US2130925A - Slag pocket construction - Google Patents

Description

Sept. 20, 1938. l. c. JOHNSTON 2,130,925

SLAG POCKET CONSTRUCTION Filed July 9, 1937 2 Sheets-Sheet l INVENTOR. [Pr/n C; do/msfov wL/WMM ATTORNEYS.

p 1938; l. c. JOHNSTON 2,130,925-

SLAG POCKET CONSTRUCTION Filed July 9, 1937. 2 Sheets-Sheet 2 IN VENTOR. [FY/'17 C. dO/msfo)? I I} %ma 1% ATTORNEYS Patented Sept. 20, 1938 PATENT OFFICE SLAG POCKET CONSTRUCTION Irvin O. Johnston, Youngstown, Ohio, assignor to John M. Crowe, Fort Mitchell, Ky.

Application July 9. 1931. Serial naiszxme 'lClaims.

This invention relates to a slag pocket construction for industrial furnaces such as are used for melting large quantities of various metals. The invention is illustrated and described as applied to an open hearth furnace,'but

its use in connection with other types of furnaces will readily be appreciated by persons conversant with the art.

An object of the present invention is to increase the efllciency of industrial furnaces by simplifying the removal of slag therefrom, resulting in a considerable saving of time, effort and expense.

Another object of the invention is the accomplishment of the above object in such a manner as to avoid shutting down the furnace for the removal of the slag, and without danger of explosion, or of injury to workmen engaged in the work of slag removal.

These and other objects are attained by the means described herein and disclosed in the accompanying drawings, in which:

Fig. 1 is a vertical cross-sectional view of a furnace embodying the invention, certain parts being broken away and others being shown diagrammatically. I

Fig. 2 is an elevational view of a brick-enclosed slag deposit as it appears when disassociated from the furnace.

Fig. 3 is a detail view of a canopy arch member constituted of a group of fire bricks embraced by a metal band or bar, this forming a detail of'the present invention.

Fig. 4'is an enlarged cross-sectional view taken on line 44 of Fig. 1, and showing a slag accumulation to be displaced as in Fig. 2.

Fig. 5 is a view looking down on one corner of a modified form of slag pocket.

To persons skilled in the art to which the present invention appertains, it will readily be un derstood that the ordinary industrial furnace comprisesa melting bed and means including uptake and downtake lines or downcomers for the cyclic transfer oi. fuel and heated gases of combustion past the bed during the operation of the 45. furnace.- Beneath the downcomers are located the slag pockets, which function to connect the rain of slag that is carried downwardly through the.

downcomers as the heated gases of combustion are advanced in their passage toward the checkers or such other preheating apparatus as may form part of the furnace equipment. The details of all of the foregoing are foreign to the present invention, and need not be made the subject of a lengthy explanation, all this being well within 55 the knowledge of persons familiar with the operating principles of industrial furnaces for the melting of steel, iron, and other metals in large quantities.

The present invention is concerned with that region, in a furnace, wherein the slag accumulates and eventually becomes a homogeneous mass that requires removal at intervals. The removal of this accumulated slag heretofore presented a perplexing problem, and was accomplished only by shutting down the furnace for nearly a week while workmen labored within the slag pockets to dislodge the slag in relatively small chunks; and this cumbersome method of slag removal is still being employed by the majority of largest steel plants, notwithstanding the existence of numerous patent disclosures purporting to obviate the difllculty, expense, and waste of time involved in removal of the slag.

Prior inventors have attempted to solve the slag removal problem by providing auxiliary or secondary slag pockets which were expected to receive molten slag from the main slag pockets of the furnace, with the aid of reheating burners playing upon the slag to re-liquefy it for ultimate removal. This plan has not proven successful and has been rejected by the industry as being impractical, the major dlfllculty being that of re-melting the slag after it has once solidified as a sizeable mass. The application of burners resulted in merely burning a hole in the mass, without rendering the mass mobile; and heat of such intensity and volume as a burner is capable of producing would not re-liquefy the whole mass of slag so as to render it fluid.

