CA1044486A - Molybdenum and ferromolybdenum production - Google Patents
Molybdenum and ferromolybdenum productionInfo
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- CA1044486A CA1044486A CA200,296A CA200296A CA1044486A CA 1044486 A CA1044486 A CA 1044486A CA 200296 A CA200296 A CA 200296A CA 1044486 A CA1044486 A CA 1044486A
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- molybdenum
- iron
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B34/00—Obtaining refractory metals
- C22B34/30—Obtaining chromium, molybdenum or tungsten
- C22B34/34—Obtaining molybdenum
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Abstract
ABSTRACT OF THE DISCLOSURE
A process is provided for preparing briquettes comprising molybdenum or a mixture of molybdenum and iron, said briquettes being of such density as to be capable of penetrating steel slags. The process is a two-stage process in which molybdenum trioxide is reduced at about 500° - 650°C to molybdenum dioxide and the molybdenum dioxide or a mixture molybdenum dioxide and iron oxide is reduced at about 800 - 900°C to metallic molybdenum or a mixture of metallic molybdenum and iron. Gaseous hydrogen as hydrogen per se or in the form of dissociated ammonia is the reducing agent.
A process is provided for preparing briquettes comprising molybdenum or a mixture of molybdenum and iron, said briquettes being of such density as to be capable of penetrating steel slags. The process is a two-stage process in which molybdenum trioxide is reduced at about 500° - 650°C to molybdenum dioxide and the molybdenum dioxide or a mixture molybdenum dioxide and iron oxide is reduced at about 800 - 900°C to metallic molybdenum or a mixture of metallic molybdenum and iron. Gaseous hydrogen as hydrogen per se or in the form of dissociated ammonia is the reducing agent.
Description
Molybdenum has long been used as an alloying additive in the production of stainless and alloy steels. ~e general practice for all grades of alloy steels is to charge the required quantity of molybdenum or molybdenum trioxide along with the scrap before melt down.
In the process of melting down, if the oxide is exposed to the atmosphere at high temperature, there will be some losses due to vaporiza-tion of the molybdenum oxide. After melt down the final adjustments to the molybdenum level in t~.e alloy steel are made using ferromolybdenum.
This is because ferromolybdenum has no detrimental effect on either the bath oxygen or carbon level as would occur if molybdenum oxide alone were used. In addition, the use of ferromolybdenum increases the rate of dissolution and bath homogenization and minimizes loss of volatilization.
It would be desirable to use a ferromolybdenum product for all alloying purposes in steel for the above reasons, but the high cost of ferromolybdenum produced by the thermite process ha prevented its general use. If a more economical method of production could be found, the above mentioned advantages could be utilized for all stages of the steelmaking proces~.
The term " lybdenum oxide" or "molybdenum oxides" as used herein-after is defined as technical grade molybdenum trioxide (MoO3) containing inconsequential trace impurities and minor amounts of molybdenum sesqui-oxide (Mo203) and molybdenum dioxide (MoO2). It is to be understood, however, that molybdenum trioxide of any purity may be used in the process to make the novel product.
The novel lybdenum product, for use in the alloying of steel, is made by a novel process in which molybdenum oxide is stepwise reduced to molybdenum dioxide and then to molybdenum metal by hydrogen, reformed gas, or cracked NH3 reduction. The first temperature stage is carried
In the process of melting down, if the oxide is exposed to the atmosphere at high temperature, there will be some losses due to vaporiza-tion of the molybdenum oxide. After melt down the final adjustments to the molybdenum level in t~.e alloy steel are made using ferromolybdenum.
This is because ferromolybdenum has no detrimental effect on either the bath oxygen or carbon level as would occur if molybdenum oxide alone were used. In addition, the use of ferromolybdenum increases the rate of dissolution and bath homogenization and minimizes loss of volatilization.
It would be desirable to use a ferromolybdenum product for all alloying purposes in steel for the above reasons, but the high cost of ferromolybdenum produced by the thermite process ha prevented its general use. If a more economical method of production could be found, the above mentioned advantages could be utilized for all stages of the steelmaking proces~.
The term " lybdenum oxide" or "molybdenum oxides" as used herein-after is defined as technical grade molybdenum trioxide (MoO3) containing inconsequential trace impurities and minor amounts of molybdenum sesqui-oxide (Mo203) and molybdenum dioxide (MoO2). It is to be understood, however, that molybdenum trioxide of any purity may be used in the process to make the novel product.
The novel lybdenum product, for use in the alloying of steel, is made by a novel process in which molybdenum oxide is stepwise reduced to molybdenum dioxide and then to molybdenum metal by hydrogen, reformed gas, or cracked NH3 reduction. The first temperature stage is carried
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out at about 500 ~ 650C to reduce the molybdenum oxide to molybdenum dioxide. The final redu~tion of the molybdenum dioxide to molybdenum metal takes place in the second temperature zone at about 800 - 900C.
In another and more preferred embodiment, a novel ferromolybdenum product is made by the process of this invention by premixing molybdenum oxide and iron oxide. The mixture is then stepwise reduced such that in the first step essentially all of the molybdenum trioxide is reduced to molybdenum dioxide and little if any iron oxide is reduced. In the second step, at temperatures between about 800 - 900C, reduction of the molybdenum dioxide i9 completed to essentially all metallic molybdenum and essentially all of the iron oxide is reduced to metallic iron.
In yet another embodiment molybdenum oxide and iron particles are mixed. The mixture may then be stepwise reduced such that in the first step the molybdenum trioxide is reduced at temperatures of about 500 - 600C
to lybdenum dioxide. In the second step the molybdenum dioxide is reduced to metallic lybdenum at temperatures of between about 800 - 900C.
Since the iron is already in the metallic state no reduction thereof i8 required.
The lybdenum oxide, premixed molybdenum oxide/iron oxide, or premixed lybdenum oxide/iron charge is preferably in briquette form to facilitate handling and complete gaseous reduction. The gaseous reducing agent, preferably a hydrogen containing gas, is supplied to the two temperature zone furnace in a countercurrent fashion and at least a portion of the gaseous reducing agent is recycled for nearly complete utilization of reductant. It should be particularly pointed out that at no time during the processing do tbe molybdenum or iron melt. As a result the product contalns discrete or individually distinct particles of metal. The brlquetting provides only surface bonding for ease of handling the product.
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The metallized product may be crushed and briquetted to provide a surface bonded briquette having a specific gravity of between 4.5 - 7, which is sufficiently dense to enable penetration of steel making slags when making steel alloying additions.
The novel product of the instant invention may be in one or more forms. In one form the product consists essentially of a briquette of discrete or individually distinct particles of molybdenum metal. In another form the product consists essentially of a briquette of mixed discrete or individually distinct particles of molybdenum and iron. The lron may be from about 5 to about 70 or more weight percent of the briquette.
The final product contains less than about 7% by weight oxygen and is essentially carbon free.
Specifically, the present invention enables the economical product-tion of a metallized ferromolybdenum product which displays excellent properties for purposes of making steel alloying additions. The reduction of oxides takes place in the process without carbon and other harmful contaminants entering the product, and ultimately ending up in the alloy steel. Further, the oxygen content, which can change the carbon level in lten steel by reacting to form carbon monoxide, is diminished to below 7% in the reduction. ~inally, the process takes place at moderately low temperatures and hence does not involve high temperature, high cost melting and alloying of molybdenum and iron.
The present invention provides a method whereby molybdenum in its higher oxidation states may be economically reduced to a metallic product without contamination by carbonaceous materials.
The invention further provides a metallized ferromolybdenum product of individually distinct particles loosely bonded that is suitable for use as an alloying addi~ive in steel.
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, ~ ' '' ' ' ' ' ; , The invention al~o provide~ a carbon free metallized molybdenum product, containing less than 7% 2~ and sufficiently den~e to penetrate steel making slags when making molybdenum alloying additions to steel.
FIG. 1 is a diagrammatic view showing steps of the method;
FIG. 2 is a graph showing the rate of reduction of molybdenum oxide and mixtures of molybdenum oxide and iron oxide.
