US1909048A - Open-hearth furnace - Google Patents

Description

May 16, 1933. N F EGLER 1,909,048

OPEN HEARTH FURNACE Filed July 3, 1931 2 Sheets-Sheet l Patented May 16, 1933V NICHOLAS IKEGLER, OF MONESSEN, PENNSYLVANIA OPEN-HEARTn FURNACE Application filed July 3, 1931. Serial No. 548,540.

This invention relates to open-hearth metallurgical furnaces. In the operation of open-hearth furnaces, fuel and air are admitted to the furnace chamber through a port arranged at one end of the chamber, and the gaseous products of combustion find escapek through a port at the opposite end of the chamber. f From time to time thedirection of "flow is reversed, and the port which had been serving as the intake port, that is, the combustion-producin g port, becomes the port for the outflow of products of combustion, while the port which had been the outflow port be- 1 comesthe intake. Such structures as these 5 are known as .reversing furnaces, and in such furnaces the fuel employed is frequently natural gas, or coke-oven gas, or the gas drawn from ore-reducing blast furnaces. Where gas comprises the fuel of the furnace, it is the practice to introduce the gas (ordinarily in preheated condition) in continuous stream through an uptake to the furnace port; preheated air for the support of combustion is also introduced incontinuous i 2 stream into the port, and, as these streams meet land mingle, a combustible mixture is formed to burn within the furnace chamber. In certain types of furnaces, the stream of gas, upon leaving. the uptake, enters the port through which it advances to the furnace chamber, and the stream of combustion-supporting air is directed angularly into the `stream of gas as it advances through the port. A furnace of this character is known asia blow-torch furnace, and it has been found 1n general that such a furnace gives more perfect combustion, greater heat, and better tonnage than furnaces of other port structure. kHowever, the relatively highv temperatures generatedin the blow-torch furnace tend to destroy more rapidly the ports and walls of the furnace, and this tendency more or less e y completely offsets the good effects indicated.

The volume of outgoing products of combustion is much greater than that of the incoming fuel and air; this is due both to the chemical changes involved in combustion and tothe elevation of temperature incident to combustion. Because of this condition, it has long been a problem, how to fashion and ar- `range furnace ports to achieve. in largest `measure economy of fuel, efliclency of operation, anddurability of structure. Particu-` larly has this been a problem in open-hearth furnaces of the blow-torch type. .This in- 55 vention consists in a portstructure designed tovachieve the above-mentioned good results Without impairin g the durability of theffurnace. Inv the accompanying drawings F ig.` I is'o a fragmentary view in medial, vertical, longitudinal section, showing the rport at one end of the furnace and a portion'of the furnace chamber. In the port here shown the invention is embodied. Fig. II is a view in 65 transverse vertical section, on the plane II-II of Fig. I. Fig. III is a view in horizontal section on the plane III-III,`4 Fig. II. And Fig. IV is a View to larger scale, partly in vertical and longitudinal section :470 andpartly in side elevation and, when compared with Fig. I, showing a certain movable part in its alternate position of service within the port.

In the furnace kshown in the drawings the 575,

walls of the furnace chamber are indicated at l, the hearth at 2, and the roof at 3. Ports 4, arrangedat opposite ends of the furnace, opento the furnace chamber. Into the port .4 a tubular body extends in the direction of the length of the furnace. This tubular body is commonly called a burner, and as a matter of convenience it will in the following specification be so named. Through the burner 5 and into the furnace chamber a P85 stream of gas and air is projected.

In structure the burner 5 advantageously comprises a doublefwalled; body 6 of metal; conveniently it is semicircular inv cross section, cf.. Fig. II, and isV provided with a fiati"o base 7 rInthe base 7 two orifices 8 andA 9 are formed,r leaving three web portions 10, 1l, and l2. The manner in which these web lportions serve as closures or vvalves will presently be described; suffice itnow to say 95 that the hollow chamber within the doublewalled body G is continuous throughout these webs and that the -Whole hollow body is thus adapted to be cooled by thel circulation of water. Conveniently, cooling water is introduced to the hollow body 6 through two inlet pipes 13 (cf. Figs. I and III), and pipes 13 are continued in extensions 14, to insure distribution of water in the base 7. An outlet 15 (Figs. I and IV) serves as an escape for the circulating cooling water. The rear end of the hollow body G is closed, as by means of a refractory wall 16, and, upon the basal web 11, a wall 17 of refractory material is erected, extending transversely of the hollow body. The mouth 18 of the body 6 is open. rlhe interior of the body 6, forwardly of the wall 17, is provided with a lining 19 of refractory material, and eXteriorly the upper and arched surface of the body 6 is protected by a covering 24 of refractory material. The lining within the body 6 at its forward end includes a fire-brick covering 20 upon web 12. An orifice 21 extends through the transverse wall 17 longitudinally of the structure as a whole.

