CA1259573A - Adjustable syclone separator and process of using the same - Google Patents

Abstract

A B S T R A C T

ADJUSTABLE CYCLONE SEPARATOR AND
PROCESS OF USING THE SAME

The present invention relates to a process and apparatus for changing the pressure drop across an operating separator without terminating its operation or significantly reducing the efficiency of its separation. A stream of particle-suspending fluid which is less dense that the suspended particles is flowed tangentially into an upper portion of a generally cylindrical vortex chamber so that particles are separated by being moved radially outward and downward toward a bottom-located particle outlet while cleaned fluid is flowing upward toward a top-located outlet. m e pressure drop across the separator is increased or decreased by moving a vortex stabilizing means toward or away from the fluid outlet opening without interrupting the flow of fluid and particles within the separator.

Description

3 ~ 7~

ADJUSTABLE CYCLONE SEPARAIOR AND
PRCCESS OF USING I~E SAME

m e present invention relates to a cyclone separator for imparting a swirling and separating action to a stream of fluid.
More particularly, the invention relates to a method and apparatu~ for changing the magnitude of the pressure drop across S a cyclonic separator without materially restricting its separating efficiency. By changing the pressure drop, the cyclone acts also as an erosion resistant vortex valve.
A conventional cyclone separator is arranged for receiving tangential inflows of particle-suspending gaseous or liquid fluids to form a stabilized generally ver~ical vorteK so that separated solid or liquid particles are separated by being moved radially outward and dcwnward past a vortex stabilizer which is located at, or ~omewhat below, the natural turning point of the vortex. Such a location for a vortex stabilizer was thought to be needed in order to maintain an adequate dow~ward and outward expulsive force on the separated particles.
As far as applicant is aware, it was not previously recognized that, while inflowing and treating a particle-laden fluid in a cyclone separator, online changes can be made in the vertical length of the vortex without first terminating or ctherwise changing the rate or pressure at which the inflowing stream is provided. Applicant has discovered that when the vortex length is shortened by an upward movement of a vortex-stabilizer, the result is mainly an increase in the pressure drcp across the cyclone. The increased pressure drop increases the back pressure on the inflowing stream and thus can be used to throttle and/or divert the stream while causin~ only a minor reduction in the efficiency with which the suspended particles are separated.
The present inventio~ therefore relates to a method and apparatus for separating the components of and controlling the ~a 5'~

- 2 - 63293-2491 flow of a suspension composed of particles dispersed within a fluid having a density different from that of the particles.
More specificaJly, the i.nvention provides a process for separating a suspension of particles dispersed within a fluid having a density different from that of the particles comprising -the steps of: flowing a stream of said suspension tangentially into an upper portion of a generally cylindrical and vertical vor-tex chamber of a cyclone separator in which the vortex chamber contains an upper fluid outlet opening at or near the top of the said chamber and a lower fluid outlet opening at or near the bottom of the said chal~er and a vertically movable vortex stabilizer, so that the inflowing stream forms a vortex above the vortex stabilizerl said vortex stabilizer comprising a vertical pin or vortex finder; centrifugally and gravitationall.y moving the denser component of the suspension radially outward and downward to pro-vide an outflow of denser component-enriched fluid through the lower outlet opening while providing an outflow of denser component-depleted fluid through the upper outlet opening; and both changing the pressure drop across the cyclone separator and the proportion of fluid outflowing through the said upper and lower fluid outlet openings, by moving the said vor-tex stabi.l:izer comprising a vertical pin or vortex finder, toward or away f.rom the said upper fluid outlet opening by externally controllable means.
The invention also provides a cyclone separator compris-i.ng: a vertical cylindrical vortex chamber; means for flowing .~.

?~ I r~t'~
- 2a - 63293-2491 fluid containlng discontinuous and dispersed components having different phases and densi-ties tangentially into an upper portion of said chamber to form a vortex for causing the denser components to move radially ou-tward and downward relative to less dense components of the inflowing fluid; outlet means for denser com-ponents-depleted fluid at or near the top of said chamber; outlet means for denser components-enriched fluid at or near the opposite end of said chamber; and intermediately located vortex stabilizing means comprising a vertical pin or vortex finder, and movable mounted within said chamber in a location in which it is capable of stabilizing said vortex; and externally controllable means for moving said vortex stabilizing means comprising a vertical pin or vortex finder, toward or away from said fluid outlet means at or near the top of sa:id chamber and for adjusting the distance between the said stabilizing means and the said outlet means for denser components-depleted fluid.
The present invention is applicable to treatments of substantially any suspension susceptible to separation in a cyclone separator. The suspended particles can be solid, liquid or gaseous and the particle suspending fl.uid can be gaseous Or liquid as long as the pa:rticles are dispersed within a :E]ui.d which comprises a different phase and has a density which is clifferent from that of the particles.
Figure 1 is a diagrammatic elevation of a test loop used in testing the apparatus of the present invention.

