US1902951A - Furnace equipment - Google Patents

Description

Patented Mar. 28, 1933 UNITEDHSTATES PATENT orrlcs WILLIAM A. DARRAH, or CHICAGO, ILLINOIS FURNACE EQUIPIVIENT Application filed January 7, 1929, Serial 330,870. Renewed. August 12, 1932.

This invention relates to equipment and methods for constructing furnaces and other combustion devices. It is particularly applicable to furnaces used for'heating air or other gases in the class of equipment known as heaters or air heaters. My invention, however, may be aplied to many other purposes such as the construction of furnacesft'or heating steel, ceramic material, etc, or for baking, drying and other purposes.

Some of the objects of this invention are to provide economical, simple and efficient.

means for constructing combustion devices, which will be durable, efficient and relatively inexpensive. Another object of this invention is to provide means for reducing the depreciation of combustion chambers which has hitherto been relatively high. My invention also makes it relatively easy to repair or rebuild combustion devices in part on the sectional principle instead of making it necessary to rebuild the entire structure. Other objects of this invention will be apparent from the specification, claims and drawings.

In order to illustrate my invention most effcotively I have shown; one form of structure in accordance with my principles applied to a furnace for heating air or air heater. It will of course be understood'that the principles and features of construction illustrated here may be applied in many other ways to other devices without departing from the scope of this invention.

My invention is designed to provide equipment which permits ready expansion of component parts when subjected to relatively high differences of temperature.

Referring to the drawings: i Figure 1 shows a front elevation of one form of air heater constructed in accordance with my invention,

Figure 2 shows diagrammatically a side elevation of the same air heater, while Figure 3 shows a plan view of my device;

Figure 4 shows in perspective a detail of chamber 11 and is preferably 'located'near one of the expansion blocks as illustrated i Figures 1, 2 and 8,

Figure 5 shows in perspective a detail of a slightly modified form which also comes within the scopeof-my invention,

Figure 6 shows a portion of a combustion chamber constructed 1n accordance with my invention but slightly modified from the ar- V rangement shown in Figure 3.

The equipment consists of a shell or housing 1 which may be constructed of steel, brick or other building material as desired. I prefer apply insulation as shown by 2, 3 and 4. The insulation may be any of the well known materials such as magnesium carbonate, .infusorial earth and similar materials. The housing may be reinforced by structural steel, buck stays, 5, 6, 7, 8, 9 and ldas shown.- A combustion chamber preferably constructed of highly refractory material. such as silicon carbide is indicated by 11. The floor of air heater 1 may be constructed of ordinary fire brick or concrete as indicated by 12 and in a'similar manner the floor of the combustion chambermay be constructed of firebrick or othermedium graderefractory 13 and preferably covered in the hotter portion with a layer of'sand or other comminuted refractory 14. Inorder to provide means for maintaining the lower portion of combustion chamber 13 cool, I provide a series of airports 1 5, 16 and 17, arranged in a. manner to'be'described subsequently. The combustion chamberll is preferably constructed with vertical walls 18 and 19 and a covering. in the form of a tile or arch 20.

The combustion chamber 11 is surmounted by a secondary combustion chamber 21 which in most cases may be constructed from fire,

restrict the flow of products of combustion from the. combustion later to be described. t I Aburner 26 arranged for'oil, gas, powdered coal, etc., is placed at one 'end of combustion chamber for reasons the floor 14 of the combustion chamber;

An opening or air entering port 27 is provided in one portion of the heater housing and an air leaving port 2 8 is provided at an-' other portion of the heater housing. I A movable by-pass damper 29 connecting to operating handle is provided within the heater housing in such a location that by moving said damper 29 variable portions of the air 'which enters through port 27 may be bypassed directly to port 28, the balance being caused to circulate around the outside Walls of combustion chamber 11, thereby heating the air or circulating gases and partially cooling the combustion chamber walls.