Referring to Figure 1, the raw materials, in this ~llustration molybdenum oxide and iron oxide, are blended together with water and briquetted prior to introduction into the kiln. Zone I is operated at about 500 - 650C, which is sufficient to cause the reduction of the molybdenum trioxide to molybdenum dioxide, in the presence of a reducing gas such as hydrogen or carbon monoxide. The solids 11, an intermediate product consisting essentially of molybdenum dioxide (and unreduced iron oxides), move from Zone I into Zone II of the kiln where the temperature i8 maintained between sbout 800 - 900C. In Zone II both molybdenum dioxide and the iron oxides in the intermediate product are reduced to provide a metalllzed product 13 containing a minimum amount of oxygen and i8 essentially carbon free. The metallized product 13 exits from the kiln and may subsequently be mechanically crushed and briquetted to form the final product, which i~ a surface bonded briquette of particulate metallic lybdenum with up to about 30 weight percent or more metallic iron particles, having a specific gravity of 4.5 - 7, essentially carbon free, and contain-lng less than 7% oxygen.
The preferred reductant is hydrogen, which can be introduced as hydrogen per se or in the form of dissociated ammonia. The fresbly dis-sociated ammonia, or make-up reductant 3, is combined with a stream of recycled gas reductant 5 and the two streams together enter the kiln as .,. . ,,, , . , , . ,, . , , i , , , , , :, ., -', ' " ',', ', "'''~' ~"'''''', ' ' ,' '"",' ,., the reduction gas feed stream 9. The freshly dissociated ammonia i8~
of course, a constant 25% by volume nitrogen, and 75% by volume hydrogen, so that the total feed stream 9 content is dependent on the composition of recycled gaseous reductant 5 and the volume ratio of recycle gas to make-up gas. These reductant volume considerations are critical in the present invention for purposes of effecting essentially complete utiliza-tion of available reductant for each specific molybdenum oxide/iron oxide charge composition.
The feed gas reductant 9 enters downstream to the solid~ flow 13 and makes it way countercurrent through Zone II. A portion 15 of the gas leaving Zone II i8 recycled around Zone II continues into Zone I to reduce the molybdenum oxide to molybdenum dioxide. ~he overall reaction in Zone I is exothermic and is completed very quickly. As a result, the reductant in this zone does not necessarily need to be passed counter-currently to the solids flow. In the present process, however, it i8 convenient to pass the gas countercurrent in Zone I as it exits from Zone II. The Zone II endothermic reduction of molybdenum dioxide to its metallic state is much more difficult than the trioxide reduction of Zone I, and hence the countercurrent reductant flow is desirable to effect maximum driving force for completion of the reaction.
Referring to Figure 2 there is shown a plot of time versus the percent weight 1088 at two reduction temperatures and two compositions.
The horizontal broken lines A, B and C represent theoretical weight 1088 for: A - Pure lybdenumtrioxide, B - technical grade molybdenum trioxide, and C - technical grade molybdenum trioxide containing sufficient lron oxide to result in a product containing 30 weight per-cent iron.
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The starting materials may be less than 100% pure metal oxide~ -The process is particularly attractive for the use of technical grade molybdenum oxide. Any impurities, including unreduced oxides, merely pass through the process without significant effect on the efficiency of the process or the yield of the final product. This is largely true because of the relatively low temperatures used in the process. At higher temperatures sintering would have the ill effect of hindering complete reduction by blocking the path of gaseous reductant to the inner regions of the briquette. The low temperatures employed in the process do not present this problem. The impurity limits tolerable in the raw materials, therefore, would be dictated only by the end product require-ments.
The process is useful in the reduction of molybdenum oxides alone or in the reduction of molybdenum oxides mixed with iron oxides. The presence of the latter is desirable if the end product is to be used as an alloying addition in steels. Among other things the process is unique in providing a product containing both molybdenum and iron obtained by the slmultaneous reduction of both molybdenum oxide and iron oxide rather than by the mere blendlng of metalllc iron with a reduced molybdenum product - -as is described in U. S. Patent No. 2,302,615. In the present invention, the process is adaptable to meet the presence of iron oxides in terms of thermodynamic considerations and volume of reductant supplied. The basic parameters, which may be ad~usted to provide for a change in the composition of the oxide charge, are the temperature of the kiln zones and the volume ratio (at steady state) of the recycled ga~ retuctant to make-up gas.
In orter to prevent the reoxidation of the pure metallic molybdenum briquette once a steel alloying addition is made, it is desirable that '" '', ., ,, ',", ", .' . ,'" ', ~ ' ' ; ' ~ '",; '; ' ,'' " ' . .,, ,, ' ' ' ~ ' ' ' ~,:, , ,',,-'", ~, ',' .' ' ': ' ' . ' ' '' " ,,, j , , : , , .. . . .. . .
""" "~ "~""~w~fr~i~if; ~
the molybdenum be dissolved as quickly as possible in the ~teel melt.
To accomplish this quick dissolution, a quantity of iron is introduced with the molybdenum into the steel melt. Dissolution in the ~teel melt is relatively rapid since the novel product of this invention is a loosely surface bonded briquette of discrete pa~ticles of metallic molybdenum and iron.
In the final metallized ferromolybdenum alloying agent, a quantity of iron in excess of 15% has been found to be beneficial. Specifically, an iron concentration in excess of 15% in the briquette product has the effect of promoting rapid dissolution of molybdenum in the steel melt and contributing to a very hlgh recovery of molybdenum in the cast alloy steel. The iron so provided is sufficient to ensure that all the molybdenum present will dissolve at steel making temperatures without the formation of high melting point phases as the briquette disintegrates in the melt. The advantage of supplying sufficient iron in the briquette for complete, rapid dissolution of the molybdenum i9 the avoidance of both reoxitation and 1098 of lybdenum in the slag, and the ~ettling out of heavy refractory molybdenum bearing compounds at the bottom of the vesRel which might cause problems with subsequent heats.
In carrying out the process of the present invention, we have found that several novel products may be produced which are particularly u~eful as alloying additions in the preparation of alloy steels. The present process is adaptable to provide for the production of these various products. ~or example, the temperature and gas reductant levels may be altered to provide for the reduction of 100% molybdenum oxide starting material or mixture of molybdenum oxide and iron or iron oxides in any desired proportions. A practical limlt is up to 70% iron oxide in the ~tartlng material. The reduction may al~o be carried ou~ in rotary ~- ' , , ,: " ",., ,:,, ~,,: ,~,., . ' ' lf;~ 4~
kilns, belt furnaces, or fluidized beds, as long as the temperature stages and gas recycling are maintained. We have found that the presence of a 30 weight percent iron addition decreases the reduction time relative to molybdenum oxide alone by 40% with consequent advantages in reducing the size of the equipment.
In Zone I the molybdenum oxide is reduced to molybdenum dioxide between about 500 - 650C. At temperatures in excess of 650C molybdenum trioxide is known to volatili~e. For this reason the first stage of the process is carried out below 650C. At this temperature the iron oxides are not appreciably reduced to lower oxides or iron metal.
If acceptable utilizations of the hydrogen gas are to be realized, thermodynamic considerations in the reduction of molybdenum dioxide in the second sta8e requires that the reaction be carried out at higher temperatures than in the first stage. The greatest improvement occurs when the temperature i9 raised to at least 800C with less significant benefit occurring above 900C. In addition, increasing the temperature has a marked effect on the rate of reduction, the time required being reduced by a factor of three when the temperature is raised from 800 to 900C. ~igure 2 illustrates this. Equipment design considerations and energy requirements preclude using much higher temperatures, 80 that ~ -800 - 900C is con~idered an optimum compromise, though lower or higher temperatures could still be used to achieve the same results in terms of the products produced. The relatively low temperature processing in the present invention is an essential feature of the process of the present invention. We have been able to produce a ferromolybdenum product from iron and molybdenum oxides without fuslng at the high temperatures used ln conventional ferromolybdenum production. Instead, we are able to co-reduce the oxides at temperatures not in excess of 900C. ~ -_ g ~ .-,, ' ,'' ' ' ,' ' ';'. ,', " ', ~ "',, : "" ' ,' lr3~
Reductant In practicing the present process, hydrogen gas has been found to be the most suitable reductant, although other gaseous reductants such as carbon monoxide or reformed hydrocarbons may be used. We prefer that the hydrogen source be cracked ammonia because of itq low cost. The feed gas 9, (recycled plus make-up), will be about 50% H2/50% N2 depending on the proportion of iron oxide in the starting material. Overall, the feed requirements are calculated on a stoichiometric basis for the completion of the reduction reactions, and sufficient make-up gas is supplied to the recycle stream to meet the stoichiometric requirements and the furnace losses.
