US3647418A - HIGH-RECOVERY PRODUCTION OF RICH FeNi ALLOYS IN A CONVERTER - Google Patents

Abstract

A method of producing nickel rich iron alloy by increasing the nickel concentration of the alloy in a converter having molecular-oxygen containing gas blowing comprising adding nickelbearing iron ore and molecular oxygen containing gas to the converter at a rate which maintains the temperature in the converter between 1,550* and 1,650* C., carrying out the blowing and addition of ore in a plurality of steps, and removing, after each step, the slag produced at each step of blowing with addition of ore so that the weight of the slag removed after each step is smaller than four times the weight of the alloy produced after the end of the corresponding step of blowing and addition of ore.

Description

United States Patent Moussoulos Mar. 7, 1972 [54] HIGH RECOVERY PRODUCTION OF RICH FENI ALLOYS IN A CONVERTER 21] Appl. No.: 512,806

[30] I Foreign Application Priority Data Dec. 11, 1964 Greece ..27418 [52] 11.8. CI ..75/82, 75/31, 75/60 [51] Int. Cl. C221) 23/00, C220 3/00 [58] Field ofSearch ..75/82, 31,133, 60

2,750,286 6/1956 Perrin ..75/31 X 3,030,201 4/1962 Queneau et al. ....75/82 X 3,158,464 11/1964 Chynoweth ..75/60 X 3,169,055 2/1965 Joseffson et al ..75/133 X Primary Examiner-Henry W. Tarring, I1 Attorney-Millen, Raptes & White [57] ABSTRACT A method of producing nickel rich iron alloy by increasing the nickel concentration of the alloy in a converter having molecular-oxygen containing gas blowing comprising adding nickel-bearing iron ore and molecular oxygen containing gas to the converter at a rate which maintains the temperature in the converter between 1,550 and l,650 C., carrying out the blowing and addition of ore in a plurality of steps, and removing, after each step, the slag produced at each step of blowing with addition of ore so that the weight of the slag removed after each step is smaller than four times the weight of the alloy produced after the end of the corresponding step of blowing and addition of ore.

2 Claims, No Drawings HIGH-RECOVERY PRODUCTION OF RICH FENI ALLOYS IN A CONVERTER This invention relates to alloy enrichment, especially to a process of producing iron-nickel alloys, and more particularly to a process of producing an alloy having a high nickel content.

For the production of nickel and iron alloys from lateritic or other nickel-bearing iron ores, or even from roasted sulfide ores, there are several commercial pyrometallurigical processes in use. These processes are conducted in a furnace which can be heated by any method such as electrically, or with conventional fuels. The nickel-bearing iron ore is smelted by feeding the ore admixed with a reducing agent directly into the furnace or alternatively by utilizing an ore previously reduced in a rotary kiln, for example. In the latter case, the kiln-treated ore is fed into the smelting furnace with or without the admixture of another quantity of untreated nickelbearing iron ore.

During this smelting step, and depending upon the operating conditions, there is produced a ferronickel alloy in which the nickel concentration can be controlled. Such control is accomplished by increasing or decreasing the percentage of carbon in the mixture fed to the smelting furnace; or by regulating the extent of reduction obtained during a preliminary treatment; or even by changing the ratio of the resulting product from the preliminary reduction treatment to the untreated nickel-bearing iron ore.

In still another process, ferronickel alloys are produced by transforming nickel from its oxidized ores into a nickel alloy. ln processes of this type, nickel oxide ores are first heated to a molten state and then admixed with either molten iron or iron nickel alloy to promote the preferential transfer of nickel from the nickel-bearing iron ore to the alloy thereof. Further, these alloys can be produced by melting the nickel-bearing iron ore and adding, with or without agitation, a metal alloy which is a strong reducing agent, e.g., ferrosilicon. The nickel in the iron ore is thus reduced and the alloy reducing agent aids in the recovery of the nickel from ores containing the same.

The ferronickel alloys produced by the above-described processes are impure and contain unacceptably high amounts of impurities where the alloy is to be directly used for the production of steels, semisteels and other products. The presence of these impurities (P, C, S, Si, etc.) therefore necessitates additional refinement of the nickel alloys. This refining step is usually conducted in a converter, where molecular oxygen, in the form of air, for example, is blown into the ore to oxidize and remove the impurities from the alloy containing the same.

