EP0209626B1

EP0209626B1 - Erosion resistant waterwall

Info

Publication number: EP0209626B1
Application number: EP19850305173
Authority: EP
Inventors: Richard C. Johnson; Leigh B. Egbert
Original assignee: Foster Wheeler Energy Corp
Current assignee: Foster Wheeler Energy Corp
Priority date: 1985-07-19
Filing date: 1985-07-19
Publication date: 1990-10-31
Also published as: EP0209626A1; DE3580361D1

Description

This invention relates to a waterwall and, more particularly, to a waterwall that has been provided with a surface that is resistant to erosion caused by particulate material.
Most erosion in industrial processes occurs where large volumes of abrasive particles such as coal, catalyst, sand, shale, limestone, etc. change direction of flow via elbows, tees, separators, swirl vanes and the like. The erosion occurs as a result of low angle impingement by large volumes of the abrasive particules which move at varying velocities.
Several systems have been devised to resist this type of erosion. For example, monolithic, cement or phosphate bonded castable (and plastic) refractories held by steel anchors on about two or four-inch staggered centers, or on a hexagonal steel grid have been utilized to resist the above erosion. A system of this type is disclosed in DE-A 27 24 336 in which a tubular heat exchanger wall is equipped with rods on the furnace side.On the rods are mounted protective caps of a fireproof material secured thereto by cement. Also, a considerable thickness, up to several inches of the above mentioned refractories, have been installed on V-bar of S-bar anchors, and if the erosion is exceptionally severe a prefired refractory is used which is usually bolted to the steel structure.
However, the use of these refractories affects the thermal conductivity which, in many systems, seriously affects heat absorption rates to the tubular surfaces in fluidized bed boilers, for example.
It has been discovered that a steel support system is more erosion resistant than most of the monolithic cement-bonded, castable refractories discussed above that are traditionally used in studded anchor wall systems. However, if the tube enclosure walls were simply designed with a greater thickness of steel, the weight and cost increase could be prohibitive.
The present invention is directed at a waterwall that is erosion resistant yet does not affect the heat absorption rates of the waterwall. It also seeks to do so in such a matter that does not prohibitively increase the weight and cost of the system.
A waterwall according to the invention comprises a plurality of water tubes extending in a spaced parallel relationship; a plurality of continuous fins extending between adjacent tubes for the length thereof and connected to the outer surfaces of the tubes to form a gas-tight structure; and a plurality of stud members attached to the exposed surface at one side of the structure, the stud members being disposed over the exposed surface of each tube in the structure. Each stud member is formed with a portion projecting towards the exposed surface, each stud member and projecting portion being a solid body of circular cross-section, with the diameter of the projecting portion being less than that of the stud member. The stud member is surrounded by a ceramic sleeve, with a part of each sleeve being held around the projecting portion and between the stud member and the surface of the tube, and the distal end of each portion is welded to the said exposed surface to anchor the stud member and the ceramic sleeve thereto.
An embodiment of the present invention will now be described by way of example and with reference to the accompanying drawing in which:

Figure 1 is a partial, front perspective view of a conventional waterwall being prepared according to the invention;
Figure 2 is a cross-sectional view taking along the line 2-2 of Figure 1 and depicting a portion of the waterwall surface after being prepared according to the invention;
Figure 3 is a top plan view of the stud member utilized in the embodiment of Figure 2; and
Figure 4 is a vertical cross-sectional view taken of the stud member of Figure 3 before it is welded to the waterwall to form the assembly shown in Figure 2.

In Figure 1 reference numeral 10 refers in general to a conventional waterwall before it has been modified according to the present invention. The waterwall is formed by a plurality of spaced, parallel water tubes 12 extending for the length of the wall. A pair of continuous fins 14 extend from diametrically opposed surfaces of each tube 12. Each fin 14 is welded along its edge portion to the corresponding surfaces of the adjacent tubes 12 to form a gas tight structure.
A portion of the surface of the waterwall 10 that is exposed to heated particulate material is depicted in Figure 2 in connection with a tube 12 and the two fins 14 extending therefrom. According to the present invention, a plurality of stud members are disposed in a spaced relationship along the exposed surfaces of the tube 12 and the fins 14.
As shown in Figure 2, the stud member are formed by an inner, rod-like member 22 surrounded by a ceramic sleeve 24. A portion 22a of the inner member 22 projects downwardly from the ceramic sleeve 24 for melting during welding of the stud member to the exposed surface of the tube 12 and the fins 14. The inner members 22 thus functions to anchor the ceramic sleeves down in the position shown in Figure 2 and, in addition, provides steel to weld the stud member, including the ceramic sleeve 24 to the outer exposed surface of the tube 12 and the fins 14. The stud members are preferably made of steel which is welded to the exposed surfaces of the waterwall 10 as described.
Although only one tube 12 and its corresponding fins 14 is shown in Figure 2, it is understood that the stud members can extend over the entire exposed surface of the waterwall 10 as needed.
According to a preferred embodiment the diameter of each tube is at least five times greater than the diameter of the stud members and the spacing between adjacent stud members is between one- fourth of an inch (0.64cm) to one inch (2.54cms). For example, the diameter of a tube 12 can be three inches (7.62cms) while the diameter of each stud member is one-half inch (1.27cms), it being understood that these dimensions can vary with different designs.
The arrangement of the present invention enjoys several advantages. For example, the irregular shape formed by the stud members in the described embodiment disrupts the abrasive particulate flow and lowers the erosive potential when the particles impact with each other or are deflected away from the underlying structure. The closely spaced stud members may also serve as traps for the particulate material which protects the underlying steel in the areas of severe erosive activity. Further, the invention enables the metal surface thickness to be selectively increased in localized, erosion prone areas of the waterwall as required.
All of the foregoing is achieved without significantly reducing the heat absorption rates of the waterwall and is ideally suited for field repairs and installation in areas with obvious high erosion rates. is understood that, according to present invention, if heat transfer . is not a factor the spaces between the stud members may be filled with a moderately erosion resistant aluminaphosphate bonded monolith which can be replaced if necessary during annual outages.

Claims

1. A waterwall comprising a plurality of water tubes (12) extending in a spaced parallel relationship; a plurality of continuous fins (14) extending between adjacent tubes (12) for the length thereof and connected to the outer surfaces of the tubes to form a gas-tight structure; and a plurality of stud members (22) attached to the exposed surface at one side of the structure, the stud members (22) being disposed over said exposed surface of each tube (12) in the structure, characterised in that each stud member (22) is formed with a portion (22a) projecting towards said exposed surface, each stud member (22) and projection portion (22a) being a solid body of circular cross-section, with the diameter of the projecting portion (22a) being less than that of the stud member (22), the stud member 22 is surrounded by a ceramic sleeve (24), with a part of each sleeve (24) being held around the projecting portion (22a) and between the stud member (22) and the surface of the tube (12), and the distal end of each portion (22a) is welded to the said exposed surface to anchor the stud member (22) and the ceramic sleeve (24) thereto.

2. A waterwall according to Claim 1 characterised in that the stud members (22) and sleeves (24) are closely spaced on and extend over the entire exposed surface of each tube (12).

3. A waterwall according to Claim 1 or Claim 2 characterise in that the diameter of each tube (12) is at least five time greater than the diameter of each stud member (22) disposed thereon.

4. A waterwall according to Claim 3 characterised in that the diameter of each tube (12) is substantially 7.6 cms (3 inches) and the diameter of each member (22) is substantially 1.25 cms (0.5 inch).