In operating a device of this kind, the walls of combustion chamber 11 particularly walls 18 and 19 and to an appreciable extent walls 22 and 23 become intensely heated. Manyrefractory materials which will withstand high temperatures are subject to considerable expansion under heat and some refracto-riesare itis constructed, it is highly desirable to provide a system of expansion joints throughout the structure.

It is not sufiicient in the case of even relatively. small cevices to provide for expansion joints at each end, as even in this case growth or expansion will take place within the interior of various walls, causing warping, cracking and destruction of the "material.

To overcome this diificulty, I have provlded a series of column tile 31, one form of which is shown in perspective in Figure 4 and an alternative one in Figure 5. The socalled column tile are named for the reason that they are used to form a relatively permanent column or pier which carries a considerable portion of the load of the structure and retain the side walls in position without restricting other expansion. The column tile 31, therefore are provided with grooves or re-entrant corners 32, 33 arranged to engage with corresponding corners .34 and 35 of wall tiles 36, 37 etc. At the end of the combustion chamber I may provide a vertical wall 38 carryingcolumn tile 39 and 40 at its corners, where the combustion chamber 11 connects with the front wall 41 of the heater and also provide expansion joints indicated by 42 and 43 similar in construction to joints provided at39and40. m

In order to prevent walls 18 and 19 from spreading I provide a series of stretchers ortile as for example 44 and 45 which serve to hold walls 18 and 19 from moving outward.

Arch 20 of course serves to hold the walls from moving inward as well as the fact that they are interlocked with foundation 13 as shown. Further arch 20 is provided with a series of expansion joints 46,47 and 48 which if desired may be covered with brick or tile 49, 50 and 51.

. Referring to Figure 5 column tile 52 is provided with two openings or grooves 53 and 54 which serve to retain the wall tile in position in the same manner as in the cases of column tile 31. In the case of column tile 52 the ends of the wall may be cut at 90 instead of on a bevel as in the case of column tile 31. V

Column tile 31 may beplaced with the extending portion either in the air space'as shown in Figure 3 or inthe combustion chamber as shown in Figure 4. Further the stretcher tile 44 and 45 may be placed with I their greatest width horizontal asshown in Figure 3 or arranged as indicated by56, 57 and 58 with their greatest dimension vertical. Stretcher tile 44 and 45 may be supported in any manner as for example at one end b a brick-59 corbeled out from the wallof the air chamber and atfthc other end by a brick 60 corbeled out from the combustion chamber .wall. I find it convenient to provide a dovetail or interlocking arrangement as shown by 61 in Figure 4 permitting the individual column tile to be locked one to the other, thus preventing lateral or horizontal displacement. I

Inoperating a device constructed in ac- ;ordance with my invention, fuel is delivered into combustion chamber 11 from burner 26 and the greater portion of the combustion orv dinarily takes place in the lower part before the productsof combustion enter the secondary chamber 21. This arrangement insures that "the combustible materialwill be completely burned producing no soot or dirt, the distance of travel through the combustion chamber the greatest section of the com bustionv chamber both serving tocontrol the time that the combustible materials remain in the hot zone. It will be of course understood that combustion of the more difficult portions of the fuel substantially stops as soon as the temperature to which the fuel is subjected falls below a definite value. I

In actual operation air heaters of this kind are frequently operated under such .condi-.

tions that the air pressure within the heater is lower than the pressure of the atmosphere outside. Such a condition would result in a tendency to draw the products of combustion out of the combustion chamber too rap .idly and before combustion has'b-een completed. The retarding wall 25 serves to overcome this difliculty by restricting the opening from combustion chamber 21. The layer of sand or'comminuted material 14 on the lower portion of combustion chamber 11 serves to provide a readily expandable protection to the floor of combustion chamber 11, thus making it unnecessary to provide elaborate expansion means in this portion of the device. Further the cooling ducts 15, 16 and 17 serve to cause the flow of air beneath the floor of combustion chamber 11, thus further reducing the temperature of the floor. This arrangement is of considerable importance especially in'those cases in vhich the heater may be constructed on a wooden or concrete floor. IVithout means of tlie'kind described, the floor would be charred and the concrete disintegrated, thus not only causing a serious heat loss, but resulting in a failure of the structure.

