US2468654A - Process of obtaining metals, oxides, and salts, from bituminous shale - Google Patents

Description

April 26, 1949. P. G. BRUNDELL ETAL 2,468,654

PROCESS OF OBTAINING METALS, OXIDES, AND

SALTS, FROM BITUMINOUS SHALE Filed Jan. 20, 1947 CHARGE OF BITUMINOUS \jHALE LIMESTONE OR DoLoMITE, ETC. OXIDIZING (ROASTING oRsINTERINs) I REDUCINGAGENTS IF REQUIRED LIME SHALE 'ASH WITH REDUCING AGENT CONTENT I-5 TIMEs THAT REQUIRED To REDUCE METAL OXIDES LIME |,O---60% BY WEIGHT.

SULFIDIC .sULFUR CONTENT BELOW. 1.5%

FUSION META L sLAs SLAG WOOL VANADIUM AL! 0 MOLYBDENUM K 0 TUNGSTEN RECOVERY TITANIUM INV EN'T. DRE

:F'ET' EUNNEEE 5%1rumcie H Eiig HEITEL EINE rI'z'Im Patented Apr. 26, 1949 UNIED STTS ATENT OFFHIE Per Gunnar Brundell and Stig Harald Tjernstrom, Vargon, Sweden Application January 20, 1947, Serial No. 723,202 In Sweden June 29, 1943 18 Claims.

The present invention relates to a process of obtaining rare metals such as vanadium, molybdenum, titanium, tungsten and others, as well as iron and possibly also aluminium and potassium values from bituminous shale. A further object of the invention is to obtain a slag in the course of the process, which is readily transformable into slag-wool and similar valuable products. By the expression bituminous shale in this connection is meant an argillaceous rock impregnated by organic matter in the form of graphite, carbon and/or bituminous matter. As examples of bituminous shales there may be mentioned the alum shales belonging to the Upper Cambrian and the Lower Ordovician formations, which are found in quite heavy layers e. g. on the North American continent, in Ecandinavla, Scotland, on the European continent and other places. The bituminous shale has for a long time been used for a number of technical purposes, e. g. as a fuel in the burning of lime, for production of shale oil and for the manufacture of building and insulating materials. Shales rich in alumina and potash have been used for the production of alum etc. It is also known that the bituminous shale often contains small percentages of such valuable metals as V, Mo, Ti, W and others. The content of these metals varies very strongly with the character of the shale. Thus, for instance, the Dictyonema shale frequently contains up to 0.35%, and sometimes even more, of vanadium, while molybdenum and tungsten are generally present only in quantities up occurring average compositions of bituminous shales which may suitably be treated according to the invention,

Per cent Per cent Oil 8 MgO 0-2 C 7-25 S 2-10 S102 45-55 Fe 3-9 A1203 -1'7 Ti 0.3-0.6 K 4.- 5 V 0.04-0.4 NazO 0- 1 Mo 0-0.02 CaO 0- 5 W 0-0.01

If the carbon-containing shale is smelted, e. g.

in an electric furnace, the carbon will reduce the metal compounds present, so that a metal bath, the chief constituent of which is iron, and a siliceous slag floating on top of this are obtained. Our investigations have demonstrated that it is possible to cause the valuable metals such as V, Mo, W etc. to enter into this metal bath. The yield of e. g. vanadium, i. e. the proportion between the quantity of Vanadium transferred to the metal bath and the total amount introduced in the furnace with the shale will, however, vary considerably owing to the conditions under which the process is carried out. Our investigations have demonstrated that the amount of metal obtained by this reduction process will, up to a certain limit, increase by decreasing carbon content in the raw material. This rather surprising result is explained by the fact that the amount of carbon present in the shale is considerably higher from the outset than what is necessary for obtaining a complete reduction of the metals in question. The excess carbon will cause considerable difficulties in the smelting of the shale since it will cause a reduction of the compounds contained in the siliceous slag. The products thus formed-chiefly siliconwill partly dissolve in the metal bath. At the same time considerable amounts will escape in a gaseous state from the furnace. This entails the formation of less favorable equilibria in regard to the yield of vanadium. Only in such cases where the chief object would be to obtain alumina and potash in the process would such a far going reduction of the siliceous matter be of any advantage, since by these expedients the silica content of the siliceous slag will be lowered, which makes the slag more suitable for leaching with acids to obtain salts of A1203 and K20.

Our investigations have thus demonstrated that if a high yield of e. g. vanadium is desired,

the raw material, i. e. the shale should, previous to being fused, be subjected to a preparatory heating to oxidizing temperatures in the presence of air. This will lower not onlythe carbon content of the shale, but the non-oxidized (sulfide) sulfur content as well, a fact which has proven advantageous for the subsequent smelt-..

ing.

According to the invention the shale material is thus subjected to a roasting or sintering in the presence of air previous to the reducing smelting, in order to lower its sulfidic sulfur i. e. its non-oxidized sulfur content. Such a roasting or burning is sometimes made in connection with known processes for recovery of oil from the shale, for which reason the solid residue from such processes, e. g. the so-called shaleash, in many cases is suitable for a direct use in the fusion process according to the invention.

