US2135630A - Method of producing ferromolybdenum - Google Patents

Description

Patented Nov. a, 1938 PATENT. OFFICE METHOD OF PRODUCING FEBRO- MOLYBDENUM John D. Sullivan and Dimitry N iconofl, Columbus,

Ohio, assignors, by mesne assignments, to Kennecott Copper Corporation; New York, N. Y., a corporation of New York No Drawing. Application October 15, 1937, Serial No. 169,234

12 Claims.

Our invention relates to a method of producing ferromolybdenum. It has to do, more particularly, with the production of ferromolybdenum from molybdenite, M052, concentrates containing appreciable amounts of copper.

Many of the cupriferous ores of the United States contain appreciable amounts of molybdenum in the form of the mineral molybdenite, MOSz. Molybdenum can be recovered from these ores by concentration processes but frequently a considerable amount of copper minerals is present in the molybdenite concentrates. This is especially true. if a high recovery of molybdenite is desired. The accompanying copper is usually in the form of sulphide which may, for example, be covellite, chalcocite,'bornite, chalcopyrlte, enargite, tetrahedrite, tennantite or other sulpho or sulphide mineral. .No definite limits can be given for the percentagcs'of molybdenite and copper in concentrates because these depend in part on the method of concentration employed, and on the nature of mineral association. Under some conditions nearly pure molybdenite may be obtained while again the molybdenum content of concentrates may be 25 per cent or even lower. The copper may vary from 3 or 4 per cent to 12 or 15 per cent or even higher. In some cases the copper content may be lower than 3 per cent.

In the 'prior art, success has been had in producing ferromolybdenum from high grade products containing small amounts of copper and other impurities. However, to the best of our knowledge, no practical processes have been developed for economically producing ferromolybdenum from low-grade products containingap- -preciable amounts of copper and other impurities. For many purposes, the copper content of ferromolybdenum should be low and those methods hitherto utilized for producing ferromolybdenum from high grade products containing small amounts of copper and other impurities. have not been economically applicable to the production of low-copper ferromolybdenum from copper-bearing .molybdenite concentrates.

One of the objects of this invention is to' provide a method for producing a low-copper ferromolybdenum from molybdenite concentrates containingpppreciable percentages of copper.

Another object of this invention is to provide a method for producing a low-copper ferromolybdenum from molybdenite concentrates con- .talning appreciable percentages of copper and, at the same time, to produce a copper matte which subsequently can betreated in a copper smelter.

" denum to discard. The matte will contain most of the copper and will be low in molybednum, so that it can be readily treated for the recovery of copper in a copper smelter. The metal will be ferromolybdenum containing copper in amounts which, though appreciable, will not be too high for most purposes for which the ferromolybdenum is to be used.

The percentage of sulphur present during the period of fusion in the smelting step of our process is an important factor in the success of such process. If too little sulphur is present at this time, too much of the copper will tend to combine with the ferromolybdenum and if too much sulphur is present at such time part of the molybdenum will enter the matte together with the copper and iron which normally will be the prin-- cipal metallic ingredients thereof. .As a matter of fact, the sulphur content at the time of fusion may be so high that the product will be practically a single mass substantially devoid of the separate layers which we desire to attain. 35

The desired sulphur content of the mass during the fusion step may be attained in several ways. It will depend partly on the amounts of molyb-- denum, copper, iron and other ingredients in the concentrates or ores. It will also depend partly on the type of furnace used in the smelting operation, since some furnaces tend to eliminate as vapor a larger portion of the sulphur than others. It is not feasible to give the exact ranges of $111- phur content desired, since these will vary with certain types of concentrates or ores. The important thing is that the sulphur content during the fusion step be within such a range that insion will result in the formation of substantially distinct layers, one layer being slag with a low percentage of molybdenum therein, another layer being matte and containing most of the copper with very little molybdenum and the third layer being ferromolybdenum wherein the copper content is not too high.

value.

With most of those sulphide concentrates which we have used to date, the sulphur content has been high and, in these cases, we have found it desirable to roast -these concentrates or ores to lower the sulphur content to a predetermined As indicated above, the sulphur content of the roasted material depends on the amounts of molybdenum, copper, iron, and other ingredients in the concentrates or ores, and on the type of furnace to be used in subsequent melting operations. It may, for example, vary from 5 to 15 per cent, but we do not wish to limit ourselves to this range because in a certain type of concentrates or ores andin certain furnaces these limits may be exceeded. Those skilled in the art can choose a suitable method of roasting. For many purposes, we prefer sintering. However, it should be understood that when we use the term roasting, we intend to include sintering, nodulizing and similar processes.

In the preferred form of our invention, the roasted ore is mixed with suflicient lime or other suitable flux to form a slagwith impurities in the ore product and with ingredients of the reducing agent used in a subsequent step. The lime or other flux may be mixed with the concentrates before roasting.