It will be apparent that equipment of the kind described, when in the hands of the average plant operator, will be rapidly raised from a very low ten'iperature up to a. maximum temperature frequently exceeding 2000 F. within a period of fifteen to thirty minutes. Such a change in temperature causes the strains and expansion previously mentioned and is one of the reasons for the necessity of the type of structure here disclosed.

In the device which I have invented the major portion of the load of the structure is carried on the column tile as shown, the

wall tile normally carrying a relatively slightload or in some cases merely their own weight. Under these conditions, each wall tile is free to expand as required independently of the balance of the structure. By allowing each portion of the structure'to expand independently of the assembly the tendency for warping, cracking and other defects are largely overcome. v

It will, of course, be understoodthat a structure in accordance with my invention may be constructed, using silicon carbide, aluminum oxide, chrome oxide, magnesite and other refractories, although I have found that silicon carbide is well suited for this work and the structure shown is particularly adapted for this material.

In addition to providing great mechanical flexibility the device which I have shown provides a high degree of thermal. flexibility in that a wide variation may take place in the volume of fuel burned in the combustion chamber without seriously affecting thefpe'rformance of the equipment. The device is also quite flexible from the standpoint of handling air or other gases in that, the air which is being heated may be caused to pass around the combustion chambers in the space provided, therefore, or above the combustion chamber, or the air may be by-passed directly from the entering port 27 to the leavin port 28, the adjustment used depending of course upon the volumes of air or gases being heated, desired temperatures, greatest sectional area available or other obvious factors. The

use, however, of by-pass damper 29 or the equivalent is of considerable importance in the commercial operation of this equipment.

Itis not always easy to obtain absolutely clean combustion so that no soot or dirt re- Inasmuch mains in the combustion gases. as this equipment is frequently employed in connection with drying, baking or heating materials which are light in color and which must not be discolored,'absolutely clean combustion is essential. Cleanliness of combustion is obtained only when all conditions are correct. Somefactors are of more importance than others, however, and one important point is to maintain a high and uniform temperature within the combustion chamber. I have found that it is not satisfactory to maintain a high temperature only at the dis charge end of the combustion chamber. I

have even found that a high temperature at ble for clean combustion are obtained when steps are taken to insure that the portion of the combustion chamber around the burner i sintensely hot. This result may be obtained by constructing the walls of the combustion chamber at this point from material which has the characteristics of great refractoriness combined with a poorer heat conductivity than the balance of the combustion chamber.

"In other words, I may use such refractories as aluminum oxide, silica conipounds, sillinianite, mullite, etc., for that portion of the combustion chamber adjacent to the burner and extending along the flame for an appreciable distance. I may also obtain the same result by constructing a semi-insulating wall out- 'side the combustion chamber as shown by reference numbers 70, 71 and 72 in Figure 3. Other obvious expedients may be employed such as restricting the flow of air or other gases being heated, so that they do not re;

move as much h-eatfrom that portion ofthe combustion chamber adjacent to the burner as they do from other portions. For example air or other gases to be heated ordinarily would enter in portion 74 and travel substantially horizontally through passages .75,

76, 77 and 78. 7 Some of the air or gases being ieated may by-pass through adj ustable'opening 79and leave by exit port 80. Other of the circulating gases being heated will travel;

upward through openings 81, 82, 83, 84, 85,

lid

etc., thus serving to partially cool the walls 36, 37, etc. Obviously the size of the openings between the supporting tiles such as 44 preferably arranged to coincide so that the combustion chamber is in effect constructed from a series of short lengths. This is not absolutely essential however. It is quite advantageous to arrange so that arch 20 is carried primarily on column tile 31 or the equivalent instead of upon the intermediate portions of the wall, although the particular details of construction depend to some extent upon the obvious features of design.

