US2409873A - Heat exchange - Google Patents

Description

Patented Oct. 22, 1946 HEAT EXCHANGE Howard Y. Lankford, Gary, Ind., assignor to Carnegie-Illinois Steel Corporation, a corporation of New J ersey Application June 6, 1945, Serial No. 597,922

8 Claims.

This invention relates generally to heat exchangers, and more particularly to an improved construction and arrangement of the bricks forming the checkerwork thereof.

While not limited thereto, the'herein claimed invention has its greatest utility in the checkerwork used in hot blast stoves of the type used to preheat air supplied to support combustion and bring about reducing reactions in a blast furnace.

As is known to those skilled in the art, such hot blast stoves are in the nature of huge brick-lined steel sheels approximately 20 feet in diameter and 80 feet or more in height. Within the lining it is customary to provide a division wall defining a combustion chamber, and the balance of the space is substantially filled with refractory brick checkerwork forming a system of flues. In normal operation blast yfurnace gas is burned in the combustion chamber of the stove and the stack draft draws the hot burned gases through the multiplicity of fluesformed by the checkerwork. As the gas is passed through the checkerwork, each brick absorbs and stores part of the heat. Periodically the supply of combustion gas is cut 01T and the blast main is opened, thereby admitting cold air under pressure to the stove. The cold air passing through the many flues of the checkerwork absorbs heat therefrom, thence flows to the hot blast main leading to the bustle pipe of the blast furnace in a manner well known to those skilled in theart. n

Practice has demonstrated that although blast furnace gas passes through primary washers before being introduced into the hot blast stove, there is still considerable dust entrained in the gas which has a tendency to precipitate on various ledges formed by conventional forms of checkerbrick. Checkerbrick heretofore used are open to various objections, the chief of which is that they are of such form that they promote the accumulation of objectionable dust deposits.

An object of the present invention is.to provide an improved checkerwork structure for hot blast stoves, overcoming inherent shortcomings in the prior art.

A further object is to provide an improved brick so constructed and arranged that it furnishes an increased heating surface for the checker chainber.

Another object is to provide checkerwork formed of bricks having portions constructed and arranged to create a turbulence in the hot gases or air passing through the iiues.

A further object is to provide means to create a turbulence of hot gases or air in the flues in order to force the hot gases or air into all corners and crevices of the flues to thus improve utilization of all available heating surfaces and brick. Volume, thus making for an increased rate of heat exchange.

Another object is to provide an improved checkerbrick so constructed and arranged that an interlocking effect is obtained between adjacent bricks to thus prevent relative movement or creeping of the bricks under the influence of expansion and contraction due to alternate heating and cooling.

As will be more fully apparent hereinafter, the above and related objects are made available by the use of a novel form of Checkerbrick of generally rectangular prismatic form whose horizontal top and bottom faces are flat, whose vertical end faces are also flat, and whose upright side faces have one or more shallow pyramidal laterally projecting portions which project into the flues formed by the juxtaposed brick. The pyramidal projections serve to provide more heating surface than that of a standard brick, and they also function to create a turbulence of the air'or gas flowing through the checkerwork. This turbulence is advantageous as it dislodges precipitated dust and thus more of the hot gas or air is brought into intimate contact with the surfaces of the Checkerbrick, thus increasing the efficiency of the heat transfer.

For a more complete understanding of the invention, reference should be made to the accompanying drawing, the following detailed disclosure, and the appended claims.

In the drawing:

Figure 1 is a horizontal section on a small scale through a hot blast stove to illustrate the application of the invention.

Figure 2 is an enlarged fragmentary top plan of a portion of the checkerwork of a hot blast stove embodying the present invention.

Figure -3 is a vertical section on line III-III of Figure 2.

Figure 4 is an enlarged plan view of my improved Checkerbrick.

Figure 5 is a front elevation of the brick of Figure 4. Y

Figure 6 is a vertical end View of Figure 5.

Figure 'I is a perspective view of my improved Checkerbrick.

Figure 8 is a perspective view illustrating the relationship of a plurality of bricks constituting the improved checkerwork.

Referring in detail to the drawing, reference numeral l0 represents the conventional `outer steel shell of a hot blast stove; I2 represents the usual brick lining; and Il represents the wall which with a portion of the lining I2 defines a combustion chamber I6. The balance of the stove is substantially filled with checkerwork such as indicated at I8, this checkerwork being formed of a novel type of checkerbrick best shown in Figures 2 to 6 inclusivev andto be presently described in detail. The bricks are formed of refractory material commonly used in the art.

As will be apparent from Figures 4 to 7 inclusive, my improved checkerbrick is of generallyv rectangular prismatic form having parallel flat top and bottom faces 20 and 22 and nat upright substantially vertical end faces 24 and 26. The upright side faces 2B and 30, instead of being flat like all the other faces described, are equipped with a plurality of shallow pyramidal projections. For the purpose of identification the pyramidal projections of the face 28 are indicated at 2128a and 28h. Likewise the pyramidal projections on the opposite side face areindicated at 30a and 30h.

Between the pyramidal projections 20a and 2W the side face 28 includes a flat portion 26C. Likewise, between the pyramidal projections 30a and 3!)b there is a flat portion 30C. The distance, marked d, between the bases of these projections, is at least equal to the dimension c, so as to provide a seating area substantially equal to the areaof the end faces 2-1Y or 26 of a similarV brick arranged perpendicular thereto. This relationship, as clearly illustrated in Figures 2 and S, provides an assemblage in which the bricks extending lengthwise in one direction are interlocked by the pyramidal projections with tho-se bricks extending perpendicular thereto.