~5'.~5~73 - 2b - 63293-2491 Figure 2 is a diagrammatic elevation of one embodiment of a cyclone separator of the present invention.
The present invention provides a method and apparatus involving discoveries and/or features such as the following:
(l) the separation performance of a cyclone separator can be optimized while the separator is on stream by vertical adjustments of a movable vortex stabilizer, (2) the pressure drop through a plurality of cyclone separators which are connected in parallel through a manifold can be similarly adjusted to equalize ~>~3~ ~'3 the flow through each separator or to terminate or to reduce the flow through a particular separator, (3) the outflow from a cyclone separator cutlet may be similarly closed-off ccmpletely to terminate a flow of a fluid without any downstream valve, (4) a novably m~unted vortex stabilizer can be adjusted to control the amcunt of fluid leaving the separator as a fluid in which a dense component is either enriched or depleted, (5) a cyclone separator of the present invention is particulary a~vantageous for controlling gas or liquid recycle streams which are relatively enriched or depleted of solid par~icles that are both abrasive and more or less dense than the gas or liquid in which they are dispersed.
A cyclone separator uses the centrifugal forces in a confined, high velocity vortex to separate phases of different densities. The strength and stability of the vortex are of prinary importance in determining both separation efficiency and erosion resistance of a cyclone. Since improved cyclone reliability, separatio~ performance, and erosion resistance are extremely important commercial objectives, studies were undertaken to achieve cyclone modifications which might reduce erosion and improve efficiency. In particular, studies were made of cyclone internals which contained means for stabilizing the vortex. The term "stabil~zed", is used to mean that the vortex was held in the centre of the cyclone and that the turbulent energy dissipation was reduced.
Nunerous cyclone flow, velocity, acoustical, and pressure drop experiments were performed at near ambient conditions. Most of these experiments were done with a 0.5 m diameter, tangential inlet cyclone which was a ~31 scale PLEXIGLAS model of a second stage FCC commercial cyclone. The scale of the model was chosen to simulate the Reynolds and Strouhal nu~bers of an actual fluid cracking catalyst (FCC) cyclone at a similar Lnlet velocity (25m/sec). The model was tested with and without vortex stabilizers of various configurations. Wall roughness was simwlated by a lO mesh, O.ll cm "thick" wire screen closely 9r~73 fitted to the inside walls of the cyclone. This model is typical of cyclones used in modern catalytic cracking units, except that it is a particularly high efficiency design. The distinguishing features of such a design are a large inlet to outlet area ratio, narrow inlet, and long cyclone body.
Many variations of the basic cyclone were tested to determine the effects of hopper gecmetry, stabilizer geo~etry, and wall roughness on the vortex motion in cyclones.
All experiments used air (to simulate gaseous hydrocarbons) as the main flaw. The air was supplied by three 300 kW blc~ers, having a total capacity of one stan Prd m3/sec. Most of the exFeriments were done with about 0.6 m3/sec at 117 kPa. This flow rate corresponds to an inlet velocity of 17 m/sec. At this flc~
rate, the Reynolds number based on the outlet tube diameter (Rez = pgwiri~) was approximately 2.8 x 10 . At such a high Reynolds number the velocity profiles are essentially independent of the flcw rate, therefore, ~he actual flow rate was allowed to vary sc~Ewhat, but all measurements were taken at flow rates above 0.5 m3/sec at 110-130 kPa, 16-29C. For purposes of cc~parison, the velocity profiles were all adjusted to an inlet velocity of 17 mlsec.
Cyclones are characterized by large radial pressure gradients which balance the centrifugal forces in the swirling flow. Therefore, there is a relative vacuu~ at the centre, or core, of the vortex. This low pressure core would presumably "suck" on any nearby surface, thus stabilizing an attachment of the vortex to that surface.
Vortex stabilizer means were placed in the model cyclone to forestall the unsteady motion of the vortex.
