Method and apparatus for continuously fractionating particles contained within a viscoplastic fluid

Patent metadata

Field	Value
Publication number	US-9849466-B2
Application number	US-201214129820-A
Country	US
Kind code	B2
Filing date	Jun 29, 2012
Priority date	Jun 29, 2011
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

Particles are separated from a source viscoplastic fluid by flowing streams of the viscoplastic fluid and a destination fluid in parallel streamed relationship inside a rotating cylindrical annulus by using baffles to introduce each fluid independently at an inlet lower end of the annulus and for separating the upper streams consisting of an un-yielded source and destination flow proximate the radially innermost side of the annulus, a bulk axial flow in a more central region and a yielded layer destination flow adjacent the radial outermost side of the annulus which contains the particles that have separated. Inlet and outlet baffles are provided at each end of the vertically oriented device to maintain the flows discrete on entry and to maintain the separated flows discrete on exit so as to facilitate removal of the component flows from the fractionator.

First claim

The invention claimed is:

1. A method for continuously fractionating particles within a viscoplastic fluid, the method comprising:
(a) flowing one stream of the viscoplastic fluid having the particles to be fractionated and a second type of particles therein (“source fluid”) in a direction that is non-orthogonal relative to an axis of rotation such that the source fluid experiences laminar spiral Poiseuille flow;
(b) subjecting the source fluid to solid body rotation about the axis of rotation such that the particles to be fractionated experience centrifugal force equalling or exceeding resistive forces corresponding to the yield stresses of the viscoplastic fluid and such that the second type of particles experiences centrifugal force less than the resistive force corresponding to the yield stresses of the viscoplastic fluid while maintaining laminar spiral Poiseuille flow;
(c) continuing flowing and rotating the source fluid until the particles to be fractionated migrate sufficiently from the second type of particles to be separately collected from the second type of particles; and
(d) collecting the particles that have been fractionated.

2. A method as claimed in claim 1 further comprising:
(a) flowing another stream of fluid (“destination fluid”) parallel to the source fluid, wherein the source fluid is nearer to the axis of rotation than the destination fluid and wherein the destination and source fluids contact each other and comprise a stable multilayer flow;
(b) subjecting the source and destination fluids to solid body rotation about the axis of rotation such that the particles to be fractionated experience centrifugal force equalling or exceeding resistive forces corresponding to the yield stress of the source fluid and such that the second type of particles experiences centrifugal force less than the resistive force corresponding to the yield stress of the source fluid while maintaining the stable multilayer flow; and
(c) continuing flowing and rotating the destination and source fluids until the particles to be fractionated migrate from the source fluid into the destination fluid, and wherein the particles to be fractionated are collected from the destination fluid.

3. A method as claimed in claim 2 wherein the destination fluid comprises a viscoplastic fluid, and wherein the source and destination fluids are subjected to solid body rotation such that the particles to be fractionated experience centrifugal force equalling or exceeding resistive forces corresponding to the yield stresses of the source and destination fluids and such that the second type of particles experiences centrifugal force less than the resistive force corresponding to the yield stresses of the source and destination fluids.

4. A method as claimed in claim 3 wherein the direction in which the destination and source fluids flow is parallel to the axis of rotation.

5. A method as claimed in claim 3 wherein the source and destination fluids comprise the same type of viscoplastic fluid.

6. A method as claimed in claim 3 further comprising subjecting the source and destination fluids to solid body rotation prior to contacting them together.

7. A method as claimed in claim 6 further comprising fully developing the velocity profiles of the source and destination fluids prior to contacting them together by pumping the source and destination fluids along the axis of rotation.

8. A method as claimed in claim 3 , wherein the source and destination fluids are subjected to solid body rotation in a fractionation conduit and further comprising introducing the source and destination fluids simultaneously through a single inlet conduit to the fractionation conduit prior to being subjected to solid body rotation, wherein the source and destination fluids have sufficiently different densities such that they separate into two fractions prior to collecting the particles that have been fractionated.

Assignees

• Martinez Dominic Mark
• Olson James Allen
• Madani Ario
• Frigaard Ian Alistair
• Farajisarir Davood
• Lockhart James
• Univ British Columbia

Inventors

• Martinez Dominic Mark
• Olson James Allen
• Madani Ario
• Frigaard Ian Alistair
• Farajisarir Davood
• Lockhart James

Classifications

• B04B11/06

  Arrangement of distributors or collectors in centrifuges · CPC title

• B03B5/32 Primary

  using centrifugal force · CPC title

• B04B11/02

  Continuous feeding or discharging; Control arrangements therefor · CPC title

• B04B7/08 Primary

  Rotary bowls (centrifugal casting machines B22D) · CPC title

• B04B1/00

  Centrifuges with rotary bowls provided with solid jackets for separating predominantly liquid mixtures with or without solid particles · CPC title