Abstract:
A horizontal cyclone separator in which a furnace section and a vortex chamber communicating with the furnace section and having an inlet which extends a fraction of the length of the furnace section receives a mixture of the gaseous products of combustion and solids entrained by the gases. A coaxially disposed tube extends partially into the chamber to allow the separated gases to exit the separator. A ring-shaped solids deflector is disposed on the vertical wall opposite the coaxially disposed tube to prevent solids from bouncing off the rear wall towards the center of the separator and into the path of the separated gas stream. The separated solids fall into an outlet trough formed in a lower portion of the furnace section for returning the solids to the furnace section.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to a cyclone separator, and, more particularly, to a horizontal cyclone separator for separating solid particles from gases generated by the combustion of fuel in a fluidized bed reactor, or the like. 
     BACKGROUND OF THE INVENTION 
     A typical cyclone separator is usually associated with a fluidized bed reactor and includes a vertically-oriented, cylindrical vortex chamber in which is disposed a central gas outlet pipe for carrying the separated gases upwardly, while the separated solids are returned to the fluidized bed through a funnel-shaped base of the separator via a stardpipe. These vertical cyclone separators are substantial in size and eliminate the possibility of a compact system design which can be modularized and easily transported and erected. For larger reactors, several vertical cyclone separators are often required to provide adequate particle separation, which compound the size problem and, in addition, usually require complicated gas duct arrangements with reduced operating efficiency. 
     Horizontal cyclone separators characterized by a horizontally-oriented, cylindrical vortex chamber, as disclosed, for example, in U.S. Pat. No. 5,174,799, have been constructed which eliminate many of the above mentioned problems. For example, horizontal cyclone separators may be readily configured within the upper portion of the reactor and integrated with the walls of the reactor making the bulk, weight, and cost much less than conventional separators. Additionally, they can be modularized making them easy to erect. However, many known horizontal cyclone separators have various shortcomings, particularly with regard to their gas-solids inlet which extends substantially the full length of the separator. This extended length causes the separated solids that have collected on the wall past the exit to become re-entrained in the incoming gas-solids stream. Another shortcoming is that the vertical end wall opposite the gas outlet causes the separated solids to bounce off the latter wall and become re-entrained in the separated gas stream. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a horizontal cyclone separator that minimizes the re-entrainment of the separated solids into the separated gas stream. 
     It is a further object of the present invention to provide a horizontal cyclone separator having an inlet that extends a fraction of the length of the separator. 
     It is a still further object of the present invention to provide a horizontal cyclone separator of the above type in which a ring-shaped solids deflector is provided on the vertical end wall opposite a gas outlet to prevent solids from bouncing from the wall into the separated gas stream. 
     It is a further object of the present invention to provide a horizontal cyclone separator wherein the incoming gas-solids mixture is directed tangentially into a vortex chamber. 
     Toward the fulfillment of these and other objects, the horizontal cyclone separator of the present invention includes a furnace section and a vortex chamber communicating with the furnace section and having an inlet which extends a fraction of the length of the furnace section and receives a mixture of the gaseous products of combustion and solids entrained by the gases. Once inside the vortex chamber, the solids are separated from the mixture by centrifugal action. A coaxially disposed tube extends partially into the chamber to allow the separated gases to exit the separator. A ring-shaped solids deflector is disposed on the vertical wall opposite the coaxially disposed tube to prevent solids from bouncing off the rear wall towards the center of the separator and into the path of the separated gas stream. The separated solids fall into a trough formed in a lower portion of the furnace section for returning the solids back to the furnace section. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above brief description as well as further objects, features, and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred but nonetheless illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawing in which: 
     FIG. 1 is a perspective/schematic view of a fluidized bed reactor including the horizontal separator of the present invention; 
     FIG. 2 is a sectional view taken along the line  2 — 2  of FIG. 1; 
     FIG. 3 is a sectional view taken along line  3 — 3  of FIG. 1; and 
     FIG. 4 is a sectional view taken along line  4 — 4  of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1-4 of the drawings, the reference numeral  10  refers, in general, to the fluidized bed reactor of the present invention. The reactor  10  includes a front wall  12 , a spaced parallel rear wall  14 , and an intermediate partition  16  extending between the walls  12  and  14  in a spaced, parallel relation thereto. As shown in FIG. 1, first and second sidewalls  18  and  20  extend perpendicular to the front wall  12  and the rear wall  14  to form a substantially rectangular vessel. As shown in FIGS. 2 and 4, the upper portions  12   a  and  14   a  of the walls  12  and  14 , respectively, are curved and extend towards each other to provide a roof for the vessel. The front wall  12  and the partition  16 , along with corresponding portions of the sidewalls  18  and  20 , form a furnace section  22 . 
