US2402084A - Continuous reduction of molybdenum compounds - Google Patents

Description

.im 11 1946 i CONTINUOUS REDUCTION OF MOLYBDENUM COMPOUNDS R. F. RENNIE 2 Sheets-Sheet Filed Jan. v, 194s m QL INVENTOR f?. F.' )PENN/E ATTORNEY MN wu mw R. F. RENNIE CONTINUOUS REDUCTION OF MOLYBDENUM COMPOUNDS Filed Jan. 7, 1943 2 Sheets-Sheet 2 mvENToR f?- F: /ENA//E MW ATTORNEY Patented June 11, 1946 CONTINUOUS REDUCTION MOLYBDENUM COMPOUNDS Robert Fredrik Rennie, Lake Forest, Ill., assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation oi Pennsylvania Application January 7, 1 943, Serial No. 471,804

15 Claims. (Cl. 75--84) This invention relates to the manufacture of molybdenum, and more particularly to a method oi' continuously reducing compounds of molybdenum, suchv as the trioxide and ammonium molybdate, for that purpose.

The principal object of my invention, generally considered, is in shortening and otherwise improving on the manufacture of molybdenum, starting with a reducible compound, avoiding slow reduction due to keeping the reaction temperature low, and continuously moving the compound through a furnace in a direction opposite to that of the reducinggas.

Another object of my invention is the reduction of molybdenum trioxide, or other reducible compound, to molybdenum, while continuously moving the same in a direction opposite to the flow of the reducing gas.

A further object o! my invention is the reduction of a molybdenum compound to molybdenum, by moving it in a furnace continuously through heat zones of increasing temperatures, while passing reducing gas through said furnace in a direction opposite t that of said movement, at the same time stepwise increasing by effective concentration the strength of said reducing gas, to improve the quality of the metal produced and in order to avoid a runaway reaction.

Other objects and advantages of the invention, relating to the particular features and steps of the process, will become apparent as the description proceeds.

Referring to the drawings:

Figure 1 is a vertical longitudinal sectional view, with parts in elevation and parts shown diagrammatically, of a furnace and associated apparatus for reducing molybdenum compounds to molybdenum.

Figure 2 is a vertical, longitudinal, sectional view, with parts in elevation and parts shown diagrammatically, of another embodiment of a furnace and associated apparatus for practicing Vmy invention.

Figure 3 is a view similar to Fig. 2, except a furnace part is shown fragmentarily in elevation, and the loading end of the furnace is open while the unloading mechanism is shown in engagement with boats for the purpose of removing them from the furnace.

In my copending application, Serial No; 413,118, nled October 1, 1941, now Patent No. 2,385,843, dated October 2, 1945, I have disclosed a method of reducing ammonium molybdate to molybdenum, making use of some 'of the ammonia generated during the breaking down of the molybdate for reduction purposes, and diluting the hydrogen used in the ,main reducing action with steam in order to slow down the reaction where necessary and avoid the formation of imperfect metal. This process is an improvement over that previously employed, but is not continuous in that the molybdate is introduced into the furnace and the reducing atmosphere and temperature varied as desired until it is changed to molybdenum, whereupon it is Withdrawn.

In my copending application, Serial No. 458,106, filed September l2, 1942,- I have disclosed a method of reducing molybdenum trioxide to molybdenum, which is similar to that of reducing ammonium molybdate to molybdenum, as disclosed in my application above-mentioned, except that the material is preferably granulated before reduction and I suggested using reducing agents other than hydrogen, it of course being understood that in the reduction oi the trioxde there is no ammonia inherently available for reducing purposes.

The present invention is an improvement over the above-mentioned processes for stationary reduction of molybdenum compounds by various reducing gases, in that I propose to move the charge to be reduced forward at constant speed into zones of increasing temperature and in a direction opposite to that of the iiow of the reducing gas, whereby said gas may be introduced when in its most concentrated or highly reducing condition, and reduced in strength, not only by the steam evolved during the reduction process, but also by the addition of desired amounts of steam along the length of the furnace, thereby avoiding a runaway reaction at the beginning of the reduction process, and improving the quality of the metal which is produced.

