US1775414A

US1775414A - Furnace-wall structure

Info

Publication number: US1775414A
Application number: US82750A
Authority: US
Inventors: Frank J Tone
Original assignee: Carborundum Co
Current assignee: Unifrax 1 LLC
Priority date: 1926-01-21
Filing date: 1926-01-21
Publication date: 1930-09-09
Anticipated expiration: 1947-09-09

Description

Sept. 9, 1930.

F. .LYToNE FURNACE WALL STRUCTURE Filed Jan. 21, 1926 Patented sept. 9, 1930'.V

UNITED STATES PATENT oFFiycE ERAN; if. TONE, or NIAGARA FALLS, NEw Yoan, AssIcNon 'ro THE cAEEoaUNnUN y COMPANY, or NIAGARA rALLs, NEw Yoan, A coEroEArIoN or rENNsYLvANTA rUnNAcE-WALL srnuc'runn l Appuaadp alea nnuary 21, me. -serm No. slam.

This invention relates to furnace wall structures such as are used in boiler furnaces, and the like, where the side walls are subjected to severe temperature conditions. The invenp f tion refers particularly to a composite type of wall consisting of refractory material, in

which are installed water tubes to absorb a portion of the heat and prolong the life of the structure. y

It is the practice in certain types of construction to replace the `ordinary fire-brick' Wall with a water tube construction whichv is either exposed directly to the flame in the furnace, or is partially protected from the flames by means of metal or refractory facings. In many cases the water tubes are enmoved un er normal conditions.

The invention may 'be readily understood by reference to the accompanying drawings which illustrate a preferred embodiment of my invention, but to the details of construction of which my invention is not limited.

In the drawin v Figure -l is a slde elevation of a portion ofv a furnace wall embodyingmy invention;

Fi ure 2 is a section in--the plane of line II--II of Figure 1;

' Figure 3 is a detail view similar to Figure2, sllioviling a slightly modified constructlon of l 00 Fi ure 4 is a section taken on the line IV V of Figure 3, lshowing in addition the outer wall of the furnace;

Figure 5 is a view similar to Figure 3, showlng another modification and 4 Figure 6 is a detail view of anotherform o'f block. f

In the drawings, 2 represents a portion of a furnace structure within which are vertical which has abo y portion 5 and a lug portionv 6. The lugl ortion 6 is adapted to project betweenpara lel tubes 3, and is diagonally or angularly arranged with respect to the body of the block in such wa that the outer end of the lug may extend be ind one of the tubes, asclearly shown in Figure 2,'while lthe lug itself has a recess 7 into which a portion of the tube may fit.

The tubes 3 are The thickness of the block may be varied as conditions may arise, but I have found that in the'ordinary construction an overall thickness of approximately four inches is very satisfactory. In such a block the body portion is substantially two inches thick. rllhe locks are laid in courses or rows, with the angular lug or projection 6 in alternate courses being reversed, as shown in Figure 2. When arranged .in this manner, the friction of one row of blocks on the contiguous rows makes it diiiicult for an row ofv blocks to b e moved out diagonally rom its -proper position.

For the purpose of further securing the wall, the tops of the blocks may be provided with one or more lugs 8 ada ted to project into correspondingly forme grooves 9 1n the next adjacent lock above, thereby providing an interlocking connection between joints. This prevents any movement of any single row of blocks in a direction parallel with the face of the wall. The result of this is that it is impossible for any block to move outwardly in a direction normal to the face of .the wall and all of the blocks are locked securely in place by the tubes.

. engaging the two parallel tubes t lock the v j block in position. By making the straps 12v of sufficient widths, it is possible to have a single strap hold two adjacent blocks in place. This can be done by forming the groove 11a in one of the blocks on the top face of the block and having the groove correspondingly located'in the bottom of the block which would be superimposed thereon. The two grooves would then be opposite each other and would be aligned so that the single strap 12 could serve to hold two blocks in place, as shown in Figure 4:.

The construction shown in Figure 5 is generally similar to that described in connection with Figure 3, lbut in this particular form of block the body 13 of each block has two legs or lugs 14 which are spaced apart a distance sufficient to enable the block to straddle the pipe 3. The width of the lugs or legs 14 is equal to substantially half ofthe distance between adjacent tubes, so that the lugs of two adjacent blocks will serve to fill the gap between two adjacent tubes. The

lugs 14 are provided with grooves 15 ar? ranged in the same manner as the grooves 11 described in connection with Figure 3. A strap 16 may be inserted in the 'grooves 15 of the legs of two adjacent blocks, to lock the blocks to the tubes.

The block shown in Figure 6 has a body portion 17 and a curved lug 18 within which is a semi-circular recess 19. -The shape of the lug 18 and the recess 19 is such that the block may be placed in the wall structure by turning it about the tube with the tube as a center. When in position, the curved lug 18 will be fitted around the pipe to such an extent that the block will be prevented from moving straight out away from the tube.

While the blocks as described in any of the various forms may be made of any suitable refractory material, I prefer to use a material for the blocks having an'especially high refractibilty and a high lcoefiicientof thermal conductlvity or heat permeability, as compared with fire-clay. This is because I find that these properties enable a suiiicient amount of heat to be withdrawn from the exposed portion of the block to keep it below the temperature at which it would react y with the products of combustion. This arrangement gives a block which will withstand excessive temperature conditions and excessive corrosive conditions. When the heat which is conducted awa from the ex. posed portion of the bloc reaches the back of the block, it is absorbed by Huid passing through the tubes in a useful manner. There is, therefore, a very definite advantage obtained by the u'se of blocks of high heat permeability in combination with cooling tubes, whereby a more highly refractory furnace is secured and a more effective cooling of the lining obtained.

