US2330751A - Reduction apparatus - Google Patents

Description

Sept. 218, 1943. F. G. SHAUB ET 'AL 2,330,751

REDUCTION :'PPARATUS Filed July 24, 1941 i' I m Patented Sept. 28., 1943 REDUCTION APPARATUS 'Frank G. shaun, Detroit, Imbert A. McCloud,

Dearborn,

and Burton E. Tiffany,

Detroit,

Mich., assignorsv to Ford Motor Company, Dearborn, Mich., a corporation of Delaware lApplication July Z4, 1941, Serial No. 403,835

v 9 Claims. This invention relates to reduction apparatus;

' and, more particularly, to an electric furnace and associated condensing device intendedl for use in the reduction of magnesium and similar metals.

While particular reference will be made in this specification to the use of this furnace in the reduction of magnesium, it will -be understood that it is equally available for-the reduction of lother metals which present similar problems. The difilculties incident tol the production of metallic magnesium from available magnesium compounds have been exhaustively studied; but, as yet, no safe, economical and large-scale process is available.

The particular difliculty, of course, in obtaining the metallic magnesium, arises from the ease with which this metal oxidiz'es. Moreover, this oxidation may be accompanied with some violence.

specification, claimed in our claims, and illustrated in the accompanying drawing, in which:

Figure 1 is an elevation of the furnace and cone assembly, parts thereof being shown in section.

Figure 2 is a sectional elevation on an enlarged scale, showing a portion of the furnace and cone when in operating position.

Figure 3 is a sectional elevation through the electrode holder.

Figure 4 is a diagrammatic sketch showing the several positions of the furnace and cone.

Referring now to Figure 1, the furnace I and cone (I` of this invention are shown in their operating position. The furnace is substantially in the form of a Vertical cylinder having an outer shell I2, a series of layers of insulating material The -two principal methods of obtaining metallic magnesium employ either electrolysis or the condensation of magnesium vapor. In the first, the metal is formed in lumps in a molten bath and is prevented from oxidizing by a slag covering. In the latter, the condensed magnesium is in the form of an impalpable powder in which p state it is particularly susceptible to rapid' and violent oxidation and great care must be taken to prevent this.

The furnace which we have devised is intended to be used in the carbon reduction of magnesium oxide. In this process, suitable quantities of magnesium oxide and finely-divided carbon are intimately mixed and subjected to the heat of an electric furnace.

and the temperature is such that the reduced magnesium in the furnace is in the form of a gas. This gas is then withdrawn .from the furnace to a suitable condensing device, in which the gas is condensed in the form of the powder previously described. The principal mechanical requirements of this process are: first, a suitable heat source; second, that no oxygen be admitted to either the furnace or the condensing device; and third, that the metallic magnesium dust be so treated as to permit its safe handling.

Other requirements are that there be a suitable means of charging the furnace, that the interior of the furnace be available for cleaning and inspection, and that suitable means be provided for cleaning out the condensing chamber.

With these and other objects in view, our invention consists in the larrangements, construction and'combination of the various parts'of our improved furnace construction, described in the The reaction between the carp bon and the magnesium oxide reduces the latter I3, an upper stack block I4 defining the stack I5,

a chamber block I6 defining the chamber Il, and

the hearth block I8 having a central charging well IS. Blocks I4, I6 and I8 are preferably formed from carbon, as being least reactive among available refractories. The furnace is supported on a base plate 20, which also supports the charging mechanism indicated generally as 2l. The base plate is also provided with wheels 22 which run on the rails 23, these rails being arranged to form an arcuate track as best shown in Figure 4. A number of overlapping and interlocking floor plates 24 are provided on each side of the `furnace and operated thereby. The purpose of this construction is to permit the furnace to be moved away from the cone, the latter being flxedly mounted. This permits ready access to the interiors of both the cone and the furnace and the cleaning or repair thereof. The rails 23 are mounted on the floor 25 at the operating level. This floor is cut away to form a slot 26, through which the charging mechanism 2| extends. This arrangement permits the furnace to l be readily accessible from the Working elevation,

while the charging mechanism, which does not require careful supervision or control, is situated below that level.v The floor plates 24 referred to, are provided on each side of the furnace and cover the slot 26 yregardless of the position the furnace may occupy.

