CA1214335A - Hydrodynamic recycle of metallic sulfide seed under pressure - Google Patents
Hydrodynamic recycle of metallic sulfide seed under pressureInfo
- Publication number
- CA1214335A CA1214335A CA000430187A CA430187A CA1214335A CA 1214335 A CA1214335 A CA 1214335A CA 000430187 A CA000430187 A CA 000430187A CA 430187 A CA430187 A CA 430187A CA 1214335 A CA1214335 A CA 1214335A
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- Prior art keywords
- pressure
- autoclave
- slurry
- solution
- sulfide
- Prior art date
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J3/00—Processes of utilising sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
- B01J3/04—Pressure vessels, e.g. autoclaves
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G1/00—Methods of preparing compounds of metals not covered by subclasses C01B, C01C, C01D, or C01F, in general
- C01G1/12—Sulfides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
- C01G53/11—Sulfides
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B23/00—Obtaining nickel or cobalt
- C22B23/04—Obtaining nickel or cobalt by wet processes
- C22B23/0453—Treatment or purification of solutions, e.g. obtained by leaching
- C22B23/0461—Treatment or purification of solutions, e.g. obtained by leaching by chemical methods
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/44—Treatment or purification of solutions, e.g. obtained by leaching by chemical processes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Mechanical Engineering (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Inorganic Chemistry (AREA)
- Metallurgy (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process is provided for continuously precipi-tating precipitate-forming ions under elevated temperature and pressure from a solution thereof using recycle precipi-tate seed as a precipitation aid. The process comprises establishing a solution of the precipitation-forming ions, feeding the solution at an elevated temperature and pressure through an autoclave having a series of precipi-tation compartments, and adding a precipitation agent to the solution while it is maintained under elevated tempera-ture and pressure to precipitate the precipitation-forming ions and thus form a precipitate slurry. The slurry is caused to flow out of the autoclave by virtue of the prevailing pressure in the system to a solids-liquid separator which is serially connected in pressure communi-cation with the autoclave, the separator having a dense slurry fluidized leg or an elutriation column and being disposed at an elevation relative to the autoclave to pro-vide a hydrostatic head of the withdrawn slurry in gravity-flow relationship to the autoclave. The precipitate may be continuously elutriated in the column under the pre-vailing pressure so as to provide an upper slurry portion of precipitate fines and a lower portion of product con-centrate. The precipitate fines are then caused to flow by gravity as seed material to the autoclave without requiring the use of pumps for circulating the slurry.
A process is provided for continuously precipi-tating precipitate-forming ions under elevated temperature and pressure from a solution thereof using recycle precipi-tate seed as a precipitation aid. The process comprises establishing a solution of the precipitation-forming ions, feeding the solution at an elevated temperature and pressure through an autoclave having a series of precipi-tation compartments, and adding a precipitation agent to the solution while it is maintained under elevated tempera-ture and pressure to precipitate the precipitation-forming ions and thus form a precipitate slurry. The slurry is caused to flow out of the autoclave by virtue of the prevailing pressure in the system to a solids-liquid separator which is serially connected in pressure communi-cation with the autoclave, the separator having a dense slurry fluidized leg or an elutriation column and being disposed at an elevation relative to the autoclave to pro-vide a hydrostatic head of the withdrawn slurry in gravity-flow relationship to the autoclave. The precipitate may be continuously elutriated in the column under the pre-vailing pressure so as to provide an upper slurry portion of precipitate fines and a lower portion of product con-centrate. The precipitate fines are then caused to flow by gravity as seed material to the autoclave without requiring the use of pumps for circulating the slurry.
Description
--1~
3~1l5 This invention relates to the hydr~dynamic recycle of seed material, e.g., metallic sulfide seed, under pres-sure i~ the precipitation of precipitatio~-forming ions from solutions thereof, for example, the precipitation of 5 nickel and cobalt ions as sulfides ~rom dilute solutions ~tai~ed ~n ~he hydrometa~llurgical recov~ry of n~ckel and cobalt from lateritic ores.
Precipitation of nickel and cobalt as sulfides from either ammoniacal or acidic leach solutions i~ ~ c~m-1~ monly used commercial method. The Moa Bay pla~t in Cubais one of the few commercial operations where nickel and cobalt are precipitated rom acidic leach solutions.
Briefly, the process consists of neutralizi~g the leach llquor ~pressure leaching of lateritic ores wi~ sul~uric 15 acid~ with lime (coral mud) and decanting the ~eutralized liquor which is the~ treated with hydrogen sulfide gas.
