GB2128903A - Separating impurities from a gas - Google Patents

Abstract

A method of separating solid or liquid impurities from a gas involves causing the impurity-bearing gas to flow axially along a path through a gas centrifuge whilst being subjected to a radially-outward force derived from the gas centrifuge in operation, collecting the impurities on the wall of the centrifuge rotor or on the wall of the stationary casing enclosing the rotor, and recovering the impurities, the stripped gas being allowed to flow outwardly generally axially from the centrifuge. Apparatus for performing the method consists of a driven rotor (3) in a stationary casing (1), gas being introduced into the casing (1) at an inlet (11) and being constrained to flow axially into the rotor (3) at the lower end, where vanes (8) impart rotational flow to the gas and impurities are deposited on the wall of the rotor (3) for subsequent recovery. Stripped gas leaves the rotor (3) generally axially at its upper end, where moving vanes 7 and fixed vanes (9) cooperate to convert a part of the rotational energy of the gas into a pressure rise. <IMAGE>

Description

SPECIFICATION A method of and apparatus for separating impurities fromagas This invention relates to the separation of solid or liquid impurities from gases, for example the removal of dustfrom ambient atmosphere.

The conventional methodsforthe removal of solid or liquid impuritiesfrom gases include the use of cyclones, settling chambers or filtration. These methods suffer respectively from the following limitations: cyclones are limited to subsonic speeds and near the chamberwall the centrifugal field falls to zero; for settling chambers the field is limited to earth gravity; and filters are subject to blockage of the pores.

It is an object of the present invention to provide a method, and apparatusforperforming it, which is an economic and more effective alternative to established conventional methods.

According to the invention, a method of separating solid or liquid impurities from a gas comprises the steps of causing the impurity-bearing gas to flow axially along a path through a gas centrifuge whilst being subjected to a radially-outwardforcederived from the gas centrifuge in operation, collecting the impurities on the wall of the rotor, andlorthe stationary casing enclosing the rotor, of the gas centrifuge, and recovering the thus-separated impurities whilst allowing the stripped gas to flow outwardly in a generally axial direction from the centrifuge.

Apparatus for performing the said method may comprise a gas centrifuge including a driven cylindrical rotorandastationarycasingenclosingthesaid rotor, and entry in said casing for impurity-bearing gas, an inlet at one end of said rotorfor entered gas, an outlet at the other end of said rotorforstripped gas, and means for protecting the impurity-bearing gas from that bearing for the rotor which is adjacent the gas inlet end.

Alternately, the path of the gas within the rotor may be arranged to be re-entrant in character, which results in providing additional effective length (for the same rotor length) during which centrifugal separation is taking place.

The impurities may be collected from the wall ofthe rotor on which they are deposited either by mechanical means, such as dislodgement by repeated impacts either after stopping the centrifuge or with the rotor running, or by replacement of the rotor and recovery or disposal ofthe impurities (including disposal of the rotorwhere a suitable inexpensive material for the rotor has been employed), or washing the impurities off the rotor and/orcasing walls.

The rotor may be made slightly conical so that collectionofthe separated impurities is encouraged because the conical shape encou rages them to fiow or migrate along the wall underthe action of centrifugal force (analogous to flowing downhill) to facilitate their leaving the rotor continuousi#.

Examples of gas centrifuge for performing the said method will now be described with reference to the accompanying drawings, wherein: Figure lisa diagrammatic side view in medial section showing one embodiment and Figure 2 is a similar view, showing another embodiment.

In Figures 1 and 2, like parts have like reference numerals.

Referring to the embodiment of gas centrifuge shown in Figure 1, a gas cleaning centrifuge 1 has a casing 2 and a vertically disposed rotor3 carried on a spindle 4journalled at its ends in suitable bearings (not shown) which can be conventional air bearings or other suitable high speed bearings of known type, disposed in housings 5, 6 respectively. The lower housing 6 also encloses a suitable motor (not shown) for rotating the rotor 3 via spindle 4.The rotor 3 whose wall thickness must be adequate to withstand the centrifugal pressure of the deposits is secured to the spindle 4 by upper and lower radial vanes 7, 8 respectively, the vanes 7 being closely adjacent fixed vanes 9 depending from the housing 5 and located by an annular plate 10 which also provides a partition dividingthevolumecontainingthebearing housing 5 fromthecasingvolumewhichseesincoming gas to be stripped. The latter enters the casing 2 at circumferentiallydisposed inlets 11 and passes downwardly between the rotor 3 and the casing 2 before passing into the rotor 3 at the lower end, the lower vanes 8 serving to accelerate the gas to the rotational speed of the rotor; once past the vanes 8 the gas rotates with the rotor 3, with little angular motion relative to the rotor.As the gas leaves the top of the rotor 3 it meets the fixed vane 9 which converts a part of the rotational energy ofthe gas into a pressure rise, as in an axial flow compressor. This ensures that the leakage which willoccurpasttheoutsideoftherotorwill be of clean gasfrom outletto inlet. The gas compression may also be of value in circulating the gasthrough the system in which the centrifuge is connected, the centrifuge thereby providing the dual functions of a gas cleaner and a blower or compressor.

