Simulated moving bed block displacement procedure

Details Simulated moving bed block displacement procedure Simulated moving bed block displacement procedure

1999-09-14

2001-03-13

Brunsman, David (Department: 1755)

Sugar, starch, and carbohydrates

Processes

Carbohydrate manufacture and refining

C210S656000

Reexamination Certificate

active

06200390

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
This invention pertains to the control of a simulated moving bed (SMB). It is particularly directed to a block displacement procedure which may be applied, for example, to recover a betaine fraction from the circulation loop in an SMB of a sugar factory.
2. Background Art
U.S. Pat. No. 4,412,866 describes the operation of an SMB to separate the components of a feed stock. A resin bed is divided into a series of discrete vessels, each of which functions as a zone within a circulation loop. A manifold system connects the vessels and directs in appropriate sequence to each vessel each of the four media accommodated by the process; namely, feed stock, eluant, extract and raffinate. As applied to a sugar factory, a typical feed stock is sucrose solution, the eluant is water, the extract is an aqueous solution of sucrose and the raffinate is an aqueous solution containing nonsucrose, such as salts and high molecular weight compounds
The largest single loss of sugar values from a typical sugar factory is attributable to molasses formation. Molasses comprises the byproduct (or waste) stream remaining after repeated crystalizations to recover purified sugar. This molasses is typically of such low purity that further crystallization procedures for the recovery of additional sugar are economically impractical. SMB arrangements similar to those disclosed by the '866 patent are used in sugar factories to process molasses; typically producing a product fraction of relatively high (e.g., 90%) purity and low ash content and a waste fraction, comprising 40-50% of the feed, of relatively low purity and high ash content. (As used in the sugar industry, “purity” specifies percent by weight sucrose of the solids contained in a sample, on a dry weight basis.) This waste fraction contains most of the betaine values of the molasses feed. Betaine, being the most abundant nitrogenous compound found in molasses, has been recognized as a commercially useful byproduct; notably for use in animal feeds.
U.S. Pat. No. 4,359,430 and 5,127,957 describe methods for the recovery of a betaine fraction from various sources, such as the molasses produced by a sugar factory. The '957 patent discloses a batch operation imposed upon an SMB system. The method involves shutting off all input and output streams to the SMB while maintaining circulation through the resin bed. Thereafter, water and/or molasses feed are introduced to displace betaine, sucrose and rest molasses from separate columns in the loop.
There remains a need for an improved method for the recovery of betaine from an SMB system. Ideally, betaine removal should be accomplished without disrupting the continuous operation of the system.
DISCLOSURE OF INVENTION
According to this invention, a “block” of betaine is displaced from the circulation loop of an ion exclusion system configured as an SMB without disturbing the normal operation of the system. In practice, a betaine fraction is withdrawn from the circulating loop while an equal volume of water is introduced to the loop. The circulation loop continues without disruption.
Broadly, the invention is applied to a simulated moving bed process for the recovery of sugar values from a circulating stream moving in a closed loop through and between a plurality of segregated resin beds wherein input streams of feed and eluant are introduced to the circulating stream and output streams of extract and raffinate are withdrawn from the circulating stream at respective locations in the loop, those respective locations of the input and output streams being determined by the requirements of the process. Inherently, there develops a fluid block in the circulating loop concentrated with respect to betaine values. That block may be referred to as “betaine-enriched,” although it is more properly regarded as being concentrated with respect to betaine values, no such values being necessarily added to the circulating stream. The improvement of this invention comprises withdrawing at least a portion (referred to as a “betaine-enriched fraction”) of the betaine-enriched block from the circulating stream. Such withdrawal is from a betaine recovery location in the loop. A volume of eluant, typically water, sufficient to compensate for the withdrawn portion is injected into the circulating stream, ideally immediately adjacent and downstream of the betaine recovery location. The betaine recovery location is generally situated between a first location in the loop at which eluant is introduced to the loop and a second location at which extract is removed from the loop. Simply stated, the invention provides a method for displacing a block of betaine from the circulation loop of an ion exclusion system configured as an SMB without disturbing the normal operation of the system. The method comprises withdrawing a betaine fraction from that circulating loop while simultaneously introducing an equal volume of water to that loop. Ordinarily, water is introduced to the loop downstream with respect to the withdrawal of the betaine fraction. It is recognized that every location in a circulating loop may be regarded as both upstream and downstream of every other location in the loop. The terms “upstream” and “downstream,” as used in this disclosure have reference to the direction of flow of a circulating stream as it travels from the point of introduction of an input feedstock stream around the loop, back to that introduction point.
According to an illustrative embodiment of this invention, a betaine recovery procedure is applied to an SMB sugar recovery process in which a plurality of resin zones are arranged to receive flow in series. A circulation stream is caused to flow continuously at a basic flow rate through a loop including those zones and a connecting manifold system. The manifold system is configured to introduce an input feed stock stream to the circulation stream exiting a first resin zone as the circulation stream flows to a second resin zone located downstream in the circulation stream with respect to the first resin zone. The manifold system is further operated to withdraw an output raffinate stream from the circulation stream exiting the second resin zone. It further functions to introduce an input water stream to the circulation stream entering a fourth resin zone downstream in the circulation stream with respect to the first, second and a third said resin zone, and to withdraw an output extract stream from the circulation stream exiting the fourth resin zone. The manifold system is further operated to shift each of the feedstock, water, raffinate and extract streams, as a group, to other locations around the loop so that the feedstock stream is introduced in sequence to each of the four resin zones, while each of the other input and output streams are similarly advanced to maintain their respective positions in the loop, The recovery procedure comprises operating the manifold system to divert a betaine-enriched fraction from the circulation stream while simultaneously introducing a corresponding volume of water to the circulation stream at a location which maintains the basic flow rate in the loop. In most instances, the betaine-enriched fraction is diverted from the circulation stream at a location in the loop downstream from the introduction of the input water stream and upstream from the output extract stream.


REFERENCES:
patent: 4359430 (1982-11-01), Heikkila et al.
patent: 4412866 (1983-11-01), Schoenrock et al.
patent: 5102553 (1992-04-01), Kearny et al.
patent: 5127957 (1992-07-01), Heikkila et al.
Copy of International Search Report dated Apr. 3, 1998.

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