Aside from its refining function, the converter can also function to enrich the nickel content of the ferronickel alloys. In such a process, it is possible to preferentially oxidize the iron contained in the alloys without simultaneously oxidizing more than a relatively insignificant percentage of the nickel. Consequently, the nickel content of the alloy is increased more less in proportion to the extent of iron oxidation.

If, in carrying out these processes of blowing to refine and/or enrich the alloy, there is added a cold solid material thereto, the temperature in the converter, which normally increases due to the exothermic heat of reaction (oxidation of the metallic iron by oxygen), can be held to a reasonable low level. The material which is added can be an inert material such as lime which does not directly affect the concentration of the nickel in the alloy; or conversely, it can be iron or ferronickel scrap which when melted does affect the nickel concentration in the molten alloy. 1n the latter case, however, iron or ferronickel scrap does not increase the recovery of nickel from the primary source; the effect is merely additive.

Another known process utilizes the converter as the sole piece of equipment for also smelting nickel-bearing iron ores to ultimately obtain a ferronickel alloy. According to this method, to the converter is added nickel-bearing iron ore containing nickel and iron oxides. The heat of reaction between oxygen and metallic iron (which is in the initial charge) melts the ore. From the resultant molten ore, a portion of nickel reduced to the metallic state by iron or ferrous compounds migrates into the underlying alloy. Under certain conditions, the utilization of nickel-bearing iron ore in this manner results in an economic recovery of nickel. Under such circumstances, the nickel recovered from the ore may counterbalance the nickel losses in the slag, which losses are brought about during the enrichment of the alloy.

Under equilibrium conditions in the converter, the nickel losses depend in part on the concentration of nickel in the underling alloy. This is particularly evident when it is desired to produce an alloy having a high nickel concentration, because the nickel concentration of the alloy determines the nickel content of the overlying molten slag. This slag results both from the fusion of added lateritic nickel-bearing iron ore and from the iron oxide formed by the oxidation of metallic iron in the alloy.

It is known that, in general, the richer the nickel in the underlying molten alloy, the richer in nickel will be the overlying molten slag. The nickel losses occurring in the slag during the enrichment of the alloy by oxygen blowing usually reach such proportions that it is uneconomical to enrich the alloy with nickel above a certain concentration. This, of course, militates against the use of this process for the production of high nickel alloys. Consequently, the enrichment of ferronickel alloys by oxygen-blowing has been limited to lower nickel concentrations heretofore.

It is therefore a principal object of this invention to provide an improved process for increasing the concentration of nickel in a ferronickel alloy.

It is another object of the invention to improve the process in the blowing of oxygen into a ferronickel alloy in the presence of nickel-containing ores in order to obtain a high nickel alloy more economically.

It is still another object of this invention to provide a process of economically forming a concentrated alloy of a relatively nonoxidizable metal from an alloy containing the latter and a relatively oxidizable metal.

These and other objects and advantages of the invention will become apparent by reference to the description and claims appended hereto.

To achieve the broadest object of this invention, slag is removed during a process instead of waiting until the desired concentration of relatively nonoxidizable (nonslag-forming) metal is attained in the molten alloy. This is preferably accomplished by conducting a plurality of the similar steps wherein slag is removed at the termination of each step. In this way, there will be less slag in equilibrium with the enriched alloy; and thus less of the desired metal is lost in the slag.

With respect to the preferred specific embodiment of this invention, there is provided a process of increasing the nickel concentration of a nickel-iron alloy comprising: blowing a quantity of molecular oxygen-containing gas into a molten nickel-iron alloy while simultaneously adding a nickel-bearing iron ore to the molten alloy, adjusting the addition rate of oxygen-containing gas and ore into the converter to maintain the temperature therein preferably between 1,550" and 1,650" C. and removing the formed slag from the molten alloy during the process at a rate so that the final quantity of slag preferably weighs less than about four times the final quantity of enriched alloy. in this way an alloy having a high nickel content can be obtained from a nickel-bearing iron ore with only a minimum loss of nickel.