I have discovered that an auxiliary slag pocket can afford a solution to the slag removal problem, provided that is is properly related to the main slag pocket of the furnace. That is, provision must be made for a constant substantial circulation of the furnace heat not only in the main slag pocket, but also in the auxiliary pocket, so that the slag may not chill and solidify en route to the auxiliary slag pocket. To accomplish this,

vthe auxiliary slag pocket 6 must be connected with the main slag pocket I by a large or high head opening 8. This opening should be several feet in height, or suiilciently high to afford a free circulation of the intense heat of the furnace into and from the auxiliary slag pocket. In practice, the opening 8 has been made approximately six feet high, with excellent results in securing an accumulation 9 of slag outside the main slag pocket 1, without the use of secondary burners or tools of any kind. The free and substantial circulation of the intense heat of the furnace CJI continuously into and from the auxiliary slag pocket 9', during the operation of the furnace, is considered the most practical and effective expedient yet devised for the displacement of slag from the main slag pocket of the furnace. Low head openings between the main and auxiliary slag pockets have proven ineffective for the purpose, as evidenced by the fact that secondary burners heretofore were proposed to effect movement of the slag from the main pocket to the auxiliary pocket.

A further improvement which I have devised, is that of constructing the auxiliary slag pocket in such manner as to easily efi'ect removal of the slag as a single solid chunk, using a crane or the like which may load the slag directly onto a conveyance for suitable disposal thereof. By means of this improvement, the work of slag removal which formerly required several days time, is accomplished in less than an hour, and the furna'ce need not be disabled or shut down in the interim. A description of the indicated improvement follows.

The .character 92 indicates an exterior wall of the furnace, above which is suitably supported the melting bed l3 and other essentials which need not be referred to in connection with the instant invention. It will be noted that the high 7 head opening or passage 8 previously referred to, is formed in the exterior wall l2; and at a location exteriorly of the furnace, and below the level of the floor H of the main slag pocket, there is provided an open topped receptacle It which, by preference, is constructed of concrete or any other durable material suitable for the purposes hereinafter set forth. The receptacle M may be imbedded in the earth as indicated, where circumstances permit such construction. In any event, the receptacle M is stationary and may be considered a permanent part of the furnace.

The permanent receptacle M has a floor l5 and upwardly and outwardly flared inclined walls it adapted'to be lined ,with a suitable insulating material which, for practical purposes, may be sand or an inexpensive commercial insulating substance. The floor or bottom of the receptacle it, as well as the inclined walls 16, is adapted to be lined as just explained. The layer of insulating material I! is thereafter covered with a suitable refractory material, such as fire clay in either the plastic or block form, as indicated at 58. According to the present invention, slag deposited by the downcomers on to the main slag pocket floor I3, will find its way into the lined receptacle or auxiliary slag pocket where it solidlifies and eventually becomes an accumulation of slag indicated by the character 9. As before explained, the high head opening or passage 8 in the exterior wall l2 of the furnace makes possible the transfer of slag from the main slag pocket I to the auxiliary slag pocket 6, without the aid of implements or burners.

Upon the circumferential upper edge 19 of receptacle I 4,- there is provided an insulated refractory cover which closes the auxiliary slag pocket and connects it to the main slag pocket through the high head opening or passage t.

a crane hook .20 to be employed for lifting the aiaaeaa chunk (see Fig. 2) the material of thepit it may be recessed as at 2%, 2i and 22 for housing suitable lifting devices such as cables, chains,'or the like 23. Such lifting devices may be placed in position as indicated in Fig. 4, prior to lining of the auxiliary slag pocket, the looped ends 24 thereof being permitted to extend as shown in Fig. 4. The lifting means 23 may be protected from heat radiation by means of the sand or insulating material if which may be packed into the recesses 20, El and 22 at the time of relining the auxiliary slag pocket.

At this point, it may be noted that the cable 23 of Fig. 4c may be considered merely a leader to be used for pulling a larger and more sub- As was mentioned previously, theinsulated refractory cover of the auxiliary slag pocket preferably is of temporary construction, and as such, it may be built up of masonry, preferably in the form of fire brick walls 25 and 26 resting upon the upper faces is of the side walls of receptacle id. The top surfaces of the masonry walls 25 and 26 preferably are inclined upwardly toward the top of the opening or passage 8, from the far wall of the receptacle as indicated in Fig. 1.

