Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Patent
1989-12-08
1991-06-04
Dawson, Robert A.
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
210202, 210251, 2105121, 210787, 210806, 210808, B01D 17035, B01D 17038
Patent
active
050211650
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a separator apparatus.
Flotation cells are used in industry for the purpose of separating particles from a liquid. These operate generally by admixing gas bubbles to the mixture to be separated, whereby the gas bubbles are brought into contact with the particles so that the gas bubble-particle entities are effectively lightened and rise to the surface of the mixture where they can be drawn off. To facilitate this action, chemical reagents may be added to the mixture.
It has also been discovered that flotation cells may be used for separating liquid phases one from the other, if one of the liquid phases be present in the form of discreet droplets, such as in an emulsion. However, it has been found that systems of this kind are only capable of satisfactory operation where the influent oil-in-water concentration does not exceed 500 ppm. One use, however, for oil-water separators lies in the cleaning up of residual water at oil wells, after removal of the principal oil concentration therefrom, such as in off-shore oil wells where the residual water must be decontaminated of residual oil to give a high water purity level before the water can, under environmental protection laws, be legally returned to the sea. In such instances, it is often impossible to maintain the influent oily water such that the concentration of oil therein is less than 500 ppm, with the result that unsatisfactory results are obtained, insofar as purity of the effluent water is concerned.
Similar considerations concerning the efficiency of operation of flotation cells of the types including means for introduction of gas bubbles and/or including agitation means apply in relation to efficiency of operation of "degassers" being a form of flotation cell not having provision for agitation of material being separated and not necessarily having provision of introduction of gas bubbles. In the latter, separation of gas and liquid and/or of liquid components is effected simply by gravitational settling. A so called "skimmer" is a form of degasser having provision for removal of free oil. The term "flotation device" is used in this specification to mean any device in which separation is effected by settling.
The invention generally envisages the use of a hydrocyclone to pre-condition a mixture before admission to a flotation device.
In one aspect, there is provided separator apparatus comprising a hydrocyclone having a separating chamber with an inlet for inlet of a liquid mixture to be separated, an overflow outlet for outlet of a less dense liquid component of the mixture and an underflow outlet for outlet of a more dense liquid component of said mixture, and a flotation device, such as a flotation cell coupled to receive outlet material from said underflow outlet. The hydrocyclone is in this case effective in use to effect a pressure reduction in the material emerging from said underflow outlet, as compared to pressure of said mixture at said inlet, whereby to facilitate any of said less dense component present in solution in said more dense component breaking out of solution to be either carried to said overflow outlet or to emerge from the underflow outlet with the more dense component, as droplets thereof in the more dense component, the flotation device being effective to effect separation of said droplets from the more dense component by adherence of gas thereto, to cause the less dense component to float to the surface of the material admitted to the flotation device.
The invention also provides a method for separating liquid components of a liquid mixture one from the other by use of a hydrocyclone to which the mixture is admitted, the hydrocyclone being operated whereby a less dense component of the mixture emerges from an outlet of the hydrocyclone in the form of droplets in a more dense component of the mixture, the material emerging from the outlet being admitted to a flotation device such as a flotation cell to effect separation by adherence of gas bubbles to the droplets to cause the less dense component to
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patent: 4627922 (1986-12-01), Viator et al.
patent: 4935154 (1990-06-01), Arnold
"Small-Scale Experiments on Hydrocyclones for Dewatering Light Oils", I. C. Smith, M. T. Thew, P. S. Debenham and D. P. Colman (International Conference on Hydrocycloner, Oct. 1-3, 1984, Paper I4.
"The Effect of Split Ratio on Heavy Dispersion Liquid-Liquid Separation in Hydrocyclones", Smith, Thew and Colman (2nd International Conference on Hydrocyclones, Sep. 19-21, 1984, Paper E2.
International Patent Publication, WO85/00760, Carroll et al, 2-1985.
WO 85/00851.
Patent 2,000,052, published 6-1978, GB.
Conoco Specialty Products
Dawson Robert A.
Drodge Joseph
Holder John E.
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