CA1048278A - Metal carbonate recycle to reduction circuit in the cuprion process - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process in which copper, nichel, cobalt, and molyb-denum are recovered by direct leaching of comminuted raw manganese nodules after the nodules are reduced in a reduction circuit with an aqueous ammoniacal leach solution containing cuprous ions. An improvement is disclosed which results from recycling a portion of the metal values recovered back to the reduction circuit as a solid basic metal carbonate. The metal carbonate recycle enables the size of the reactors in the reduction circuit to be reduced. The recycle also increases the efficiency of the process by facilitating the solubilization of copper. Another aspect of the invention resides in the advantages of maintaining solubilized copper in amounts between 10 grams per liter and the solubility limit in the reduction circuit.

Description

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Tllere is known a process in which copper~ nickel, cobalt and molybdenum are recovered from raw manganese nodules with an aqueous ammoniacal leach solution containing cuprous ions. In that process ~which has come to be called the "cuprion"
process) ground manganese nodules are contacted with an ammoniacal leach solution containing cuprous ions in a reaction vessel to reduce the manganese oxides in the nodules to enable metal values such as copper, nickel, cobalt and molybdenum to be solubilized. The nodule residue is washed with an ammoniacal ammonium carbonate solution to remove these entrained metal values from the residue. The reduction liquor i5 recycled to the reaction vessel in which the manganese nodules are added.
To maintain a sufficient amount of cuprous ions, a reducing gas, such as carbon monoxide, is passed through the reaction vessels. The process described requires, however, large reactors, or a large number of smaller reactors in order to process a nominal output of metal values.
In accordance with the present invention~ it has been discovered that the volume of reactors required in the reduction circuit is influenced by the copper content of the reduction liquor. The size of the reactors required can be reduced if the amount of solubilized copper in the cuprous ion reduction liquor is increased, Recycling a mixed metal carbonate pre-cipitate to the reduction circui.t is a practical way to increase the copper content of the cuprous ion reduction liquor ln the reduction circuit.
Thus, according to one aspect of the invention there is provided in a process in which metal values selected from ,i , the group consisting of copper, nic~el~ cobalt and molybdenum are recovered from a manganese containing ore by introducing the ore into a reaction ~essel containing cuprous ions in an ~t 2 -~ ~ .' ' ` ~

2~
aqueol~s a~moni~cal ~monlu~ carbonate leach ~lution to allow the cuprous ions to reduce the manganese oxides in the ore to enable tlle ~tal values to ~e solubilized in the aqueous ammoniacal ammonium carbonate leach solution and in which cuprouS ions are contlnuously regen&rated in the leach solution by a reducing gas wherein the improvement comprises leaching the metal values from said manganese containing ore with said leach solution, recovering a portlon of the metal values solubilized in the leach solution as a mixed metal carbonate precipitate and recycling the mixed metal carbonate back to said reaction vessel to increase the solubilized copper content of the leach solution in the reaction vessel.
According to another aspect of the invention there is provided in a process in which metal values sele~ted from the group consisting of copper, nickel, cobalt and molybdenum are recovered from a manganese containing ore by introducing the ore into a reduction reaction vessel in which the ore is reduced, said reduction reactlon vessel containing an aqueous ;
ammoniacal ammonium carbonate leach solution of cuprous ions to allow the cuprous ions to reduce the manganese oxides in the ore to enable the metal values to be solubilized in the - aqueous ammoniacal ammonium carbonate leach solution and in ; which cuprous ions are continuously regenerated in the leach solution by a reducing gas wherein the improvement comprises leaching metal values from said manganese containing ore with sald leach solution, recovering a portion of the metal values solubilized in the leach solution, after the solubllized metal values leaYe the reduction reaction vessel, as a mixed metal ~ ~ -carbonate precipitate and recycling a sufficient amount of the mixed metal carbonate back to the reduction reaction vessel so , as to maintain the soluble copper content of the reduction ' .

