US2663631A - Reduction of oxides - Google Patents

Description

Dec. 22, 1953 H. E. TscHoP ETAL 2,663,631

REDUCTION OF OXIDES Filed Aug. 27, 1949 6 Sheets-Sheet 1 DeC 22, 1953 H. E. TscHoP ETAL 2,663,631

' REDUCTION( oF oxIDEs FiledrAug. 27, 1949 `e sheets-sheet 2 //1/ WA/MMR maf-f2.5

Dec. 22, 1953 H E. TscHoP ETAL 2,663,531

REDUCTION OF OXIDES Filed Aug. 27, 1949 e sheets-sheet s WCLQM ATTORNEY Dec. 22, 1953 H. E. rsa1-10F x-:TAL

REDUCTION OF OXIDES Filed Mig. 27. 1949 6 Sheets-Sheet 4 Dec. 22, 1953 l H. E. TscHo ET AL 2,663,631

REDUCTION OF' OXIDES Filed Aug. 27. V194,9 e sheets-sheet 5 CH3/WEER 665 /l 4 l pff/5959i //////l/ Dec. 22, 1953 H. E'. TscHoP ET AL 2,663,631

REDUCTION oF oxInEs Filed Aug. 27, 194e csy Smets-sheet e Y cf/vrE/ 50i/YER aas Exam/s7- Mmm/v01. was-#53mm Patented Dec. 22, 1953 UNITED 'ST'EES REDUCTON OF OXIDES Ware Application August V27, 1949, Serial No. 112,774

12 Claims.

The present invention relates generally to an improved process for treating raw oxidic materials containing nickel and/or vcopper to obtain therefrom yhigh-'duality metal. More Vparticularly, the present invention relates to an improved process for partially reducing raw nickel and nickel-copper oxides to obtain a uniformly high metal content in said oxides and then to subsequently directly smelt 'and renne said partially-reduced oxides to produce nished nickel and nickel alloys containing copper whereby the production of metal from said oxides is greatly simpliiied and facilitated, to 1a machine having a n'ovel structure for obtaining controlled partial reduction of said oxides, and to a unique partially-reduced oxide product.

Heretofore, the nickel and nickel-copper bessemer mattes and/or -sintered mattes available as raw material for the usual open-hearth furnace, electric-arc furnace, or inductionfurnace smelting and rening processes were treated rst by roasting the nickel and/ or coppercontaining mattes to oxides and then by partially reducing the hot oxides with charcoal in an endeavor to obtain a consistently uniform and substantially high metal content in said oxides. In some cases, a double roasting was necessary to obtain a lsatisfactoryelimination of sulfur prior to reducing with charcoal. The reduced nickel or nickel-copper oxides were then used as part of the smelting charge along with charcoal or tar coke in acid open-hearth melting and refining operations. Further processing included either direct casting into pigs or else duplex refining the molten metal from the open hearth in a basic electric-arc furnace before casting into ingots.

Another method of sulfur elimination in the matte-sintering process was developed whereby low-sulfur, raw nickel oxide or nickel-copper oxides containing essentially no free metal were produced, these oxides then `being smelted with tar-coke additions to molten metal in gas-nred, batch-type furnaces without preliminary roasting. This method was also unsatisfactory in that reducing gases formed within the charge were diluted with and rapidly removed by the combustion gases. In addition, the coke-oxide mixture was insulating in character and heat penetrated very slowly to the interior portions of the charge. The overall result was a relatively slow reaction which began on the exposed surface of the charge and which proceeded slowly inwardly as the surface layers were reduced and melted away. Furthermore, contaminating ele- 2 ments, 'such as sulfur, were introduced into the metal by the tar coke and had 'to be eliminated by subsequent desulfurizing treatments.

IThe art has long sought a simple, inexpensive method for rapidly reducing oxides to obtain products of controlled composition which could then be directly converted to high-quality metal in a single smeltingererlning operation. '.Ihis problem was not solved |by any -of the conventional processes employed by or known to the art until the advent of the present discovery. @ne phase of the problem of reducing the oxides involves obtaining a high concentration of reducing gases in contact with the oxides which is necessary for rapid reduction of the oxides. This condition is attained only when dilution and contamination of the reducing gases by nitrogen and/ or combustion gases is avoided. In actual practice, this condition cannot be `attained Vin a blast furnace, a reverberatory-type furnace or la direct--red rotary kiln. Another phase of the oxide-reduction problem involves high thermal efficiency and excellent heat-transfer characteristics coupled with the employment of inexpensive fuel. lThe numerous processes which have been employed and which were intended to produce high concentrations of uncontaminated reducing gases in intimate contact with the oxides to be reduced have all been very unsatisfactory from the viewpoint of thermal efficiency, heat transfer and economy. .In particular, the conventional methods for producing nickel or nickel-copper alloys from the oxides of these metals have been relatively complicated, time 'and space consuming and costly. Furthermore, the metal content of the oxides reduced by the prior art methods preparatory to smelting and refining was variable and unpredictable.

Up to the Vpresent time, the art has failed to develop a technically efficient 'and economic process and apparatus which would obtain conccinitantly all the foregoing necessary conditions and satisfactorily solve the problem in a practical manner, particularly on an industrial scale to produce commercially acceptable products. The Aforegoing remarks are especially applicable to the nickel industry where the Volumes of materials handled are less than are those handled in the iron and steel industry and where the metallurgical properties of the nickel and nickel-copper oxides, such as sulfur absorption, etc., differ greatly from those of iron and iron oxides. The pressing nature of the problem is attested by the continued experimentation of the Bureau of Mines en oxide reduction processes 3 which likewise clearly indicates that the problem exists and that it has not yet been satisfactorily solved by others skilled in the art.

It is an object of the present invention to provide a novel process for simply, economically and rapidly producing nickel and nickel-copper alloys from raw oxides containing these metals which comprises as essential features in novel combination a unique operation for obtaining partially-reduced oxides of uniform and consistently high metal content, directly converting said reduced oxides to high-quality metal in a single smelting and refining operation without substantial addition of supplementary reducing agents.

It is another object of the present invention to provide as an essential feature in a novel combination of operations, an operation for obtaining a high degree of controlled partial reduction of nickel and nickel-copper oxides to obtain a product having consistently high and uniform metal contents and containing controlled amounts of highly-active carbon iinely dispersed throughout the partially-reduced oxides.

It is a further object of the present invention to provide as an essential feature thereof, a novel operation and a unique, easily controllable, unitary apparatus for producing partially-reduced oxides of controlled composition from raw oxides which utilize relatively inexpensive hydrocarbon gas, such as natural gas, to reduce said oxides With markedly low consumption of said gas by simultaneously combining high thermal efliciency together with high concentrations of uncontaminated reducing gas in contact with the oxides.

The present invention also provides as an important but not essential feature the recovery and recirculation of valuable reducing components from the spent exhaust gas produced in the essential oxide-reduction operation.

It is a further object of the present invention to provide unique, partially-reduced oxide products having uniform and consistently high metal contents and controlled carbon contents.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the drawings, in which:

Fig. 1 gives, for purposes of comparison, flowsheet A illustrating a prior art process for producing nickel-copper alloy ingots and now-sheet B illustrating the much more simple and economic procedure for obtaining the same results by the present novel process and apparatus;

Fig. 2 schematically depicts in perspective the location and temperatures of the various zones in an annular oxide-reduction muiile embodying the novel structure of apparatus encompassed by the present invention. It is to be appreciated, however, that divisions between the various zones and the various temperature ranges are of necessity arbitrarily shown in Fig. 2 and that in actual operation said divisions are not sharp but tend to blend into each other at the junctions between adjacent zones;

Figs. 3 and 4 are reproductions of macrophotographs at l0 magnications of two nickel-copper oxide particles, each partially reduced by one of the two embodiments of the essential oxide-reduction operation of the present process. The oxide particle shown in Fig. 3 was partially reduced by employing con-current gas flow and contains only about 9.05% carbon whereas the oxide particle shown in Fig. 4 was partially reduced by employing counter-current gas flow and contains about 3.85% carbon;

Fig. 5 shows a flow-sheet depicting one particular manner of combining the various operations, units of equipment and features of the present invention and, in addition, also includes the optional embodiment in the oxide-reduction operation of recirculation of reducing gases recovered from spent exhaust gases;

Fig. 6 illustrates an elevational view, partly in section, on an annular oxide-reduction muiile which is a preferred embodiment of the present invention; and

Fig. 7 is a detailed'section of the annular muffle structure illustrated in Fig. 6.

