US2534454A - Method of operating open-hearth furnaces - Google Patents

Description

Dec. 19, 1950 c. M. KAY ErAL METHOD 0F OPERATING OPEN-HEARTH FURNACES Filed Dec. s, 1947 Q//l LA Patented Dec. 19, 1950 METHOD F OPERATING OPEN -HEARTH FURNACES Charles M. Kay, Worcester, Mass., and John C. Witherspoon, Monongaliela, Pa., assignors to The American Steel and Wire Company of New Jersey. a corporation of New Jersey Application VDecember 3, 1947, Serial No. 7 89,508

` 3 Claims. l 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 hot metal is added and the entire charge refined. Various types of fuel, such as gas, oil 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.'

In some instances where gaseous fuels are used, two burners may be used at each end of the furnace, but these are commonly low pressure burners firing at an angle to the center line of the furnace. The amount of heat required varies at different stages of the heat. The desired characteristics of the flame are also different at various stages of the heat. When using a single liquid fuel burner it is difficult to obtain the desired amount of heat at all times and it is also diillcult to change the flame characteristic. During the melting down period a sharp, short intense flame is preferable while during the refining period a long luminous flame is preferred. In using a single burner the volume of fuel is such that the combustion is somewhat delayed because the fuel and air do not mix readily, and as a result, the melting down of the scrap charge is delayed because the maximum flame temperature is not obtained with the desired speed.

It is an object of this invention to provide a method of firing an open hearth furnace in which two streams of liquid fuel are introduced into the furnace one above the other, thus enabling a greater volume of fuel to be supplied than with a single burner and at the same time enabling quicker mixing of the air and fuel to increase the speed of combustion of the fuel.

Another object of the invention is to provide a sharp llame for heating the charge during the melting period.

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

Figure l is a horizontal sectional view taken at the burner ports;

2 Figure 2 is 9, sectional view taken on the line lI-II of Figure l; and

Figure 3 is a sectional view taken on the line III- III of Figure 2.

Referring more particularly to the drawings, the reference numeral 2 indicates the hearth of an open hearth furnace. The ends of the furnace are thesame and therefore onlyV one end is shown in the drawings and will be described herein. A

pair of burner tunnels 4 are provided through the end wall 5` and two liquid fuel burners of conventional design are located therein. The lower burner 6 is arranged approximately on the center line of the furnace with its axis arranged at an angle to intersect the surface of the charge. Directly above the burner 6 is the burner 8 which is arranged at a steeper angle than burner 6 so that its extended axis will intersect the extended axis of burner 6 at a point beyond the intersection of the axis of burner 6 with the surface of the charge. While the above arrangement is a preferred arrangement, it is also within the scope of our invention to position the burners within a range extending from that relative angular relationship in which the extended axes of the burners intersect at substantially the same point on thecharge to the position where the said' extended axes of the burners are parallel. As is usual, the liquid fuel is atomized with steam or compressed air and the flow of the mixture of steam and fuel to burners 6 and 8 is regulated by means of valves IIJ and I2, respectively. Air for combustion is supplied from a checker chamber I4 through the air uptakes I6 and flows into the melting chamber I8 of the furnace around the streams of fuel from burners 6 and 8. The mixing of the fuel and air Is accelerated as it passes through the restricted passageway or throat 20. The furnace is provided with the usual back wall 22 and front wall 2l having door openings 26, 28 and 38 therein. The opening 30- is on the center line of the furnace and two openings similar to openings 26 and 28 are located on the opposite side of the center line.

The furnace is operated in the following. manner:

Metal scrap is charged into the furnace and `burners 6 and 8 are set in operation with air flowing upwardly from the checkers I4 through the uptakes I6 around the streams of fuel flowing from the burners. The streams of fuel from the burners flow longitudinally into the chamber I8 with the stream from the burner 6 being directed downwardly at an angle to impinge on the charge and the stream from the burner I being directed above the first stream downwardly at an angle to impinge'on the charge at a point beyond the point of impingement of the first stream on the charge. The center lines of'the streams of fuel intersect at a zone between one-third and one-half the length of the furnace (as measured between the burner tips at each end of the furnace) from the burners. In th'e furnaces in which the method is being used this zone includes doors 28 and 30 and the space therebetween. Because of the bulkiness of the scrap charge it is advantageous to have the two flames contact the charge at different positions and at different angles. These double burners give a short flame with the heat concentrated in a small area.

