US1798611A - Open-hearth furnace - Google Patents

Description

March 31, 1931. LEVENTRY 1,798,611

OPEN HEARTH FURNACE Filed April 8, 1921 5 Sheets-Sheet l Wm Pay A. Lewen/ry v March l931- R. L. LEVENTRY 1,798,611

OPEN HEARTH FURNACE Filed April 8, 1921 5 Sheets-Sheet 2 L. Levedfo March 9 R. L. LEVENTRY 1,798,611

OPEN HEARTH FURNACE Filed April 8, 1921 3 Sheets-Sheet 5 INVENTOR.

ATTORNEYS.

Patented Mar. 31, 1931 ROY L. LEVENTRY, OFYOUNGSTOWN, OHTO OPEN-HEARTH FURNACE I 5 Application filed April 8, 1921. Serial No. 459,613.

The modern open hearth steel furnace is a rectangular box-like structure, enclosing a shallow hearth upon which the material entering into the manufacture of steel is melted 5 and refined. The heat necessary to the operation is supplied by a flame playing over the hearth. The flame isusually produced by the combustion of gaseous fuel, which, together with the air necessary to support combustion,

is supplied through large ducts located at either end of the furnace. If the fuel employed is producer gas, both air and gas are preheated, while if coke oven gas or natural gas is used, the air only is preheated: The great majority of modern furnacesare fired with producer gas. In this type three vertical ducts are constructed in the brickwork at each end of the furnace. The central duct discharges into a horizontal nozzle known as the gas port, through which the heated gas is forced into the furnace. The two outer ducts are known as the air uptakes since they discharge preheated air into the upper portion'of the furnace. The air and the gas meet at the nose of the gas port and produce a flame which passes across the furnace, the products of combustion being drawn out through the openings in the opposite end. These openings are identical insize and shape to the openings through which the air and gas entered. After a suitable period of time the process is reversed. The air and gas then enter the furnace through the openings by which the products of pombustion previously were removed, the flame traverses the hearth in the opposite direction, and the products are carried off through the openings by which the air and gas previously entered.

Under the method of construction and operation described above difliculty is experienced in obtaining complete combustion of the gas in the furnace chamber since an intimate mixture of gas and air is not'pbtained. As a result the furnace must be flooded with an excess of. air to insure complete combustion, in many cases amounting to over 100 per cent of the amountrequired for perfect combustion. The results of this practice are a lower flame temperature and a consequent decrease in steel production. It is, moreover,

difiicult to prevent the presence of injurious oxides in the finished product when this excess of air is used. .It is evident, then, that if a more intimate mixture of gas and air could be secured, less excess air would be required, and higher quality steel in greater quantities would be produced.

To accomplish this, various devices have been proposed, consisting of gates or dampers placed in the various uptakes to be used with fans or blowers for forcing the correct amount of air into intimate contact with the gas, and thus obtaining a short hot flame with minimum excess of air. All of these installations however must be made at great expense and involve extensive alterations to the furnace structure. There is a pressing need of a cheap method of eliminating the defect described, a method which will involve a small change only to existing equipment.

To fill this need the apparatus constituting the present invention, has been developed. One object of the invention in other words is to provide an arrangement for effecting an intimate mixture of air and producer gas in an open hearth furnace to produce a hotter flame than has heretofore been obtained, without the use of air in excess of that absolutely required to complete the combustion of the gas. A second .object is to provide means for the' combustion of coke oven gas in an open hearth furnace. On account of the low specific gravity of this gas it-must be thoroughly mlxed with the air of com bustion before entering the furnace proper, otherwise, it will rise, due to extreme lightness, and'the flame will have an injurious ef-' feet on the roof.

To the accomplishment of the foregoing 99 and related ends said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims, the annexed drawings and the following description setting forth in detail certain mechanism embodying the invention, such disclosed means constituting however but several of the various mechanical forms in which the principleof the invention may be used. 1 p ,5)

In said annexed drawings Fig. 1 is an end elevation of a furnace em bodying my present improvements; Fig. 2 is a central longitudinal section thereof as indicated by the line 2-2, Fig. 1; Fig. 3 is a horizontal section taken on the plane indicated by the line 3-3, Fig. 1; Fig. 4 is anothervertical section but taken on a plane to the right of the center as indicated by showing a modification of the air passages,

the aspirator being constructed in the brickwork beneath the normal level of the gas port. l

Briefly stated, the invention consists-1n the use of the suction exerted by a jet of fluid 1ssuin from a nozzle under hi h ressure to D b draw heated air directly; into the gas port and there force it into intimate contact with the gas. This air may'be drawn from. any

' convenient place such as from the uptakes at the side or from the checker chambers or slag pockets beneath. The passages through which this air is'conducted may be construct ed of pipe (as shown in the drawing). or of masonry. They may be built on the .outside of the furnace structure as shown in Figs. 1, 2- and 3, or they may bebuilt directly in the brickwork of the furnace itself, as shown in Figs; 6, 7 and 3. The actual amount off 10 of fluid under pressure Wlll be to constiair to be drawn through this aspirator may be varied by changing the size of the passages.

or by varying the pressure 'of the jet. Compressed air, steam or other fluid may be used to form the jet described. As may be seen in the drawings,- when .coke oven gas or its equivalent is to be used, this .gas is brought into the producer gas port from the side and issues from the delivery pipes at a point directly in front of the air delivery duct of the aspirator, so that a thorough mixture is obtained at this point. With the application of coke oven gas to the aspirator principle, the furnace may be operated on either coke oven gas, or producer gas exclusively, or a combination of the two. It. will be seen that the apparatus is very simple and may be installed with a minimum of expense.