Generally speaking, the present invention comprises a novel combination of operations involving the rapid, controlled, partial reduction of raw oxides in a special oxide-reduction muiile of novel structure to produce unique partially-reduced oxide products having consistently high and uniform metal contents and controlled contents of finely-dispersed, highly-active carbon which are then directly convertedinto high-quality metal products by electric or induction-furnace practice without substantial additions of supplementary reducing agents.

Partially-reduced oxides treated by the present novel process are directly melted along with scrap by the usual electric-arc furnace or inductionfurnace technique, the conventional practice of preliminary melting in an acid open-hearth furnace, desulfurizing, etc., prior to duplexing the melt in an electric furnace, being omitted. The purpose of conventional preliminary open-hearth smelting prior to refining and finishing in electric furnaces is necessary mainly to obtain a product suitable for electric-furnace refining since oxides reduced by conventional methods have relatively low and Variable total metal contents which render these oxides unsuitable for direct electric-furance smelting and refining.f

In order to obtain material suitable for electric-furnace refining, it is necessary that the oxides charged into the electric furnace be highgrade, i. e., of uniformly high total metal content, both from the viewpoint of metallurgical quality and also cost. The quality of reduced oxides produced by the prior art methods is not only relatively lower from the viewpoint of total metal content but also is quite variable in metal content, e. g., the variation usually is from about 767Lto about 85% whereas the minimum desirable metal content for direct electric-furnace smelting is :at least about 88% total metal content. These factors render preliminary openhearth melting a necessary operation before electric-furnace rening and deoxidation can be economically and metallurgically feasible. On the other hand, the partially-reduced oxides produced by the present novel process are of sufficiently high and uniform in quality to permit direct smelting, refining and deoxidation by electric-furnace or induction-furnace practice with considerable savings in operating, labor and equipment costs.

In order to clearly demcnstate the marked distinctions and advantages of the present process over conventional processes, two i'owsheets are presented in Fig. 1. Flow sheet A shows a typical prior art process and ow sheet B illustrates the much more efficient, simple and economic process embodying the present invention. in l. ilow sheet A shows the conventional operations for producing cast ingots containing about 76% nickel and 30% copper, such as sold under the trade-mark MoneL from sintered nickel-copper oxide. Flow sheet ,B illustrates the present improved process. Identical amounts of scrap and oxide are shown entering each 'system and 100,000 pounds of the aforesaid nickel-'copper alloy as -ingots are produced by both systems. The advantages ef the present novel process as compared to the production syst-ern employing the Old DlaCliQe ale readily lpalel by Comparing the tvo now sheets. In the latter, a small amount 'of tar coke and oxide Vis placed in the bottl'l Of Ythe electric furnace, mixed With SCT-2p, melted, refined and cast into ingots which comprise approximately 66% of the total tonnage produced. The balance or the oxide is mixed with about 12% tar coke by weight and charged into a gasered, open-hearth furnace Where it is reduced and melted. The reduction and melting operation in the open-hearth furnace is slow and inefficient since the oxideecoke mixture has very poor heat-transfer characteristics. Reduction with Subsequent melting occurs only on `the surface of the charge and any reducing gases, e. g., carbon monoxide, formed by the reaction of the coke with the oxide are rapidly diluted with 'combustion gases and swept out of the furnace, thereby slowing the reducing action and wasting valuable reducing gases. Unreiined molten metal tapped from the open-hearth furnace is de's'ulfurized in the ladle and the sulfur-containing impurities are removed with the slag. De 'sulfurizatiton is necessary due to sulfur pick-up from the coke which has been added to the oxide i'n the open-hearth furnace. This product is transferred to an electric furnace for further refi'nn'g and is then cast into ingots.

In procedures employing the present new process, including the novel oxide-reduction operation, the oxide is partially vreduced in the novel oxide-reducing muilie employing counter-current gas now. The partially-reduced oxide containing a uniform high total metal content and a controlled Vcarbon content is charged directly into the electric furnace, melted, refined and cast into in'gots. A very small amount of tar coke, e. g., up to about 1,000 pounds of tar coke, may be added if desired together with the partially-reduced oxide. In this particular case the optimum total metal content in the partially-reduced oxide is about 91% copper plus nickel together with about 1.5% of carbon finely dispersed throughout the reduced oxide particles.

In the present process, both the conventional mixing and the ladle-destilfurlaing operations have been eliminated. Furthermore, the duplexing operation, i. e., the combi-nation of openhearth and electric-furnace operations, has been eliminated, thereby completely avoiding all delays caused by the unequal tap-to-tap times for the 'two difierent types of furnaces. Since the oxide partially reduced by the novel oxide-reduction operation is discharged from the 'mule with a low-heat content, it can be stored normally and is available for direct charging into the electric furnace at any time without suiering any loss of activity of the contained, deposited carbon. Furthermore, any extra carbon additions (tar coke additions) made in the new system amount to not more than about 15% of the tar colte added during processing by the old system, but even here this small amount of tar coke can be elimina-ted when employing the new process. Since the tar-coke requirement of the new' process is either nil or at the most negligible, the problem of sulur contamination by tar coke is also negligible. A still further advantage of the new process `is the fact that the ratio of scrap to partially-reduced oxide in direct electric-furnace smelting can be varied at will over a much Wider range than when processing by convention-'a1 methods.

The physical properties and the metallurgical quality of the metals and alloys obtained as commercial products as a result of utilizing the process of the present invention is, in every Way, comparable to the quality of the metals and alloys obtained by the more costly and more complicated conventional duplex smelting and rening operations.

The novel oxide-reduction operation in the present process employs hydrocarbon gas, e. g., natural gas, tc obtain the desired high degree of controlled partial reduction or" the raw oxides. It is contemplated that the flow of the gases can either be con-current with or counter-current to the feed of oxide through the reduction mullle, depending on the carbon content desired lin 'the 'final product. It has been discovered that natural raw gas, e. g., a gas containing generally about to about 95% methane, is particularly applicable in the present process.

In an embodiment of the oxide-reduction op eration, the relatively cool, raw, natural gas enters the novel reduction munie through the port from which the partially-reduced oxide is discharged where it aids in cooling said oxide. As the gas flows counter-currently to the downwardly-moving column of oxide and upwardly into the hightemperature reducing zone, the progressively increasing temperature encountered accelerates the reduction reactions. The novel result is a partially-reduced oxide of high, consistently uniform metal content discharging from one end of the apparatus and exhaust gases` resulting from the partial oxidation of natural gas and containing hydrogen, carbon monoxide, water vapor, carbon dioxide, nitrogen, hydrocarbon gases, etc., discharging from the other end of said apparatus.

The various zones and temperatures occuring within the reduction munie when employing counter-current gas flow to obtain partially-reduced oxides oi controlled composition are schematically illustrated in Fig. 2. The cool raw natural 'gas I0, upon entering the oxide-discharge port of the reduction apparatus and upon coming into contact with reduced oxide Il in cooling zone I2, cools said oxide and is in turn preheated. Above the cooling zone, in zone I3, temperatures above about l000 F., e. g., at 'about 1l00 F. and higher, are obtained and some oxide reduction also continues to take place to some extent in this zone. Carbon is precipitated on and dispersed Within the particles of partially-reduced oxide and the remaining gas flows upwardly yinto regions of progressively increasing temperature containing progressively less reduced oxide while, at the same time, continuously reacting with the unreduced oxide in main reducing zone Iii and in primary reducing Zone l5. The carbon which is deposited on the partially-reduced oxide is carried downward with said oxide and, being intimately dispersed on and within the oxide particles f see Fig. e), provides a most excellent, highly-active, reducing agent for the subsequent electric-arc or vinduction-hlrnace direct sin-citing of the reduced oxide, operation le, to produce metal 10a.

The major function of primary reducing zone l5 is to complete the preheating of the oxide to the reduction temperature range, e. g., about 1790 F. to about W F., both by heat vsupplied by the intern-a1 and external heating chambers (see Figs.

6 and '7) of the novel annular mulile and also by absorption ci heat from the hot gases progressing upwardly through the oxide bed. lI'he secondary function of zone le is to initiate the reduction of the oxide since the gases leaving the reducing zone lai still possess potential reducing power.

initial preheating of the entering raw oxide I8 occurs in the zone l@ which is located immediately above the primary reducing zone but which is positioned outside the external heating cham `er oi the muiile (not shown in Fig. 2) Preheating in Zone it is accomplished mainly by the heat absorbed from the large volurne of exhaust gases.

