US2027151A - Apparatus for making open-hearth steel - Google Patents

Description

Jan. 7, 1936. M. J. CONWAY APPARATUS FOR MAKING OPEN HEARTH STEEL Filed June 20, 1934 5 Sheets-Sheet l 4. L-i F: 6- -E i i l i v I =i f- :i

WITNESSES Jan. 7, 1936. M. J. CONWAY APPARATUS FOR MAKING om HEARIH STEEL Filed June 20, 1954 5 Sheets-Sheet 3 v a, I I fllllllllllll. .||llIL I\ rllillllllllll IIIIIIIIIPI llllk Jan. 7, 1936.

M. J. CONWAY APPARATUS FOR MAKING OP EN HEARTH-STEEL 5 Sheets-Sheet 4 Filed June 20, 1934 6 INVENTOR mn sa -:5

woo? v Jan. 7, 1936. M. J. CONWAY 2 APPARATUS FOR MAKING OPEN HEARTH STEEL Filed June 20, 1934 5 Sheets-Sheet 5 M my mww Patented Jan. 7, 1936 UNITED STATES PATENT OFFICE APPARATUS FOR MAKING OPEN-HEART STEEL Martin J. Conway, Coatesville, Pa. Application June 20, 1934, Serial No. 431,456

- n 12 Claims. This invention relates tothe manufacture of steel or products requiring a similar heat treatment and more particularly to an improved method and apparatus for manufacturing what is known as open-hearth steel and is a continuaof rectangular shape, and burning gases which develop'most of the heat for the chemical reac-"' tions are passed over them, first from one end of the furnace and then from the other, through ports located in each end of the furnace.

The products of combustion which develop from such firing are passed out of thefurnace'in the reverse order through the ports temporarily not in use for the entrance of the heating gas and into chambers partly filled with checker brick which absorb some of the sensible heat of these products and from which they are passed onward into the furnace stack. At relatively short intervals these reversals are effected by shutting off. the gas and air at one end of the furnace and introducing them through the checker cliambers at the opposite end.

In passing througlf/the checker chambers the g'asesabsorb some of the heat stored in the checker bricks; and enterthe furnace with a high sensible heat, consequently producing a much higher temperature of combustion than can be obtained without preheating which is essential in order to provide the temperatures required for the production of open-hearth steel. In accordance with the usual practice, the re-' versals are'efl'ected at intervals of from fifteen to thirty minutes and are repeated until, the oxidation of the charge has reached a desired point. Among the disadvantages of such prior practice is the deleterious eflect upon the steel of the constantly varying temperatures resulting from the periodical reversing of the firing. In addition considerable time and heat are wasted during the reversing operations. This is due'to'the reversals taking several minutes, and to the fact that the gases contained in the checker cham bers and uptakes at the time of the reversing of the firing in each direction are passed out of the stack without reaching the furnace.

A further disadvantage is that duplicate air and fuel supplying apparatus in the way of burner ports and reversing valves are required at the. end of the combustion chamber and also corresponding duplicate sets of regenerators and reversing, valves in the exhaust passages. Such duplication of parts materially adds to the initial 1 cost of the furnace and due thereto and to the uneven heating conditions encountered together with the complicated problems resulting from the reversing operations, the maintenance of the furnace is made very costly. In addition considerable'valuable time as well as heat is lost whenrepairs are required, which is relatively frequently, and, as will be appreciated, this all adds to the cost of the steel.

With these and various other dimculties in mind it is an object of this invention to provide an improved method of producing open-hearth steel in accordance with which the steel is subjected to uniform or selectively regulated heating, whereby a considerable saving of time and operating cost as well as improvement in the 26 product is effected. n F V Anotherobject is to providea furnace for practicingthis method in which there is no unnecessary duplication of parts and in which the heating is can'ied out in a continuous uninter- 30 rupted process. This grflli yreduces the initial cost of the furnace and due to the uniformity of the heating the maintenance cost is likewise reduced. r