Describing the overall process in greater detail, the nickelbearing iron ore to be treated is charged to the converter after crushing, e.g., to 30 mm. If desired, the ore can be pretreated by heating and/or drying. The converter being charged contains a quantity of molten ferronickel alloy remaining from a former treatment. (When operation of the converter is first begun, a predetermined quantity of the alloy is melted in a furnace separately and supplied in molten form to the converter.) in the overall refining process, it is preferred to employ a weight ratio of from 1 to 10, more preferably 1.5 to 4.0 times as much nickel-bearing iron ore as original molten alloy.

As the oxidizing agent to remove the elemental iron from the alloy, oxygen, air, a mixture thereof, or any other molecular oxygen-containing gas is blown through the molten material in the converter to which has been added a nickel-bearing iron ore. The converter process is conducted in such a way as to produce from each portion of ore charged, a slag containing a small quantity of nickel. For this purpose, the oxygen-blowing and the addition of nickel-bearing iron ore are carried out intermittently and incrementally, and the slag formed during each blow is removed from the converter. Since the increase in nickel content of the underlying molten alloy during each blow is dependent upon blowing time and the quantity of the nickel-bearing iron ore charged, the duration of the blowing is controlled to minimize the formation of excessive amounts of overlying slag.

As stated previously, the ratio of the weight of the overlying molten slag formed during each blow to the weight of fer ronickel alloy produced is preferably smaller than 4 to l, and more preferably lower than 2 to 1. Further, the weight of the nickel-bearing iron ore charged is adjusted to maintain the converter temperature between 1,550 and l,650 C. during the blow. Thus, the preferred operation according to the present process is'based on controlling both the fusion temperature of the ore and the quantity of resulting slag-containing iron oxide formed by the oxidation of metallic iron.

In addition to controlling the ore charge, the oxygen blow is also regulated so as to oxidize the iron at a rate such that the evolved exothermic heat of reaction during oxidation is suffrcient to fuse the charged ore at a melt temperature of 1,550 to 1,650 C. and also to produce a quantity of slag less than four times the weight of produced ferronickel alloy.

After each blow is terminated, the molten alloy in the converter can be allowed to stand for some minutes until continuing reactions therein have ceased. Thereafter, the slag is then more safely withdrawn from the converter.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the specification and claims in any way whatsoever. Where the expression m. is employed, the volume is based on normal conditions of temperature and pressure of C. and 760 mm. Hg, respectively.

EXAMPLE 1 a. A nickel-rich alloy is produced according to my process from a nickel-bearing lateritic iron ore and a nickel-poor ferronickel alloy as follows: 6 tons of molten ferronickel containing 18 percent nickel are charged into a converter provided with a conventional lance for blowing pure oxygen.

In the first step of the process, oxygen is admitted through the lance and 1,700 kg. of nickel-bearing iron ore with 1.6 percent nickel (25.8 kg), 36 percent iron, and percent moisture are gradually added. The oxygen blow is continued until 290 m. of oxygen are discharged. The blow is then interrupted, the molten mass is allowed to stand for 5-7 minutes. The slag, amounting to 3,598 kg., is then removed from the alloy. There is then recovered an alloy weighting 4,359.7 kg. and containing 25 percent nickel. The rejected slag containing 0.45 percent nickel, i.e., 16.2 kg. nickel, is discarded. In this case, the ratio of the weight of the slag produced to the weight of the final alloy was 0.825 to 1, and the nickel lost in the slag amounted to 1.47 percent of the total nickel charged in the form of both alloy and ore.

b. After removing the slag, the alloy produced in step (a) above is again blown with 240 m. of oxygen while simultaneously adding 1,400 kg. of nickel-bearing iron ore containing 1.6 percent, or 21.3 kg., of nickel, 36 percent iron, and 5 percent moisture. The process is then interrupted, the reaction mass allowed to stand for 5-7 minutes, and the slag formed, about 2,952 kg., is separated therefrom. The alloy remaining after this last blow weighed 3,012 kg. and contained 36 percent nickel. The slag formed contained 0.9 percent nickel and hence there was discarded, in the slag, 26.7 kg. of nickel. in step (b), the ratio of the weight of the slag formed to the weight of the final alloy was 0.98 to l, and the nickel loss was 2.4 percent of the total nickel fed in both the alloy and the ore.

c. After removing the slag from the alloy produced from the preceding step (b), the alloy is again blown with 255 m. of oxygen while adding 1,100 kg. of nickel-bearing iron ore containing 1.6 percent, or 16.7 kg., of nickel, 36 percent iron, and 5 percent moisture. The treatment is interrupted, and after 5-7 minutes of standing, the slag formed, about 2,632 kg., is poured off. The resulting alloy weighed 1,617.5 kg and contained 64 percent nickel. The discarded slat contained 2.5 percent nickel, and thus 65.8 kg. of nickel were rejected therewith. In this step, the ratio of the weight of the slag formed to the weight of the final alloy was 1.63 to l, and the nickel loss in the slag was 5.98 percent of the total nickel charged in both the initial alloy and the ore.