Thus, in Figure 4 where the furnace is shown in full line entirely removed from the cone, the innow piled together, while those at the rear side of the furnace are extended to cover the slot. In Figure 4, this latter position is shown by the dotted outline.

The furnace of this invention is of the singlepliase electric type, having an electrode 2l eX- tending through the stack i5 to the chamber il and supported by an electrode holder 28. Associated with this is a conventional electrode feeding device not shown in detail by which the arc between the electrode and the other element is automatically maintained. The electrode holder, which is shown on an enlarged scale in Figure 3, is water jacketed to cool the electrode as by the passages 2d. The holder is made of copper and the water chambers therein are remote from the electrode to prevent leakage of water into the furnace. In addition to providing the usual packing i3@ to prevent leakage, a nitrogen stream is introduced above the electrode which tends to raise the pressure within the furnace above atmospheric and prevent leakage along the electrode. This stream is introduced through a channel 3| through the electrode holder into the central well thereof. This channel communicates `with a bushing -l whose inner surface engages the electrode and whose outer surface is provided with a circumferential channel 33. A plurality of holes 3S leads from the channel to the interior of the bushing and permitsthe nitrogen to be discharged and distributed around the outer surface of the electrode. This nitrogen being forced into the furnace prevents the accumulation of magnesium in a gaseous form in the upper part of the stack and forces it downwardly to where it may be removed from the furnace. This is important, since otherwise the magnesium would tend to condense in the upper part of the furnace on the walls thereof, destroy the arc and prevent operation of the furnace.

Material to be treated is fed from beneath the furnace through the hearth block i3. This block is in the form of a frustum of a cone and is surrounded by a steel jacket 35, which is bolted to the base plate Ztl. The forces exerted by the material when it is pushed up through the hearth block are considerable, and this means is used to prevent dislocation of the hearth block thereby. Communicating with the lower end of the hearth block is a steel ring' 36 which, in turn, communicates with the chamber 37 of a vertical ram 3B. This chamber is intersected by the chamber 39 of a horizontal ram du. The chamber of the horizontal ram is, in turn, intersected by a conveyor pipe (il, into which the raw material to be fed to the furnace may be introduced.

As will be noted from the drawing, the feeding system is tapered slightly, having an increasing diameter above the point at which the horizontal 'ram enters the Vertical ram. rlhis has been found necessary to prevent clogging of the material during the feeding operation. Each of the rams is operated by a suitable hydraulic cylinder as indicated at 32. This type of construction is particularly desirable since it is entirely supported by the furnace and may move with thefurnace when it is desired to have access tc the interior thereof or to the cone.

The material to be charged is placed in thi conveyor pipe ill, from which it is introduced into the chamber of the'horizontal ram. This ram forces it into the chamber of the vertical ram, compressing it inthe process and causing much of the air therein to be removed by leaking past the head of the ram. The vertical ram is then operated and the material which has been discharged into its chamber is further compressed and substantially all of the remaining air is forced from it, while the material is so compacted as to have adequate electrical conductivity.

The feed of the ram is interlocked with the power input to the electrode so that the material is fed at a proper rate. This is not shown, but it makes use of any conventional electrical hookup. The material is then forced upwardly through the charging well in the hearth block until it reaches the approximate level of the bottom of the chamber Il. The hearth block, chamber block and stack block are all made of carbon and the hearth block acts as the other i electrodes of the single-phase furnace, electrical connection thereto being provided through the bolt 43 to a bus bar '34 to make the other electrical connection. The arc of the furnace is then between the electrode 2l and the hearth block I8 and the compacted charge therein. As the charge to be acted upon isconned Within the hearth block, there is no opportunity forv it to escape or to avoid the operation of the arc.