Spanning the opposed masonry walls 25 and 26, is a series of arched deck members, most clearly shown in Figs. 3 and 4, these members each comprise a long arcuate metallic bar 27 having downwardly turned ends 23 and 29 arranged to embrace a series of blocks or bricks 30 of fire clay or other suitable material. These arched units are placed inside by side relationship along the tops of the masonry walls 25 and 26 as illustrated in Figs. 1 and 4, to'furnish the refractory cover previously mentioned. After the arched units are placed in position as shown, they may be cemented over with a suitable thickness of plastic substance which may be clay or mud of one kind or another, as indicated by the broken line 3| of Fig. 1.

While an insulated refractory cover of the character just described has many advantages such as easy placement and removal with a minimum of time and effort, it is to e understood that other types of covers, and pa ticularly one-piece covers of suitable design, may be substituted for'the refractory cover herein specifically described. Likewise, it is to be understood that the masonry walls 25 and 26 are but one form of means that might be employed for supporting thecover over the top of the auxiliary slag pocket for excluding outside air and con-- necting the auxiliary slag pocket with the main slag pocket, through the high head opening 8.

The provision of an inclined cover for the auxiliaryslag pocket. has the advantage of assisting the heated gases of combustion to circulate from the main slag pocket into the auxiliary slag pocket, and back into the main slag pocket.

From the foregoing it should be understood that the particular construction described and illustrated herein insures a fluid condition of the slag from the time it is deposited upon the floor IQ of the main slag pocket until it reaches its destination within the auxiliary slag pocket. If

the auxiliary slag pocket were not so associated with the main slag pocket as to maintain a high degree of heat in the slag throughout its course a i accum ated a the w the lining W of travel to its destination, the slag would chill bodily from the exterior pit I4. To facilitate the removal of the accumulated mass as a solid and pile up in the region of the opening 8, and the auxlliary slag pocket would receive no appreciable amount of slag from the main slag pocket.

et floor.

The operation of the device is as follows:

Assuming that the auxiliary slag pocket has been built up and associated with a furnace as indicated in Fig. 1, and that the furnace is in operation, particles of slag will be dropping from the downcomer 32 and will be'deposited upon the floor l3 of the main slag pocket I. When the deposit becomes of sufllcient magnitude to fiow, it will enter the high head opening 8 and run into the intensely heated auxiliary slag pocket 6, seeking a level upon the floorof the auxiliary slag pocket rather than clinging to the region 33 and the adjacent wall of the auxiliary slag pocket. This process of slagmovem'ent will continue until the auxiliary slag pocket is filled to approximately the level of the main slag pock- The movement of the slag as,just described may be either continuous or spasmodic, as determined by changing heat conditions in the furnace from time to time.

When the level of slag in the auxiliary slagpocket reaches a predetermined height, workmen are assigned "to the task of removing one or two of the arch units close to the upper part of the high head opening 8, whereupon the workmen proceed to temporarily block up or close the opening '8. All this may be accomplished while the furnace is in operation, if desired.

After the opening 8 has been closed temporarily in the manner just described, all of the arched cover units 21 are removed, and the masonry.

walls 25 and 26 are demolished, leaving the looped ends 24 of the lifting means or cables 23 exposed so that a crane hook such as 20 of Fig. 2 may be readily applied to the loops 24 for lifting the chunks of slag en masse from the concrete receptacle or pit l4. In as much as the entire operation above described is performed exteriorly of the furnace, there is no reason for workmen entering'the furnace proper, nor does the furnace suffer any destruction or loss of operating time by reason of 'the removal of slag. As indicated in Fig. 2, the lining bricks l8 generally will cling to the accumulationof slag, and be removed bodily therewith. These lining bricks l8 may be old bricks which are plentiful about the premises of steel plants, and for that reason the loss of the bricks is of negligible importance.

After the accumulation of slag has been removed from the concrete pit or foundation 14, the work of relining for a subsequent deposit of slag in the auxiliary pocket is begun. First, the cable or lifting means 23 is placed within the continuous recess or channel 21-20-22 as indicated in Fig. 4 and thereafter, the linings I! and I8 are applied. Upon completion of the lining operation, the masonry walls 28 and 28 are rebuilt upon the upper faces .of the receptacle walls, and the arched refractory cover units 21 are placed in position as illustrated in Fig. l. I

All openings and cracks are properly plugged with fire clay or the like, and a layer 3| of plastic material is applied to render the auxiliary slag pocket entirely airtight so that the furnace heat may not escape from any part of the auxiliary slag pocket. When the auxiliary slag pockethas again become filled, the operation of slag r mit the flame from the furnace to roll or lap in and out of the auxiliary slag pocket, while the slope or inclination of the cover directs the flame downwardly upon the accumulated slag. In constructions employing a large and properly situated high head opening 8, the exterior refractory cover need not be inclined to the extent illustrated, but may approach or assume a horizontal disposition. The purpose of arching the auxiliary slag pocket cover is to impart thereto a maximum strength, therefore, a flat cover of suitable strength would suffice.