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re.lction v~ssel tt a leyeL of at leas~ 10 g~ttms per litert If the solubilized copper content of the reduction liquor in the reduction circui~ is maintained at a level of 10 grams per liter, the size of the reactor required in the known process briefly described above can be reduced by a factor of two. Of course a higher copper content in the reduction liquor makes further reduction in the size of the reduction reactors possible.
Accordingly, it is an advantage of the present inven-tion, at least in the preferred forms, that it can provide animproved process for solubilizing metal values in manganese nodules.
A further advantage of the present invention, at least in preferred forms, is that it can provide a multistage process for the continuous reduction of manganese nodules by the cuprion process in which the amount of cuprous ions in each stage of the process is relatively high.
A further advantage of the present invention, at least in preferred forms, is that it can provide a multistage process for the continuous extraction of metal values from manganese nodules by the cuprion process in which the solubilized ~ ~`
copper content of the reduction liquor in the reduction circuit is about 10 g/l or greater.
A further advantage of the present invention, at least in preferred forms, is that it can provide a practical method for increasing the copper content of the reduction liquor in the cuprion process.
Another advantage of the present invention, at least in preferred forms, is that it can provide an improved cuprion 30 process which includes the steps of recycling a ~asic metal ~ ~-carbonate feed to the reduction circuit.

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,. 1 is a flow shee~ lllustratin~ the process of the present invent iOIl, ~`ig. 2 is a scheMatic dia~ram Or the knowll process briefly ;
described above, Fig . 3 is a schemati c d:ia~;ram similar to Fig . 2 but sh~wing .
the process of ~he present inventionO 1~
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At the outset, the process o~ the present invention is described in its broadest o~erall aspects with a more detailed description ~ollowing. The present invention is directed to the recovery o~ metal values from manganese deep sea nodules. ~or the purpose of this patent specifica-tion and claims, complex ores which are found on the deep sea floor of oceans and lakes containing manyanese, iron, copper, nickel, molybdenum, cobalt and other metal values are variously referred to as deep sea manganese nodules, manganese nodules or nodules.
Ocean floor deposits are found as nodules, loose-lying at the surface o~ the so~t sea floor sediment, as grains in the sea floor sediments, as crusts on ocean floor hard rock outcrops, as replacement fillings in calcareous debris and animal remains, and in other less important forms. Samples of thls,-ore material can readily be recovered on the ocean floor hy drag dredging, a method used by oceanographers for many years, or by deep sea hydraulic dredging, a method that could be used in commercial operations to mine these deposits. Mechanical deep sea nodule harvesters are described in U.S. Patent Nos.

3,480,326 and 3,504,943.
The character and chemical content of the deep sea nodules may vary widely depending upon the region from which the nodules are obtained. The Mineral Resources of the Sea, John L. Mero, Elsevier Oceanography Series, Elsevier Publishing Company, 1965, discusses on pages 127-241 various aspects of man~anese nodules. For a detailed chemical analysis of nodules from the Pacific Ocean see pages 44g and 450 in the Encyclopedia of Oceanography, edited b~ R.W. Fairbridge, Reinhold Publishing ,, : , :: . : , .

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corp., N.Y. lY66, and U.S~ Patent No. 3,16~,85~; For the purpose of this invention the complex ores will be considered as containing the following approximate metal content range on a dry basis:
METAL CONTENT ANALYSIS RANGE
Copper 0.8 - 1.8 Nickel 1.0 ~ 2.0 Cobalt 0.1 - 0.5~i Molybdenum 0.03 - 0.1%
Manganese 10.0 - 40.0%
Iron 4.0 - 25.0~
The remainder of the ore consists of oxygen as oxides, clay minerals with lesser amounts of quartz, apatite, biotite, sodium and potassium feldspars and water of hydration. Of the many ingredients making up the manganese nodules, copper and nickel are emphasized ~;
because, from an economic standpoint, they are the most significant metals in most of the ocean floor ores.
In the cuprion process, raw manganese deep sea noaulesi are reduced with cuprous ions (Cu~ in an aqueous ammoniacal ammonium carbonate solution. The curprous .
ions reduce the manqanesie in the nodules which enables , metal values such as copper, nickel, cobalt and molybdenum to be dissolved while leaving undesirable metals such as j ~
iron in the solid residue. In the reduction process, ~ -, the manganese dioxide in the deep sea nodules is reduced by cuprous ion to manganese carbonate according to the reaction M~O2 + 2 Cu(NH3)2 4 NH3 + CO2 2 (1) MnCO3 + 2 Cu (NH3)~ + 2 OH

