Gas separation – With concentrate backflow or re-entrainment preventing means
Reexamination Certificate
2001-03-23
2003-03-18
Smith, Diane S. (Department: 1724)
Gas separation
With concentrate backflow or re-entrainment preventing means
C015S353000, C055S426000, C055S439000, C055S459100, C055SDIG003
Reexamination Certificate
active
06533834
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to cyclonic separators. In one particular application, the invention relates to the cyclonic separation of particulate material from an air flow.
BACKGROUND OF THE INVENTION
The use of a cyclone, or multiple cyclones connected in parallel or series, has long been known to be advantageous in the separation of particulate matter from a fluid stream. Typically, a relatively high speed fluid stream is introduced tangentially to a generally cylindrical or frusto-conical container, wherein the dirty air stream is accelerated around the inner periphery of the container. The centrifugal acceleration caused by the travel of the fluid in a cyclonic stream through the cyclone causes the particulate matter to be disentrained from the fluid flow and, eg., to collect at the bottom of the container. A fluid outlet is provided for the extraction of the fluid from the centre of the top of the cyclone container, as is well known in the art.
A typical flow path in a cyclone separator is as follows. Fluid to be treated is introduced tangentially at a fluid inlet located at an upper end of the cyclone container. The fluid stream rotates around the inner surface of the cyclone container, and spirals generally downwardly around the inner surface of the container (if the cyclone container is vertically disposed). At a bottom end of the cyclone container the fluid stream travels radially inwardly, generally along the bottom of the container and then turns upwardly and proceeds vertically up and out of the cyclone container. The particulate matter separating action of the cyclonic flow occurs substantially around the inner surface of the container. Once the fluid moves inwardly to the centre of the container, and upwardly there through, there is little or no dirt separation achieved.
The difficulty experienced with prior art cyclonic separators is the reentrainment of the deposited particles back into the outgoing fluid flow. Deposited particles exposed to a high speed cyclonic flow thereover have a tendency to be reentrained. This is particularly problematic when the container has a solid bottom portion in which the dirt collects. However, there is a potential reentrainment problem even if the bottom of the container has a passageway provided in the bottom thereof to convey the separated particulate material away from the container.
If a high degree of separation is required, it is known to connect a plurality of cyclones in series. While using several cyclones in series can provide the required separation efficiency, it has several problems. First, if the separators are to be used in industry, they generally need to accommodate a high flow rate (eg. if they are to be used to treat flue gas). The use of a plurality of cyclones increases the capital cost and the time required to manufacture and install the separators. Further, the use of a plurality of cyclones increases the space requirements to house the cyclones. Accordingly, there is a need for an improved anti-reentrainment means for cyclonic separators.
SUMMARY OF THE INVENTION
In has now been discovered that a single cyclone having improved efficiency (eg. up to 99% efficiency) may be manufactured by positioning in the cyclone chamber a member for creating a dead air space below the cyclonic flow region of the cyclone chamber. This construction traps separated material below the cyclonic flow region and inhibits the reentrainment of the separated material. Thus, a single cyclone may be used in place of a plurality of cyclones to achieve the same separation efficiency.
In accordance with the instant invention, there is provided a separator for separating entrained particles from a fluid flow, the separator comprising a cyclone chamber having a cyclonic flow region, the cyclonic flow region having a center, a longitudinal axis, an outer peripheral portion, an inner portion and a radial width; a fluid inlet for introducing a cyclonic fluid flow to the cyclonic flow region; a fluid outlet for removing the fluid flow from the cyclone flow region; a plurality of vanes positioned in the cyclone chamber and extending inwardly towards the center, the vanes having an inner portion and an outer portion and creating a dead space; and, a cover member spaced from the bottom and positioned above the vanes.
In one embodiment, the separator has a bottom and the vanes are spaced from the bottom whereby the dead zone is positioned beneath the vanes.
In another embodiment, the separator has an open end distal to the fluid inlet and the vanes are spaced from the open end whereby the dead zone is positioned beneath the vanes.
In another embodiment, the cover member is positioned over the inner portion of the vanes. The cover member may have a radial width that is from 25-75% and preferably from 25-35% of the radial length of the vanes.
In another embodiment, the vanes extend downwardly from the cover member. The vanes may have a height of at least three-quarters the distance between the bottom and the cover member. Preferably, all of the vanes are of substantially the same height. Further, preferably the vanes are substantially parallel to the longitudinal axis.
In another embodiment, the vanes extend upwardly at an angle of up to 45° to the longitudinal axis.
In another embodiment, the vanes are equidistantly spaced around the bottom.
In another embodiment, the vanes extend to the centre and the cover member has a radial width that is from 25-35% of the radial width of the cyclonic flow region.
In another embodiment, the vanes curve in the downstream direction as they extend inwardly from the outer periphery.
In another embodiment, the vanes extend radially inwardly from the outer periphery.
In another embodiment, the separator further comprises a cleaner head adapted for movement over a floor and having a fluid nozzle positionable adjacent the floor, the nozzle in fluid flow communication via a passageway with the separator fluid inlet, a handle for moving the cleaner head over the floor, and a casing for housing the cyclone chamber. The separator may further comprise a centre feed pipe, the vanes extend to the centre feed pipe and the cover member extends outwardly from the centre feed pipe, the cover member having a radial width that is from 25-75% of the radial length of the vanes.
In accordance with the instant invention, there is also provided a separator for separating entrained particles from a fluid flow, the separator comprising a cyclone chamber having a cyclonic flow region, the cyclonic flow region having a center, a longitudinal axis, an outer peripheral portion, an inner portion and a radial width; means for introducing a fluid flow to the cyclone flow region for cyclonic rotation therein; separations means for creating a plurality of non-rotational flow regions positioned beneath the cyclonic flow region; particle receiving means disposed beneath the separations means for receiving particles separated from the fluid flow; and, means for removing the fluid flow from the cyclone flow region positioned above the particle receiving means.
In one embodiment, the cyclone chamber has a bottom spaced below the separation means and the particle receiving means is positioned between the bottom and the separation means.
In another embodiment, the separator further comprises means for removing particles separated from the fluid flow from the cyclone flow region positioned below the separations means.
In another embodiment, the separation means comprises cover means positioned in the inner portion of the cyclonic flow region and baffle means extending in the direction of the longitudinal axis of the cyclonic flow region and extending downwardly from the cover means.
In another embodiment, the baffle means are generally parallel to the longitudinal axis.
REFERENCES:
patent: 1797812 (1931-03-01), Waring
patent: 2542634 (1951-02-01), Davis et al.
patent: 2678110 (1954-05-01), Madsen
patent: 2811219 (1957-10-01), Wenzl
patent: 2846024 (1958-08-01), Bremi
patent: 2913111 (1959-11-01), Rogers
patent: 291
Conrad Wayne Ernest
Petersen Dave
G.B.D. Corp.
Smith Diane S.
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