The heat of the arc is suflicient to cause the required chemical reaction between the magnesium oxide and the carbon and, as a result, gaseous magnesium and carbon monoxide are formed. In addition to these, the nitrogen gas introduced through the electrode holder is also present. These gaseous materials blow through the tap hole l5 to the cone Il. The cone, as best shown in Figure 1, comprises the front portion 46, which is substantially in the shape of a frustum of a cone, and a back portion il which is substantially in the form of a horizontal cylinder, having on its upper side an explosion diaphragm 68 and at its lower side a sump t9. 'The front portion is provided with a cooling jacket 50, through which oil maybe circulated. It is also equipped with a plurality of jets 5l, one such being shown. These jets are preferably made in concentric tubes, the inner tube 52 being for the passage o f quenching oil and having a nozzle 53 at its inner end. The outer tube 56 is intendedfor the supply of nitrogen to the interior of the cone when that is required during the operation.

This arrangement is preferred as the inner` tube is made removable so the nozzle may be cleaned, and when this is done, nitrogen may be introduced through the outer tube to prevent any leakage of air into the cone. The front end of the cone, as best shown in Figure 2, is formed with a plate 55, which is so shaped that it abuts against the furnace plate 56, the latter being made preferably of* stainless steel. The cone plate has a central aperture which has a slight inwardly extending circumferential flare. Cooperating with this is a seal member 5l, which may be forced into contact with the cone plate and bearing on the are thereon, eiiectively prevents the entrance of any gases into the interior of the cone when the latter is not in contact with the furnace. This seal member is carried on a hollow shaft 58 and is externally operated by a handle 59. This hollow shaft, in turn, encloses the shaft 60, which has at its forward endv a reamer 6l, and which may be operated externally by the handle 62. The purpose of this mechanism, which may be forced into the tap hole of the furnace, is to clean the latter without the necessity of removing the cone from the furnace. Mounted on the exterior of the seal shaft is a cone.

scraper shaft 63 which has extending arms 64 and scraper blades 65 attached thereto. These blades scrape the interior of the cones surface and loosen any material deposited thereon, particularly the slag formed in the furnace and deposited in the cone. This assembly of shafts is journaled as at 66 and the outer or scraper shaft is preferably driven through a chain and sprocket arrangement 61 by an external motor 68.

As we stated previously, `the gaseous magnesium, the carbon monoxide, and the nitrogen flow from the furnace to the interior of the The joints between the cone and the furnace may be made sufficiently tight by the application of a little clay, and as the pressures in both of the units are somewhat above atmospheric, there is no tendency for any leak of air inward to occur.

A constant spray of highly atomized oil particles is maintained in the interior of the cone through the nozzle-53. This spray is very violent and is directed somewhat' inwardly from each of the nozzles surrounding the cone, this direction being indicated by the lines 69. This quenching oil which is recirculated, condenses the gaseous magnesium to the form of a powder and the powder suspended in oil is deposited on the walls of the cone. Magnesium powder, when moistened in oil, will not `oxidize and there is no tendency to explode. The deposited matter on the walls of the cone is scraped therefrom by the scraper and fallsinto the sump 49, from which it is removed by a screw conveyor, not shown here, for further treatment. This conveyor line also includes a suitable trap to prevent the access of air to the interior of the cone. The operation of the furnace and cone should now be apparent. To recapitulate briefly, the material in the charge is fed to the interior of the furnace through the bottom thereof and through one of the electrodes' making the electrical circuit. It is then constrained in place by this electrode while an arc is set up between the constraining electrode and the material and a conventional 'central electrode. The heat of the arc is sufficient to fuse the magnesia and to cause the necessary chemical reaction; and the products thereof pass from the furnace, the interior of which is maintained at a temperature. slightly above atmospheric, to a condensing cone. During this step, a small pool of fused magnesia forms on the surface of the charge. The gases are then condensed by a violent spray of oil partcles and the condensed magnesium metal sus-- pended in the oil proceeds to a sump in the cone `from which they, together with such gases as are formed during the process as Well as the introduced nitrogen gas, are removed for'further s eparation and treatment. The quenching oil includes a small quantity of previously condensed( magnesium which serves as nuclei for the condensation of the gas. The furnace indentation permits the zone of the arc and the quenching zone to be closely adjacent, a feature we believe to be essential for the best yield.