Heat is supplied to zones i2 to l5 by an external heating cham-ber 3e (Fig. 6), for muille diameters over about 5 inches by an internal (core-heating) chamber '2l (Fig. 7), and by the exothermic oxide-reducing reactions. In the present oxide-reduction operation, more gas is employed than is theoretically necessary to reduce the oxide to the desired degree of partialreduction resulting in. an overall negative heat balance. Good heat-transfer characteristics in the novel mullle are therefore a necessary feature in obtaining the excellent results ci the present process. Excellent heat-transfer characteristics are attained without unduly high temperature gradients in muilles or diameters in excess of 5 inches by employing not only an external 'ieating chamber but also an internal or coreheating chamber. in employing counter-current gas flow, the Aupward-moving hot gases serve to uniformly and gradually pre-heat the downwardmoving oxide and the heat is then returned to the incoming gases by the downward movement oi the oxide. The eliiciency of heat recovery is indicated by the fact that the temperature oi the spent, exhaust gases il' (Fig. 2) is generally below about 220 F. Oxide pre-heating is not only desirable from the viewpoint of returning otherwise wasted heat to the si stem but is also desirable from the viewpoint of uniform and gradual preheating of the incoming oxides to gether with initial reduction of said oxides by gases now having only a relatively small reducing potential. This condition serves to prevent excessive rates of reduction. Excess reduction rates, obtained when raw oxide is quicklyexposed to hot, highly-reducing gases may cause sintering or fusion of the reduced oxide which, in turn, would promote bridging in the muile, thereby preventing or hindering iiow of the oxide through the mufle.

The final, partially-reduced oxide product containing finely-dispersed, highly-active carbon has been found to be eminently suitable for subsequent direct melting and rening. Partially reducing, rather than completely reducing, the 0xide together with deposition of carbon in the partially-reduced oxide particles permits a much higher production or "throughput rate for any given size of reduction mullle than can be realized if the oxide is completely reduced and also permits equally rapid conversion to metal in the subsequent melting and refining operations,

Cooling the partially-reduced oxide to at least about 550o F. 0r lower is not diilcult when employing the foregoing particular embodiment of the present process, namely, counter-current ow of gas to oxide. Heat absorbed by the endothermic decomposition of the incoming gas cools the oxide to about 1100 F. with great rapidity. Further heat is absorbed in heating the cool incoming gas up to its decomposition temperature so that the remaining amount of cooling to the required oxide-discharge temperature is relatively small.

As disclosed hereinbefore, the partially-reduced oxide produced by employing counter-current flow of gas to oxide contains finely-dispersed carbon which can be controlled over a wide range by varying the operational factors. The carbon content can be controlled between about 0.4% and about 4.0% by Weight. Certain overall processing requirements, however, may make it desirable to produce partially-reduced oxide containing carbon in amounts lower than about 0.6 The aforesaid low-carbon reduced oxide is produced by employing con-current flow of gas with oxide wherein more of the carbon deposited on and within the oxide particles is oxidized to carbon monoxide or carbon dioxide than is the case when counter-current gas ilow is employed. 1n this embodiment of the present process, the gas is introduced at the top of the muiile along with the raw oxide and withdrawn at the bottom along with the reduced oxide. The carbon deposits on the oxide particles in the upper part of the main reducing zone and most of the carbon thus deposited oxidizes as it passes downward with the oxide through the balance of the main reducing Zone. Carbon content of oxides reduced by this embodiment can be held at values even below about 0.10% by this method, e. g., at about 0.05% or even lower. However, the thermal efficiency of this embodiment of the novel reduction operation is somewhat lower-than when employing counter-current gas flow because in counter-current :dow the heat of the exhaust gases is almost completely transferred to the cold raw oxide entering the Inutile. With con-current ow this heat is lost. Furthermore, with counter-current ilow the heat of the hot reduced material is largely used to heat the incoming gas. With con-current flow this heat is lost. In addition to the heat losses, Cooling of the reduced material to 'below its reoxidation temperature in air, e. g., below about 550 F., becomes more difcult when employing con-current flow; and for large furnaces the extension of the annular muffle into the cooling zone from the reducing Zone becomes a matter of practical necessity.

For producing partially-reduced oxides most economically for direct melting and reiining by electric-furnace practice, it is preferred to employ counter-current flow of gas to oxide because the degree of reduction can be best controlled and carbon is deposited on and precipitated within the iinal product particles in amounts between about 0.i% and about 4%, preferably between about 1.0% and about 2.0% and more preferably in an amount about 1.5% by weight of the nal product. Oxide partially-reduced by concurrent gas low and containing carbon in amounts below about 0.6% usually is not as suitable for direct electric-furnace melting as is oxide reduced by counter-current gas ilow and having higher carbon contents. However, under certain circumstances low-carbon partially-reduced oxide may be required, in which case con-current flow of gas with oxide would be the most feasible embodiment of the oxide-reduction operation to employ. However, by proper control of the operational factors of either embodiment, it is possible to secure a uniform and high degree of reduction together with deposition of controlled amounts of highly-active carbon finely dispersed within the partially-reduced oxide particles which will promote rapid and complete melting and reinch of heating surface to 1.0 cubic inch of annular volume. In an annular muiile, the ratio of mule heating area to muiiie volume is determined by the width of the annular space, indicated by the letter W in Figs. 2 and '7. For example, 6 O, D. 2" I. D., 14 O. D. l0" I. D., and O. D. l6 I. D. muiiies all have an annular Width, or width of oxide bed, of 2 inches and each mufle has a surface area to volume ratio of 1,0. In the art it is well known that the terms O. D. and I. D. means outside diameter and inside diameter, respectively. Similarly, if the width W of the annular space is 3 inches, the aforementioned ratio will be 0.6'7, and if the width is 4 inches, the ratio will be 0.50, etc. Thus, while both heating area and oxide-bed thickness are of primary importance in securing rapid heating of the oxide within the novel annular muflle, both factors may be expressed in terms of the width of the oxide bed. Thus, reducing the width of the annular space decreases the time required to heat the oxide to the desired temperature for reduction.

Another factor which is important in improving heat transferv and which is influenced by the width of the annular space is the velocity of the reducing gas. For example, two tests, i. e., test Nos. 3 and 4, were conducted in two different circular mufes, neither of which contained an internal or core-heating chamber and in which the temperature of the oxide feeding through' the mules was measured at a point on the axis of the mufiie near the bottom of Zone i3 both before and after the reducing gas was introduced in counter-current flow to the movement of the The very considerable effect of rate of gas flow on heat transfer by convection heating can be clearly seen in each of the above tests. The reduction reactions begin as soon as the gas is turned on and the net heat balance is endothermic when there is an excess input of natural gas, as was the case with the tests shown in Table II. Therefore, the increases in temperature obtained by iiowing natural gas through the muflie, as illustrated by the foregoing test data, cannot be attributed to heat released by the reduction reaction since the net heat balance in the system is negative, but must be attributed to the important effect of velocity of gas 110W through the muiiie. The relative gas velocity in an annular mufle is determined by the width of the annular space and by the height of the reducing zone. In other words, the dimensions of the muflie tube have a very important effect on the eiciency of heat transfer in the muilie. Thus, for any given volume of gas input, the shorter the distance between inside and outside walls of the annular reduction chamber, then the higher the ratio of heating surface area to mufile volume, the shorter the width of the oxide bed through which heat must be transferred, and the greater the velocity of the gas flowing through the oxide bed.

Circular, non-annular muflies having an inside diameter in excess of about 5 inches result in heat-transfer characteristics too poor to justify economic commercial operation. The present, novel, annular muflie overcomes this handicap and permits the construction of any desired size of reduction furnace without loss of high heattransfer characteristics. The width of the an-I nular muflie space (W in Fig. 2) is important from the commercial viewpoint and, for economic op eration, this width should not exceed about 5 inches and preferably not exceed about 4 inches, particularly when nickel or nickel-copper oxides are to be treated.