The reductant gas feed 9 to Zone II must be such that the ratio of hydrogen to water vapor required from thermodynamic considerations for completion of the reduction is maintained, in addition to providing sufficient hydrogen as required by the reaction stoichiometrics.
The Zone I reaction is not appreciably altered by the partial pressure of hydrogen to partial pressure of water vapor ratio, and no ad~u~tment in the stoichiometric calculations need be made with respect to the reductant requirementq for Zone I. Therefore, for maximum utiliza-tion of reductant only enough reductant to complete the molybdenum tri-oxide reduction to molybdenum dioxide i~ allowed to enter countercurrent-ly into Zone I. The remaining gas 15 from Zone II is recycled through a conden~er to re ve the water therefrom and feed back 5 to the feed stream 9 for Zone II. It is necessary to condense and remove water from the recycle gas since the effect of the water vapor pressure on the reductlon rate 18 negative in Zone II.
The Novel Metallized Products The preferred product for alloying of ferrous metals is produced " ,: ' ~ , " '' , ,, ,, , , .," ' ,, , , , , ,, , , , : , , ,, , " ~, , ; ,, .
4~36 in the novel process from technical grade molybdenum trioxide and a mixture of iron oxides such that the iron content of the product is between 0-30 weight %. The molybdenum oxide and iron oxide are co-reduced to pro-duce the desired metallized product. While 30 weight ~ is the prefer~ed limit on iron oxide in the batch charge, the amount of iron is not restricted to this by the process. The product is characterized by being a loosely bonded, preferably surface bonded only, briquette of discrete or individually distinct particles of reduced metal and will contain less than 7% by weight oxygen and be essentially carbon free.
We prefer that the product be a briquetted mixture of co-reduced metallic particles of molybdenum and iron. The novel process, however, is entirely suitable for reduction of molybdenum trioxide alone, or molybdenum oxide mixed with iron, which can be later briquetted and u~ed directly a6 an alloying agent.
Finally, the process is adaptable to be used in producing a metallized ferromolybdenum product from the mixed sulfides of lybdenum and iron. In a prior roasting step, the MoS2 and FeS2 (pyrite) may be co-roasted to yield mixed oxides which are then briquetted and charged directly in Zone I of the furnace of the novel process. This additional step in the process is particularly attractive from an economic stand-point because the metal sulfides are generally the least expensive source of lybdenum and iron. The process produces a metallized ferromolybdenum product from these crude raw materials with essentially complete utiliza-tion of reductant.
We have found in practicing the process of the present invention that the phys1cal form of oxide charge is important. Preferably the ~tarting material~ wlll be particulates in the size range from about --mlnu~ 20 to about mlnus 325 mesh. Table II below presents a typical size - . . . .. . . . ... . .. .. . .
,: , " , ; .,, ., "' ,. , ' .,,, , . :, , , distribution range for technical grade molybdenum trioxide, Iron oxide particles should be within same general slze range. The reduction steps, for example, may be carried out in shallow beds of oxide po~ders but unreacted core and handling problems may decrease the gas utilization efficiency of the process. We, therefore, prefer that the molybdenum and iron oxides be blended with water and briquetted prior to reduction.
Around 3% water has been found sufficient for making the green briquettes for feeding to Zone I reduction. This form allows the reducing gas to effectively reach the entire volume of material.
After reduction, the metallized product may be rather porous so that crushing and rebriquetting is necessary to densify the material for subsequent use. Molybdenum alloying additions to molten steels must sink through the steel slags which float on the surface of the molten metal. These slags have specific gravities in the range of 3 - 3.5 80 that the metallized product must be compacted to a specific gravity in excess of 3.5 in order to penetrate the layer of slag. To accomplish this, we have found that the metallized ferromolybdenum product of the inventive process may be crushed and briquetted to a specific gravity of between about 4.5 and 7. A metallized ferromolybdenum briquette compacted to 4.5 - 7 specific gravity is entlrely suitable for the alloying addition and results in high yields in the steel. The higher density of the briquette enables it to penetrate the steel slag and be delivered to the molten steel while the iron enables the molybdenum to dissolve easily in the molten metal. While it is apparent that higher density briquettes could be obtained it is preferable to not exceed a specific gravity of 7. With applicants' novel product 100% of the reduced molybdenum in the briquette i8 recovered in the steel rather than a significant proportion being lo~t in the slag.
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The metallized ferromolybdenum product need not be 100% reduced for use in the steel alloying process. With almost 100% utilization of reducing gas, some oxygen may necessarily remain in the product. The quantity of oxygen associated with the molybdenum and iron in the product, however, will always be less than about 7 and preferably in the range of 0-2% by weight.
Without limiting the above described process, the following examples are illustrative of the features of the inventlon.
Example I
Reduction of Molybdenum Oxide to Metallized Product Molybdenum oxide (technical grade molybdenum trioxide) is briquetted and charged to the low temperature end of a moving grate kiln operated at distinct temperature zones of about 500C and about 900C.
The assay and size distributions of the molybdenum oxide are shown in Tables I and II. The speed of the moving grate kiln is set 80 that the briquettes will be totally reduced during the passage of the molybdenum oxide therethrough. This usually takes place when the oxide ha been in the hot zones for 4-5 hours.
! Table I
Assay of Molybdenum Oxide --Molybdenum Iron Copper Lead Sulfur Oxygen wt. % wt. % wt. % wt.% wt. % wt. %
58-62 1 0.4-0.8 0.015-0.030 0.04-0.2 29-31 ,, ~, . ,, ,, ',, ,,, :, , Table II
Size Distribution of Mol~bdenum Oxide Screen Size % Retained -20 + 30 2.14 -30 + 60 17.38 -60 + 80 18.56 -80 + 120 22.30 -120 + 140 10.53 -140 + 170 3.24 -170 + 230 8.49 -230 + 270 2.32 -270 + 325 7.08 -325 7.96 The reducing gas, dissociated ammonia, is passed countercurrent to the solids flow. The feed stream of dissociated ammonia enter~ at a rate of around two moles ammonia for each le of molybdenum to be reduced.
After the reductant passes through Zone II at about 900C, a bleed stream removes all but one le of hydrogen for each mole of molybdenum trioxide to be reduced according to the reaction MoO3 + H2 ~ MO2 + H20 (1) The remaining reductant from Zone II is recycled through a condenser to remove the water and then back into the feed stream. The recycle portion brlngs the overall feed composition to 50~ H2/50% N2. In the process approximately ten les H2 + N2 are recycled when the reaction reaches eteady 8tate. This results in a hydrogen efficiency approaching 100%
tl8counting leakage losses.
The molybtenum oxide i~ reduced completely in Zone I to molybdenum dioxide whlch 18 further reduced to lybdenum metal in Zone II. Oxygen ' '- ' ' .
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in the final product i9 no more than 1-2% aY determined by the ~oTnparison of the actual weight loss with that calculated from the lybdenum content.
It is calculated that no more than about 0.32 lb. of NH3 i~ used for every pound of molybdenum metal produced. This compares with 0.83 lb. NH3/lb.
molybdenum with no recycling of hydrogen. The rate of weight 1088 for Examples I and II are shown in Figure 2. For comparison, the rate of weight loss is shown for the same materials at about 800C. The expected weight loss is also shown (broken line A) based on an initial molybdenum content of 60 wt.%, as analyzed for this particular batch of material, and 10 assuming that the only oxygen present was as molybdenum trioxide. It can be seen that at about 900C the weight losses were slightly higher than calculated and may be attributed to the reduction of oxides of the other metals present as minor impurities.
l~xale II
Co-Reduction of Iron Oxides and Molybdenum Oxide -~
The process of Example I was followed butwithmillscale blended and briquetted with the lybdenum oxide such that ~he product would contain 30 wt.% iron after reduction. (Millscale ~ PeO 60-70 wt.%, Fe203 25-30 wt.%, Fe304 5-10 wt.%, by x-ray analysis overall composition 20 FeOl 2 by hydrogen reduction). The briquettes measured about 1/2" in diameter and 1/2" long and weighet 5 grams each. Furnace temperature in Zone I remained at about 600C but the dissociated ammonia feed was increased to 2.6 les per mole molybdenum. Again one mole N2 per le molybdenum was allowed to proceed from Zone II into Zone I and the remaining 9.8 moles N2 + H3 (at steady state) were recycled through the contenser and lnto the dissociated ammonia feed stream. Overall feed composition ~recycle plus make-up) was 56.4% N2t43.6% H2 and 0.42 lb. of a~onia was u~et for every pound of molybdenum metal reduced. The .
