ZA200800129B - Sugar treatment process - Google Patents

Description

® | ? . \ LIN # 2007/0915,

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THIS INVENTION relates to a sugar treatment process.

The Applicant is aware of a process that is capable of producing high quality : cane sugar directly from raw cane juice, by subjecting the raw cane juice to membrane filtration, refrigeration, ion exchange demineralization and decolourization, and crystallization. A sugar treatment plant embodying such : a process can thus be located at a cane sugar mill site. However, cane sugar mills normally operate seasonally, being dependent on a supply of cane which is thus only available during the cane growing season. There is thus insufficient raw cane juice feedstock for the sugar treatment plant to operate continuously throughout the year. It is thus an object of this invention to provide a means whereby this problem can at least be alleviated.

Thus, according to the invention, there is provided a sugar treatment process, which comprises | : blending sugar cane derived sugar syrup with clarified sugar cane derived sugar juice and/or ion exchange sweet water, to obtain a sugar juice feedstock; : - subjecting this sugar juice feedstock to membrane filtration; passing the resultant filtered sugar juice through at least one ion . exchange stage in which it is sequentially brought into contact with a strong acid cation ion exchange resin in the hydrogen form and thereafter with an “anion ion exchange resin in the hydroxide form, to obtain a purified sugar solution; concentrating the purified sugar solution, to produce a syrup; and recovering sugar products from the syrup. : C:AMSWord\MyDocuments\specs\Tongaat-SugarMilling-CS\Eil 04/01/2008 : :

A cane sugar mill produces raw sugar cane derived sugar syrup which can be subjected to crystallization to produce raw sugar and partially exhausted syrup, such as A molasses, ie the supernatant liquid resulting from the first crystallization of a sugar syrup. Raw syrup and/or the raw sugar and partially exhausted syrup can thus be stockpiled or stored during the cane growing - : season, so that a supply thereof is available for use as feedstock to the process of the invention throughout the year. Co " The sugar syrup used in the process of the invention will thus comprise raw syrup and/or partially exhausted syrup, as hereinbefore described. A supply of raw sugar may also be available, especially when partially exhausted syrup or molasses is stockpiled for use in the process, and the process may thus include treating raw sugar as well, as hereinafter described.

The sugar syrup is thus blended with sufficient of the clarified sugar cane derived sugar juice and/or ion exchange sweet water, so that the sugar juice feedstock has a desired sugar concentration, eg about 25 Brix.

The sugar syrup may thus in particular be stored sugar syrup as hereinbefore described. The invention thus provides a means for running the process, . which will typically be carried out in a sugar treatment plant located at the site of a cane sugar mill, during periods when there is a reduced supply of clarified sugar cane derived sugar juice (hereinafter also referred to as ‘a clear juice’), or even when no clear juice is available, in which case the ion exchange . 25 sweet water is used as blending liquid for the sugar juice. Such periods’ of reduced or no clear juice supply typically occur out of season, when sugar mills are not operational, or when sugar mills are subjected to maintenance shutdowns. The sugar syrup has a high sugar concentration, ie a high Brix, and is hence stable, so that it can readily be stored during season, eg in large storage tanks, until required for use during the off season.

If necessary, ie if the supply of clear juice and ion exchange sweet water is insufficient, then additional water can be used to dilute the sugar syrup. Such : C:\MSWord\MyDocuments\specs\Tongaat-SugarMilling-CS\Ell 04/01/2008 . :

° . =» 2007700129 dilution will typically be effected in a dilution stage, which may follow an optional sugar syrup clarification stage.

The clarified sugar cane derived sugar juice or clear juice may be obtained by preparing sugar cane stalks, eg disintegrating or breaking up the stalks; removing sugar juice from the prepared stalks by diffusion and/or milling, using imbibition water, thereby to obtain mixed juice; heating and liming the mixed juice; and subjecting the mixed juice to primary clarification, to obtain the clear juice. :

The membrane filtration of the sugar juice feedstock may be effected in a filtration stage. In the filtration stage, sufficient suspended solids, organic non-sugar impurities and colour are removed to render the sugar juice amenable to subsequent treatment in the ion exchange stage. The sugar juice may typically be passed through a membrane in the size range 200

Angstrom to 0.1 micron. This thus constitutes ultrafiltration of the sugar juice.