From the total 6,000 kg. of a ferronickel alloy containing 18 percent nickel in the preceding steps (a), (b), and (c), there were produced 1,617.5 kg. of a ferronickel alloy containing 64 percent nickel. At the same time, there were discarded in total 9,182 kg. of slag having an average nickel content of 1.18 percent, and the total loss of the nickel from both the alloy and ore was 9.5 percent.

A material balance on the basis of the nickel in the initially charged ferronickel alloy shows that out of 1,080 kg. of nickel in the initial alloy, only 44.8 kg. of nickel was discarded and lost in the slag, i.e., 4.15 percent.

lf, instead of recovering nickel by the process of this invention, the conventional process is employed whereby blowing is continued until a final nickel concentration of 64 percent in the alloy is obtained, the results, in terms of nickel losses. are altogether different.

In Example 2, a ferronickel alloy with 64 percent nickel is produced from an alloy containing 18 percent nickel. This conventional process is carried out in a one-step process and thereby characterizes the difference in the results obtained:

EXAMPLE 2 Six tons of a ferronickel alloy are charged into the same converter used in the preceding Example 1, and 820 m." of oxygen are blown therein while adding 4,200 kg. of nickel-bearing iron ore containing 1.6 percent nickel, 36 percent iron, and 5 percent moisture. After 5-7 minutes of standing, the slag formed, about 9,584 kg., is poured off. The slag, as in Example 1 (c), contains 2.5 percent nickel since the treatment was continued until there was produced a ferronickel alloy containing 64 percent nickel.

Out of the 63.8 kg. of nickel charged in the ore, the alloy produced from the above process had a weight of 1,412.8 kg. and 239.6 kg. of nickel were rejected in the slag.

In the conventional process illustrated by this example, the ratio of the weight of slag formed to the weight of the final alloy was 6.78 to 1 and the nickel lost in the slag was 21 percent of the nickel totally charged in both the alloy and ore.

When the nickel balance uses as a basis the initially charged ferronickel alloy, it is seen that 175.8 kg. of nickel in the initially charged ferronickel alloy was lost, i.e., 16.3 percent.

By comparing the above two examples, it is seen that in the process of the present invention, the amount of nickel lost in the slag is substantially reduced. Thus, in above Example 1. the nickel lost is 9.5 percent, as compared to a 21 percent loss in the conventional process of Example 2.

It is also desirable to add before or during the oxygen blow, several solid'reducing agents, e.g., carbon, which do not react instantaneously with the molten slag but instead are conserved during and after the blow. By the use of these reducing agents, such as carbon, the nickel content of the molten slag is lowered, since the carbon mixed with the slag during the blow continuously reacts therewith, even before the blow is begun. Thus, there is an in situ" reduction of nickel in the slag, and the resulting reduced nickel then migrates from the slag to the allow therebelow. When the carbon is charged before the nickel bearing iron ore, the admixture thereof during the subsequent smelting favors the reduction of the nickel in the iron ore and thus an increased recovery of nickel therefrom is attained.

Nickel alloy production according to this invention is thus even further improved by the presence of a solid reducing agent in the converter during the blowing or before it. By this technique, the oxidation of nickel by the oxygen blown is inhibited, and the reduction of nickel oxide found in the nickelbearing iron ore is facilitated. Therefore, it is within the purview of this invention to reduce the nickel losses in the slag by the in situ reductive action of the solid reducing agent, e.g., carbon, before or during blowing. As a result of the reverse action of the reducing agent to the oxidative action of the oxygen blown, on the one hand there is produced a rich, e.g., up to 90 percent, ferronickel alloy with simultaneous smelting of nickel-bearing iron ore, and on the other hand, the nickel losses in the slag are reduced to levels much lower than those which are obtained in the processes described hereinbefore.