The balance of the test data disclosed in the present specification was obtained in or pertains to one of three furnaces, the dimensions and operating data for which are given in Table III. Test Nos. 15 to 26 and 39 to 48, inclusive, were made in a small-scale, non-annular furnace (furnace A), and test Nos. 11 to 14 and 27 to 38, inclusive, were made in a medium-sized, semicommercial annular furnace (furnace B). Test Nos. 5 to 10, inclusive, were computed for a largescale furnace of the dimensions of furnace C with the exception that the annular width was varied Y Table III Furnace Reduction Zone Data A B C Reducing Zone O. D., inches 3 G 18 Reducing Zone I. D., inches. 0 2 12 Reducing Zone Height, inches 30 63 135 Width of O xide Bed, inches. 3 2.0 3. 0 www 1. 33 1. 00 o. 666

Volume Relative Reducing Gas Vclocities 1 2. 46 3. 75 Oxide Feed Rate, lbs/hr 40 350 3, 000 Reducing Gas Consumption in t 3/lb Oxide 1. 50 l. 50 1. 50 Time in Reducing Zone, min 34. 5 29. 4 41. 3 Time at Reducing Temp., min. 17. 6 14. 4 17. l Reducing Temp., F 1, 700 l, 900 1,900

Since the reduction mufle of furnace A was only 3 inches in diameter (the width of the oxide bed), it was not necessary to provide this furnace with an internal, core-heating chamber. In this case, the high heating surface to mufile volume ratio, narrow width of oxide bed and a relatively high reducing gas velocity for this ratio and width results in good performance without core heating. In larger furnaces, high efficiency is obtained by employing core-heating means. The foregoing muiiles obtain markedly improved results in that there is obtained maximum throughput capacity coupled with unusual and markedly superior heat-transfer characteristics. Another factor controlling the width of the annular muiile space that can be employed is the particle size of the oxide charged, as discussed hereinafter. However, it has been discovered that there is an optimum width of annular mufle space for each specic application of this novel reduction operation and that this width is highly important from the viewpoint of economic practicability. For example, a certain copper-nickel oxide charged into furnace C at a rate of 3000 lbs. per hour will require about 24.2 minutes to reach a temperature of about 1500o F. plus an additional time of about 16 minutes at temperatures between about 1500 F. and about 1900 F. to be reduced about The data given in following Table IV were computed for a furnace having the overall; dimension of furnace C but with the annular width varied, calculations being based on data obtained on furnace B. These data illustrate the effect of varying the width ofthe annular muille space on the time at temperature at a feed rate of 3000 lbs. per hour of oxide in all cases.

From the foregoing data, it may b e seen that when the factor of time at reducing temperature is introduced, the commercially practical opti-- mum width of the annular space is not necessarily the minimum width. For example, use f av l-inch width results in very rapid heating (excellent heat transfer), but the volume of the muiile so reduced that the total time in the heating zone is less than the 16 minutes required to obtain about 75% reduction. At the lother extreme, increasing the width of the annular space above about inches results in such poor heat transfer that the oxide never reaches the desired reduction temperature unless the oxide feed rate is lowered below a commercially acceptable rate. From the foregoing data in Table 1V, it is obvious that the width of the annular space should not be more than about 5 inches nor less than about 1 inch, preferably not more than 4 inches nor less than about 2 inches, for practical purposes.

For any given muiile diameter the eifect 0f increasing inutile height is to increase the production capacity of the unit., In addition to the obvious advantage ofY increasing the length of the reducing zone, an increase in oxide feed rate is obtained which in turn requires an increased ow of reducing gas. This results in higher reducing gas velocities within the muflle which in turn 'improve the heat transfer characteristics of the process. Increased height is always desirable, the only limiting factor. being practical engineering considerations, e. g., initial cost and maintenance cost of excessively high structures, etc.

The maximum particle size that can be treated successfully by the reduction operation of the present process depends mainly upon the eifec tive cross-sectional area of the muilie, i. e., width of oxide bed. For any given area of mufe crosssection, the maximum permissible particle size is that size which will moveV freely downward under the influence of gravity without mechanical C-.lQgging Thus, for the particular muiile dimensions of furnace C described hereinbefore, -a particle size of about 0.75 inch is about the maximum size which can be handled without clogging. However, the preferred maximum particle size in this case is about 0.5 inch since parf ticle sizes larger than about 0.5 inch` in average diameter require somewhat slower rates of feed than are commercially feasible in ordertoV allow time for diffusion of the reducing gases intothe centerof each particle. Consequently, in a furnace of the size of furnace S, the reduction reac-ftion rate decreases appreciably as the particle size increases over about 0.5 inch. However, larger particle sizes can also be successfully re-y duced `provided the dimensions of the annular' muille are also increased to accommodate these larger-sizes.

Although. the maximiun permissible particle size is controlled bythe capacity of the muiiie to handle the oxide without clogging, it has been discovered that the range of particle sizes of the oxide to be treated by thepresent process is a very important factor in the successful operation of' the process- It has been found that if too great, a proportion ofthe oxide being treated is of' too fine a particle size, this fine fraction tends to cake or 'bridge in the reduction Inutile thus blocking the mui/lie and preventing the oxide from properly feeding through the muille. To obtain' the optimum rate of feed, for instance in a furnace of the dimensions of-v furnace C', it is preferred that the minimum particle size i-n the oxide feed Ybe maintained at about 0-.1 inch a1- thoughv successful reduction can also be obtained with feeds containingv oxide particle sizes down to about, 0.05 inch (about 14 mesh) provided the percentage of these fine particles in the feed is not too high, e. g., no more than about 10% by volume of the total feed', and provided thata clean sizing separation at the particle size of about 0.05 inch can be made. In order to allow for screening ineiiiciencyand variations in particle size distribution which can occur in com-4 mercial scalel operations, screening at about- 0.1 inch, e. g., from about 6V to about 8 U. S. standard mesh, is recommended. The preferred range of particle size, of about 0.1 inch to about 0.5 incl-1, as contemplatedv by the present invention for vtreatment in a mufe ofthe type of furnace C is important from the viewpoint of obtaining the best results. However, good results can ber obtained in larger size commercial equipment with wider particle size ranges, e. g., about l0.05 inch to about 0.75 inch, provided that the screening facilities are sufficiently good to obtain cleanminirnum and maximum particle size separations.-

'Ilhe determination of the actual particle, size rangel to be employed with any particular size of apparatus is dictated by at least three considerations. First, the dimensions and the shape of the muilie are important factors in determining the particle size range that may be employed mechanical clogging and/ or caking is to be avoided. Second,y the reduction rate decreases as the particle size increases above about 0.4 to about 0.5 inch, the degree of reduction depending on the shape and porosity` of the particles and the copper content of the oxide being treated. Third, the success of the present invention depends on intimate contact of the reducing gases with the oxide particles. Conditions favoring intimate contact between oxide and gas are a uniformly cereus, iride bedY andv as small an oxide particle size as is consistent with porosity of the bed with out obtaining caking or bridging in the muffle. When the range of particle size of the oxide is wide, the overall porosity of the bed decreases due mainly to the fact that the finer particles tend to segregate in the interstices between the larger particles, thereby forming dense cakes which prevent free uniform passage of the reducing gases. In this case, the gas will tend to channel: throughv or around the segregated fines; and the result is. a lower degreeV of reduction of the finer particle sizes as illustrated in following Table V, although normally it would be expected that the finer sizes would experience a higher degree of reduction. Furthermore, the tendency of too fine particles to cake and sinter, thereby clogging the mule tube, is a further reason why the minimum particle size is important and must be controlled.

For any given set of muflie dimensions having a minimum heating surface area to muifle volume ratio of at least about 0.4, the optimum or permissible maximum and minimum particle size for the particular muifle must be determined by actual test. The mufe cross-section is an important factor and increasing the muffle crosssection, particularly with respect to the width of the oxide bed, not only permits treatment of finer particle sizes but also permits treatment of a larger percentage of fine particles in comparison to the particle size range and minimum particle size permissible for treatment in smaller muifles. Furthermore, the permissible range and distribution of sizes determined for any particular apparatus also controls the percentage of fine particles to be allowed. For instance, if the maximum allowable particle size for a specic apparatus is determined by tests to be about 0.2 inch, the minimum permissible particle size can be as low as about 0.04 inch and the percentage of sizes between 0.04 inch and 0.1 inch can be as high as about 50% of the entire feed.