The importance of lowering the sulfidic sulfur content in the material previous to the reducing smelting has been clearly demonstrated by our investigations; Grdinary bituminous 'shal'e of:

contents in the charge and in spite of sufficiently high reduction temperature, if the sulphur content of the ingoing shale material is comparatively high, and that a considerable increase" in the yield is attained when, ceteris paribus, the

sulfi'dict sulfur content in the material is lower-ed by ioxidation". previousztb: the reduction: pro cess:

The followin'grfigures may serve as an'e-xamplea of:this significance; Ihe figures relate to. two: samples "of roasted: shale having practicallythesameicontent of Fe; C and Vand fused with thesame amount of CaO'; the difference-mainly beings in the 'su'ltur: content of the material.

Ca0- addition Per cent 4. 7 4. 5-

Per cent 4 Per cent Contents in the corresponding 5 Slag from FeO CaO Si 0 2 l cent Per cent

' Per cent 21 Yield of vanadium asmetol.

From charge Yield.

' Per" i cent The difference in-the'result at different sulphur contents" is striking; Since in this case itwas the question of two shale materials which had been" de -sufuriz'ed to a difi'erent'degreebyadiffei ently'stron'g. roasting, it is evidentthat the effect oftl're lowering of the sulfur content must bestill more pronounced when comparing our process with smelting processes-inwhich a shale material" is subjected" to a reducing smelting withoutany' previous roasting or oxidation at all-and which for this reasonhas a stillhighersulphurcontent; M

When reference is made to the sulphur contentit should always be remembered that it is here a question of the non-oxidized, i. e. the sulfidic sulfur. If the" roasting is, for instance; carried out. on thesh'ale'when mixed with lime or limestone, the sulfur may toa' great extent be re tai'n'e'd by" the lime in theform of sulfite or sulfater" Analyt'icall'y' the sulfur content of the charge may appear to remain high, but due colon =0 to the oxidation which the sulfur has undergone during the roasting it no longer appears in its sulfidic form and has thereby lost its detrimental effect on the metal yield in the reduction process, as our investigations have demonstrated. A plausible explanation of our discovery that the sulfidic'sulfur in: the shaleshould be brought below 1.5'% and suitably under 1% to obtain satisfactory yields of metals is that the sulfur in the shale is chiefly bound to the metals in a sulfidic state. Thus. the iron-at least for the main part -is present as. pyrite and the vanadium probably as V253. If such a shale material having a comparatively high sulfur content, which for instance in Dictyonema shale is often around 2.54%, is directlysubjected to a reducing smelting,.the resulting poor yield most likely may be attributed to a. formation of a finely dispersed sulfidic'r matte. which retains a large part of the metals in the slag instead of letting them pass over intothemetallie-bathr If the shale con tains. oil this may of course first be recovered by known-methods, previous-to a-lowering of the carboncontent of the material by burning;

We haveafoundw that by burning out the car hon-in the shale-or its distillationresidue to such a degreethat the amount'of: carbon leftin the shale iswithin the range of fromone to five times the. amount theoretically needed for a reduction of,.a1l the: content of F6203, TiOz, V205, M003 and WQzwtO corresponding metals, exceedingly high yieldsofa vanadium and other valuable metals-may berealized; It is,.of-.course, also-possible to adjust the carbon-content by mixing a shale, the carbon content of whichis more or less completelyburnt out,.witha shale more rich in carbonor with some other. suitable carbonaceousmaterial, e. g. coal or coke,. so that the above mentioned desired proportions of from one to five times the theoretical above mentioned-oxides is-obtained in the charge. Such additional reductionagent'may also, instead of in=the form of carbonaceous material, be: added in .thaformofae; 1g. FeSi, CaSi, CaCa, Si, Al, Mg, reducing. gases, such as Hz, producer. gas. and similar: It.may-also be advantageous to adjust the carbonwcontent by; adding reducible oxides orsimilarmaterial e. g.,iron orezor other iron contaming. materials, whereby a simultaneous adjusting of theamount or vanadium and if desired also of molybdenum and tungsten in the resulting metal-bath may be obtained; It should, however,

be noted that the carbonior carbonaceous materialthat the energy-consuming reduction of the silica in the shale is highlyuepressed.

The equilibrium between .slag and metalbath.

1 changes. in the acidity of the slag may cause.

great. variations in .the yield of vanadium, molybdenum etc. A suggested explanation oi this is the amphoteric nature of the corresponding metal-oxides although nothing definite can be-sai'd as to the reasonsi'onthe statecl and ob-- amountof. carbon needed for a reduction of the:

served fact. The acidity of the slag may be adjusted by the addition of basic slag forming material. By this addition the fusing point of the slag is influenced in the sense that it falls with rising content of basic material. Hereby it is possible to attain the temperature range which is most favorable for the reduction process. At too high reduction temperatures, e. g. when the slag has a high fusing point, the yield of vanadium will decrease at the same time as the iron content of the slag increases. At too low reduction temperatures, on the other hand, the reduction will become unsatisfactory. It is thus possible to adjust the reaction conditions properly by adjusting the acidity (basicity) of the slag, which stands in close relation to its fusing point. Suitable reaction conditions are as a rule obtained within the temperature range 1500 to 1800" C., particularly in the vicinity of 1600 C..