A spinner 12 attachedto the spindle 4 just above the housing 6 serves to keep the lower bearing and motor free from solid or liquid from the entering gas. The spinner may also be the rotor of a drive motor.

Separation does not in fact need to take place solely inside the rotor 3; the gas outsidethe rotor3 will also rotate, although less rapidly, and hence impurities in the space between the rotor 3 andthe casing 2 will movetowardsthe casing 2. Thusinthe the embodiment of Figure 1 the spaces both outside and inside the rotors are used, the gas flowing down outside the rotor3 and up inside. This has the advantagethatthe heavier particles (probablyforming the bulkofthe impuritiesto be removed), will be deposited on the casing wall before entering the rotor itself. In an alternative embodiment, only the space between the rotor and the casing is employed for separation, there being no flow path for gas provided within the rotor.

Solids or liquid droplets can be collected by being washed offthe inner wall of rotor 3 or dissolved by a supply of water introduced via water supply pipe 13.

An annularguard 14 acts as a seal to reduce gas flow between inlet and outlet.

One means of removing the solid particles or droplets which accumulate on the rotor wall is to introduce water or another liquid which will carry them away in suspension or in solution. An arrange mentforthisshown in Figure 1 incorporates the pipe 13 which introduces the water or other liquid into the rotor. The centrifugal force will cause the liquid to form a layer on the rotorwall which, in this arrangement, is prevented from leaving the top of the rotor by an inward turning lip 15 at the top of the rotor. The liquid must therefore travel down the rotor, as a layer onthewall, emerging from the bottom carrying with it the substances removed from the gas stream.In another embodiment ofthe invention the liquid flow is upwardly in the rotor rather than down, the preferred arrangement being one in which the liquid emerges into the space from which the impurity-bearing gas enters the rotor.

In the embodiment shown in Figure 2, two gas passes within the rotor 3 give additional effective length. Here an air bearing 15 is shown atthetop which acts also as a seal between the clean and dirty gas areas. The extended passageway, re-entrant insofar as the rotor 3' is concerned, is provided by spaced tubular parts 16, of rotor3', joined by upper and lowervanes 18,19 respectively. Further re-entrant passageways can be provided by further spaced tubular parts outside part 16, if required. The dual or multiple passageways can be arranged in parallel instead of in series, or possibly in a series parallel combination. The drive of rotor 3' is by a stub spindle 20 journalled in a ball-and-cup bearing 21 and driven by a motor 22.

CLAIMS (Filed on 2619183) 1. A method of separating solid or liquid impuri tiesfrom a gas, comprising the steps of causing the impurity-bearing gas to flow axially along a path through a gas centrifuge whilst being subjected to a radially-outward force derived from the gas centrifuge in operation, collectingthe impurities on the wall of the rotor, and/orthe stationary casing enclosing the rotor, of the gas centrifuge, and recovering the thus-separated impurities, the stripped gas being allowed to flow outwardly in a generally axial direction from the centrifuge.

2. Apparatus for performing the method according to claim 1, comprising a gas centrifuge including a driven rotor and a stationary casing enclosing said rotor, an entry in said casing from impurity-bearing gas, an inlet atone end of said rotorfor entered gas, an outletattheotherendofsaid rotor far stripped gas, and means for protecting the impurity-bearing gas from that bearing forthe rotorwhich is adjacent the gas inlet end.

3. Apparatus according to claim 2, wherein, instead ofthe path ofthe gas within the rotor being merely lengthwise of the rotor, the path of the gas within the rotor is arranged to be re-entrant in character, resulting in the provision of additional effective length of the same rotor length during which centrifugal separation is taking place.