.
, ., 1~4B;~78 Cupric ions indicated in equation (1) are reduced back to the cuprous state with carbon monoxide accordiny to the reaction 2 Cu (NH3)4 + CO ~ 2 OH ~ --t (2 2 Cu ~NH3)2 + 4 NH3 ~ CO2 + H20 Cuprous ion is consumed in reaction (1) and is regenerated by reaction (2). The net overall reaction for the reduction process is the sum of equation (.11 and 12), or equation ~3J: ~
2 ~~~~~ (3) ;
In order to provide an efficient reactor system : ~or the cuprion process, it is necessary to balance the rate of reaction ~1) and l:2~
In order to maintain enough cuprous ions at all : stages of the cuprion process by regeneration from cupric ions, the cuprous ion concèntration must be maintained at a fairly high level because the amount of catalyst ` ~:
available for reducing cupric ions to cuprous ions is :
: controlled by the actual amount of cuprous ions. In fact, if the level of cuprous ions is below about 2 grams per liter (at atmospheric pressure and temperature below approxima~ely ~0C) efective regenerat.ion of cuprous ions is not commercially feasible. `: ~
One method of maintaining the cuprous ion ~`
concentrations fairly high at all levels of the process is to inject the nodule feed stock at multiple points. ~
This multipoint injection facilitates the regeneration .:~ .
: of cuprous ions by rèducing the possibility that the - nodule will exhaust the supply of cuprous ions in any one reactor by reac~ing with them.

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In accordance with the present invention, it has been discovered that the efficiency of the cuprion is increased if the soluble copper content of the reduction liquor in the reduction circuit is maintained at a level of about 10 g/l or greater. In connection with the term "soluble copper", as used throughout this specification and claims ~soluble copper", is intended to describe copper in an ionic state, that is in either its cuprous or cupric form.
In accordance with the present invention, the amount of soluble copper in the reduction liquor in the reduction circuit is increased by diverting a portion of the pregnant liquor that could otherwise be sent to - L~X extraction, stripping the liquor to obtain a metal carbonate precipitate containing basic copper carbonate as well as nickel, cobalt and molybdenum carbonates, and recyclying the precipitate to the reduction circuit in sufficient quantity to maintain the desired level of soluble copper in that circuit. Without this metal carbonate recycle the soluble copper level in the reduction liquor will be only 4-6 g/l. With a basic metal carbonate recycle, the soluble copper level in the reduc~ion liquor can be increased to any desirable level up to the solubility limit. At this point it should be noted that the recycle solid is not pure oxide but a mixed oxide carbonate-hydroxide preclpitate of varying composltion.
It goes into solution as metal amine carbonate.
.
The process of the present in~ention is further illustrated by the following example in conjunction with Fig. l of the drawing. At the outset, ho~ever, it is emphasized that the following description relates to a ~L~4~
procedure that has been performed in a pilot plan-t. ay extrapolating the results obtained from the pilot plant, however, one skilled in this art can design a commercial plant for processing large quantities of nodules.
The pilot plant was designed for one halE tons per day nodule throughput, based on a 3 1j2 percent solid slurry and with up to a three hour hold-up in the reduction section.
The process performed in the pilot plant can be broken down into the following sections:
1. Ore Preparation 2. Reduction-Leach 3. Oxidation and Wash-Leach 4. BMC Recycle S. LIX Separation of the Metals 6. Electrowinning ORE PREPARATION
The nodules utilized in the pilot plant process are received in 55 gallon drums in the condition that they are in after being mined from the deep sea ocean bottom. To facllitate processing in the pllot plant, the nodules are air dried. After they are dried, they are then blended, using the "cone and quarter" technique before going into the primary crushin~ ci;rcuit. The primary crushing circuit consists of a Jacobson "~ull .
Nelson" crusher to reduce the raw nodules to minus one inch. Thereafter! the nodules are passed through a Stedman double row cage mill to reduce the ore further to minus 6 mesh. The nodules are then conveyed away on a belt feeder to drums for storage or further processing.