If the shale is melted together with a suitable amount of burnt lime, limestone, dolomite and/or other slag forming basic materials containing CaO, MgO, BaO, NazO or K20 the yield of vanadium, molybdenum etc. may thus be considerablly increased. The addition of burnt lime, limestone or equivalent basic material, which necessarily must be adjusted with regard to the composition of the shale, will thus vary between wide limits The addition, however, must be sufiicient to produce a lowering in the viscosity of the slag but not substantially exceeding the quantity required to produce a basicity in the slag bath corresponding to a CaO content of up to 60%. The optimum conditions are, however, generally obtained in the rather narrow range of about to 25% CaO. Additions of lime or other basic material in such quantities that the basicity of the slag will be over 60% calculated as CaO, entails a gradually in creasing and undesirable formation of carbides. The viscositycurve will also become of such form that the slag will be unsuitable for slag-wool production.

The favorable influence of the basic addition on the yield of vanadium etc. is that it makes the slag more fiuid, by lowering its viscosity, whereby a more rapid separation of slag and metal may be effected, tapping is facilitated and better conditions will prevail during the smelting, since the heat transfer in the molten charge is considerably improved when the slag is easy flowing. When utilizing the slag for making slag-wool and similar products a still lower viscosity than what is produced within the above mentioned optimum basicity range may be de sirable in order to obtain a suitable composition and workability of the slag for said purpose. In such event the basicity, computed as CaO, may suitably be increased up to as high as 40 and even more. This will generally mean a slight decline in the yield of vanadium which, however, in such cases is more than offset by the gain in regard to the qualityrof the slag, since the removal of iron from the slag will be practically unchanged while the physical properties desirable in slag-wool products are materially improved.

Our investigations have demonstrated that it is of great importance that the slag forming basic materials are added in the right proper tions. Thus the yield of vanadium, molybdenum etc. will first increase with increased addition of basic material up to a maximum and then again fall upon further increase of the basic components in the slag. It is, however, not possible to state any definite figure for the position of the maximum point that would hold for general conditions, because of the rather complicated system which is represented by the slag. It is evident that the maximum point will become displaced according to the composition of the shale, the largest variations being due to the contents of $2102, A1203 and alkali in the shale. The aforementioned figures for the slag basicity, corresponding to not over calculated as CaO and preferably lying between 10 to 25% Ca) will, however, hold for the usual composition of the shales e. g. as according to the above stated table of analysis.

The heat value of bituminous shale is generally between 500 and 2500 kilogram calories per kilogram. When adjusting the carbon con tent of the shale according to the invention, a considerable amount of the heat value of the material may be utilized by calcining a quantity of limestone with the aid of the burning shale, said quantity being calculated such that the mixture of burnt lime and shale ashes resulting from the burning will yield a siliceous slag in the subsequent smelting, having a suitable CaO-content for obtaining the highest yield of vanadium. For shales with higher heat values the burning may be carried out in such a manner that the mixture of shale ashes and burnt lime will leave the furnace with a temperature of up to 950 C. or more, in which condition the mixture is ready for immediate charging into an electric furnace. The burning and preheating may of course also be aided by addition of suitable fuels, e. g. coke. The smelting process is not limited to the use of electric furnaces but may also be carried out in blast-furnaces, reverberatory furnaces or the like.

While testing various modes of carrying out the oxidizing step of the invention we have made the rather surprising discovery that the use of a sintering process similar to the known procedures for treating metal ore concentrates and employing similar equipment, e. g. as described in Liddel Handbook of Non-Ferrous Metallurgy (part I, 1945, Chapter X, Roasting and Sintering), produces very favorable results in several respects as against conventional roasting treatment, as will be more fully explained in the following.

Previous to such sintering the charge is reduced to a suitable particle size. If it is desired to obtain a sinter with good mechanical strength for the purpose of being used in smelting equipment where such strength is desirable, the crushing of the shale and other material possibly entering the charge, should preferably be made so that the various grain classes will be fairly uniformly present. A suitable grading is generally obtained by crushing down the raw-material to correspond to a maximum of about 5 millimeters in diameter. In order to prevent clogging finer grains than about 0.08 millimeters should be avoided.

The ignition of the sintering charge is made in the same manner as known in connection with the conventional sintering of metal ore concentrates, e. g. by means of a gas-burner or by using a layer of charcoal breeze and Wood-wool. In order to lower the resistance for the suction of gases through the charge during sintering,'this is suitably loosened up or made porous by 7 means off arradditiomof water.- in. an; amount-of forplnstancer 5-,15;per cent-of. the weight of the charge. The charging of the sintering pan is suitably made. over. a spike roller or through a screen to preserve the even and porous structure of-the charge when placed; in. the pan.

