US1576883A - Process of making graphite - Google Patents

Description

` Ill. is i v... R A

V M WEAVER PROCESS OF MAKING GRAPHITE Filed March 2, 1923 March 16 1926.

TIG'. 1

Quan/Wto@ Patented Mar. 16, 1926.

PATENT OFFICE.

VICTOR M. WEAVER, F HARRISBURG, PENNSYLVANIA.

PROCESS OF MAKING GRAPHITE.

Application led March 2, 1923. Serial No. 622,298.

To all lwko-m t may concern Be it known that I, VICTOR M. WEAVER, a citizen of the United States, and a` resident of Harrisburg, county of Dauphin, State of Pennsylvania, have invented acertain new and useful Improvement in Processes of Making Graphite, of which the following is a full, clear, and exact description, reference being had to the accompanying'drawings. p

This invention relates to the art of manufacturingv relatively dense or crystalline forms of carbon from carbonaceous material. More particularly it has for its object the manufacture of graphite and especially dense forms thereof. y

An object of this invention is to makev graphite slabs suitable for electrodes which are of uniform, relatively dense, homogeneous character and which will be suitable for use in the electrochemical or other arts wherever such characteristics are desirable. A further object of this invention is to produce such graphite in relatively large quantities and in a relatively cheap manner and of a predetermined form so that it can be used, if desired, as an electrode Without additional cutting andvshaping.

Another object ofthe invention is to pro- .30 duce graphite without the use of the customary pitch binder or the like, which in heating volatilizes and causes the electrode to become relatively porous. .e A further object of this invention is to virtually cast carbonaceous material into graphitic slabs or ingots by the. use of a flux capable of iowing the materlal and of being broken down to leave graphite.

Another object of my invention is to pro- 4 duce graphite shapes or slabs which can be mechanically pressed -or worked while the slab is hot to force the particles relatively close .together and thereby roduce a more dense slab ofcrystalline car on.

According to the usual methods of manufacturing graphite slabs or electrodes the carbonaceous material is first calcined and then ground and pulverized. This ulverized material is then mixed with a inder,

such as a itch binder. This material is then presse for extruded into the desired shapes and heated usually in an electric furnace. Toobtain'graphite the tem erature must be relativelyv much' higher t an for the so-called carbon electrodes. Durin the final baking a relatively large part o the binder is volatilized and driven oil' and this naturally leaves the electrode more or less porous. Thus it will be seen that the shaping and manufacture of carbon or graphite electrodes hasbeen analogous, generally, to the methods of operation in the ceramic industry. That is, carbon Ahas been treated as an infusible substance and all of the working of the material and the application of pressure in the forming steps is performed before the material is finally baked. As distinguishedffrom these methods of operation and the analogy to ceramics, I have made observations which show that carbonaceous material, such as graphite, can be treated in a manner analogous to metals, and b such treatment can be made, worked, and ormed to produce relatively cheaply uniform, relatively dense, homogenous, slabs or ingots of graphite. I have observed that at relatively high heats carbonaceous material is' somewhat plastic and that under certain conditions and With certain fluxes such material can be transformed into aphite and can be made to iow. Accorin to my process, therefore, I select a iux W ich has the property of transforming carbonaceous material into graphite and which will flow at relatively hightemperatures in the presence of graphite and which finally u on reaching a. higher-temperature Will break up into volatile matter leaving graphite. The volatile matter ycombines with the carbonaceous material above, forming more of the iux. Such a flux, for exam le, lis calcium carbide.V This iux has tlie ro erty of becoming relatively thin and iipuid at high temperatures with graphite present, and upon further heating the calcium will be volatilized, leaving the carbon previously combined in thecalcium carbide as graphite. The volatile calcium driven off by this reaction combines with more of the carbonaceous material to form more calcium carbide. These reactions continue progressiveyly until all of the carbonaceous material is transformed into graphite. By utilizing the properties of calcium carbide or an equivalent flux 'which becomes relatively thin and fluid at high temperatures, I am enabled to. flow the carbonaceous material the previous slabs of graphite more densev than they would be if simply allowed to cool after formation according to the process herein described. This is accomplished by working or pressing Vthe graphite sla-b While it is suiliciently hot to be somewhat soft and plastic, that is, while it is above a red heat. It may be done by transferring the slab from the electric furnace in which it is formed to a mold of suitable material and exertin a pressure as with a plunger of a press or a very short period of time and then removing the slab from the mold. Or the furnace itself, if suitably designed, may be used as the die to'hold the ingot during the application of pressure. Under certain conditions, if the pressing be done relatively quickly, metal dies, preferably lined with a suitable protective coating of refractory material, may be used, as the heat received by them would be conducted through the relatively largel mass of metal sufficiently rapidly to prevent the destruction of the die before the graphite slab can be pressed and removed from the die.