It is recognized that the reduction process of y making magnesium has been practiced before` and that quenching of the gaseous magnesium, by one method or another, has also been practiced. However, the applicants have made a careful and exhaustive study and are unable to determine that the reduction process has ever ity of the cone and furnace, as an example, permit an unusual flexibility in the operation of the plant, Heretofore, the cone and the furnace have been made as a unit and whenV any repair or inspection was necessary, a number of connections and controls had to be removed and disconnected. In this device, when it is desired to obtain access to either the interior of the furnacev or the cone, it is only necessary to seal the cone by the sealing device disclosed, and move the furnace bodily away from the cone. During this time, the electric arc may be maintained and the feed of material for the furnace is uninterrupted. The entire furnace, as a. unit, is selfcontained in the sense that' it may be moved about as desired and still be operated throughou l A particular advantage of thisv apparatus is found in the method of charging. The materials compression and leaks past the heads of the rams.

In addition, by utilizing the hearth block togetherwith the charge as one of the electrodes and leading the material up through it, the material is maintained in position where it may be acted upon with the greatest efficiency by the electric arc. The arc is concentrated on the surface of the material to be worked upon and, as a result, there is no scattering or dispersal thereof nor is the material allowed to accumulate in parts in the furnace where it is not acted upon by the arc. The hearth, when first used, will erode rather swiftly to form a basin-shaped depression in the vicinity of the well; Thereafter he trate of 1erosion lessens and an equilibrium om 1s reac ed with little furt of the hearth material. her detenoration By introducing a stream of nitrogen around the electrode, the electrode holder is not only rendered leakproof, insofar as the outer air is concerned, but magnesium vapors are forced downwardly in the stack and'do not have an opportunity to condense therein. This lis particularly important, as is the relation of the stacks diameter to the diameter of the electrode insofar as preventing such condensation therein. If this condensation were allowed, the eciency of the furnace would seriously decrease.4 We find that a suitableratio is one which gives sufficient velocity to the gas stream; and in the case of a 4 electrode, an 8" stack is adequate.

The construction shown has particular advantages in connection with the furnace used. The

seal mechanism by which the interior of the cone may be shut off prior to its being moved away from the furnace is novel. By use of this seal, the furnace and the cone may be separated and the atmosphere in the cone prevented from deteriorating. The concentric arrangement of the nitrogen pipe and the oil jet likewise has the advantage of permitting the replacement and feeding of the jet without adversely affecting the atmosphere in the cone.

The particular jet nozzle used, i. e., one which directs the oil inwardly, has been found to be particularly advantageous as a 'quenching medium. The spray therefrom is highly atomized and veryviolent and it has been found that a larger proportion of the magnesium is quenched when a spray of this character and direction is used than with any other means available.

While, as stated above, the general technique to be followed inthe reduction of magnesium metal is a matter of common knowledge, to date practical applications of this knowledge have not been evident. The requirements to be met in a successful apparatus are many and the deficiency in any one detail may totally prevent formation of the metallic magnesium. The applicants have devoted considerable time and study to the problem and in the apparatus shown have arrived at a means by which metallic magnesium may be made on a-Commercial basis by the reduction process with eiciency, economy and, abovel all, safety. They have, moreover, by the use of the4 single-phase furnace, the compression feed thereto, the use of a combined electrode and hearth* block, and a furnace which is movably mounted with respect to a condensing cone, achieved av flexible vand workable unit. In addition, the sealing means shown for the cone and the oil spray means used therewith remove many of the dimculties hitherto encountered in the condensation apparatus.v This furnace, while shown with an oil quench, may also be used with ,other quenching means such as gas, molten lead, etc.