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The second grinding circuit is the final stage of ore preparation before the nodules enter the reduction stage. This circuit consis~s of a hopper, filled from the drums of cage milled ore, located on top of a hydraulic weigh feeder. The weigh eeder is used ~o meter nodules at a given rate into an open circuit rod mill for final grinding. The rod mill reduce~ the nodules from a particle size of minus six mesh to a particle size of approximately minus sixty mesh. As the nodules enter the rod mill, they are wetted with a synthetic sea water which brings the nodules up to approximately 40% moisture.
This moisture content corresponds to -the moisture which would be present in nodules as they are brought up from the sea bottom. At this point, it should be noted that in a commercial operation the nodules would be processed directly after being mined from the ocean bottom, thus, the foregoing steps of drying and wetting the nodules would be unnecessary. However, for purposes of a pilot plant operation it was found convenient to air dry the nodules and later wet the nodules so that they had a 2~ moisture content equivalent to that of reshly mined nodules.
It has been found advantageous to add recycle reduction llquor to the rod mill. In a commercial process recycle liquor can be added to the grinding mill in order to provide a liquor to facilitate grindlng and reduce the dust problem without introducing more water into the circuit which would cause undesirable dilution. Of course, the recycle reduction liquor is advantageous in maintaining the proper copper concentration in the reduction circult as well to provide liquor which is ~1 0;

;278 useful in the grinding process itself. Datails oE the recycle liquor circuit are amplified below.
REDUCTION-LEACH
The reduction-leach portion of the pilot plant is the section where the nodules are chemically reacted to make the metals of interest soluble in a strong ammoniacal ammonium carbonate solution. This is accomplished by reducing and converting the MnO2 in the nodules;to MnC03 .
After leaving the rod mill, the nodules are passed through a conduit into a vibrator (not shown).
The purpose of the vibrator is to remove àhy tramp material. The vibrator utilized is a Sweco vibrating s~reen. The material that enters and leaves the vibrator is actually a liquid slurry. Connected to the vlbrator ~ .
is a surge tank (not shown). The purpose of the surge tank is to serve as a storage unit so that the process plant will not have to be shut down in the event that there is a malfunction in some piece of ore preparation machinery. After leaving the surge tank, a feed pump pumps the slurry to the reduction circuit.
The reduction circuit includes six reactors connected in serles. These reactors are sixty gallon capacity reactors whlch are used to a 42 gallon capacity in the actual processing. Each reactor is formed of 316 stainless steel and are outfitted with agitators, pressuxe gages, level alarms, and ~as sparging equlpment. ~he reduction and leaching within these reactors is performed -~
at a temperature between the range of 40-70C, a pH -~
between the range o 10.0-10.8, and at a pressure of approximately one atmosphere. ;

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Gas sparging is directed underneath the agitator from the bottom of the reactor where a reduction gas containing 95 percent carbon monoxide and 5 percent hydrogen is introduced. This mixture is used because it is similar to a reduction gas mixture ~hat is av~ilable in commercial ~uantities. Of course, hydrogen is unneces-sary in the process. Indeed, the only gas necessa~y for the process is carbon monoxide. The off gas coming out of the reactors first goes through condensers which remove some of the water in the gases before going to off gas rotameters which give an indication of the amount of gases coming out of a reactor. The off gases go through an ammonia scrubber and are exited to the atmos-phere.
The reactors themselves are outfitted with gravity overflows so that there is a cascading system from the first through the sixth reactor. In one important emb~diment of the multipoint injection system, each of the~first four reactors is ~ed an equal amount of feed stock. That is, 25 percent of the slurry being pumpe~d from the ore preparation circuit will go into each of the first four reactors. It should be notedl however, that there are a large number of possible ways of accomplishing multipoint injection. That is, the nodule slurry can be injected into twQ,three, five or more reactors and the amount of slurry going into any given reactor need not be equal to the amount going into the others.
It has been found advantageous, however, that there be no nodule injection into at least the last reactor. That ~-is, each portion of nodules should pass through two stages in progression; therefore, there should be no nodule 78 ~:
injection in th~ last stage. It should be noted that - in the pilot plant process there is no nodule injection in the last two stages. ~ach reactor contains a mechanica]
impeller to achieve mechanical agitation which disperses the gas and suspends the solids. It has been established that the reaction rate of cuprous ion regeneration is influenced by gas-liquid mass transfer rate of carbon monoxide. The rate is affected primarily by the ex-tent ;
of gas-liquid interfacial area, which is turn afected by the method used to disperse the gas.
While the nodules are fed to the first four, reactors, carbon monoxide is sparged into the bottom of each reactor as required. The slurry in these reac~ors is approximately 3.5 percent solids and the average, residence time-in the system is twenty minutes per stage.
The slurry overflowing the last reactor is flocculated ~ ~
to enhance settling before entering a clarifier. The ~ ~?
clarifier is used to separated the liquid from the solids. ,~
The reduction-leach circuit also includes a gas `
metering system. As set forth above, the reducing gas is 95 percent ca~bon monoxide and 5 percent hydrogen.
It has also been found advantageous to include a 1 percent methane tracer in the reducing gas. The methane was used , '~
as an aid in establishing material balances. The reducing gas is fed from portable cylinders through a pressure reducing va1ve and a gas totalizer. The gases are metered individually to each of the six reac'tors as required to ~ '-maintain the cuprous ion within various control ranges.
The gases are also sampled by ga~ chromatographs. '~