,Another object is to increase the life of the 36 furnace as well as increase its output over that of a furnace of the prior type having an equivavarious other novel features and advantagw of the'invention will be apparent when the followingdetailed description is read in conjunction 15 with the accompanyingdrawings of which Fig. 1 is a plan view of a furnace designed to mac-- tice this invention; Fig. 2 a vertical section taken on the line 'II-II of Fig. 1 showing in addition certain optional features which may be utilized; Fig-file. vertical section taken on the line Ill-III of Fig. 1; Fig.4 a vertical-section taken on the line IV-IV of Fig. 1; Fig. 5 a horizontal section taken on the lines V--V of Figs. 3

and 4; Fig. 6 a vertical section taken on the line to Figs 9 and of an end construction adapted for. use with 'producer gas, blast furnace gas or a mixture of gases such as blast furnace and coke-oven gas, etc.

In accordancewith the invention a furnace is provided in which one-way firing is. employed and with which recuperators are used for heating the air or air and fuel burned in the furnace, the furnace being designed at its firing end to provide a burner adapted to thoroughly mix the fuel and air without regard to the customary necessary dimensions for exhaust gases which in the past has militated seriously against proper and efilcient firing. The other end of the furnace in turn is equipped with a suitable outlet,for conducting the products of combustioh into a slag pocket or chamber in which the solids carried by .such products from the combustion chamber are permitted to collect and from whence the gas is discharged into the recuperators free of such ingredients.

In practicing the invention the furnace is first lighted and brought up to charging temperature, during which period the recuperators through which the fuel and air flow oppositely to the products of combustion are gradually elevated in temperature. When a proper temperature for charging is provided the charge is placed in the.furnace and subjected to a con-- tinuous uninterrupted uniform heat until its treatment of the charge is completed.

To reiterate, according to the invention the furnace is fired from one end only, being equipped for that purpose at its firing end with an accuratelyand efliciently designed main burner port 5 and an auxiliary burner port 6. The main burner port is adapted to supply most of the fuel-and air=utilized in the furnace and is preferably placed as low as possible in order to sweep the hearth and sinter the materials in preparing the hearth for the charge.'

The auxiliary ports 6, which may be eliminated if not required, or increased in number if desired, depending upon the size of the furnace, are mounted on the roof I and preferably at a steep angle, so as to direct their supply of fuel and air at high velocity toward the metal contained in the hearth in a fashion to maintain a uniform temperature throughout the furnace.

The roof 'I which constitutes the top of the combustion chamber It may be plain or arched and made out of any suitable refractory material. For support it is suspended from a series of cross-beams 8 which are covered over with sheet steel or other suitable material in such a manner as to provide a cooling chamber 9' extending over the entire roof of the combustion chamber. To} permit a flow of cooling air to be circulated through such chamber to cool both the roof and its supporting structure, openings II and I2 are provided at opposite ends of the furnace, and avent or connection I3 is located 5 on the top thereof for connecting it to any suitable suction device capable of providing the proper circulation.

Back of I the hearth 2 there is provided a down-draft passage I 4 through which the products of cumbustion are conducted from the com bustion chamber lll'into a slag pocket or chamber l6. This chamber is adapted to collect the solids carried out of the combustion chamber by the hot gases, and from it such gases, free 15 of the ingredients, are passed into a series of recuperators l1, l8 and I3 which are employed to recover the waste heat from such products and to utilize it in preheating the air delivered to the combustion chamberby the burner ports 2;) Sand 6.

- The first of these recuperators consists of a substantial rectangular housing-2l constructed of suitable refractory material such as fireclay brick properly reinforced with steel buckstays '25 (not shown). Communicating with the wall of this housing adjacent the furnace in the upper mid=section thereof is a duct or tlmnel 26 leading from the slag pocket l6. Opposite the inlet of this duct as shown in detailsin Figs. 3, 5, 6, 7 and 8 there is provided a series of honeycomb-like walls 20 formed of somewhat spoolshape fire-proof tile or blocks 22 which are supported by a transverse wall 23 located above the base of the recuperator, and extended to a second transverse wall 30 spaced from the roof of the recuperator.