Another important factor in determining the permissible range and distribution of particle sizes is the reduction temperature employed. Thus, the lower the minimum particle size and/ or the higher the percent of the finer sizes which are permissible, the lower is the reduction temn perature which can be successfully employed. Thus, for a mufle having the dimensions of furnace C when employing reduction temperatures between about 1800 F. and aboutr2000 F., e. g., about 1900 F.; it is preferred that the particle sizes be between about 0.05 inch and about 0.5 inch with not more than about of the total feed being in the particle size range of about 0.05 inch to about 0.1 inch.

To illustrate the effect of particle size on the degree of reduction of both nickel oxide (containing only about 5% copper) and nickelcopper oxide (containing about 19% copper),

each type of oxide was partially reduced in an annular mufe of the dimensions of furnace B. Four particle size ranges were screened from sample of each type of partially-reduced oxide and the total metal content (percent copper plus nickel) was analyzed in each sample. The comparative data are given in the following Table V:

Table V Percent Copper plus Nickel in Final Product It is to be noted that the maximum yield, measured by the total metal content, for both types of oxide is obtained in the narrow particle size range of 0.263 inch to 0.371 inch which lies approximately in the center of the preferred range of about 0.1 inch to about 0.5 inch. To illustrate le the effect of increasing the particle size range on the degree of reduction, three tests were made on nickel-copper oxide at 1'700o F. under similar conditions of time, feed rate, and atmosphere, and in a furnace of the dimensions of furnace A. The data are given in the following Table VI:

Table VI P t. 1 l C Percent a1' 1c e Size opper p us Tesi' NO Range (inch) Nickel in Final Product 15 0.051 t0 0.371 89.4 0.051 to 0.310... 91.3 0.051 to 0.l25 92.1

It is apparent from the foregoing data that the more narrow the range of particle size, the higher is the total metal content and the greater is the degree of reduction of the nal partially-reduced product.

In commercial operation and employing apparatus of the dimensions of furnace B, an oxide feed rate of at least about 1'75 pounds of oxide per hour, preferably about 350 pounds of oxide per hour, is desired. For a muie of the dimensions of furnace C, the desired oxide feed rate for economic operation is at least about 1500 pounds of oxide per hour, preferably about 3000 pounds of oxide per hour. To obtain these high feed rates and, at the same time, to obtain a final reduced oxide product containing over 88%, preferably over 90%, total metal content, it has been discovered that higher temperatures in the 1500o F. to 2000 F. range, preferably between about 1700o F. and l900 F., are most beneficial in that the rate of heat transfer is markedly increased and the nal product, after treatment in the foregoing temperature ranges, averages between about 90% and 95% total metal content. The following Table VII gives data illustrating the effect of Various reduction temperatures upon the reduction of a copper-nickel oxide in a mule of the dimensions of furnace A, all other operating conditions being maintained substantially constant.

Table VII Final Prod- Test N0 Reduction Feed Rate, Gas Input, uct, Percent Temp., r. lbs/hr. Fu/lb. Cui-Percent 1, 40. 0 1. 50 82.0 1,300 39. 2 l. 53 86. 3 l, 500 40. 3 l. 47 91. 6 l, 600 39. 8 1. 48 98. 2 1, 700 39. 0 1. 53 93. 9 l, 800 38. 3 1. 52 94. 6 l, 900 37. 9 l. 58 95. 3

It is to be noted that at substantially the same oxide feed rate and input rate of natural gas, there is a definite increase of total metal content in the partially-reduced oxide product as the temperature is increased. An upper limit of about 2000 F. for the reduction temperature is desirable solely from the View point of apparatus deterioration and is not restricted at this particular maximum value due to any change in the nature of the reduction reactions causing a decrease in the total metal content of the treated product. It is also not desirable that the temperature be lower than about 1500 F. purely from the viewpoint of commercial practicality. For instance, a rate of feed of about 35 to 45 pounds of oxide per hour in a mufle of the dimensions of furnace A and selected to give about 90% to aoeaom about 92% total'V metal vcontent at about 1500 F. does not produce anywhere near this total metal value if treated at 1100o F. since the reduction reaction is much slower at this low temperature. In order to obtain a satisfactory 'uniform product of the desired high metal content, the feed rate must be reduced to only a 'fraction of the feed rate when employing temperatures above about 1500" F. The following Table VIII illustrates the feed rates necessary to obtain a satisfactory product at temperatures of 1100 F., 1300" F. and 1500o F. in a muiiie of the dimensions of furnace A.

Table VIII *Data for test No. 20 is also presented in Table VII.

A most important factor affecting the production rate, i. e., the rate of feed of oxide, for any given set of operating conditions is the copper content in the oxide being treated by the present process. In order to illustrate the effect of copper content in accelerating the feed rate While obtaining satisfactory results, a series of tests were made in a mufile of the dimensions of furnace B in which the oxides contained both nickel and copper but wherein the copper content varied in each test from a low value of 4.8% copper to a high value of 19.2% copper. These various oxides were all reduced at l900 F. by the novel reduction operation, such as is illustrated by the flow-sheet in Fig. 5, employing the reducing equipment of the preferred design shown in Figs.

6 and '7. The optional gas recovery and recirculation system was not used in these tests.

G. 1 238 l, 900 l. 41 92. 1 11. 2 286 1, 900 1. 43 98. 0 10. 7 303 l, 900 1. 58 91. 8 11. 2 310 1, 900 l. 39 92. 8 1,1. 2 331 l, 900 1. 38 91. 8 19. 2 285 l, 900 1. 68 9.4. 8 10. 2 392 1, 900 1. 53 92. 2 19. 2 397 l, 9U() 1. 51 91. 5 19. 2 421 l, 900l 1. 42 92. 3

spectively), the respective total metal contents show a 3.9% difference in favor of the high-copper oxide in spite of the fact that the high-cop per oxide feed rate was somewhat faster. 'Ihis indication of a slower reaction rate for the reduction of low-copper oxide as compared to the is contemplated that the partially-spent reaction rate Afor the reduction ofvr high-copper lcontent be very high, although the latter is also very desirable. In other words, it is more important that the degree of partial reduction be controlled to produce a consistently uniform metal content rather than to attempt to more completely reduce the oxide to obtain very high total metal contents. Thus, a degreey of partial reduction between about` and about 75% (about 90% to about nickel content) is much viewpoint of the commercial control of` Subsc--Y quent smelting operations than is a higher'. degree of reductionv which varies between about '75% and about 95% (about 92%vv to about 96%v total copper plus nickel) .Y The desired uniformity of produ-ct having reductions inV the. latter higher range, e. g., from 92% to 96% copper plus nickel, can be obtained at the expense of a lowered throughput capacity, particularly for reductions in excess of about 85% (about 94% copperplus nickel). However, it is technically possible to obtain any desired degree of reduction with. the reduction operation and apparatus. Degrees of reduction up to about 85% or 90% are obtainable in one single passage of the oxide through the reduction muflie. To obtain still higher reductions, two or more passages of the oxide through the reduction muilie are usually re, quired. Nevertheless, for` any given muifle, degrees of reduction in excess of about tend to decrease the throughput capacity more and more rapidly as the degree of reduction is ine creased. Therefore, the optimum` degree of ree duction in any particular situation depends in large part' upon the contemplated subsequent processing operations and also upon the ecoa nomics of that particular situation.

The metal content of the raw or sintered nickel and nickel-copper oxides such as contemplated for treatment by the present process usually is about '75% to about 80%, essentially all of which is combined. As the oxides are reduced, free or uncombined metal is formed in increasing amounts. However, where Values for total metal content of the nal product are given in the present specification, it is not meant that these values represent free or uncombined metal but represent free metal plus remaining combined or oxidized metal. Thus, for a reduction of about 75% which is equivalent to a total metal content of about 92%, the free metal content of the final reduced product is about 69%, the balance being combined metal.

Fig. 5 is a flow sheet illustrating the preferred overall process embodying the present invention employing countercurrent flow of natural hydrocarbon gas to oxide to obtain a partially-reduced oxide which is then directly smelted and refined to produce a high-grade metal product. As an embodiment of this preferred overallprocess, vit exhaust 92% total copper plus more desirable from the gases can be treated for the separation of reducing components from non-reducing components in the exhaust gases, e. g., the separation of hydrogen, carbon monoxide and hydrocarbon from carbon dioxide, water vapor and possibly nitrogen. The partially-spent exhaust gases can be treated for recovery of hydrogen, carbon monoxide, hydrocarbons, carbon dioxide, etc., in a recovery system such as indicated within the area bounded by dotted lines in the now-sheet shown in Fig. 5. From a commercial viewpoint, recovered reducing gases, e. g., carbon monoxide, hydrogen and hydrocarbon gases, can be utilized in various ways, for instance, as reducing atmospheres in heat treating furnaces or, preferably, as a supplementary supply of reducing gas for the present process. In addition, carbon dioxide can be recovered as a commercial byproduct.