The roasted product and lime or other suitable flux are smelted in a suitable furnace, for example an electric furnace, with iron and a suitable reducing agent to produce a slag, a matte, and a metal. -Thereducing agent in the charge may be a carbonaceous reducing-agent such as coal or coke, or it may be an agent such as silicon or ferrosilicon, or a combination of both types.

The amount of iron added will depend on the grade of ferromolybdenum to be produced and on the amount of iron in the ore product. The iron maybe in the form of cast iron or'steel, for example, scrap, or iron ore may beused, in which case suflicient reducing agent must be present to reduce the iron ore to metal. If sufficient reducing agent is used, the slag will be low enough in molybdenum to discard. The matte will contain most of the copper and will below in molybdenum. It can be treated for recovery of copper in a copper smelter. The metal will be ferromolybdenum containing an appreciable amount of copper, but'i'or most purposes the cop per content is not too high. For many purposes the sulphur content of the ferromolybdenum is too high; so it is treated with a desulphurizing' slag, which for example may be a high lime slag. If the desulphurizing slag is sufflciently reducing, the molybdenum content will be low enough to permit discarding it, but if it contains an appreciable amount of molybdenum it can be returned as part of the charge in the initial smelting operation. We have been able to reduce the copper content of ferromolybdenum to below 1.5% by this procedure.

It is obvious, of course, that if any matteforming constituents other than copper are present they will likewise be separated in the matting operation. The process, therefore, in its broadest sense involves removal of matte-forming constituents from molybdenum products by a smelting process.

' As a modification of this method, in some instances it maybe unnecessary to roast the con-' centrates. This is true if iron ore is used as a source of iron. Also, in some instances it is possible to use a higher sulphur content in the charge although additional lime will be used either in the charge to slag the additional sulphur or in trates or pyrite.

their copper content in a copper smelter.

the desulphurizing slag used to refine the ferromolybdenum.

Important features are that suflicient flux should be present to slag the ingredients to be removed from the charge and sufficient sulphur should be present to form a copper matte. It is obvious that part of the concentrates may be roasted even to a dead-roasted condition and the sulphur in the charge brought up with raw concentrates. Likewise, it may be possible to deadroast all the concentrates and add sulphur as a sulphur-bearing material, for example pyrite.

Although the product. made by the smelting procedure outlined will be in a marketable form suitable for most commercial uses, in some instances it will be necessary to produce a ferromolybdenum with still lower copper content. This invention is also concerned with making such a product 'by the following procedure.

After the initial smelting step, the slag and mate are removed. The next step comprises forming a matte to remove most of the copper remaining in the metal. As a first step it is usually desirable to increase the sulphur content of the metal, preferably to about 5 per cent or even higher if the metal does not already contain this amount. This can be done by adding a sulphidecontaining material, for example, raw concen- If raw concentrates are used, sufiicient lime or other flux should be used to form a slag with the impurities therein. In either case some matte will be formed, and if concentrates are used some slag will also be formed, which should be low enough in molybdenum to reject. The matte formed when concentrates are used probably will contain enough molybdenum to Justify returning itto the original smelting furnace as part of the initial charge. If pyrite is used for sulphurizing, the matte formed in this operation will be low in molybdenum, and it is not necessary to remove it before proceeding with the next operation. After sulphurization,

the next step is adding pyrite or similar matting agent to matte oil most of the copper still remaining in the metal.

,To reduce the copper content still lower the metal is treated with ferromanganese or with manganese ore and a suitable reducing agent to forma manganese-copper matte. It is not necessary to skim the matte between the pyrite and manganese treatments. Of course, skimmingthe' pyrite matte before addition of manganese is op tional. The composite or individual mattes will be low in molybdenum and can be treated for' The ferromolybdenum will be low in copper, but will contain an appreciable amount of sulphur; so it is treated with a basic desulphurizlng slag. The metal after the desulpliurizing treatment will be low in sulphur. The copper content will be 0.7 per cent or less, and may be lower than 0.5 per cent. The desulphurizing slag, if reducing, may be low enough in molybdenum to discard, or if it contains molybdenum, it can be added as part of the charge in the initial smelting step. It is obvious, of course,'that should any product outlined above for removal from the system be too high in molybdenum to discard it can be returned to the circuit to recover the molybdenum therein.

I 'In the above matting operation, in which the ,ferrochromium, aluminum, and Ierrosilicon. Be-

cause of their availability and relatively low cost, we ordinarily prefer to use manganese products.

While the process has been carried out on numerous products in various furnaces two examples will be given to illustrate the principal features of the invention. Concentrates of the following chemical analyses was used:

Per cent Ingredient Example 1.--A charge of 66 lbs. roasted calcines containing 5 per cent of S and 8.3 per cent each of .coal and C20, 15.5 lbs. raw concentrates,

-10.5 lbs. iron shavings, and 10.5 lbs. coal was smelted in an electric furnace. The resultant metal after .removal of slag and matte con.- tained 46.8 per cent of Mo and 1.4 per cent of Cu.