The shale material; employed has generally such: a high, heatvalue that no extra fuel is needed, in the charge. On the contrary, there iszfrequently so much fuel contained in the shale material. that considerable quantities of basic slag, forming substanceswmay'be admixed therewith without the heat valuebecoming too low. Thus-for instance, in sintering ashale containing 9% C, an addition; of ,upto 70% of the weight of the shale of limestoneydolomite or other suitable:carbonatecontaining material may be made, whereby these carbonate materials at the same time will for the larger part become transformed toioxides. In this manner it is possible in a very simple Way to producea charge which after a possible addition of reducing agents is ready for immediate use in thelsmelting furnace.

Our; tests have shown that if the shale particles exceed a certain grain size, which however varies somewhat with-the nature of thematerial, they will not become completely roasted but will contain an unroasted core. grainzsize it is thusbymeans. of a few test-runs possible to determine how much carbonaceous material may be left. inthe sinter tobe used as reducing agent inthe following: smelting process. The amount of carbonwhich in this manner may be left, is however dependent onhow far the simultaneous oxidation and removal of the sulfide sulfur can be realized,1 asthis varies from one shale to another. In some instances it is necessary to burn out practicallyall of the carbon in the shale in order to lower the sulfide sulfur to an amount corresponding to optimum yield of metals in the subsequent reduction process. Other shales on the other hand, when roasted down to a carboncontent of about 3% which is suitable for the reduction process, have at the same time lost enough sulfide. sulfurto. suit the optimum requirements-,. and. no extra reduction agentis thus needed insuch-cases.

As already mentioned in theforegoing, a roasting inthe presence of basic slag. forming materials,. e. g. limestone, may cause the sulfur originally contained as unoxidized sulfide sulfur. in the shale to remain for the larger part in the charge, although. now in theform of sulfite and sulfate and thus without detrimental influence onthe subsequent metal reduction process. have found that someof these sulfites and sulfates may-become thermally dissociated whereby sulfur partly escapes in-the form. of oxides and partly is reduced back to a. sulfidic form. This secondary sulfide. sulfur is, however, of. no detrimental influenceonthe yield of e. g. vanadium, sincethe sulfur in this case during the reduction is bound to thelime. sintering temperaturefor instance from 950 C. to 1200 C., e. g. by increasing; the heat value of the charge, using stronger suction through the pan.etc.- it will thus, owing to a. higher thermal dissociation of the sulfites and sulfates already during, the sintering operation; be possible to causea substantial lowering of the total sulfur content of the charge. This will materially help toelessen the formation-of secondary sulfide sulfur in the;subsequcntreduction; process which,

even if it ,is of no particular value-in regard to.

By adjusting the.

Byv increasing the 8; the yield of. metal, is of.importance in making slag-wool or foam by conventional methods from the ensuing slag. Already a. fraction of a percent of calcium sulfide in the product maybe sufficient to spoil its quality, owing to the instability of this compound under certain conditions particularly in the presence of Fe. Such a sintering temperature that thermal dissociation of sulfites and sulfates will take place to a subi stantial degree is thus-a valuable step in theprocess according to the invention. Especially in the case of slag foam, where the material contains numerous pores and vesicles in which hydrogen sulfide, which may form when the calcium sulfidein the slag is brought in contact with water during the well known foaming process, becomes included and from which it subsequently gradually diffuses into'the atmosphere, it is extremely important that the product is as stable as possible, since it will otherwise be perfectly valueless as insulating material in buildings because of its nauseating smell.

When sintering is made of a charge having avery high heat value, a fusing may take place in the sintering zone, The grains of shale material in the charge will thereby become encased in an impervious glazing and prevented from becoming roasted or oxidized. This may be prevented by adjusting the heat value of the charge by adding a sufilcient amount of returns from previous sinterings in theingoing charge on the sintering equipment.

If the sintering operation is interrupted when the zone of sintering has reached the grate the sinter generally is very hot (e. g. 500-800 C.). From the point of heat economy it is advantageous to charge this hot sinter directly into the reduction furnace, possibly after a coarse crushmg.

The high efficiency of the process in transferring the metals in question into the metal bath entails the great advantage that the slag will show a comparatively low content of the sulfide forming heavy metals in question (Fe, V, Mo, W); the percentage of Febeing generally below 0.5% and quitefrequently as low as 0.2%, theother metals (V, Mo, W) in proportion thereto generally being present in a total quantity of less than 0.05%. When blowing such slag by known methods a slag-wool of light color and very attractive appearance is obtained, provided that the basicity is sufficiently high e. g, 25-45% ad even up. to 55% calculated as CaO. A far going reduction of the heavy metals (Fe, V, Mo etc.) is very much dependent upon the degree to which the corresponding sulfides are transferred to oxides during the sintering. A reducing smelting of shale or shale residue having a high.

content of sulfide sulfur bound to heavy metals will yield a slag which contains a comparatively high. percentage of these metal sulfides in solution or very finely dispersed. A slag wool from such a slag will have a dark color and frequenty decomposes in the presence of moisture while giving off sulfur containing gases.

