Abstract:
A cyclone for high temperature applications where the outlet pipe is vertically hung, properly located, and sealed over the vessel outlet opening without the need for bolts, so as to allow dimensional growth due to thermal expansion without failure-causing stresses induced on welds.

Description:
BACKGROUND OF THE INVENTION 
     Cyclone separators are typically found in applications which require the removal of particulates from a fluid stream. This fluid stream may be a liquid such as water, or it may be a gas such as air. Cylones are very useful for pollution control applications, removing particulate matter from exhaust gases before these gases are directed to baghouses or scrubbers or are discharged directly to the atmosphere. 
     Many exhaust gas applications operate at high temperatures such that the cyclone itself is exposed to these high temperatures. Thus, the cyclone experiences dimensional growth due to thermal expansion. It is desirable to be able to operate at these high temperatures, sometimes in excess of 1,500° F., while maintaining a relatively cool skin temperature below 650° F. so that inexpensive materials of construction, such as carbon steel, may be used for the vessel body of the cyclone. In order to accomplish this, it is industry standard to utilize refractory material, such as Vibecast refractory, lining the inside of the cyclone vessel body. 
     While the use of the refractory allows the high temperature operation while maintaining a much cooler cyclone vessel body, it causes a problem when it comes to connecting the cyclone outlet pipe, operating at this higher temperature, to the much cooler cyclone vessel body. In the prior art, a bolted, flanged connection has been made between the outlet pipe and the cyclone vessel body, with a gasket to seal the gap between the two flange faces. This unyielding connection does not allow for relative movement between the outlet pipe and the cyclone vessel body. Since this relative motion must occur due to the differences in thermal expansion between the outlet pipe and the cyclone vessel body, the result is very high induced stresses on the welds as well as on the bolts, resulting in eventual failure, requiring down time and expense to repair and replace the damaged parts. The severe operating conditions also tend to cause the nuts to become frozen onto the bolts, making it very difficult to remove and replace a worn outlet pipe. These difficulties have generally limited operation of the cyclones to temperatures in the range of 1,600° F. to 1,800° F. 
     SUMMARY OF THE INVENTION 
     The present invention provides an arrangement for mounting the outlet pipe onto the vessel body of a cyclone operating at very high temperatures, without experiencing the failures and limitations present in the prior art. The present invention eliminates the use of flanges or bolts, substantially reduces the thermal-expansion-induced stresses on the welds, and allows operation at temperatures well in excess of 1800° F. In fact, this present invention will allow operation of the cyclone in a coke calciner application where the exhaust gases entering the cyclone are at temperatures in excess of 2,250° F. 
     The present invention provides for nesting of the outlet pipe into an opening in the vessel body so that the weight of the outlet pipe keeps the pipe in place and there is no need for bolts. The preferred frustro-conical shapes of the nesting surfaces properly center and locate the outlet pipe, and the contact surface area between the two parts is generally sufficient to seal the surfaces without the need for gaskets, although a gasket can be used if desired. This connection permits relative expansion and contraction of the vessel and the outlet pipe without affecting the connection or seal between the parts. It also results in a simpler, faster installation with no bolts, quick and automatic location of the outlet pipe in the outlet opening, and easy removal and replacement of the outlet pipe without the need to remove or install bolts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic sectional view of a typical cyclone; 
     FIG. 2 is a enlarged, broken away, sectional view of the area securing the outlet pipe to the cyclone body in the prior art; 
     FIG. 3 is a detailed, enlarged view of the connection between the outlet pipe and vessel body of FIG. 2; 
     FIG. 4 is a detailed, enlarged view of a preferred embodiment of the connection between the outlet pipe and vessel body of the present invention; and, 
     FIG. 5 is a perspective, exploded, partially broken away view of a cyclone made in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a schematic sectional view of a typical cyclone  2 . The particulate laden fluid stream enters via the tangential inlet pipe  4  and swirls inside the vessel body  10  of the cyclone  2 . The particulates are thrown against the wall of the cyclone  2  and fall to the bottom to be expelled via the particulates discharge pipe  6 . The fluid stream eventually turns up to travel inside the swirling vortex and exits via the outlet pipe  8 . 
     FIG. 2 shows the connection between the cyclone vessel body  10  and the outlet pipe  8  as taught in the prior art for high temperature applications. A more detailed and enlarged view of this connection is shown in FIG.  3 . The outlet pipe  8  has a flange  14  welded to its outside surface. Gussets  16  reinforce the flange  16  to the outlet pipe  8 , and lifting holes  18  are used to aid in the installation of the outlet pipe  8 . 
     A projection  12  from the vessel body  10  may extend above and beyond the height of the outlet pipe  8 , boxing in the outlet pipe  8  and serving as an exhaust manifold. However, for the purposes of the present invention, it does not matter what other connections or enclosures there may be at the outlet of the outlet pipe. The concern is how the outlet pipe is connected to the vessel body. 
     A collar  20  is welded at one end to the vessel body  10 , and terminates at the other end with a flange  22 , which mates to the flange  14  on the outlet pipe  8 . A gasket  24  is inserted between the mating flanges  14 ,  24 , and bolts  26  and nuts  28 , arranged in a bolt-hole pattern, secure the outlet pipe  8  to the vessel body  10  of the cyclone  2 . Insulation  30  lines the inside walls of the cyclone  2  to help keep the skin temperature of the vessel body  10  at a relatively cool 650° F. or below, while the exhaust gas temperatures reach between 1,600° F. and 1,800° F. 