As shown in Figs. '7 and 8 the blocks compris- -ing these intermediary vertically disposed honeycomb-like walls 20 consist of a pair of 40 square laterally spaced fiat end walls 22a. connected together by tubular center sections 22b, said square end sections being provided with suitable interlocking means (not shown) for rigidly effecting their assembly in the form of a wall. As illustrated these walls form a series of channels 24 opening into the inlet 26 and through which the waste products are passed into an outlet duct or tunnel 43 connecting this recuperator with the next recuperator l8, and as will be appreciated by reason of the tubular sections in the blocks 22 thesegases are permitted to pass freely between such channels 24. Connected to the chamber 30 formed in the recuperator below the transverse flow "block supporting wall 23 is an airduct 42 by which the outlet of recuperator I3 .is connected to this recuperator and from this chamber the air is passed upwardly through openings 25 in the wall 23 between the end sections 22a of the blocks 22 and about the tubular sections 22b into a chamber 10 formed by the transverse wall 30 passage 35. To provide'a definite path for the waste gasfrom this up-dra'ft passage 35 to the down-draft passage 36 the middle section 39 of the roof of the recuperator is'raised and the upper ends of the walls 32 and 33 are joined by a covered wall 40.

For passing the air through this intermediate recuperator from its air chamber 31 which is connected by a conduit or tunnel 4I- with the outletof the last recuperator I9 and the chamber 38 which is connected by a tunnel 42 with the inlet chamber 80 of recuperator .Il, a series of tiers of tubes 44, and 44a is mounted in the walls 3|, 32, 33 and 34, respectively, and to facilitate. the mounting of these tubes as well as for cleaning them, the walls 32 and 33 in the center of the recuperator I8 are spaced sufllciently far apart to form a chamber 40a in which a man may work. It is also contemplated, that suitable baffling (not shown) may be inserted in the various recuperators to channel the gas through them in such a way. as to bring about eflicient transfer of the heat from the exit gases to the preheated air for combustion. Furthermore, while tubes are shown in the recuperators for conducting the air through them, any type or shape of passage may be used. so long as mixing of the exhaust gas and air is not permitted. I

From the lower end of the down-draft passage 36 in the recuperator I8 a flue tunnel 50 is connected to the bottom of the recuperator I9 and through it the waste gases are passed upwardly between vertically disposed walls 45 to an outlet flue 45, horizontal baflles 41 being arranged between the walls 45 to provide a more circuitous I path for the incoming air.

To provide a fixed draft for the furnace the 'flue 46 is connected to the inlet of a fan 48 which is operated by a motor 40 and has its outlet in turn connected by a flue to 'a stack 5m, and for installations where it is non-essential to pass all of the products of combustion through this recuperator, a by-pass stack connection I00 is connecteddirectly from the tunnel 50 to the stack 5Ia, 'being provided with a damper I0l for controlling the amount of gases passed through it. As illustrated best in Fig. 5 the walls 45 are mounted in pairs and these pairs are spaced from each other to provide passages 52 for the passage of the air through the recuperator, the lower ends of the latter passages being arranged to communicate with tunnel 4| leading to the air inlet of recuperator I 8 and their upper ends with a conduit 53 which is connected to the outletof an air drafting fan 54 which is operated by a motor 55. 'As-shown, to take advantage of the heat absorbed by the air passed through the cooling chamber 3 over the roof of the furnace, and also to make use of the air drafting fan for'cooling theroofas well as supplying air. to the combustion chamber inthe furnace; the inlet'of the fan 54 is connectedto the vent I3 in the top of the furnace by a conduit 55 having a draftingdamper 51 in it.

For communicating the air supplied by the fan 54 as it leaves the outlet chamber I0 of recuper-' ator I! to' the burner ports 5 and 5. conduit or tunnel 58 is utilized.