' ~

8TA~T-UP
The process of the present invention i5 directed toward a continuous process in which nodules are continuous~y processed to produce various desirable metals. In order to reach a continuous steady s~ate, the reactor vessels must be loaded with start-up materials. Thus, each of the six reactors are filled with an ammonia-ammonium carbonate solution containing approximately 100 grams per liter total ammonia and approximately 15 grams per liter tvtal carbon dioxide. After the reactors are ~illed with the ammonia-ammonium carbonate solution, copper metal is added and is partially oxidized. The metal is added as a copper powder and is oxidized to convert some of the copper to cuprous ions. Hydroxyl ions are also produced with the cuprous ions. Enough copper metal is added so that 10 grams per liter copper in solution results. The next step in the start-up procedure i5 to check the cuprous ion concentration. Thus, the mixture in each reactor is analyzed to make sure that the cuprous ion concentration is at an acceptable level of about 7 grams per liter.
If more cuprous ions are needed, this can be accomplishe~
by passing the reducing gas throu~h the bottom of the reactor. The first three reactors have pH loops which consist of a finger pump which pumps the solution to a housing which `contains a pH electrode. The pH is then measured in a readout on a control panel. The pH is a valuable control device and can be used to indicate whether or not the carbon dioxide, ammonia or cupr~us ions have gone off the speci~ied limits.
After the reactor vessels have been loaded for .
start-up as set forth above, the manganese nodules are ~ .
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added to ~he first four reactors. ~he total rate of feed to the four reactors is about 30 pounds per hour of nodulPs.
As the nodules are being ~ed into the reactors, carbon monoxide is sparged through the bottom of the reactors at a total rate of about 70 standard cubic foo~ pex hour.
At this point, it should be noted that the amount of carbon monoxide that i5 fed into each stage of the reactor is controlled by the cuprous ion concentration of the contents of any given reactor. This is determlned by analyzing the contents of the reactor periodically. During start-up, this is done every half hour and is continued once an hour while the process is in ~he steady state stage. ~
?
Approximately 120 gallons per hour of reduction slurry enters the clarifier. The solids leave the bottom of the clarifier in the form of a slurry with approximately a 40 percent solids content. lrhe overflow from the clarifier is clear liquid which constitutes the recycle reduction liquor. However, after leaving the clarifier, ~;
the recycle reduction liquor enters a surge tank where~
UpQn it is passed into an ammonia makeup unit. Gaseous ;;~
ammonia and carbon dioxide are sparged into the ammonia makeup unit in order to keep the ammonia and carbon dioxide ,, . :
content of the liquid at a prescribed level. At steady state, that level is approximately 100 grams per liter ~
ammonia and the CO2 content about approximately 25 grams ~ -~.
per liter. After leaving the makeup unit, the liquid ~i~
is pumped by a metering pump through a heat exchanger into the first reactor and the grlnding mill. The heat exchanger removes heat that has generated in process.

