US2550848A - Method of operating open-hearth furnaces - Google Patents

Description

y 1951 K. H. MOODY 2,550,848

METHOD OF OPERATING OPEN-HEARTH FURNACES Filed March 16, 1948 2 Sheets-Sheet 2 lawenlar: A f/fi/ M000),

Patented May 1, 1951 METHOD OF OPERATING OPEN-HEARTH FURNACES Keith H. Moody,.Duluth, Minn, assignor to The American Steel & Wire Company of New Jersey, a. corporation of New Jersey Application March 16, 1948, Serial No. 15,233

6 Claims.

This invention relates to a method of operating open hearth furnaces and more particularly to operating such furnaces when they are using scrap metal as part of the charge. In the operation of such furnaces, scrap is first charged into the furnace and melted down, after which cold and/or hot iron are added and the entire charge refined. Various types of fuel,-such as gas, oil

a and tar, are used in heating the furnace. In

some instances a combination of gas and oil or tar is used. This invention relates to those furnaces in which oil or tar are used separately or in combination with gas and for the purpose of this application, any fuel made up in whole or in part of a liquid will be termed liquid fuel. In heating the charge, the heat is supplied alternately from each end of the furnace and ordinarily a single burner is used at each end of the furnace.

Due to normal furnace construction and the relative position of the bridge walls and burners, it has been difficult to provide the air in a manner to obtain combustion of the liquid fuel close to the entrance end of the furnace when using a single burner at top capacity. As a result, a considerable amount of fuel burns near the exit end of the bath or may even burn as it leaves the furnace through the downtakes. We have found that by introducing compressed oxygenfdirectly below the fuel stream the speed of combustion is increased with an accompanying increase in melting rate and fuel efiiciency. It has been suggested that oxygen be introduced around the periphery of the fuel outlet, but'this does not act in a satisfactory manner and tends to burn the roof. When oxygen is supplied in the manner of my invention it has been found that the roof temperature will be lower than normal.

I t It is an object of this invention to provide a method of firing an open hearth furnace in which oxygen is introduced into the furnace directly beneath the fuel stream.

Another object is to provide a burner especially adapted for carrying out my method.

These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

Figure 1 is a plan view, partly in section, of one-half of an open hearth furnace showing my burner in place;

Figure 2 is a longitudinal section of the furnace of Figure 1 taken through the front uptake;

Figure 3 is a longitudinal elevation of the burner of my invention;

Figure 4 is an enlarged longitudinal section of the burner of Figure 3;

Figure 5 is a sectional view taken on the line V-V of Figure 4; and

Figure 6 is a sectional View taken on the line VIVI of Figure 4.

Referring more particularly to the drawings, the reference numeral 2 indicates the hearth of an open hearth furnace. The furnace is substantially symmetrical about its transverse center line and therefore only one-half thereof is shown in the drawings and will be described herein. A burner tunnel t is provided through the end wall 6 and a-liquid fuel burner 8 is arranged approximately on the center line of the furnace with its axis arranged at. an angle to intersect the'surface of the charge.

As shown in Figures 3 to 6, the burner 8 consists of a casing it inside of which near the top thereof is a conventional oil burner l2 made up of three concentric pipes l4, l6 and i8. Steam is supplied through the inner pipe l4 and oil is supplied through the pipe I6 around the pipe M. The oil passes through holes 29 in pipe I 4 at the nozzle 22 where it mixes with the steam in the usual manner. An air space is provided between the pipes l6 and I8. Beneath the oil burner I2 is a longitudinal pipe 24 which contains an oxygen supply pipe 26. The end of the pipe 26 extends beyond the end of the burner a distance of between one and twelve inches, preferably between six and twelve inches. rounds the front part of the pipe 26 and water is supplied thereto through a pipe 39 with the water exhausting therefrom through a pipe 32. Water is supplied to the casing l0 through pipes 34 and exhausts through a pipe 36. The usual valves are provided for regulating the flow of the various fluids.

The burner 8 may be located on the exact center line of the furnace or its axis may be tilted a slight amount toward the front of the furnace as shown. For example, it might be aimed at a point three feet from the longitudinal center line on the opposite end wall of the furnace. The vertical angle of the burner is preferably such that the flame strikes the top of the bath 38-at a point in line with the center line of the first furnace door 40. In addition to the door 68, the front wall 42 is provided with doors 44 and 46, the door 46 being on the center line of the furnace and two doors similar to doors a0 and 44 being located on the opposite side of the center line. The furnace is provided with the usual back wall 48. Air for combustion is supplied from the checker chamber 50 through air uptakes 52 and flows into the melting chamber 54 around the stream of fuel from burner 8. The mixing of the fuel and air is accelerated as it passes through the restricted passageway or throat 56.

