EP0024818B1

EP0024818B1 - Insulated ceramic fiber refractory module

Info

Publication number: EP0024818B1
Application number: EP19800302570
Authority: EP
Inventors: David Ross Dunlap; Ronald Ray Smith
Original assignee: AP Green Refractories Co
Current assignee: AP Green Refractories Co
Priority date: 1979-07-26
Filing date: 1980-07-28
Publication date: 1984-04-25
Also published as: DE3067617D1; EP0024818A1; MX153463A

Description

Background of the invention

The present invention relates to ceramic fiber modules for insulating the interior of a high temperature furnace. In particular, this invention describes a module and method of using the same in which the module comprises a ceramic fiber shell-like form, a plurality of ceramic fiber blankets situated within the shell-like form and means for joining the shell and contents to a furnace housing which generally is of steel.
For many years heat treating furnaces, ceramic kilns, brick kilns, and the like, were lined with dense fireclay brick. Later insulating firebrick replaced the dense fireclay brick because of its lighter weight and better insulating properties. Recently ceramic fiber material made of alumina-silica fibers made into blankets has replaced the insulating firebrick as lining for such furnaces and kilns. The latest advance in this art is the use of module units in which the ceramic fiber blankets are positioned on end, or edge grain, and restrained in a blanket which is designed to be attached to the steel frame defining the furnace or kiln.
The rolls of ceramic fibers typically are impaled upon metal studs welded to the furnace walls. This arrangement has several drawbacks, namely that the temperature limit of the construction is dependent on the temperature that the metal studs can stand. Another drawback is that the ceramic fiber blankets are easily damaged, torn and also tend to shrink lengthwise with high temperature use so that gaps are formed between the ends of the blankets.
For economic reasons, it is undesirable to replace a large layered blanket module, which has only a relatively small damaged area. However, unless the blanket is replaced, the damaged area will grow in size.
In order to facilitate replacement of damaged insulation, numerous modular insulation articles have been developed.
The modules eliminate much of the temperature limitation, but there is a possibility that heat can flow between the modules and between the strips of ceramic fibers mounted in the modules. In all of these modules, the blankets are perpendicular to the furnace wall and therefore the thermal conductivity and refractoriness of the module is uniform from hot face to cold face.
Typical of such construction are the constructions of U.S. Patents Nos. 3,819,468 and 3,993,237. These devices still require a welded stud on the furnace frame and time consuming application. Other patents exemplifying this type construction include U.S. Patent No. 3,832,815 in which a series of strips of ceramic fibers are clamped together into a module for installation on furnace walls. Still other such devices are shown in U.S. Patents Nos. 4,001,996 and 4,123,886.
UK Patent Specification No. 2 006 413 discloses an insulating module, for lining a wall of a furnace and like equipment, comprising an outer shell-like form of ceramic fiber insulating material; at least one layer of ceramic fiber insulating material positioned within the outer shell; means for joining said shell and layer; and attachment means for attaching the module to the wall.
As mentioned, in all of the foregoing listed patents the fibers in the blanket lie in planes generally perpendicular to the furnace wall. In addition many of these devices require a welded stud on the furnace wall and several of the patents disclose impaling or spearing the ceramic blanket on a pin or stud mounted on the furnace wall with a washer mounted on the end of a stud to hold the blanket in place. These arrangements tend to allow the blanket to sag or tear away from the furnace wall and the stud serves as a conduit for heat from the blanket to the furnace wall.
Accordingly it is a principle object of the present invention to provide a ceramic fiber module in which layers of ceramic fiber blankets are all positioned in a plane parallel to the surface of the furnace wall inside a shell-like form. It is a further object to provide a simple effective means for attaching such ceramic fiber modules to a furnace wall in an efficient and safe manner. It is a further object to provide a method for fastening such ceramic fiber modules to a furnace wall without providing a direct conduit for heat to pass from the furnace to the outside shell.
Still another object is to provide a module of ceramic fiber blankets in which the end of the module closest to the heat of the furnace has a high temperature resistant fiber blanket positioned therein. Closer to the furnace wall are high heat transfer resistance materials.
A still further object is to provide a "T" shaped anchor which is fastened to a furnace frame and retains modules in side-by-side arrangement on the wall while the anchor is protected from direct furnace heat.
These and other objects and advantages will become apparent hereinafter.

Summary of the invention

The present invention provides a new and improved composite high temperature and high insulating module in which the or each layer of ceramic fiber insulating material is parallel to the wall to which the module is attached; the attachment means comprise a one-piece "T" anchor; and the anchor comprises opposing arms having sharpened ends, one of which penetrates the module from a side intermediate the hot and cold faces, and a centre bar member which is bent back on itself so that it is of double thickness and fastened at the end thereof to the furnace wall.