'""' '' ' '."' "'" ,"'' ',,' , ', ,",'' ~' ,'.,~ ' ',' ' ', ';''"'' ', ' " ' ' ' . ,', ' '' ' ', ' ' , ' ' ' , ',, ' ' ' ' ' ' " , ''' '" ,' , ,' " ', ' ,,, " , ' ' ,, , ' : " . . . .
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Table III
Density of Process Materials Material Specific Gravity Molybdenum Oxide (technical grade molybdenum trioxide) 2.2 Millscale l.9 Green Pellet 3.6 'MoO2' Pellet 2.3 Mo -Pe Pellet (30 wt.%) 2.3 Mo -Pe Powder (30 wt.%~ 1.7 Recompacted Mo - Fe (30 wt,%) 4.5 Recompacted Mo 4.3 to 7.2 Example III
Effect of Recycle Ratio around Zone II on Hydrogen Efficiency Using the process of Example II, again wlth the millscale addition for 30 wt.% iron in the product, the materials were blended and briquetted.
(The flow diagram for the process is shown in Pigure 1). Various quantities of reducing gas were then recycled around Zone II in different test runs to determine the effect of utilization of reductant or hydrogen efficiency.
In tabular form (Table IV), the results are shown of varying the recycle ratios on the basis of complete reduction of one mole of molybdenum plus 30 wt.~ iron. --.. . .. .... .. . . . . .
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Table IV
Hydrogen Utilization Efficiency as ~unction of Recycle Ratio Feed to ~eed Hydrogen Overall ~eed Recycle Zone I Make-Up Efficiency Compo~ition N2~H2 N2+H2 H2 NH3 Moles % %N2t%H2 Moles Moles Moles 0 8.0 5.27 5.43 47.7 34/66
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out at about 500 ~ 650C to reduce the molybdenum oxide to molybdenum dioxide. The final redu~tion of the molybdenum dioxide to molybdenum metal takes place in the second temperature zone at about 800 - 900C.
In another and more preferred embodiment, a novel ferromolybdenum product is made by the process of this invention by premixing molybdenum oxide and iron oxide. The mixture is then stepwise reduced such that in the first step essentially all of the molybdenum trioxide is reduced to molybdenum dioxide and little if any iron oxide is reduced. In the second step, at temperatures between about 800 - 900C, reduction of the molybdenum dioxide i9 completed to essentially all metallic molybdenum and essentially all of the iron oxide is reduced to metallic iron.
In yet another embodiment molybdenum oxide and iron particles are mixed. The mixture may then be stepwise reduced such that in the first step the molybdenum trioxide is reduced at temperatures of about 500 - 600C
to lybdenum dioxide. In the second step the molybdenum dioxide is reduced to metallic lybdenum at temperatures of between about 800 - 900C.
Since the iron is already in the metallic state no reduction thereof i8 required.
The lybdenum oxide, premixed molybdenum oxide/iron oxide, or premixed lybdenum oxide/iron charge is preferably in briquette form to facilitate handling and complete gaseous reduction. The gaseous reducing agent, preferably a hydrogen containing gas, is supplied to the two temperature zone furnace in a countercurrent fashion and at least a portion of the gaseous reducing agent is recycled for nearly complete utilization of reductant. It should be particularly pointed out that at no time during the processing do tbe molybdenum or iron melt. As a result the product contalns discrete or individually distinct particles of metal. The brlquetting provides only surface bonding for ease of handling the product.
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The metallized product may be crushed and briquetted to provide a surface bonded briquette having a specific gravity of between 4.5 - 7, which is sufficiently dense to enable penetration of steel making slags when making steel alloying additions.
The novel product of the instant invention may be in one or more forms. In one form the product consists essentially of a briquette of discrete or individually distinct particles of molybdenum metal. In another form the product consists essentially of a briquette of mixed discrete or individually distinct particles of molybdenum and iron. The lron may be from about 5 to about 70 or more weight percent of the briquette.
The final product contains less than about 7% by weight oxygen and is essentially carbon free.
Specifically, the present invention enables the economical product-tion of a metallized ferromolybdenum product which displays excellent properties for purposes of making steel alloying additions. The reduction of oxides takes place in the process without carbon and other harmful contaminants entering the product, and ultimately ending up in the alloy steel. Further, the oxygen content, which can change the carbon level in lten steel by reacting to form carbon monoxide, is diminished to below 7% in the reduction. ~inally, the process takes place at moderately low temperatures and hence does not involve high temperature, high cost melting and alloying of molybdenum and iron.
The present invention provides a method whereby molybdenum in its higher oxidation states may be economically reduced to a metallic product without contamination by carbonaceous materials.
The invention further provides a metallized ferromolybdenum product of individually distinct particles loosely bonded that is suitable for use as an alloying addi~ive in steel.
.
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, ~ ' '' ' ' ' ' ; , The invention al~o provide~ a carbon free metallized molybdenum product, containing less than 7% 2~ and sufficiently den~e to penetrate steel making slags when making molybdenum alloying additions to steel.
FIG. 1 is a diagrammatic view showing steps of the method;
FIG. 2 is a graph showing the rate of reduction of molybdenum oxide and mixtures of molybdenum oxide and iron oxide.
Referring to Figure 1, the raw materials, in this ~llustration molybdenum oxide and iron oxide, are blended together with water and briquetted prior to introduction into the kiln. Zone I is operated at about 500 - 650C, which is sufficient to cause the reduction of the molybdenum trioxide to molybdenum dioxide, in the presence of a reducing gas such as hydrogen or carbon monoxide. The solids 11, an intermediate product consisting essentially of molybdenum dioxide (and unreduced iron oxides), move from Zone I into Zone II of the kiln where the temperature i8 maintained between sbout 800 - 900C. In Zone II both molybdenum dioxide and the iron oxides in the intermediate product are reduced to provide a metalllzed product 13 containing a minimum amount of oxygen and i8 essentially carbon free. The metallized product 13 exits from the kiln and may subsequently be mechanically crushed and briquetted to form the final product, which i~ a surface bonded briquette of particulate metallic lybdenum with up to about 30 weight percent or more metallic iron particles, having a specific gravity of 4.5 - 7, essentially carbon free, and contain-lng less than 7% oxygen.
The preferred reductant is hydrogen, which can be introduced as hydrogen per se or in the form of dissociated ammonia. The fresbly dis-sociated ammonia, or make-up reductant 3, is combined with a stream of recycled gas reductant 5 and the two streams together enter the kiln as .,. . ,,, , . , , . ,, . , , i , , , , , :, ., -', ' " ',', ', "'''~' ~"'''''', ' ' ,' '"",' ,., the reduction gas feed stream 9. The freshly dissociated ammonia i8~
of course, a constant 25% by volume nitrogen, and 75% by volume hydrogen, so that the total feed stream 9 content is dependent on the composition of recycled gaseous reductant 5 and the volume ratio of recycle gas to make-up gas. These reductant volume considerations are critical in the present invention for purposes of effecting essentially complete utiliza-tion of available reductant for each specific molybdenum oxide/iron oxide charge composition.
The feed gas reductant 9 enters downstream to the solid~ flow 13 and makes it way countercurrent through Zone II. A portion 15 of the gas leaving Zone II i8 recycled around Zone II continues into Zone I to reduce the molybdenum oxide to molybdenum dioxide. ~he overall reaction in Zone I is exothermic and is completed very quickly. As a result, the reductant in this zone does not necessarily need to be passed counter-currently to the solids flow. In the present process, however, it i8 convenient to pass the gas countercurrent in Zone I as it exits from Zone II. The Zone II endothermic reduction of molybdenum dioxide to its metallic state is much more difficult than the trioxide reduction of Zone I, and hence the countercurrent reductant flow is desirable to effect maximum driving force for completion of the reaction.