I have found that the arrangement of the burner materially below center line of the V combustion chamber is of decided advantage in obtaining a relatively uniform heat distribution throughout the combustion chamber. It will be obvious that the hot products of combustion being lighterthan air tend to rise and by placing the burner initially appreciably below the center line, the rising tendency of the products of combustion is partially compensated for.

It should be understood that many obvious modifications may be made in the arrangement, dimensions and structure described and shown here without departing from the scope of my invention. Various materials may be substituted for those specifically mentioned and many modifications may be made in the shapes and proportions in the average parts of the equipment. 7

Having now fully described my invention, what I claim as new and wish to secure by Letters Patent in the United States, is as follows:

1. A gas heaterconsisting of a housing, a combustion chamber of refractory material located therein, a passage for gas being heated along said combustion chamber, a fuel supply device delivering fuel to said combustion chamber, said combustion chamber beingcon structed with a series of column members and a series of intermediate panel members, said panel members being arranged to eX- pandindependently of each other, and a restricted'opening in said combustion chamber connecting to a space outside said combustion chamber and within said housin 2. A heater consisting of a housing, a combustion chamber therein, passages for the material being heatedaround said combustion chamber, ports in said combustion chamber connecting the latter to the interior of said housing and'means for'controlling the in sucha manner that the heat conductivity of the portionof said combustion chamber adjacent said fuel supply device is higher thanthe heat conductivity of the balance of said combustion chamber.

4. A combustion chamber consisting of a series of supporting columns an archcarried by said columns and a series of independently eXpansible panel units between said columns forming a substantially air tight continuous wall for said combustion chamber.

5. A combustion chamber constructed of highly refractory material arranged in a series of independently expansible units, a floor for said combustion chamber formed of comminuted material, a fuel supply device for said combustion chamber arranged to deliver fuel and air at a point appreciably below the middle portion of said combustion chamber.

6, In a heater for gases, a burner for sup-' plying fuel to the interior of said combustion chamber, a refractory combustion chamber constructed from a series of independently expansible refractory units joined together to prevent appreciable leakage, and a series of supports for maintaining said individual units in permanent alignment,

7. A combustion chamber consisting of a series of independently expansible units interlocked to prevent appreciable leakage and constructed from highly refractory materials, a fuel supply device therefor, said combustion chamber'being arranged to permit lesser heat flow from the portions an appreciable distance away from the fuel supply device than from the portions adjacent said fuel supply device.

8. The process of burning fuel which consistsin delivering said fuel to one end of a closed highly refractory combustion cham-.

ber, restricting the outflow of combustion gases from said combustion chamber, and re stricting the flow of heat fromthe portion of said combustion chamber away from the fuel supply device. i

' 9. A gas heater consisting of a housing, a combustion chamber within said housing, an inlet in said housing for said gas being heated, an outlet in said housing for said gas,

a duct for said gas in contact with said com- 10. A gas heater consisting of a housing, a-I

combustion chamber within said housing, an

inlet in said housing for said gas being heated, an outlet in said housing for said gas, a duct for said gas 1n said housing in contact with said combustlon chamber and a by-pass duct for said gas in said housing between said inlet and said outlet and means to control the relative flow of said gas in said ducts.

11. A gas heater consisting of a housing, a combustion chamber within said housing, an inlet in said housing for said gas being heated, an outlet in said housing for said gas,

a duct in housing for said gas in contact.

with said combustion chamber and a by-pass duct located in said housing for said gas and connecting said inlet and said outlet and means to control the relative flow of said gas in said first mentioned duct and said by-pass duct.

12. In a gas heater a combustion chamber, a housing enclosing said chamber, a duct in said housing directing a portion of the flow of gas being heated in contact with saidcombustion chamber and another duct in said housing bypassing said directing duct and means to control the relative flow of gas in said duct system.

