WO1998054290A2

WO1998054290A2 - Process and plant for treatment of distillery lees

Info

Publication number: WO1998054290A2
Application number: PCT/GB1998/001536
Authority: WO
Inventors: Andrew John Teece; Michael John Hoole
Original assignee: Memcor Limited
Priority date: 1997-05-29
Filing date: 1998-05-27
Publication date: 1998-12-03
Also published as: GB9926973D0; WO1998054290A9; GB2340487A; AU7664998A; WO1998054290A3

Abstract

A process is described for the treatment of distillery lees containing copper values and waxy materials. This process comprises passing distillery lees containing copper values and waxy materials to a settling zone, retaining the distillery lees in the settling zone for a period of time effective for allowing settlement of waxy solids therefrom, recovering a liquid phase from the settling zone, contacting the liquid phase with a cation exchange resin in a first ion exchange zone having an inlet region and an outlet and containing a charge of a cation exchange resin, the cation exchange resin in the first ion exchange zone being at least partially in the H+ form, recovering an intermediate liquor from the first ion exchange zone, contacting the intermediate liquor with a cation exchange resin in a second ion exchange zone, the cation exchange resin in the second ion exchange zone being at least partially in the H+ form, recovering a final liquor having a reduced copper content from the second ion exchange zone, and backwashing ion exchange resin of the inlet portion of the first ion exchange zone with a portion of the final liquor to remove waxy materials deposited on the ion exchange resin therefrom.

Description

PROCESS AND PLANT FOR TREATMENT OF DISTILLERY LEES

This invention relates to a process for the treatment of spent distillery lees and to a plant for utilisation of such a process . In the production of spirits for consumption, such as whisky, it is necessary to distil the ethanol-containing liquor obtained by fermentation of a sugar or other carbohydrate source, e.g. a malt liquor. In production of whisky such distillation is traditionally effected in batch mode using a series of copper stills and condensers. In the course of the distillation process there occurs some corrosion of the metal of the still itself, principally at the neck of the still where the body of the still narrows at the entrance to the condenser. In addition, after the batch is transferred, any liquid remaining in the condenser will also tend to dissolve copper; this liquid will be carried into the next still when distillation recommences. As a result the lees obtained at the end of each batch distillation has a small but significant copper content. As well as this copper content the lees also has a waxy solids content which tends to deposit upon equipment used for treatment of the lees.

Although the use of stainless steel would solve this problem, stainless steel stills would not be acceptable to most whisky distillers. Similar problems will arise in the distillation of other spirits for consumption, such as gin, which is carried out using stills and/or condensers made from copper.

Current legislation requires that the copper content of the lees resulting from distillation in the production of spirits for consumption must be significantly reduced before it can be discharged to the environment. Whilst it can readily be envisaged that one method of treatment of the spent distillery lees in order to reduce its copper content is to subject it to ion exchange, this does not solve the problem of how to cope with the wax content of the spent distillery lees which will otherwise relatively rapidly foul the ion exchange resin and the equipment used to treat the spent lees .

The present invention accordingly seeks to provide a process for the treatment of copper containing lees from distillery operations carried out using copper stills or condensers which results in production of a treated liquor with a sufficiently low copper content suitable for discharge to the environment without further treatment.

The invention further seeks to provide a process for treatment of distillery lees produced by distillation of malt fermentation liquors for the production of whisky to permit discharge of a treated water stream acceptable for direct discharge to the environment without risk of unacceptable pollution.

A still further aim of the invention is to provide an ion exchange process for the treatment of spent distillery lees resulting from whisky distillation in copper stills or condensers in which the risk of waxy materials present in the spent distillery lees clogging the ion exchange resin is minimised or substantially obviated. According to the present invention there is provided a process for the treatment of distillery lees containing copper values and waxy materials which comprises passing distillery lees containing copper values and waxy materials to a settling zone, retaining the distillery lees in the settling zone for a period of time effective for allowing settlement of waxy solids therefrom, recovering a liquid phase from the settling zone, contacting the liquid phase with a cation exchange resin in a first ion exchange zone having an inlet region and an outlet and containing a charge of a cation exchange resin, the cation exchange resin in the first ion exchange zone being at least partially in the H⁺ form, recovering an intermediate liquor from the first ion exchange zone, contacting the intermediate liquor with a cation exchange resin in a second ion exchange zone, the cation exchange resin in the second ion exchange zone being at least partially in the H⁺ form, recovering a final liquor having a reduced copper content from the second ion exchange zone, and backwashing ion exchange resin of the inlet portion of the first ion exchange zone with a portion of the final liquor to remove waxy materials deposited on the ion exchange resin therefrom.

