Liquid purification or separation – Tangential flow or centrifugal fluid action
Patent
1989-07-18
1991-07-16
Hart, Charles
Liquid purification or separation
Tangential flow or centrifugal fluid action
210788, B01D 17038
Patent
active
050322753
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a cyclone separator. This separator may find application in removing a lighter phase from a large volume of denser phase such as oil from water, with minimum contamination of the more voluminous phase. Most conventional cyclone separators are designed for the opposite purpose, that is removing a denser phase from a large volume of lighter phase, with minimum contamination of the less voluminous phase. In our case, a typical starting liquid-liquid dispersion would contain under 1% by volume of the lighter (less dense) phase, but it could be more.
This invention is based on the observation that when the density difference is small or the droplets of the lighter phase are small (generally less than 25 .mu.m) more efficient separation can be achieved if there is a restriction to flow through the cyclone a longway downstream of the cyclone.
According to the present invention there is provided a cyclone separator comprising at least a primary portion having generally the form of a volume of revolution and having a first end and a second end, the diameter at said second end being less than at said first end, at least one inlet, the or each said inlet having at least a tangential component, at or adjacent said first end for introducing feed to be separated into the cyclone separator and the separator further including at least two outlets, one at each end of the primary portion in which cyclone separator the following relationships apply:
where d.sub.1 is the diameter of the said primary portion where flow enters, preferably in an inlet portion at said first end of said primary portion, (but neglecting any feed channel) d.sub.ix is twice the radius at which flow enters the cyclone through the x.sup.th inlet (i.e. twice the minimum distance of the tangential component of the inlet centre line from the axis) and ##EQU1## where A.sub.ix is the projection of the cross sectional area of x.sup.th inlet measured at entry to the cyclone separator in a plane parallel to the axis of the cyclone separator which is normal to the plane, also parallel to the cyclone axis which contains the tangential component of the inlet centre line, and where ##EQU2## and where d.sub.2 is the diameter of the primary portion measured at a point z.sub.2 where the condition first applies that ##EQU3## for all z>z.sub.2 where z is the distance along the cyclone separator axis downstream of the plane containing the inlet and d is the diameter of the cyclone at z, and further z=0 being the axial position of the weighted areas of the inlets such that the injection of angular momentum into the cyclone separator is equally distributed axially about said axial position where z=0 and being defined by ##EQU4## where z.sub.x is the axial position of the x.sup.th inlet.
Moreover in the separator of the invention, the second end of the primary portion feeds into a second portion of constant diameter d.sub.3 and length l.sub.3 and the following further relationships apply: ##EQU5## where .alpha. is the half angle of the convergence of the separation portion i.e. ##EQU6##
The inlet or inlets may be directed tangentially into the primary portion or into an inlet portion or may have an inwardly spiralling feed channel, such as an involute entry. Preferably, where the inlet(s) are directed tangentially there are at least two equally circumferentially spaced inlets.
A plurality of inlets may be axially staggered along the primary portion or an inlet portion. Moreover the inlet or inlets need not be arranged to feed exactly radially into the separator but may have an axial component to their feed direction.
Each feed channel may be fed from a duct directed substantially tangentially into the inlet portion, the outer surface of the channel converging to the principal diameter of the inlet portion d.sub.1, for example by substantially equal radial decrements per unit angle around the axis, preferably attaining the diameter d.sub.1 after at least 360.degree. around the axis.
The expression ##EQU7## which we call the "swirl coefficient" S
REFERENCES:
patent: 4576724 (1986-03-01), Colman et al.
patent: 4722796 (1988-02-01), Colman et al.
patent: 4820414 (1989-04-01), Carroll et al.
Conoco Specialty Products Inc.
Hart Charles
Holder John E.
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