The Applicant has found that ultrafiltration prior to ion exchange is important in order to inhibit rapid fouling of the ion exchange resins, and to ensure that the resultant sugar products meet required turbidity specifications.

If necessary, the sugar juice feedstock can be evaporated to obtain a desired sugar concentration, before subjecting it to the membrane filtration. This may particularly be applicable during periods when the supply of clear juice is plentiful. The clear juice as obtained from sugar cane stalks as herein before described, has a low sugar or sucrose concentration, typically less than 15% : (m/m), for example in the order of 10% to 15% (m/m). The sugar juice feedstock may thus have a low sugar concentration even though sugar syrup : is blended with the clear juice, eg if the feedstock contains a high proportion of sugar juice. Thus, the sugar juice feedstock may be concentrated to a sugar or sucrose concentration of at least 20% (m/m), preferably from 20% to 40% (m/m) typically about 25% (m/m), ie 25 Brix. Such evaporation will thus be : effected in a primary evaporation stage. : C:\MSWord\MyDocuments\specs\Tongaat-SugarMilling-CS\Eil 04/01/2008 : :

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The clear juice is typically at an elevated temperature, eg at a temperature above 90°C. Thus, the membrane filtration will also typically be affected at elevated temperature; however, since ion exchange normally takes place at lower temperatures, eg at a temperature below 60°C, such as at about 10°C, the juice will normally be cooled down, eg by means of refrigeration, before it is subjected to ion exchange.

Low feedstock temperatures are also required during ion exchange to inhibit sucrose inversion to fructose and glucose, which can be catalyzed by strong acid cation resins. Thus, the filtered sugar juice will in any event be cooled to below 25°C if no inversion from sucrose to fructose and glucose is required.

Should inversion be required, the degree of sugar inversion can be controlled by adjusting the temperature of the sugar juice before it enters the ion exchange stage. Thus, by reducing the sugar juice temperature to about 10°C, minimal sucrose inversion to fructose and glucose will take place in the ion exchange stages.

In the ion exchange stage, deashing or demineralization and further colour removal takes place. ) © 20

The ion exchange stage may comprise a simulated moving bed arrangement or system, eg it may comprise a continuous fluid-solid contacting apparatus such as that described in US 5,676,826 (Rossiter); a separation train system such as that described in WO 2004/029490 (Jensen); or the like.

The process may include subjecting the filtered sugar juice to a first pass : through the ion exchange stage, to obtain a partially purified sugar solution, and thereafter subjecting the partially purified sugar solution to at least one further pass through the ion exchange stage, to obtain the purified sugar solution. : The process includes regenerating the resins from time to time, as required.

Thus, the strong acid cation resin may be regenerated by contacting it with a strong acid, such as hydrochloric acid or nitric acid, with an acid stream rich in potassium salts thereby being obtained. This component is suitable for use as a

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®o 5 wt2007/00129 fertilizer feedstock. The anion resin may be regenerated by contacting it with a strong or weak base such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, or a combination of sodium or potassium hydroxide and ammonium hydroxide, with an alkaline stream which is rich in nitrogen being obtained. This component is also suitable for use as a fertilizer feedstock.

The resins may be sweetened off. The process may thus include washing out the residual sugar solutions with wash water after the resin capacity has been reached. Instead, the resins may be sweetened on. The process may thus include first adding sugar solution thereby displacing the water present after regeneration. The spent wash water then constitutes the ion exchange sweet water, which can be used to effect dilution of the stored sugar syrup, as hereinbefore described.

As indicated hereinbefore, deashing or demineralization (cations and anions) and colour removal are effected simultaneously in the ion exchange stage. : However, the Applicant has found that it is not always the most efficient route to remove all colour during passage of the sugar juice through the ion exchange stage. Some colour may thus, if desired, be removed in the ion exchange stage, with the remaining colour then being removed by further treatment of the sugar juice.

