US2660419A - Apparatus for introducing air to burners of reversing type furnaces - Google Patents

Description

. HARTNE RODUCING A Nov. 24, 1953 J. Y 2,660,419

- APPARATUS FOR IR TO BURNERS OF REVERSING TYPE FURNACES 3 Sheets$heet 1 Filed March 9, 1950 J. L. HARTNEY R INTRODUCING AIR TO BURNERS Nov. 24, 1953 APPARATUS FO OF REVERSING TYPE FURNACES 3 Sheets-Sheet 2 Filed March 9, 1950 FIG. 2..

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APPARATUS FOR INTROD INC AIR TO BURNERS OF REVERSING TYPE FURNACES' Filed March 9, 1950 V 3 Sheets-Sheet 3 Ala -470//7e r/.

Patented Nov. 24, 1953 BURNERS NACES OF REVERSING TYPE FUR- James L. Hartney, Chicago, 111., assignor to United States Steel Corporation, a corporation of New Jersey Application March 9, 1950, Serial No. 148,619

7 Claims. (01. 263-45 This invention relates to improved, apparatus for introducing air to the :burners of reversing type furnaces.

An object of the invention is to provide improved apparatus for pre-heating compressed air and selectively directing such air to either burner or set of burners in a reversing type furnace.

A further object of the invention is to provide improved systems for directing flow of compressed air from a heating device to either burner or set of burners in a reversing type furnace and automatically maintaining continuous flow of such fluid through the heating device during changeovers and thereby preventing overheating of the heating device.

A further object of the invention is to provide improved apparatus utilizing pre-heated compressed air as atomizing fluid for liquid fuel in open hearth furnace burners, thereby enhancing furnace efficiency over that obtained with steam as atomizing fluid.

In accomplishing these and other objects of the invention, I have provided improved details of structure, a preferred form of which Y shown in the accompanying drawings, in which:

Figure 1 is a schematic view of a reversing type furnace equipped with an improved apparatus for introducing pre-heated air to the burners embodying features of the present invention;

Figure 2 is a top plan View with parts broken away of a preferred construction of heat exchanger used in the apparatus shown in Figure 1;

Figures 3 and 4 are vertical sectional views of the heat exchanger taken respectively on lines III-III and IV-IV of Figure 2;

Figure 5 is an enlarged vertical sectional view of the heat exchanger showing the wall construction;

Figure 6 is a side elevational view with parts broken away of a preferred construction of a multiple diaphragm by-pass valve used in the apparatus shown in Figure 1; and

Figure 7 is an exploded sectional view of the operating mechanism of the valve shown in Figure 6.

Referring more in detail to the drawings:

In Figure 1 there is shown schematically a reversing type furnace I0, which can be for example an open hearth for manufacturing steel and which has two selectively operable burners I2 and I3 at opposite ends. The furnace is reversed periodically and thus is fired alternately from these two burners, as known in the art. There is shown at 14 an air compressor which directs compressed air through a line [5 to a receiving tank I6. From the tank the air passes via a line 11 into a heat exchanger [8, where the air is heated to a fairly high temperature which is maintained constant or nearly so, Line I! preferably has a pressure regulator l9 and a by-pass valve 20 for said regulator. The furnace, burners, air compressor, receiving tank, and pressure regulator may be of any standard construction; hence no more detailed'description is deemed necessary. The preferred construction of heat exchanger is described more fully hereinafter.

One purpose for which air can be introduced to the burners is as fuel atomizing fluid. In this instance the air is heated to a temperature preferably between 600 and 800 F, commonly being maintained at 700 F. The pressure commonly is maintained between and pounds per square inch, although none of these values are necessarily critical, as long as they are maintained constant or nearly so.