Example 2.Concentrates were sintered with lime to yield a product containing 25.6 per cent of Mo,l2.'7 per cent of S, and 10 per cent of 09.0. A mixture of 540 lbs. sinter, 125 lbs. boiler plate punchings, and '75 lbs. coke was smelted in an electric furnace. After the slag and matte were removed, 70 lbs. of concentrates containing 82 per cent of MOS: was added. The matte and slag were removed, and 15 lbs. pyrite added, and after reaction between pyrite and metal 15 lbs. high-carbon, 80 per cent Mn, ferromanganese was added. The matte was removed, and the metal treated with a high lime slag; The final metal analyzed as follows:

The above examples are illustrative only, and other grade concentrates can be used, and any of the alternative procedures can be employed. For

example, Ierrosilicon can be used instead of coke as the reducing agent and sulphurizing may be effected by pyrite instead of concentrates. Obvi ously the step of treatment withmanganese may i be omitted it the copper content is low enough in the ferromolybdenum for its contemplated use.

It will be seen from the above that we have provided a novel method which is of great importance to the metallurgical industry because it is a simple and inexpensive method by which ierromolybdenum suitable for the metallurgical industry can be obtained from low grade products containing appreciable amounts oi copper and other materials. Moreover, the amount of copper present in the ferromolybdenum produced can be regulated to render it suitable for any.

particular'purpose for which it is to be utilized.

Thus, it will be seen that this invention makes possible theluse of concentrates and are products for the making of ferromolybdenum that have not previously been available because there has been no simple and economical method for recovering ferromolybdenum from such concentrates and ore products which ferromolybdenum is substantially free from objectionable quantitles of copper. It is likewise apparent that our process results in the formation of a matte which contains substantially all of the copper in the concentrates or ores and which can readily be treated in a copper smelter.

In the claims, the term iron is intended to include cast iron, ingot iron, steel or iron are together with a suitable reducing agent. Likewise, the term concentrates, as used in the claims is intended to include high grade ores which do not require concentration.

Having thus described our invention, what We claim. is:

l. The method of making ferromolybdenum from copper-bearing molybdenum-containing material which comprises smelting a charge com p taining a copper-bearing molybdenum product, a slag-forming flux, at reducing agent, and iron,

' such charge being further characterized by con-- primarily of ferromolybdevnum, removing the forming ingredient which comprises smelting a such charge being further characterized by con-v taining sulphur in selected amount and with the components so proportioned and in such form as to yield slag, matte, and metaLconsisting primarily of ferromolybdenum, and separating the metal from the slag and matte.

4. A. method of making ferromolybden denite concentrates, adjusting the sulphur content of the concentratesto within a selected range such that a copper matte will be formed during subsequent smelting, smelting said concentrates with a slag-forming 'fiux, iron and a reducing agent to form during fusion a layer of slag, a matte and a meta1 consisting primarily of ferromolybdenum,'and then separating the metal from the slag and matte.

5. The method of making ferromolybdenum from copper-bearing ,molybdenumcontaining material which comprises smelting a charge containing said molybdenum product, a slag-forming flux, a reducing agent, and iron, such charge be- -which comprises selecting copper-bearing molyb ing further characterized by containing sulphur in selected amount and with the components so- 6. A method of making ferromolybdenum which comprises smelting partly roasted copper-bearing molybdenite concentrates with iron, a reducing agent, and a flux capable of forming a slag with ingredients in the charge to form a slag, matte and metal, removing the slag and matte, .adding additional concentrates and removing the matte formed, adding successively pyrite and one of the group consisting of manganese, ferromanganese, and manganese ore and a reducing agent,

removing the matte and treating the metal with a desulphurizing slag. I

'7. A method of making ferromolybdenum which comprises smelting partly roasted copper-bearing molybdenite concentrates with iron, a reducing agent, and'a slag-'iorming flux, removing the slag and matte formed, and treating the metal with a desulphurizing slag. Y

8. A method of making ferromolybdenum which comprises smelting partly roasted copper-bearing molybdenite concentrates with iron, a reducing agent, and a slag-forming flux to produce a slag, a matte and a metal, and then removing the slag and the matte.

9. A method of making ferromolybdenum which comprises smelting partly roasted copper bearing molybdenite with .iron and a reducing agent to form a matte and metal, removing the matte,

adding a sulphide-bearing material to the metal 2,1as,oso

to form a copper-bearing matte, removing the matte, and treating the metal with a slag to reduce the sulphur content.

10. A method of decopperizing ierromolybdenum which comprises adding to copper-bearing.

ferromolybdenum a sulphurizing agent and one oi. the group consisting of manganese, ferromanganese, and manganese ore and a reducing agent to remove copper as a manganese-copper'matte.

11., A method of making ferromolybdenum which comprises smelting partly roasted copperbearing molybdenite concentrates with iron, a reducing agent, and a flux capable of forming a slag with ingredients in the charge to form a slag, matte and metal, removing the slag and matte, adding a sulphide-bearing material to the metal,

adding a matte-forming ingredient to the metal,