As an example of the result of a properly'conducted sintering accordin to above statedprinciples may be mentioned that a slag-wool blown from a slag which had a content of secondary sulfide sulfur as high as 1.7% (chiefly as calcium sulfide) but practically free from heavy metals (0.3%) uponboiling in water for 6 hours did notlosemore than 0.0009 S.

The invention can beunderstood readily from" a study of the accompanying drawing in which the figure is a flow sheet of our process. The legends on this flow sheet are believed to make it self explanatory.

In the flow sheet the arrows shown in full lines represent the preferred procedures while those with dotted stems represent optional procedures. As indicated, a charge of bituminous shale is first subjected to an oxidizing treatment which may be either a roasting or a sintering procedure. The conditions are so controlled during the oxidation that the sulfidic sulfur content is reduced below 1.5%. Limestone or dolomite can be added to the charge undergoing oxidation if desired. The reducing agent content of the resulting shale ash is then controlled so that the reducing agent present amounts to from about 1 to 5 times that required to reduce the metal oxides. The lime content is also controlled so that the reducing agent present amounts to from about 1 to 5 times that required to reduce the metal oxides. The lime content is also controlled so that from to 60% by weight is present. The batch is then smelted. The slag is drawn on and either blown into slag wool or treated for recovery of its A1203 and K contents. The metal which is recovered from the smelting step contains substantially the entire content of vanadium, molybdenum, tungsten and titanium present in the original bituminous shale.

Our invention can be explained in greater detail by reference to the following specific examples which represent practical operating embodiments of processes which result in the recovery of metal values and slag wool from bituminous shales in accordance with the present invention. These examples are not to be considered as limiting the scope of our invention.

EXAMPLE 1 1000 kilograms of shale containing 9% C and 2.6% S (as sulfides) were crushed down in a ball mill to a maximum particle size of 3 millimeters with an even grain class distribution down to about zero and mixed with 700 kilograms of dolomite (all particles below 3 mm. and about same grain distribution as the shale). The mixture was moistened with 225 kilograms of water and subjected to sintering in an ordinary suction sintering pan. The sintering temperature was during the operation which lasted minutes kept around 950 C. The highest temperature of the escaping gases was 220 C. No extra fuel Was added.

The resulting sinter contained 0.1% C, 0.2% sulfide-S, 19.2% CaO and 13.2% MgO. The total sulfur content of the sinter was 1.2%. After reducing smelting for recovery of metals according to the previously described procedure in a direct arc furnace the slag was recovered and blown to wool by the conventional method using compressed air as blowing medium. The wool product showed very high quality in regard to color and elasticity. It analysed as follows:

Percent S102 45.0 A1203 13.7 TiOz 0.4 CaO 20.3 MgO 14.5 Fe 0.2 V, Mo Less than 0.04 S 1.0 Alkali oxides 4.1

The yield of vanadium was in this instant 89% in spite of the fairly high basicity of the slag, which demonstrates the efficiency of the sintering process as applied in our invention.

The surprising discovery in the course of our investigations, that the heating of the raw-material while subjecting it to oxidizing conditions, with or without the presence of additions of basic slag forming substances, to such high temperatures that a sintering takes place which at first was considered objectionable, instead produces a charging material for the reduction step in the process which is exceedingly apt to give high yields of metals under such conditions that a sla is at the same time obtained which is particularly well suited to be worked up to slag-wool and similar products, means a very definite improvement both of a technical and commercial nature of our process as originally outlined. The sintering procedure not only facilitates the proper adjustment of the carbon content in the oxidized material intended for the subsequent reduction step, at the same time as it permits of a very far going oxidation of the sulfur, but it also provides a material which in the reduction step readily lends itself to a quite unexpected completeness of separation of the heavy metals in the charge into the metal bath while leaving a very pure slag behind. The reason for this favorable resuit is not quite understood but we at least partly attribute it to the very even oxidation of the raw-material which may be obtained in a sinterin apparatus as against other conventional shale roasting or burning equipment, such as shaftfurnaces and the like, as well as possibly to the more even distribution of the homogeneously oxidized shale material in the charge which is attained in this manner, particularly when the sintering procedure is carried out with a mixture also containing basic slag forming additions, in which case a very uniform charging material for the reduction furnace is obtained, whereby the chemical reactions and the separation of the slag and metals evidently is highly facilitated.

As further representative examples of sinterlng procedures according to the invention the following may be stated.