Since the time-temperature schedules for such a reduction have been worked out for stationary reductions, as described in the aforementioned pending applications, I have correspondingly arranged the speed with which the charge moves forward and the length of the diiferent temperature zones so as to substantially conform with said schedules, the difference being necessitated by the fact that the control is by the strength of the reducing agent, temperature, length of heating zones, and the speed of movement ci' the charge therethrough, rather than by varying the flow of hydrogen or other reducing gas and the amount of diluting material during an increase in temperature o f the reduction furnace.

Before this improvement was introduced, there was some difficulty when one tried to decide what flow of hydrogen, or other reducing gas, to use. If the reduction tube was fed with the amount of hydrogen that is needed in the end zone, it would cause a too violent reaction in the zones of lower temperature, or those near where the reaction is beginning. If the furnace was fed with the amount of hydrogen that is wanted at the beginning of the reduction process, the end zone would have to be made impractically long to give complete reduction.

compounds to molybdenum by a continuous process. I propose to feed the reduction tube With the hydrogen, or other reducing gas, necessary for speedy complete reduction in the end zone, and

at diierent points admit controlled amounts oi" steam, or other diluting agent, into the reduction tube to slow down the reaction Where necessary 'and prevent \the formation of imperfect metal.

Referring now to the drawingsin detail, like parts being designated byv like reference characters, and first considering the embodiment of my invention illustrated in Fig. 1, there is shown a furnace li consisting of a preferably slightly inclined reduction tube I2, which may be of about 4" internal diameter and formed of relatively refractory material, such as nichrome. This tube may be covered with suitable insulating material I3, in turn enclosed in a sheet metal envelope I4 and heated in anydesired manner, as by 4 means of resistance wires I5, I6, and I1, respectively, controlled by rheostats I8, I9 and 2| to provide three heating zones, respectively designated as 22, 23 and 24.

The windings, insulation, and other characteristics of the furnace are such that the heating zone 22.may be maintained at about 400 C., the zone 23 at about 630 C., and the zone 24 at about 1075" C. The furnace and accessories are desirably held in position as by means of supports 25. 'I'he left hand end of the furnace has a section desirably cooled by a water jacket 26 and provided with an outlet pipe 21 for the excessM hydrogen, steam and/or ammonia, or otherreagent used during the process. It is 'closed by a hinged door or cap 28, desirably including power means for pushing the molybdenum compound through the furnace, such as an air lor water cylinder 23 and piston 3l for operating a rod 32 and associated pusher element 33. 'I'his or other suitable means may be used for moving the containers on boats 34, of the molybdenum compound to be reduced, at uniform speed from the left hand or inlet end of the furnace to the right hand or outlet end. The door or cap 28 may be secured in place by locking means 35, and provided with a chain 30 to a counterweighi; and lifting apparatus (not shown).

The outlet end ofgthe furnace is provided with a section cooled by a water jacket or like means 38 and provided with a pipe 31 for introducing a supply of hydrogen or other reducing gas. The extreme end of the cooling section 38 of the tube I2 is closed by a hinged lid or door 38, provided with a-suitable latch or locking device 4I.

amounts of water, or other diluting agent, along the length of the tube I2, said means in the present embodiment comprising pipes 42, 43 and 4. Water for these pipes is supplied from a reservoir Ll5 kept in the desired level as by means of a oat valve (not shown) in the Water supply pipe 66. The ow of the water from the reserlvoir to the pipes 42, 43 and 44 is controlled by valves i3 and 49, respectively, admitting water through gaged capillary tubes 5I, 52 and 53 and transparent connections 5d, 55 and 56, permitting observation of the flow of water.

rihe hydrogen or other reducing gas'supplied passes to the reduction tube at a desirably continuous rate being, however, naturally steadily attenuated during the reaction process by. steam and/or other reaction product, with the excess withdrawn from pipe 2 for reclamation after the condensation o'f any steam therefrom.