     Differences in dimensional growth due to thermal expansion cause severe stresses to this design, particularly at the welds where the collar  20  is secured to the vessel body  10  and to the mating flange  22 , as well as to the bolts and the weld securing the flange  14  to the outlet pipe  8 . 
     FIGS. 4 and 5 illustrate a preferred embodiment of the present invention. In this embodiment, the cyclone  102  includes a vessel body  110 , an inlet  104 , and an outlet pipe  32 . The outlet pipe  32  has a frustro-conical, tapered outer surface portion formed by an inverted skirt (or funnel)  34  fixedly secured, as by welding along the line  35 , to the outside surface of the outlet pipe  32 , such that the angle a between the vertical axis of the outlet pipe  32  and the funnel  34  is a small angle a, preferably in the range of 7° to 23°, with the most preferred angle a being 15°. The taper is such that the outer surface portion  34  extends from a narrower outside diameter at the bottom to a wider outside diameter at the top. Gussets  36  preferably are welded to the outlet pipe  32  and to the skirt or funnel  34  and serve to reinforce the skirt  34 . Holes  38  are formed in the gussets  36  and provide a place to hook into the outlet pipe  32  to lift it for installation into and removal from the cyclone  102 . While the tapered outer surface portion of the outlet pipe  32  is provided by adding the skirt or funnel  34 , this tapered outer surface portion could also be achieved by tapering all or part of the outlet pipe  32  itself. 
     Looking now at the cyclone vessel  110 , a collar  42  has a second end fixedly secured, as by welding, to the vessel body  110  at an angle β from the vertical that is larger than the angle a between the tapered outer surface portion of the outlet pipe  32  and the vertical. This angle β is preferably in the 15° to 45° range, with the most preferred angle β being 30°. The first end  44  of the collar  42  is beveled at an angle, so that the beveled edge tapers downwardly from its largest diameter to its smallest diameter. When the collar  42  is installed on the vessel  110 , the angle of the beveled edge  44  is the same as the angle of the tapered outer surface  34  of the outlet pipe  32 , such that, when the outlet pipe  32  comes to rest against this beveled first end or upper edge  44  of the collar  42 , the outer surface  34  of the outlet pipe  32  mates with the first end or upper edge  44  of the collar  42  to form a good metal-to-metal seal. While the collar  42  in this embodiment is welded to the vessel body  110 , it could alternatively be formed as an integral part of the vessel body  110 . The upper edge  44  of the collar  42  forms the upper opening in the vessel  110 , which is sealed by the outlet pipe  32 , so that gases must exit the vessel  110  through the outlet pipe  32 . While experimentation has shown that the metal-to-metal seal between the tapered outer surface  34  of the outlet pipe  32  and the upper edge  44  of the collar  42  is sufficient, a gasket may be placed between those two surfaces if deemed necessary or desirable. 
     The first end  44  of the collar  42  is thicker than the second end  46 . The greater thickness of the first end  44  allows for more contact surface area with the tapered outer surface  34  of the outlet pipe  32 , in order to obtain a better seal. The smaller thickness of the second end  46  of the collar  42  allows for more flexibility between the collar  42  and the vessel  110  to accommodate expansion. In this preferred embodiment, the thickness of the first end is approximately twice the thickness of the second end and is formed by welding a second layer of metal onto the first layer for part of the length of the collar  42 . 
     A layer of insulation  30 , such as Vibecast refractory, lines the inner walls of the vessel body  110  of the cyclone  102 . A gap between the refractory material  30  and the collar  42  at each side of the collar  42  (only shown on one side in FIG. 4) is packed with ceramic wool  31 , such as Kaowool. This prevents any deflection of the support collar  42  from interfering with the rigid refractory material  30 . 
     Referring now to FIG. 5, the outlet pipe  32 , having a tapered outer surface portion  34 , is inserted into the opening defined by the beveled first end  44  of the collar  42 . The tapered surface  34  will enter this opening until its outer diameter exceeds the smallest inside diameter of the opening defined by the beveled first end  44  of the collar  42 . Then the funnel  34  will come to rest on the beveled first end  44  of the collar  42 , and the two surfaces, having the same taper, mate so as to have a good metal to metal seal. The outlet pipe  32  is then centered and vertically hung with respect to the collar  42 . 
     As a hot fluid stream is introduced into the cyclone  102 , the temperature of all the components will begin to rise. Since the vessel body  110  and the collar  42  are insulated with refractory  30  and packed wool  31 , their temperature rise will be less dramatic than that of the outlet pipe  32  and its corresponding tapered outer surface  34 , resulting in different dimensional growth due to differing thermal expansion. However, the tapered surface  34  is free to grow dimensionally, independent of the vessel body  110  of the cyclone  102 . As the tapered surface  34  grows, it rides up the beveled surface  44  of the collar  42 , taking up the differential in expansion while keeping the outlet pipe  32  round and vertically hung. Thus, there is no distortion or extra stress caused to the parts by thermal expansion, while still maintaining the desired seal between the parts. To remove the outlet pipe  32 , a crane or other lift device simply hooks into the holes  38  in the gussets  36  and lifts the outlet pipe  32  out of the cyclone body  110 . 
     It will be obvious to those skilled in the art that modifications may be made to the embodiment described above without departing from the scope of the present invention.