The tubular burner 5 rests upon the floor of the port and is movable in its position in the furnace port and in the direction of its length, between the alternative positions shown in Figs. I and IV. The position shown in Fig. I is that occupied at the intake end of the furnace; the position shown in IV is that occupied at the ontgo end.

Extending vertically through the floor of the port, advantageously in the vertical midplane of the port, is passageway 22 which at the intake end of the furnace serves as the uptake, for the introduction of gaseous fuel. Forwardly of the fuel uptake 22, that is, in a` region of the furnace structure nearer to the furnace chamber, a passageway 23 opens to the port, and this passageway 28 serves at the intake end of the furnace as the air uptake. It will be noted (Fig. II) that the width of the passageway 23 approximates that of the port. Through this passageway 23 at the intake end of the furnace and through the opening 9 streams of combustion-supporting air, preheated in the usual manner in regenerator chambers (not shown), enter the burner, forwardly of the wall 17 (cf. Fig. I). The gaseous fuel, also preheated in the usual manner, rises through passageway 22 and through opening 8 and enters the burner to the rear of wall 17. From the space to the rear of the wall 17 the stream of gas advances through the oriice 21 to the space forwardly of such Wall 17, to which last mentioned space the air also has access as has been indicated. rI`he air, in streaming upward through opening 9, is directed angularly upon the stream of gas as it advances to the furnace chamber; and consequently, the mixing of the fuel and the air begins within the mouth 18 of the burner, and a combustible mixture advances to the furnace chamber.

The flame springs from the port at one end of the furnace, and streams through the furnace chamber. The products of combustion pass through the port at the opposite end of the furnace chamber. Periodically, by operation of valves (not shown), the direction of fiow through the furnace is reversed, and at the same time the burners 5 at the two ends of the furnace are shifted the port which h a d been serving as intake port becomes the outgo port, and the port which had been serving for the escapeV of products of combustion becomes the intake port. Such reversal is in* cident to the use of the regenerator. Regenerators are provided at or in association with each furnace port; the outgoing hot gases sweep through the regenerators and heat to a high temperature the checkerwork within them, and the clleckerwork absorbs large stores of heat. Vhen the furnace is rcversed, the air on its way to the port (now the intake port) passes through one of the pre viously heated regenerators and takes up heat which has been so stored in its checkerwork. Similarly, gaseous fuel is introduced to uptake 22 by way of the other of the regen erators in which heat has been stored. By periodic reversal, quantities of heat are at intervals stored alternately in the regenerators for each port, and the stored quantities of heat are taken up by the incoming gaseous fuel and air, rendering both components of the gaseous mixture more effective in the apidity and efficiency of combustion within the furnace chamber. In a typical open-hearth furnace the same passageways and port which at one end of the furnace admit the components of the combustiblev mixture serve at the opposite end as the way of escape for the roducts of combustion; and, as has been said, since the products of combustion are of vastly greater volume than the entering components of the combustible mixture, the designing of an efficient port is an engineering problem of importance. The problem Ais rendered much more difficult by the fact (particularly in a furnace of blow-torch type) that the hutgoing products of combustion are exceedingly hot and in a condition to act the more deleteriously upon confining walls.

Turning to the drawings, it will be perceived that, whereas at the intake end of the furnace (Fig. I) the burner 5 overlies the passageway 23, so that access of air is through the burner, at the outgo end (Fig. IV), the burner being withilrawn, the products of cont bustion have immediate access to passageway 23 and that so much of the stream as escapes through passageway 23 does not flew through the burner at all. It will further be perceived that the orifices 8 and 9 formed in the floor of the burner are so proportioned that, whereas at the intake end (Fig. I) the air rising through passageway 23 has access to the burner (and to the stream of gas advancing throlfigh the burner) through a restricted orifice formed by the smaller opening 9 (and combustion. And, in addition to that,

whereas at the intake end the passageway 22` fiares to a wide delivery for the gas through the larger opening 8 into burner 5, at the outgo end the passageway 22 is, by the registration with it of the smaller opening 9, throttled, so as'to reduce to still lower value that portion of the stream of products of combustion which finds escape through passageway 22.