A vertical pin or vortex finder may be added to the stabilizer to restrict and centre the lateral precessional motion of the vortex. It was found that a 0.6 cm diameter stabilizer pin was insufficient to restrict the vortex precession in the test cyclc~ne. The vortex stabilizer was more effective w~len a larger ~ ~ r r ~ 7 3 s --pin was used to centre the vortex. A 1.9 cm diameter rod was test~d with better results.
Several types of vortex stabilizer means were tested wi~h varying results. Generally, a flat plate or circular disc was found to be satisfactory. m e vortex stahilizer means diameter should ~e at least about one vortex outlet tube diameter. The maxi ~ stabilizer dlameter in a ccmmercial model is set primarily by weight limitations and is limited only by providing an annulus between the perimeter of the stabilizer and the vessel wall large enough to permit catalyst to flow downwardly while sim~ltaneously pass mg stripping gas in an upwardly direction.
The vortex finder is not critical to cyclone performance prc~ided the vortex stabilizer means are located a short distance from the vortex outlet, i.e., at least about 2-3 vortex outlet tube dia~eters. Hcwever, if the vortex finder is located at a greater distance, say 5-8 vortex outlet tube diameters, then it is preferred that the vortex stabilizer means contain a vortex finder. Preferably, such a vor~Jex finder would be greater than about one-third the vortex length.
Based on aerodynamic studies, vortex stabilization appears desirable for increasing separation efficiency while minimizing both pressure loss and erosion. Vortex stabilizers reduced the pressure drop across the m~del cyclone by 10-15% even though the peak swirl ve:Locities were significantly increased. This behaviour is exceptional in cyclones since increasing swirl almost always raises the pressure loss. As the pressure drop goes down, vortex stabilization seems to re~uce the turbulent energy dissipation in cyclones.
A test loop was constructed of PLE~IGLAS as shown in Figure 1. Catalyst enters the bottom of a 8 cm x 4.3 m riser 10 and is transported by air which enters through a concentric 0.04 m nozzle 11. m e differental pressure (~P) 12 across the riser was not measured precisely, but was on the order of 0.25 KPa. Air flow rates of 1.8 to 2.9 Nm3 were used in the riser 10. These rates correspond to superficial velocities in the riser 7.2 to ~,135'7~
-- 6 ~
11.5 m/sec. Measure~ent of air rate was via rotc~eter. Catalyst flow rates in the riser were varied frcm 2 to 9 kg/minute.
Control of solids flc~ rate was by setting a pinch clamp 13 in a 0.076 m diameter standpipe 14 between the catalyst hold tank 15 and the riser 10. The catalyst rate was measured by elosing a pineh elamp 16 between the stripper eyclone 17 and the eatalyst hold tank 15 and measuring the rate of level increase in the stripper c~clone body. For this measurement air was turned off to the stripper cyclone 17 and a catalyst density of 0.8 g/cm3 was assumed.
At the top of the riser 10 there is a right angle turn 18 and a transition 19 from a 0.076 m pipe to a 0.152 m high x 0.04 m wide rectangular tangential cyclone inlet 31 (58 x 10 4 m2)~ Gas velocities at the eyclone inlet were varied fram 5.2-8.4 mlsee.
Gas exits from the stripper cyclone 17 via a 0.076 m pipe 20. A secondary cyelone 21 eollects the catalyst frc~n the stripper eyclone overhead. A paper filter 22 allc~ws clean gas to pass to the atmosphere and catehes eatalyst which eseapes frcm the seeondary eyclone.
Catalyst exits from the stripper eyelone 17 through a standpipe 23. A pineh elamp 16 is used to control the eatalyst level in the bottc~n of the stripper eyelone 17. A eatalyst hold tank 15 below the stripper eyelone 17 provides a reservoir whieh feeds the riser through a 0.076 m standpipe 14.
A detailed diagrammatie elevation view of the stripper cyelone 17 is shc~n in Figure 2. The eyelone zone 24 was made from a 0.142 m inside diameter (ID) pipe and containecl a vortex finder 25 and a vortex stabilizer 26 located a selected clistanee from the bottom of the elean gas c~utlet pipe 20. me stripping zone 27 was also made fram a 0.142 m ID pipe. The elean gas c~utlet 20 was a 0.076 m ID pipe with 0.3 em wall thiekness and extended 7 inches through swirl-indueing zone 30 to the tap of the cyelone zone 24. m e catalyst or separated ecmponent outlet 23 was 0.076 m ID pipe. m e partiele-laden gas enters the swirl zone 30 through the tangential inlet 31.

