Gas separation – Multiple separators – each with discrete and longitudinally... – Centrifugal
Reexamination Certificate
2001-06-20
2003-07-22
Reifsnyder, David A. (Department: 1723)
Gas separation
Multiple separators, each with discrete and longitudinally...
Centrifugal
C055S428000, C055S459100, C055SDIG003, C210S512100, C209S719000
Reexamination Certificate
active
06596046
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an improved apparatus for separating a component from a fluid stream. In one embodiment, the fluid may be a gas having solid and/or liquid particles and/or a second gas suspended, mixed, or entrained therein and the separator is used to separate the particles and/or the second gas from the gas stream. In an alternate embodiment, the fluid may be a liquid which has solid particles, and/or a second liquid and/or a gas suspended, mixed, or entrained therein and the separator is used to remove the solid particles and/or the second liquid and/or the gas from the liquid stream. The improved separator may be used in various applications including vacuum cleaners, liquid/liquid separation, smoke stack scrubbers, pollution control devices, mist separators, an air inlet for a turbo machinery and as pre-treatment equipment in advance of a pump for a fluid (either a liquid, a gas or a mixture thereof) and other applications where it may be desirable to remove particulate or other material separable from a fluid in a cyclone separator.
BACKGROUND OF THE INVENTION
Cyclone separators are devices that utilize centrifugal forces and low pressure caused by spinning motion to separate materials of differing density, size and shape.
FIG. 1
illustrates the operating principles in a typical cyclone separator (designated by reference numeral
10
in
FIG. 1
) which is in current use. The following is a description of the operating principles of cyclone separator
10
in terms of its application to removing entrained particles from a gas stream, such as may be used in a vacuum cleaner.
Cyclone separator
10
has an inlet pipe
12
and a main body comprising upper cylindrical portion
14
and lower frusto-conical portion
16
. The particle laden gas stream is injected through inlet pipe
12
which is positioned tangentially to upper cylindrical portion
14
. The shape of upper cylindrical portion
14
. and frusto-conical portion
16
induces the gas stream to spin creating a vortex. Larger or more dense particles are forced outwards to the walls of cyclone separator
10
where the drag of the spinning air as well as the force of gravity causes them to fall down the walls into an outlet or collector
18
. The lighter or less dense particles, as well as the gas medium itself, reverses course at approximately collector G and pass outwardly through the low pressure centre of separator
10
and exit separator
10
via gas outlet
20
which is positioned in the upper portion of upper cylindrical portion
14
.
The separation process in cyclones generally requires a steady flow free of fluctuations or short term variations in the flow rate. The inlet and outlets of cyclone separators are typically operated open to the atmosphere so that there is no pressure difference between the two. If one of the outlets must be operated at a back pressure, both outlets would typically be kept at the same pressure.
When a cyclone separator is designed, the principal factors which are typically considered are the efficiency of the cyclone separator in removing particles of different diameters and the pressure drop associated with the cyclone operation. The principle geometric factors which are used in designing a cyclone separator are the inlet height (A); the inlet width (B); the gas outlet diameter (C); the outlet duct length (D); the cone height (Lc); the dirt outlet diameter (G); and, the cylinder height (L)
The value d
50
represents the smallest diameter particle of which 50 percent is removed by the cyclone. Current cyclones have a limitation that the geometry controls the particle removal efficiency for a given particle diameter. The dimensions which may be varied to alter the d
50
value are features (A)-(D), (G), (L) and (Lc) which are listed above.
Typically, there are four ways to increase the small particle removal efficiency of a cyclone. These are (1) reducing the cyclone diameter; (2) reducing the outlet diameter; (3) reducing the cone angle; and (4) increasing the body length. If it is acceptable to increase the pressure drop, then an increase in the pressure drop will (1) increase the particle capture efficiency; (2) increase the capacity and (3) decrease the underflow to throughput ratio.
In terms of importance, it appears that the most important parameter is the cyclone diameter. A smaller cyclone diameter implies a smaller d
50
value by virtue of the higher cyclone speeds and the higher centrifugal forces which may be achieved. For two cyclones of the same diameter, the next most important design parameter appears to be L/d, namely the length of the cylindrical section
14
divided by the diameter of the cyclone and Lc/d, the length of the conical section
16
divided by the width of the cone. Varying L/d and Lc/d will affect the d
50
performance of the separation process in the cyclone.
Typically, the particles which are suspended or entrained in a gas stream are not homogeneous in their particle size distribution. The fact that particle sizes take on a spectrum of values often necessitates that a plurality of cyclonic separators be used in a series. For example, the first cyclonic separator in a series may have a large d
50
specification followed by one with a smaller d
50
specification. The prior art does not disclose any method by which a single cyclone may be tuned over the range of possible d
50
values.
An example of the current limitation in cyclonic separator design is that which has been recently applied to vacuum cleaner designs. In U.S. Pat. Nos. 4,373,228; 4,571,772; 4,573,236; 4,593,429; 4,643,748; 4,826,515; 4,853,008; 4,853,011; 5,062,870; 5,078,761; 5,090,976; 5,145,499; 5,160,356; 5,255,411; 5,358,290; 5,558,697; and RE 32,257, a novel approach to vacuum cleaner design is taught in which sequential cyclones are utilized as the filtration medium for a vacuum cleaner. Pursuant to the teaching of these patents, the first sequential cyclone is designed to be of a lower efficiency to remove only the larger particles which are entrained in an air stream. The smaller particles remain entrained in the gas stream and are transported to the second sequential cyclone which is frusto-conical in shape. The second sequential cyclone is designed to remove the smaller particles which are entrained in the air stream. If larger particles are carried over into the second cyclone separator, then they will typically not be removed by the cyclone separator but exit the frusto-conical cyclone with the gas stream.
Accordingly, the use of a plurality of cyclone separators in a series is documented in the art. It is also known how to design a series of separators to remove entrained or suspended material from a fluid stream. Such an approach has two problems. First, it requires a plurality of separators. This requires additional space to house all of the separators and, secondly additional material costs in producing each of the separators. The second problem is that if any of the larger material is not removed prior to the fluid stream entering the next cyclone separator, the subsequent cyclone separator typically will allow such material to pass therethrough as it is only designed to remove smaller particles from the fluid stream.
SUMMARY OF THE PRESENT INVENTION
In accordance with one embodiment of the instant invention, there is provided a non-frusto-conical cyclone separator comprising a longitudinally extending body having a wall, the wall having an inner surface and defining an internal cavity within which a fluid rotates when the separator is in use, at least a portion of the inner surface of the wall configured to continuously impart changes in the rate of acceleration to the fluid as it rotates within the cavity.
In accordance with another embodiment of the present invention, there is provided a non-frusto-conical cyclone separator comprising a longitudinally extending body having a longitudinally extending axis and a wall, the wall having an inner surface and defining an internal cavity within which a fluid rotates when the separator is in use, a
Conrad Helmut Gerhard
Conrad Wayne Ernest
Szylowiec Ted
G.B.D. Corp.
Reifsnyder David A.
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