Cyclone separator wall refractory material system

Abstract: A refractory material system for the wall of a cyclone separator in which a plurality of erosion-resistant refractory material wear blocks extend in a spaced relationship to the tube of the water-steam walls of a cyclone separator. The wear blocks are attached to a continuous fin extending between each adjacent pair of tubes and insulating, erosion-resistant refractory material extends between the fins and the wear blocks.

Description: This invention relates to a refractory material system for the wall of a cyclone separator and, more particularly, to such a refractory material system that has been provided with a surface that is resistant to erosion caused by particulate material. Conventional cyclone separators, for service at ambient temperatures, are normally provided with a steel shell which may be lined with a relatively thick about 102 to 152 mm (4 to 6 inches) erosion-resistant refractory material, if severe erosion is expected. At high temperatures (up to about 982°C or 1800°F) the lining may be provided with a dense, erosion-resistant hot face refractory material and a lightweight, insulating back-up layer with an overall thickness of 305 or more mm (12 or more inches). The purpose of the insulating back-up layer is to insulate and protect the outer shell from hot, corrosive process gases as well as to provide an erosion-resistant, hot-face refractory material which can be repaired or replaced as erosion progresses. A circulating fluidized bed boiler requires large diameter cyclone separators which are exposed to hot (816° to 982°C or 1500°-1800°F) gases containing erosive particles. Conventional thick refractory wall cyclone separators have several drawbacks for this application. The most significant drawbacks are that several inches of refractory material and insulation are required with a significant weight increase; the erosion-resistant layer must be resistant to rapid temperature changes which requires a special, costly, low-expansion refractory material and conservative heating cycles; the massive refractory material walls are difficult to install and maintain, especially in the roof sections; and frequent internal repairs are necessary to maintain the necessary surface contour and thickness. Any excessive loss of hot-face refractory material requires costly, time-consuming repairs to prevent overheating of the steel enclosure. Cyclone separators having water-steam cooled walls have reduced heat loss through the enclosure walls. The cyclone walls, however, must be protected from erosion caused by hot, high-velocity fluid bed particles. A refractory system protecting the cyclone walls from erosion must have a predictable thermal conductance to prevent damage to the tubular water-steam walls in the event of a catastrophic shutdown in which the hot fluidized bed solids settle against the refractory system. U.S. Patent No. 4,635,713 discloses an erosion resistant tubular waterwall. The design criteria of a tubular waterwall, however, from the standpoint of erosion and thermal absorption characteristics differ substantially from the design criteria of the wall of a cyclone separator in a circulating fluidized bed boiler. There is therefore a need for a lightweight hot-face refractory material system with high erosion-resistance as well as controllable and predictable thermal conductance to ensure long-term protection for the tubular support members and the steel enclosure during rapid shutdowns. European Application 88306056.8, Serial No. 298 671 discloses a cyclone separator where refractory blocks cover and protect a waterwall arrangement. The blocks are joined to the tubes of the waterwall arrangement but their replacement in the event of wear or damage is not foreseen. Therefore according to the present invention there is provided a cyclone separator comprising a plurality of tubes extending vertically and circumferentially in a parallel relationship for at least a portion of their lengths, a plurality of continuous fins extending between adjacent tubes, the tubes and fins forming a waterwall, a plurality of wear blocks extending in a spaced relation to the waterwall, a plurality of anchors extending perpendicularly from the fins and refractory means extending between the waterwall and the wear blocks, characterised in that the wear blocks comprise a centrally located bore and a weldable member located at one end of the bore, and the weldable members are welded to the anchors to secure the wear block to the waterwall. In a cyclone separator according to the invention the waterwall is protected from overheating. The refractory material wear blocks are attached to the tubular waterwall system of the cyclone separator but may be easily replaced in the even of mechanical or thermal breakage. The invention will now be more fully described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective/schematic view of a cyclone separator according to the present