Attention is now directed to Fig. 5 which shows an auxiliary slag pocket corresponding to that of Fig. 4, and embodying certain refinements and improvements. The slag pocket of Fig. 5 is viewed at one corner, and shows the construction as seen when looking down from the -level indicated by theline IQ of Fig. 4. As in the construction heretofore described, the modified slag pocket comprises the open topped receptacle or pit l4 having formed therein the recesses or channels as disclosed in Fig. 4, the character 22 being representative of that part of the channel which is formed in one of the upright walls of the pit. It will be noted that the receptacle or pit is lined with sand or other insulating material as at I1, this lining being held in placed by the lining bricks l8 as explained in connection with Fig. 4.

The construction of Fig. 5 distinguishes from that of Fig. 4 in the provision of a course 40 of channel closing bricks extending along the floor and opposite sides of the pit or receptacle, and so arranged as to provide a continuous complementary recess or channel 4| in the. block or accumulation of slag which fills the auxiliary slag pocket as heretofore explained. The complementarychannel or recess along the bottom and adjacent sides of the slag accumulation is ormed by the inwardly set course 40 of channel closing bricks resting upon the two adjacent courses 43 and 42 of channel border bricks which may contact the inner surfaces of the bottom and the contiguous side walls of the pit or receptacle l4. Little or no sand or insulating material I1 is employed in the region of the channel 22 and its complementary'channel 4!, the primary purpose of the omission of sand or insulating material I! being to avoid clogging of the continuous channel 22-. The channel thereby is kept clear so that a leader cable 23 v normally disposed therein may easily be pulled through the channel, to draw a heavy and substantial lifting cable or the like 43 through the channel and into positionfor lifting of the accumulated slag mass as illustrated in Fig. 2 wherein the cables 23 correspond to the cable 48 of Fig. 5. The formation of the complementary channel 4| in the lining of the slag pocket insures against slipping or shifting of the lifting cable 43 as the mass of slag is drawn from the pit with the aid of a crane or derrick as heretofore explained. Fig. 5clearly shows the floor and two inclined sides of the pit or receptacle lined with fire brick, all as explained in connection with, Fig. 4. If the major portion of the interior of the pit or receptacle is protected against the adhesion of molten slag by reason of the sand lining I], there will be little if any resistance to lifting of the slag mass, together with the lining bricks, from the pit or receptacle. The sand lining virtually performs the function of a multiplicity of ball bearings which facilitate disasseciation of the slag mass and lining bricks from the interior of the pit or receptacle l4.

It is to be understood that courses of bricks 42 and 43 keep the channels 22 and 4! sufficiently clear of sand to enable withdrawal of the leader cable 23 and placement of the lifting cable 43 as explained. With the Fig. 5 construction, the lifting cable 43 is never subjected to the intense heat of the molten slag of the auxiliary slag pocket, wherefore said lifting cable is kept in the best of condition for performance of its strenuous lifting function. The smaller and less expensive leader cable 23 may be replaced from time to time, should it be affected by the intense heat of the slag.

It should be understood that; the channel or recess 22 extends down one side wall of the pit or receptacle-across the floor thereof, and up the opposite side wall, to form a continuous passage corresponding to that indicated at 2t, 2!, and 22 of Fig. 4.- The complementary channel 4| formed by the courses of bricks 40, 42, and 43 likewise is continuous about the bottom and two .sides of the lining structure, to furnish a suitable seat or groove in the mass of slag to be ultimately formed in the auxiliary slag pocket. The seat or groove, as previously explained, houses the lifting cables during the lifting operation exemplified in Fig. 2.

It is to be understood that various modifications and changes may be made in the slag pocket construction herein illustrated and described, without departing from the spirit of the invention. or the scope of the appended claims.

