| 摘要 |
Installations with membrane modules (1, 2) and a retentate circuit are used according to the transverse current process for concentrating retentate residues when clarifying fruit juices by ultrafiltration or microfiltration. The installation is at first operated at an approximately constant retentate tangential velocity on the membranes until an increased concentration is obtained. The transmembrane differential pressure of the membrane modules (1, 2) is then held constant or increased and the tangential velocity is reduced until the desired degree of concentration of the retentate residue is reached. Retentate positive-displacement pumps (8) with an adjustable speed of rotation are used to carry out the last reducing step. In order to avoid fouling of the membranes of the membrane modules (1, 2), the installation is operated with special retentate flow dividers (10), or each group of membrane modules is associated to its own circulation pump.
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