Pumps – Combined
Patent
1996-06-27
1998-07-28
Freay, Charles G.
Pumps
Combined
417244, 4174235, 417533, 2101952, F04B 2100, F04B 2304
Patent
active
057855048
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a pressure and liquid recirculation pump which includes mainly an intermediary inlet and an intermediary outlet for the liquid being pumped. More particularly, the present invention relates to an installation used for the concentration of a solution, such as maple water, impure water, and others, by way of a process using a semi-permeable membrane.
According to the present invention, the pressure pump is used both for feeding the liquid, such as maple water, from a stocking tank towards a filter, and then for the introduction under pressure of the filtered liquid in a housing which encloses the membrane, and finally for recirculating the liquid so as to remedy to the filling in or plugging of the membrane and to reduce the concentration at the membrane surface, thereby resulting in a lowering of the osmotic pressure and producing an increase in the permeation flow.
DESCRIPTION OF THE PRIOR ART
It is well known in reverse osmosis processes that the solutions of salt or other solutes, notably those having low molecular weights, for example sea water, maple water and others, are introduced to a selective membrane and submitted to a pressure. Contrary to what happens in the case of a normal osmosis where there is an equilibrium of the solution on both sides of the membrane, the reverse osmosis results in that a solution having a low, and even extremely low, concentration appears on the side of the membrane opposite that of the original solution. In summary, in order to reverse the normal osmotic flow from the side of the membrane where the solution is less concentrated towards the side where the solution is more concentrated, there is exerted on the solution to be treated a pressure differential higher than the osmotic pressure differential of the solutions in contact with the surfaces of the membrane.
It has now been noticed that, during a reverse osmosis process, the concentration at the interface membrane-solution to be treated is higher than the average concentration on the high pressure side of the membrane. This abnormally high concentration at the interface penalizes the quality of the product obtained by the reverse osmosis process because, on the one hand, a considerable amount of salt or other matters in solution, in contact with the membrane is rejected, and on the other hand, by recirculation, there is a reduction of the concentration at the surface of the membrane of the not-very-soluble components which can be tolerated without precipitating on the membrane.
Commonly, the expression filling-in or plugging refers to all phenomena, other than temperature and compaction variations, which reduce a membrane's permeability to pure water. The phenomena are linked to the presence of solutes or of matters in suspension, notably colloids, bacteria, etc., which can deposit at the surface or in the pores of the membrane. The plugging can be more or less rapid depending on the nature of the particles which are present and on their concentration at the surface of the membrane. To obviate to the problems resulting from the plugging of the membrane, which is more or less reversible, rinsing of the membrane using hot or cold water or the cleaning thereof are carried out.
In the production or maple syrup, the maple water has always been evaporated until the syrup was obtained. Now, with the high increase in the price of energy, it is useful to proceed with the evaporation from the solution which is more concentrated than the water directly obtained from the maple tree. In order to do so, reverse osmosis processes have been used, wherein the substantially pure water is discharged and the concentrated water retained. As in the other reverse osmosis cases, there is a serious problem of plugging at the level of the membrane. Indeed, the solutes contained in the maple water are essentially sugars and minerals. The maple water also contains some bacteria, the number of which varying from a few dozens to many millions per ml. The solutes are almost all retained
Freay Charles G.
Les Entreprises Denis Darveau Inc.
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