US2491705A - Open-hearth furnace - Google Patents

Description

Dec. m, 1949 F. s. BLOOM 2,491,705

OP EN-HEARTH FURNACE 2 Sheets-Sheet 2 Filed Feb. 24, 1949 INVENTOR FREDERICK S. BLOOM Patented Dec. 2c, 1949 DPEN-HEARTH FURNACE Frederick S. Bloom, Mount Lebanon Township, Allegheny County, Pa.

Application February 24, 1949, Serial No. 78,180

a Dias. (oi. 263-l) This invention relates to means for heating an open hearth regenerative furnace either with gas alone or with oil alone. Natural or coke oven gas is generally a less expensive fuel than oil and is therefore desirable for the purpose of heating large open hearth furnaces such as those used for making steel. However, the supply of gas is sometimes out oh and it is highly desirable to avoid a shut-down by using some other fuel. While gas-fired open hearth furnaces and oiliired open hearth furnaces are well known in the art and mixtures of gas and oil have been used in both gas-fired and oil-fired furnaces, it has not heretofore been practicable to use gas alone and oil alone alternatively in any one furnace. The problem is to get a proper flame to heat the charge in the melting chamber and at the same time to avoid burning out the furnace lining, particularly the roof lining of the furnace.

A conventional open hearth furnace designed to be heated by oil has a comparatively straight roof and passages of substantially uniform crosssection connected to the ports at either sides of the furnace. it single burner is mounted at each end of the furnace. Gas can be mixed with the oil to some extent but if straight gas is used in either of the burners it has been found that turbulence in the port eliminates the luminosity of the flame and reduces the roof life very substantially. For example, the use of straight gas in a furnace designed for oil has reduced the roof life to approximately 100 heats as compared with 225250 heats when oil was used.

A conventional open hearth furnace designed to be heated by gas, on the other hand, has a downwardly extending knuckle in-the roof of the furnace adjacent each port at either end of the furnace. The passages leading to the ports slope downwardly and progressively narrow as they approach the ports in order to accelerate the speed of the incoming air before it enters the melting chamber. Gas is fed into the passage at relatively low pressure and velocity and the accelerated stream of incoming air serves to direct the naming gas downwardly into the melting chamher. It is not practicable to introduce straight oil through gas burners and if a conventional single oil burner is inserted at each end of a gasflred furnace it has been found that the flame from the oil burner tends to burn away the roof,

thereby greatly reducing the life of the furnace.

My invention makes it possible to heat an open hearth furnace of gas-fired design selectively with gas alone or oil alone andwithout suffering the dvantages mentioned above. My invention E will best be understood by reference to the following detailed description andin the accompanying drawings. I have shown inthe drawings. for purposes of illustration only, a present preferred embodiment of my invention, in which Figure 1 is a sectional side view of one end. of a preferred embodiment of my open hearth furnace (on the line I--I in Figure 2) Figure 2 is a sectional plan view on. the line II-II in Figure 1;

Figure 3 is a partially sectioned plan view of one of the oil burners of my furnace;

Figure 4 is a sectional view on the line Ill-JV in Figure 3;

Figure 5 is a sectional view on the line V- -V in Figure 3; and

Figure 6 is a diagrammatic plan view of the fuel oil and steam supply system for the oil burners at each end of my furnace.

My furnace is of the regenerative type in which the flow ofair through the furnace is reversed periodically in the conventional manner and the two ends of the furnace are therefore symmetrical in all respects, including the arrangement of burners. One end of my furnace is illustrated in Figures 1 and 2. A central furnace chamber it contains the charge to be melted (not shown) and has a hearth l I, a roof if, a port l3 and a downwardly extending knuckle M adjacent the upper portion of the port it. A passage to slopes downwardly and narrows as it approaches the port it and is connected to an iair uptake it from a checker chamber (not shown). The air uptake it is also connected to a stack (not shown) in order to exhaust products of combustion when the regenerative cycle is reversed. Water-jacketed gas burners Ill and it are set into the side walls l9 and 20 of the passage l5 and are connected to gas supply lines Ma and Mia controlled by valves ill) and itb, respectively. A bafile ti extends above the level (if the gas burners ill and i8 where the passage iii connects with the air uptake it. The construction so far described is conventional in regenerative open hearth furnaces designed to be heated by natural or coke oven gas.