- The correct amount of'air for combustion may be supplied without the use ofslides or dampers and the three uptakes are left free for the accommodation of the outgoing gases when the furnace is reversed. The apparatus is easy to adjust and will not get out of order when in operation.

The construction of the furnace proper, illustrated in the several figures of the drawings, has been as previously stated, changed as little as possible from standard design. Thus there is retained the usual gas uptake 1 that discharges through a port 2 into the adjacent end of the furnace chamber 3, while on each side of such gasuptake is an airuptake 4; that communicates freely with the upper portion of the furnace. The foregoing constitutes standard construction for a producer gas furnace. I 1 l In order to adapt the foregoing construction for use with an aspirator two duets 8, 8

are brought from the respective air uptakes,

4, 4 to a junction with a, third duct 7. Connected to this junction in a direction parallel to duct 7 is a smaller duct or pipe 10 through which compressed air, steam or like fluid may be supplied under pressure. Where, as shown in Figs. 1, 2, 3 and 4, duct 7 and itsbranches consist of pipes, an enlarged head 9, shown in detail in Fig. 5, serves to connect their respective outer ends. In Figs. 6, j

7 and 8 the cqnst-ruction is built as an integral part of the furnace, the ducts in question being constructed of masonry with the exception of uct 10 which will be a steel pipe with a fire brick shell. In Fig. 8,'auxi1iary pipes 11, 11 are shown, for the introduction of the compressed fluid into different parts of the apparatus. For the employment of coke oven gas as the heating medium either in whole or in part, two pipes 5, 5 are brought in through the lateral walls of the furnace so as to bring their ends opposite each-other approximately centrally of port 2 and immediately in front of the discharge end of duct 7.

The effect of the admission through'pipe duct 7 so as to combine with gaseous fuel supplied. either through uptake 1 as producer gas, through pipes 5, 5 as coke oven gas or through both as a combination of thetwo. I

have found that a relatively small volume of compressed air thus supplied through pipe 10 and under a moderate pressure will draw suflicient air through ducts 8 to provide a proper combustible mixture without lowering the temperature of the aspirated air sufficiently to impair the efliciency of the apparatus. 3

As an example of satisfactory operating conditions, I have found that compressed air amounting to two per cent only of the total volume required will if supplied through the pipe 10 under a pressure of 30 pounds produce entirely satisfactory results. I The advantages derived from the use of this apparatus are as follows: I

(1) A quick and perfect combustion of the .fuel gas with a resulting flame that is short and hot giving increased production to the furnace; (2) an improvement in the quality of steel made due to the absence of injurious oxides in the metal. These oxides air in the flame; (3) simplicity, ease of operation and low cost of installation ofthe ap paratus. It is easily adapted to any producer gas fired furnace; and the apparatus may be used with any gaseous fuel, although particularly designed for producer and coke oven gas. 1

Other modes of applying the principle of my inventionmay be employed instead of the one explained, change being made; as regards the mechanism herein disclosed, provided 'the means stated by any of the following claims or the equivalent of such stated means be employed. v

' I therefore particularly point'out and dis-' tinctly claim as my invention v 1. In a furnace ofthe character described, the combination of a hearth, a. horizontally extending gas port at the end thereof, a vertical duct connected with the rear end of said port, an air duct on discharging into the furnace, two fuel supply pipes extending into said port from opposite'sides, and an a'spiratorconnected to drawair from said air ducts and discharge the same in said port just to the rear of the outlets of said ful supoutlets of P y p p L a A 2. In" a furnace of the character described, the combination of a hearth, 'a horizontally extending gas port at the end thereof, a ver tical duct connected with the rear end of said discharging into said each side of said port upper portion of the nace, and another fuel supply means discharging into said port, and an aspirator connected to draw,

air from said duct and discharge the same in said port adjacent the outlet of said fuel supply.

5. In a furnace of the the combination of a hearth, a horizontally extending gas port at the end thereof, a vertical duct connected with the rear end of said port,'selectably-usable heating means comprising means for supplying gas to said vertical duct, an air ductfon each side of said port discharging into the upper portion of the furnace, and another fuel supply means port, and an aspirator connected to draw air from said air duct and discharge'the same in said port adjacent the outlet of said fuel supply.

Signed by me, this 4th day of April, 1921.

port,an airduct on each side of said port dlscharging .into the upper portion ofthe furnace, two fuel supply pipes extending intosaid port from opposite sides, an air supply duct extending through the end of the furnace'to a point just tothe rear of the said fuel supply pipes, branches leading from said lastmentione d air duct to I said first-named air ducts respectively, and

7 upper portionof "ply pipes extending just tothe rear of such recess;

- fi'rst-namedair ducts respectively,

' l sure fluid-jet projecting i-nto said last mentioned air-duct. 1

a pressure fluid jet mentioned air-duct.

3. In a furnace of the character described, the combination of a? hearth,"a horizontally extending gas port-at the end thereof, said port being formed with a transverse recess, in its bottom wall, a vertical duct connected with-the rear end of said port, an air duct on each side of said port dlscharging into the the. furnace, two fuel supinto said port-from op-' posite sides, thefinner ends of said pipes lying in such recess, an air su ply duct extendingthrough the end of the mace to a point L branches leadfrom said last-mentioned air duct to said and a pres- 4. In a furnaceof the-character described, the combination of a: hearth, a gas port at the end thereof, selectably-usable heatmg' means' comprising a gas-supply duct. leading to said gas port, an air duct' beside "saidbport disprojecting into said last R. L. LEVENTRY.

character described,

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