized in that the condenser arrangement (13a) comprises a heat exchanger (3a) downstream of the evaporator (39a) in the product stream of the alcohol vapour and intended for preheating the fermented mash to be fed to the distillation column.
10. Plant according to any of Claims 1 to 9, characterized in that a part of the alcohol product stream can be fed as ref lux to the condensation arrangement (13a) of each distillation column (Sa, 73)