invention; and Figure 2 is an enlarged, cross-sectional view taken along the portion of the wall of the outer cylinder of Figure 1 as designated by the line 2-2. Referring to Figure 1 of the drawings, a cyclone separator 10 is shown which may be of any type suitable for use with a circulating fluidized bed boiler such as the cyclone separators disclosed in co-pending Application No. 88306056.8, Serial No. 298 671 and U.S. Patent No. 4,476,337. A refractory material system 12, is shown in Figure 1 as applied to the inner wall of the cyclone separator disclosed in Figures 6 and 7 of co-pending Application No. 88306056.8, Serial No. 298 671, for purposes of example. The cyclone separator 10 includes a lower ring header 16 and an upper ring header 18. The header 16 extends immediately above, and is connected to, a hopper 20 disposed at the lower portion of the separator 10. A group of vertically-extending, spaced, parallel tubes 22 are connected at their lower ends to the header 16 and extend vertically for the greater parts of their lengths to form a right circular cylinder 24. A proportion 22a of the tubes 22 are bent out of the plane of the cylinder 24 to form a tangential inlet passage 26 to the interior of the cylinder. At the upper end of the cylinder 24, the tubes 22 have radially inwardly bent portions 22b, followed by upwardly directed portions 22c to define a circular opening which has a diameter less than that of the diameter of the cylinder 24. The tubes 22 then finally have radially outwardly bent portions 22d, with their respective ends being connected to the upper header 18. The tube portions 22b thus form a roof for the cyclone. A plurality of pipes 28 extend upwardly from the upper header 18, it being understood that the lower header 16 can be connected to a source of cooling fluid, such as water, or steam, which passes from the header 16, through the tubes 22, and into the upper header 18 before being discharged, via the pipes 28, to external equipment. The direction of flow for the cooling fluid could also be reversed. An inner pipe, or barrel, 29 is disposed within the cylinder 24, is formed from a solid, metallic material, such as stainless steel, and has an upper end portion extending slightly above the plane formed by the header 18 and the upper tube portions 22d. The pipe 29 extends immediately adjacent the tube portions 22c, and its length approximately coincides with the inlet passage formed by the tube 22a. Thus, an annular passage is formed between the outer surface of the pipe 29 and the inner surface of the cylinder 24, and the tube portions 22b form a roof for the chamber. It is understood that an upper hood, or the like (not shown), preferably rectangular in cross section, can be provided above the plane formed by the upper header 18 and the tube portions 22d and can be connected to the pipe 29 by a plurality of conical plates or the like (not shown). The hood can be top supported from the roof of the structure in which the separator 14 is placed and the remaining portion of the separator can be supported from hangers connected to the header 18, or the pipes 28. Referring to Figure 2, the refractory material system 12 includes a plurality of erosion-resistant refractory material wear blocks 30. As shown in Figure 1 the refractory material system 12 extends adjacent the inner wall of the cyclone separator 10 and overlies the tubes 22. As shown in Figure 2 a fin 32 is attached to, and extends from, the adjacent walls of each pair of adjacent tubes 22. The fins 32 are, preferably, welded to the tubes 22. The tubes 22 and fins 32 together constitute a waterwall system 34 forming the wall of the cylinder 24. The wear blocks 30 are attached to the waterwall system 34 by anchors 36 extending from the fins 32. The anchors 36 are, preferably, welded tot he fins 32. Each wear block 30 includes a centrally located bore 38 having a varying diameter, and a ferrule insert 40 is located at the lower end of the bore. The wear blocks 30 are preferably attached to the anchors 36 by inserting each anchor 36 into a corresponding bore 38 and plug-welding the ferrule insert 40 to the anchor to create a weld zone 44. The weld zone 44 and the upper end of the bore 38 are covered with a plug 48 of insulating, erosion-resistant refractory material. The plug 48, preferably, comprises a refractory material product commercially available under the Trade Mark C-E 90 Ram TR Plastic Trowel Mix. An insulating, erosion-resistant layer of refractory material 50 is disposed between the wear blocks 30 and the waterwall system 34 and around a plurality of studs 52 attached to the tubes 22. The studs 52 are preferably made of steel and, as shown in Figure 2, are preferably arranged in an alternating pattern of 3 studs per tube and 2 studs per tube on adjacent tubes 22. The layer of refractory material 50 aids in protecting the waterwall system 34 from overheating in the event of a catastrophic shutdown in which hot fluid bed material settles against