In the process of the invention the hot distillery lees may enter the settling zone at a temperature in the range of from about 90°C up to the boiling point of the distillery lees .

Typically the copper content of the distillery lees is from about 10 ppm by weight up to about 100 ppm by weight, for example about 25 to about 35 ppm by weight.

Preferably the process is operated so that the intermediate liquor has a copper content of less than about 5 ppm by weight, preferably less than about 1 ppm by weight, and even more preferably in the range of from about 0.2 to about 0.5 ppm by weight. In this case the final liquor may have a copper content of less than about 0.1 ppm by weight . In a preferred process according to the invention the ion exchange resin of the first ion exchange zone comprises a gel polystyrene sulphonate resin with divinylbenzene cross- linking. The first and second ion exchange zones conveniently comprise respective first and second ion exchange columns connected in series, the feed to each of the first and second ion exchange columns being to the top of the column in each case, and the treated liquid being recovered from a bottom part of the column after passage through the respective charge of ion exchange resin therein.

The ion exchange resin in an upper portion of the first ion exchange column can be backwashed periodically, for example after treatment of each batch, by fluidisation using recycled final liquor. The final liquor used for fluidisation of the ion exchange resin of the upper portion of the first ion exchange column can be introduced through an interface distributor disposed below the upper portion. Although such a distributor can be fitted with orifices of the type usually used in ion exchange plants, which are typically designed to give a small pressure drop, e.g. of the order from about 0.1 bar to about 0.3 bar, it is preferred to fit the distributor with high energy spray nozzles designed to produce a pressure drop of at least about 1 bar up to about 10 bar or more, e.g. in the range of from about 2 bar to about 5 bar. Such high energy spray nozzles are preferably designed to produce a hollow cone pattern with a large angle of spray of from about 60° to about 120°, e.g. about 90°.

After a period of time in use the ion exchange resin of the first ion exchange zone becomes loaded with copper values . The copper loaded ion exchange resin can then be regenerated by treatment with a solution containing a mineral acid, such as sulphuric acid, followed by electrolysis of the resulting copper containing solution to yield metallic copper and a regenerated mineral acid, e.g. sulphuric acid, solution. In such a procedure the copper loaded ion exchange resin can be subjected to a detergent wash prior to regeneration with sulphuric acid or other mineral acid.

There is produced as a result of regeneration of the copper loaded ion exchange resin with a mineral acid, such as sulphuric acid, an initial copper rich acid solution and a subsequent copper lean acid solution. The copper rich acid solution can be subjected to electrolysis, while the copper lean acid solution can be reserved for use in regeneration of a subsequent charge of copper loaded ion exchange resin. In order that the invention may be clearly understood and readily carried into effect a preferred process in accordance with the invention, and a plant in which such a process can be operated, will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a flow diagram of a plant for treatment of spent distillery lees;

Figure 2 is a partly cut away perspective view of one of the ion exchange columns of the plant of Figure 1 showing a preferred nozzle arrangement for use in back washing of the resin;

Figure 3 is a horizontal section, viewed from above, of the ion exchange column of Figure 2 ; and

Figure 4 is a side view, on an enlarged scale, of one of the nozzles shown in Figures 2 and 3.

Referring to Figure 1 of the drawings, a charge of spent distillery lees is discharged via line 1 from a whisky still (not shown) made of copper into a spent lees holding tank 2. The temperature of the spent lees is approximately the same temperature as the bottom temperature of the still at the end of the batch distillation process, typically at least about 90°C up to about 100°C. Its copper content is approximately 30 ppm w/v. Flow sensor 3 monitors the flow of the spent lees into spent lees holding tank 2. A level sensor 4 is used to ensure that the spent lees holding tank 2 does not get inadvertently overfilled.

The spent distillery lees is allowed to settle in tank 2 for at least 1 hour and to cool. Waxy solids settle out and can be removed by way of valve 5 and drain conduit 6 into a waste solids collection zone 7.

Tank 2 is provided with an underflow weir 8. Clarified liquor is withdrawn from tank 2 by way of line 9 using pump 10. The liquor flows on in line 11 to one or other of a pair of ion exchange resin columns 12 and 13 , each containing a charge of a cation exchange resin.