As a specific example, silicon carbide has been found to be from around six to nine times more thermally conductive than fire clay. The thermal conductivity as compared with fire clay varies according to the density of the refractory blocks, the manner in which they are formed, and the percentage of bonding material and filler relative to the amount of silicon carbide contained in the block. Silicon carbide is also very much stronger at the high operating temperatures of a boiler than is fire clay. The thermal conductivity fof silicon carbide is well above .O06 cal./c1n3/CC./sec.. whereas fire clay has a thermal conductivity well below this.

Considering that fire clay is a much poorer conductor of heat than silicon carbide, it will be evident that in order to dissipate heat through a fire clay refractory the wall will have to be so thin, in order to transmit any appreciable amount of heat, as to be mechanically impractical. Considering that silicon carbide is from six to nine times more thermally conductive than fire clay, a silicon carbide wall from six to nine inches thick will dissipate the same amount of heat as a fire clay wall only one inch thick.

With the present invention the refractory wall can be thick enough to be mechanicallyx sound and yet heat can be dissipated throug the wall at a rate sufficient to maintain the inner surface of the wall at a temperature below the flame temperature in the furnace. In other words, heat can be dissipated through the wall at a rate, sufficient to clause the congealing of slag on the inner surface of the wall and thereby form a protective coating over the refractory. In order to do this w1th a fire clay wall, the wall would be so thin as to be entirely impractical. The invention possesses an advantage over a metal wall, as is sometimes rovided where water cooling is resorted to, or the reason that the temperature of the exposed face of the refractory can be kept much higher than the surface of the water cooled metal wall. This is of definite advantage because in the burning of fuels, particularly suspended fuels such'as oil orI powdered coal, it is desirable to keep the temperature of the refractory walls above the kindling temperature of the fuel, but below the slagging temperature. As above pointed out, the present invention permits the furnace to be operated with the exposed face ofthe refractory at a temperature where the slag will congeal to form a protective coatin At the same time the temperature of t e wall can be kept well above the kindling temperature of the fuel.

The invention therefore secures 4a high degree of efficiency. The ,heat which is dissipated through the Walls is utilized to heat the water in the tubes. The invention secures the advantage lof the usual metal water leg in a boiler, but in an arran ement wherein the temperature of the re ractory can bev fractory coating thereover, saidl refractory coating comprising silicon carbide having a thermal conductivity in excess of .006 ca1./ cma/oC/sec.

2. In a furnace wall, a water circulating passage, and a non-metallic refractory facing over the passage and in intimate contact therewith, said facing being comprised of a silicon carbide refractory which is at least six times as conductive as fire clay.

3. In a furnace wall, the combination with a series of spaced apart tubes with a refractory facing thereover comprised of a plurality yof silicon carbide refractory blocks, said blocks being in intimate contact with and being mechanically interlocked with the tubes, the blocks having a thermal conductivity at least six times lthat of fire clay.

4. In a furnace wall, the combination with a series of s aced-apart water tubes, of. a silicon carbi e refractory facing thereover and `in intimate contact therewith, said facing having a thermal conductivity many times that of ire clay but less than the thermal conductivity of cast iron.

spaced- 5. In a furnace wall structure,-

apart boiler tubes and a facing over saidV tubes of heat-conducting refractory blocks having substantially rectangular fiat front faces, thel width of which is substantially equal to the distance between the tube cen-- ters, the blocks having an extension on thel rear thereof projecting between the tubes,

one side of the extension having a semi-circular recess therein'ada ted to fit around the tubes, the other side o -the extension bein tap'ered,.said blocks bein laid in horizonta courses with the ends t ereof' inv abutting relation,the blocks in each course being reversed with vrespectv to those of adjacent COUI'SGS.

6. In a furnace structure having spaced-- apart boiler tubes in the wall thereof, a heatconducting nonmetallic refractory facingv therefor comprised of j substantially rectangular' blocks'with fiat faces and squared ends, the width of the face being ,sub-

stantially i equal to the distance between' the tube centers, said blocks having an extension on the rear face thereof projecting between the tubes, said extensions having a semi-circular recess in one side thereof to fit around the boi1er`tubes,'said blocks having one end thereof pro'ecting beyond the center of one tube and aving the other end abutting against the end of the next adjacent block, said blocks being laid in horizontal courses, with the blocks of one course reversed with respect to the blocks of the adjacent courses whereby a breaking of joints is secured.

7. In a furnace structure having spacedapart boiler tubes in the wall thereof, a heatconducting nonmetallic refractory facing therefor comprised of substantially rectangular blocks with flat faces and squared ends,

the width of the face being substantially -equal tothe distance between the tube cenasv against the end of the next adjacent block,

said blocks being laid in horizontal courses, with the blocks of one course reversed with respect to the blocks of the adjacent courses.

whereby a breaking of oin'ts is secured, the

top face of each block ing provided with a rejection, the bottom faces of the blocks being provided with a recess adapted to receive the projection of an adjacent block.

In testimony whereof I have hereunto set my hand. Y

FRANK J. TONE.

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