By subjecting these'graphite slabs to this temperature and pressure treatment, the density of the carbonaceous material can be raised very materially and in fact it seems that vunder proper conditions the density can be raised to 3.5, or that of the diamond.

In the accompanying drawing wherein I have shown for illustrative purposes an electric furnace for carrying out my process,

Figure 1 is a longitudinal sectional view through the furnace.

F ig. 2 is a transverse section through the furnace.

In carrying out my process I use a troughshaped furnace l, having retaining walls of any suitable material, preferably iron. The bottom and side walls of the furnace are lined with a suitable heat insulator 3, such as powdered carbon or graphite, lpreferably lamp black. Resting on this ming are slabs of carbon 2, forming the bottom of the inside of the furnace.

A vertically movable frame 4 rests on the carbon floor 2 around its periphery until thefurnace has been charged and is ready for operation. Beforethe furnace is started theV frame is raised slightly above the floor and isA gradually moved upwardly as the ingot forms. The carbonaceous material from the charge constantly falls between the y intact, insures that the ingot will be of the t shape desired. Under certain conditions, if desired, the walls 4 may be of carbon and left in place during the heating.

Any number of electrodes 5 suitable to heat the contents of the furnace may be used. These electrodes are preferably lo-` cated so as to draw arcs from the surface of the bottom 2 of the furnace proper to heat the material in the furnace. These electrodes may be raised in any well known manner (diagrammatic means only being indicated in the drawing) as the material in the furnace becomes fused. The powdered or broken carbonaceous material 3 may be covered with any suitable material 6, such as lime dust, to exclude the air therefrom. I charge the floor ofthe furnace with limo, preferably pure calcium oxide and carbonaceous material, the charge as a whole being designated by numeral 7, the latter preferably being petroleum coke because it leaves substantially no ash. A substantial excess of coke beyond that required to react with the lime to form calcium carbide is used, and this material is placed on top of the charge on the furnace floor, filling the furnace as high as is desirable. When the ;l arcs are struck, the temperature rises and calcium carbide forms and flows over the bottom 2 of the furnace, for calcium carbide is relatively thin at high temperatures.

This fusion of the calcium carbide will tend to dissolve additional carbon.

As the temperature is raised the carbide at the bottom of the furnace is broken up,

the calcium rising and perhaps forming more carbide with the carbonaceous niaterial above, thus melting and fusing and perhaps dissolving more carbon until the reaction has worked progressively and entirely throughout the contents of the fur nace. tcrial lias either been formed in the carbide or dissolved by the carbide and after the calcium has been driven off, the remaining slab or ingot is one of relatively dense graphite.

It will thus be seen that the reaction is carried out in zones progressively upward in the furnace, the graphite slab beingtlie hottest zone and above it a layer of carbide becoming rich in graphite. Above this, the calcium vapor, driven off from the hot carbide reacts with carbonaceous material forming new carbide. The charge above these zones is heated by the ascending yvapors and heat from ythe reactions below.

After all of the carbonaceous inasame rate as the electrodes, so that it is not in the hottest zone. As the ingot forms upon the bottomv 2 of the furnace, it is retained by the powdered carbon side walls 3 and this is advantageous as will appear hereinafter.

For some purposes a highly dense graphite is desirable and according to my process the density of the ingot so produced in the electric furnace may be increased due to its having property similar to iron or other metals in that. it can be mechanically worked to increase its specific gravity.

The design of furnace herein disclosed is well adapted for cases when it is desired to compress the hot ingot. This may be done by transferring the entire furnace into a die and placing it in a press, or if the furnace wall andpacking be strong enough for the pressure desired, it can be used as the die itself and the pressure can be exerted directly upon the ingot from above.

It will thus be noticed that with the furnace herein disclosed the retaining receptacle not only supports the lining and heat insulating material 3 but also excludes the air therefrom. Also the gases evolvingr from the reaction pass upwardly through the charge and not through the lining material.

Furthermore, it is to be understood that the particular forms of apparatus shown and described, and the particular procedure set forth are presented for purposes of eX- planation and illustration and that various modifications of said apparatus and procedure can be made Without departing from my invention as defined in the appended claims.

Vhat I claim is:

1. The process of making graphite which consists in heating lime and carbonaceous material in a suitable furnace, whereby a fluid carbide is formed, and continuing the heating until the carbonaceous material has been transformed into graphite and the calcium volatilized.