Referring to Figure 2 there is shown a plot of time versus the percent weight 1088 at two reduction temperatures and two compositions.
The horizontal broken lines A, B and C represent theoretical weight 1088 for: A - Pure lybdenumtrioxide, B - technical grade molybdenum trioxide, and C - technical grade molybdenum trioxide containing sufficient lron oxide to result in a product containing 30 weight per-cent iron.
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The starting materials may be less than 100% pure metal oxide~ -The process is particularly attractive for the use of technical grade molybdenum oxide. Any impurities, including unreduced oxides, merely pass through the process without significant effect on the efficiency of the process or the yield of the final product. This is largely true because of the relatively low temperatures used in the process. At higher temperatures sintering would have the ill effect of hindering complete reduction by blocking the path of gaseous reductant to the inner regions of the briquette. The low temperatures employed in the process do not present this problem. The impurity limits tolerable in the raw materials, therefore, would be dictated only by the end product require-ments.
The process is useful in the reduction of molybdenum oxides alone or in the reduction of molybdenum oxides mixed with iron oxides. The presence of the latter is desirable if the end product is to be used as an alloying addition in steels. Among other things the process is unique in providing a product containing both molybdenum and iron obtained by the slmultaneous reduction of both molybdenum oxide and iron oxide rather than by the mere blendlng of metalllc iron with a reduced molybdenum product - -as is described in U. S. Patent No. 2,302,615. In the present invention, the process is adaptable to meet the presence of iron oxides in terms of thermodynamic considerations and volume of reductant supplied. The basic parameters, which may be ad~usted to provide for a change in the composition of the oxide charge, are the temperature of the kiln zones and the volume ratio (at steady state) of the recycled ga~ retuctant to make-up gas.
In orter to prevent the reoxidation of the pure metallic molybdenum briquette once a steel alloying addition is made, it is desirable that '" '', ., ,, ',", ", .' . ,'" ', ~ ' ' ; ' ~ '",; '; ' ,'' " ' . .,, ,, ' ' ' ~ ' ' ' ~,:, , ,',,-'", ~, ',' .' ' ': ' ' . ' ' '' " ,,, j , , : , , .. . . .. . .
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the molybdenum be dissolved as quickly as possible in the ~teel melt.
To accomplish this quick dissolution, a quantity of iron is introduced with the molybdenum into the steel melt. Dissolution in the ~teel melt is relatively rapid since the novel product of this invention is a loosely surface bonded briquette of discrete pa~ticles of metallic molybdenum and iron.
In the final metallized ferromolybdenum alloying agent, a quantity of iron in excess of 15% has been found to be beneficial. Specifically, an iron concentration in excess of 15% in the briquette product has the effect of promoting rapid dissolution of molybdenum in the steel melt and contributing to a very hlgh recovery of molybdenum in the cast alloy steel. The iron so provided is sufficient to ensure that all the molybdenum present will dissolve at steel making temperatures without the formation of high melting point phases as the briquette disintegrates in the melt. The advantage of supplying sufficient iron in the briquette for complete, rapid dissolution of the molybdenum i9 the avoidance of both reoxitation and 1098 of lybdenum in the slag, and the ~ettling out of heavy refractory molybdenum bearing compounds at the bottom of the vesRel which might cause problems with subsequent heats.
In carrying out the process of the present invention, we have found that several novel products may be produced which are particularly u~eful as alloying additions in the preparation of alloy steels. The present process is adaptable to provide for the production of these various products. ~or example, the temperature and gas reductant levels may be altered to provide for the reduction of 100% molybdenum oxide starting material or mixture of molybdenum oxide and iron or iron oxides in any desired proportions. A practical limlt is up to 70% iron oxide in the ~tartlng material. The reduction may al~o be carried ou~ in rotary ~- ' , , ,: " ",., ,:,, ~,,: ,~,., . ' ' lf;~ 4~
kilns, belt furnaces, or fluidized beds, as long as the temperature stages and gas recycling are maintained. We have found that the presence of a 30 weight percent iron addition decreases the reduction time relative to molybdenum oxide alone by 40% with consequent advantages in reducing the size of the equipment.
In Zone I the molybdenum oxide is reduced to molybdenum dioxide between about 500 - 650C. At temperatures in excess of 650C molybdenum trioxide is known to volatili~e. For this reason the first stage of the process is carried out below 650C. At this temperature the iron oxides are not appreciably reduced to lower oxides or iron metal.
If acceptable utilizations of the hydrogen gas are to be realized, thermodynamic considerations in the reduction of molybdenum dioxide in the second sta8e requires that the reaction be carried out at higher temperatures than in the first stage. The greatest improvement occurs when the temperature i9 raised to at least 800C with less significant benefit occurring above 900C. In addition, increasing the temperature has a marked effect on the rate of reduction, the time required being reduced by a factor of three when the temperature is raised from 800 to 900C. ~igure 2 illustrates this. Equipment design considerations and energy requirements preclude using much higher temperatures, 80 that ~ -800 - 900C is con~idered an optimum compromise, though lower or higher temperatures could still be used to achieve the same results in terms of the products produced. The relatively low temperature processing in the present invention is an essential feature of the process of the present invention. We have been able to produce a ferromolybdenum product from iron and molybdenum oxides without fuslng at the high temperatures used ln conventional ferromolybdenum production. Instead, we are able to co-reduce the oxides at temperatures not in excess of 900C. ~ -_ g ~ .-,, ' ,'' ' ' ,' ' ';'. ,', " ', ~ "',, : "" ' ,' lr3~
Reductant In practicing the present process, hydrogen gas has been found to be the most suitable reductant, although other gaseous reductants such as carbon monoxide or reformed hydrocarbons may be used. We prefer that the hydrogen source be cracked ammonia because of itq low cost. The feed gas 9, (recycled plus make-up), will be about 50% H2/50% N2 depending on the proportion of iron oxide in the starting material. Overall, the feed requirements are calculated on a stoichiometric basis for the completion of the reduction reactions, and sufficient make-up gas is supplied to the recycle stream to meet the stoichiometric requirements and the furnace losses.
The reductant gas feed 9 to Zone II must be such that the ratio of hydrogen to water vapor required from thermodynamic considerations for completion of the reduction is maintained, in addition to providing sufficient hydrogen as required by the reaction stoichiometrics.
The Zone I reaction is not appreciably altered by the partial pressure of hydrogen to partial pressure of water vapor ratio, and no ad~u~tment in the stoichiometric calculations need be made with respect to the reductant requirementq for Zone I. Therefore, for maximum utiliza-tion of reductant only enough reductant to complete the molybdenum tri-oxide reduction to molybdenum dioxide i~ allowed to enter countercurrent-ly into Zone I. The remaining gas 15 from Zone II is recycled through a conden~er to re ve the water therefrom and feed back 5 to the feed stream 9 for Zone II. It is necessary to condense and remove water from the recycle gas since the effect of the water vapor pressure on the reductlon rate 18 negative in Zone II.
The Novel Metallized Products The preferred product for alloying of ferrous metals is produced " ,: ' ~ , " '' , ,, ,, , , .," ' ,, , , , , ,, , , , : , , ,, , " ~, , ; ,, .
4~36 in the novel process from technical grade molybdenum trioxide and a mixture of iron oxides such that the iron content of the product is between 0-30 weight %. The molybdenum oxide and iron oxide are co-reduced to pro-duce the desired metallized product. While 30 weight ~ is the prefer~ed limit on iron oxide in the batch charge, the amount of iron is not restricted to this by the process. The product is characterized by being a loosely bonded, preferably surface bonded only, briquette of discrete or individually distinct particles of reduced metal and will contain less than 7% by weight oxygen and be essentially carbon free.
We prefer that the product be a briquetted mixture of co-reduced metallic particles of molybdenum and iron. The novel process, however, is entirely suitable for reduction of molybdenum trioxide alone, or molybdenum oxide mixed with iron, which can be later briquetted and u~ed directly a6 an alloying agent.