Description of the drawings

Figure 1 is a fragmentary vertical sectional view of a preferred embodiment of the invention;
Figure 2 is an enlarged fragmentary side elevational view of the preferred anchor means shown in Figure 1;
Figure 3 is a plan view of a preferred blank for the shell shown in Figure 1:
Figure 4 is a detailed side elevational view of a modification of the anchor means shown in Figure 2;
Figure 5 is a detailed top view of the embodiment shown in Figure 4;
Figure 6 is a sectional view taken along line 6-6 of Figure 4; and
Figure 7 is a fragmentary sectional view of parts of two ceramic fiber modules fastened to a furnace wall by the anchor means shown in Figures 4, 5 and 6.

Detailed description

The modular insulating article designated by the letter "A" (Figure 1) comprises an outer shell-like form 10, insulation layers 11, 12, 13, 14, disposed within the shell 10. The preferred modification is shown in Figures 1 and 2 and involves a "T" shaped anchor 60 spot-welded at the free leg of the "T" 61 to the furnace wall 62. The top of the anchor 60 has opposed ends 63 which may be sharpened as shown in Figure 2. The modules "A" are impaled onto the ends 63 to retain them to the wall 62.
The "T" shaped anchors 60 preferably are of 304SS or 310SS stainless steel and are one piece with the center bar member 64 being bent back on itself so that it is of double thickness. The distance of the top members 63 from the wall 62 is determined by the thickness of the module "A" but preferably is 1/2 of the height of the module "A".
In the modification shown in Figures 1 and 2, the ceramic fiber blanket layers 11, 12, 13, 14 are secured together and to the shell 10 by any suitable adhesive such as Kaowool Cement by Babcock and Wilcox or Cera-Cote Cement by Johns-Manville. Wherever adhesives are mentioned in this application, any conventional ceramic fiber blanket adhesive is suitable.
The outer shell 10 has a rectangular cross section and a depth which varies according to the preference of the user and the thickness and number of the insulating layers 11-14. The depth of the shell 10 preferably is about 6" (15.2 cm). The configuration of the cross- section is preferably square, and the dimensions preferably 12"x12" (30.5 cmx30.5 cm). The thickness or depth of the shell 10 depends on the temperature of the furnace in which it is located. The higher the operating temperature of the furnace the thicker the module needs to be.
The shell 10 is formed from a blank 30a (Figure 3) which is cut in the form of a cross. The blank 30a has fold lines 31 to define a closed end 32 and side walls 33. When the side walls 33 are folded inwardly, the shell 10 is formed with an open base.
Suitable materials for the shell 10 include commercially available ceramic blankets manufactured under the names Kaowool (Babcock and Wilcox), Fiber-Frax (Carborundum Co.), Lo-Con (Carborundum Co.), Cera-Blanket (Johns Manville Co.) and Cer-Wool (C. E. Refractories). The blankets are made from refractory materials such as chromia-alumina-silica, alumina-silica compositions, fused silica, high silica glass and zirconia compositions which withstand high temperatures. When erected, the outer shell 10 has the appearance and structure of a five sided box or cube, having a vacant interior portion. Within the vacant interior portion are disposed the insulation layers 11-14. Suitable materials for the layers include the fiber insulating blankets sold under the names Kaowool (Babcock and Wilcox), Fiber-Frax (Carborundum Co.), Cera-Blanket (Johns Manville Co.), and Cer-Wool (C. E. Refractories). The blankets are made from refractory materials such as chromia-alumina-silica, alumina-silica compositions, fused silica, high silica glass and zirconia compositions which withstand high temperatures.
The thickness of each layer can vary from 1 to about 2 inches (2.5 to about 5 cm) and from about 3 Ib/ft³ (0.048 g/cm³) to about 8 Ib/ft³ (0.128 g/cm³) in density. It is preferred that the thicker layers be placed closer to the furnace wall and that the thinner layers be placed closer to the "hot face", i.e., the side of the module adjacent to the furnace interior. The quantity of layers to be inserted into the shell varies according to the preference of the user and the operating temperature of the furnace. Also it is preferred that the most highly refractory or high temperature resistant layers be close to the hot face while the less dense and lower cost insulating layers be placed close to the furnace wall. This results in economies of construction and in a more heat resistant and good insulating module. In Figure 1, the layer 11 has a density of 4 Ib/ft³ (0.064 g/cm³) while the layer 14 has a density of 8 Ib/ft³ (0.128 g/cm³). The layer 14 is highly temperature resistant while the layer 11 has excellent resistance to heat transfer, and has a lower cost.
The layers 11-14 are positioned parallel to the furnace wall to provide better insulating effect and also for ease of assembly. When the layers 11-14 are positioned parallel to the furnace wall, it allows the aforementioned variance in density, refractoriness, etc., among the different layers. The layers 11-14 are laid in the shell 10, and the base 18 positioned over the open end of the shell 10.
An anchor 70, having the shape of a bifurcated "T", is shown in Figures 4-6 as well as being shown installed in Figure 7. The anchor 70 is a one piece unitary member made from stainless steel such as 304SS, 310SS or tnconet601.
The anchor 70 comprises a body portion formed from parallel upstanding spaced apart legs 71 and 72. The legs 71 and 72 are laterally spaced and aligned to allow adjacent modules "A" to engage each other in a close fit.
The legs 71 and 72 terminate in a single U-shaped foot 73 which has a bight portion adapted to engage and retain the head 74 of a self-tapping screw 75 which fastens the anchor 70 to the furnace wall 15 (Figure 7). The foot 73 is at right angles with respect to the legs 71 and 72 and joins the said legs 71 and 72 at their lower ends. The lateral spacing of the legs 71 and 72 is determined by the size of the bight portion of the foot 73.
At the free ends of the legs 71 and 72 are opposed sharpened arms 76 and 77 which are used to impale the modules "B" as shown in Figure 7. The ends 78 and 79 of the arms 76 and 77 are tapered at about a 30° angle to give a sharpened effect which allows the arms 76 and 77 to more easily penetrate the modules "B". The arms 76 and 77 are parallel but extend 180° with respect to each other. They also are parallel to the foot 73 and the arm 76 extends in the same direction as the foot 73 while the opposed arm 77 extends away from the foot 73.
The anchor 70 can be attached to the steel wall 15 using a variable speed hand drill to drive the fastener 75 into the wall 15. Such tools are available from any of the major hand tool manufacturers. The size of the self-tapping screw 75 is determined by the thickness of the shell.
Wherever in this specification a module is glued to an existing furnace wall, any commercially available air setting mortar can be used.
The various elements shown in the different embodiments "A" and "B" may be interchanged without affecting the scope of the invention.