The ratio of solid reducing agent such as carbon to the ore added is from 1 to 5 percent and preferably 2 percent. Besides carbon other solid reducing agents can be used, such as silicium alloys finely crushed and the like.

To illustrate the advantages of using a solid reducing agent, an example of such a treatment is set forth below:

EXAMPLE 3 a. Into a preheated converter having a l0-ton capacity, there are introduced 20 kg. of coke fines and then 6 tons of a molten ferronickel alloy containing 34 percent nickel. The lance is positioned in the molten alloy, and oxygen is blown therethrough for 1 minute. Thereafter, and while the blow is continued, 700 kg. of nickel-bearing iron ore, containing 1.41 percent nickel, 38.05 percent iron, and 7.63 percent moisture are added. In total, 149 m. of oxygen are blown. After this treatment, theslag, which now weighs about 1,673 kg. and contains 0.55 percent nickel, is poured off. It is seen then that whereas 9.2 kg. of nickel are lost through the slag, the same amount of nickel was introduced into the converter via the nickel-bearing iron ore.

The above process produced 5,151.5 kg. of ferronickel alloy containing 39.6 percent nickel. The loss of nickel, calculated on the basis of the nickel totally fed in the alloy and nickelbearing ore was 0.45 percent. The ratio of the weight of the slag formed to the weight of the alloy produced was 0.33 to 1.

b. After pouring off the slag in the preceding treatment 3 (a), 10 kg. of coke fines are introduced into the alloy left in the converter, and the resulting admixture is subjected to further treatment by blowing 157 m. of oxygen therethrough and adding 700 kg. of nickel-bearing iron ore as in Example 3 (a). The process is then discontinued and the slag formed, about 1,723 kg., is poured off. The alloy left in the converter weighed 4,265.2 kg. and contained 47.8 percent nickel; the slag rejected contained 0.6 percent nickel. Therefore, 10.4 kg. of nickel were discarded as compared to 9.2 kg. of nickel fed in the nickel-bearing iron ore.

The ratio of the weight of the slag formed to the weight of the alloy produced was 0.4 to l, and the nickel loss, through the slag, calculated on the basis of the total nickel fed in the alloy and the nickel-bearing iron ore was 0.51 percent.

C. After removing the slag from the alloy in step (b), 10 kg. of coke fines was added to the contents of the converter. The resulting admixture was then blown with 121 m. of oxygen while adding 600 kg. of nickel-bearing iron ore, having a composition similar to that used in Example 3 (a). After the blow period, the slag formed, about 1,391 kg., was removed from the alloy.

There was produced in this process 3,571.6 kg. of ferronickel alloy, containing 57 percent of nickel. The slag contained 0.78 percent nickel. Hence, in the slag there was lost 10.9 kg. of nickel as compared to the 7.9 kg. of nickel introduced via the nickel-bearing iron ore.

The ratio of the weight of the slag formed to the weight of the final alloy was 0.39 to l, and the nickel lost in the slag was 0.53 percent of the nickel fed in the ferronickel alloy and ore.

d. After removing the slag from the alloy in step (c), 10 kg. of coke fines were charged to the converter. Thereafter, 127 m. of oxygen was blown through the resulting admixture with simultaneous addition of 600 kg. of nickel-bearing iron ore having a composition similar to the ore in Example 3 (a). After the blow, the slag formed, about 1,429 kg., is poured off.

This step resulted in the production of 2,852.4 kg. of ferronickel alloy containing 70.7 percent nickel. The slag contained 1.9 percent nickel. Thus, in the slag, 27.1 kg. of nickel were lost compared to the 7.9 kg. of nickel fed in the nickelbearing iron ore.

The ratio of the weight of slag formed to the weight of the final alloy was 0.5 to 1, and the nickel loss in the slag was 1.33 percent of the nickel totally fed in both the alloy and ore.

e. After removing the slag from the alloy of step (d), 10 kg. of coke fines are charged into the converter followed by 127 m. of oxygen blow and the addition of 400 kg. of nickel-bearing iron ore having a composition similar to that of the ore used in Example 3 (a). The slag, about 1,221 kg. formed during the blow, is poured off. The above procedure results in the production of 2,176 kg. of ferronickel alloy containing percent nickel. The slag formed contained 5.18 percent nickel. Compared to the 5.2 kg. of nickel fed in the nickel-bearing iron ore, 63.3 kg. of nickel are lost in the discarded slag. ln this case, the ratio of the weight of the slag formed to the weight of the final alloy was 0.56 to 1, and the nickel lost in the slag was 3.13 percent of nickel fed in both the alloy and ore.