In the furnaces in which the invention is being used we have found that it is advantageous to provide from 30% to 75% of the fuelthrough the top burner and the remaining fuel through the lower burner. As compared to the single burner previously used, about 25% more fuel can be used efliciently with the double burners. On

single burners about 3.05 pounds of steam are n consumed per gallon of oil fired whereas the total steam consumption is about 3.5 pounds per gallon of oil fired when two burners are used, this being approximately a increase per gallon of oil. Due to the increase in fuel consumption, approximately 1290 pounds of steam are consumed per hour with double burners as compared to 920 pounds on a single burner, this being an increase of approximately 40%. While the data givenrepresents one particular practice used it will be understood that the invention is not limited to such practice but is also applicable to a practice in which up to 75% of the total fuel may be fed from the top burner and up to 6.0 pounds of steam may be consumed per gallon of oil fired. During the refining period, the top burner 8 is shut off and only the lower burner 6 is used. This is necessary because the large amount of heat liberated through the use of the two burners and increased fuel will overheat the roof and walls if there is an insufficient amount of cold charge available to absorb the heat input.

It will be understood that the furnace will otherwise be operated in the manner normal to such furnaces, that is, it will be reversed at intervals and on each reversal the burners and be made without departing from the scope of the following claims.

We claim:

1. In the method of making steel in the melting chamber of an open hearth furnace which includes the step of charging metal scrap into the furnace, the improvement in the melting step thereof comprising projecting a pair of streams of liquid fuel from a pair of burners into one end of and longitudinally of said chamber, one stream of said fuel being directed downwardly at an angle to impinge on said charge, the other stream of said fuel being directly above and in the same vertical plane as the rst stream and being directed downwardly at an angle to impinge on said charge at a point beyond the point of impingement of the rst stream on the charge,

the center lines of the streams of fuel intersectins at a zone between one-third and one-half the length of the furnace from theburners, and flowing into said chamber a stream of air around said streams of fuel.

2. In the method of making steel in the meltlng chamber of an open hearth furnace which includes the step of charging metal scrap into the furnace, the improvement in the melting step thereof comprising projecting a pair of streams of liquid fuel from a pair of burners into one end of and longitudinally of said chamber, one stream of said fuel being directed downwardly at an angle to impinge on said charge, the other stream of said fuel being' directly above and in the same vertical plane as the rst stream and being directed downwardly at an angie to impinge on said charge at a point beyond the point of impingement of the rst stream on the charge, supplying from 30% to 75% of the fuel through the top burner and the remainder through the bottom burner, and flowing into said chamber a stream of air around said streams of fuel.

3. In the method-of making steel in the melting chamber of'an open hearth furnace which includes the step of charging metal scrap into the furnace, the improvement in the melting step thereof comprising projecting a pair of streams of liquid fuel from a pair of burners into one end of and longitudinally of said chamber, one stream of said fuel beingy directed downwardly at an angle to impinge on said charge, the other stream of said fuel being directly above and in the same vertical plane as the first stream and being directed downwardly at an angle to impinge on said charge at a point beyond the point of impingement of the rst stream on the charge, supplying from 30% to 75% of the fuel through the top burner and the remainder through the bottom burner, the center lines of the streams of fuel intersecting at a zone between one-third and one-half the length of the furnace from the burners, and flowing into said chamber a stream of air around said streams of fuel.

CHARLES M. KAY. JOHN C. WI'IHERSPCON.

REFERENCES CITED The followingreferences are of record *In the file of this patent:

I UNITED STATES PATENTS Number Name Date 1,554,251 Schieldrop Sept. 22, 1925 1,907,140 Bartholomew May 2, 1933 1,955,589 Leahy Apr. 17, 1934 2,011,554 Luetscher Aug. 13, 1935 2,018,179 Kuhner Oct. 22, 1935 2,025,165 Henry Dec. 24, 1935 2,069,196 Conway Feb. 2, 1937 2,137,185 Seil Nov. 15, 1938 2,140,785 Cone Dec. 20, 1938 2,233,916 Creighton Mar. 4, 1941 2,310,454 Mulholland Feb. 9, 1943 2,417,951 Schwartz Mar. 25, 1947 OTHER REFERENCES 1944 Open Hearth Proceedings, pages 126, 127, I1q29 published by the A. I. M. E. (New York,

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