Claims

1. An insulating module, for lining a wall of a furnace and like equipment, comprising:

(a) an outer shell-like form of ceramic fiber insulating material;

(b) at least one layer of ceramic fiber insulating material positioned within the outer shell;

(c) means for joining said shell and layer; and

(d) attachment means for attaching the module to the wall; characterised in that:

each layer of ceramic fiber insulating material is parallel to the wall to which the module is attached;

the attachment means comprise a one piece "T" shaped anchor; and

the anchor comprises opposing arms having sharpened ends, one of which penetrates the module from a side intermediate the hot and cold faces, and a centre bar member, which is bent back on itself so that it is of double thickness and fastened at the end thereof to the furnace wall.

2. The module of Claim 1 wherein said attaching means is a bifurcated one piece unitary "T"-shaped anchor having, firstly, a foot means which includes a bight portion to engage and retain a fastening means and, secondly, a body portion formed from parallel, upstanding, spaced apart legs which have opposed arms at their free ends.

3. A furnace wall-lining combination characterized by side by side rows of the modules of Claim 1 positioned on the interior wall of a furnace in adjacent position, wherein one piece "T" shaped anchors penetrate the side walls of adjacent modules intermediate the hot face and cold face and each comprise a top with sharpened ends on which the modules are impaled and a centre bar member, bent back on itself so that it is of double thickness, with a free end spot welded to the furnace wall.

4. A refractory module assembly for lining an interior wall of a furnace characterized by:

(a) ceramic fiber shells formed into open sided cubes having the open sides disposed adjacent to a wall of the furnace,

(b) a plurality of ceramic fiber interior layers positioned within said shells, said layers disposed in planes parallel to the wall of the furnace,

(c) bases for said modules, said bases being joined to said shells to form the sixth side of the cubes; and

(d) one piece "T" shaped anchors for attaching said modules to the wall, which penetrate the modules from a side intermediate the hot and cold faces and each comprise a top with sharpened ends on which the modules are impaled and a centre bar member, bent back on itself so that it is of double thickness, with a free end spot welded to the furnace wall.

5. The module assembly of Claim 4 wherein the ceramic fiber layers positioned adjacent to the hot faces of the modules are more refractory than the layers positioned adjacent to the furnace wall.