US2634009A - Charging electric furnace - Google Patents

Description

April 7, 1953 F. WEITZENKORN CHARGING ELECTRIC FURNACE Filed July 25, 1945 INVENTOR. LEE WE ITZENKORN HIS ATTORNEY Patented Apr. 7, 1953 UNITED STATES" PATENT O FF'I CE CHARGINGELECTRIC-FURNACE Lee Erank W eitzenkorn, Dnndalk, assig s},

by niesn assignments, to Armco Steel corps ration, a cor oration of Ohio ApplicationJuly 23, 1945, :Serial 7N0; $06,555

1 claim. (01. 214 452") l invention relates to electric arc furnacepractice; and more-particularly;concernsanov'el mode oi' introducingitherein' the chrome-:ore-"or' similar ore-which is to be subsequently: processed andreduced.

An objectof my invention is to provide a-n'ew' and f novel method of introducing; chrome ore" into an electric arcfurnace in such manner that the ore is distributed gently and with a natural angleof repose-about the banks' of thefurnace.

. Another object istorprovide amethod of thegeneral type of the -foregoing,"wherein chrome or at any desired point. ore can-be quickly and readily supplied to those points within'the furnace-"where the layer of ore; momentarily appears to bethin.

Still another object I is: to provide a method of the general type described wherein all tend ency oftheoreto clog. in :the delivery-process is effectively eliminated, the ore" falling: gently: onzthe- -banks of the furnace-,1 and all danger is effectively eliminated of delivery at toogreat a--ve1ocity or' with too great a force so 'a's-to dislodge the deposited :orei- Surging? and jamming" no longer constitute a problem,- and the" rate-of; feed :from the hopper: and thevelocity with which the: ore is depositedboth are sub ject to i-full and sensitive control, hand-shovelling being effectively? avoided."

Otheri objects :and advantages will in part be obvious and in part pointed out hereinafterduring the course 1 of: the following" description:

, My invention accordingly resides in'theseveral 40 various combinations of each of -'the=same with one or more of the others; the-scope of 3 the procedural and' manipulative' steps and in the.

applicationiof'j all of which is more fully! set forth in' theclaim at the end of-this specification.

In the- 'drawing's, whereinIdi'sclose" one em-' bodiment of'my invention which I- prefer at present of equipment facilitating the practice or myvnew invention, Figs; 1 and: 2 respectively illustrate apparatus for practicing-:my invention; and the laying of ore onto the banks-f an electric arc furnace in accordancetherewitht As conducive tea-more thorough and complete" unclerstanding of my new invention; it may be noted; i that in therp-ast three? or four decades;

the use of the electric arc furnace has come into point of fact, this patchingg i as is calledthe greater and greater acceptanc in- :the processing; of: irons, steels-and other heavy metals. Despite the substantial operationalexpense of these furnaces as compared with the coke-fired open-,= hearth-furnace and the Bessemer, and despite the, comparativelysmall capacityof electricunits; the high temperatures required the melting: ofhigh alloy steels and other specialized alloy metals have dictated the'use-of such equipment in producing-such steelsn The" widespread expansion' of this type, of metal processing-qhas" resultedin the rapid refinement and development ofthej furnace equipmentitself. At the present time, therefore, the electric furnace has reached a' high state of development: Contamination of the-heat undergoing processing) is reduced'toa minimum. Products of high purity and accurateanalysis areobtained and operational times'are reducedto' a'minimum, while unit capacity has been increased. Operating in batteries 0f'two,-four, six or more fur-Q.

naces substantial operational, efliciencies are: achieved, limited almost entirely by unit power costs.

Holding step" with the development of: the electric arc-furnace if not exceeding it; is the evolution of 'whatare known as stainless steels,

by'which of course is meant the-now'well-knowni chromium alloy steels-which are so'widelyi'used in all walks of industrial, commercial and resi-' dential use; The utilization of such metalsof varying percentage composition runs'the entire gamut from armor plate to lamp reflectors; ornamental bric-a-brac, cooking utensils and: 'the'like; 'Iheevolution-of such steels and -the widening demand therefor, both as to quantity and as to extent of utilizationyhas in itself T spurred 1 the development of the :electric' furnace; This is' 'because a high degree of 'purity' is'required with close adherence to the percentage composition :sought. For these reasons, the use of the: basic oracid open hearth" methods of processing as heretofore: known have proved entirely unsatisfactory in the production" of stainless steel. By processes of evolution',1to-

gether with selective'elimination over aperiod ofyearsthe production ofchromium metals has been almost entirely limited to electric:furnace equipment.=

Now, invelectric furnace practice, 'it is customary to handch'arge: the ore l about "the walls or banks of thelfurnacei' This is' sl'ow andtime'- consuming, and lrequiresi a large lab'or gang? In distribution of chrome ore along the banks of the furnace, comprises a most expensive manipulation, due primarily to the labor costs involved, but also to the time consumed in processing a particular batch or charge into the furnace.