T~e ~ulide precipitation is carried out in a ser~es o~
hlgh pressure autoclaves at a temperature of about 120C.
and a total pressure of about 150 psig. A choke controls 20 the ~low of the slurry from a high pressure autoclave to a flash tank. A large amount of H2S gas is dissolved i~
the solution at the high pressure prevalent i~ the auto-c}aves and is released in the flash tank. This released gas, which is several times the amount actually consumed 25 during precipitation, is washed, dried and compressed hy a compressor to high pressure prior to its recycle to the autoclaves. ~he slurry from the flash tank goes ts 3~
a solid~liquld separation step ~thickener~. About two-third~ of the ~ickel sulflde leaving the reactor is returned back to the process for recycl~ng and the remai~ing one-third leaves as the product concentrates.
5 The amo~nt of solid recycle is proportio~ed to give about 20 gpl solids in the fee~ slurry.
The Moa Bay acid leaching proce~s is d}sclosed in an article entitled "Acid Leaching Moa Bay-Nickel"
by E.T. Carlson and C.SO Si~ons (Journal of Metals, 10 March, 1~6~, pp 206-213~
Another sulfide precipitation method is dis-closed in U.S. Patent NoO 2,722,480 (November 1, 1955~.
The method is particularly applicable in the treatment of nlckel solutions resulting from the leaching o~
15 later~tic ore, such solutions generally contain~ng 3 to 13 grams per liter ~gpl) of n~ckel, 0O2 to 0.7 gpl Co, Q.5 to 2.0 gpl Fe , 2 to 8 gpl Al, 1 to 5 gpl Mn, n . 5 to 2~0 gpl Mg, and about 15 to 30 gpl H2SO4. The method comprîses adjust}ng the free acid content of the solution to a p~ of about 1 to 3, adding to the adjusted solution a~out Q~03 to about 10 gpl of finely divided metallic po~der selected from the group consisting of Fe, Ni, and Co and mixtures thereof, confining the solution at a temperature of about 60C. to 90Cn under a positlve 25 over-pressure of hydrogen sulfide gas and contl~uing the treatment with agitation until sulfide precipitat~n su~stantially ceases According to the patent, sub-sta~tially all of the nickel (eOgO, 98 to 99~ i9 pre-clp~tated by this method in about 1 to 2 hour~e 3~ In U~SO Patent No 4,110,400, which issu~d on August 29, 1978, a method is disclosed for efficiently pxec~pitating nickel sulfide from an acidic nickel sulfate solution having a p~ ~etween 1O5 and 4, containing about 1 to 4Q gpl nickel, optionally containing cobalt, and 35 containing sufficient inert soluble sulfate salt to buffer the solution during the precipitation of nickel sulfide at relatively low temperature and pressure. As in the Moa Bay process, the precipitation is carried out ~ 3--under pressure ~n a series of autoclaves, the ~-olution with the precLpitate ~iOe~ the slurry~ ls flashed to ordi~ary pressure, and the flashed solution is then passed to a thickener ~here the slurry is elutriated to 5 recover the product, a portlon of the product being re-cycled as se~d material to the autocla~es as a precip~ta-tion aid.
A disadvantage of the foreg~lng methods i5 the requir~ment for pumps for maintainlng recirculation 10 throughout the autoclave system, particularly in the re-cycling of seed or solld catalysts In the case o~
metallic sulfide precipitation, a ma~or problem is the transport, reslurry and the general handling of der~se, abraslve metal sulfide seed which can result in pump 15 break-down and ther~by adversely affect the overall efficiency of the systemO
It would be desirable to have a precipitation system which does not require the need for a plurality of pumps for mo~ing leach liquor and seed through the auto-20 claves during the precipitation cycle In accordance with the invention there is pro-vided a process for continuously precipitating precLpltate-forming ions under elevated temperature and pressure from a solution of said ions using recycle precipltate seed as 25 a precipitation aid which comprises, establishing a solution of said precipitation-f~rming ionsl, feeding said solutlon at an elevated temperature and pressure through an autoclave having one or a series o~
30 precipitation compartments~
adding a precipitation agent to said solutiorl while it is maintained under said elevated temperature and pressure to form a precipitate of said precipitation-forming ions in the form of a slurry, and causing said slurry to flow out of said auto-clave by virtue of the prevalllng pressure in the sys~em to a serially co~nected solids-liquid separator i~
pjressure commu~ication with said autoclave, 3~
said separator having a lower, den~e ~luidized slurry column and being dLsposed at an elevatlon relative ~o said autoclave to ~rovide a hydrostatic head of said ~it~dra~n slurry ~.n gravity-flow relationship to said autocla~e, said hydrostat~c head being sufficient to provide pressure d~fferential to cause flow of the dense fluldized slurry to said autoclave as seed.
