Moving-Bed Chromatography

Moving-Bed Chromatography

This section explains the moving-bed method, which is one of the ways by which the fixed-bed system can be made continuous.

Let us say that in Fig. 1, the adsorbent is caused to move in the opposite direction of the desorbent (and component A, C) at a migration rate between the velocities of components A and C. This would be the situation in Fig. 2, where while the desorbent is continuously fed into one end of the column, the adsorbent is made to move in the direction opposite to that of the desorbent, while the feed mixture is also supplied at the middle of the adsorbend bed. At this point the adsorbent is caused to move at a migration rate, Us, which is between Ua and Uc, the velocities of components A and C in the fixed-bed mode, i.e. (Ua>Us>Uc).

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In such a situation, components A and C will move within the column at the speeds, Ua-Us (>0) and Uc-Us (<0) respectively. Thus, starting from the point where the feed mixture is fed, components A and C will move in opposite directions from one another within the column. If the mixture is continuously fed into such a device, components A and C will continuously be separated to both ends of the column. However, in a large industrial device, it is extremely difficult to uniformly move the adsorbent without disturbing the absorption band.

From this conception came the idea that rather than have the adsorfent continuously move, instead a column of fixed length (packing bed) could move. This process is shown in Fig. 3.

With a device such as the one described in the preceding paragraph, a mixture can be separated in a continuous manner using the principle of the moving-bed mode. While it is not impossible to move the column in smaller devices, in an industrial device, it becomes mechanically complex.

The simulated moving-bed mode described in the following section is a chromatographic separation method invented so as to gain the same level of separation as the moving-bed mode, without having to actually move the adsorbent.

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the following internet browsers:
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This section explains the moving-bed method, which is one of the ways by which the fixed-bed system can be made continuous.
Let us say that in Fig. 1, the adsorbent is caused to move in the opposite direction of the desorbent (and component A, C) at a migration rate between the velocities of components A and C. This would be the situation in Fig. 2, where while the desorbent is continuously fed into one end of the column, the adsorbent is made to move in the direction opposite to that of the desorbent, while the feed mixture is also supplied at the middle of the adsorbend bed. At this point the adsorbent is caused to move at a migration rate, Us, which is between Ua and Uc, the velocities of components A and C in the fixed-bed mode, i.e. (Ua>Us>Uc).
	We recommend the use of the following internet browsers: Internet Explorer(ver. 3.02 or above) and Netscape Communicator(ver.4.06 or above).
In such a situation, components A and C will move within the column at the speeds, Ua-Us (>0) and Uc-Us (<0) respectively. Thus, starting from the point where the feed mixture is fed, components A and C will move in opposite directions from one another within the column. If the mixture is continuously fed into such a device, components A and C will continuously be separated to both ends of the column. However, in a large industrial device, it is extremely difficult to uniformly move the adsorbent without disturbing the absorption band.
From this conception came the idea that rather than have the adsorfent continuously move, instead a column of fixed length (packing bed) could move. This process is shown in Fig. 3. With a device such as the one described in the preceding paragraph, a mixture can be separated in a continuous manner using the principle of the moving-bed mode. While it is not impossible to move the column in smaller devices, in an industrial device, it becomes mechanically complex. The simulated moving-bed mode described in the following section is a chromatographic separation method invented so as to gain the same level of separation as the moving-bed mode, without having to actually move the adsorbent.
	We recommend the use of the following internet browsers: Internet Explorer(ver. 3.02 or above) and Netscape Communicator(ver.4.06 or above).