13. A multiple passage combustion chamber consisting of a series of relatively thick columns retaining a series of relatively thin intermediate panels arranged for independent expansion, a cover for said combustion chamber constructed in sections to permit individual expansion of each section, and a burner for supplying fuel into said combustion chamber, near one end, and a restricted outlet near the other end.

14. A gas heater consisting of a housing, a

combustion chamber therein constructed. of

refractory material and arranged in inde pendently expansible longitudinal sections, independent bracing members for said units extending from said housing to each of said independent sections, and a passage for gas being heated about said combustion chamber and in contact therewith.

15. In a gas heater a combustion chamber constructed of a series of independently eX- pansible units of highly refractory material, a burner for delivering fuel into said combustion chamber, a passage beneath said combustion chamber for removing heat there from, and a restricted outlet from said combustion chamber into the space around said combustion chamber and arranged so as to maintain a higher pressure in said combustion chamber than in said surrounding space.

16. In a gas heater a combustion chamber constructed of independently expansible units of silicon carbide, a burner for delivering fuel into said combustion chamber, a passage below said combustion chamber for cooling the lower portion therein and a restricted outlet from said combustion chamber into the space around said chamber and arranged so as to maintain a higher pressure in said chamber than in said space.

17. A gas heater consisting of a housing, a combustion chamber within said housing constructed of independently expansible units interlocked, one to the other, in a'manner to prevent appreciable leakage into or out of said combustion chamber, a burner arranged to deliver fuel into said combustion chamber, bracing members from said housing to said combustion chamber and ducts for removing heated gases from said combustion chamber. s

18. A device for heating gases consisting of a housing, a combustion chamber therein and spaced from'said housing for a portion of its surface, said combustion chamber being formed of independently eXpansib-le refractoryunits, independent, laterally extending supports for said units of said combustion chamber, and a passage for gases being heated adjacent said combustion chamber and within said housing, and a restricted port connecting said chamber with said housing.

19. A combustion chamber consisting of a series of independently expansible refractory units interlocked to prevent leakage, a gas passage outside of and adjacent said combustion chamber, a. fuel supply device near one end of said combustion chamber, and'an upper passage for "products of combustion above said combustion chamber and communicating with it, and a restricted opening near the end of said upper pasasge connecting said combustion chamber with said gas passage, said restricted opening having a lesser area than the cross section of said combustion chamber and arranged to maintain a greater pressure Within said chamber than outside same.

20. A combustion chamber consisting of two substantially horizontal passages arranged one above the other, said passages being constructed of independently expansible units interlocked together to prevent leakage, a duct outside said combustion chamber, a fuel supply device near one end of said combustion chamber and a restricted opening through the Walls of the upper portion of said combustion chamber near the end and communicating with said passages, said restrict ed opening being less in area than the cross section of said combustion chamber, thereby maintaining a higher pressure in said combustion chamber than in said passages.

21. In a combustion chamber a Wall of refractory material having oneside substantially unbroken and composed of a series of columns supporting intermediate panels, a

housing and arranged to bypass said direct ing duct.

23. A gas heater consisting of a housing, a combustion chamber in said housing, ducts in said housing beneath and above said com bustion chamber, and a bypass duct in said housing, arranged todirect a controlled portion of gases to be heated away from contact with said combustion chamber.

24. A gas heater consisting of a housing, a combustion chamber in said housing, an inletiand an outlet to said housing, a duct along said combustion chamber in contact With the sides thereof, a duct connecting said inlet and outlet directly, and means for controlling the relative volume of gases passing alongside said combustion chamber and the relative volume of gas passing directly from said inlet to said outlet.

25. In a gas heater a combustion chamber, a burner for delivering fuel into said combustion chamber, a ductbeside said combustion'chamber for cooling a portion thereof, an inlet to said housing, an outlet to said hous- I ing and means for proportioning the amount of gas being heated which cools said combustion chamber and the amount Which passes directly from said inlet to said outlet.

WILLIAM A. DARRAH.

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