9~ 3 The vortex stabilizer 26 was 10.2 cm in diameter (for most of the tests), 1.27 cm thick at the edge and 2.5 om thick in the centre. me vortex finder 25 was 6.4 cm long, 1,27 cm diameter at the base and 0.635 cm diameter at the top.
In the embodlment shown in the drawing, the vortex stabiliæer 26 is provided with a skirt tube 35 which Æ ounds a guide tube 36. Seal rings 37 are arranged to prevent the flow of fluid between the tubes 35 and 36. m e vortex stabilizer 26 is vertically movable by means of a rack and pinion drive gear arrangement 38. The drive g~Ar shaft is supported by bearings 39, is Æ ounded by a seal ring 37, and is provided with a handle or drive 40 which can be operated frcm a location outside of the cyclone separator.
E~MPLE
Tests such as those conducted in apparatus of the type shown using gaseous suspension of solid particles have demonstrated the dependence of the pressure drop across a cyclone separator on the location of the vortex with respect to the upper, particle-depleted fluid outlet. In a test m a cyclone separator having a 51 cm diameter vortex zone, the vortex length was varied between 91 cm and 43 cm. The sus$ension of particles was inflcwed at an inlet pressure of 117 Pa gauge. With the vortex length of 91 cm the pressure drop fram the inlet opening to a particle-depleted fluid outlet opening was 21 Pa and the pressure drop from the inlet to the particle-enriched fluid outlet was 12 Pa. When the vortex length was 43 cm, the pressure drop from the inlet to the particle-depleted fluid outlet was increased to 72 Pa, although the pressure drop to the particle-enriched fluid outlet was still above 12 Pa. In those tests, the flow split was changed by a factor of about 2 even though the underflow of particle-enriched fluid was not contained within the cyclone separator.
Where the flow of the particle-enriched fluid is contained within the cyclone separator, so that there is no fluid outflow, the m~vement of the vorte~ stabilizer toward the particle-depleted fluid outlet can increase the pressure drop across the 5~3S~3 ~ 8 --cyclone separator to a point at which the flow is terminate~. Insuch an operaticn the cyclone separator is operating as a valve.
Where the inflowing fluid contains suspended solid particles that are apt to erode the seats of the valve, the present apparatus is particularly advantageous. Tests in systems of the type shown have indicated that, in a cyclone separator there is little, if any, we æ on the vortex stabilizer, even when the vortex stabilizer is quite close to the particle-depleted fluid outlet.
miS is due to the fact that the particles which could cause an abrasion are continually thrown radially outward by the cyclonic action, so that substantially the only fluid flcwing along the Æ faces of the vortex stabilizer or the adjacent edges of the particle-depleted fluid outlet are subst~ntially free of such particles.
1~ In a coal gasification process produced gases which contain suspended particles of unreacted coal and/or fly-ash are desirably cooled by diluting them with a stream of clean recycle gas. The present cyclone separator is particularly well suited for use as an erosion resistant valve for controlling such an operation. Most valves tend to be severely eroded by suspended solids at the elevated pres Æ es and temperatures ccmmonly ~ loyed for coal gasification. With the present cyclone separator the solids-laden reaction product can be flowed tangentially so the contam mating solids are spun outward as they would be in an ordinary cycloneO But, with the present sysb~m, the flow of the relatively clean recycle gas through the upper outlet can be controlled by simply vertically moving the vortex stabilizer to cause the cyclone separator to act as a vortex valve while also causing the cont~lminated solids to be carried down and out in a particle-~nriched gas stream.
Where large volumes of solid particles suspended in large volumes of gas are to be separated, such as is ccmmon in catalytic cracking and various other manufacturing processes, pluralities of cyclones separators are often operated in parallel, with each separator being connected to receive a porti,~n of a solids-laden stream from a manifold, with the separated solids ~ ~ ~rj~573 g being discharged into a ccmmon hopper. For example, it is common for 8 cyclone separators to be manifolded together to receive catalyst-laden flue gas from a regenerator. In such operations it is difficult to feed all of the cyclones equally and collected solids from sGme of them are apt to flow through the hopper and back into flue gas flowing through other cyclones. However, when using the present cyclone separators the vortex stabilizers can be adjusted, without interrupting the operation, in order to control the flow split between the separators operating in parallel.
In general, the present invention is useful in separating solids, liquids or gaseous particles which are dispersed in a gaseous or liquid fluid having a density different from that of the particles. m e present process may be used to control the flow split between the underflow and overflow of either particle-depleted or particle-enriched fluid. Particularly in a situation where the underflow is contained in a chamber below the vortex chamber of the separator, the present invention can be used as a valve for controlling the flow of a fluid containing abrasive particles by altering the pressure drop through the cyclone separator or termlnating the flow in a manner that avoids any substantial erosion due to abrasion.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for separating a. suspension of particles dispersed within a fluid having a density different from that of the particles comprising the steps of:
flowing a stream of said suspension tangentially into an upper portion of a generally cylindrical and vertical vortex chamber of a cyclone separator in which the vortex chamber contains an upper fluid outlet opening at or near the top of the said chamber and a lower fluid outlet opening at or near the bottom of the said chamber and a vertically movable vortex stabilizer, so that the inflowing stream forms a vortex above the vortex stabilizer, said vortex stabilizer comprising a vertical pin or vortex finder;
centrifugally and gravitationally moving the denser component of the suspension radially outward and downward to provide an outflow of denser component-enriched fluid through the lower outlet opening while providing an outflow of denser component-depleted fluid through the upper outlet opening; and both changing the pressure drop across the cyclone separator and the proportion of fluid outflowing through the said upper and lower fluid outlet openings, by moving the said vortex stabilizer comprising a vertical pin or vortex finder, toward or away from the said upper fluid outlet opening by externally controllable means.