The charge which had the same grain class distribution as in Example 1 was treated in thesintering apparatus without extra fuel, except for the ignition. The operation lasted for 45 minutes during which time the oxidation and sintering took place. The maximum temperature in the sintering zone was about 1000 C. The obtained sinter was crushed to lumps of about 2"- diameter and mixed with 4.5 per cent of its weight of charcoal breeze /2" lumps). The well mixed charge was then smelted in a direct are electric furnace. The slag was tapped at about 1500? C. and blown to slag-wool by means of compressed air in the conventional way whereby a product with long, fine glass-wool like, extremely elastic fibres Was obtained. .1

ii The metal bath was recoveredseparately" and cast' to ingots. The yield of vanadium was 89%. The slag analyzed:

The sintering operation was mainly carried out as described in connection with Example 2, the grain sizes of the material being about the same. The main difference from Example 2 is that no carbonate material (dolomite, limestone) was added. For this reason a certain quantity of ready sinter was returned and mixed with the charge, as seen from the table, in order to adjust the mean heat value of this, which otherwise would have been too high. The obtained sinter was reduced to lumps of about 2" diameter and mixed with 45 per cent of its weight burnt lime and 5.5 per cent of its weight coke breeze (below /4).

The charge was smelted as in Example 2. Yield of vanadium 87%. The basic content of the slag calculated as CaO was 39%. The slightly lower yield of vanadium as against Example 2 is probably mainly due to the fact that the sintering' took place in the absence of basic additions. In all three examples the amount of reducing agent in the fusing step was about two to three times that needed for reduction of the heavy metal oxides.

The slag-wool obtained according to the invention is in its general appearance of about the same character as glass-wool, i. e. it differs favorably from other known slag-wool and so called rock-wool products in that it has considerably longer fibres, which even compared to glass-wool show a great improvement as regards elasticity. The product is easily distinguished from all of the aforementioned known products by its chemical analysis, the characteristic features of which are as follows:

Fe Below 0.5% S 0.3% to 2.0%, normally about 1% Total CaO, MgO and alkali oxides 25% to 55% Alkali oxides 2%-7%, normally 4%-5% SiOz 38%50% A1203 %15% The slag may to advantage be used not only for producing slag-wool by known methods but also other products such as slag-foam and similar insulating materials, owing to its high qualities in regard to properties desirable in the manufacture and use or" these known products.

The siliceous slag may also be finely ground and leached with acids in order to obtain aluminium I2 and potassium values. .Thefacility'of extraction increases strongly and rapidly with increased basicity of the slag, so. that it is possible already at a comparatively low basicity, within the limits stated, to obtain a practically complete recovery of said values,

From what has been stated above is seen that the process according to the invention willtgive extremely high yields of vanadium and other valuable metals when observingtheconditions in regard to proper adjustment of the carboncontent of the shale and in the charge, a lowering of heavy metal bound unoxidized. sulfur priorto smelting to below 1.5% and preferably below 1%, adjusting the basicity. of the. slag etc. Ourtests have shown that it is possible. to'attaintan almost quantitative collection ofsuch'metals asV, Mo, Ti and W in the metalibathif these conditionszare properly observed, i. e. by smelting shalevwith 'a suitable carbon content together with the proper amount of lime, according to the general principles of the invention already set forth. As already mentioned, the siliceous slag obtained in the process is well suited to a further treatment for the obtaining of A1203 and K20 therefrom, as well as for the manufacture of building and insulating materials.

It should in this connection .beipointectout that in order to sufiiciently lower the original. sulfide sulfur content it may be necessary to subject the shale-to such an intense oxidizing treatment that its inherent carbon content may berburnt down to such'extent that additionof external reduction agent is necessary. The above-outlined sintering procedure has in these instances proven particularly useful for preparin ashale material which will readily lend itself 'to complete reduction-in regard to the metals in question in spite of the fact that use can not be had of native carbon in the shale except to perhaps a very small extent. This is probably due to the fact that a sintered charge. becomes very porouswhereby'a gastransport into it from external reduction agents is facilitated.

The slag and metal baths may be tapped from the furnace either separately or together, in which latter case they are separated. outside this-and subsequently treated separately.

The metal bath obtained by the smelting, will in favorable cases hold e. g. 10% vanadium and may be processed in various ways, for instance by forming a vanadium slag by adding iron ore, chromium ore or other suitable ore. The remaining iron may to advantage be worked up to steel e. g. in an electric steel furnace.

Considering the fact that the percentages of vanadium, molybdenumetc, in the shale are very small and in general of the same order of magnitude as those inslags from metallurgical processes, and furthermore considering that the slag bath constitutes about to and the metal bath only 10 to 5% of theshale raw material entering the process, it must. be said. to be. quite surprising that under these circumstances it is possible to carry out a metallurgical process with analmost quantitative yield of the said metals. The reason for this extremely satisfactory result may, in addition to the above outlined expedients in regard to proper adjustment of the carbon an'd lime content, in such caseswhere. only. a mild roasting has taken place, be sought in the" fact that at least a substantial proportionofthe reducing agent employed consists of the carbon present' in the material itself which as already stated, in the bituminous shales is intimately distributed 13 throughout the material, whereby anexceedingly even and speedy reduction is obtained.

