Food or edible material: processes – compositions – and products – Processes – Separating a starting material into plural different...
Patent
1989-06-22
1993-10-12
Pratt, Helen F.
Food or edible material: processes, compositions, and products
Processes
Separating a starting material into plural different...
426492, 21032165, A23L 230
Patent
active
052523500
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for clarifying liquids, particularly raw juice from fruit, grapes, berries or other fruits and vegetables by ultrafiltration or microfiltration.
BACKGROUND OF THE INVENTION
In the known processes of microfiltration and ultrafiltration, mainly tube- or plate-shaped membrane filtration modules are used. The liquid to be clarified or filtered flows crosswise to the filtration device over the membrane filtration surface. Thus, the clarified juice, the permeate, is separated from the liquid containing the filtration residues. This procedure is repeated from time to time in one circuit of the retentate. During batch processing the concentration of the filtration residues, the so-called proportion of solids, constantly increases.
The disadvantage of these known processes is that with increasing filtration time and increasing proportion of solids in the retentate, a decrease occurs in the filtration yield, e.g. the amount of permeate outflow per filtration surface unit and time unit. This decrease in the filtration yield can amount to less than half the starting value. For achieving a certain filtration yield, the reduced filtration yield must be taken into account in the design of ultrafiltration and microfiltration units. However, this requires large filtration surfaces and leads to expensive, partially uneconomical units with a large number of filtration modules.
SUMMARY OF THE INVENTION
The object of the invention is to avoid the disadvantages mentioned and to develop a process, which with reduced investment costs guarantees a high filtration yield.
This object is achieved according to the invention in that the proportion of solids in the retentate is sharply increased by concentrating during the starting time and after reaching the maximum filtration yield, is maintained constant by regulation. In this way the filtration yield, which at first decreases and then increases again when the proportion of solids increases further, can be maintained at a level far exceeding the starting value.
To ascertain the proportion of solids and to regulate the condition of the retentate, the proportion of solids or another quantity dependant on the proportion of solids is measured in the retentate circuit and the measured quantity is used to regulate the amount of retentate outflow or the amount of fresh juice to be fed in.
In another embodiment of the invention, the amount of permeate outflow or the filtration yield is measured to regulate the condition of the retentate and the measured quantity is used to regulate the amount of retentate outflow or the amount of fresh juice to be fed in. The measurement of proportion of solids can be omitted in this case, since the condition of the retentate is also largely dependant on the filtration yield.
Another embodiment of the invention provides for regulating the condition of the retentate in that both the proportion of solids or another quantity dependant on the proportion of solids and the amount of permeate outflow or the filtration yield are measured, and the desired value of the proportion of solids is determined by the maximum filtration yield value which can be achieved at the beginning of the process. The regulation of the condition of the retentate thus takes place depending on the proportion of solids, the desired value of which is not however pre-set as an empirical value, but rather is ascertained by ongoing measurement of the filtration yield.
To obtain the highest possible concentration of the proportion of solids in the retentate in the shortest possible time during the starting time, at first a relatively small amount of retentate is used and the remaining portion of the batch amount is fed to the retentate circuit only after achieving the desired value of the proportion of solids.
The unit for carrying out the process according to the invention is characterized in that, in the retentate circuit of an ultrafiltration or microfiltration device there is placed a measuring device to measure the proportion of solids and it is conn
REFERENCES:
patent: 3756408 (1973-09-01), Spatz et al.
Bucher - Guyer AG Maschinenfabrik
Jaskiewicz Edmund M.
Pratt Helen F.
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