Although in many instances the electric furnace is employed essentially as a finishing furnace for processing stainless steels already partially treated in either the open hearth or acid process, the operators have always been most active in undertaking to reduce the costs of operation and to bring them more nearly in line with the operational costs of the methods and processes heretofore in use. In this way they argued, as has already been pointed out, that increased utilization could be achieved of the electric furnace products such as chrome steels and the like. In an attempt to reduce the labor costs, therefore, and to step up the operational time requirements, it has been suggested to blow the chrome ore into the furnace. For one reason or another, however, these expedients failed to give entirely satisfactory results. To illustrate, in many instances regulation'of the flow of the material was impractical. In the usual design of a pneumatic blower, comprising essentially an open hopper containing the ore and a siphon or venturi which conveyed the ore to the air holes and discharge pipes, it was found that the ore tended to clog either in the siphon or in the bottom portion of the hopper. At the best, it flowed in a very irregular pulsating stream. In one instance, the ore would surge forth in quantity, the air mixture being quite enriched therewith. The next moment the unit quantity delivered would be much decreased, and the air mixture would be practically devoid of ore. Moreover, the rate of delivery was likewise found to be pulsating, so that the ore could not be properly banked around the walls of the furnace.

An important object of my invention, therefore, is to avoid in substantial measure the many disadvantages and defects of the art as it existed prior to my invention and at the same time to provide a method rapid, time-saving, certain and precise in nature, for uniformly discharging and depositing chrome or similar pre-dried ore at the desired point of application with a gentle arc whereby the ore can be deposited in its natural angle of repose, in which all pulsation and irregularity in feed is avoided along with all tendency of clogging and tendency for the deposited ore to be blown away from its point of deposition, and as well, to supply the ore at controlled unit volume and at controlled unit velocity.

Basically, my invention comprises discharging a stream of hot pre-dried chrome or similar ore from the end of a flexible pipe in and about the walls or banks of an electric arc furnace. .A pneumatic blower is employed successfully operable with substantially any type of granular or powdery ore. Regulation of the discharge velocity and control of the quantity and direction of the ore stream makes it entirely feasible to place the ore in any desired spot within the furnace, and in any desired quantity, simply by turning the flexible hose in that direction.

In practice my invention may be stated as comprising placing the ore to be discharged in a tightly closed container, and equalizing the air pressure both above and below the ore. This prevents improper surging in the discharge line and moreover, prevents clogging and jamming of the ore which feeds into the discharge pipe. Inasmuch as the pressure of both the top and bottom of the chrome ore in the hopper is equalized, the ore flows by simple gravity feed. A suitable valve regulates the flow from the hopper. An air line serves to pick up the chrome ore passing through the regulator neck and forces it through a Venturi column, whereby the pressure component of the air is sacrificed in order to increase the velocity component thereof. The stream of air, carrying entrained ore with proper density of ore and proper velocity of discharge, is passed through a flexible metal hose whence it is spread into the furnace in desired manner.

It is important in the patching operation according to electric arc furnace practice that the chrome ore fall in a gentle arc sothat the stream of the ore may be placed at any point therein and at any quantity on the banks of the furnace, allowing the ore to pile against its banks in its natural angle of repose. Any appreciable variation of the angle of deposition from the natural angle of repose of the material would result in the deposited material breaking away from its anchorage and collapsing into the bed of the furnace. The flexible metal hose can be so manipulated through the door of the furnace and the rate of feed and velocity components so selected that these objectives can be accomplished in highly satisfactory and accurately predetermined manner.

To illustrate this more effectively, reference may now be had to the specific structure which I illustratively employ for the practice of my invention and which is shown in Fig. 1 of the drawings. Therein a hopper NJ for the chrome or similar powdery or granular ore is provided. This is generally cylindrical in form with an inverted truncated conical bottom H. A removable pressure cover I2 is hinged at [3 to the top of tank ll}, latch l4 being provided on the top periphery of the tank diametrically opposed to hinge l3, for securing the pressure cover i2 in place. At its lower part the inverted truncated bottom ll terminates in a delivery column 15, which opens into a channel I 6. This channel it is connected at its left end in the figure to a variable source of air not shown, a main air control valve I! being provided for further manipulative variation in the incoming air.