The following examples serve to further illustrate the process according to the invention as applied without sintering.

A Dictyonema shale having an ignition loss of 13.1% contained 9.5% carbon and a'3.1% sulfur. After roasting this shale yielded an ash of the following composition:

15,300 kg. of this ash was mixed with 2300 kg. of burnt lime with the following analysis:

Per cent Ignition loss 3.0 SiOz 8.2 A1203 0.8 F8203 0.7 CaO 84.8 MgO 2.3

The mixture was fused in an electric furnace. Hereby 15,200 kg. of slag and 849 kg. of metal were obtained with the following compositions:

Slag: Per cent Metal: Per cent S102 57.? Fe 78.0 A1203 18.5 Si 13.6 F8203 0.5 V 5.21 TiOz 0.3 Ti 1.5 CaO 14.1 P 0.7 MgO 2.4 Mo 0.25 Alkalies Mn Percent Sulfur 0.8 V 0.029 Vanadium yield 91 As a further example of the efiiciency of the process according to this embodiment of the invention may be stated that a shale ash with a vanadium content of 0.06% upon fusing with lime gave a vanadium yield of 96%.

The following tables demonstrate the influence of the carbon and lime contents. The starting materials consisted of burnt lime of above analysis and shale from which the above ash was prepared by roasting without sintering.

l. VARIATIONS IN CARBON CONTENT CaO-content of slag about 14% Carbon Vanadium Yield of cor tent in Metal man bath Vanadmm Per cent Per cent Per cent 14 2. VARIATIONS IN THE LIME AnmrIoN Carbon content of ash about 3.4%

0210- Vanadium Yield of content in metal oi slag bath vanadmm Per cent Per cent Per cent 2. 0 3. 38 65 9. 3 4. 12 77 14.0 4. 89 91 19. 7 4. 92 25. 5 4. 56 83 These figures are of particular interest when compared with the high yields of vanadium which are obtained in the upper basicity range, from about 25 to 45% CaO and more, when using a sintered charge and which as a rule can not be attained by a mere roasting of the material.

The present application is a continuation-inpart of our copending application, Serial No. 541,270, filed June 20, 1944, which now stands abandoned.

We claim:

1. In the treatment of bituminous shales by reducing smelting for recovery of at least one of the metals vanadium, molybdenum, titanium and tungsten contained therein, the process which comprises first heating such a shale to oxidizing temperatures in the presence of air under conditions causing a lowering of its heavy metalbound sulfidic sulfur content to below 1.5 per cent by weight; adjusting the reducing agent content of the charge to be smelted to within the range from about 1 to 5 times the quantity required for complete reduction of the metal oxides of iron, titanium, vanadium, molybdenum and tungsten contained therein, adding basic, slag forming materials in quantity sufficient to lower the viscosity of the slag formed in the subsequent fusion step but not substantially exceeding the quantity required to produce a basicity in the slag bath corresponding to a quantity of 60 per cent by weight of said slag, calculated as CaO, fusing to form a metal bath and a siliceous slag bath, separating the metal bath and recovering the metal values therefrom.

2. A process for the recovery from solid bituminous shale distillation residue of at least one of the metals vanadium, molybdenum, titanium and tungsten contained therein by reducing smelting, comprising selecting such a material having a content of heavy metal-bound sulfidic sulfur of less than 1.5 per cent by weight, adjusting the reducing agent content of the charge to be smelted to within the range from about 1 to 5 times the quantity required for complete I'BdllC". tion of the metal oxides of iron, titanium, vanadium, molybdenum and tungsten contained therein, adding basic, slag forming materials in quantity sufiicient to lower the viscosity of the slag formed in the subsequent fusion step but not substantially exceeding the quantity required to produce a basicity in the slag bath corresponding to a quanity of 60 per cent by weight of said slag, calculated as Ca0, fusing to form a metal bath and a siliceous slag bath, separating the metal bath and recovering the metal values therefrom.

3. The process according to claim 1 wherein the basicity of the slag is adjusted to within the range of from about 10 to 25 per cent by weight, calculated as CaO.

4. The process of claim '1 wherein the bitumi- 1'5 nous shale originally'contains an: excess of car bon, the carbon content being brought within 1 the limitsstatedfluring theoxidizingtreatment.

5. The process of claim 1 wherein the bituminous shale contains an excess of reducing agent I and the relative quantity of the latter in the charge is adjusted by the addition of iron oxide.

6. The process of claim 1 wherein basic ma- I tcrial necessary for adjusting the basicity of the slag is added in the form of carbonate previous to the oxidizing step whereby during the course of the oxidizing treatment-it is transformed to the metal bath said slag is transformed intoa-slagwool product.

, lfLvThe process of claim l wherein the oxidizing-andfusingsteps are conducted in different equipment and the productobtained. inthe oxidizing step is transferred to the fusing step at high temperaturesup to about 950 C.