For instance, Fig. shows that the partiallyspent exhaust gases are drawn by means of a suitable pump through conduit 32 into a condenser33 to remove the bulk of the Water vapor. The gases from the pump outlet now containing hydrogen, carbon monoxide, hydrocarbons, carbon dioxide, and inert gases (mainly nitrogen) continue into the bottom of a carbon dioxide absorbing unit 34 of commercial design utilizing aqueous monoethanolamine solution as the absorbing agent. The carbon dioxide on passing upward through the absorbing unit with the reducing gases is removed by the downward-moving cold amine solution. The cold amine solution on leaving the bottom of the absorbing unit with its burden of carbon dioxide passes through a heat exchanger 35 to partially cool carbon dioxide-free amine solution that is then introduced at the top of the absorber unit. The carbon dioxide-containing amine solution leaving the unit is thereby preheated before its entry into the top of the amine solution reactivator 36. Heat introduced into this unit causes the amine solution to release the carbon dioxide which passes upward through a Water cooler where vaporized and entrained amine solution is condensed and returned to the reactivator. Recovered carbon dioxide is withdrawn from the cooler as a valuable by-product. The hot amine solution, now free from carbondioxide, is drawn off at the bottom of the reactivator by a pump and passed through the heat exchanger 35 where it is partially cooled, thereby heating the out-going carbon dioxide-containing amine solution from the absorber. The partially-cooled, carbon dioxide-free amine solution continues on from the heat exchanger to a water cooler 31 where it is cooled to the proper' temperature for absorbing carbon dioxide and then returned to the absorber thus completing the absorption cycle. Reducing gases coming off the top I" the absorber 34 contain hydrogen, carbon monoxide, hydrocarbons, and a small amount of inert gases, such as nitrogen, but are essentially free from carbon dioxide and water vapor. These reducing gases are available for reintroduction into the reduction mule together with raw natural gas. Thus, the high concentrations of reducing components in the gas necessary to obtain maximum reduction of oxide at a rapid rate can be obtained with a minimum consumption of raw gas. The feed rate of oxide or, in other words, the furnace throughput capacity can thereby be markedly increased; `'and the heat requirements per unit weight of oxide reduced are considerably lowered since heat units, which other- Wise. would be necessary to decompose large excesses of raw gas, are utilized instead for heating the oxide to the required reducing temperature.

By recovering` and re-circulating unoxidized combustibles and hydrocarbons contained in the partially-spent exhaust gas, more complete uti-- lization is made of the total reducing potential present in the original raw gas and, as a result, the actual amount of gas consumed per unit Weight of oxide reduced more closely approaches. the ideal or theoretical oxidation-reduction ratioof about one cubic foot of West Virginia natural gas per pound of oxide. In this manner, for any given feed rate, the percentV total metal con-v tent obtained in the final reduced product is increased; and the consumption of gas per pound of oxide thus reduced is substantially lowered. The benefits derived from treating partiallyspent exhaust gases to recover therefrom the active reducing components and re-circulating said recovered reducing components back through the reduction muflle are illustrated by the data presented in the following Table X. The data for test Nos. 44 to 48, inclusive, were obtained by re-circulating recovered reducing gases and the data for test Nos. 39 to 43, inclusive, were obtained by employing a large excess of raw natural gas only, e. g., 50% excess, to supply the concentration of reducing components necessary to obtain the required degree of reduction. The results shown in Table X were obtained in furnace A, the temperature being maintained in all cases at about 1800 F.

liti. D.=Not determined. l:Balance of 1re-circulated gas mainly hydrocarbons.

From an analysis of Table X, it can be seen that re-circulation of recovered reducing gases increases the degree of reduction obtained or alternatively, increases the production or throughinert gases, such as nitrogen, presentA in the raw natural gas used for reduction. The quantity of valuable reducing components `lostin this escaping gas is largely determined by the quantity of natural gas introduced into the mule and the degree of reduction obtained. For example, on the assumption that r% reduction is required, this theoretically would require about 0.75 cubic foot of gas per pound of oxide feed. Therefore, if

2l 75% reduction is attained, any natural .gas indeduced inte 'the faune in excess of abeut offs :cubic 'foot per pound of oxide feed can be exhausted through the charging ein in the form f partially-'spent reducing gases. 'The amount cf excess natural gas introduced into the rnuie is 'an `amount su'cie'nt only to prevent excessive build-up Vof inert gases in the recovered and re- 'circulate'd reducing gases. Several methods exist of controlling bleeding of partially-spent exhaust gas through the charging bin to .prevent excess build-up of the inert gas components in lthe munie. The preferred method is the 'one hereinbefore described and is preferred largely on the 'basis of the simplicity 'of control 'which itprvides Increasing the input of natural gas above the theoretical value serves to increase considerably the heat requirements for the system, the excess heat being utilized primarily for 'decomposing th excess hydrocarbon gas Iwhich is exhausted ron the mui'e before its reducing potential has been profitably used. ThereforeLfor most economical production on a commercial scale, recovery and re-use of these reducing components in the par,- tially-spent exhaust gas is 'a desirable, although not an essential, feature of the present in vention, as shown by the data in the foregoing Table This is especially true where an outlet exists for the sale of the carbon dioxide recovered as ley-product.

Figs. 6 and 7 are sectional elevational views of a preferred structure' of the novel, annular, oxidereduction munie of the present invention. In 'ore der to obtain the `high degree of operating efficiency whereby high concentrations of uncon-` taminated reducing gases together with excel-- lent heat-transfer characteristics are econonii'- cally obtained, it is necessary to employ the present novel structure ofereduction inutile. vA preferred embodiment of the complete assembly of novel annular reduction munie is illus= trated in Fig. 6'. The core-heating chamber, flame tube and annular oxide-reduction chainber portions of theannular munie are shown in detail in Fig. 7. This 'novel structure is necessary to prevent excessive lowering of thermal efficiency when munie diameters exceed about 5 inches. The example of the novel munie Vstructure illus-- trated in the aforementioned figuresl involves supplying heat to the core of the downward moving annular column of oxide as well as to the outside of said annular column of oxide. This is accomplished by providing an annular oxideieduction chamber 20 (Fig. 7) for the downward passage of the oxide. The inside wall of the annular oxide-reducing chamber is common to the wall of the interior, closed-end, ccire-lieat= ing chamber 2l (Fig. '7) the heat being provided, for instance, either by a semi-long-lame burner or by a partial-premix burner inserted vtherein and comprising name tube 'A2 (Fig. 7) and flame-- retention tip 23 (Fig. 7). However,- any typehof burner may be usedprovided it satisfies the requrement of even, controlled distribution of heat. The outside wall of said annular oxide-reducing chamber is common to the interior wall of the exterior combustion muflle 24 (Fig. 6) to which heat is supplied preferably by tangentially=firing gas burners 25 (Fig. e arranged sph-any relative to one another. l

Control of the rate of combustion of the heat/'j ing gases applied both externally and internally to the annular oxide-reducing chamber is effect; ed by means known to those skilled in the art. Although heat can be supplied to the outside wall and to the core of the annular reduction chamber fromelectrlc-power seurce's. e.. g., electricheating elements;r 'tlispreferable-that'the source of:` heat. be; obtained by thel combustion of gas, oil or powderedfuelamore preferably by the combustion of the same-.natural gas which is introduced. into the annular reductionr chamber.. Except inavery few areas where electric power is very cheap in comparison to the cost ofA gas, oil` or c oal, electric power is the least desirable source of heat for the oxide-reduction operation. A` very important factor favoring employment of natural gas,. oill and powdered` coal as the source of heat is that the atmosphere produced. by the combustin of these fuels", particularly natural gas, `c'a'n be easily controlledy tocontain essentially no free oxygen, i'. e., can be controlled to produce neutral to reducing" atinospheresl This is' of great importance i-n p'i'olori'girigy the service life of metallic nufiles", particularly when operated at t'eiiiperatV `es` above about 1500" Fl The muflle is' preferably constructed of heat-resistant metal, more prefer-ab y a ickeI-chr'ome-iron alloy sold under the trade-niark Iric'onel."