''`~',: ' -15~ ~

OXIDATION AND 1~ SH LEAC~_ In the oxidation and wash-leach circuit, the clarifier underflow is combined with second stage wash liquor and the resulting slurry is oxi~ized with air to convert the cuprous ion in the clarifier underflow to cupric ion to facilitate fu ure processing. The oxidized slurry i5 then pumped to a countercurrent decantation system ~CCD) consisting of se~en stages of countercurrent washing units. The wash-leach steps are carried out on a batch basis in nine tanks. It should be noted that in the pilot plant nine stages are used to simulate a countercurrent wash system. Although this system is not truly countercurrent, it has been able to demonstrate that a seven reactor countercurrent system is advantageous.
The two extra units used in the pilot plant are necessary because oneeunit is either being filled or is being emptied. In the wash-leach system, the metal solubilization is completed as the displacement wash process is carried out. Fresh wash~ uor is added to the seventh stage of the system as a solution containing 100 grams per llter .
2Q ammonla and IOO grams per liter carbon dioxide. Liquor is transferred from one tank of the settled slurry every twelve hours to ancther appropriate tank in the system to affect the countercurrent washing. Thé carbon dioxide concentration varies throu~hout the washing system and exits in the pregnant liquor which contains approximately 65 grams per liter C02. This decrease in C02 concentration is due to the fact that the slurry entering the oxidation and wash-leach circuit has a liquor phase which contains ~;
only 25 grams per liter C02. Pregnant liquor, containing the metal to be recovered, is decanted from the first '' ~ r,; , ~

wash stage and pumped to a surge tank. Fresh ammonia solution without metals is added to the last solids wash stage. The metal values in solution range ~rom approximately 0 in the fresh wash liquor to between 6-8 grams per liter copper and 5-10 grams per liter nickel in the pregnant liquor. Of course, other metal values are also present in the pregnant liquor but nickel and copper are the major metal values of interest.
After the wash-leach step, the pregnant metal bearing liquor is piped off for further processing as is axplained below. The second stage wash is recycled back to the oxidation reactor. The tailings, which are nothing ' more than reduced nodules washed of all their non-ferrous metal values and with the manganese converted to manganese carbonate, are sent to a surge tank. From the surge t~nk, they are then pumped to a steam stripping operation where the ammonia and C02 are driven off. The tailings ~ ' are then drummed. The-ammonia and CO2 obtained in the steam stripper may be recycle~
BMC RECYCLE
A small stream 10 of basic metal carbonates (BMC) ~;
is recycled to the ~irst stage as required to maintain ';~ ;
the total copper in the system at an acceptable leve This stream of basic metal carbonate compensates for ~' unsolubilized copper leavin~ the reduction loop in the clari~ier underflow. To produce stream 10 of ba'sic metal ~' carbonates, a portion of the pregnant liquor 12 (wash '~
effluent) from the oxidation and wash-leach circuit '~
is steam stripped on a batch basis to remove ammonia ~ ''' and carbon dioxide and to precipitate the'basic metal carbonates. The precipitated basic metal carbonates ~,, , ' .,'.
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are dissolved in an aqueous solution containincJ approximately 60 g/l N~13 and 60 g/l C02. This BMC feed is pumped to the first stage of the reduction circuit.
The amount of BMC ~eed added to the reduction cir-cuit varies according to the amount o soluble copper present in the reduction reactors and the copper concen tration desired in the reduction circuit. It has been found advantageous to maintain the soluble copper content o~ the reduction circuit at a level of l0 g/l or greater.
Thus, as the amount of soluble copper in the reduction circuit is depleted, BMC feed is prepared and recycled ;~
to the reduction circuit. Of course, the basic metal values of the BMC feed is controlled by the base metal --content of the nodules processed. The stream l0 of basic metal carbonates primarily contain solubilized copper and nickel; however, small amounts of molybdenum and cobalt are also present. It should be apparent that it lS the amount of copper metal in the BMC feed which controls the amount of BMC recycle feed that is added to the reduction circuit. Further details o~ the BMC ~eed are set forth~elow in a section entitled "SPECIFIC DETAILS
OF THE BMC RECYCLE".
LIX SEPARATION
The pregnant liquor contains various metal values including copper, nickel, cobalt and molybdenum. In the LIX separation circuit, the object is to separate the copper/ nickel, cobalt and molybdenum from each other ~-and from the pregnant liquor. Initially, the copper and nickel are co-extracted by : .