My furnace also has oil burners 22 and 23 positioned within the passage l5 below the level of the knuckle M. As shown in Figure 2, these oil burners are positioned adjacent and on the approximate level of the gas burners ii and i8 respectively, between the gas burners l1 and i0 and the port l3. The construction of the oil burners is substantially the same in each case, the burner .23 being illustrated in detail in Figures 3-5. A cylindrical water jacket 24 having an outer wall 25 and an inner wall 26 surrounds and is spaced from a pipe 21 through which a mixture of oil and high-pressure steam is fed into the burner. The pipe 21 terminates in a nozzle 28 arranged to project the mixture of oil and steam in a conical stream out of the burner through an opening 29 in the water jacket 24. The water jacket 24 has a water inlet 30, a water outlet 3| and a dividing wall 3Ia to form passages through which water is circulated to cool the oil burner. The pipe 2! is connected through intermediate connections 32 to an oil supply line 33 and a steam supply line 34I The oil burners 22 and 23 are slidably mounted in the side walls I9 and 20 of the burners and are withdrawn through the said side walls when the furnace is to be heated with gas instead of oil. The intermediate connections 32 are disconnected when the oil burners 22 and 23 are withdrawn. As shown in Figure 3, the burner 23 has a flange 35 around its outer end which projects outside of the furnace. The flange is bolted to the furnace when the oil burners are in operation and its bolt holes 36 are elongated so that the burner may be rotated to adjust the angle of fire of its nozzle within the furnace.

The supply line system for the oil burners of my furnace is illustrated diagrammatically in Figure 6. The burner 23 described above has a valve 31 controlling its fuel oil supply line 33 and a valve 38 controlling its steam supply line 34. The burner 22 similarly has a fuel oil supply line 39 controlled by a valve 40 and a steam supply line 4i controlled by a valve 42. Oil burners of similar construction are similarly positioned at the opposite end of the furnace and these burners, designated 43 and 44 are respectively connected to fuel oil supply lines 45 and 46 controlled by valves 41 and 48 and to steam supply lines 49 and controlled by valves 5| and 52. The fuel lines 33, 39, 45 and 46 are all connected to a main fuel oil supply line 53 with an intermediate valve 54 controlling the lines 33 and 39 and an intermediate valve 55 controlling the lines 45 and 46 in order to facilitate reversing the furnace at the end of each regenerative cycle. The steam lines 34, 4|, 49 and 50 are similarly connected to a central line 56 supplied with high pressure steam to atomize the fuel oil (compressed air may be substituted for steam). A valve 51 and by- pass valves 58 and 59 control the flow of steam to the lines 34 and 4| and corresponding valves 60, 6i and 62 control the flow of steam to the lines 49 and '50 in order to facilitate reversing the furnace at the end of each regenerative cycle. The above mentioned valves in the fuel oil and steam supply lines may also be controlled to turn off the supply of fuel oil and steam when the gas burners are turned on to heat the furnace. The gas burner supply lines are likewise controlled by valves (see valves I 'lb and I8!) in Figure 2) in order to reverse the furnace for regenerative purposes and in order to turn off the gas burners when the oil burners are turned on and vice versa.

During operation of the furnace the gas burners are employed when gas is available to heat the furnace and during this period the oil burners are disconnected from their supply lines and are pu led back out of the air passages at each end of the furnace. However, when it is desired to heat the burners with fuel oil alone, the oil burners are inserted into the air passages as illustrated in Figure 2, the fuel oil and steam supply lines are connected to the oil burners, the control valves are adjusted to supply fuel oil to the burners and steam to atomize the fuel oil. and the oil burners are adjusted laterally as shown in Figure 2 and are rotated about their axes as shown in Figure 1 until the cones of fire are properly adjusted to heat the charge in the furnace and to avoid injury to the furnace lining. The cones of atomized fuel oil should be so directed that they do not play against the walls of the.,surrounding passage nor against the edges of the port or of the roof knuckle at the end of the passage. It is also of importance that the separate identity of the flames from the several burners be maintained at least until they are beneath the adjacent roof knuckle.

When we is again available to fire the furnace the gas burners are again turned on and the fuel oil burners are disconnected and pulled back out of the air passages at each end of the furnace. It is thus apparent that my system of burners provides two heating systems in the same furnace which can be used optionally to heat the furnace with gas alone or oil alone and can be alternated while keeping the furnace in continuous operation.