After passage through the reducing chamber. th'rdced Xld' is; Cooled t at least below its reoxidatiori temperature in air, e. g., to at least about 550' Fi Where the flow of gas is countercurrent to the movement' of oxide, this cooling Of tl reduced X'ld t abt 55.0 F. O1* lOWel is effected by the incoming, cold, raw, natural gas'v and also by water-ld chamber 26 (Fig. 6)

from whenceeit is discharged via a novel discharging nichanisi 2T to bin 23 (Fig'. 6). Where the flow of gasis concurrent with `the movement of oxide, the cooling o f the reduced oxide is almost solely effected by efficient heat transfer between water-cooled chamber 2G and the reduced oxide. Discharge mechanism 21 is the only continuously moving mechanical part in the entire novel reductiony apparatus. This mechanisxn serves to regulate the rate of feed of the material through the apparatus but is not a gas-'tight seal. In effect, the column of reduced oxide rests on a shelf or table within the discharger housing. The discharger blade, located well below the end of the munie water jacket 25,

gently pushes the reduced oxide off the shelf by a slow reciprocating motion. Since there is adequate space between the table-blade combination and the end of the munie waterjacket, there is no shearing of the ductile, reduced product; and cc )nsequentlyi wear of the moving blade is negligible. In other words, since this mechanism comes into contact'only with reduced oxide of high metal content and not with unreduced oxide,

it is not subjected to extremely high abrasive action of unreduced raw oxides. Furthermore, the carbon deposited on and within the reduced oxide particles servesl as an excellent lubricant for the movement of both' the blade and the reduced oxide across the surface of the table. As a result, this mechanism is relatively troublefree in operation and has an unusually long serviceY life.

The exact maximum temperature to which the reduced oxide must be cooled is influenced by the degree of activity of the reduced oxide; The gastight seals 29 and 3G (Fig.` e) at the receiving and discharging ports of bin 2B', respectively, are so arranged that when one seal is open, the other is closed, thereby substantially excluding diluting and/or oxidizing agents, such as air, from thc munie; In employing counter-current now of gas to oxide, the gas is introduced` into the munie through gas-inlet port 3| (Fig. (i).

In the presentspecication, wherel any total metal content values (per cent copper plus nickel) are given, these values represent analyses made. on a carbon-free basis. Also, where the termv nickel-copper oxide is employed, it is meant. that said oxide is mainly a mixture of copper and nickel oxides although it is possible that; compounds of copper oxide and nickel oxide, together with some iron oxide, silica, etc., might also be present.

It is to be observed that the present invention. provides a novel process for producing metal from raw oxides, particularly nickel-containing oxides, which comprises reducing raw oxides of controlled particle size with hydrocarbon gases,l particularly methane, to provide reduced oxide products having consistently uniform and high total metal contents and controllable, consistently uniform contents of highly-active carbon nely dispersed throughout Vthe reduced oxide particles and then directly smelting and refining said reduced oxides without substantial additions of supplementary reducing agents. The foregoing novel process, when employed in the production of metal from raw oxides of said metal, results in the elimination of Various complicated, expensive, timeand space-consuming operations necessary when producing metal from raw oxides by prior art methods and provides reduced oxides which are directly converted to metal by electric-- are or induction-furnace practice.

Furthermore, the invention provides a novel unitary reduction apparatus which combines the characteristics of excellent heat transfer between heat source, gases and oxide and high concentrations oi uncontaminatedreducing gases in contact with the oxides.

Moreover, the present invention provides a new product, heretofore unobtainable by conventional processes, which is a partially-reduced metallic oxide having a consistently high and uniform metal content and having a controlled, uniform, highly-active carbon content nely dispersed throughout the reduced oxide particles.

Although the present invention has been described in conjunction with certain preferred embodiments, it is to be understood that modications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Thus, metallic oxides having oxygen dissociation pressures comparable to those of nickel oxide and copper oxide, including the oxides of lead, bismuth, cobalt, etc., can also be reduced by the present process regardless of whether or not nickel oxide and/or copper oxides are also present. However, cobalt oxide is the oxide most likely to be associated with nickel oxide and/or copper oxide and the present invention is particularly applicable to the treatment of the oxides of the metals cobalt, nickel and copper which have the atomic numbers 2'7, 28 and 29, respectively. Such variations and modiiications are to be considered within the purview of the application and the scope of the appended claims.

.We claim:

1. A process for controlled reduction of oxides of metal having atomic numbers from 27 to 29 to obtain partially-reduced oxide of consistentlyuniform, high, total metal content and containing controlled amounts of uniformly dispersed, finely-divided, highly-active carbon and capable of being directly converted into high-quality metal without substantial additions of supple- 24 mentary reducing agents which comprises establishing a substantially vertical annular column of at least one of said oxides having a particle size between about 0.1 inch and about 0.5 inch, said column having an effective width between about 2 inches and about 4 inches and having a ratio of surface area to volume of at least about 0.5; heating said oxide in a single operation to a temperature between about 1700 F. and about 1900 F. out of contact with combustion gases and in contact with countercurrently flowing hydrocarbon gas containing about 75% to about methane to obtain controlled partial reduction of said oxide to a uniform total metal content between about 88% and about 95% and to obtain controlled vuniform dispersion of about 0.4% to about 4.0% finely-divided, highly-active carbon within the particles of partially reduced oxide; and cooling said oxide in a non-oxidizing atmosphere to a temperature below at least about 550 F.

2. A process for controlled reduction of oxides of metal having atomic numbers from 27 to 29 to obtain partially-reduced oxide of consistentlyuniform, high, total metal content and containing controlled amounts of uniformly-dispersed, finely-divided, highly-active carbon and capable of being directly converted into high-quality metal without substantial additions of supplementary reducing agents which comprises establishing a substantially vertical annular column of at least one of said oxides having a particle size between about 0.04 inch and about 0.75 inch, said column having an effective width between about 1 inch and about 5 inches and having a ratio of surface area to volume of at least about 0.4; heating said oxide in a single operation to a temperature between about '1500 F. and about 2000 F. out of contact with combustion gases and in contact with countercurrently flowing hydrocarbon gas to obtain controlled partial reduction of said oxide to a uniform total metal content of at least about 88% and to obtain controlled uniform dispersion of about 0.4% to about 4% finely-divided, highly-active carbon within the particles of the partially-reduced oxide; and cooling said oxide in a non-oxidizing atmosphere to a temperature below at least about 550 F.

3. A process for controlled reduction of oxides of metal having atomic numbers from 27 to 29 to obtain partially-reduced oxide of consistentlyuniform, high, total metal content and containing controlled amounts of uniformly-dispersed, nely-divided, highly-active carbon and capable of being directly converted into high-quality metal without substantial additions of supplementary reducing agents which comprises establishing a substantially vertical annular column of at least one of said oxides having a particle size between about 0.1 inch and about 0.5 inch, said column having an effective width between about 2 inches and about 4 inches and having a ratio of surface area to volume of at least about 0.5; heating said oxide in a single operation to a temperature between about 1700 F. and about 1900 F. out of contact with combustion gases and in contact with concurrently flowing hydrocarbon gas containing about 75% to about 95% methane to obtain controlled partial reduction of said oxide to a uniform total metal content of about 88% to about 95% and to obtain controlled uniform dispersion of about 0.05% to about 0.6% finely-divided, highly-active carbon within the particles of the partially-reduced oxide; and

25` cooling said oxide in a nonexidizifig atiisphere to a temperature below` atleast about 550 F. Y

. 4.,A process for Acontrolled reduction ofoxides of metal having. atomic numbers from 27 to 29 to obtain partially-reduced oxide of consistentlyuniform, high. total metal content andcontaining controlled amounts of uniformly-dispersed, finely-divides, mercy-activ 'carbn and capable of being directly converted into high-quality metal without substantial additions of supplementary reducing agents which comprises establishing a substantially vertical annular column of at least one of said oxides having a particle size between about 0.04 inch and about 0.75 inch, said column having an effective width between about 1 inch and about 5 inches and having a ratio of surface area to volume of at least about 0.4; heating said oxide in a single operation to a temperature between about 1500 F. and about 2000 F. out of contact with combustion gases and in contact with concurrently flowing hydrocarbon gas to obtain controlled partial reduction of said oxide to a uniform total metal content of at least about 88% and to obtain controlled uniform dispersion of about 0.05% to about 0.6% finely-divided, highly-active carbon within the particles of the partially-reduced oxide; and cooling said oxide in a non-oxidizing atmosphere to a temperature below at least about 550 F.

