Liquid purification or separation – Processes – Chromatography
Patent
1996-01-16
1997-06-10
Therkorn, Ernest G.
Liquid purification or separation
Processes
Chromatography
127 462, 162 16, 162 36, 2101982, B01D 1508
Patent
active
056372256
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for the fractionation of sulphite cooking liquor by a chromatographic simulated moving bed system in which the liquid flow is effected in a system comprising at least two chromatographic sectional packing material beds. By the method of the invention, sulphite cooking liquor can be fractionated to yield at least two fractions. The invention is related in particular to fractionation of sulphite cooking liquor into at least three fractions, xylose being concentrated in one of said fractions and lignosulphonates being concentrated in another of said fractions. The invention offers an advantageous method particularly for the recovery of xylose from hardwood sulphite cooking liquor in a continuous process. Typically in this method lignosulphonates are recovered as the most rapidly eluted product fraction, and xylose which is the slowest to elute is recovered as the third product fraction.
By sulphite cooking liquor in this context is meant liquor employed in the cooking of sulphite cellulose, liquor ensuing from the cooking, or a part thereof.
In the method of the invention, the product or products are recovered using a multi-step sequence comprising the following phases: feeding phase of sulphite cooking liquor, eluting phase and recycling phase.
In the feeding phase sulphite cooking liquor is introduced into the sectional packing material bed and simultaneously a corresponding amount of product fraction is withdrawn from a later point downstream in the same sectional packing material bed or from a downstream sectional packing material bed (possibly through one or more other sectional packing material beds) connected in series with said bed. The feeding phase may also include all sectional packing material beds in the system.
In the recycling phase the liquid present in the sectional packing material beds with its dry solids profile is recycled in a loop comprising one, two or several sectional packing material beds; this may also include all sectional packing material beds in the system.
The eluting phase comprises feeding of an eluent into a sectional packing material bed and respectively withdrawal of a product fraction or fractions from a downstream point of the packing material bed, from the same sectional packing material bed or a downstream sectional packing material bed.
A process step comprises one or more of the above simultaneous identical or different phases. A step can consist of, for example, a mere feeding phase, recycling phase or eluting phase, a feeding phase and (a) simultaneous recycling and/or eluting phase(s), an eluting phase and (a) simultaneous recycling phase(s), a recycling phase and (a) simultaneous eluting phase(s) etc., and said steps are repeated from one to five times during the sequence.
Said phases are employed to form sequences comprising several successive process steps. In accordance with the invention, a sequence preferably comprises four to ten steps.
A sequence comprising said steps is repeated five to seven times to equilibrate the system, whereafter the process is continued in a state of equilibrium.
Typically from two to twelve, preferably two to six, chromatographic sectional packing material beds combined into one or more loops are employed in the method of the invention. A loop may comprise one, two or several sectional packing material beds packed into one or more columns.
The sulphite cooking liquor comprises, in addition to the cooking chemicals, for example undissolved wood material, lignosulphonates, organic acids, hexose and pentose sugars derived as hydrolysis products of hemicellulose, and also small amounts of oligosaccharides if hydrolysis into monosaccharides has been incomplete. Normally a low pH in pulp cooking contributes to the hydrolysis of hemicellulose into monosaccharides. When the pulp is produced from hardwood, the major part of the monosaccharides contained in the cooking liquor consists of xylose, which can be employed as a raw material in the production of crystalline xylose, xylitol and furfural, fo
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Heikkila Heikki
Hyoky Goran
Kuisma Jarmo
Therkorn Ernest G.
Xyrofin Oy
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