At start up of the plant each of ion exchange columns 12 and 13 contains a respective charge of cation exchange resin which is in the H⁺ form. In the course of treatment of the lees the cation exchange resin is gradually converted into the Cu⁺⁺ form. Conveniently each of columns 12 and 13 contains sufficient resin to treat about 8 batches of spent lees from the whisky still before the resin is wholly converted to the Cu⁺⁺ form. A suitable cation exchange resin is Purolite ClOO resin manufactured by Purolite International Ltd., Hounslow, Middlesex, U.K. ("Purolite" is a Trade Mark).

Normally the ion exchange columns 12 and 13 are connected in series. As will be described further below, either of the ion exchange columns 12 and 13 can be used as the "lead" column while the other one is used as the "lag" column .

When column 12 is used as the "lead" column, flow to column 12 is controlled by valve 14 in line 15, which is connected to lines 16 and 17. Line 17 discharges into the top of column 12. The copper-containing liquor flows down through an upper portion 18 of the bed of ion exchange resin and then through a lower portion 19 of the bed of ion exchange resin. If desired, a perforated screen can be used to separate the portions 18 and 19; however, no screen is usually needed. The liquor, which has had at least a major part of its copper content removed, exits column 12 from its bottom end by way of line 20 and flows on through line 21, valve 22, and lines 23 and 24 into the top end of column 13. Typically the copper content of the liquor at this stage is less than 1 ppm by weight. It then flows down through a top portion 25 of the charge of resin in column 13 and then through a lower portion 26 of the charge before exiting the column 13 from near its bottom by way of line 27. The treated lees at this stage typically has a copper content of less than 0.1 ppm by weight . The treated lees then flows on in lines 28 and 29 and through valve 30 to line 31, from which it can be discharged to the environment in line 32 or, as necessary, passed by way of line 33 to treated lees holding tank 34.

When the charge of ion exchange resin in column 12 is exhausted through treatment of a predetermined number of batches of spent lees, column 12 is taken out of service and its charge of resin is regenerated. Regeneration of the charge of resin can be effected on site or, more preferably, the column with its charge of copper loaded ion exchange resin can be transported to a central site for regeneration; alternatively the charge of copper loaded resin can be discharged as a slurry into a transportable tank, which may be large enough to hold one or more charges of resin, for conveyance to the central regeneration site.

By suitable manipulation of the appropriate valves, as is described further below, column 13 can then be made to become the "lead" column, while a further column (not shown) is connected to the plant as the new "lag" column in place of the column 12.

Flow of spent lees from line 11 to column 13, when this is the "lead" column, can occur by way of line 35, through valve 36, and then through lines 37, 38 and 24. Valves 14 and 22 are closed in this flow mode of the plant. In addition valve 30 is closed so that the treated lees in line 28 can flow instead through line 39, valve 40, and line 41 to line 16. The treated lees from the lag column (which now corresponds to column 12) exits therefrom by way of lines 20 and 21, from which it then passes into line 42, through valve 43, and line 44 into line 31 (for discharge) or line 33 (for flow into holding tank 34) .

Because the spent lees from holding tank 2 contains waxy materials, the charge of ion exchange resin in the "lead" column 12 or 13 tends to become clogged in use. It is accordingly desirable to back wash the charge of ion exchange resin in the "lead" column 12 or 13. It is, however, undesirable to backwash the entire charge of resin in the "lead" column 12 or 13 because this results in disturbing the packing of the resin and leading to a danger of resin with high copper levels becoming positioned near the exit to the column 12 or 13. As a result, the liquid may not undergo proper treatment after backwashing because of high copper leakage. It has been found that, in practice, it is only necessary to backwash the top portion of the resin charge in the "lead" column 12 or 13 in order to minimise fouling of the resin by the residual waxy solids in the spent lees in line 11.

It is also desirable to carry out backwashing of the resin with water that is substantially free from calcium and magnesium ions . Accordingly it is convenient to use the treated lees from holding tank 34 for this purpose.

