Liquid purification or separation – Processes – Chromatography
Reexamination Certificate
2001-11-15
2004-05-25
Therkorn, Ernest G. (Department: 1723)
Liquid purification or separation
Processes
Chromatography
C210S659000
Reexamination Certificate
active
06740243
ABSTRACT:
BACKGROUND
Simulated Moving Bed (SMB) technology for adsorption processing was first developed in the late 1950s for the separation of petrochemicals. Since that time, a number of SMB systems have been commercialized and the method has been applied to adsorption chromatography, ion exchange chromatography, ion exclusion chromatography, size exclusion chromatography and other chromatographic techniques. SMBs are currently used in the food, pharmaceutical, chemical, petrochemical, and other industries. The operating scheme for a binary separation is shown in FIG.
1
. The boxes in the figures represent either adsorption columns, or sections of a column separated by a space with appropriate withdrawal and feed lines. The simulation of bed movement is obtained either by switching all the feed and withdrawal ports in the same direction as the fluid flow at regular switching times, t
sw
, or by moving the adsorbent column. This switching can be seen by comparing the system in parts a, b, c, and d. Regions between withdrawal and feed points are called zones. Each zone has a different function in the separation. Although
FIG. 1
shows a simple system with one column or section per zone, it is also common to have multiple columns or sections per zone. Upon completion of the steps in
FIG. 1
, the cycle repeats itself over and over. Eventually a cyclic steady state is reached and the average concentrations are similar to those that would be obtained if the bed were actually moving continuously. Thus, the movement of the bed is “simulated.”
The four-zone system shown in
FIG. 1
is an effective separation device. However, it is limited to binary separations. Thus, in
FIG. 1
the feed (F) contains two solutes, A and B, that are split into an A product and a B product. If there is a third component in the feed, it will appear in one or both of the two product streams. Because ternary mixtures arise naturally, there is a desire for an effective ternary separation technique in many industries. The most obvious approach to separate ternary mixtures is to connect two 4-zone SMB systems together. The two obvious methods to do this are shown in FIG.
2
. Solute A is the least strongly adsorbed, B is the middle solute, and C is the most strongly adsorbed solute. D is the desorbent, which in aqueous systems is often water. D may or may not be adsorbed. Although the switching of ports or movement of columns is not shown in
FIG. 2
, it is understood to occur. Multiple columns may be employed in each zone. The two trains may differ from each other and have different numbers of columns per zone, different column diameters and lengths, different adsorbents, and different switching times. The approaches shown in
FIG. 2
are seldom employed in commercial practice, because the capital cost and desorbent usage for both schemes is high. Thus, there is major industrial interest in developing methods that are superior to those in FIG.
2
.
SMB systems with different numbers of zones (e.g., 2, 3, 5, and 9) are also well known. A 3-zone system for binary separation is shown in FIG.
4
. Two 3-zone systems could replace the 4-zone system in FIGS.
2
(
a
) and
2
(
b
).
An improved nine-zone system was recently developed. The scheme used a single train with nine zones and employed a recycle stream. A similar nine-zone scheme is redrawn in
FIG. 3
using two trains to allow for more flexibility in operating conditions.
FIG. 3
shows a method where the more strongly adsorbed components, B and C plus desorbent D, are fed to the second train. One can also build a scheme where the less adsorbed components, A and B plus desorbent D, are fed to the second train.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a system for performing a separation of a feed stream that contains at least three components. In one embodiment, the system includes a simulated moving bed separation apparatus adapted to discharge at least two streams, the at least two streams including a first discharge stream containing all the components except that it does not contain substantial amounts of a least retained component, and a second discharge stream containing all the components except that it does not contain substantial amounts of a most retained component, thus effecting a substantial separation of the least retained component from the most retained component.
In another embodiment, the system includes a first simulated moving bed separation apparatus and a second simulated moving bed separation apparatus, the first simulated moving bed separation apparatus adapted to discharge at least two streams, the at least two streams including a first discharge stream containing all the components except that it does not contain substantial amounts of a least retained component, and a second discharge stream containing all the components except that it does not contain substantial amounts of a most retained component, thus effecting a substantial separation of the least retained component from the most retained component. At least one of the first or second discharge streams becomes a feed stream for the second simulated moving bed separation apparatus. Optionally, the at least two streams from the first simulated moving bed separation apparatus include a third discharge stream that contains the least retained component and no substantial amounts of any other component and a fourth discharge stream that contains the most retained component and no substantial amounts of any other component. Preferably, the second simulated moving bed separation apparatus includes a first discharge stream containing all the components except that it does not contain substantial amounts of a least retained component, the second simulated moving bed separation apparatus further includes a second discharge stream containing all the components except that it does not contain substantial amounts of a most retained component, and wherein the second simulated moving bed separation apparatus further includes a third discharge stream taken from between the first and second feed streams of the second simulated moving bed separation apparatus. Preferably, the third discharge stream from the second simulated moving bed separation apparatus contains all the components except that it does not contain substantial amounts of either the least retained component or the most retained component. Optionally, the simulated moving bed separation apparatuses may be configured into a loop.
In another aspect, the present invention provides a process for performing a separation. In one embodiment, the process includes feeding a stream that contains at least three components into a simulated moving bed separation apparatus; substantially separating a least retained component from a most retained component; and discharging at least two streams. The at least two streams include a first discharge stream containing all the components except that it does not contain substantial amounts of the least retained component, and a second discharge stream containing all the components except that it does not contain substantial amounts of the most retained component.
In another embodiment, the process includes feeding a stream that contains at least three components into a first simulated moving bed separation apparatus; substantially separating a least retained component from a most retained component; discharging at least two streams, the at least two streams including a first discharge stream containing all the components except that it does not contain substantial amounts of the least retained component, and a second discharge stream containing all the components except that it does not contain substantial amounts of the most retained component; and delivering at least one of the first or second discharge streams as a feed stream for a second simulated moving bed separation apparatus. Optionally, the at least two streams from the first simulated moving bed separation apparatus include a third discharge stream that contains the least retained component and no substantial amounts
Mueting Raasch & Gebhardt, P.A.
Purdue Research Foundation
Therkorn Ernest G.
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