I will no w describe a preferred reduction schedule of molybdenum trioxide to molybdenum, preferably using hydrogen on granulated material, the manufacture of -'which'has been described in my application, Serial No. 458,106, previously referred to, although I do not wish to be limited to the use of such material, as ammonium molybdate and other reducible molybdenum compounds may be handled in a similar manner. Instead of hydrogen, mixtures thereof such as Endogas (which is mainly a mixture of hydrogen and carbon monoxide, diluted with nitrogen) and water gas, and other reducing agents such as carbon monoxide, ammonia, and reducing mixtures, as referred to in said application, Serial No. 458,106, may be employed. It svill also be understood that other diluting agents such 'as nitrogen and carbon dioxide, as referred to in said application, may be employed instead of, or admixed withs`team or with each other. The schedule disclosed is merely illustrative and changes may be made within the broad scope of my invention.

The preferably granulated molybdenum trioxide (M003) is placed in boats 34, desirably formed of refractory metal such as nickel, preferably about 2 kilograms per boat, the material being spread out in the boats to expose as much sur'- faceaspossible.

The loaded boatsvmay be ilrst introduced into the cool or left hand end portion of the tube I2, after opening the cap or door 28, a sumcient number of boats being placed in front of the pusher element 33 so that the process may be continuous for a desired number of hours without shutting off the ow of hydrogen, or other reducing gas, and replenishing the supply of material to be reduced.. After insuring that both doors 28 and 39 are closed and that cooling water is circulating through the Waterjackets, thehydrogen supply. is turned on, as by opening the Y valve 51, to ush out the air in the tube I2 in order to insure that no explosion will occur when the furnace is brought to a higher temperature.

The electric current is then turned on to the resistance wires I5, IB and I1, or other heating source applied, until the zones of the vfurnace reach the desired temperatures, as may be indicated by suitable pyrometers (not-shown). That is, the temperature in the zone 22 controlledby wire I5 is desirably 400 C., that in zone 23 controlledby wire 'I6 is desirablyY 630 C., y"and that in zone 24 controlled by wire I'I is desirably -1075 C. The flow of water to the pipes 42, 43 and 44 is regulated so that we desirably lget about Means are provided for introducing desired 'I6 3 cc. per minute from the pipe 42. aboutl 9 cc.

`43 to make the reaction to molybdenum dioxide,

or intermediatereduction product, come to a standstill, with approximately 100% of that` product at the point of admission of pipe 43. Enough water is to be admitted by pipe 44 to slow the reaction from the molybdenum trioxide, or starting product, sufficiently to prevent overheating and premature formation of imperfect metal. Compared with the stationary reduction described in the applications referred to, more than proportionate amounts of steam must be added because at the point of entry of pipe 43 there will be about 100% excess of hydrogen, and at the point of entry of pipe 44 there will be about 300% excess of hydrogen. This continued addition of steam during the process of reduction desirably coarsens the metal powder produced. This explains the reason for the steam inlet pipe 42, which is not to control the speed of reduction, but to control particle size of reduced metal, In certain cases, however, it may not be necessary to add any water by this pipe 42, or the proportion of water at this point may be varied, depending on the progress of the reduction as determined by experience.

At the same time air is admitted to the end pipe 53, as by means of a suitable control valve (not shown), to cause the pusher element 33 to start uniform movement of the boats 34 through the various zones of the furnace at a rate of speed calculatedto leave said boats in zone 22 for about one hour, in zone 23 for about 2% hours, and in zone 24 for about 31/2 hours. The lengths of said zones are thus made proportionate to the times in which the boats are to remain therein, thatis. in the ratioof 1:21A:31/.

The operation, therefore, starts at about 400 C. with the hydrogen or other reducing gas diluted with a maximum amount of steam, or other diluting agent, not only on account of the introduction of water, but also because of the formation of water by reaction of hydrogen with the oxygen of the molybdenum trioxide, or other oxygen compound, as said agent passes along the reducing tube from right to left. This reducing action by the hydrogen, or other reducing gas, starts the reduction of molybdenum trioxide, or

other compound, toward a lower oxidation product, such as the dioxide, avoiding by dilution a runaway reaction at undesired high temperatures and the production of imperfect metal.