5. A process for controlled reduction of oxides of metal having atomic numbers from 27 to 29 to obtain partially-reduced oxide of consistentlyuniform, high, total metal content and containing controlled amounts of uniformly-dispersed, finely-divided, highly-active carbon and capable of being directly converted into high-quality metal without substantial additions of supplementary reducing agents which comprises establishing a substantially vertical annular column of at least one of said oxides having a particle size between about 0.04 inch and about 0.75 inch, said column having an effective width between about 1 inch and about 5 inches and having a ratio of surface area to volume of at least about 0.4; heating said oxide in a single operation to a temperature between about 1500 F. and about 2000" F. out of contact with combustion gases and in contact with flowing hydrocarbon gas to obtain controlled partial reduction of said oxide to a uniform total metal content of at least about 88% and to obtain controlled uniform dispersion of about 0.05% to about 4.0% finely-divided, highly-active carbon within the particles of the partially-reduced oxide; and cooling said oxide in a non-oxidizing atmosphere to a temperature below at least about 550 F.

6. As a new article of manufacture, a partiallyreduced particle of oxide of metal having atomic numbers from 27 to 29, said particle having a size of about 0.1 inch to about 0.5 inch and containing a total metal content of about 88% to about 95% together with about 0.4% to about 4.0% highly-active, finely-divided carbon uniformly dispersed within said partially-reduced particle.

7. As a new article of manufacture, a partiallyreduced particle of oxide of metal having atomic numbers from 27 to 29, said particle having a size of about 0.1 inch to about 0.5 inch and containing a total metal content of about 88% to about 95% together with about 0.05% to about 0.6% highly-active, finely-divided carbon uniformly dispersed within said partially-reduced particle.

8. As a new article of manufacture, a partiallyaccessi Cil' reduced particle ofxid ofirfietal having atomic numbers from, 2,7 to 29,saidp'article having a size of 'about004uinch `to about 0.75 inch and containing a total nmetal content of at least about 88% r together withabout 0.05% .to a\bout.4.0% highly-active; hely-divid'ed carbon uniformly dispersed Awithin `'said .partially-reduced particle.

9. Asa new article of manufacture, a partiallyreduced particle of oxide of'metal having atomic numbers from '27156 29, said particle having a size of about 0.04 inch to about 0.75 inch and containing a total metal content of at least about 58% together with about 0.4% to about 4.0% highly-active, finely-divided vcarbon uniformly dispersed within said partially-reduced particle.

l0. As a new article of manufacture, a partially-reduced particle of a nickel-containing oxide, said particle having a size of about 0.04 inch to about 0.75 inch and containing a total metal content of at least about 88% together with about 0.4% to about 4.0% highly-active, nely-divided carbon uniformly dispersed within said partially-reduced particle.

1l. A process for controlled reduction of a nickel-containing oxide to obtain partially-reduced oXide of consistently-uniform, high, total metal content and containing controlled amounts of uniformly dispersed, nely-divided, highlyactive carbon and capable of being directly converted into high-quality metal without substantial additions of supplementary reducing agents which comprises establishing a substantially vertical annular column of said oxide having a particle size between about 0.1 inch and about 0.5 inch, said column having an effective width between about 2 inches and about 4 inches and having a ratio of surface area to volume of at least about 0.5; heating said oxide in a single operation to a temperature between about 1700 F. and about 1900 F. out of contact with combustion gases and in contact with counter-currently ilowing hydrocarbon gas containing about 75% to about methane to obtain controlled partial reduction of said oxide to a uniform total metal content between about 88% and about 95% and to obtain controlled uniform dispersion of about 0.4% to about 4.0% finely-divided, highly-active carbon within the particles of partially reduced oxide; and cooling said oxide in a non-oxidizing atmosphere to a temperature below at least about 550 F.

12. A process for controlled reduction of a nickel-containing oxide to obtain partiallyreduced oxide of consistently-uniform, high, total metal content and containing controlled amounts of uniformly-dispersed, finely-divided, highly-active carbon and capable of being directly converted into high-quality metal without substantial additions of supplementary reducing agents which comprises establishing a substantially vertical annular column of said oxide having a particle size between about 0.04 inch and about 0.75 inch, said column having an effective width between about 1 inch and about 5 inches and having a ratio of surface area to volume of at least about 0.4; heating said oxide in a single operation to a temperature between about 1500 F. and about 2000 F. out of contact with comb-ustion gases and in contact with countercurrently flowing hydrocarbon gas to obtain controlled partial reduction of said oxide to a uniform total metal content of at least about 88% and to obtain controlled uniform dispersion of finely-divided, highly-active carbon within the particles of the partially-reduced oxide; and

. 27 28 ooling said oxide in a, rich-oxidizing atmosphere Number Name Dat to a. temperature below at least about 550 F. 1,480,212 Lamothe Jan. 8, 1924 HARRY E. TSCHOP. 1,550,271 Macklind et al Aug. 18,' 1925 J QSEEH EDWIN CARTER. 1,848,710 Gustafsson Mar. 8, 1932 CHARLES BRUCE GOODRICH. 5 2,166,207 Clark July 18, 1939 2,256,536 Udy Sept. 23, 1941 Rferences Cited in the le of this patent 2,296,841 Y Gardner Sept. 29, 1942 UNITED STATES PATENTS 2,302,615 LIIZ NOV. 17, 1942 2,417,949 Riveroll Mar. 25, 1947 Number Name Date 1,075,135 Alton oct. '1, 1913 1-

Claims (2)

1. 5. A PROCESS FOR CONTROLLED REDUCTION OF OXIDES OF METAL HAVING ATOMIC NUMBERS FROM 27 TO 29 TO OBTAIN PARTIALLY-REDUCED OXIDE OF CONSISTENTLYUNIFORM, HIGH, TOTAL METAL CONTENT AND CONTAINING CONTROLLED AMOUNTS OF UNIFORMLY-DISPERSED, FINELY-DIVIDED, HIGHLY-ACTIVE CARBON AND CAPABLE OF BEING DIRECTLY CONVERTED INTO HIGH-QUALITY METAL WITHOUT SUBSTANTIALLY ADDITIONS OF SUPPLEMENTARY REDUCING AGENTS WHICH COMPRISES ESTABLISHING A SUBSTANTIALLY VERTICAL ANNULAR COLUMN OF AT LEAST ONE OF SAID OXIDES HAVING A PARTICLE SIZE BETWEEN ABOUT 0.04 INCH AND ABOUT 0.75 INCH, SAID COLUMN HAVING AN EFFECTIVE WIDTH BETWEEN ABOUT 1 INCH AND ABOUT 5 INCHES AND HAVING A RATIO OF SURFACE AREA TO VOLUME OF AT LEAST ABOUT 0.4; HEATING SAID OXIDE IN A SINGLE OPERATION TO A TEMPERATURE BETWEEN ABOUT 1500* F. AND ABOUT 2000* F. OUT OF CONTACT WITH COMBUSTION GASES AND IN CONTACT WITH FLOWING HYDROCARBON GAS TO OBTAIN CONTROLLED PARTIAL REDUCTION OF SAID OXIDE TO A UNIFORM TOTAL METAL CONTENT OF AT LEAST ABOUT 88% AND TO OBTAIN CONTROLLED INIFORM DISPERSION OF ABOUT 0.05% TO ABOUT 4.0% FINELY-DIVIDED, HIGHLY-ACTIVE CARBON WITHIN THE PARTICLES OF THE PARTIALLY-REDUCED OXIDE; AND COOLING SAID OXIDE IN A NON-OXIDIZING ATMOSPHERE TO A TEMPERATURE BELOW AT LEAST ABOUT 550* F.
2. 8. AS A NEW ARTICLE OF MANUFACTURE, A PARTIALLYREDUCED PARTICLE OF OXIDE OF METAL HAVING ATOMIC NUMBERS FROM 27 TO 29, SAID PARTICLE HAVING A SIZE OF ABOUT 0.04 INCH TO ABOUT 0.75 INCH AND CONTAINING A TOTAL METAL CONTENT OF AT LEAST ABOUT 88% TOGETHER WITH ABOUT 0.50% TO ABOUT 4.0% HIGHLY-ACTIVE, FINELY-DIVIDED CARBON UNIFORMLY DISPERSED WITHIN SAID PARTIALLY-REDUCED PARTICLE.

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