Refractory tile for heat exchanger protection

A refractory tile adapted for protective fixation to the heat exchanger in an incinerator or furnace regardless of orientation. The tile includes a transverse groove which carries a shouldered slot to be guided by and mate securely with an anchor attached to the heat exchanger.

This invention is in the field of refractory materials, especially the 
field of firebrick and tile. More specifically, this invention relates to 
the specialized refractory tile employed in furnaces, ovens, incinerators, 
boilers, etc. to protect heat exchangers therein from the erosive and 
corrosive effects of flame. 
BACKGROUND OF THE INVENTION 
It has long been the practice to cover the firebox walls of facilities such 
as municipal incinerators with a firebrick or tile sheath in order to 
protect the structural elements thereof, the walls and the ceilings, from 
the erosive and corrosive effects of the fire. Many of these facilities 
now include energy recovery systems which operate to retrieve the heat 
generated during the combustion process. In many cases the energy recovery 
system comprises a boiler, including an array of metal tube walls through 
which water is circulated as a heat transfer medium. This array is often 
placed at the periphery of the firebox and is also susceptible to the 
detrimental effects of impinging flame. Therefore, it is desirable to 
protect this heat exchanger array with its own refractory covering which 
is suspended from the heat exchanger itself. 
In contrast to the firebrick employed to protect the structural elements of 
the facility, the refractory material used to cover the heat exchanger is 
seldom simply firebrick held together with mortar but is often a more 
specialized type of brick or tile with unique characteristics. One of the 
characteristics required of the brick is high thermal conductivity to the 
underlying heat exchanger. Another, but related, special requirement is a 
means for attaching the brick to the heat exchanger. Attachment of the 
brick has been accomplished in a number of ways. 
In U.S. Pat. No. 3,327,445, refractory bricks are suspended on the vertical 
wall of a furnace on metallic support shoes and hung from vertical "I" 
beams using "J" bolts anchored in the bricks. U.S. Pat. Nos. 3,328,014 and 
3,380,409 disclose furnace wall construction in which tongue and groove 
mating elements are used to hang refractory brick from a vertical metal 
framework. In none of these references is the brick hung from a heat 
exchanger. 
U.S. Pat. No. 1,987,738 discloses a steam locomotive firebox which contains 
an array of tubing through which water is circulated. The heat exchanger 
on the metallic arch of the firebox, which is inclined from the vertical, 
is shielded from direct flame with a layer of refractory blocks. The 
blocks are suspended from and anchored to the array by means of mating 
tongue and groove structures in the blocks and arch. Boiler tubes in a 
furnace are protected with refractory brick which is hung from the tubing 
framework with mated fittings according to U.S. Pat. Nos. 3,850,146 and 
3,828,735. 
U.S. 3,797,416 discloses protecting boiler tubes from the erosive effects 
of injected pulverized coal fuel by hanging protective structures from the 
tubing using mated ear and groove fittings which are wedged together to 
provide a tight fit to the tubing. Nickel alloy, not refractory brick, is 
disclosed as the protective structural material, flame not being the 
erosive agent. 
U.S. Pat. No. 4,768,447 describes a firebrick adapted to be hung on a 
vertical wall of tubing in an incinerator by means of an inclined recess 
in the firebrick into which a mating projection from the tubing wall fits; 
the firebrick is held against the tubing by gravity. 
Whereas there have been many proprietary methods for hanging protective 
refractory brick on an array of heat exchanger tubing, few of these 
methods have commercial significance. The most common method for hanging 
the firebrick is to run a bolt through the brick and anchor it to the 
tubing. This technique, while relatively inexpensive, subjects the brick 
to compressive stresses, which leads to the development of cracks and, 
ultimately, to failure of the brick. Furthermore, while many of the 
methods for affixing the bricks may be satisfactory when the array of heat 
exchanger tubing is vertical, they become unsatisfactory for use when the 
array is inclined from the vertical toward horizontal; the weight of the 
bricks then tends to pull them away from the tubing, lowering the thermal 
conductivity drastically and sharply affecting the efficiency of heat 
recovery. 
For example, the firebrick of U.S. Pat. No. 4,768,447 is forced against the 
tubing array by gravity only to the extent the array is vertical. To the 
degree the array is inclined from the vertical, the weight of the brick 
tends to separate it from the tubing. 
SUMMARY OF THE INVENTION 
Thus, it is an object of this invention to provide a refractory tile which 
can be employed effectively on an inclined, including horizontal, tubing 
array, as well as on a vertical array of heat exchanger tubing. It is 
another objective to provide a refractory tile which is relatively easy to 
produce and inexpensive to mount. It is yet another objective to provide a 
refractory tile system which includes a refractory tile together with a 
mating anchor to affix the tile to an array of tubing. Still another 
objective of this invention is to provide a protective covering of tile 
systems to shield an array of heat exchanger tubing from the erosive and 
corrosive action of flame while maintaining efficient heat recovery. Other 
objectives will become apparent hereinafter. 
These objectives are attained by this invention in a refractory tile which 
is particularly adapted for fixation to either vertical or inclined arrays 
of heat exchanger tubing to produce, with other tile, a monolithic 
protective covering over the array. Close contact between the tile and the 
heat exchanger is obtained, regardless of the orientation of the array, 
thus providing excellent thermal conductivity. 
Each refractory tile of this invention includes an exposed face and a 
concealed face which are spaced apart with an edge. The concealed face of 
the tile carries at least one groove which is open to the concealed face 
and extends transversely across the tile from the edge. The groove 
includes a shouldered slot which terminates on the concealed face of the 
tile. The underside of the shoulder begins at the slot entrance with a 
guiding surface tapered into the groove and ends with a securing surface 
paralleling the groove. 
In preferred embodiments, the concealed face of the tile is contoured so 
that the tile closely engages the heat exchanger through a refractory 
mortar bond, thereby providing optimum thermal contact. Also in preferred 
embodiments, the refractory tile carries a recess on its edge to allow 
fixation of each tile to adjacent tile in the array with mortar. 
The invention will be clarified by reference to the drawings which 
accompany this specification and to the detailed description which follows 
.