     The walls  12  and  14 , the partition  16 , and the sidewalls  18  and  20  are each formed by a plurality of vertically-disposed tubes  23  (FIG. 1) interconnected by vertically-disposed elongated bars, or fins to form a contiguous, airtight structure. Since this type of structure is conventional, it will not be described in further detail. 
     Conventional flow circuitry is provided, although not shown, to pass water, steam and/or a water-steam mixture (hereinafter termed “fluid”) through the tubes  23  to heat the fluid to the extent that it can be used to perform work, such as driving a steam turbine. To this end, headers (not shown) are connected to the upper and lower ends of the walls  12  and  14  for introducing fluid to, and receiving fluid from, the tubes  23  forming the respective walls. Downcomers connect a steam drum (not shown) to the headers by branch conduits for passing fluid from the drum to the headers. Conduits (not shown) connect the upper headers to the steam drum for returning fluid from the headers to the drum. The aforementioned flow circuitry is also provided for the partition  16  and the sidewalls  18  and  20 , and it is understood that the reactor  10  may be equipped with additional flow circuitry for improving the transfer of heat from the reactor  10 . Since, this type of flow circuitry is well known, it is not shown in the drawings nor will it be described in further detail. 
     A perforated air distribution plate  24  is suitably supported at a lower portion of the furnace section  22  and defines a plenum chamber  26  extending below the plate  24 . Air from a suitable source is introduced into the plenum chamber  26  by conventional means, such as a forced-draft blower, or the like. The air introduced through the plenum chamber  26  passes in an upwardly direction through the air distribution plate  24  and may be preheated by air preheaters and appropriately regulated by air control dampers as needed. 
     The air distribution plate  26  is adapted to support a bed of particulate fuel material consisting, in general, of crushed coal and limestone, or dolomite. A fuel distributor pipe  27  (FIGS. 2 and 4) extends through the front wall  12  for introducing the particulate fuel into the furnace section  22 , it being understood that other pipes can be associated with the walls  12 ,  18 , and  20  for distributing particulate fuel material and/or additional particulate fuel material into the furnace section as needed. It is understood that a drain pipe may register with an opening in the air distribution plate  24  and extend through the plenum  26  for discharging spent fuel and sorbent material from the furnace section  22  to external equipment. 
     A horizontal cyclone separator, designated generally by the reference numeral  28 , is provided in an upper portion of the vessel formed by the reactor  10 . The separator  28  includes a horizontally-disposed vortex chamber  30  for separating solid particles from a mixture of gases and particles, in a manner to be described. The vortex chamber  30  is generally cylindrical and is defined by the upper, curved portions  12   a  and  14   a  of the front wall  12  and the rear wall  14 , respectively, as well as an upper portion  16   a  of the partition  16  which is curved towards, and is connected to, the curved wall portion  12   a . An elongated opening formed in the upper portion  16   a  of the partition  16  defines an inlet  32  extending a fraction of the length of the furnace section  22  and the vortex chamber  30 . The vertical portions of the partition  16  and the wall  14  define an outlet trough  34  extending from a lower portion of the vortex chamber  30  to an area just above the distribution plate  24 . The wall  14  and the partition  16  also include angularly extending straight portions  14   b  and  16   b , respectively, which define a horizontally oriented funnel  35 , extending the full length of the vortex chamber  30 , for directing the separated solids from the vortex chamber  30  to the outlet trough  34 . 
     A solid block  33  having ends  33   a  and  33   b  (FIG.  1 ); sides  33   c  and  33   d ; a top  33   e ; and a bottom  33   f  is disposed in the furnace section  22  and is mounted on the partition  16 , with the side  33   d  and the top  33   e  of the block engaging the wall portions  16   b  and  16   a , respectively, of the partition  16  as shown in FIGS. 2 and 4. The side  33   c  of the block  33  is positioned just below the inlet  32  and parallel to the wall  12  to define, along with the latter wall and the sidewall  20 , a straight passage, having a substantially rectangular cross-section, registering with the inlet  32  to direct the flow of entrained solids and gases substantially tangential into the separator  28 . 