In the operation of the furnace the products of combustion are drawn from the combustion chamber I0 by the drafting fan 43 through the recuperators I1, I3 and I9 in the path marked by the double-headed arrows in the drawings, which is traced from chamber I Ii through the passage I4 into the slag pocket I6, thence by passage 26 into the upper wall of the recuperator II through which it is forced downwardly through the channels 24 and the tubular section's 22a of the baflle blocks 22 into the down-draft through the joints which develop between the passage 21 which carries it into the bottom of the up-draft passage 35 and the recuperator I8. 1 In this passage it passes by the tube 44a, the down-draft passage 36, around the tubes 44 and by way of the passage or flue 50 into the bottom of recuperator I9 from whence it passes upwardly between the walls 45'into. the flue 45 and then by way of the fan 48 into the flue 5| which carries it to the furnace stack and the atmosphere. 7 l

The air in turn is forced by fan 54 through recuperator I 0 by way of passage 52 into the chamber 31 of recuperator I8 from whence it passes through the tubes 44 and 4411. into chamber 33 and from there by passage 42 into the chamber 50 of recuperator II. From this ohamher it passes through the channels 25 defined,

.by the walls into the chamber 10 and from thence by wayof duct 50=to the burner ports 5 and 6. '3

As shown in Fig. 2, fuel is fed into the furnace by a passage 5| which has branches 62 and 63 running to the main and auxiliary ports 5 and 6. However, as shown in Figs. 9, 10, 11 and 12, the burner end of the furnace may be differently constructed as required for handling different kinds of fuel.

In Figs. 9 and 10, a form of burner construction is illustrated for use with coal tar, oils,

natural gas and oils, while in Figs. 11 and 12 a type of furnace construction is shown for use with natural gas, coke oven gas, producer gas, blast furnace gas, mixed gas and the like. In the latter, inlet 6Ia is particularly adapted for producer gas.

As will be appreciated by those. skilled in the art, the tubular blocks 22 employed in the first recuperator I! are made of some suitable refractory material such as chrome or mullite which will not be deleteriously affected by the products of combustion or the impurities in the form of oxides or slags which they carry.

It will also be appreciated, however,. that it is very difficult in view of the great temperatures and great changes in temperature encountered by such recuperators to maintain a sealed contact between the blocks. 22 because of the considerable expansion and contraction which will -take place between them. Nevertheless it is air is passed therethrough at a pressure .higher than atmosphere while, the waste gases are 5 passed through at a pressure below atmosphere, which in a construction of this type would normally tend to produce a considerable. leakage' of .the air into the waste gas products recuperator blocks as a result of the cracks formed by expansion and contraction.

To eliminate this condition, or in other words balance these pressures, an auxiliary fan I02 is provided which is equipped with 'a motor I03 and arranged with its inlet connected bya duct I04 with the air passage 42 connecting the recupera tor I8 to therecuperator I1, and its outlet I04a connected to a duct I05 which is projected into the tunnels 5B in'a'manner to function as a jet tending to increase the suction on the air passing through the recuperator II, this arrangeone of a number of well-known constructions of this character and connected by suitable tubes I08 and I08 with the channels 25 between the top and bottom of the recuperators and the channels 24 defined by the walls 20. This regulator, as will be readily appreciated without necessarilydescribing the details thereof, is connected to suitable control means I06 connected to the supply circuit IIO of the fan motor I03 to so regulate the operation of the fan I02 as to maintainthe desired air pressure in the recuperator.

It will also be appreciated that by reason of the passages 24 in the recuperator II being made relatively large as illustrated, they provide an unobstructed and free pmage permitting a slow movement of the gas in a general downward direction so that the gases effectively give up their heat by radiation to the outer walls of the blocks 22 as well as to the surface of the tubular sections 22b which are in direct contact with the air passing upward and around them and the channels formed between them and sections 2211. Such construction also militates against any clo ing of the recuperator by reason of any deposit which may not settle out of the waste products in the slag pockets settling in such channels. 1

In the second recuperator I8, due to the temperature of the gases being somewhat reduced by the time they reach the tubes I4 and a, the latter may be made of diiferentmaterial than that used in the'formation of blocks 22 in the recuperator l1, and preferably a material such as carborundum which has a higher coefficient of conductivity than mullite or chrome, while in recuperator I9 metal may be used to form the air and gas passage. Such metal will suflice for the construction and is preferably used because of its high heat conducting qualities.

To provide a maximum efiiciency for the recuperators and a cost, the cross-section of the air and gas passages is reduced from the first to the last recuperator in accordance with the variations'in the volume of the gas and air passing through them which vary as their temperatures. In their construction, consideration is also given to the control over the speed of passage of the air andgas through them to afiord the maximum transfer of heat.

