Liquid purification or separation – Processes – Chromatography
Reexamination Certificate
1999-02-10
2001-05-01
Therkorn, Ernest G. (Department: 1723)
Liquid purification or separation
Processes
Chromatography
C210S198200, C127S046200
Reexamination Certificate
active
06224776
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for fractionating a solution into two or more fractions enriched with different components. In particular, the present invention relates to a method for fractionating a solution by a chromatographic simulated moving bed (SMB) process in which the liquid flow is effected in a chromatographic system comprising one or more columns containing one or more partial packed beds. The dissolved substances present in the feedstock are separated in the partial packed beds, and a separation (i.e. dry solids) profile is formed. The columns/partial packed beds of the chromatographic system form one or more loops. The novel separation system of the present invention comprises at least two separation profiles in the same loop. A separation profile is formed by the feed solution and the dry substance recirculated. The separation profile is a complete or an essentially complete dry solids profile.
In accordance with the method of the present invention, two or more profiles of dissolved material (dry solids profiles) are moving in the entire resin bed (all columns in the loop). This is different from prior art SMB methods wherein only one profile moves through the loop of the chromatographic system at any one time.
The chromatographic SMB method of the present invention enables a more efficient use of the resin, resulting in higher capacity at a given product recovery, purity and resin volume or alternatively, higher product purity is achieved at the same capacity as in prior processes.
Fractionation of a solution comprising many dissolved substances into fractions enriched with different components is often necessary in order to recover the desired components optimally pure. The method of the present invention can be employed to carry out such fractionation. A sulphite cooking liquor, for instance, can be fractionated by the present method so as to give a fraction rich in monosaccharides and/or a fraction rich in lignosulphonates. Furthermore, molasses or vinasse can be fractionated in this way to obtain fractions rich in a sugar, such as sucrose, and/or betaine, for instance.
The method of the present invention is particularly well suitable for separating substances that are difficult to separate from mixtures containing them. Such mixtures include fructose/glucose syrups, beet-derived juices, invert sugar mixtures, starch hydrolysates, wood hydrolysates, milk whey solutions and other lactose-containing solutions, solutions containing amino acids, fermentation broths containing various organic acids, such as citric acid, bagasse hydrolysates, and particularly solutions containing inositol, mannitol, sorbitol, xylitol, erythritol, glutamic acid and/or glycerol.
BACKGROUND OF THE INVENTION
Continuously operated chromatographic separation processes presently commonly employ the simulated moving bed method, which is used in a variety of different applications. The simulated moving bed method may be sequential or continuous or comprise a combination of a continuous and a sequential method.
In a continuous simulated moving bed process, all fluid streams typically flow continuously. The streams are: the supply of feed solution and eluent, the circulating of the liquid mixture, and the withdrawal of products. The flow rate for these flows may be adjusted in accordance with the separation goals (yield, purity, capacity). Normally 8 to 20 partial packed beds are combined into a loop. The eluent and feed supply and product withdrawal points are shifted cyclically in the downstream direction in the packing material bed. On account of the supply of eluent and feed solution, the withdrawal of products, and the flow through the packing material bed, a dry solids profile is formed in the packing material bed. Constituents having a lower migration rate in the packed bed are concentrated in the back slope of the separation profile, i.e. dry solids profile, while constituents having a higher migration rate are concentrated in the front slope. The points of introduction of the feed solution and eluent and the withdrawal points of the product or products are shifted cyclically at substantially the same rate at which the dry solids profile moves in the packing material bed. The eluent and feed supply and product withdrawal points are shifted cyclically by using feed and product valves located along the packing material bed, typically at the upstream and downstream end of each partial packed bed. If product fractions of very high purity are desired, short cycle times and multiple partial packed beds must be employed (the apparatus has the requisite valves and feed and withdrawal equipment).
In the sequential simulated moving bed process, some of the fluid streams do not flow continuously. The streams are: the supply of feed solution and eluent, the circulating of the liquid mixture, and the withdrawal of products (eluting phase; two to four or more products). The flow rate and the volumes of the different feeds and product fractions may be adjusted in accordance with the separation goals (yield, purity, capacity). The process commonly comprises three basic phases: feeding, elution and circulation. During the feeding phase, a feed solution, and possibly also an eluent during a simultaneous eluting phase, is introduced into predetermined partial packed beds, and simultaneously a product fraction or fractions are withdrawn. During the eluting phase, eluent is introduced into a predetermined partial packed bed or predetermined partial packed beds, and during these phases two, three or even four product fractions are withdrawn. During the circulating phase, no feed solution or eluent is supplied to the partial packed beds and no products are withdrawn.
The continuous simulated moving bed process has been disclosed in U.S. Pat. No. 2,985,589 (Broughton, et al.), for example. In accordance with this process, the mixture to be fractionated is introduced into one partial packed bed and eluent is introduced into another partial packed bed, and two product fractions are withdrawn substantially simultaneously. There are at least four partial packed beds, forming a single loop with continuous circulation, and the feed and product withdrawal points are shifted cyclically in the downstream direction in the packing material bed. A similar method is described in U.S. Pat. No. 4,412,866 (Schoenrock, et al.).
Sequential simulated moving bed processes are described in British application 2 240 053 and U.S. Pat. No. 4,332,623 (Ando, et al.); U.S. Pat. No. 4,379,751 (Yoritomi, et al.) and U.S. Pat. No. 4,970,002 (Ando et al.), for instance. A sequential simulated moving bed process applied to the recovery of betaine and sucrose from beet molasses is described in Applicants' Finnish Patent 86 416 (U.S. Pat. No. 5,127,957). In these methods, only one complete or essentially complete dry solids profile is circulated in the partial packing material loop.
Also, Applicants' copending Finnish applications 930 321 (filing date Jan. 26, 1993) and 932 108 (filing date May 19, 1993) relate to a sequential simulated moving bed method, the first applied to the fractionation of molasses and the latter to the fractionation of sulphite cooking liquor. As is described in these applications, the simulated moving bed method may include multiple loops; yet a single dry solids profile is circulated in each loop.
Finnish Patent 86 416 (U.S. Pat. No. 5,127,957) referred to above discloses a method for recovering betaine and sucrose from beet molasses employing a sequential simulated moving bed process. The chromatographic system comprises at least 3 chromatographic partial packed beds in series. In the method, betaine and sucrose are separated during the same sequence comprising a molasses feeding phase wherein the molasses feedstock is supplied to one of said partial packed beds and eluent water is supplied substantially simultaneously to another of said partial packed beds, an eluent feeding phase, and a circulating phase. These steps are repeated either once or several times during t
Heikkila Heikki
Hyoky Goran
Kuisma Jarmo
Paananen Hannu
Cultor Corporation
Scully Scott Murphy & Presser
Therkorn Ernest G.
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