The furnace is operated as follows:

-Metal scrap is charged into the furnace, the burner I2 is started in operation and oxygen is introduced through the pipe 26. The air from the checker chamber 50 flows upwardly through the uptake 52 around the streams of fuel flow- A pipe 28 suring from the burner. The velocity of the oxygen stream is preferably approximately the same as the velocity or" the flame but may vary from onesixth to two times the velocity of the flame, this being sufficient to enable the oxygen to penetrate the cone of the fuel stream flame at a point approximately 2 feet from the end of the fuel jet. By supplying oxygen in this manner the greatest amount of heat is directed downwardly on the charge where it is most useful. The oxygen is preferably turned off at the end of the melt-down period or at least a short time after the lime boil, but ma if desired be used to raise the temperature of the molten bath after additions have been introduced while working the heat. It will be understood that the furnace will otherwise be operated in the usual manner. That is, it will be reversed at intervals and on each reversal, the burner and oxygen will be shut off at one end and the burner and oxygen at the other end will be turned on.

While one embodiment of my invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing, from the scope of" the following claims.

I claim:

1. In the method of making steel in the melting chamber of an open hearth furnace which includes the steps of charging metal scrap into the furnace, the improvement in the melting step thereof comprising projecting a stream of liquid fuel from a burner into one end of and longitudinally of said chamber, said stream being directed downwardly at an angle to impinge on said charge, flowing into said chamber a stream of preheated air around said stream of fuel, and introducing a stream of oxygen into said chamber only directly below and in the same longitudinal vertical plane as the fuel, said stream of oxygen entering said chamber ata point between one and twelve inches from the furnace end of the burner.

2. The method of making steel in the melting chamber of an open hearth furnace according to claim 1 in which the velocity of the oxygen at the point of introduction is approximately the same as the velocity of the fuel.

3. The method of making steel in the melting chamber of an open hearth furnace according to claim 1 in which the oxygen is shut off after the scrap is well melted down.

4. The method of making steel in the melting chamber of an open hearth furnace according to claim 2 in which the oxygen is shut off after the scrap is well melted down.

5. In the method of making steel in the melting chamber of an open hearth furnace which includes the steps of introducing a metal charge into the furnace, the improvement in the melting step thereof comprising projecting a stream of liquid fuel from a burner into one end of and longitudinally of said chamber, said stream being directed downwardly at an angle to impinge on said charge, flowing into said chamber a s.rean1 of preheated air around said stream of fuel, and introducing a stream of oxygen into said chamber only directly below and in the same longitudinal Vertical plane as the fuel, said stream of oxygen entering said chamber at a point between one and twelve inches from the furnace end of the burner.

6. The method of melting metal in the melting chamber of an open hearth furnace which includes the steps of charging metal scrap into the furnace, projecting a stream of liquid fuel from a burner into one end of and longitudinally of said chamber, said stream being directed downwardly at an angle to impinge on said charge, flowing into said chamber a stream of preheated air around said stream of fuel, and introducing a stream of oxygen into said chamber only directly below and in substantially the same longitudinal vertica1 plane as the fuel, said stream of oxygen entering said chamber at a point between one and twelve inches from the furnace end of the burner.

KEITH H. MOODY.

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

UNITED STATES PATENTS Number Name Date 1,659,869 Gow Feb. 21, 1928 1,712,326 Brock May 7, 1929 1,718,732 Danforth, Jr June 25, 1929 1,830,574 Thwing Nov. 3, 1931 1,917,031 Hamilton July 4, 1933 1,955,589 Leahy Apr. 17, 1934 2,243,987 Stokes June 3, 1941 2,362,085 Morgan Nov. 7, 1944 2,417,951 Schwartz Mar. 25, 1947 2,446,511 Kerry et a1 Aug. 3, 1948 OTHER REFERENCES A. I. M. E. Open Hearth Proceedings, pages 68, 69, 73, 74, 76, and 82. Published in 1947 by the A. I. M. E., New York, N. Y.

The Foundry, October 1947, pages 74, and 76. Published by th Penton Publishing Co., Cleveland, Ohio.

Claims (1)

1. IN THE METHOD OF MAKING STEEL IN THE MELTING CHAMBER OF AN OPEN HEARTH FURNACE WHICH INCLUDES THE STEPS OF CHARGING METAL SCRAP INTO THE FURNACE, THE IMPROVEMENT IN THE MELTING STEP THEREOF COMPRISING PROJECTING A STREAM OF LIQUID FUEL FROM A BURNER INTO ONE END OF AND LONGITUDINALLY OF SAID CHAMBER, SAID STREAM BEING DIRECTED DOWNWARDLY AT AN ANGLE TO IMPINGE ON SAID CHARGE, FLOWING INTO SAID CHAMBER A STREAM OF PREHEATED AIR AROUND SAID STREAM OF FUEL, AND INTRODUCING A STREAM OF OXYGEN INTO SAID CHAMBER ONLY DIRECTLY BELOW AND IN THE SAME LONGITU-

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