To provide for forcing air into the roof-cooling chamber 9 for cooling purposes only a separate fan 8I disposed to be operatedby a motor 82 may be mounted with its outlet connected by a conduit 83 with the duct 56, a gate 84 being provided in the duct 83 for disconnecting it from the duct 58 when the fan 54. is used.

To permit the operation of the fan 54 when the fan 8I is operated, a shut-01f gate 85 may be provided in duct 56 on the draft fan side of the duct 83, and an outlet gate 86 may be provided opposite thereto in 'duct 56 for letting the inlet air enter the duct ahead of the regulating valve 51. When the fan 8| is operated the openings II and I2 are closed so that the cool air forced in the chamber 9 will be forced through the interstices between the brickwork of the furnace roof and not only cool the roof but also provide a shield on the underside of the roof to protect the roof against the products of combustion inthe combustion chamber. As further precaution against injury to the roof from overheating, ventilator 'Il may be present in the given quantity of charge considerably increased. In addition, its cost of production is materially reduced by reason of the fact that the overhead accurately regulated and its quality by reason thereof improved as well as its volume from a.

cost incidental to the installation and mainte- 4 nance of the furnace is materially reduced as well-as the fact that the time required for reducing a charge to the proper constituents is greatly lessened inasmuch as the intermittent time losses due to varying reversals are eliminated.

In addition, among the detailed advantages of the invention is the saving in cost efiected by the elimination of reversing valves, duplicate burners, double air regenerators and the like. Another is the'saving in maintenance possible because of the longer life which the furnace enjoys due to .the'uniform heating conditions under which it operates. A further advantage is the greater economy obtained by means of the greater heat efficiency flow from the unidirectional firing. In, addition, there are numerous other advantages which wi1l be apparent to those s ed in the art.

While the furnace as illustrated and described constitutes an embodiment of the invention intended more particularly for refining steel, it will be understood that the invention may be applied to other processes where high temperatures are such as in the meltingof glass and the like.

According to the provisions of the patent statutes, I have explained the principle and mode of operation of my invention and have illustrated and described what I now consider to represent 'its best embodiment. However, I desire to have it understood that within the scope of the appended claims the invention may be practiced otherwise than as" specifically illustrated and described.

I claim':

1. An open hearth furnace comprising a melting hearth forming the bottom wall of an enclosed heating chamber, heating means at one end of the chamber above the hearth embodying fuel and air supply means, means for withdrawing the products of combustion at another end of said chamber, and means for preheating the air supply to the heating means by the heat of the products of combustion leaving the heating chamber including means for balancing the pressure of the preheated air entering the furnace and the products of combustion or waste gases leaving the furnace chamber, said pressure balancing meansbeing responsive to andcontrolled by variations in the pressure of the waste gases or products of. combustion leaving the furnace chamber and the preheated air entering said chamber.

2. In an open hearth furnace, the combina tion with a. melting chamber of a recuperator ducting waste gasesand air under pressure through said recuperator passages, and means responsive to the pressure differential of the fluids in said recuperator passages for changing the pressure of the air to substantially the same pressure as the waste gases.

3. An industrialheating furnace comprising a heating chamber, heating means at one end of the chamber above the hearth embodying fuel and air supply means, a waste gas passage for withdrawing the products of combustion at "another end of said chamber, a recuperator communicating with said waste gas passage and with the air supply means and embodying heat ex-,

change passages for the waste gases and air to be preheated, means for maintaining constant pressure of the air in said heat exchange passages, and means for increasing the volume of air delivered to the heating chamber independently of said pressure controlling means.

4. An industrial heating furnace comprising a heating chamber, heating means at one end of the chamber above the hearth embodying fuel and air supply means, a waste gas passage for withdrawing the products of combustion at another end of said chamber, a recuperator communicating with said waste gas passage and with the air supply means and embodying heat exchange passages for the waste gases and air to be preheated, a pressure regulator operative in response to variations in the pressure of the gases, and air passing through, said heat exchange passages for maintaining a predetermined relation of the pressure in the waste gas and air passages.

