TMB – True Moving Bed
The continuous TMB process combines the advantages of liquid-liquid chromatography with those of a continuous process such as SMB (Simulated Moving Bed).
Liquid-liquid chromatography is carried out with both a liquid mobile phase as well as a liquid stationary phase. In contrast to SMB and related processes, the movement of the stationary phase is not achieved by a valve circuit but rather via a clocked phase inversion.
- Lowest solvent consumption of all chromatographic methods
- Fast repackaging in case of carrier change because phases are liquid.
- High product purity and very good yield
- No expensive stationary solid phase.
- Extremely low operating costs
- Low product dilution
- GMP and ATEX compliant
- Very high productivity.
Example of TMB for Laboratory
Process development is usually carried out on laboratory scale in a 250 ml system with two 125 ml rotors. Transmission to process scale (scale-up or upscaling) is easily possible with minor adjustments. The data obtained by the laboratory TMB are used to estimate the performance of the TMB application on a large scale, in a pilot plant or in production.
This TMB functions with continuous sample injection on both rotors. The more polar component is collected on side of rotor 1 as extract and the weaker polar component is collected on side of rotor 2 as the raffinate.
Two detectors and two fraction collectors are optionally used for process development. Special software tailored to the TMB process is necessary for controlling, since this method differs very much from conventional batch processes.
Example of TMB for Pilot Plant and Production
In this TMB there are two rotors, each with 6.25 liters rotor volume.
The pulse rate of the two shown cycles leads to substance front accumulation, comparable to the SMB process. Depending on the solubility of the substance, the components migrate to either of the two outputs, extract or raffinate, where they are collected.
Flow Sheet of TMB - True Moving Bed
The true moving bed process is optimized for productivity with greatly reduced solvent consumption. It shows its full strength when permanently applied on a large scale, e.g. a pilot plant. For often changing applications or small quantities the TMB process is less interesting because the system needs time to reach steady state (settling) for high purity production.
This phenomenon of poorer product qualities at startup or shutdown of a continuous process is normal for continuous processes that often also work non-chromatographically. This normal phenomenon is usually taken into account for product collection. This is the reason why the TMB process like any other continuous process is above all more powerful the longer the plant produces in the steady state.
Particularly for applications in pilot plant or production the true moving bed process opens new opportunities for cost savings over conventional chromatographic processes. This saving is based on much lower solvent consumption, but also on non required column material, such as silica gel. Again, in the TMB process the stationary phase as well as the mobile phase is liquid.