Some changesmay be made in the arrangement, construction and combination of the various parts of our improved construction without departing from the spirit of our invention, and it is our intention to cover by our claims such changes as may reasonably be included within the scopethereof.-

We claim as our invention:

l. In combination in a reduction apparatus, comprising, an electric furnace, a condensing cone, said furnace and said cone abuttingT each other in one position andzhaving a scalable connection therebetween, a support having a slot therein, said cone securedto said support, charging means secured to said furnace and extending through said slot in said support, and means on said support movably supporting said furnace, whereby said furnace and said charging means may be removed from said condenser to permit access to the interiorl of said furnace, and sealing means on said cone.

2. In combination, in a single-phase electric furnace, comprising, a chamber, a hearth block, a charging well extending from said chamber downwardly through said hearth block, means by which the materials to be treated therein may be forced through said charging well,` an electrode adjustably secured in said chamber, said hearth bleek and the material therein serving as another electrode to complete an arc, and means communicating with said charging well to compress the material prior to the charging thereof to free said material of air.

3. In combination, in a single-phase electric furnace, comprising a chamber, a hearth block, a charging well extending from said chamber through said hearth block, a rod electrode secured in said chamber above said charging well, said 'hearth block serving as another electrode to complete an arc therewith', acharging ram substantially aligned and connected with said charging well, a second charging ram leading into said charging well between said rst ram and said hearth block, said second ram being oblique to said rst ram and means to admit charge material to said second ram.

4. In combination, in an electric furnace, comhearth block and secured to said base plate, a

charging mechanism secured to said base plate and communicating with said charging Well, an electrode support mounted on said furnace and including means for cooling an electrode supported thereby, and an electrode extending from said supporting means into said chamber.

5. In combination, in a metal reduction system, comprising, a single phase electric furnace, a hearth block, a charging well extending upwardly through said hearth block to a, chamber,

means at the other end of said well to compress.

the material to be fed to said furnace and to force said material upwardly in said well whereby the air is removed from said material and the particles thereof are brought into intimate contact, an adjustable electrode in said chamber, electrical connection to said electrode and said material said electrode adapted to act with compacted material of the charge to form an electrical arc therebetween, and means to force the reaction products of the material under said arc from said furnace.

6. In combination, in a reduction apparatus, comprising, an electric furnace, a port therein, a

rhorizontal supporting means therefor, an arcuate slot formed in said supporting means, guide means associated with said slot, means on said furnace to co-operate with said guide means whereby said furnace may be translated in an.

arcuate path, and charging means secured to said furnace and extendingtherefrom through said slot.

7. In combination, a single-phase electric furnace, comprising, a chamber, a stack of reduced cross section extending upwardly from said chamber, a hearth block defining a horizontal floor for said chamber, a charging well extending through said hearth block into said chamber, a movable electrode mounted in said'stack and extending through said chamber and substantially aligned with said charging well, a discharge port through the wall of said furnace communicating with said chamber, the area of said port being'small as Acompared with the horizontal. cross section of said chamber, the lower line of said port being spaced a substantial distance above the floor of said chamber, and an electrical connection of said hearth block 'whereby said hearth mock comprises another electrode to complete an arc therein.

8. In combination, a single-phase `electric furnace, comprising, a chamber, a stack extending from said chamber, a hearth block of electrically conductive and refractory material forming the floor of said chambena charging well extending through said hearth block opposite said stack tol said chamber, an electrode adjustably mounted in said stack and substantially aligned with said charging well, electrical connections in said electrode and said hearth block to complete an arc therethrough, and a discharge port in said chamber spaced a substantial distance above said oor, the cross-sectional area of said port being small as compared to the horizontal cross section of said chamber.

9. In combination, in a magnesium-reduction system, comprising, a furnace, a chamber in said furnace, a port communicating between said chamber and the exterior `of said furnace, a

carbon hearth block below said chamber, a charging well extending from said chamber through said hearth block, a feed mechanism communicating with said charging well and adapted to force charged material therethrough, lan electrical connection to said hearth block, an electrode adjustabiy mounted in said chamber, an electrical connection to said electrode, said feed mechanism including means to compact the charge prior to its delivery to said charging well.

FRANK G. SHAUB. ROBERT A. McCLOUD. BURTON E. TIFFANY.

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