5. An industrial heating furnace comprising a heating chamber, heating means at one end of the chamber above the hearth embodying fuel and air supply means, a waste gas passage for withdrawing the products of combustion at another end of said chamber, a recuperator communicating with said waste gas passage and with the air supply means and embodying heat exchange passages for the waste gases and air to be preheated, air'pressure means connected to the air passages of the recuperator and also.

directly to the air passage leading to the heating chamber, and pressure regulating means for automatically regulating the air pressure means to vary the volumes of air delivered to the air passages of .the recuperator and the air passage of the furnace chamber.

6. [in industrial heating furnace comprising a heating chamber, heating means at one end of the chamber above the hearth embodying fuel and'air supply means, a waste gas passage for withdrawingthe products of combustion at one end of said chamber, a recuperator communieating with said waste gas passage having heat exchange-passages for the waste gas and air supplied to the furnace chamber, a blower connected to the recuperator to supply air to the heat exchange passages, a motor for said blower, a

regulator responsive to the waste gas pressures combustion in the heating chamber, awaste gas passage for drawing the products of combustion from thefurnace chamber, a primary refractory recuperator having heat exchange passages communicating with the waste gas and air delivering passages of the furnace, a secondary metallic 5 recuperator having heat exchange passages in communication with the heat exchange passages of the first recuperator, means for delivering air under pressure to and from the secondary re- 7 cuperator to the primary recuperator, means 10 for exhausting the waste gases from the furnace chamber through said recuperators in the ordermentioned, and means for supplying additional air to the first recuperator in accordance with a desired volume and pressure of the air passing of burners, fuel supply means therefor, air pas- 2o sages for delivering air to the burners to support combustion in the heating chamber, a waste gas passage for drawing the products of combustion from the furnace chamber, a primary refractory recuperator having heat exchange passages com- 25 municating with the waste gas and air delivering passages of the furnace, a secondary metallic recuperator having heat exchange passages in communication with the heat exchange passages of the first recuperator, means for delivering air 30 underpressure to and from the metallic-recuperator to the primary recuperator, means for exhausting the waste gases from the furnace chamberthrough the primary and secondary recuperators in the order mentioned, and means 3 for supplying additional air to the heat exchange passages of the primary recuperator and to the air passage leading from the recuperator to the furnace chamber.

9. In an industrial heating furnace, a heating 0 chamber, heating means comprising a plurality of burners, fuel supply means therefor, air passages for delivering air to the burners to support combustion in the heating chamber, a waste gas passage for drawing the products of combustion 5 from the furnace chamber, a primary refractory recuperator having heat exchange passages communicating with the waste gas and air delivering passages of the furnace, a secondary metallic recuperator having heat exchange passages in 50 communication with the heat exchange passages of the first recuperator, means for delivering air under pressure to and from the metallic recuperator to primary recuperator, means for exhausting the waste gases from the furnace 55 chamber through the primary and secondary recuperators in the order mentioned, and means for balancing the pressure of the'air and waste gases in the heat exchange passages of the firstnamed recuperator. J

10. In an open hearth furnace, a heatingchamber, fuel burners and preheatfair passages for said chamber, a waste gas passage leading from saicrchamber, a cooling chamber above the furnace, exhaust means'for said cooling cham- 65 her, a plurality of recuperators having heat exchange passages for successively receiving the waste gases from the furnace chamber and delivering preheated air to support combustion in said chamber, and means for drawing air 7 a waste gas passage leading 15 r for said chamber,. a waste gas passage leading from said chamber, a cooling chamber above the furnace, exhaust means for said cooling chamber, a plurality of recuperators having heat exchange passages for successively receiving the waste gases from the furnace chamber and delivering preheated air to support combustion in said chamber, means for drawing air through the cooling chamber above the furnace and. delivering it to the recuperators, and means for supplementing the air supply after it has passed from the recuperators.

12. In an open hearth furnace, a heating chamber, fuelburners and preheat air passages from said chamber, a cooling chamber above the ber, a plurality of recuperators having heat exchange passages for successively receiving the waste gases from the furnace chamber and delivering preheated air to support combustion in said chamber, means for drawing air through the cooling chamber above the furnace and delivering it to the recuperators, and means for supplementing the air supply to the recuperators and to the preheated air passage leading to the furnace chamber. a MARTIN J. CONWAY.

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