Cyclone separator including a hopper formed by water-steam cooled walls

Abstract: A cyclone separator (2) formed by a plurality of parallel tubes (20). A portion of the tubes (20) form a cylinder (8), a portion are bent radially inwardly to form a roof (4) and a portion are bent to form a hopper (6). Water is passed through tubes (20) to cool the separator.

Description: This invention relates to a cyclone separator and, more particularly, to such a separator for separating solid fuel particles from gases discharged from a combustion system or the like. Conventional cyclone separators are normally provided with a hopper connected to their lower end to collect the solid particles from the separator. The separator and the hopper are usually provided with a monolithic external refractory wall which is abrasion resistant and insulative so that the outer casing runs relatively cool. Typically, these walls are formed by an outer metal casing and two inner insulative refractory materials to protect the outer casing from high temperatures and reduce heat losses. However, in order to achieve proper insulation, these layers must be relatively thick which adds to the bulk, weight, and cost of the separator and hopper and require controlled, relatively long, start-up and shut down times to prevent cracking of the refractory. Also, the outside metal casing of these designs cannot be further insulated from the outside since to do so could raise its temperature as high as 1500°F (approximately 816°C) which is far in excess of the maximum temperature it can tolerate. Further, most conventional cyclone separators require relatively expensive, high temperature, refractory-lined ductwork and expansion joints between the reactor and the cyclone, and between the cyclone and the heat recovery section, which are fairly sophisticated and expensive. Still further, conventional separators formed in the above manner require a relatively long time to heat up before going online to eliminate premature cracking of the refractory walls, which is inconvenient and adds to the cost of the process. Also, other cyclone separators may require a separate roof tube circuit which still further adds to the cost of the system. SE-B-437 124 discloses a cyclone separator made up of a number of tubes extending between a pair of ring headers, with upper end portions of the tubes bent radially inwardly to form a roof section for the separator. EP-A-0298671 discloses a cyclone separator the cylindrical part of which is made up of a number of tubes extending between a pair of ring headers, with upper end portions of the tubes bent inwardly to form a roof section for the separator. It is therefore an objective of the present invention to provide an improved cyclone separator. According to the invention there is provided a cyclone separator comprising an inner cylinder, a plurality of tubes, the intermediate portions of the tubes extending vertically and circumferentially in a parallel relationship to form an outer cylinder extending around the inner cylinder in a coaxial relationship to define an annular chamber between the cylinders and, the upper end portions of the tubes being bent radially inwardly to form a roof section, a first ring header connected to the upper ends of the tubes, a second ring header connected to the lower ends of the tubes, lower end portions of the tubes lower end portions of the tubes being bent radially inwardly to form a conical shaped hopper section, means for passing water or steam or a water and steam mixture through the ring headers to circulate the water or steam or water and steam mixture through the tubes to cool the separator, and means for directing gases containing solid particles through the annular chamber for separating the solid particles from the gases by centrifugal forces, the separated gases exiting through the inner cylinder and the separated solids falling to the bottom of the separator for disposal or recycle, an upper portion of the inner cylinder extends above the roof section, the first and second ring headers are coaxially aligned with one another, a continuous fin of varying width extends from corresponding portions of adjacent tubes to form a gas tight structure, refractory means extends around the inner surfaces of the tubes, and insulation extends around the outer surfaces of the tubes. In the cyclone separator according to the invention, heat losses can be reduced and the requirement for internal refractory insulation minimized. Also the bulk, weight and cost of the separator can be much less than that of conventional separators. Further, the need for expensive, high-temperature, refractory-lined ductwork and expansion joints between the furnace and the cyclone separator and between the latter and the heat recovery section are minimized. Because the conical, cylindrical and roof sections of the separator are formed by heat transfer tubes, circulation of a steam-water mixture can be maintained in the tubes with an external pump or without the use of an external pump in a natural circulation boiler. The invention will now be described, by way of example, with reference to the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 is a perspective/schematic view of the cyclone separator of the present invention showing a portion of the tubes forming the outer cylinder; and Figure 2 is a cross-sectional view taken along the line 2-2 of Figure 1. Referring to Figure 1 of the drawings, the cyclone separator 2 of the present invention includes an upper roof section 4, a conically-shaped lower hopper section 6 and an intermediate cylindrical section 8. A lower ring header 12 is disposed at the lower end of the hopper section 6 and an upper ring header 14 is disposed above the roof section 4. Each of the sections 4, 6 and 8 is formed by a group of continuous, spaced, parallel tubes 20 spanning the entire length of the separator 2 and connected at their lower ends to the header 12 and at their upper ends to the header 14. An inlet passage 24 is provided to the interior of the cylindrical section 8 and can be formed by bending a portion of the tubes 20 out of the plane of the cylindrical section 8 as shown in more detail in U.S. Patent No. 4,746,337 assigned to the assignee of the present invention, the disclosure of which is incorporated by reference. The roof section 4 is formed by bending the tubes 20 radially inwardly at an angle as shown by the reference numeral 20a, and then upwardly at an angle as shown by the reference numeral 20b. An inner pipe, or barrel, 26 is disposed within the cylindrical section 8, is formed from a solid, metallic material, such as stainless steel, and has an upper end portion extending slightly above the roof section 4. The pipe 30 extends immediately within the circular opening defined by the apex formed by the bent tube portions 20a and 20b. An annular chamber 28 is formed between the outer surface of the pipe 26 and the inner surface of the cylindrical section 8, for reasons that will be described. As better shown in Fig. 2, the tubes 20 are spaced apart and a continuous fin 30 extends from, and is welded to, adjacent tubes. The structure thus formed is disposed between an inner refractory material 32 and outer insulative material 34. The refractory material 32 can be a relatively thin layer of high conductivity refractory and the insulative material may be of any conventional design. A natural-circulation steam drum 40 is provided which is connected, via a pipe 42 and two branch pipes 42a and 42b, to the upper ring header 14. A downcomer pipe 44 and two branch pipes 44a and 44b connect the steam drum 40 to the lower ring header 12. Thus, water from the steam drum is conveyed by the downcomer pipe 44 to the ring header 12 by gravity and passes upwardly from the latter header through the tubes 20 by natural convection, as will be described. It is understood that the separator 2 of the present invention is part of a boiler system including a fluidized bed reactor, or the like, (not shown) disposed adjacent the separator. In operation, the inlet passage 24 receives hot gases from the reactor which gases contain entrained fine solid particulate fuel material from the fluidized bed. The inlet passage 24 is arranged so that gases containing the particulate material enter in a direction substantially tangentially to the chamber 28 and thus swirl around in the chamber. The entrained solid particles are thus propelled, by centrifugal forces, against the inner wall of the cylindrical section 8 where they collect and fall downwardly by gravity into the hopper section 6. The relatively clean gases remaining in the chamber 28 are prevented from flowing upwardly by the roof section 4, and thus enter the pipe 26 through its lower end. The gases pass through the length of the pipe 26 before exiting from the upper end of the pipe and are directed to external equipment for further use. Water, or steam, from the drum 40 is passed, via the pipes 44, 44a and 44b into the lower header 12 and passes, by convectian upwardly through the tubes 20 of the hopper section 6, the cylindrical section 8 and the roof section 4. The heated water, or steam, passes into the upper header 14 and, via the pipes 42a, 42b and 42 back to the drum 40. The water thus maintains the separator 2 at a relatively low temperature. Several advantages result from the arrangement of the present invention. For example, heat losses are reduced and the requirement for internal refractory insulation is minimized. Also, the bulk, weight, and cost of the separator of the present invention is much less than that of conventional separators. Further, the need for expensive high temperature refractory-lined ductwork and expansion joints between the reactor and cyclone separator, and between the latter and the heat recovery section is minimized. Still further, the requirement for additional roof circuitry is eliminated. It is understood that variations in the foregoing can be made within the scope of the invention. For example, the inner pipe 26 can be formed of water tubes in a manner similar to the separator 2 and the latter tube can be connected to the flow circuit including the steam drum 40. Also, a forced circulation system can be used instead of the natural circulation system described above in which case a pump 50 would be provided in the line 44 which receives the fluid from the drum 40 and pumps it to and through the branch conduits 44a and 44b and the tubes 20.