Finally, the process is adaptable to be used in producing a metallized ferromolybdenum product from the mixed sulfides of lybdenum and iron. In a prior roasting step, the MoS2 and FeS2 (pyrite) may be co-roasted to yield mixed oxides which are then briquetted and charged directly in Zone I of the furnace of the novel process. This additional step in the process is particularly attractive from an economic stand-point because the metal sulfides are generally the least expensive source of lybdenum and iron. The process produces a metallized ferromolybdenum product from these crude raw materials with essentially complete utiliza-tion of reductant.
We have found in practicing the process of the present invention that the phys1cal form of oxide charge is important. Preferably the ~tarting material~ wlll be particulates in the size range from about --mlnu~ 20 to about mlnus 325 mesh. Table II below presents a typical size - . . . .. . . . ... . .. .. . .
,: , " , ; .,, ., "' ,. , ' .,,, , . :, , , distribution range for technical grade molybdenum trioxide, Iron oxide particles should be within same general slze range. The reduction steps, for example, may be carried out in shallow beds of oxide po~ders but unreacted core and handling problems may decrease the gas utilization efficiency of the process. We, therefore, prefer that the molybdenum and iron oxides be blended with water and briquetted prior to reduction.
Around 3% water has been found sufficient for making the green briquettes for feeding to Zone I reduction. This form allows the reducing gas to effectively reach the entire volume of material.
After reduction, the metallized product may be rather porous so that crushing and rebriquetting is necessary to densify the material for subsequent use. Molybdenum alloying additions to molten steels must sink through the steel slags which float on the surface of the molten metal. These slags have specific gravities in the range of 3 - 3.5 80 that the metallized product must be compacted to a specific gravity in excess of 3.5 in order to penetrate the layer of slag. To accomplish this, we have found that the metallized ferromolybdenum product of the inventive process may be crushed and briquetted to a specific gravity of between about 4.5 and 7. A metallized ferromolybdenum briquette compacted to 4.5 - 7 specific gravity is entlrely suitable for the alloying addition and results in high yields in the steel. The higher density of the briquette enables it to penetrate the steel slag and be delivered to the molten steel while the iron enables the molybdenum to dissolve easily in the molten metal. While it is apparent that higher density briquettes could be obtained it is preferable to not exceed a specific gravity of 7. With applicants' novel product 100% of the reduced molybdenum in the briquette i8 recovered in the steel rather than a significant proportion being lo~t in the slag.
,, ,:, ,,, ,,,, , " ",, ,,, , ', ,, ,';, " , ,', ,, ,, '' ', ;,' ' ' ', , , , :
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The metallized ferromolybdenum product need not be 100% reduced for use in the steel alloying process. With almost 100% utilization of reducing gas, some oxygen may necessarily remain in the product. The quantity of oxygen associated with the molybdenum and iron in the product, however, will always be less than about 7 and preferably in the range of 0-2% by weight.
Without limiting the above described process, the following examples are illustrative of the features of the inventlon.
Example I
Reduction of Molybdenum Oxide to Metallized Product Molybdenum oxide (technical grade molybdenum trioxide) is briquetted and charged to the low temperature end of a moving grate kiln operated at distinct temperature zones of about 500C and about 900C.
The assay and size distributions of the molybdenum oxide are shown in Tables I and II. The speed of the moving grate kiln is set 80 that the briquettes will be totally reduced during the passage of the molybdenum oxide therethrough. This usually takes place when the oxide ha been in the hot zones for 4-5 hours.
! Table I
Assay of Molybdenum Oxide --Molybdenum Iron Copper Lead Sulfur Oxygen wt. % wt. % wt. % wt.% wt. % wt. %
58-62 1 0.4-0.8 0.015-0.030 0.04-0.2 29-31 ,, ~, . ,, ,, ',, ,,, :, , Table II
Size Distribution of Mol~bdenum Oxide Screen Size % Retained -20 + 30 2.14 -30 + 60 17.38 -60 + 80 18.56 -80 + 120 22.30 -120 + 140 10.53 -140 + 170 3.24 -170 + 230 8.49 -230 + 270 2.32 -270 + 325 7.08 -325 7.96 The reducing gas, dissociated ammonia, is passed countercurrent to the solids flow. The feed stream of dissociated ammonia enter~ at a rate of around two moles ammonia for each le of molybdenum to be reduced.
After the reductant passes through Zone II at about 900C, a bleed stream removes all but one le of hydrogen for each mole of molybdenum trioxide to be reduced according to the reaction MoO3 + H2 ~ MO2 + H20 (1) The remaining reductant from Zone II is recycled through a condenser to remove the water and then back into the feed stream. The recycle portion brlngs the overall feed composition to 50~ H2/50% N2. In the process approximately ten les H2 + N2 are recycled when the reaction reaches eteady 8tate. This results in a hydrogen efficiency approaching 100%
tl8counting leakage losses.
The molybtenum oxide i~ reduced completely in Zone I to molybdenum dioxide whlch 18 further reduced to lybdenum metal in Zone II. Oxygen ' '- ' ' .
, , f~
in the final product i9 no more than 1-2% aY determined by the ~oTnparison of the actual weight loss with that calculated from the lybdenum content.
It is calculated that no more than about 0.32 lb. of NH3 i~ used for every pound of molybdenum metal produced. This compares with 0.83 lb. NH3/lb.
molybdenum with no recycling of hydrogen. The rate of weight 1088 for Examples I and II are shown in Figure 2. For comparison, the rate of weight loss is shown for the same materials at about 800C. The expected weight loss is also shown (broken line A) based on an initial molybdenum content of 60 wt.%, as analyzed for this particular batch of material, and 10 assuming that the only oxygen present was as molybdenum trioxide. It can be seen that at about 900C the weight losses were slightly higher than calculated and may be attributed to the reduction of oxides of the other metals present as minor impurities.
l~xale II
Co-Reduction of Iron Oxides and Molybdenum Oxide -~
The process of Example I was followed butwithmillscale blended and briquetted with the lybdenum oxide such that ~he product would contain 30 wt.% iron after reduction. (Millscale ~ PeO 60-70 wt.%, Fe203 25-30 wt.%, Fe304 5-10 wt.%, by x-ray analysis overall composition 20 FeOl 2 by hydrogen reduction). The briquettes measured about 1/2" in diameter and 1/2" long and weighet 5 grams each. Furnace temperature in Zone I remained at about 600C but the dissociated ammonia feed was increased to 2.6 les per mole molybdenum. Again one mole N2 per le molybdenum was allowed to proceed from Zone II into Zone I and the remaining 9.8 moles N2 + H3 (at steady state) were recycled through the contenser and lnto the dissociated ammonia feed stream. Overall feed composition ~recycle plus make-up) was 56.4% N2t43.6% H2 and 0.42 lb. of a~onia was u~et for every pound of molybdenum metal reduced. The .
'""' '' ' '."' "'" ,"'' ',,' , ', ,",'' ~' ,'.,~ ' ',' ' ', ';''"'' ', ' " ' ' ' . ,', ' '' ' ', ' ' , ' ' ' , ',, ' ' ' ' ' ' " , ''' '" ,' , ,' " ', ' ,,, " , ' ' ,, , ' : " . . . .
... .-.. . .. . . . ..
' ', ,,' ' , ' ', '' ,'' ', " '", ', ': ' densities of various process materials are shown in Table III.
Table III
Density of Process Materials Material Specific Gravity Molybdenum Oxide (technical grade molybdenum trioxide) 2.2 Millscale l.9 Green Pellet 3.6 'MoO2' Pellet 2.3 Mo -Pe Pellet (30 wt.%) 2.3 Mo -Pe Powder (30 wt.%~ 1.7 Recompacted Mo - Fe (30 wt,%) 4.5 Recompacted Mo 4.3 to 7.2 Example III
Effect of Recycle Ratio around Zone II on Hydrogen Efficiency Using the process of Example II, again wlth the millscale addition for 30 wt.% iron in the product, the materials were blended and briquetted.
(The flow diagram for the process is shown in Pigure 1). Various quantities of reducing gas were then recycled around Zone II in different test runs to determine the effect of utilization of reductant or hydrogen efficiency.