Thus, in one embodiment of the invention, the process may include subjecting the purified sugar solution from the ion exchange stage, or the partially purified sugar solution of the ion exchange stage, to further decolourizing in a decolourizing stage.

The decolourizing stage may comprise an anion resin, in particular an anion resin in hydroxide or chloride form; an absorption resin; activated carbon; or another absorption medium.

When the decolourizing stage includes an anion resin in the chloride form, the partially purified sugar solution, after the first pass thereof through the ion exchange stage, may be brought into contact with the anion resin in the chloride

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® 7 form in the further ion exchange stage, and thereafter subjected to a second pass through the ion exchange stage.

When the decolourizing stage includes an anion resin in the hydroxide form, an absorption resin, activated carbon, or another absorption medium, the purified sugar solution from the ion exchange stage may be brought into contact with the anion resin, the absorption resin, the activated carbon or the other absorption medium.

The concentration of the purified sugar solution into the syrup may be effected by means of evaporation. The resultant syrup may have a sucrose or sugar concentration of about 65% (m/m).

The recovery of the sugar products from the syrup or concentrated juice may include treating the syrup to recover therefrom liquid sugar products and/or solid or crystal sugar products. Crystallization may thus be effected. Primary crystallization may be effected in at least one primary crystallization stage, to produce refined white sugar and primary mother liquor or molasses, while secondary crystallization of the- primary mother liquor may be effected in at least one secondary crystallization stage, to produce impure crystallized sugar and secondary mother liquor or white strap molasses.

The primary crystallization may be effected in a plurality of sequential primary stages or boilings. The secondary crystallization may also be effected in a plurality of sequential primary stages or boilings. The purge or mother liquor from the primary crystallization is thus exhausted further by the secondary crystallization to recover the impure sugar crystals. The impure crystallized sugar from all the secondary crystallization stages or boilings may be remelted or redissolved, and recycled to the syrup ahead of the primary crystallization stages. This recycle is typically less than 20% of the total feed to the primary crystallization stages. The purge or mother liquor from the secondary or exhaustion crystallization stages is thus defined as the white strap molasses.

In another embodiment of the invention, the process may include subjecting the syrup, prior to the primary crystallization, to decolourizing crystallization in a

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® 8 decolourizing crystallization stage, to produce high colour white sugar and tertiary mother liquor or molasses; remelting or redissolving the high colour white sugar to produce a remelted sugar solution which is then subjected to the primary crystallization in the primary crystallization stages; retumning the primary mother liquor or molasses to the decolourizing crystallization stages: subjecting the tertiary mother liquor or molasses to mill crystallization in a mill crystallization stage to produce the white strap molasses and impure crystallized low colour sugar; and returning the impure crystallized low colour sugar to the decolourizing crystallization stage, with the decolouring crystallization and the crystallization constituting the secondary crystallization.

In a particular embodiment of the invention, the filtered sugar juice is passed through a primary ion exchange stage in which the sugar juice is sequentially brought into contact with the at least one strong acid cation ion exchange resin in the hydrogen form and thereafter with at least one weak base anion ion exchange resin in the hydroxide form, to effect primary demineralization of the sugar juice; and thereafter passing the sugar juice through a secondary ion exchange stage in which the sugar juice is sequentially brought into contact with at least one strong base anion ion exchange resin in the hydroxide form and thereafter with at least one acid cation ion exchange resin, to effect secondary demineralization of the sugar juice, thereby to obtain the purified sugar solution. The primary and secondary ion exchange stages may then be the same or similar to those described in ZA 2006/09300 which is hence incorporated herein by reference.

The process may include adding raw sugar, such as filtered Dissolved Raw

Sugar (melt) to the ion exchange stage. The raw sugar quality will determine if the melt is added to the demineralization stage or the decolourization stage.

The raw sugar may in particular be stored raw sugar, as hereinbefore described. The use of such stored raw sugar will also permit the process to run the whole year round including periods when a sugar mill providing the clear juice, is non-operational, eg out of season or during maintenance periods, as hereinbefore described.