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an organic exLractan~ in a series of mi~erlsettLer units, The organic extractant i9 L~X-64N in a kerosene ba~e, LIX~64N i5 a Trade Mark of General Mllls Chemicals, Inc. and represents an organlc extractant having 2~1lydroxy ben~ophenoxime as an active agent as disclosed in U.S. Patent No. 3,429,449.
The copper and nlckel free l~quor (raffinate) is sent to a storage tank before it is steam stripped.
The organic extractant which contains copper and -nickel values is washed with an NH4 HC03 solution followed by an ammonium sulfate solution to remove ammonia picked up during extraction. This scrubbing operation is carried out in another ;
series of mixer settlers. The organic extractant is then stripped with a weak H2S04 solution (pH about 3) to preferen-tially remove nickel. Thereafter, the copper is stripped, which is accomplished by using a stronger (160 g/l) H2S04 solution. The copper and nickel free organic extractant is recycled to the meeal extraction circuit of the LIX process.
The raffinate which contains only cobalt, molybdenum `~
and some trace impurities that were not extracted into the organic phase is sent into a surge tank for future processing to recover cobalt and molybdenum. In the cobalt and molybdenum recovery circuit, the ammonia and C02 are stripped from the raffinate. The ammonia and C02 are condensed and sent back to ~ ~ -the process for recycling. Hydrated lime is then added to the raffinate in a steam stripper. The resulting slurry is agitated ;
and then allowed to settle. The solution which no longer contains cobalt and molybdenum is recycled back to the process as fresh wash liquor. Ammonia and C02 are added to the solu-tion to bring it up to the prescribed concentration~
ELECTRO~INNING
Metal recovery is accomplisbed by electrowinning Z~7~3 copper and nickel from the ~olution prepared in the LIX plant as describe~1 above~ This pro&ess is perfor~ed on a batch basis for the copper recovery and on a continuou~ basis for the ' ''~

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nickel recovery in ~ se~arate plan~. The metal containing solutions are transferred once a day.
SP~CIFIC DETAILS OF Bl~1C RF,CYCLF, A comparison of the process of the present invention with the known process briefly described above is set forth in the discussion belo~Y which is to be taken in conjunction with Figs. 2 and 3 The ]cnown process is set forth schematical1y in Fig. 2. A
is shown in Fig, 2, in the known process nodules 20 are treated in reaction vessels ~l, 22, 23. The processed nodules then flow into a clarifier at 2~. Pregnant liquor is taken from the clarifier at 26. A portion Or the pregnant liquo~ is recycled at 2~ into reactor . ~ .
21. The portion of the s~ream of pregnant liquor 32 that is not recycled to reactor 21 is sent to the extraction circuit. Reduced pulp 3~ is sent to the wash circuit.
In the process of the present invention, as is shown schematically in Fig. 3, about one quarter of the wash ef~luent stream ~0 is di~verted to a steam stripping. At this point it should be noted that B~;5C recycle rate depends on the copper concentration de-sired in the reduction circuit. Sending about one quarter of the wash ffluent (pregnant liquor) to a BMC steam s~ripper will increase the copper concentration in the reduction reactors nearl~ two and one half time (from 4.3 to lO g/l)~, The basic carbonate precipltate formed in khe steam stripping section 37 is ~iltered at 3~, is dis-solved in water containing NH3 and C02 and is sent to khe reducing circuit with steam 2~. Stream 2~ is recycled directly to the reduc' tion circuit and pre~nant liquor stream 32 is sent to LIX extraction.
The remaining por~ion of the wash effluent 40 is spli~.