In the drawings, I have shown a furnace with two oil burners at each end. In some cases it may be desirable to use three or more burners but in any case the separate identity of the separate flames should be maintained at least until the names are beneath the adjacent roof knuckle.

A great advantage of my invention lies in the fact that suitable temperatures for melting down and refining can be maintained in the working chamber of the furnace and that highly satisfactory operating conditions are obtained with oil fuel despite the fact that the chamber is shaped for gas firing. A notable ,consequence of the use of my invention is that the life of the brickwork is not diminished as has been the case heretofore when it was attempted to use straight oil in a furnace of gas-fired design. I desire particularly to point out that contrary to what might be expected, the preservation of the brickwork at either end of the furnace results from the observation at the other end of the furnace of the principles herein disclosed. In other words, the impairment of the brickwork if these principles are not observed will be found to take place at the exit end of the furnace.

Although I have illustrated and described a preferred embodiment of the invention, it will be recognized that changes in the arrangements and details may be made without departing from the spirit of the invention or the scope of the v appended claims.

I claim:

1. An open hearth regenerative furnace of gas-fired design comprising a central melting chamber with a roof, a down-sloped and progressively narrowing air passage leading into each end of the melting chamber and terminating in a port spaced substantially below theprincipal level of the roof, well-defined roof knuckles over each of said ports and controlled means for supplying gaseous fuel to each passage for normal gas-fired operation, in combination with an oil combustion system for use when gaseous fuel is unavailable comprising at least we burners for each end of the furnace, controlled means for supplying fuel oil and a compressed gaseous medium to each burner, each burner having a nozzle for releasing a conical stream of oil atomized in said gaseous medium and the several nozzles at each end of the furnace being positioned within the respective air passages and directed toward the central melting chamber, the nozzles in each passage being oppositely spaced from each other, from the interior surfaces of the passage, and from the port at the end of the passage so that their cones of atomized fuel will merge only after passing beneath the knuckle into the central melting chamber.

2. An open hearth regenerative furnace of gas-fired design comprising a central melting chamber with a roof, a down-sloped and progressively narrowing air passage leading into each end of the melting chamber and terminating in a port spaced substantially below the principal level of the roof, well-defined roof knuckles over each of said ports and controlled means for supplying gaseous fuel to each passage for normal gas-fired operation, in combination with an oil combustion system for use when gaseous fuel is unavailable comprising at least two burners for each end of the furnace, controlled means for supplying fuel oil and a compressed gaseous medium to each burner, each burner having a nozzle for releasing a conical stream of oil atomized in said gaseous medium and the several nozzles at each end of the furnace being positioned within the respective air passages and directed axially parallel to each other toward the central melting chamber, the nozzles in each passage being oppositely spaced from each other, from the interior surfaces of the passage, and from the port at the end of the passage so that their cones of atomized fuel will merge only after passing beneath the knuckle into the central melting chamber.

3. An open hearth regenerative furnace of gas-fired design comprising a central melting chamber with a roof, a down-sloped and progressively narrowing air passage leading into each end of the melting chamber and terminating in a port spaced substantially below the principal level of the roof, well-defined roof knuckles over each of said ports, a pair of gas burners directed toward each other from opposite sides of each passage, and controlled means for supplying gaseous fuel to said gas burners for normal gas-fired operation, in combination with an oil combustion system for use when gaseous fuel is unavailable comprising at least two oil burners for each end of the furnace, controlled means for supplying fuel oil and a compressed gaseous medium to each oil burner, each oil burner having a nozzle for releasing a conical stream of oil atomized in said gaseous medium and the several nozzles at each end of the furnace being positioned within the respective air passages and directed axially parallel to each other toward the central melting chamber, the nozzles in each passage being positioned below the level of the roof knuckles and at the level of the adjacent gas burners and being positioned between the adjacent gas burners and the adjacent port, and said nozzles in each passage being oppositely spaced from each other, from the interior surfaces of the adjacent passage, and from the port at the end of the passage so that their cones of atomized fuel will merge only after passing beneath the knuckle into the central melting chamber.

FREDERICK S. BLOOM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,506,840 Kernohan et a1. Sept. 2, 1924 1,564,049 Davies Dec. 1, 1925 1,964,774 Smoot July 3, 1934

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