Finally the boats successively reach the next zone where they are heated to a temperature of about 630 C., in a reducing atmosphere more concentrated than that in the zone 22, because there is not only less water admitted in this zone,v

but there has been less impoverishment of the reducing gas. In this second zone the reduction to molybdenum dioxide is substantially completed so that upon reaching the zone 24, of the higher temperature of about l75 C., the still more concentrated reducing atmosphere may be safely employed without danger of a runaway reaction or the development of imperfect metal.

If molybdenum trioxide is reduced in this manner, the reaction is in accordance with the following equations:

MoO3+H2ziMoOz+H2O+29-7 kg. calories per gr.

mol. (exothermic) M'nOz-l-2HzzMo-lf-2H2O-6 kg. calories per gr.

mol. (endothermic) The above equations were developed from the Hours Oclock Furnace temp.

l. 8:00 to 9:00.... 400 50 cu. it. oi H; per hr.+l5+ cc.

H10 per min.I

2 9:00 to 11:15... 030 50 cu. it. ol Hr per hr.+12+ cc.

' H2O per min. Reduction to M002 nearly complete.l

35..... 11:15 to 2:45... l, 075 60 cu. ft. of H2 er lx1-.+from 3+ cc. to no 10 per min. Remainder o! M001 reduced to Mo.l

The flow oi H2, starting a't 50 cu. ft. per hr. at exit end lofiurnace, is continually reduced toa variable extent due to combmmg with the O of the M00; and M002 during the process.

From the foregoing it will be seen that I have shortened the schedule to 6% hours, from the 9 hour schedule of the applications previously referred to, I have, as in said earlier applications, also provided for the elimination of clinkers and/or cones and made it possible to reduce from a high oxidation form, such as the trioxide, directly to the metal in one continuous process, that is, pushing the boats of oxide in one end of a furnace and withdrawing them from the other end, While maintaining a continuous flow of reducing and diluting materials through said furi nace. At the same time, I provide for salvage of any unused hydrogen or other reducing gas.

It will, of course, be understood that the continuous time of any process, prior to removal of the reduced metal and re-charging with oxide or other compound depends on the length of the reduction tube, as in the embodiment described the pusher element 33 can operate only until the charge associated therewith reaches the end of the tube or outlet door 39 thereof. It is, therefore, believed desirable that the inlet end of the furnace, or that cooled by the water jacket 26, be of a length corresponding with the intertermediate or heated portion thereof, and that the outlet end, or that cooled by the water jacket 38, be of a corresponding length, so that a charge of boats equal in length to the heated portion of the tube, that is the portion consisting of the left hand end of the furnace and the operation continued until completed, when the entire charge will have been moved to the outlet end. Thereupon the hydrogen or reducing gas supply may be shut off, the heating current terminated, the flow of water or other diluting agent stopped and, when the furnace is suiciently cool to avoid undesired `oxidation of the reduced metal, the door 39 may then be opened and the charge of metal removed, after which the door 28 may be opened and a. new charge of oxide, or other reducible molybdenum compound, introduced and the process repeated.

Referring Vnow to the embodiment of my invention illustrated in Figs. 2 and 3, there is fragmentarily shown a furnace Ill, which may be identical with the furnace of the preceding embodiment insofar as the central or heating section is concerned. However, the left hand or loading end of the inclined reduction tube |2a of the furnace of the present embodiment, has a section that is cooled by water jacket 26* and provided with an outlet pipe 21EL for excess hydrogen, steam and/or ammonia or other reagent used during the process, and said section need not be as long as the furnace or heating section for reasons which will be explained.

In the present instance the loading end of the tube I2n is closed by a door or cap 23, including power means for pushing the molybdenum compound through the furnace, such as, for example, an hydraulic cylinder 29B, piston 3|, operating a rod 32, and associated pusher element 33B.

This or other suitable means may be used for moving the containers or boats 34a of the molybdenum compound at uniform speed, from the left hand or inlet end .of the furnace to the right hand or outlet end. The door or cap 28a is, in the present instance, hinged at, its lower end rather than at its upper end and normally secured in place by locking means 35a. As in the preceding instance, the cylinder 29a is provided with a chain 30a to a counterweight and lowering apparatus (not shown).