2. The process of making relatively dense graphite ingots which consists in placing carbonaceous material and a relatively small quantity of lime in a suitable furnace and heating until the carbonaceous material has been transformed in the presence of calcium to a relatively dense quality of graphite and the calcium volatilized.

3. The process of making relativelyE dense shapes of graphite which consists in heating in a suitable container of predetermined shape carbonaceous material and a fiux capable of .flowing the material and of breaking down upon continued heating into volatile matter and graphite.

4. The process of making relatively dense 2ll Vshapes of graphite which consists in heating in. a suitable container of predetermined shape a 4@relatively large quantity of cargraphite bonaceous material and a relatively small quantity of material capable of combining with the carbonaceous material to flow it and upon continued heating capable of breaking down into volatile material and graphite.

5. The process of making relatively dense graphite ingots which consists in heating in an electric yfurnace a relatively large quantity of carbonaceous material and a relatively small quantity of lime until calcium carbide is formed and continuing the heating until all the calcium carbide is broken down into "olatile material and graphite.

6. The process of making relatively dense ingots of graphite which consists in heating in an electric furnace a relatively large quantity of carbonaceous material and a relatively small quantity of lime until calcium carbide is formed and continuing the heat ing While the calcium is progressively volatilized, forming more carbide With the remaining carbonaceous material until the calcium is driven off leaving a relatively dense quantity of graphite.

7. The process of forming sha-pes of relatively dense graphite Which consists in mechanically Working relatively hot graphite.

8. The process offorming shapes of relatively dense graphite Which consists in pressing relatively hot graphite in a die.

9. The process of forming relatively dense shapes of graphite which consists in mechanically Working graphite while it is suilciently hot to be plastic.

10. The process of making relatively dense shapes of graphite which consists in heating carbonaceous material with lime in an electric furnace until the calcium is volatilized, removing the graphite ingot and mechanically working it to increase its density.

11. The process of forming relatively dense shapes of graphite which consists in heating in an electric furnace carbonaceous material and a fiux in a container of predetermined shape until the flux is volatilized, leaving a soft, hot graphite ingot, and mechanically pressing such ingot to increase its density and homogeneity.

12. The rocess of making relatively dense graphite shapes which consists in heating in an electric furnace carbonaceous material and lime until a relatively dense homogeneous ingot of graphite is produced, and mechanically working such ingot under pressure while it is hot and soft to produce a more dense and homogeneous shape of graphite.

13. The process of making relatively dense predetermined shapes of graphlte which consists in heating in an electric furnace carbonaceous material and lime in a container of predetermined shape until a relatively dense homogeneous ingot of is roduced and mechanically Working such lngot under pressure while it is hot and soft to roduce a predetermined shape of graphite iaving increased density and homogeneity.

14. The process of increasing the density of graphite which consists in compressing s relatively soft hot graphite.

15. The process of increasing the density of a slab of graphite which consists in heating such slab until it becomes relatively soft and compressing it.

y16. The process of increasing the density and ho1nogeneity of vraphite which'consists in heating it until .it becomes plastic and applying a relatively great pressure thereto.

17. The process of increasing the density of carbonaceous material which consists in heating such material until it becomes soft and applying a relatively great pressure thereto. f

18. The process of increasinv the density of carbonaceous material whic consists in heating such material in an electric furnace until itbecomes plastic and applying a relatively high pressure thereto While it is conned in a relatively strong container. v19. The process of increasing the density of carbon which consists in heating it above a red heat and applying a pressure upon it while it is above a red heat. Y

20. The processof making graphite ingots which consists in forming a mold of relatively line carbonaceous material and heating the carbonaceous material with a flux therein by means of an electric are,

blackv of predeter- 22. An electric furnace for reacting on l carbonaceous material comprising a retaining member, a lining of re atively fine carbonaceous material, a vertically movable frame to engage the sides to receive the charge and vertically movable electrodes inside said` frame vto draw arcs from the bottom of the furnace.

-23. An electric furnace construction com-v prising a trough-shaped 'retaining member,

of the lining and,

a lininr for the sides and bottom of rela-- tively fine carbonaceous material, a floor of carbon slabs upon the bottom of said lining 'i a movable frame engaging the sides of said lining, and superposed above said floor, said frame and licor forming a receptacle for the charge, and electrodes for drawing arcs through a portion of the charge.

In testimony whereof, I hereunto ailix my signature.

VICTOR M. WVEAVER.

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