2. A cyclone separator for carrying out the separating process as claimed in claim 1, comprising:
a vertical cylindrical vortex chamber;
means for flowing fluid containing discontinuous and dispersed components having different phases and densities tangentially into an upper portion of said chamber to form a vortex for causing the denser components to move radially outward and downward relative to less dense components of the inflowing fluid;

outlet means for denser components-depleted fluid at or near the top of said chamber; outlet means for denser components-enriched fluid at or near the opposite end of said chamber;
an intermediately located vortex stabilizing means comprising a vertical pin or vortex finder, and movable mounted within said chamber in a location in which it is capable of stabilizing said vortex; and externally controllable means for moving said vortex stabilizing means comprising a vertical pin or vortex finder, toward or away from said fluid outlet means at or near the top of said chamber and for adjusting the distance between the said stabilizing means and the said outlet means for denser components-depleted fluid.

3. A process for operating a plurality of cyclone separators connected in parallel so that they each receive a portion of a stream comprising a suspension of particles within a fluid having a density different from that of the suspended particles comprising:
connecting at least one cyclone separator apparatus of the type defined by claim 2 as at least one of said parallel connected cyclone separators; and moving at least one movable vortex stabilizer within at least one of said parallel connected cyclone separators into a position causing the rate of outflow through at least one fluid outflow opening of each of said parallel connected cyclone separators to substantially equal that of at least one other of said parallel connected cyclone separators.

4. A process for optimizing the performance of a cyclone separator of the type defined by claim 2 comprising moving said vortex stabilizing means into a position relative to the uppermost fluid outlet in which more of the suspended particles are separated from the inflowing fluid than are separated from that fluid when the vortex stabilizing means is located differently and the pressure applied to inflowing fluid is substantially the same.

5. A process as claimed in claim 1 in which the outflow of fluid through the upper outlet is substantially terminated by moving the vortex stabilizer toward that outlet without significantly increasing the pressure applied to displace fluid through the cyclone separators.

6. A process as claimed in claim 5 in which the inflowing fluid comprises a particle-suspending gas produced in a coal gasification process.

7. A gaseous as claimed in claim 1 in which the inflowing fluid is a gaseous suspension of solid particles.

8. A process as claimed in claim 1 in which the inflowing fluid is a liquid suspension of droplets of liquid that is less dense than the suspending liquid.

9. A process as claimed in claim 1 in which the inflowing fluid is a gaseous suspension of droplets of liquid that is denser than the gas.

10. A process as claimed in claim 1 in which the inflowing fluid is a liquid suspension of solid particles that are more dense that the liquid.