the wall of the cylinder 24 and overheats the waterwall system 34. The layer 50 of refractory material, preferably, comprises an aluminium or magnesium phosphate-bonded alumina-silicate. Suitable materials include products commercially available under the Trade Mark CE-Blu Ram HS which is an unburned 73% Al₂O₃ plastic firebrick, or under the Trade Mark Resco AA-22. As stated above, the refractory material is preferably rammed to the surface contour of the studs 52, although those skilled in the art will recognise that other, less erosion-resistant castable or plastic refractory materials may be cast, rammed, gunited, or vibration-cast over the studs 52. Those skilled in the art will also recognize that the refractory material of the layer 50 as well as the plug 48 may include reinforcing stainless steel fibres, preferably, in a weight percentage of from about 2.0 to about 5.0 percent, to improve the strength and spall resistant properties of the refractory material. The wear blocks 30 provide additional insulation and erosion protection for the waterwall system 34 and the insulating layer 50 of refractory material. However, in the event of the failure of several erosion-resistant wear blocks 30, the waterwall system 34 will still be protected from excessive heat absorption and severe erosion by the layer 50 of erosion-resistant refractory material. The wear blocks 30, preferably, have a high erosion resistance and a specific thermal conductivity that aids in controlling the rate of heat absorption from the fluid bed solids, which may be at a temperature of about 871°C (1600°F), into the waterwall system 34 in the event of a rapid shut-down. The wear blocks 30 of the refractory material system 12, preferably, are arranged in a vertical, staggered alignment to conform with the circumferential contour of the cylinder 24 as shown in Fig. 1. The wear blocks 30, preferably, are arranged to provide perimetrical spacing therebetween and, most preferably, to provide 6.4 mm (1/4-inch) perimetrical open joints. The perimetrical spacing of the wear blocks 30 tends to prevent disruptive mechanical spalling forces that are generated during thermal cycling, especially during start-up and shut-down, when fine bed dust or particulate material accumulates between adjacent mortar or butt jointed wear blocks. The perimetrical spacing of the wear blocks 30 also enables periodic maintenance repairs of individual wear blocks without requiring the removal of several if not all adjacent blocks. By staggering the wear blocks 30 and providing for open joints therebetween, tangential erosive attack of and continuous joint erosion paths in the wear blocks around the circumference of the cylinder 24 are minimized. Those skilled in the art will recognize that the size and shape of the wear blocks 30 may be varied to accommodate any specific configuration. Each wear block 30, preferably, includes a bevel 54 at its vertical edges to minimize disruption of the cyclone flow characteristics of the separator. Since each wear block 30 is attached to an anchor 36, the wear blocks 30 may be easily removed and replaced in the event of mechanical failure or thermal spalling by removing the plug 48 and detaching the wear block 30 from its anchor 36. The wear blocks 30 may comprise any suitable refractory material such as those containing alumina silicates, alumina, silica, zirconia or silicon-carbide. The wear blocks 30, preferably, comprise aluminium or magnesium phosphate-bonded refractory materials since advantageous erosion resistant properties can be attained without the necessity of prefiring the blocks at a temperature above 538°C (1000°F) and since the blocks will have maximum strength in the 371 to 1093°C (700 to 2000°F) temperature range. A suitable material includes a product commercially available under the Trademark C-E 90 Ram HS Plastic which is a pre-reacted (pre-heated) phosphate - bonded 93% alumina (Al₂O₃) plastic firebrick, or C-E Blue Ram HS (73% Al₂O₃). Those skilled in the art will recognize that the wear blocks 30 may also comprise a prefired ceramic bonded material and that the refractory material of the wear blocks may also include reinforcing stainless steel fibres to improve the strength and spall-resistant properties thereof. The erosion-resistant refractory arrangement used in the cyclone separator 10 of the present invention has superior resistance to the rapid temperature changes that may occur in a hot circulating bed environment. The refractory material 50 disposed around the tubes 22 and studs 52 is grossly sub-divided by the multitude of studs 52, leaving an infinite number of small segments of refractory mass between the studs 52. These small segments are very resistant to failure by shrinkage or cracking. Furthermore, the wear blocks 30 are very resistant to cracking due to the absence of abutting joints where compressive stresses can originate from expanding dust and particulate accumulations. Although not shown in either Fig. 1 or Fig. 2, a