'I'he outlet end of the furnace is provided with aV section, cooled by water jacket or like means 36EL and provided with a pipe 31a for' introducing a supply of hydrogen or other reducing gas. 'Ihe extreme end of the cooling section 382t of the reduction tube |2a is closed by a cap or lid 39e', provided with suitable latch or locking device MB.'

The cooling section V38a of the reduction tube l2il is in this instance formed in two sections which may be separated as in Fig. 2, or connected as in Fig. 3, by closing or opening the gate valve 6|.

The cap 39B is provided with an aperture containing a sleeve element 62 and hooked rod 63, controlled by a handle 64, so that they are adapted to be reciprocated and turned at will. They may be moved toward the entrance end of the reduction tube when the gate valve 6| is open, as in Fig. 3, and turned so that the hooked end portion 66 of the rod 63 engages one or more of the boats Y 34 to pull it, or them, to the right hand position shown in Fig. 2, whereupon the gate valve may be closed, the cap 39 and its associated sleeve and rod removed, and the boats taken out of the furnace. The sleeve 62 is desirably provided with a collar or flange B5 which is adapted to engage the forward or right hand end of a boat 34* to tell the operator when to turn the handle 64 so that the hooked end portion 6B thereof will connect with the boat or boats 34a nearest the exit end of the furnace.

The hydrogen supply pipe 81 is desirab-ly provided with a branchl 68 controlled by a valve 69 so that the extreme right hand section., of the reduction tube, or that beyond -the gate valve 6|, may, prior to opening said valve to resume the reducing operation, be hushed out with hydrogen so that when said gate valve is opened an explosive mixture will not be formed. During the flushing operation the air is exhausted through pipe 1| controlled by valve 12.

The operation of the embodiment of. my invention illustrated in Figs. 2 and 3 may be as follows:

'I'he loaded boats of the reducible compound,

such as the granulated trioxide, may be rst inof the tube I2* after dropping the cap or door 28e. Any convenient number of boats are placed in front of the pusher element 331. When the door 28'* is open, the valve 13 in the hydrogen exhaust pipe-21a is closed as by releasing the spring actuated stem 14 thereof by swinging the adjustable pusher element 10 of the operating arm 15 from engagement therewith. The arm 15 is integral with or connected to the door 28* so as to swing therewith.

At the same time the valve 16 is opened, as by release of its spring actuated stem 11 by disengagement of the arm-carried adjustable pusher element 80, to increase the supply of gas to the pipe 18 to change the pilot light 19 issuing therefrom to a relatively long name 8| and thereby ignite the issuing hydrogen, or other reducing gas 82, and prevent the formation of a'n explosive mixture.

When the furnace is open, as represented in Fig. 3, then the charge of boats 34a may be introduced, as by pushing them in along a loading plate 83 by means of a pusher element 84, after which the door 28* is closed as in Fig. 2, au-v tomatically reducing the flame 8| to the pilot light 19 and opening the reducing gas exhaust pipe valve 13 by bringing the operating arm 15 into engagement therewith.

The hydrogen, or reducing gas supply is then turned on, the furnace brought up to temperature, and the reducing action started as described in connection with the embodiment of Fig. 1. The hydraulic cylinder or other operating means pushes the boats 34EL a desired distance into the furnace, whereupon the pusher element 33*I may be withdrawn, the filling end of the furnace opened, and some more boats placed therein, as illustrated in Fig. 3.

This pushing and withdrawing operation is repeated until it is estimated that the boats at the head or right hand end of the line are coming close to the gate valve 6|. Said gate valve 6| is then opened, the hooked rod 63` moved from the position shown in Fig. 2 to that shown in Fig. 3 and turned to engage one or more of the boats 34a and pull them to the extreme right hand position shown in Fig. 2. The gate valve 6| is then closed, the exit cap 3SE and'its hooked rod 53 removed therefrom and the captured; boats taken out of the furnace. 'Ihe cap 39P- and rod 63 are reapplied to the furnace as in Fig. 2, the outer section or that to the right of the valve 6| flushed out with hydrogen, the valves 69 and 12 closed, the gate valve 6| opened.

It will be understood that the reducing operation may bev continued uninterruptedly during the operation of the loading or unloading of the furnace. The short stoppage time taken for loading is allowed for as part of the reduction time, the time taken for unloading, however, not affecting the reduction time because during the unloading operation the piston 3 I may operate and continue to push the boats from left to right in the reduction tube.