In summary, the overall process of Example 3, comprisin steps (a) to (e), utilizing 6,000 kg. of a ferronickel alloy containing 34 percent nickel and 3,000 kg. of nickel-bearing iron ore, resulted in the production of 2,176 kg. of a ferronickel alloy containing 90 percent nickel. With respect to the slag, there were rejected a total of 7,436 kg. having an average nickel content of 1.62 percent. The total loss of nickel on the basis of that initially present in the alloy together with that introduced in the nickel-bearing iron ore was 5.81 percent.

As another aspect of the invention, the slag formed during the production of an enriched ferronickel containing, e.g., 50 percent or more of nickel is recirculated to provide an even further reduction in nickel losses. It is preferred to recycle this nickel-rich slag to the converter during the first step of the process in which the nickel content of the slag is low. The recycled slag can be granulated or crushed, and it can be recycled while hot or molten to the converter. 1n the latter case, the thermal content of the slag aids in maintaining the thermal balance in the converter.

In the event the slag is added in cold and solid form to the converter, the quantity of ore to be added is reduced, since the slag takes the place of the ore. When the slag added is in molten or hot condition, the quantity of the ore to be added to only slightly reduced.

The above process is more fully described in Example 4 hereinafter set forth. In this example, the slag formed is recycled during the production of ferronickel alloy containing 70.7 to 90 percent nickel.

EXAMPLE 4 a. To recycle the molten slag after the end of the blowing operation in Example 3 (e), the molten slag is removed in a ladle typically used in metallurgy. Thereafter, the alloy produced is removed from the converter in another ladle. The hot and molten slag removed is then recharged into the converter.

Further, there is added to the converter 20 kg. of coke fines, followed by a charge of 6 tons of molten ferronickel alloy containing 34 nickel.

The process is initiated by blowing oxygen for 1 minute through the charge. Thereafter, and while the oxygen blow continues, 700 kg. of nickel-bearing iron ore, containing 1.41 percent nickel, 38.05 percent iron, and 7.63 percent moisture, are added. Totally, 110 m. of oxygen are blown. After this first step is completed, the slag weighting about 2,692 kg. and containing 0.55percent nickel, is poured off. Consequently, 14.8 kg. of nickel are lost in the slag, whereas 9.2 kg. of nickel were fed in the nickel-bearing iron ore and 63.3 kg. of nickel were introduced in the rich slag (this slag weighted 1,221 kg.

and contained 5.18 percent nickel). Thus, there is obtained a credit of about the entire nickel content fed in the rich slag.

From the first step of the process, 5,297.2 kg. of ferronickel alloy containing 39.6 percent nickel were produced. The nickel loss out of the nickel totally fed in the alloy, ore, and slag, was 0.7 percent.

The ratio of the weight of the slag formed to the weight of the alloy produced was 0.51 to 1.

b. After removing the slag formed in step (a), kg. of coke fines are added to the converter with the alloy produced. 162 m. of oxygen are then blown through the resulting admixture, while adding 700 kg. of nickel-bearing iron ore having a composition similar to the ore used in Example 4 (a). After the oxygen blow, the slag formed, about 1,755 kg., is rejected.

The alloy in the converter after this step weighed 4,385.8 kg. and contained 47.8 percent nickel. The rejected slag contained 0.6 percent nickel representing 10.5 kg. as compared to the 9.2 kg. of nickel fed in the nickel-bearing iron ore.

The ratio of the weight of slag formed to the weight of the alloy produced was 0.4 to l, and the nickel lost in the slag was 0.5 percent of the nickel, based on both the alloy and ore.

c. 10 kg. of coke fines were charged to the converter containing the alloy produced in step (b) above. The resulting admixture was then blown with 125 ms" of oxygen while adding 600 kg. of nickel-bearing iron ore, similar to the ore used in Example 4 (a). The produced slag removed after the blow weighted approximately 1,415 kg.