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The process may include treating the retentate produced in the ultrafiltration stage. This treatment may include concentrating and clarifying the retentate ) to produce clarified retentate and retentate scum. The process may then include recycling the clarified retentate to the primary evaporation stage.

The invention will now be described in more detail with reference to the accompanying diagrammatic drawing which shows, in simplified flow diagram form, a sugar treatment process according to the invention.

In the drawing, reference numeral 10 generally indicates a sugar treatment . process according to the invention. | }

The process 10 includes an optional flotation/clarification stage 12 with a stored syrup line 14 leading into the stage 12. A dilution water line 16 leads : into a dilution stage 13, which is connected to the clarification stage 12 by a flow line 15.

A clear juice line 22 leads into a primary evaporation stage 20. A sugar juice line 24 leads from the stage 20 to an ultrafiltration stage 26. A transfer line 18 leads from the dilution stage 13 to the ultrafiltration stage 26.

A permeate line 28 leads from the ultrafiltration stage 26 to a refrigeration stage 30, with a chilled permeate flow line 32 leading from the stage 30 to a demineralization ion exchange stage 34.

A wash water line 36 leads into the ion exchange stage 34 while an ion exchange sweet water withdrawal line 38 leads from the stage 34 to the ’ dilution stage 13.

A deashed juice line 40 leads from the stage 34 to a decolourization ion exchange stage 42. A filtered raw sugar melt addition line 44 leads into the stage 42 or optionally the stage 34 depending on the raw sugar quality used.

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® 10

A white juice withdrawal line 46 leads from the stage 42 to a secondary evaporation stage 48. A white syrup withdrawal line 50 leads from the secondary evaporation stage 48 to a crystallization stage 52. A white sugar withdrawal line 54 leads from the stage 52, as does a high grade molasses withdrawal line 56.

A retentate withdrawal line 60 leads from the ultrafiltration stage 26 to a : concentration/clarification stage 62. A retentate recycle line 64 leads from the stage 62 to the primary evaporation stage 20. A retentate scum withdrawal line 66 leads from the stage 62.

In use, a plant embodying the process 10 is located at the site of a sugar cane mill (not shown). During the cane growing and harvesting season, the sugar cane mill produces raw syrup and/or partially exhausted syrup, eg A molasses, and raw sugar. A portion of these products is stored for off-season use. Such storage is thus effected in bulk storage tanks (not shown), and storage of these products is possible as a result of their high sugar concentration which permits storage of such products without the products deteriorating or going off spec.

The process 10 operates by continually feeding raw syrup and/or partially exhausted syrup along the line 14 into the stage 12. It will be appreciated : that, during the growing season, the raw syrup and/or partially exhausted syrup can be drawn directly from the sugar mill, however, during the off- season they will be drawn from the bulk storage tanks. The stored raw syrup or stored partially exhausted syrup, eg A molasses, thus enters the flotation clarification stage 12 along the line 14 and, after clarification, is diluted in the dilution stage 13 with water entering along the line 16 or line 38. The resultant sugar solution passes along the line 18 to the ultrafiltration stage 26 where it is mixed with clear juice entering along the line 24. The clear juice is, if necessary, first subjected to evaporation in the stage 20 to produce a sugar juice having a required sugar concentration, preferably about 25 Brix. This sugar juice is then withdrawn along the line 24 and subjected to ultrafiltration in the stage 26 where particles larger than 0.1um are removed.

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The permeate from the ultrafiltration stage 26 passes along the line 28 into the refrigeration stage 30 where it is cooled down, typically from about 90°C to about 10°C.

The chilled permeate passes along the line 32 into the ion exchange stage 34.

The ion exchange stage 34 comprises a simulated moving bed ion exchange arrangement and comprises a continuous fluid solid contacting apparatus, such as that taught in US 5676826, and which simulates a moving bed ion exchange arrangement in which the clarified sugar juice passes sequentially through multiple ion exchange passes. Each ion exchange pass comprises a strong acid cation ion exchange resin in the hydrogen form, followed by anion ion exchange resin in the hydroxide form. Deashed juice from the stage 34 passes, via the line 40, into the stage 42. In the stage 42, the deashed juice is contacted with an anion resin in the hydroxide or chloride form, an absorption resin, activated carbon or another absorption medium, to effect further decolourization of the juice.