     A central open-ended tube  36  extends through the sidewall  20  and has a first portion  36   a  extending just above the inlet  32  as viewed in FIG. 1, and a second portion  36   b  projecting outwardly from the latter wall. 
     A generally ring-shaped solids deflector  38  having an outer annular flange  39  (FIGS. 1 and 3) extends inwardly from wall  18  and is connected to the wall in any conventional manner. An opening, or slot,  38   a  is defined in the lower portion of the deflector  38  for directing separated solids into the funnel  35  and the outlet trough  34 . 
     In operation, particulate fuel material is introduced to the air distribution plate  24  from the distributor pipe  27  and is ignited by a light-off burner (not shown), or the like. Additional material, such as adsorbent material, or the like, may be introduced through other distributors into the interior of the furnace section  22 , if needed. 
     A high-pressure, high-velocity, combustion supporting air is introduced through the air distribution plate  24  from the plenum chamber  26  at a velocity which is greater than the free-fall velocity of the relatively fine particles in the bed and less than the free-fall velocity of relatively course particles. Thus, a portion of the fine particles become entrained and pneumatically transported by air and the combustion gases. The mixture of entrained particles and gases rises upwardly within the furnace section  22  and is directed by the block  33  and corresponding portions of the walls  12  and  20  through the inlet  32  and into the vortex chamber  30  in a direction substantially tangential to the vortex chamber  30  and thus swirls around in the chamber. The entrained solid particles are propelled by centrifugal forces against the inner surfaces of the upper portions  12   a ,  14   a , and  16   a  of the walls  12  and  14  and the partition  16 , respectively, forming the vortex chamber  30 , where they collect and are thus separated from the gases. The separated particles then fall downwardly by gravity into the funnel  35  and the outlet trough  34 . The partition  16  extends sufficiently into the fuel bed supported by the distribution plate  24  so that the particles can flow from the outlet trough  34  into the furnace section  22  as needed, while sealing against backflow of the high-pressure gases from the furnace section  22 . The pressure changes created by the spiral flow force the separated gases concentrating along the central axis of the vortex chamber  30  toward the low pressure area created at the inlet opening of the tube  36 . The clean gases thus pass into the tube  36  and exit through the outlet opening directly into a heat recovery section or other external equipment. 
     Water is introduced into the system through water feed pipes that are conducted downwardly through the tubes forming the walls  12 ,  14 ,  18 , and  20  and the partition  16  as described above. Heat from the fluidized bed, the gas column, and the transported solids convert a portion of the water into steam, and the mixture of water and steam rises in the tubes, collects in a set of upper headers and is transferred to a steam drum. The steam and water are separated within the steam drum in a conventional manner and passed to conventional external equipment. Other cooling surfaces, preferably in the form of partition walls with essentially vertical tubes, can be utilized in the furnace section  22 . 
     It is thus seen that the reactor of the present invention provides several advantages. For example, the provision of the horizontal cyclone separator integrated in the upper portion of the reactor  10 , with the outlet trough  34  connected directly to the fuel bed of the furnace section  22 , permits the separation of the entrained particles and the recycling of same back to the furnace section while eliminating the need for relatively bulky and expensive vertical cyclone separators. Also the gas-solids mixture enters the vortex chamber  30  generally tangentially through the inlet  32  extending along a fraction of the length of the furnace section, without being significantly redirected by unnecessary baffles, tubes and/or ducting. Also, the inlet  32  extends only a fraction of the length of the separator  28  thereby preventing separated solids within the vortex chamber  30  from encountering the incoming gas-solids mixture. Furthermore, the ring-shaped solids deflector  38  prevents solids from bouncing from the rear wall  18  into the exiting gas vortex spinning towards the gas exit  42 . Moreover, the central tube  36  promotes well-defined circulation in the vortex chamber  30 , thereby providing sufficient centrifugal force to counteract the reversal of acceleration caused by the earth&#39;s gravity. Finally, since the outer portion  36   b  of the tube  36  is provided just behind the end of the vortex chamber  30 , the hot, clean gases are transferred directly and quickly into external equipment without the need for additional piping and intricate duct arrangements. 
     It is understood that variations in the foregoing can be made within the scope of the invention. For example, the walls of the vessel of the reactor  10  may be reconfigured to accommodate more than one horizontal cyclone separator in the upper portion thereof in communication with the furnace section. Also, while the headers and flow circuitry have been described, it should be understood that any other suitable header and flow circuitry arrangement could be employed in connection with the present invention. 
     A latitude of modification, change, and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.