In tabular form (Table IV), the results are shown of varying the recycle ratios on the basis of complete reduction of one mole of molybdenum plus 30 wt.~ iron. --.. . .. .... .. . . . . .
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Table IV
Hydrogen Utilization Efficiency as ~unction of Recycle Ratio Feed to ~eed Hydrogen Overall ~eed Recycle Zone I Make-Up Efficiency Compo~ition N2~H2 N2+H2 H2 NH3 Moles % %N2t%H2 Moles Moles Moles 0 8.0 5.27 5.43 47.7 34/66
3.5~ 5.0 2.0 4.00 64.8 40/60 7.30 3.0 1.5 3.00 86.3 50/50 9.80 2.3 1.0 2.59 100.0 56.4/43.6 Example IV - -Recovery of Ferro lybdenum Product in Steel The ob~ect of the ferromolybdenum product i8 to provide a low cost means of adding molybdenum to steel with high yields and with a minimum of disturbance to the carbon level and to the oxygen balance in the lten steel bath.
A novel metallized molybdenum briquette containing 30 wt.% iron weighing about 15 grams was produced by the novel procesR in Example II.
Specific gravity of the briquette was 6.1. This briquette was then added to a 16 pound iron melt held in an inductlon furnace under an inert atmosphere. The iron melt had a basic steel slag on the surface and this was penetrated by the briquette. The melt was held for 30 minutes and then cast into lds. The ingots 80 produced were then Rampled by drilling holes at different points across the diame~er both at the top and bottom of the ingot. The drillings from across a given diameter were blended and analyzed for molybdenum. The results, given in Table V, show that the . .
l'3'~ 5 distribution of molybdenum was very uniform and that the recoveries were 100% for the reduced materials.
Table V
Distribution and Recovery of Molybdenum in Iron Ca~tin~s Input Output Molybdenum Molybdenum Concentration Recovery Iron + Contained in Casting Wt.% (Average) Molyb- Molyb-Run Iron denum denum Ingot No.* gm gm gm No. Top Bottom %
_ 2 7300 25.79 15.52 (1) 0.202 0.210 99 (2) 0.209 0.208 3 7300 17.8 15.52 (1) 0.209 0.209 100 (2) 0.209 0.208 7300 17.54 14.29 (1) 0.194 0.199 101 6 7300 34.27 21.23 (1) 0.289 0.288 100 * Runs 2, 6 used 30 wt.% iron briquet~es; Runs 3, 5 used reduced lybdenum oxide briquettes alone Without further analysis, the foregoing will 80 fully reveal tbe gist of the present invention that others can by applying current knowledge --readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations ~hould and are intended to be comprehended within the meaning ant range of equlvalence of the following claims.
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A novel metallized molybdenum briquette containing 30 wt.% iron weighing about 15 grams was produced by the novel procesR in Example II.
Specific gravity of the briquette was 6.1. This briquette was then added to a 16 pound iron melt held in an inductlon furnace under an inert atmosphere. The iron melt had a basic steel slag on the surface and this was penetrated by the briquette. The melt was held for 30 minutes and then cast into lds. The ingots 80 produced were then Rampled by drilling holes at different points across the diame~er both at the top and bottom of the ingot. The drillings from across a given diameter were blended and analyzed for molybdenum. The results, given in Table V, show that the . .
l'3'~ 5 distribution of molybdenum was very uniform and that the recoveries were 100% for the reduced materials.
Table V
Distribution and Recovery of Molybdenum in Iron Ca~tin~s Input Output Molybdenum Molybdenum Concentration Recovery Iron + Contained in Casting Wt.% (Average) Molyb- Molyb-Run Iron denum denum Ingot No.* gm gm gm No. Top Bottom %
_ 2 7300 25.79 15.52 (1) 0.202 0.210 99 (2) 0.209 0.208 3 7300 17.8 15.52 (1) 0.209 0.209 100 (2) 0.209 0.208 7300 17.54 14.29 (1) 0.194 0.199 101 6 7300 34.27 21.23 (1) 0.289 0.288 100 * Runs 2, 6 used 30 wt.% iron briquet~es; Runs 3, 5 used reduced lybdenum oxide briquettes alone Without further analysis, the foregoing will 80 fully reveal tbe gist of the present invention that others can by applying current knowledge --readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations ~hould and are intended to be comprehended within the meaning ant range of equlvalence of the following claims.
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Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. The process of making a briquette comprising molybdenum or a mixture of molybdenum and iron, said briquette being capable of penetrat-ing steel slags comprising the steps of:
(a) charging molybdenum oxides or a mixture of molybdenum oxides and iron oxide into a reduction furnace;
(b) reducing with a gaseous reducing agent in a first stage at a temperature between about 500° to 650°C substantially all molybdenum tri-oxide in said molybdenum oxides to molybdenum dioxide;
(c) reducing with a gaseous reducing agent in a second stage at a temperature between about 800 and 900°C substantially all the molybdenum dioxide to metallic molybdenum or the mixture of molybdenum dioxide and iron oxide to a mixture of metallic molybdenum and metallic iron;
(d) crushing the metallic molybdenum or the mixture of metallic molybdenum and metallic iron; and (e) briquetting said crushed metallic molybdenum or the mixture of metallic molybdenum ant metallic iron to a specific gravity greater than about 3.5 while retaining individually distinct particles of metallic molybdenum.
(a) charging molybdenum oxides or a mixture of molybdenum oxides and iron oxide into a reduction furnace;
(b) reducing with a gaseous reducing agent in a first stage at a temperature between about 500° to 650°C substantially all molybdenum tri-oxide in said molybdenum oxides to molybdenum dioxide;
(c) reducing with a gaseous reducing agent in a second stage at a temperature between about 800 and 900°C substantially all the molybdenum dioxide to metallic molybdenum or the mixture of molybdenum dioxide and iron oxide to a mixture of metallic molybdenum and metallic iron;
(d) crushing the metallic molybdenum or the mixture of metallic molybdenum and metallic iron; and (e) briquetting said crushed metallic molybdenum or the mixture of metallic molybdenum ant metallic iron to a specific gravity greater than about 3.5 while retaining individually distinct particles of metallic molybdenum.
2. The process according to claim 1 wherein molybdenum trioxide is charged into the reaction furnace.
3. The process according to claim 1 wherein a mixture of molybdenum trioxide and iron oxide is charged into the reaction furnace.
4. The process according to claim 1, 2 or 3, wherein said gaseous reducing agent is selected from dissociated ammonia, carbon monoxide, hydrogen, reformed hydrocarbons and mixtures thereof, and is fed counter-current to the molybdenum oxides and molybdenum dioxide.
5. The process according to claim 1, 2 or 3 wherein said gaseous reducing agent is fed to said second stage, a first portion of gas exiting from said second stage is recycled to said second stage after condensing water therefrom, and a second portion of gas exiting from said second stage is fed to said first stage.
6. The process according to claim 1, 2 or 3 wherein said gaseous reducing agent is fed to said second stage, a first portion of gas exit-ing from said second stage is recycled to said second stage after condens-ing water therefrom, and a second portion of gas exiting from said second stage is fed to said first stage, said second portion of gas being at least the stoichiometric equivalent required to reduce molybdenum trioxide to molybdenum dioxide in said first stage.
7. The process according to claim 1 or 2 wherein the molybdenum oxide is briquetted prior to charging to the reduction furnace.
8. The process according to claim 1 or 3 wherein said mixture of molybdenum oxide and iron oxide is briquetted prior to charging to the reduction furnace.
9. The process according to claim 1, 2 or 3 wherein a liquid binder is used in preparing the briquetted mixture.
10. The process according to claim 1 or 3 which includes the prelim-inary steps of mixing molybdenum disulfide and pyrite and roasting to provide said mixture of molybdenum trioxide and iron oxide.
11. A ferro-molybdenum product in briquette form consisting essentially of about 5 to 30 wt. % iron, not more than 7% oxygen, and the balance molybdenum, said briquette having a specific gravity not less than 3.5 and consisting essentially of individually distinct particles of metallic molybdenum and metallic iron.
