Abrasive wear barrier

Details Abrasive wear barrier Abrasive wear barrier

1998-06-26

2001-07-31

Smith, Duane S. (Department: 1724)

Gas separation: processes

Deflecting

Centrifugal force

C055S337000, C055S435000, C055S459100

Reexamination Certificate

active

06267803

ABSTRACT:

FIELD OF INVENTION
This invention relates to cyclone separators, specifically to an improved way of preventing abrasive wear caused by the operation of cyclone separators.
BACKGROUND OF THE INVENTION
In the operation of a cyclone separator, a gas/particulate stream channels tangentially into a cyclone barrel. The circular shape of the barrel imparts a spinning, vortexed flow pattern to the gas/particulate mixture. The gas/particulate mixture travels first to the walls of the barrel, then down along the conical section to the dust outlet. The conical shape of the cyclone separator increases the velocity of the gas/particulate mixture until a vortex is reached and particle free gas starts to rotate up in an inner air column. The high tangential velocity and the decreasing radius of the path create a substantial centrifugal force. This centrifugal force separates the dust from the gas stream due to the difference in density. The particulate exits at the bottom of the separator through a dust port. The gas exits through a gas outlet pipe at the top of the cyclone separator. The effect of the unmitigated flow of hot gas and particles is erosion to the material comprising the barrel walls and cylinder.
Erosion takes place as a result of the impact of the gas borne particles. The particles strike the inner wall of the cyclone separator at a high velocity and scrape along the wall causing wear until friction consumes the kinetic energy of the particle and gravity causes the particle to drop into the collector.
Temperatures inside the cyclone range from 700 degrees to 900 degrees Fahrenheit. Humidity can be between 5% to 30%. The particle size can vary between 20 microns to 150 microns. The velocity of the incoming particulate ranges between 100 feet per second to 200 feet per second. These factors have made it difficult to provide suitable protection to the inner wall of the separator.
Liners on the cyclone walls have been used to mitigate the effect of the abrasive particulate and provide some protection to the inner wall. Variable environmental conditions contribute to the suitability of various liners. Material used to protect the walls of the cyclone must withstand the harsh conditions present within the cyclone separator.
It has been known to use hardplate steel and ceramic tile as liners to protect the inner wall. However, the hardplate wears quickly and causes downtime to the cyclone separator for necessary replacement. The ceramic tile wears relatively well, but adhesion problems are experienced due to the thermal cycling of the separator. During use, the separator reaches up to 900 degrees Fahrenheit. It then cycles back to room temperature when idle. This thermal cycling causes the adhesion to fail and the tiles become detached from the inner wall, leaving the parent metal of the inner wall exposed.
OBJECTS AND ADVANTAGES
Accordingly, several objects and advantages of this invention are to provide a protective barrier to increase the durability of the walls of a cyclone separator. Specifically a barrier that facilitates a buildup of particulate fines that act as an protective layer to mitigate the erosive effects of a hot, high velocity, gas/particulate mixture.
Another object of this invention is provide a device that facilitates the buildup of particulate fines in a cyclone generator in a manner that does not create blocking or impede the action of the separator in any other way.
Still another object of this invention is to provide a simple, low maintenance method of prolonging the life of the parent metal comprising a cyclone separator wall.
Still further objects and advantages will become apparent from a consideration of the ensuing description and accompanying drawings.
SUMMARY OF THE INVENTION
The primary purpose of this invention is to provide a means to prevent erosion of the parent metal comprising the cyclone barrel and cone of a cyclone separator; specifically, the parent metal comprising the inner wall of a cyclone separator. This is accomplished through the use of a barrier of expanded metal shaped to the contour of the inner wall of the cyclone. The barrier is effective at a critical spacing from the parent metal of the cyclone wall. When the barrier is correctly spaced from the inner cyclone wall, a buildup of particulate accumulates in front of the parent metal comprising the cyclone barrel and cone. This buildup of particulate matter acts as a cushion and shield from subsequently incoming particulate matter, which travels at high speeds as it enters the cyclone separator. The high energy incoming particles strike the barrier of accumulated particulate instead of the parent metal. The accumulated particulate absorb the impact of the kinetic particles preventing the kinetic particles from striking the inner cyclone wall. The erosive effect of the incoming particles on the inner wall of the cyclone separator is thereby mitigated. In addition, the striking particles tend to embed in the accumulated particulate instead of scraping along the wall, further reducing the erosion of the inner cyclone wall. Once all of the kinetic energy has been consumed, gravity pulls the particles downward into the collector.
This invention uses the incoming particulate matter itself to form a protective barrier against the eroding factor of the continuous stream of incoming particles. The expanded metal guard is used to facilitate the necessary accumulation of incoming particulate that forms the protective barrier.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the preferred embodiment, expanded metal is secured along the inner walls of a cyclone separator barrel at a fixed distance from the inner wall generally following the contour of the cyclone separator.
FIG. 1
shows a cutaway view of a cyclone separator. Hot gases carrying particulate matter or fines, and forming a gas/particulate mixture
13
; enter the cyclone input
7
channeling tangentially into
10
the cyclone barrel. The circular shape of the barrel imparts a spinning, vortexed flow pattern to the gas/particulate mixture. The gas/particulate mixture travels first to a wall created by the barrel and expanded metal secured to the inner barrel wall. Initially the dust and particulate will pass through the openings in the expanded metal and form a buildup of particulate between the barrel wall and the expanded metal. This build up will increase until a protective layer of particulate is formed that spans between the inner wall and the expanded metal. After the particulate layer is formed, the subsequent incoming particles will strike the layer and then proceed down to a conical shaped transition barrel
11
.
The conical shape of the cyclone barrel increases the velocity of the gas/particulate mixture until a vortex is reached, and the gas, free from particles, begins to rotate up in an inner air column through the cyclone barrel to exit through a gas outlet pipe
9
. The particulate
12
exists through the bottom of the cyclone separator through a dust port
8
.
FIG. 2
shows a cutaway of a cyclone separator barrel
1
, exposing the expanded metal
2
lining the barrel.
FIG.
3
and
FIG. 4
show the proximity of the expanded metal
2
to the cyclone separator barrel
1
and a bolt
4
. Bolt
4
is secured to the inner wall of the cyclone separator barrel
1
A by a rigid means such as welding. Bolt
4
in conjunction with a washer and a nut, in turn secures expanded metal
2
to the barrel.
FIG.
3
and
FIG. 4
also illustrate the penetration of particulate matter
3
through an opening in expanded metal
2
as the kinetic particulate matter travels in a spinning motion indicated by arrow
3
B.
FIG. 4
shows the particulate matter
3
built up along the inner wall of the cyclone separator barrel
1
A, forming a protective barrier
3
A, comprised of generally stationary particulate matter. Once formed, the protective barrier insulates the inner wall from the erosive action caused by the impact of incoming particulate matter.
FIG. 5
shows how bolt
4
can be rigidly attached via a filet weld
16
to the inner wall
1
A of

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