Aline 2| extends from the heat exchanger and branches into lines 22 and 23 which extend respectively to burners l2 and I3. These lines con tain normally closed, pneumatically operated diaphragm type valves 24 and 25 respectively for controlling flow of air to the burners. Inasmuch as these valves may be of any standard construction and per se are not part of the present invention, no more detailed description is deemed necessary, When the furnace is fired from either burner, the appropriate valve is opened and directs air to that burner,

The apparatus comprises a by-pass line 26 which discharges from pipe 2| into the atmosphere and which contains a valve 21. This valve is of the normally open, pneumatically operated double diaphragm type and is more fully described hereinafter. The, apparatus comprises valve operating mechanism which automatically opens valve 2'! unless either valve 24 or 25 is open, in which case it automatically closes valve 21. Thus the air continues to circulate through the heat exchanger when valves 24 and 25 are both closed as during changeovers in firing the furnace fromone set of burners to the other, as is done periodically in operation of the furnace. Such circulation is needed to prevent overheating of the heat exchanger, since the temperature of air emerging from the heat exchanger can be fairly close to the maximum temperature which the heat exchanger can withstand. Also if the heat exchanger is overheated, there is subsequent difficulty in adjusting the air temperature to the desired constant.

The valve operating mechanism includes a control air line 28 which is connected with line I! and thus receives compressed air from tank It. Line 28 preferably contains a filter 2 9 and a pressure reducing valve 30, which both may be of any standard construction. Line 28 extends to a four-way control valve 3|, to whichare also connected an exhaust line 32 and two lines 33 and 3.4 that extend to. valves 24 and 25 respectively for operating these valves. Valve 31 has settings tov connect line 28 with either line 3301' 34 and at the same time connect the other of these lines with exhaust line 32. Inasmuch as valves having such settings are known and per se are not part of the present invention, no more detailed description is deemed necessary. Whenever the control valve admits air to line 33 or 34, valve 24 or 25 opens and air flows through that valve from the heat exchanger to one of the burners.

Air lines and 35 extend from air lines 33 and 34 respectively to the by-pass valve 21. Whenever control valve 3| is actuated to relieve the pressure on the diaphragm of either of the normally closed valves 24 or 25 and thus close this valve, it also relieves the pressure that maintains the normally open by-pass valve closed. The by-pass valve thereupon opens and maintains air circulation through the heat exchanger via by-pass line 26 and thus prevents overheating of the heat exchanger. The by-pass valve remains open until pressure is applied to the diaphragm of the other valve 24 or 25 to open this valve. At the same time pressure is applied automatically to the by-pass valve via line 35 or 36 and thus this valve closes, and circulation is resumed to one of the burners.

A preferred construction of heat exchanger 18 is shown in detail in Figures 2 to 5. The heat exchanger comprises an enclosure whose walls are formed of a heat insulation lining 31 supported by longitudinally extending channel-shaped casing members 38. Pairs of end plates 39 are interposed between successive tiers of insulating material and casings (Figure 5). A spacer 48 and a horizontal bafiie 4| are interposed between each pair of end plates 39. The baffles are sup ported cantilever fashion from the end plates and thus are free to expand and contract. The baffles extend alternately from opposite sides into the interior of the heat exchanger as best shown in Figure 3 and define a sinuous course for circulating waste products of combustion from the furnace from which the heat is derived.

A fan 42 draws a portion of the products of combustion from furnace l0 into the lower portion of heat exchanger 18 through an inlet 43. These products of combustion pass through the heat exchanger in the course defined by bailles 4| and are expelled at the top through an outlet 4t into a stack 45 (Figure 1). The portion of such products which pass through the heat exchanger is governed by a damper 43 preferably located in outlet 44.

The compressed air is maintained at a substantially constant temperature, which may be controlled by regulating damper 46. Line 21 contains a temperature indicating device 41 and line ll contains a flow indicating device 48. Damper 46 is regulated in accordance with readings on these indicating devices to maintain a flow of products of combustion through the heat exchanger sufiicient to heat the air to just the desired temperature. Although the damper may be regulated manually, the aparatus preferably includes metering controls, connected to the temperature and flow indicating devices 41 and 48 but not shown, for regulating the damper automatically. Inasmuch as such controls are known and do not per se form a part of the present invention, no more detailed description is deemed necessary.