The apexes a and b ofthe pyramidal projections-28a and 28?D are inline, as shown by line .A-A in Figure 5, this line A-A being offset a distance O from a center line B-B located midway between the top face 20 and the bottom face 22 of the brick. By thus offsetting the apexes I-am enabled to lay up `the bricks in such a relationship as tovobtain an increased turbulence. The staggered relationship of the inclined faces v4of the pyramids will be apparent from the enlarged vertical section of Figure 3., The apexes a and b on opposite sides of the brick are in line with -one v I another, as is apparent from Figures to 6. The locations of said apexes of each brick may be said to be in line with one another and offsetfrom `the center plane B-B paralleling the top andbottom faces of the brick.

-In Figure 3 the apexes a Aof the lbricks-shown in 4end elevation correspond in location; to `the showings of said apexes in the detail Views of Figures 4, through 7, while the bricks shown` cut by the plane of section in Figure 3 are inverted; that is, their apexes are oifsetdownwardly from the center line of the brick. As thus arranged, the apexes a of the sectioned bricks may be said to be staggered vertically with relation yto thefapexes a'of the bricks disposed perpendicular thereto.

Otherwise expressed, the apexes a and a .arejoffset vertically equal distances corresponding to the 4dimension o on opposite sidesl of a horizontal .plane B-B passed through the bricksmidway ,between the top and bottom faces thereof. The presence passed through the checkerwork which is effective to dislodgev dust which may tend'to precipitate on the checkerbrick, and the net result is that all 4 exposed faces of the checkerbrick are forcibly impinged by the air or gas, thus effectively promoting and increasing the heat transfer. The turbulence caused by the pyramidal projections 5 also creates a core busting effect on the gas stream; that is to say, the turbulence tends to break up any vortex or core-.like denseaccumulation of dust particles inthe gaseous stream.

Comparing a standard checkerbrick with that vof my invention as herein described, it is found that a standard 8% inch by 6 inch by 21/2 inch brick such as commonly used has a heating area of 70.5 square inches. The total volume of all checkerbricks that can now be installed with a basket-weave. pattern in a typical furnace in a typical hot blast stove is 13,900 cubic feet, with a total heating surface o-f 93,606 square feet. In comparison, a brick of my invention measuring approximately 83/8 inches by 6 inches by 21/4 inches has a heating area of 76.06 square inches. By using my improved brick in a comparable stoveinstead of the standard brick using the same basket-weave pattern, the total volume of checkerbrick would be 15,056 cubic feet, having a combined heating surface of 109,855 square feet. Thus an important advantage of my invention is an increase of approximately 8 per cent (7.9) in the effective heating area of a stove of 'comparable size. The flue openings with thestandard bricks are 3 inches by 3 inches, or 9 square inches. My improved brick will have the same iiue area at the top and bottom edges of vthe brick, but at the intermediate portions in the region of the apexes of thepyramids the flue area will be 7.1 square inches. Thus the air or gas flowing through the ues formed by my brick will exert somewhat of a venturiv effect, which will set up the turbulent action above mentioned, effective to dislodge accumulated dust and thus 40 increase the over-all efliciency of the hot blast stove.

Having thus described my invention,V Vwhat I desire to secure by Letters Patent isoutline'd' in the appended claims.

I claim:

.1. A heat exchanger including checkerwork comprising a plurality of bricks of generally rec-` tangular prismatic form whose horizontal top and bottom faces are flat, whose vertical ehd faces 50 are also fiat, and certain of Whose upright. side faces each have at leastone shallow pyrainidal laterally projecting portion. l v2. The heat exchanger as defined in claim l,

v further characterized in that theV apex o-f said 55 pyramidal projection is offsetrfrom a centeplan'e paralleling the .top andvbottorn faces `of the brick. `3. A heat exchanger including checkerwork comprising a plurality of substantially identical bricks of generally rectangular prismatic form whose horizontal top and bottom facesaie 'flat,.

whose vertical end'faces arealso flat, andwhose vvertical side faces each have -a plurality of spaced-,apart pyramidal projections.

Y 4. The heat exchanger of claim 3, further` characterized in that the .apexes of the pfyramidal projections on opposite sides of the brick are in line with one another and are offset fromacenter plane paralleling they top Vand bottom faces .of the brick. 'I

5. A heat exchangerY including checker-work comprising a multiplicity -of substantially identical bricks of generally rectangular prismatic form laid up b-asket'weav'e fashion, With end-'faces f certain of the bricks abutting side facesof 75 other bricks disposed perpendicular thereto, all

, 5 of said bricks having fiat top, bottom, and end faces, the top and bottom faces being horizontal and the end faces being vertical, the side faces of all said bricks having shallow pyramidal pro.- jections which thus extend into the flues defined collectively by the bricks, said pyramidal projections being eifective to create a turbulence of air or gas passed through said ues.

6. The heat exchanger as defined in claim 5, further characterized in that the side faces of said brick between the pyramidal projections include a flat portion whose extent is at least equal to the distance between the side faces of the brick as measured horizontally, so as to form a seating surface for the upright end face of an identical brick.

'7. A checkerbrick for use in a heat exchanger, comprising a substantially rectangular prismatic refractory body having substantially parallel fiat top and bottom faces, iiat end faces substantially perpendicular thereto, and side faces each having a pair of pyramidal projections with a flat area between them of substantially the same size and shape as the end faces of the brick.

8. The brick as defined in claim 7, further characterized in that the apexes of said pyramidal projections lie in a common plane offset from a plane midway between the top and bottom face of the brick.

HOWARD Y. LANKFORD.

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