During backwashing of column 12 , when it has been the "lead" column, treated lees is withdrawn from holding tank 34 through line 45 by means of pump 46 which delivers it through non-return valve 47 and valve 48 to lines 49 and 50 and then through line 51 and valve 52 to line 53. As can be seen from Figure 1, line 53 ends near the bottom of upper portion 18 of the resin charge in column 12 at an interface distributor (not shown in Figure 1) fitted with nozzles (also not shown in Figure 1) . These nozzles can be of a type conventionally used in water distributor systems in ion exchange plants . Such nozzles are typically designed to produce a small pressure drop, for example in the range of from about 0.1 bar to about 0.3 bar, across the orifices in order to produce uniformity of flow. The overall flow produced using such an orifice is essentially laminar. The use of such nozzles can be used to good effect in the backwashing step, during which only top portion 18 is fluidised. By using an interface distributor, as discussed above, in column 12 the lower portion 19 of the charge of resin remains packed, thus ensuring that the quality of the treated lees is maintained. During this step valves 14, 41, and 43 are kept shut, while a valve 54 in line 55 is open, thus permitting the liquor used for backwashing to flow through line 56 into spent lees holding tank 2.

Figures 2 and 3 illustrate an ion exchange column (e.g. column 12) of the plant of Figure 1 which is fitted with a type of nozzle whose use is preferred in the plant and process of the present invention. Such nozzles 101 are high energy spray nozzles having a pressure drop of at least about 1 bar, for example a pressure drop from about 2 bar to about 5 bar. Each nozzle 101 is mounted at the end of a respective arm 102 of a distributor at the bottom end of line 53. The nozzles 101 point upwards and produce a highly turbulent localised flow within the resin bed during the backwashing step which scours the resin of solids but without increasing the overall liquid flow rate from that typically used with conventional backwashing nozzles. When using such high energy spray nozzles 101 the agitation is confined to a zone less than 300 mm from the nozzles. As a result the risk of resin being carried over from the top of column 12 is minimised. One such high energy spray nozzle 101 is that sold as nozzle code ASU/ATU 1780xx by PNR-UK Ltd. of Bromsgrove, Worcester, United Kingdom. It is of open construction and produces a hollow cone pattern (indicated at 103 in Figure 4) with a large angle of spray (90°) . Other nozzles giving a different pattern of spray could be used, depending upon the dimensions of column 12.

When the resin of top portion 25 in column 13 is to be backwashed, valves 52 and 54 are closed. Instead treated lees flows from line 49 through line 57, valve 58 and line 59 into column 13. Line 59 extends only part way down inside column 13 to the bottom of top portion 25 of the charge of resin in column 13. The liquid used for backwashing exits column 13 in line 24 and passes to spent less holding tank 2 by way of line 38 through valve 60 into line 61 which is in turn connected to line 56.

The plant also includes line 62, valve 63 and line 64 for cooling of column 12 with treated lees from tank 34 prior to column handling at changeover. It also includes line 65, valve 66 and line 67 which are provided for a similar purpose for cooling of column 13.

In typical operation of the plant the conditions of the valves is as set out in the Table.

TABLE

Regeneration of the copper loaded resin conveniently comprises a detergent wash step followed by acid regeneration. The resulting copper containing sulphuric acid solution can then be subjected to electrolysis in order to recover copper therefrom by electrowinning and produce further sulphuric acid which can be used as obtained, without further purification, to regenerate a subsequent batch of copper loaded ion exchange resin.

The first step of resin treatment is to carry out a wash/backwash of the entire resin charge in the column with a warm detergent solution in order to assist further in the removal of any solids that have accumulate within the column. A suitable detergent is one containing a mixture of anionic and non- ionic surfactants. Following the detergent wash the resins are flushed with softened water prior to the regeneration step. During this rinse stage it is possible to monitor the extent of fouling by waxy materials that has occurred by checking the pressure drop across the column at a predetermined flow. If an excessive pressure drop is detected, then it may be desirable to discard the resin of the upper portion of the existing charge of resin, or the entire charge of resin, and replace it with fresh ion exchange resin.

Acid regeneration of the resin is preferably carried out in two steps. For the first stage of regeneration a predetermined amount of 15% sulphuric acid is fed to the base of the column in an upflow countercurrent mode and also to the top of the column in a downflow co-current mode. This procedure keeps the resin in the bottom of the column packed and countercurrent regeneration ensures that the resin produces low copper levels in service. The interface distributor enables withdrawal of the acid copper sulphate solution from the column. In the initial part of the regeneration step an acid copper sulphate solution (or "high copper/low acid" solution) is produced. However, towards the end of the regeneration stage the copper content drops and a solution containing mainly acid with little copper in it (or a "low copper/high acid" solution) is formed. The "high copper/low acid" solution is fed to an electrolysis cell for recovery of metallic copper and regeneration of a sulphuric acid solution. The "low copper/high acid" solution is reserved for use in regeneration of a subsequent column. This "low copper/high acid" solution can be used during the latter part of the regeneration of such a subsequent column, while recovered acid containing up to about 200 ppm of copper by weight can be used in the initial part of the regeneration step .