It has already been stated that it is an object of my invention along with the other component elements thereof resulting in the final new achievement, that the flow through the hopper H3 be entirely by gravity. In this manner, the surges which have heretofore resulted from air feed of the chrome or other ore are effectively avoided. It is for this reason, as well as to reduce in large measure the effect of the external atmosphere, that the removable pressure cover [2 is provided. This is substantially sealing in nature. The desired objective of gravity pressure within tank It is accomplished by equalizing the air pressure on both the top and bottom of the ore so that the latter falls of its own weight. This is accomplished by by-passing part of the air from conduit [6 before it reaches throat l5 up to the upper air-space l8 of the tank it, above the level of the chrome ore.

To this end a conduit [9 is provided leading from main conduit IE to the space l8. An air pressure gauge 2i) is provided for accurate determination of the pressure conditions maintaining in this line, while an air control valve 21 is provided in conduit I9 for accurate control and regulation of these pressure conditions. When portion 23 partly out of throat l and into the air column conduit [6, variation in the rate of flow cangbe accurately controlled. On the other hand, regulation of the main air valve I! will in turn accurately control the velocity with which the gravity-fed chrome ore is forced to the right in the conduit l6 beyond throat ii.

To increase effectively the velocity component of the air passing through conduit Hi, to-

. gether with the entrained and entrapped chrome ore, at the sacrifice of the pressure component thereof, 11 provide a Venturi column in con:v

duit Hi, to the right of the throat I5. A flexible metal hose 26, of strength sufiicient to withstand the rigors of extensive and heavy use, and con- 1 structed of materials capable of withstanding at least moderately prolonged exposure to the s'fub- I stantially elevated temperature within the furnace, is made fast to the free end of the venturi 25 at the righ in the single figure. This in turn; terminates in a discharge nozzle 21, somewhat in the form of an elongated wand and at the free thereonflin its natural angle of repose. He is readily l able to place the stream of ore at any point within the furnace. Simply by retaining the wand in a particular point for a suflicient length of time he can build up or patch the furnace at: that point to the desired thickness of chrome ore layer. By having a helper manipf ulating, the flow regulator 22, he can accurately control the unit quantity of chrome ore delivered" 1 from tank l0, while by manipulation of valve l7 the velocity of the stream can be readily controlled. Required gentle delivery consistent with the characteristics of the particular ore being charged is thus ensured. The helper can also make frequent observations of the pressure in the upper portion l8 of tank I!) by reading pressure gauge 20 and can make such compensatory adjustments as may be required through manipulationo'f control valve 2| in bypass l9. Removable pressure cover I2 may be released at latch l4 and swung back at any desired time to replenish the supply of chrome or other ore. Upon re- Q're flow is uniform and non-pulsating. All these "and many other highly desirable and practical results attend upon the practice of my new invention.

Many colorable variations and adaptations of my invention will readily occur to those skilled in the art once the broad aspects thereof are disclosed. Moreover, the skilled technicians in this field will readily evolve many modifications of the technique herein set P-fqrth. Accordingly, I intend that the foregoing disclosure be treated merely as illustrative, and not by way of limitation.

Iclaim:

The method of laying chrome ore onto and about the banks of an electric arc furnace in patching the same, comprising gravity feeding a constant controlled unit quantity of granular hot pro-dried chrome ore into a separately regulatable air stream by applyingthe pressure of said air stream back of the supply of hot pre-dried ore as well as at the point of the ore entering said stream, restricting the flow of said air stream wtih entrained hot pre-dried ore to limit the area of the stream and uniformly increase the velocity of the ore, passing the air column with hot predried ore addition into the furnace as a controllable stream, and discharging the stream of air with entrained hot pre-dried ore at various desired points and in desired 'quantities about the banks of the furnace. I 7

LEE FRANK WEITZENKORN.

REFERENCES orrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 634,775 Suderman et a1 Oct. 10, 1899 r 699,405 Newhouse May 6, 1902 747,396 Farnham Dec. 22, 1903 1,240,409 Black Sept. 18, 1917 1,363,610 Mowry et al. Dec. 28, 1920 1,433,302 Rothchild Oct. 24, 1922 1,529,219 Scha-ab Mar. 10, 1925 1,567,642 Harrison et al Dec. 29, 1925 1,655,585 Meyer Jan. 10, 1928 1,796,215 Peikert Mar. 10, 1931 1,837,070 Roth Dec. 15, 1931 1,970,405 Thomas Aug. 14, 1934 2,359,888 Barr Oct. 10, 1944

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