, 11. In the treatment of bituminous shales by I reducing smelting for recovery of at least one of the metals vanadium, molybdenum, titanium and tungsten contained therein, the process which 7 comprises heating such a shale to oxidizing temperatures in the presence of air under conditions producing a lowering of its heavy metal bound sulfidic sulfur content-to below 1.5 per cent by weight, adding basic, slag forming materials in quantity sufiicient to lower the viscosity of the slag formed in thesubsequent fusion step but not substantially exceeding the quantity requiredto produce a basicity in the slag bath corresponding to aiquantity of 60 percent by weight of said slag, calculated as CaO, subjecting said mixture to a reducing smelting toform a metal bath and a siliceous slag bath, separating the metal bath and recovering the metal values therefrom.

12.--Ini the treatment of bituminous shales for recovery of their vanadium, molybdenum and tungsten contents, the process which comprises adjusting the reducing agent and lime contents of such a shale so that the reducing agent content isinsuflicient to cause any substantial. reduction ofthe'SiOz present to Si'in the subsequentfusion step'and is from 1 to"5 times the quantity required for the complete reductioniof the metal oxides of iron, titanium, vanadium, molybdenum and tungsten contained therein and the-CaO content is within the range of about 10 M percent based on the weight of the siliceous slag fo'rming components, at least a substantial proportion of the reducing agent present consisting of the natural carbonaceous materialin saidshale, then fusing the mixture toiorm a metal bath and a siliceous slag bath, separating the metal bath from the slag bath and treating them separately for the recovery of their metal and mineral values.

i13.ZThe process of claim 12 wherein the reduclng agent content of saidfslag is adjustedby roasting. the bituminous ishalev to reduce its carbon content to within the range stated.

A 14.- In theitreatment of bituminous-shales for T6 recovery "of their vanadium, I molybdenum and tungsten contents, the -process which comprises adding limestone to such a shaleb-in" quantity sufficient to supply from about I0 to 25 per=cent du'ce complete reduction of theoxides of the metals iron, titanium, vanadium, molybdenum and tungstenwhich arepresentand-insuificient to cause any substantial reduction of -the SiOZ content to Si, in -the following -fusion 7 step; then fusing the mixture to produce-a metal bath-and a siliceous slag, separating the metal bath and re-- covering metal values therefrom;

'15. The process of claim-14 wherein-the roa'sting and fusing steps are conducted in different furnaces and the mixture-is transferred from" the roasting to the fusingfurnace-at high-temperatures not exceeding aboutN950 Cr '16. In the treatment'of bituminous shales for recovery of their vanadium, molybdenum -and tungsten contents, the process which comprises roasting such a shale 'in' the presence of air to lower its carbon contentb'elow that-producing any substantial reduction ofthe SiOzpres'ent to Si inthe following fusion step but leaving the carbon content within the range of from l'to 5 times the quantity requiredfor complete reduction of the'metal oxides of iron, titanium, vanadium, molybdenum and tungsten contained therein, adjusting the content of basic slagforming materials in the shale to within the range of about 10 to 60 per cent, calculated as CaO, fusing to forma metal bath and a siliceous slag bath, separating the metal bath and recovering metal values therefrom.

'17. In the treatment of bituminous shales for recovery of their vanadium, molybdenum and tungsten contents, the process which comprises roastingsucha shale in the presence of air and adjusting its carbon content within'the range of from about 1 to 5 times the-quantity required for complete reduction of the metal oxidesof iron, titanium, vanadium, molybdenum and tungsten contained therein, adding basic, slag-forming materials in quantity sufficient to lower the viscosity of the slag formed in the subsequent fusion step but not'exceeding a quantity of 60 per cent by weight, calculated as CaO, fusing to form a metal bath and'a siliceous slag bath, separating the metal bath andrecovering metal Values therefrom.

18. The process which comprises heatinga bituminous shale to oxidizing temperaturesin the presence of air to reduce its content of sulfidic sulfur below 1.0 per cent by weight; adding basic, slag-forming ingredients to the resulting shale ash in quantity sufficient to p-roduce a basicity in the slag bath corresponding to a content of'from about 25 to 45 percent of CaO, controlling the reducing agent content to a value corresponding to from 1-to5 times the quantity required for complete reduction of the metal oxides of. iron, titanium, vanadium, molybdenum and tungsten mentioned therein, fusing the resulting charge to form a metal bath and a siliceous slag bath, and recovering the slag and the metal.

PER GUNNAR BRUNDELL. STIG HARALD TJERNSTRbM.

(References on following page) 17 REFERENCES CITED The iollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,300,410 Johnson Apr. 15, 1919 1,334,004 Toorn Mar. 16, 19 20 1,369,298 Pennim-an Feb. 22, 1921 18 Number Name Date 1,815,888 Baily July 28, 1931 1,907,868 Powell May 9, 1933 2,028,105 Head Jan. 14, 1936 2,223,047 Ramseyer Nov. 26, 1940 2,313,044 Brassert Mar. 9, 1943 OTHER REFERENCES Chemical Abstracts, v01. 35, 1941, columns 6397 and 6398, Hultman.

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