Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1996-06-24
1998-09-01
Fortuna, Ana
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210641, 210651, 210805, 2101952, 2102572, 210 97, 210102, B01D 6100
Patent
active
058007130
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for thickening mixtures of solids and liquids by membrane technology by using an apparatus with a number of groups of membrane modules having a residue circuit in series, and relates as well to a device for carrying out this process.
At this time, there are not yet any known apparatuses particularly for thickening residues also known as retentate produced in ultrafiltration or in microfiltration. When clarifying fruit juices by means of filtration technologies of this kind, thickening states of up to approx. 50 vol % wet sediment content are achieved in the remaining residues, measured in the centrifuge test. That is, in the centrifuge, these residues still give off at least 50 vol % fluid. Residues of this kind are still fluid and must be further processed particularly for disposal by means of vacuum rotary filters.
Vacuum rotary filters are precoated filters and for filtration, require diatomaceous earth, which must be procured and likewise disposed of once again. Disposing of residues via the sewers is hardly possible anymore so that residue must be thickened and put in a waste dump or incinerated. In both cases, it is very significant economically to have as low as possible a water content in the residue. Only membrane apparatuses, which are equipped particularly for this purpose, seem practical for a further thickening of the residue beyond the 50 vol % mentioned. Similar ways of looking at the problem also come up in other uses of membrane technology outside the realm of fruit juice.
JOURNAL OF FOOD SCIENCE, vol. 51, no. 3, 1986, pp. 559-563 makes known an apparatus, which has metal membrane ultrafiltration with a simple passage for improved apple juice production yield. Juice production yields of up to 85% were achieved with it, but apparatuses of this kind with simple passages do not seem practical for a thickening of residues on a large scale.
Known organic membranes for filtration apparatuses, as well as pumps required for the residue circuit of apparatuses of this kind, are for the most part designed only for an operating pressure of maximally 6.5 bar. Also, higher pressures can hardly be achieved with a conventional one-stage radial pump. On the other hand, the time requirements for the entire thickening process decrease in proportion to the membrane surface used. During this thickening process, though, the viscosity of the circulating residue increases slowly at first and more rapidly toward the end.
An enlargement of the membrane surface used is suitable for thickening to a high wet sediment content, with a low time requirement. If a number of groups of known membrane modules are connected in parallel, then uneconomically high productive capacities are required for the residue circulation pumps. If this kind of groups of membrane modules are connected in series, then with the high viscosities which occur, normal operating pressures are no longer sufficient for operation.
The object of the invention, therefore, is to disclose a process for thickening solid-liquid mixtures by membrane technology and a device to carry this out, which permit a high wet sediment content of the thickened material with a limited requirement of operating time.
According to the invention, by using an apparatus with a number of groups of membrane modules having a residue circuit in series, the attainment of this object is achieved by the fact that in a first step, the thickening takes place with a membrane apparatus, which is operated in the batch process or quasi-continually, until as a result of the thickening process, the amount of thickening exceeds a first predetermined value, in that then, in a second step in the course of the thickening, at least one group of membrane modules is successively disconnected from the retentate feed stream and further thickening takes Place until a second amount of thickening value is reached, and in that then, in a third step, the thickened residue is removed from the circuit.
An apparatus for carrying out this process distinguishes itself by at le
REFERENCES:
patent: 5110472 (1992-05-01), Gresch
patent: 5112489 (1992-05-01), Hartmann
patent: 5252350 (1993-10-01), Hartmann
patent: 5549829 (1996-08-01), Le
Bucher-Guyer AG
Fortuna Ana
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