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~k~e ~ recycle increases t,~e copper cont~nt as ~ell as the total ~ctal content of a reduction liquor in vessel 21. Th~ upper li~it of copper concentr~tion that can be reached in this manner is controlled by the solubility limit of metal amine carbonates which is b~tween 40~60 g/1.
The following is an example of the steam stripping which occurs within vessel 37. 135 gallons fro~ wash effluent stream ~0 containing ~-g g/l copper and ~-10 g/l ~ickel, was steam s~ripped batchwise. The temperature during stripping rose from an initial 1~0F to 216F~ The precipitate was black and precipitate analysis showed 13.9~ Cus 17r~7c/o Nî, and 5.95~0 C02 indicating a high percentage of cupric oxide in the cake. The precipitate was fil~erable. The residual liquor analyzed 0.095 g/l Cu and 0.154 gll Ni, indicating adequa~e removal of copper and nickel vales.
The precipitate was dissolved in a water solution contain~
ing 100 ~ll NH3 and 45 g/l C02. Dissolution in this solution at ambient temperature (25C) was completed in less ~han 15 minutes.
99~% Cu and 99.4% Ni solubility was obtained.
A comparison of the process o~ the present invention with ~he known process is illustrated further in table "A'7 below.

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, ~.d~4~Z78 At this point it should be noted that the process of the present invention can be accomplished without multiple point injection o~ the nodules. Indeed, the disclosure appearing above relative to Figs. 2 and 3 is directed to a continuous process with single point injec-tion of the nodules. By following the teachings of the present invention, the copper level of the reactor vessels can be increased ln an efficient manner.
The invention may be embodied in othex specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative - and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

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Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a process in which metal values selected from the group consisting of copper, nickel; cobalt and molybdenum are recovered from a manganese containing ore by introducing the ore into a reaction vessel containing cuprous ions in an aqueous ammoniacal ammonium carbonate leach solution to allow the cuprous ions to reduce the manganese oxides in the ore to enable the metal values to be solubilized in the aqueous ammon-iacal ammonium carbonate leach solution and in which cuprous ions are continuously regenerated in the leach solution by a reducing gas wherein the improvement comprises leaching the metal values from said manganese containing ore with said leach solution, recovering a portion of the metal values solubilized in the leach solution as a mixed metal carbonate precipitate and recycling the mixed metal carbonate back to said reaction vessel to increase the solubilized copper content of the leach solution in the reaction vessel.

2. In a process in which metal values selected from the group consisting of copper, nickel, cobalt and molybdenum are recovered from a manganese containing ore by introducing the ore into a reduction reaction vessel in which the ore is reduced, said reduction reaction vessel containing an aqueous ammoniacal ammonium carbonate leach solution of cuprous ions to allow the cuprous ions to reduce the manganese oxides in the ore to enable the metal values to be solubilized in the aqueous ammoniacal ammonium carbonate leach solution and in which cuprous ions are continuously regenerated in the leach solution by a reducing gas wherein the improvement comprises leaching metal values from said manganese containing ore with said leach solution, recovering a portion of the metal values solubilized in the leach solution, after the solubilized metal values leave the reduction reaction vessel, as a mixed metal carbonate precipitate and recycling a sufficient amount of the mixed metal carbonate back to the reduction reaction vessel so as to maintain the soluble copper content of the reduction reaction vessel at a level of at least 10 grams per liter.

3. The process as set forth in claim 2 wherein said solubilized metal values bearing liquor is directed to an extraction circuit and wherein a portion of the pregnant liquor is diverted from the extraction circuit, is steam stripped to obtain a metal carbonate precipitate containing basic copper carbonate and the precipitate is recycled to the reduction reaction vessel in sufficient quantities to maintain a desired level of soluble copper in the reduction reaction vessel.

4. The process as set forth in claim 3 wherein the pre-cipitate is recycled at a rate sufficient to maintain the soluble copper level in the reduction liquor in the reduction reaction vessel between the range of 10 grams per liter to the solubility limit.

5. The process as set forth in claim 2 further comprising washing and leaching the reduced ore with an aqueous solution containing ammonia and carbon dioxide and wherein a portion of the pregnant metal bearing liquor from the circuit in which the reduced ore is washed and leached is steam stripped to remove ammonia and carbon dioxide and to precipitate the basic metal carbonate and wherein the precipitated basic metal carbonates are recycled back to the reduction reaction vessel.

6. The process as set forth in claim S wherein the precipitated basic metal carbonates are dissolved in an aqueous solution containing ammonia and carbon dioxide and are recycled as a stream to the reduction reaction vessel,