The heat exchanger has a pair of manifolds 49 and 50, each of which is divided by partitions 5| and into a plurality of superposed compartments (Figure 4). The compartments on opposite manifolds are connected by U-shaped tubes 52, which extend between baffles 41 into the path of circulation of the products of combustion. Unheated compressed air is introduced from line I! to the top chamber of manifold 49, whence it passes through tubes 52 to the top chamber of manifold 50. Such air then returns to the second chamber of manifold 43 via the next set of tubes 52. Air circulation betwen the manifolds continues through the entire height of the manifolds and the heated air finally discharges from the bottom chamber of manifold 49 into line 2i, from which it may be directed to either set of burners as already explained.

Figures 6 and 7 show a preferred construction of by-pass valve 21. Said valve includes the usual body, stem and closures, which are not shown in detail, since they may be of any standard construction. The operating mechanism for this valve includes a pair of superposed flexible diaphragms 53 and 54 housed within the usual pressure chamber 55. A spring 56 normally urges the diaphragms to a retracted position against the back wall of the chamber and normally maintains the valve open. Air may be admitted to the space behind diaphragm 53 to close the valve, or air may be admitted to the space between the two diaphragms also to close the valve. The first of these spaces is connected to line 36 by a connection 51 in the back wall of the chamber. The second of these spaces is connected to line 35 by a connection 58 situated in a spacer ring between the two diaphragms. The first space preferably has fillers 60 and the second fillers 6| to separate the diaphragms slightly from the end wall and from each other when either is retracted. Thus it is seen that the by-pass valve is closed whenever air is admitted behind either diaphragm on closing of either valve 24 or 25.

While the valve just described is particularly uited to use in the present instalaltion, similarly constructed valevs may be employed in other installations where it is desired to operate a valve from any one of a multiple of sources. Such valves may be either of the normally open type, as illustrated, or of the normally closed type.

From the foregoing description, it is seen that I have provided an eflicient apparatus for introducing pre-heated compressed air to either burner or set of burners in a reversing type furnace. The air is continuously heated by heat derived from waste products of combustion and circulation of air is automatically maintained at all times including during changeover periods. Thus I have provided a system in which there is no likelihood of parts being overheated by failure to maintain air circulation.

The present application is a continuation-inpart of my copending application Serial No. 47,034, filed August 31, 1948, now Patent No. 2,587,153, issued February 26, 1952. The double diaphragm valve forms the subject matter of application Serial No. 160,067, filed May 4, 1950, which is a division of aforesaid application Serial No. 47,034. The method forms subject matter of application Serial No. 357,739, filed May 2'7, 1353, which is a division of the present application.

While I have shown and described only a single embodiment of the invention, it is apparent that modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims,

I claim:

1. In a reversible furnace having a pair of selectively operable burners for firing the furnace, an apparatus for supplying pre-heated compressed air to said burners comprising a source flow of air through said heating device during changeovers in firing the furnace from one of said burners to the other.

2. In a reversible furnace having a pair of selectively operable burners for firing the furnace, an apparatus for supplying pre-heated compressed air to said burners comprising a source of compressed air, a heat exchanger for preheating the air, a line for directing Waste products of combustion from the furnace through said heat exchanger for heating the latter, lines for directing air from said heat exchanger selectively to said burners, valves in said lines for controlling fiow of air therethrough, a by-pass from said heat exchanger discharging into the atmosphere, a valve in said lay-pass, and a pneumatic operating mechanism connected to the valves in said lines and the valve in said by-pass automatically opening the valve in said by-pass unless the valve in one of said lines is open, thereby automatically maintaining flow of air through said heat exchanger during changeovers in' firing the furnace from one of said burners to the other.