After this treatment, 3,672.5 kg. of alloy containing 57 percent nickel were produced. The slag contained 0.78 percent nickel; consequently, 1 1 kg. of nickel were lost in the slag, as compared to 7.9 kg. of nickel fed in the nickel-bearing iron ore.

The ratio of the weight of the slag formed to the weight of the final alloy was 0.39 to l, and the nickel lost in the slag was 0.53 percent of the total nickel fed in both the alloy and ore.

d. 10 kg. of coke fines were charged to the converter containing the alloy, produced in Example 4 (c) above. The resulting admixture is then blown with 131 m. of oxygen, while simultaneously adding 600 kg. of nickel-bearing iron ore, similar to that used in the above Example 4 (a). The slag weighting 1,446 kg., is then poured off.

The process step produced 2,933.1 kg. of ferronickel alloy containing 70.7 percent nickel. The slag contained 1.9 percent nickel; consequently, 27.5 kg. of nickel were lost in the slag, as compared to 7.9 kg. of nickel fed in the nickel-bearing iron ore. The ratio of the weight of the slag formed to the weight of the final alloy was 0.49 to 1, and the nickel lost in the slag was 1.33 percent of nickel fed in both the alloy and ore.

(e). After removing from the alloy the slag produced in the preceding step, 10 kg. of the coke fines are charged to the converter, and the resulting admixture is then blown with 131 m5 of oxygen, while adding 370 kg. of nickel-bearing iron ore, similar to that used in Example 4 (a). The produced slag weight about 1,221 kg., is poured off. 2,238.9 kg. of ferronickel alloy containing percent nickel, were produced. The slag formed contained 5.18 percent nickel, and consequently, 63.3 kg. of nickel were lost, as compared to 4.8 kg. of nickel fed in the nickel-bearing iron ore.

The ratio of the weight of the slag formed to the weight of the final alloy was 0.55 to l, and the nickel lost in the slag was 3.05 percent of the nickel fed in both the alloy and ore.

In summary, it is seen that, m the preceding five steps of Example 4, from 6,000 kg. of a ferronickel alloy containing 34 percent nickel, 2,970 kg. of nickel-bearing iron ore, and by recirculation of 1,221 kg. of molten slag produced in the preceding steps and containing 5.18 percent nickel, there were produced 2,238.9 kg. of ferronickel alloy containing 90 percent nickel. In total, 7,308 kg. of slag having an average nickel content of 0.87 percent, are rejected, while 1,221 kg. of the slag produced in Example 4 (d) are recycled. Consequently, the total nickel loss from the nickel fed via the alloy, the nickel-bearing iron ore, and recycled slag, was 2.98 percent against 5.81 total nickel loss in the preceding Example 3 without recycled slag.

The process described by way of Examples 1 to 4 is likewise applicable to the treatment of alloys and ores containing cobalt and nickel, for the reason that lateritic ores utilized herein contain cobalt as well as nickel. Also, the new and novel process herein can be used to refine similar alloys and ores of copper.

From the foregoing description, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof can make various changes and modifications of the invention to adapt it to various usages and conditions. Consequently, such changes and modifications are properly, equitably, and intended to be, within the full range of equivalence of the following claims.

What is claimed is:

1. A process of producing nickel-rich iron alloys, by increasing their nickel concentration, comprising: blowing a moleculat-oxygen containing gas into a molten nickel-iron alloy in a converter while adding a nickel-bearing iron ore to the molten alloy, maintaining the temperature in the converter between l,550 and 1,650 C. by the rate of said addition and blowing, carrying out said blowing and addition of ore in a plurality of steps wherein the slag produced at each step of blowing with addition of ore is removed after each step and the weight of slag removed after each step is smaller than four times the weight of the alloy produced after the end of the corresponding step of blowing and addition of ore, separating from the alloy the slag formed by contact with alloys containing at least 50 percent nickel and recycling said last-mentioned slag to a preceding step in the process in which an alloy containing less than 50 percent nickel is being produced, thereby recovering a portion of nickel in the recycled slag.

2. The process of claim 1, further characterized in that particulate carbon is added to the reactants in the converter before the blowing of the molecular oxygen-containing gas and the addition of the nickel-bearing iron ore.

Claims (1)

1. 2. The process of claim 1, further characterized in that particulate carbon is added to the reactants in the converter before the blowing of the molecular oxygen-containing gas and the addition of the nickel-bearing iron ore.