White juice is withdrawn from the stage 42 and passes along the line 46 into the secondary evaporation stage 48 where it is evaporated to produce white syrup. The white syrup is transferred, along the line 50, into the crystallization “stage 52. The crystallization stage 52 comprises primary as well as secondary crystallization, with high grade molasses and white sugar being produced and being withdrawn the lines 56 and 54 respectively.

The ultrafiltration stage 26 is similar to the secondary clarification stage 32 of

WO 00/60128, the demineralization ion exchange stage 54 is similar to the simulated moving bed ion exchange stage or system 40 of WO 00/60128, the decolourization ion exchange stage 42 is similar to the decolourization stage 106 of WO 00/60128, the evaporation stage 48 is similar to the evaporation stage 52 of WO 00/60128, and the crystallization stage 52 is similar to the primary crystallization stage 60 and secondary crystallization stage 64 in

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® 12 combination, of WO 00/60128. WO 00/60128 is hence incorporated herein by . reference.

Filtered VHP melt, ie dissolved raw sugar, is added to the decolourization ion exchange stage 42.

When the supply of clear juice, which enters along the line 22, is limited, eg when it is out of season or when a sugar mill producing the clear juice is subjected to shutdown, the plant will operate on stored syrup and or raw sugar. The ion exchange resins in the stage 34 are sweetened on and sweetened off using wash water which enters along the flow line 36. The resultant spent wash water is then ion exchange sweet water, which can be recycled to the dilution stage 13 to provide dilution water for the syrup or to dissolve the incoming raw sugar. If the supply of clear juice and ion exchange sweet water is inadequate, then additional dilution water, entering along the line 16, can be used for dilution of the syrup or molasses in the dilution stage 13. : Ultrafiltration retentate is withdrawn along the line 60 and subjected to concentration and clarification in the stage 62. Retentate scum is withdrawn along the line 66, while clarified retentate is recycled along the line 64, to the primary evaporation stage 20.

The combination of the ultrafiltration stage 20 and the demineralization ion exchange stage 34, when. used to treat clear juice directly or, in this case, when used to treat the combination of clear juice and stored syrup, effectively bridges the gap between sugar cane milling and raw sugar refining, since high quality refined sugar can be produced directly from clear juice and syrup produced from a sugar cane mill. The process 10 is thus effectively a sugar refining process, which has been added to a sugar cane mill. However, in contrast to the seasonal operation of raw sugar cane mills, sugar refineries generally operate all year round. Such all year operation can be achieved with the process 10 by virtue thereof that it uses, as feedstock, stored syrup as well as stored raw sugar. In other words, the operational requirements of a

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® EE 13 raw sugar mill are, by means of the process 10, married to the market requirements associated with white sugar production. With the process 10, white sugar that satisfies stringent quality specifications from a highly variable quality feedstock, can be produced. The process 10 is thus decoupled from raw sugar mill operation through the production and storage of intermediate products that are easily stored and reused at times when the raw sugar mill is non-operational, eg out of season or during mill maintenance periods.

Another feature of the process 10 is the introduction of stored raw sugar, in the form of raw sugar melt, to the decolourization ion exchange 42 or demineralization stage 34. The Brix of the deashed juice entering the stage 42 along the lines 32 or 40 is low (approximately 25 Brix) and can effectively be used to dissolve the raw sugar. This is preferred over water, as the total evaporation load thus remains unchanged. Before entering the stages 34 or 42, the VHP melt is passed through appropriate processes to remove turbidity.

In the concentration/clarification stage 62, ultrafiltration retentate is concentrated by evaporation. This improves the efficiency by which flotation clarification is then employed to remove impurities. The clarified retentate is recycled to the primary evaporation stage 20. The purpose of the flotation clarification is to remove those impurities that will not pass through the ultrafiltration membranes. oo

As hereinbefore described, the stored syrup and molasses may also be subjected to flotation/clarification before being introduced into the process.