DETAILED DESCRIPTION 
With reference now to FIG. 1, above floor 21 of an incinerator or other 
furnace is supported or suspended heat exchanger 25, which is typically an 
array of closely spaced metal tubing through which a liquid heat transfer 
medium is passed. Combustion produces, among other things, gases and 
particulate matter which exit at stack 24, as well as heat which is to be 
absorbed by the heat exchanger. The heat exchanger can have vertical 
and/or inclined portions. The tile systems of this invention can be 
employed in vertical protective covering 22 or equally well in protective 
covering 23, which is inclined from the vertical. 
As may be seen by reference especially to FIGS. 2-6, the refractory tile of 
this invention comprises a ceramic body 40 composed of a thermally 
resistant but thermally conductive material, the nature of which can be 
varied as is well known in the art, the specific composition of which is 
not critical to this invention. The tile is characterized by a face 41, 
which is intended to be exposed to fire and flame, a face 42, which will 
typically be in close contact with heat exchanger 25 and concealed from 
view, and edge 43, which separates and spaces the faces apart. Although 
tile of other shapes, e.g., triangular or hexagonal, can be employed in 
the invention, the tile will typically be rectangular in plan as shown in 
FIG. 2, and, although not a requirement, the faces of the tile will 
generally be more or less coplanar as shown in FIG. 3. These selections of 
shape are made for reasons of ease in manufacture and minimum ultimate 
cost of the tile. 
One of the features of the tile is that the concealed face 42 carries at 
least one groove 46 which extends transversely from the edge of the tile. 
The single groove which is present in the tile of FIGS. 2-6, or a 
plurality of such grooves if they are present is/are adapted to guide the 
tile into position and mate the tile securely with an anchor mounted on 
the heat exchanger, or a plurality of anchors if the tile carries a 
plurality of grooves. 
The tile can be adapted to mate securely with an anchor mounted on the heat 
exchanger by providing groove 46 with a shouldered slot 47. In alternative 
embodiments, the groove 46 can, if desired, extend entirely across the 
tile. However, in the embodiment shown, groove 46 terminates at about 
mid-tile as illustrated in FIG. 5. The length and width of groove 46 can 
vary to suit the dimensions of the anchor. Slot 47 will end at a 
termination 49 which is a stop for the anchor to rest against, thus 
permitting installation in a vertical orientation. 
The underside of the shoulder 48 begins at the slot entrance with guiding 
surface 50 which works, in cooperation with a tile anchor member moving 
into the slot, to force the tile against the heat exchanger. As the anchor 
member moves further into the slot, the member encounters securing surface 
51, locking the tile in place. One advantage of mating the tile securely 
to an anchor in this way is that, no matter what the orientation of the 
tile with respect to the vertical, the tile is urged to closely hug the 
heat exchanger for the most efficient and effective heat transfer. 
Tile anchor 60, shown in FIG. 7, includes stem 61 to be mounted on the heat 
exchanger and sized to pass into slot 47 and be stopped against 
termination 49. Anchor 60 further includes bar 62 which is sized to pass 
through groove 46 and under shoulder 48 to engage guiding surface 50 shown 
in FIG. 5. It will be evident that other groove, slot and associated 
anchor shapes can be provided to achieve the guided and secured mating 
between the tile groove and its associated tile anchor. 
The tile is mounted on the heat exchanger by buttering the concealed 
surface of the tile with mortar, pressing tile groove 46 onto the bar of 
the anchor with the stem of the anchor at the entrance of tile slot 47. 
Sliding the tile along the bar then engages the bar with tapered surface 
50 of shoulder 48, forcing the tile toward the heat exchanger. Finally, 
sliding the tile further brings the stem against slot termination 49 with 
the bar against securing surface 51 of the shoulder. Adjacent tile in a 
desired array are similarly mounted on the heat exchanger. 
The refractory tile system of this invention, which includes the tile and 
its associated anchor(s), can be affixed to the heat exchanger in several 
ways. One of these ways ways is shown in FIG. 8. Tubing 26 in a heat 
exchanger array is typically joined together with metal fins 27, and it is 
convenient to simply weld the stem 61 of the anchor to the fin at the 
correct position on the tubing array. A thermally conductive mortar 70 is 
applied to the concealed face of the tile before sliding the tile over bar 
62 of the T-shaped anchor. The stem of the anchor can be varied in length 
to optimize contact with the heat exchanger. 
One of the features of a preferred tile is that the concealed face 42 will 
be contoured as necessary to conform as closely to the surface of the heat 
exchanger as possible for good heat transfer. In the event the heat 
exchanger is an array of tubing, contour 45 may be adapted to match the 
tubing. Clearly, the specific contour required to match the heat exchanger 
surface can be built into the tile at the time of its manufacture. 
The tile is also preferably provided with an edge which carries a recess 44 
to receive additional mortar as a plurality of the tile systems are 
combined to provide the protective covering of this invention as 
illustrated in FIG. 9. 
Although the invention has been illustrated in one or more preferred 
embodiments, it is not intended nor required that the scope of the 
invention be limited other than by the following claims.