12. A ferro-molybdenum product of claim 11 containing less than 7% oxygen.
13. The product of claim 11 or 12 wherein the briquette has a specific gravity of between about 4.5 and 7Ø
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US36328473 US3865573A (en) | 1973-05-23 | 1973-05-23 | Molybdenum and ferromolybdenum production |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1044486A true CA1044486A (en) | 1978-12-19 |
Family
ID=23429609
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA200,296A Expired CA1044486A (en) | 1973-05-23 | 1974-05-17 | Molybdenum and ferromolybdenum production |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US3865573A (en) |
| JP (1) | JPS5016607A (en) |
| CA (1) | CA1044486A (en) |
| DE (1) | DE2424684A1 (en) |
| FR (1) | FR2230744B1 (en) |
| GB (1) | GB1472118A (en) |
| NL (1) | NL7406937A (en) |
Families Citing this family (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3966459A (en) * | 1974-09-24 | 1976-06-29 | Amax Inc. | Process for thermal dissociation of molybdenum disulfide |
| US4039325A (en) * | 1974-09-24 | 1977-08-02 | Amax Inc. | Vacuum smelting process for producing ferromolybdenum |
| US4045216A (en) * | 1975-11-03 | 1977-08-30 | Amax Inc. | Direct reduction of molybdenum oxide to substantially metallic molybdenum |
| US4113479A (en) * | 1976-02-27 | 1978-09-12 | Amax Inc. | Vacuum smelting process for producing ferrotungsten |
| SE401524B (en) * | 1976-04-14 | 1978-05-16 | Ferrolegeringar Trollhetteverk | PROCEDURE FOR CONVERSION OF MOLYBDEN CONCENTRATE TO FERROMOLYBD AND AT THE SAME TIME DISPOSAL OF POLLUTIONS BY DIRECT REDUCTION WITH SULFID-FORMING REDUCING AGENT |
| US4547220A (en) * | 1984-04-24 | 1985-10-15 | Amax Inc. | Reduction of MoO3 and ammonium molybdates by ammonia in a rotary furnace |
| US4659376A (en) * | 1984-05-25 | 1987-04-21 | Amax Inc. | Fluid bed reduction to produce molybdenum metal |
| JPH0791567B2 (en) * | 1985-02-15 | 1995-10-04 | 株式会社小松製作所 | Sintering method |
| US4758406A (en) * | 1987-11-25 | 1988-07-19 | Amax Inc. | Molybdenum addition agent and process for its production |
| AU4623589A (en) * | 1988-11-14 | 1990-06-12 | Hans Moller | A motory system for producing a relative, incremental movement and positioning between two bodies |
| ES2060171T3 (en) * | 1989-06-02 | 1994-11-16 | Cra Services | MANUFACTURE OF FERROALLOYS USING A CAST BATH REACTOR. |
| US5954857A (en) * | 1997-01-17 | 1999-09-21 | Kennecott Holdings Corporation | Molybdenum oxide briquettes and a process for their preparation |
| AT409271B (en) * | 2000-02-04 | 2002-07-25 | Treibacher Ind Ag | METHOD FOR PRODUCING AGGLOMERATES, CONTAINING IRON AND AT LEAST ONE OTHER ELEMENT OF GROUPS 5 OR 6 OF THE PERIODIC SYSTEM |
| EP1162281A1 (en) * | 2000-06-09 | 2001-12-12 | Harper International Corp. | Continous single stage process for the production of molybdenum metal |
| US6626976B2 (en) * | 2001-11-06 | 2003-09-30 | Cyprus Amax Minerals Company | Method for producing molybdenum metal |
| US7192467B2 (en) * | 2001-11-06 | 2007-03-20 | Climax Engineered Materials, Llc | Method for producing molybdenum metal and molybdenum metal |
| US7276102B2 (en) * | 2004-10-21 | 2007-10-02 | Climax Engineered Materials, Llc | Molybdenum metal powder and production thereof |
| US7524353B2 (en) * | 2004-10-21 | 2009-04-28 | Climax Engineered Materials, Llc | Densified molybdenum metal powder and method for producing same |
| EP1691421A1 (en) * | 2005-02-10 | 2006-08-16 | Nederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO | Process for preparing a metal film on a substrate |
| US8709126B1 (en) * | 2010-02-03 | 2014-04-29 | Stc.Unm | Generation of metal and alloy micron, submicron, or nano particles in simple, rapid process |
| US20120156084A1 (en) * | 2010-08-24 | 2012-06-21 | Korea Institute Of Geoscience And Mineral Resource (Kigam) | Method of manufacturing sintered ferromolybdenum alloy from mixed powder of mill scale and molybdenum oxide powder by solid gas reaction |
| EP2597165B1 (en) | 2011-11-25 | 2014-09-03 | AB Ferrolegeringar | Iron and molybdenum containing pellets |
| CN104053799A (en) * | 2011-11-25 | 2014-09-17 | 法罗雷格林加股份公司 | Iron and molybdenum containing pellets |
| US9540707B2 (en) | 2011-11-25 | 2017-01-10 | Ab Ferrolegeringar | Iron and molybdenum containing agglomerates |
| SE537536C2 (en) * | 2013-05-27 | 2015-06-02 | Ferrolegeringar Ab | Iron and molybdenum-containing briquettes and a process for producing these briquettes |
| CN109778059B (en) * | 2019-01-21 | 2021-01-26 | 西安建筑科技大学 | Porous ferromolybdenum alloy and preparation method and application thereof |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1315859A (en) * | 1919-09-09 | pfanstiehl | ||
| US1401924A (en) * | 1920-06-14 | 1921-12-27 | George W Sargent | Process of recovering molybdenum from molybdenite |
| US1659205A (en) * | 1924-11-22 | 1928-02-14 | Westinghouse Lamp Co | Method of producing refractory metals |
| US2107279A (en) * | 1935-06-17 | 1938-02-08 | Fansteel Metallurgical Corp | Production of refractory metals and alloys |
| FR950372A (en) * | 1941-10-01 | 1949-09-26 | Westinghouse Electric Corp | Reduction of molybdenum trioxide |
| US2398114A (en) * | 1942-09-12 | 1946-04-09 | Westinghouse Electric Corp | Reduction of molybdenum trioxide |
| US2776887A (en) * | 1952-08-22 | 1957-01-08 | Westinghouse Electric Corp | Preparation of molybdenum |
| US2763918A (en) * | 1953-06-05 | 1956-09-25 | Chromium Mining & Smelting Cor | Process of making a ferroalloying material and product obtained thereby |
| US3053614A (en) * | 1959-10-27 | 1962-09-11 | Nat Distillers Chem Corp | Molybdenum process |
| US3264098A (en) * | 1963-08-19 | 1966-08-02 | Westinghouse Electric Corp | Fluidized bed process for the production of molybdenum |
| US3407057A (en) * | 1965-10-23 | 1968-10-22 | American Metal Climax Inc | Molybdenum powder for use in spray coating |
| FR1532288A (en) * | 1967-01-06 | 1968-07-12 | Ugine Kuhlmann | Molybdenum agglomerates for use in steelworks and process for their manufacture |
| US3622301A (en) * | 1970-01-09 | 1971-11-23 | Sherritt Gordon Mines Ltd | Treatment of nickel containing material to remove molybdenum |
-
1973
- 1973-05-23 US US36328473 patent/US3865573A/en not_active Expired - Lifetime
-
1974
- 1974-04-29 GB GB1860874A patent/GB1472118A/en not_active Expired
- 1974-05-08 FR FR7415838A patent/FR2230744B1/fr not_active Expired
- 1974-05-13 JP JP5235074A patent/JPS5016607A/ja active Pending
- 1974-05-17 CA CA200,296A patent/CA1044486A/en not_active Expired
- 1974-05-21 DE DE2424684A patent/DE2424684A1/en not_active Ceased
- 1974-05-22 NL NL7406937A patent/NL7406937A/xx not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| FR2230744B1 (en) | 1978-11-17 |
| NL7406937A (en) | 1974-11-26 |
| JPS5016607A (en) | 1975-02-21 |
| GB1472118A (en) | 1977-05-04 |
| DE2424684A1 (en) | 1974-12-12 |
| US3865573A (en) | 1975-02-11 |
| FR2230744A1 (en) | 1974-12-20 |
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