What is claimed is:

l. The combination with a furnace having a main slag pocket for receiving slag produced during the operation of the furnace, of an apertured wall forming part of the furnace and constituting a part, of the main slag, pocket, an

auxiliary slag pocket at one side of the apertured wall, and communicative with the main slag aperture having a high head of such proportions as to permit flame from the region of the main slag pocket to rolland lap materially into the interior of the auxiliary slag pocket for circulating and maintaining an intense heat in the auxiliary slag pocket and through the aperture which connects it with the main slag pocket, thereby to preclude any possibility of such chilling of the slag as would cause substantial solidification during movement of the slag from the main slag pocket into the auxiliary slag pocket.

2. The combination with a furnace having a main slag pocket for receiving slag produced during the operation of the furnace, of an apertured wall forming .part of the furnace and constituting a part of the-mainslag pocket, an auxiliary slag pocket at one side of the apertured wall, and communicative with the main slag pocket through the. aperture of the wall, said aperture having a high head of such proportions as to permit flame from the region of the main slag pocket to roll and lap materially into the interior of the auxiliary slag pocket for circulating and maintaining an intense heat in' the auxiliary slag pocket and through the aperture which tachedyall as a single unbroken mass.

3. The combination with aiurnace having an interior main slag pocket for receiving slag produced during the operation of the furnace, of an apertured wall forming part of the slag pocket and having an exterior side, an auxiliary slag pocket located at the exterior of the wall and outside the limits of the furnace, and communicating with the main slag pocket through the aperture of the wall, said auxiliary slag pocket having a displaceable lining upon and within which the 4. The combination with a furnace-having an interior main slag pocket for receiving slag produced during the operation of the furnace of an apertured exterior wall forming part of the slag pocket, a pit formed in the earth outside the furnace limits, and below the floor level of themain slag pocket, means covering the pit and con-. necting it with the aperture of the main slag pocket so as toconflne the furnace heat to the interiors of the main slag pocket and the pit, a lining for the pit, means for lifting bodily as a mass the lining and such slag as may accumulate and solidify-thereon after passing through the aperture from the mainslag pocket into the lined pit outside the furnace, and channel means in the pit exteriorly of the lining, for normally housing said lifting means.

5'. In combination with a furnace having an interior main slag pocket and an exterior wall with an upright high head opening formed therein in communication with said main slag pocket, of an auxiliary slag pocket to receive slag from the main slag pocket through said opening as the furnace is operating, said auxiliary slag pocket comprising a permanent pit having a floor and upwardly diverging walls located entirely outside the furnace, adjacent to said opening, and below the floor level of the main slag pocket, and including a temporary lining adapted to confine the slag flowing into the pit from the main slag pocket, a temporary cover upon the lined pit for placing the interior thereof in communication with the high head opening of the exterior furnace wall, said cover being adapted for excluding outside air, except when removed to enable accumulated slag to be lifted together with the lining as a unitary mass, from the interior of the permanent pit,

. 6. In combination with a furnace having an interior main slag pocket and an exterior wall with an upright high head opening'formed therein in communication with said main slag pocket, of an auxiliary slag pocket to receive slag from the main slag pocket through said opening as the ,furnace is operating, said auxiliary slag pocket comprising a permanent pit having a floor and upwardly diverging walls located entirely outside the furnace, adjacent to said opening, and below, the floor level of the main slag pocket, and including a temporary lining adapted to confine the slag flowing intothe pit from the main slag pocket, a temporary cover upon the lined pit for placing the interior thereof in communication with the high head opening of the exterior furnace wall, said cover being adapted for excluding outside air, except when removed to enable accumulated slag to be lifted together with the lining as ceiving slag carried over from the melting area with the gases of combustion of the furnace, said main slag chamber including a floor and an exterior apertured wall a bodily displaceable auxiliary slag pocket disposed outside the limits of the Iurnace and adjacent to the outer face of said exterior apertured wall, and below the floor .level 01 the main slag chamber, the bodily displaceable auxiliary slag pocket communicating with the main slag chamber through the aperture 01' the exterior wall, the height of said aperture being greatly in excess of the height necessary to accommodate the slag flow therethrough, thereby to insure copious circulation of the intense heat of the main slag chamber into and from the aux- 10 iliary slag pocket for the purposes described.

- IRVIN C. JOHNSTON.

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