In brief, during continuous operation the following steps will preferably occur:

1. Pusher element 32a moved from position in Fig. 2 to extreme left position.

2. YDoor 28l moved from position in Fig. 2 vto that of Fig. 3.

3. Charge-introduced as shown in Fig. 3.

4. Door 28n closed and pusher element 33a restarted by operation of hydraulic cylinder.

.5. Gate valve 6| opened and hooked member moved from position in F18. 2 to that of Fig. 3 to 10. Outer section 38 of reduction tube flushed out with hydrogen or other reducing gas.

1l. Gate valve 6| opened, completing the cycle of operations.

It will thus be seen that my reduction process may be continuous for a predetermined period, when using the apparatus of Fig. 1 or continuous for an indenite period, when using the apparatus illustrated in Figs. 2 and 3. It will also be understood that the description of the apparatus of Fig. 2 is to be supplemented by the description of the apparatus of Fig. 1, insofar as the details of the furnace or heating portion of the apparatus and the reduction schedule is concerned. The essential difference between the two operations is that in connection with the second embodiment the loading piston will periodically move back to accommodate charges, that is, move at a substantially continuous and uniform rate punctuated only by the brief loading intervals, and the reduced metal will .be withdrawn without stopping the furnace, while in the first embodiment the charge is started at the loading end and pushed on through to the unloading end without opening the furnace or stopping the movement of the boats in any manner.

It will be understood that, as in my prior application, Serial No. 458,106, no water or other diluting agent need be employed if a suiciently weak reducing gas, such as ammonia or Endogas, is initially employed, as the heat generated during the reaction is considerably less, especially in my present improved process which inherently provides for a weaker reducing action at the start because of the travel of the reducing gas in a direction opposite to that of the compound being reduced and the continuous dilution of the gas by the gaseous product of reduction. In the reduction of ammonium molybdate, making use of ammonia generated during the reducing action, the hydrogen obtained by the cracking of the ammonia is diluted with uncracked ammonia. It

will also be understood that if desired my process may be controlled by pressure as described in connection with my co-pending application, Serial No. 458,106.

Although preferred embodiments of my invention have been disclosed, it will be understood that modifications may be made within the spirit and scope of the broad idea.

I claim:

1. The method of producing molybdenum from a reducible compound thereof, comprising moving said compound through a furnace, passing a reducing gas through said furnace in a direction opposite to that of the movement of said compound, and introducing gas inert to said cornpound into said furnace intermediate the ends thereof. to slow down the initial reaction until the reduction is partially eected.

2. The method of producing molybdenum from a reducible compound thereof, comprising moving said compound through a furnace from a relatively low temperature zone into one of higher temperature, passing a reducing gas through said furnace, and diluting said reducing gas by iny the initial reaction until reduction is partially effected.

3. The method of producing molybdenum from a reducible compound thereof, comprising moving said compound through a furnace from a relatively low temperature zone into one of higher temperature, passing a reducing gas through said furnace in a direction opposite to that of the .movement of said compound, and diluting said reducing gas by introducing an inert gas into said furnace intermediate the ends thereof in order to slow down the initial reaction until reduction is partially effected.

4. The method of producing molybdenum from a reducible compound thereof, comprising moving said compound through a, furnace from a relatively low temperature zone into one of higher temperature, passing hydrogen through said furnace, and diluting said hydrogen by introducing an inert gas into said furnace intermediate the ends thereof in order to slow down the initial reaction until reduction is partially effected.

5. The method of producing molybdenum from a reducible compound thereof, comprising moving said compound through a furnace from a relatively low temperature zone into one of higher temperature, passing a gaseous reducing mixture through said furnace, and diluting said mixture with inert gas intermediate the ends of said furnace in order to slow down the initial reaction until reduction is partially effected.

6. The method of reducing molybdenum trioxide comprising moving it through a furnace, passing hydrogen through said furnace in a direction opposite to that of the movement of said trioxide, and diluting said hydrogen with steam intermediate the ends of said furnace in order to slow down the initial reaction until the reduction is partially effected.