The regenerated resin in the column is given a final softened water wash prior to return to service again. Waste water can be directed to a bio-treatment plant prior to discharge to the environment.

The spent lees solids from tank 7 and recovered during regeneration contain typically about 30% copper w/v.

Claims

CLAIMS :

1. A process for the treatment of distillery lees containing copper values and waxy solids materials which comprises passing distillery lees containing copper values and waxy materials to a settling zone, retaining the distillery lees in the settling zone for a period of time effective for allowing settlement of waxy solids therefrom, recovering a liquid phase from the settling zone, contacting the liquid phase with a cation exchange resin in a first ion exchange zone having an inlet region and an outlet and containing a charge of a cation exchange resin, the cation exchange resin in the first ion exchange zone being at least partially in the H⁺ form, recovering an intermediate liquor from the first ion exchange zone, contacting the intermediate liquor with a cation exchange resin in a second ion exchange zone, the cation exchange resin in the second ion exchange zone being at least partially in the H⁺ form, recovering a final liquor having a reduced copper content from the second ion exchange zone, and backwashing ion exchange resin of the inlet portion of the first ion exchange zone with a portion of the final liquor to remove waxy solids materials deposited on the ion exchange resin therefrom.

2. A process according to claim 1, in which the hot distillery lees enters the settling zone at a temperature in the range of from about 90┬░C up to the boiling point of the distillery lees.

3. A process according to claim 1 or claim 2, in which the copper content of the distillery lees is from about 10 ppm by weight up to about 50 ppm by weight.

4. A process according to any one of claims 1 to 3 , in which the copper content of the distillery lees is from about

25 up to about 35 ppm by weight.

5. A process according to any one of claims 1 to 4 , in which the intermediate liquor has a copper content of less than about 5 ppm by weight .

6. A process according to any one of claims 1 to 5, in which the final liquor has a copper content of less than about 0.1 ppm by weight.

7. A process according to any one of claims 1 to 6, in which the ion exchange resin of the first ion exchange zone comprises a gel polystyrene sulphonate resin with divinylbenzene cross -linking.

8. A process according to any one of claims 1 to 6 , in which the first and second ion exchange zones comprise respective first and second ion exchange columns connected in series, in which the feed to each of the first and second ion exchange columns is to the top of the column in each case, and in which the treated liquid is recovered from a bottom part of the column after passage through the respective charge of ion exchange resin therein.

9. A process according to claim 8, in which the ion exchange resin in an upper portion of the first ion exchange column is backwashed periodically by fluidisation in recycled final liquor and in which final liquor used for fluidisation of the ion exchange resin of the upper portion of the first ion exchange column is introduced through an interface distributor disposed below the upper portion.

10. A process according to claim 9, in which the final liquor used for fluidisation during the backwashing step is introduced into the upper portion of the ion exchange resin of the first ion exchange column through one or more high energy spray nozzles with a pressure drop of from about 2 bar to about 5 bar.

11. A process according to claim 10, in which the high energy spray nozzle or nozzles is or are designed to produce a hollow cone pattern with an angle of spray of from about 60┬░ to about 120┬░.

12. A process according to any one of claims 1 to 11, in which after a period of time in use the ion exchange resin of the first ion exchange zone becomes loaded with copper values and in which the copper loaded ion exchange resin is regenerated by treatment with a solution containing sulphuric acid, followed by electrolysis of the resulting copper containing solution to yield metallic copper and a regenerated sulphuric acid solution.

13. A process according to claim 12, in which the copper loaded ion exchange resin is subjected to a detergent wash prior to regeneration with sulphuric acid.

14. A process according to claim 12 or claim 13, in which there is produced as a result of regeneration of the copper loaded ion exchange resin with sulphuric acid an initial copper rich acid solution and a subsequent copper lean acid solution, in which the copper rich acid solution is subjected to electrolysis, and in which the copper lean acid solution is reserved for use in regeneration of a subsequent charge of copper loaded ion exchange resin.