This will improve ultrafiltration flux rates, thereby reducing membrane area requirements.

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Claims (29)

@ 1 ER 1AIIE, vui6d CLAIMS | NIT ]

1. A sugar treatment process, which comprises blending sugar cane derived sugar syrup with clarified sugar cane derived sugar juice and/or ion exchange sweet water, to obtain a sugar juice feedstock; subjecting this sugar juice feedstock to membrane filtration; passing the resultant filtered sugar juice through at least one ion exchange stage in which it is sequentially brought into contact with a strong acid cation ion exchange resin in the hydrogen form and thereafter with an anion ion exchange resin in the hydroxide form, to obtain a purified sugar solution; : concentrating the purified sugar solution, to produce a syrup; and recovering sugar products from the syrup.

2. A sugar treatment process according to Claim 1, wherein the sugar syrup comprises raw syrup and/or partially exhausted syrup.

3. A sugar treatment process according to Claim 1 or Claim 2, which includes, in a dilution stage, adding water to the sugar syrup, to dilute it.

4. A sugar treatment process according to any one of Claims 1 to 3 inclusive, wherein the sugar syrup is blended with the clarified sugar cane. derived sugar juice, and wherein the clarified sugar cane derived sugar juice is obtained by preparing sugar cane stalks; removing sugar juice from the prepared stalks by diffusion and/or milling, using imbibition water, thereby to obtain mixed juice; heating and liming the mixed juice; and subjecting the mixed juice to primary clarification, to obtain the clear juice. -

5. A sugar treatment process according to any one of Claims 1 to 4 inclusive, wherein the membrane filtration of the sugar juice feedstock is effected in a filtration stage in which the sugar juice is passed through a C:\MSWord\MyDocuments\specs\Tongaat-SugarMilling-CS\Eil 04/01/2008 membrane in the size range 200 Angstrom to 0.1 micron, thereby subjecting the sugar juice to ultrafiltration. :

6. A sugar treatment process according to any one of Claims 1t0 5 inclusive, wherein the sugar juice feedstock is evaporated to a desired sugar concentration, before subjecting it to the membrane filtration.

: 7. A sugar treatment process according to Claim 6, wherein the sugar juice feedstock is concentrated, by means of the evaporation, to a sugar or sucrose concentration of at least 20% (m/m).

8. A sugar treatment process according to any one of Claims 1to 7 inclusive, wherein the membrane filtration is affected at elevated temperature, and wherein the sugar juice feedstock is then cooled down to below 60°C before it is subjecting to the ion exchange.

9. A sugar treatment process according to any one of Claims 1 to 8 inclusive, which includes adjusting the temperature of the sugar juice before it : enters the ion exchange stage, thereby to control the degree of sugar inversion in the sugar juice.

10. | A sugar treatment process according to any one of Claims 1 to 9 inclusive, wherein the ion exchange stage comprises a simulated moving bed arrangement.

11. A sugar treatment process according to any one of Claims 1 to 10 inclusive, which includes subjecting the filtered sugar juice to a first pass through the ion exchange stage, to obtain a partially purified sugar solution, .and thereafter subjecting the partially purified sugar solution to at least one further pass through the ion exchange stage, to obtain the purified sugar solution.

12. A sugar treatment process according to any one of Claims 1 to 11 inclusive, which includes regenerating the ion exchange resins from time to time, as required. C:\MSWord\MyDocuments\specs\Tongaat-SugarMilling-CS\Eil 04/01/2008

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13. A sugar treatment process according to Claim 12, wherein the strong acid cation resin is regenerated by contacting it with a strong acid, with an acid stream rich in potassium salts thereby being obtained, and wherein the anion resin is regenerated by contacting it with a strong or weak base, with an alkaline stream which is rich in nitrogen being obtained.

14. A sugar treatment process according to Claim 13, wherein the resins are sweetened off by, before regenerating the resins, washing out any residual sugar juice solutions with wash water after the resin capacity has been reached.