7. The method of reducing ammonium molybdate comprising moving it through a furnace, passing hydrogen through said furnace in a direction opposite to that of the movement of said molybdate, and diluting said hydrogen with steam intermediate the ends of said furnace in order to slow down the initial reaction until reduction is partially effected.

8. The method of reducing molybdenum tri-f oxide comprising moving it through a furnace from a relatively low temperature zone into one of higher temperature, passing hydrogen through said furnace in a direction opposite to that of the movement of said trioxide, and diluting said hydrogen with steam intermediate the ends of said furnace in order to slow down the initial reaction until reduction is partially effected.

9. The method of reducing ammonium molybdate comprising moving it through a furnace from a relatively low temperature zone into one of higher temperature, passing hydrogen through said furnace in a direction opposite to that of the movement of said molybdate, and diluting said hydrogen with steam intermediate the ends of said furnace in order to slow down the initial reaction until reduction is partially effected.

10. The method of producing molybdenum from a reducible compound thereof comprising moving said compound through a furnace from a relatively low temperature zone into one of higher temperature, and passing a gaseous mixture, containing a large enough proportion of hydrogen and carbon monoxide to effect reduction of said compound, through said furnace in a direction opposite to that of the movement of said compound. and introducing gas inert to said comoxide comprising moving it in a furnace through and from a heat zone of about 400 C. into and through one of about 630 C., and then into and through one of about l075 C., while passing hydrogen through said furnace iin a direction opposite to that of the movement of said trioxide, and diluting the hydrogen in 'said furnace at a distance from its place of admission, and in at least some of said heat zones, in order to slow down the reaction until reduction is partially eiected.

12. The method of reducingmolybdenum trioxide comprising moving it successively into and through zones heated,"respectively, to 400, 630 and 1075 C., passing hydrogen through said furnace in a direction opposite to that of the movement of said trioxide, and diluting said hydrogen with steam at various points along said furnace, in order to effect a slowing down of the reaction at the earlier stages until reduction is sulciently eiected to avoid excessive generation of heat by the reducing action.

A13. The method of reducing molybdenum trioxide comprising moving it successively into and through zones in a reduction tube of about four inches internal diameter and heated respectively to 400, 630 and 1075 C., passing hydrogen at the rate of about 50 cu. ft. per hour through said furnace in a direction opposite to that of the movement of said trioxide, and diluting said hydrogen with direct additions of steam in each heat zone, in order to effect a .slowing down of the reaction in the earlier. stages, until reduction is sufilciently effected to avoid excessive generation of heat by the reducing action.

14. The method of producing molybdenum from a reducible compound thereof comprising `placing said compound in containers, introducing some of said containers in front of a pusher element in the reduction tube of a furnace, closing said tube, starting said pusher element to move said containers at a uniform rate of speed `through said tube, passing a reducing gas through said tube in a direction opposite to that of the movement of said compound, introducing inert gas into said furnace intermediate the ends thereof to slow down the initial reducing action until the reduction is partially eected,- pulling a desired number of said containers. after reduction of the compound therein, to the oppo- -site extreme end of said tube, closingv of! said extreme end portion of said tube from the main portion thereof, opening said extreme end portion of said tube, withdrawing the captured containers, closing Said extreme .end portions, flushing out said closed end 4portion of said Itube with reducing gas, reconnecting said closed end portion with the main portion of said tube, andrepeating said steps whereby the reducing operai tion may be continuous.

15. The method of producing molybdenum from the trioxide comprising placingl said trioxide in containers, introducingsome of said containers in front of a pusher .element in a cooled end portion of the reduction'tube of a furnace, closing said tube, starting said pusher element to move said containers at a uniform rate of speed through zones in said tube heated; respectively to 400, 630 and 1075 C., passing hydrogen through said tube in a direction opposite to that of the movement of said trioxide, diluting said hydrogen with steam at various points along said tube, to slowdown the initial reducing action until the reduction is partially effected, pulling a desired number of said containers, after reduction of the trioxide therein, to the opposite extremeend of said tube, closing off said extreme-end portion Of said tube from,

ROBERT FREDRIK REN'NIE.

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