Claims: A cyclone separator (2) comprising an inner cylinder (26), a plurality of tubes (20), the intermediate portions of the tubes extending vertically and circumferentially in a parallel relationship to form an outer cylinder (8) extending around the inner cylinder (26) in a coaxial relationship to define an annular chamber between the cylinders and, the upper end portions of the tubes (20) being bent radially inwardly to form a roof section (4), a first ring header (14) connected to the upper ends of the tubes (20), a second ring header (12) connected to the lower ends of the tubes (20), lower end portions of the tubes 20 are bent radially inwardly to form a conical shaped hopper section (6) means (40,42,44) for passing water or steam or a water and steam mixture through the ring headers to circulate the water or steam or water and steam mixture through the tubes to cool the separator, and means (24) for directing gases containing solid particles through the annular chamber for separating the solid particles from the gases by centrifugal forces, the separated gases exiting through the inner cylinder (26) and the separated solids falling to the bottom of the separator for disposal or recycle, characterised in that an upper portion of the inner cylinder (26) extends above the roof section (4), the first and second ring headers (14,12) are coaxially aligned with one another, a continuous fin (30) of varying width extends from corresponding portions of adjacent tubes (20) to form a gas tight structure, refractory means (32) extends around the inner surfaces of the tubes (20), and insulation (34) extends around the outer surfaces of the tubes (20). A separator as claimed in Claim 1 further comprising means (24) forming an inlet opening in a tangential relationship to the annular chamber for receiving gases containing solid particles and directing same against the inner wall of the outer cylinder (8) to separate the solid particles from the gases by centrifugal forces, the separated gases exiting through the inner cylinder (26) and the separated solids falling to the bottom of the outer cylinder and hopper section (6) for disposal or recycle. A separator as claimed in Claim 1 or Claim 2 in which the tubes (20) are disposed in a spaced relationship. A separator as claimed in any preceding claim in which the passing means comprises a steam drum (40) and means connecting the steam drum (40) to the ring headers (14,12) to circulate water and/or steam through the steam drum (40) and the tubes (20). A separator as claimed in Claim 4 in which the water and/or steam circulate through the tubes (20) and the steam drum (40) by natural circulation. A separator as claimed in Claim 4 further comprising pump means for circulating water and steam through the tubes (20) and steam drum (40).

Inventors: VENKATRAMAN SESHAMANI, VENKATRAMAN, SESHAMANI
Applicants: FOSTER WHEELER ENERGY CORP, FOSTER WHEELER ENERGY CORPORATION
Application year: 1990
Main classification: B04C5
IPC codes: F23J15, F22B31, B04C5