Hydro-cyclone with circulation outlet for boundary layer flow

Claim 1

A method of operating a hydro-cyclone comprising: a hollow, round casing having, co-axially in series, a cylindrical portion and a frusto-conical portion, the frusto-conical portion tapering toward one end of the hydro-cyclone; an end plate closing an axially outer end of the cylindrical portion opposed to said one end; a tangential inlet into the cylindrical portion adjacent said end plate; a co-axial, light fraction outlet through said end plate; and a co-axial, heavy fraction outlet at said one, taper end of the frusto-conical portion, the method including: injecting flow, containing flow elements of relatively low density and flow elements of relatively high density, tangentially into the cylindrical portion via the tangential inlet; allowing rotating flow to be established on account of said tangential injection of the flow, the rotating flow generating: a pressure gradient increasing with radius and acting on flow elements to tend to move the flow elements radially inwardly, without regard to the relative densities of the flow elements; centrifugal forces acting on flow elements in direct relation to their relative densities to tend to move the elements radially outwardly; allowing the flow elements of higher density to concentrate radially outwardly on account of the effect of the centrifugal forces dominating, and allowing the flow elements of lower density to concentrate radially inwardly on account of the effect of the pressure gradient dominating; generally moving the flow toward the taper end; exhausting a radially outer fraction of the flow in which the flow elements of higher density are concentrated, via the heavy fraction outlet; moving a remaining, radially inner, fraction of the flow, in which the flow elements of lower density are concentrated, toward the light fraction outlet and exhausting the fraction of the flow via said light fraction outlet; treating boundary layer flow, in the form of flow in a boundary layer against the end plate and containing flow elements of higher density and of lower density in undifferentiated condition as emanated from the tangential inlet, in which boundary layer flow of the rotational component is at most effective in attenuated form and the pressure gradient is substantially fully effective, resulting in said boundary layer flow containing the flow elements of higher density and of lower density in undifferentiated condition and flowing inwardly under the influence of said pressure gradient, to prevent said boundary layer flow from being exhausted via the light fraction outlet and thus from contaminating the light fraction overflow with said flow elements of higher density, by selectively drawing off the boundary layer flow via a circulation outlet provided for that purpose through the end plate in the plane of the end plate at an annular position outward of the light fraction outlet.

Claim 2

A method of operating a hydro-cyclone comprising: a hollow, round casing having, co-axially in series, a cylindrical portion and a frusto-conical portion, the frusto-conical portion tapering toward one end of the hydro-cyclone; an end plate closing an axially outer end of the cylindrical portion opposed to said one end; a tangential inlet into the cylindrical portion adjacent said end plate; a co-axial, light fraction outlet through said end plate; and a co-axial, heavy fraction outlet at said one, taper end of the frusto-conical portion, the method including: injecting flow, containing flow elements of relatively low density and flow elements of relatively high density, tangentially into the cylindrical portion via the tangential inlet; allowing rotating flow to be established on account of said tangential injection of the flow, the rotating flow generating: a pressure gradient increasing with radius and acting on flow elements to tend to move the flow elements radially inwardly, without regard to the relative densities of the flow elements; centrifugal forces acting on flow elements in direct relation to their relative densities to tend to move the elements radially outwardly; allowing the flow elements of higher density to concentrate radially outwardly on account of the effect of the centrifugal forces dominating, and allowing the flow elements of lower density to concentrate radially inwardly on account of the effect of the pressure gradient dominating; generally moving the flow toward the taper end; exhausting a radially outer fraction of the flow in which the flow elements of higher density are concentrated, via the heavy fraction outlet; moving a remaining, radially inner, fraction of the flow, in which the flow elements of lower density are concentrated, toward the light fraction outlet and exhausting the fraction of the flow via said light fraction outlet; treating boundary layer flow, in the form of flow in a boundary layer against the end plate and containing flow elements of higher density and of lower density in undifferentiated condition as emanated from the tangential inlet, in which boundary layer flow of the rotational component is at most effective in attenuated form and the pressure gradient is substantially fully effective, resulting in said boundary layer flow containing the flow elements of higher density and of lower density in undifferentiated condition and flowing inwardly under the influence of said pressure gradient, to prevent said boundary layer flow from being exhausted via the light fraction outlet and thus from contaminating the light fraction overflow with said flow elements of higher density, by selectively drawing off the boundary layer flow via a circulation outlet provided for that purpose through the end plate in the plane of the end plate at an annular position outward of the light fraction outlet.