3. In a reversible furnace having a pair of selectively operable burners adjacent opposite ends through which the furnace is fired alternately, an apparatus for supplying pre-heated compressed air to said burners comprising a source of compressed air, a heat exchanger, means for directing a portion of the products of combustion from the furnace through said heat exchanger, means for directing compressed air from said source to said heat exchanger, lines for directing air from said heat exchanger selectively to said burners, normally closed pneumatically operated valves in said lines for controlling flow of air therethrough, a by-pass for air from said heat exchanger discharging into the atmosphere, a normally open pneumatically operated valve in said by-pass, and an operating mechanism for simultaneously opening one of said normally closed valves and closing said normally open valve.

4. In a reversible furnace having a pair of selectively operable burners adjacent opposite ends through which the furnace is fired alternately, an apparatus for supplying pre-heated compressed air to said burners comprising a source of compressed air, a heating device for pre-heating air from said source, lines for directing air from said heating device selectively to said burners, normally closed pneumatically operated diaphragm type valves in said lines for controlling flow of air therethrough, a by-pass for air from said heating device discharging into the atmosphere, a normally open pneumatically operated double diaphragm type valve in said by-pass, and a pneumatic operating mechanism for applying pressure behind the diaphragms of said valves for opening the normally closed valves and closing the normally open valve, said operating mechanism automatically releasing or applying pressure to the valve in said Icy-pass on release or application of pressure to the valve in either of said lines, thereby maintaining flow of air through said heating device during changeovers in firing the furnace from one burner to the other.

5. In a reversible furnace having a pair of selectively operable burners adjacent opposite ends through which the furnace is fired alternately, an apparatus for supplying pre-heated compressed air to said burners comprising a source of compressed air, a heating device for pre-heating air from said source, lines for directing air from said heating device selectively to said burners, normally closed pneumatically operated diaphragm type valves in said lines for controlling fiow of air therethrough, a by-pass for air from said heating device discharging into the atmosphere, a normally open pneumatically operated double diaphragm type valve in said by-pass, a control valve, a line connecting said control valve with said source of compressed air, an exhaust from said controlvalve, and lines connecting said control valve with each of said pneumatically operated valves for applying pressure to the diaphragms thereof and opening the normally closed valves and closing the normally open valve, said control valve automatically releasing or applying pressure to the valve in said by-pass on application or release of pressure to the valve in either of said first named lines, thereby maintaining flow of air through said heating device during changeovers in firing the furnace from one burner to the other.

6. In an apparatus for supplying compressed air to burners of a reversible furnace, a device for pre-heating the air, a control connected to said pre-heating device for directing air to either set of burners in the furnace, a by-pass for discharging air from the pre-heating device into the atmosphere, and a valve in said by-pass, said valve having a pressure chamber, a pair of diaphragms in said pressure chamber, means connected to said control for admitting air behind either of said diaphragms for operating the valve, and means normally retracting both of said diaphragms.

7. In an apparatus for supplying compressed air to burners of a reversible furnace, a device for pre-heating the air, a control connected to said pre-heating device for directing air to either set of burners in the furnace, a by-pass for discharging air from the pre-heating device into the atmosphere, and a normally open valve in said by-pass, said valve having a pressure chamber, a pair of superposed diaphragms in said pressure chamber, means connected to said control for admitting air behind either of said diaphragms for closing the valve, and a spring normally retracting said diaphragms.

JAMES L. HAR'I'NEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,414,451 Arthur May 2, 1922 1,907,140 Bartholomew May 2, 1933 2,066,103 Fiorelli Dec. 29, 1936 2,090,771 Whitcomb Aug. 24, 1937 2,171,597 Parker Sept. 5, 1939 2,183,596 Trinks Dec. 19, 1939 FOREIGN PATENTS Number Country Date 903,404 France 'Jan. 15, 1945

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