Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1994-04-18
1996-03-12
Fortuna, Ana M.
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
210799, 134 10, B01D 6100
Patent
active
054983410
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for ultrafiltration of stabilized emulsions, for example of used cutting oils, and more particularly to such a process consisting in introducing a small quantity of salt into the emulsion with a view to destabilizing it, that is to say without preliminary separation of the water and of the oil before its delivery to the ultrafiltration membrane.
2. Description of the Related Art
A cutting oil is a mixture of mineral oil, of surface-active agents, of cosurfactants and of many various additives (bactericides, extreme pressure agents, lubricants, corrosion inhibitors, wetting agents and the like). This combination of constituents which are emulsifiable in all proportions with water is commonly employed at concentrations which vary from 1 to 10% of oil per 90 to 99% of water. Cutting oil emulsions are employed in all operations for machining and shaping metals and cutting stones in order to provide the following functions at the cutting tool:
These emulsions operate in a closed circuit on machine tools until they lose their effectiveness over some months because of a slow bacterial degradation and because of being contaminated with impurities. They must consequently be replaced at regular intervals. The organic pollution caused by a direct discharge of these spent emulsions into natural surroundings can be damaging to the environment. The problem of the treatment of these spent cutting oil emulsions must therefore be faced.
Stabilized emulsions cannot be treated by conventional methods of separation which are employed for unstabilized emulsions, namely: phase separation, flotation or coalescence with a particle or fibre bed or hydrocyclones, because the oil droplets are too small to be capable of being separated by gravity separation. In addition, the presence of the surface-active agents and of the cosurfactants prevents any coalescence of the oil droplets because of the existence of an electrical and/or mechanical barrier.
The treatment methods which are employed at present can be classified into three categories: distinguished; the simplest one consists of direct burning of the spent emulsion; the other type is based on an evaporation. The aqueous phase is thus evaporated off and the oil is recovered at the end of the operation. These two methods are adapted to all types of cutting fluid but have a major disadvantage, namely a very high energy consumption. destabilization of the spent oil-water emulsion, which is often referred to as "breaking the emulsion". This breaking is generally obtained by the action of chemical reactants of acidic, salt or polyelectrolyte type; the subsequent separation of the water and of the oil is generally carried out by simple phase separation. An example of this type of breaking process is described in document FR-A-2,656,812. Although resulting in good separation efficiencies after quite long phase separation periods, these processes exhibit two major disadvantages. The first disadvantage is related to the large quantities of reactants to be employed and is reflected in the substitution of an acidic or saline pollution for an initial organic pollution. The second major disadvantage of these techniques is that the breaking is comparable to a chemical reaction and is therefore found to be stoichiometric, that is to say that it requires an optimum dosage of the reactants employed. It is therefore essential to carry out tests as during a flocculation in order to determine beforehand the optimum concentrations of salts, acids or polyelectrolytes to be employed. ultrafiltration, the emulsion containing cutting oil droplets with a diameter of less than 5 .mu.m is circulated through an ultrafilter equipped with a water-permeable porous membrane whose pores have a diameter of approximately 100 .ANG.. Treatment processes employing ultrafiltration exhibit undoubted advantages. They consume only little energy, the treatment plants are small in size and, after treatment, the water is free fro
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Robert L. Goldsmith, "Ultrafiltration of Soluble Oil Wastes" Journal UPCF, vol. 46, No. 9, Sep. 1974, pp. 2183-2192.
Dimitri Hadjiev
Jacques Cotteret
Julien Edmond
Mohamed Belkacem
Yves Aurelle
Elf Antar France
Fortuna Ana M.
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