It is characteristic, then, of my structure that at the intake end of ther furnace the effective opening of the uptake 22 (that is the fuel uptake) is maximum, and the effective area of the air passage, or passages, is constricted, and a stream of air of proper volulne enters with accelerated velocity. At the outgo end of the furnace the air passage 23 is uncovered, and is of maximum effective area for the reception of products of combustion. At the same time the opening 9, overlying the passageway 22 is effective to retard escape of combustion products, and to cause a still greater fraction of the whole to pass out at 23 and less at 22. The arrows in Fig. IV, in-k dicate the course ofthe products of combustion. The major portion of the products of combustion are short-circuited through the air passage 23, and correspondingly the burner is relieved of the sweeping through of the hot products of combustion. That is to say, the structure is suoli that the products of combustion will flow in streamlines, or substantially so, into the passage 23, and, consequently, their destructive action on the walls of the port and of the burner is minimized. At the same time, through opening 9 and passageway 22, a sufficient fraction of the waste gas stream passes to heat effectively the checkerwork in the fuel regenerator.

It is characteristic of my structure that the .ingress of air to the port is at a point nearer to the furnace chamber, and that the ingress of gas is at a point more remote from the furnace chamber. Advantageously, the air port extends as nearly as may be to the full width of the port, to the end that, when the furnace is reversed, an outlet opening of large area is accessible to the products of combustion. Accordingly, the hot products of combustion pass quickly from the furnace.

I claim as my invention:

1. In an open-hearth metallurgical furnace of `reversing type, the combination of a furnace chamber and a port,a gas passageway opening in the floor of the port at a point more remote and an air passageway opening through the floor of the port at a point less remote from the furnace chamber, and a'burner movable over the fioor of the 'port between alternate positions of service,

which burner includes in its floor two orifices,

'one registering with said air passageway and one' registering with said gas passageway when the burner is in one of its alternate positions of service, a transverse, orificed wall within said burner and intermediate said orifices, whereby, when the burner is in said position of service, gas 'enters the burner on 011e side of said wall, and, upon passing through theorifice in said transverse wall-is `presented to air streaming into the burner on the other side of said wall, and in the otherof its alternate positions of service said burner being adapted to uncover said air passageway and, by means of a Hoor orifice, to consti-ict said gas passageway.

2. In an open-hearth metallurgical furnace of reversing type, the combination with a furnace chamber of a port, a passageway for gas opening through the floor of said port, a passageway for air opening through the floor of said port, a burner movable over the floor of the port, said burner being provided with an orificed floor, the openings in the floor of the burner being so shaped and proportioned that in one operative position of the burner the gas passageway is uncovered by the floor of the burner and the air passage` way is constricted, and, in another position, the air passageway is uncovered and the gas passageway is constricted, the said burner being further provided with an orificed, transversely extending wall, such wall being so disposed as to lie between the gas passageway and the air passageway, when the burner is in the first of the two positions de (ined.

3. In an open-hearth furnace, the combination of a port including a gas passageway and an air passageway opening into the port, a burner movable between alternate positions in said port, said burner including an orificed partition, the wall of said burner including an orifice on each side of said partition, said wall orifices in one position of the burner lying respectively in communication with said gas and air passageways, whereby the partition orice constricts thel passage of gas and one of said wall orifices constricts the air passageway,A and, in the alternate position of the burner, saidV air passageway being uncovered, and the wall 'y said partition,`and said burner Structurebeing movable between alternate posltions with respect to said fuel and air passageways, Whereby the position of said oriced partition is acljustable relatively to said passageways, and the inlets in said burner Wall, the burner Wall regions adjacent Said inlets, and said oriieecl partition co-operate n regulating gaseous flow in Said passageways.

In testimony whereof I have hereunto set NICHOLAS F. EGLER.

`my hand.

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