4. Apparatus according to either of claims 2 and 3 wherein the impurities are recovered by being col lectedfrom thewall of the rotor on which they are deposited by mechanical means such as dislodgement by repeated impacts with the rotor either during running or after stopping the rotor.

5. Apparatus according to either of claims 2 and 3, wherein the impurities are recovered by replacement of the rotor.

6. Apparatus according to either of claims 2 and 3, wherein the impurities are recovered by washing them offthe rotor andlorcasing walls.

7. Apparatus according to any of claims 2-6, wherein the rotor is made conical so as to encourage the separated impurities to flow or migrate along the rotor wall under the action of centrifugal force to facilitate their leaving the rotor continuously.

8. A method of separating solid or liquid impurities from a gas, substantially as hereinbeforede- scribed, or substantially as hereinbefore described with reference to the accompanying drawings.

9. Apparatus for performing the method accord ingtoclaim 1 or claim 8, substantially as hereinbefore described with reference to Figure 1, or Figure 2, ofthe accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. introduce water or another liquid which will carry them away in suspension or in solution. An arrange mentforthisshown in Figure 1 incorporates the pipe 13 which introduces the water or other liquid into the rotor. The centrifugal force will cause the liquid to form a layer on the rotorwall which, in this arrangement, is prevented from leaving the top of the rotor by an inward turning lip 15 at the top of the rotor. The liquid must therefore travel down the rotor, as a layer onthewall, emerging from the bottom carrying with it the substances removed from the gas stream.In another embodiment ofthe invention the liquid flow is upwardly in the rotor rather than down, the preferred arrangement being one in which the liquid emerges into the space from which the impurity-bearing gas enters the rotor. In the embodiment shown in Figure 2, two gas passes within the rotor 3 give additional effective length. Here an air bearing 15 is shown atthetop which acts also as a seal between the clean and dirty gas areas. The extended passageway, re-entrant insofar as the rotor 3' is concerned, is provided by spaced tubular parts 16, of rotor3', joined by upper and lowervanes 18,19 respectively. Further re-entrant passageways can be provided by further spaced tubular parts outside part 16, if required. The dual or multiple passageways can be arranged in parallel instead of in series, or possibly in a series parallel combination. The drive of rotor 3' is by a stub spindle 20 journalled in a ball-and-cup bearing 21 and driven by a motor 22. CLAIMS (Filed on 2619183)

1. A method of separating solid or liquid impuri tiesfrom a gas, comprising the steps of causing the impurity-bearing gas to flow axially along a path through a gas centrifuge whilst being subjected to a radially-outward force derived from the gas centrifuge in operation, collectingthe impurities on the wall of the rotor, and/orthe stationary casing enclosing the rotor, of the gas centrifuge, and recovering the thus-separated impurities, the stripped gas being allowed to flow outwardly in a generally axial direction from the centrifuge.

2. Apparatus for performing the method according to claim 1, comprising a gas centrifuge including a driven rotor and a stationary casing enclosing said rotor, an entry in said casing from impurity-bearing gas, an inlet atone end of said rotorfor entered gas, an outletattheotherendofsaid rotor far stripped gas, and means for protecting the impurity-bearing gas from that bearing forthe rotorwhich is adjacent the gas inlet end.

3. Apparatus according to claim 2, wherein, instead ofthe path ofthe gas within the rotor being merely lengthwise of the rotor, the path of the gas within the rotor is arranged to be re-entrant in character, resulting in the provision of additional effective length of the same rotor length during which centrifugal separation is taking place.

4. Apparatus according to either of claims 2 and 3 wherein the impurities are recovered by being col lectedfrom thewall of the rotor on which they are deposited by mechanical means such as dislodgement by repeated impacts with the rotor either during running or after stopping the rotor.

5. Apparatus according to either of claims 2 and 3, wherein the impurities are recovered by replacement of the rotor.

6. Apparatus according to either of claims 2 and 3, wherein the impurities are recovered by washing them offthe rotor andlorcasing walls.

7. Apparatus according to any of claims 2-6, wherein the rotor is made conical so as to encourage the separated impurities to flow or migrate along the rotor wall under the action of centrifugal force to facilitate their leaving the rotor continuously.

8. A method of separating solid or liquid impurities from a gas, substantially as hereinbeforede- scribed, or substantially as hereinbefore described with reference to the accompanying drawings.

9. Apparatus for performing the method accord ingtoclaim 1 or claim 8, substantially as hereinbefore described with reference to Figure 1, or Figure 2, ofthe accompanying drawings.