15. A sugar treatment process according to Claim 13, wherein the resins are sweetened on by, after regeneration of the resins, adding some purified sugar solution to the resins, thereby displacing the wash water present after regeneration, with the resultant spent sugar solution containing wash water then constituting the ion exchange sweet water.

16. A sugar treatment process according to any one of Claims 1 to 15 - inclusive, wherein only some colour is removed in the ion exchange stage, with the remaining colour then being removed by further treatment of the partially purified sugar solution from the ion exchange stage.

17. A sugar treatment process according to Claim 16, which includes subjecting the partially purified sugar solution of the ion exchange stage, to further decolourizing in a decolourizing stage. -

18. A sugar treatment process according to Claim 17, wherein the decolourizing stage comprises an anion resin; an absorption resin; activated carbon; or another absorption medium.

19. A sugar treatment process according to any one of Claims 1 to 18 inclusive, wherein the concentration of the purified sugar solution into the syrup is effected by means of evaporation. : C:\MSWord\MyDocuments\specs\Tongaat-SugarMilling-CS\Eil 04/01/2008

20. A sugar treatment process according to any one of Claims 1 to 19 inclusive, wherein the recovery of the sugar products from the syrup includes treating the syrup to recover therefrom liquid sugar products and/or solid sugar products. : :

21. A sugar treatment process according to Claim 20, wherein the treatment of the syrup includes subjecting it to crystallization.

22. A sugar treatment process according to Claim 21, wherein the crystallization includes effecting primary crystallization in at least one primary crystallization stage, to produce refined white sugar and primary mother liquor, as well as effecting secondary crystallization of the primary mother liquor in at least one secondary crystallization stage, to produce impure crystallized sugar and secondary mother liquor.

23. A sugar treatment process according to Claim 22, wherein the primary crystallization is effected in a plurality of sequential primary crystallization stages.

24. A sugar treatment process according to Claim 22 or Claim 23, wherein the secondary crystallization is effected in a plurality of sequential primary crystallization stages.

25. A sugar treatment process according to Claim 22, which includes : subjecting the syrup, prior to the primary crystallization, to decolourizing crystallization in a decolourizing crystallization stage, to produce high colour white sugar and tertiary mother liquor; remelting or redissolving the high colour white sugar to produce a remelted sugar solution which is then subjected to the primary crystallization in the primary crystallization stage; returning the primary mother liquor to the decolourizing crystallization stage; subjecting the tertiary mother liquor to mill crystallization in a mill crystallization stage to produce the white strap molasses and impure crystallized low colour sugar; and retumning the impure crystallized low colour sugar to the decolourizing crystallization stage, with the decolouring crystallization and the crystallization constituting the secondary crystallization. C:\MSWord\MyDocuments\specs\Tongaat-SugarMilling-CS\Eil 04/01/2008

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26. A sugar treatment process according to any one of Claims 1 to 25 inclusive, which includes adding raw sugar to the ion exchange stage.

27. A sugar treatment process according to any one of Claims 1to 9 inclusive, wherein the filtered sugar juice is passed through a primary ion exchange stage in which the sugar juice is sequentially brought into contact with the at least one strong acid cation ion exchange resin in the hydrogen oo form and thereafter with at least one weak base anion ion exchange resin in the hydroxide form, to effect primary demineralization of the sugar juice; and thereafter passing the sugar juice through a secondary ion exchange stage in which the sugar juice is sequentially brought into contact with at least one strong base anion ion exchange resin in the hydroxide form and thereafter with at least one acid cation ion exchange resin, to effect secondary demineralization of the sugar juice, thereby to obtain the purified sugar solution.

28. A sugar treatment process according to Claim 27, which includes adding raw sugar to at least one of the ion exchange stages.

29. A sugar treatment process according to any one of Claims 1 to 28 inclusive, substantially as herein described and illustrated. DATED THIS 4™ DAY OF JANUARY 2008. ” 2 2 APA 5 DNS APPLICANTS PATENT AFFORNEYS C:\MSWord\MyDocuments\specs\Tongaat-SugarMilling-CS\Eil 04/01/2008