lagging, or panel of a lightweight material, such as aluminum may be provided in a slightly spaced relationship to the plane of the waterwall system 34. Moreover, a heat insulative material may be disposed between the outer surface of the waterwall system 34 and the inner wall of the lagging or panel. In operation, and assuming the separator 10 of the present invention is part of a boiler system including a fluidized bed reactor, or the like, disposed adjacent the separator, the inlet passage 26 receives hot gases from the reactor which gases contain entrained fine solid particulate fuel material from the fluidized bed. The gases containing the particulate material thus enter and swirl around in the annular chamber defined between the cylinder 24 and the inner pipe 29, and the entrained solid particles are propelled by centrifugal forces against the inner wall of the cylinder 24 where they collect and fall downwardly by gravity into the hopper 20. The relatively clean gases remaining in the annular chamber are prevented from flowing upwardly by the roof formed by the tube portions 22b and their corresponding fins 32, and thus enter the pipe 29 through its lower end. The gases thus pass through the length of the pipe 29 before exiting from the upper end of the pipe to the aforementioned hood, or the like, for directing the hot gases to external equipment for further use. Water, or stream from an external source is passed into the lower header 16 and passes upwardly through the tubes 22 before exiting, via the upper header 18 and the pipes 28, to external circuitry which may form a portion of the boiler system including the separator 10. The water thus maintains the wall of cylinder 24 at a relatively low temperature. In the event of a catastrophic shutdown in which hot fluid-bed material settles against the walls of the separator 10, the erosion-resistant layer of refractory material 50 and the wear blocks 30 protect the waterwall system 34 from overheating. Several advantages result from the foregoing arrangement. For example, the separator of the present invention reduces heat losses and minimizes the requirement for internal refractory insulation. Also, the bulk, weight, and cost of the separator of the present invention is less than that of conventional separators. Since the refractory material system 12 is relatively lightweight, the cyclone structure can be pre-fabricated with the refractory system attached resulting in a considerable reduction in field installation costs. The separator of the present invention also minimizes 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. Still further, by utilizing the tube portions 22b to form a roof for the annular chamber between the cylinder 24 and the pipe 29, the requirement for additional roof circuitry is eliminated. It is understood that the present invention is not limited to the specific design of the cyclone separator shown in Figure 1. For example, the hopper section 20 of the separator 10 can also include water tubes identical to the tubes 22 of Figure 1.

Claims: A cyclone separator (10) comprising a plurality of tubes (22) extending vertically and circumferentially in a parallel relationship for at least a portion of their lengths, a plurality of continuous fins (32) extending between adjacent tubes (22), the tubes (22) and fins (32) forming a waterwall (34), a plurality of wear blocks (30) extending in a spaced relation to the waterwall (34), a plurality of anchors (36) extending perpendicularly from the fins (32) and refractory means (50) extending between the waterwall (34) and the wear blocks (30), characterised in that the wear blocks (30) comprise a centrally located bore (38) and a weldable member (40) located at one end of the bore (38), and the weldable members (40) are welded to the anchors (36) to secure the wear block (30) to the waterwall (34). A cyclone separator as claimed in Claim 1 in which the wear blocks (30) extend in spaced rows, with the wear blocks of each row being staggered relative to the wear blocks in adjacent rows. A cyclone separator as claimed in Claim 1 or Claim 2 in which the wear blocks (30) extend in perimetrically spaced rows. A cyclone separator as claimed in any preceding claim in which the wear blocks (30) have bevelled edges (54). A cyclone separator as claimed in any preceding claim in which refractory material (48) covers the weldable member (40) and fills the other end of the bore (38) in the wear blocks (30). A cyclone separator as claimed in any preceding claim in which a plurality of studs (52) are attached to the tubes (22) and extend within the refractory means (50). A cyclone separator as claimed in Claim 6 in which the studs (52) are arranged in a repeating pattern of three studs per tube and two studs per tube on adjacent tubes (52).

Inventors: JOHNSON RICHARD C, JOHNSON, RICHARD, C.
Applicants: FOSTER WHEELER ENERGY CORP, FOSTER WHEELER ENERGY CORPORATION
Application year: 1990
Main classification: B04C5
IPC codes: B04C5