The solids-liquid separatoL ~e.g., classifyi~g thickener~ may have an elutriation column the precipitate 1~ slurry being continuously elutriated in the column under the prevailing pressure so as to provide a dense fluidized slurry havi~g an upper portion of precipitate fines and a lower portio~ of product concentrate and the upper poxtlon of precipitate flnes being caused to flow by gravity 15 ~hydros~atically] as seed material to the autocla~e while the product concentrate is collected at the lower port~o~
of the elutriating columnO
A~ important advantage of the invent;on resides in recycling the precipitate seed under system pressure 20 without requiring the use of pumps. In the case of metal sulfide precipitate, such as nickel sulfide, the slurry of metal sulfide particles in the liquid substantlally barren of metal values flows to a solids-liquid separa~or ~e.g., a thickener~ characterized by a long vertical 25 colum~ or pipe~ The dense solids are caused in one embodiment to flow by gravity to the vertical p~pe sectio~ of the separator where the sollds are fluidized ~y wash water such as to exhibit the properties of a liquid of high density (e.gO, 2 grams~c.c ~ A head of 3~ slurry is developed in the vertical column or pipe of a~out three or four feet, which head is su~tained by the pressure in the system, the head being more than the head lost in discharging the dilute reaction slurry to the higher elevation of the solids-liquid separator ~including 35 friction loss in the discharge piping)~ As a result ~f this imbalance in head, seed solids are a~Le to flow from a point i~ the dense slurry column directly into the pressurized reactor or into the clear liquid feed line ~ 5--leading to the reactor~ The decant barren Liquid from the separator is throttled to atmospheric pressure ~or the next process step of further clarificatlon.
In a demonstration of this technique in the metal sulflde precipitation reaction, the dense slurry column was an elutriation and wash column fluidized by wash water~
The relati~ely coarse bottom slurry was withdrawn as a pro-duct while the finer particles were returned to the reaction vessel or autoclave as seed. The fluidizing wash water dis-places the acid reaction product from the recycle slurry9thus minimizing the circulating acid load to the reactor In one embodiment of the inventionr the recycle seed slurry was intxoduced through a jet in the clear l~quid feed to the reactor. This variation wa~ used to take into account limited headroom for the elevation of the sollds-liquid separator above the reaction autoclave.
In a particular system in which this lnvention was demonstrated, four agitation tanks and four trou~le-prone slurry pumps ~ere eliminated. The operating e~ficiency for the system increased from ~9 to 99 percent.
Mechanical reliability was also enhanced in that the bulk of the coarse slurry did not pass through the pressure let-down system.
The invention is particularly applicable to the continuous precipitation of metal sulfide under elevated temperature and pressure fxom an aqueous solution of sulfide-forming metal ions, such as nickel and/or cobalt, using recycle nickel sulfide seed as a precipitation aid.
The established aqueous solution may in this instance be a leach liquor obtained in the leaching of nickel lateritic ores. The process comprises feeding the solution or leach liquor at an elevated temperature and pressure through at least one autoclave having a series of precipitation com-partments, adding a sulfide-precipitation agent, e.gO, H2S, to the solution while maintaining it under elevated temperature and pressure to precipitate the metal sulfide and thus form a sulfide slurry, causing the slurry to flow out of the autoclave by virtue of the prevailing pressure 3~
in the system to a serially connected solids-liquid separator (e.g., classifying thickener) in pressure com-municat~on with the autoclav~, the separator being char-acterized by an elutriation column and being disposed at an elevation relative to the autoclave to provide a hydrostatic head of the withdrawn slurry so as to effect recycle gravity flow to the autoclave, continuously elutriating the sulfide slurry in the elutriation column while under the prevailing pressure so as to provide an upper slurry portion of sulfide fines in the elutriation column and a lower portion of pro-duct concentrate, and then causing the upper fines portion of the metal sulfide fines to flow by gravity (hydro-statically~ as seed material to the autoclave while collecting the product concentrate at the lower portion of the elutriating column.
The details of the invention will be clearly apparent by referring to the drawing which shows a hydrometallurgical system for precipitating nickel sulfide using H2S as the precipitant, the system comprising an autoclave 10 having a series of compartments A to F, each compartment having a stirrer 11.
Clear liquid feed 12, e.g , pregnant leach liquor, is fed to the autoclave where it is maintained under pressure (for example, 150 psig) as it passes through the autoclave. After pH adjustment in the known manner, H2S
xeagent 13 is injected under pressure into the autoclave to precipitate the metal sulfide (for example, at a solution temperature of about 1209C.). The dilute slurry 14 formed is caused to leave the autoclave by virtue of the pressure in the system and enter the upper end of the solids-liquid separator at 15A which is characterized by a vertical column 16 having a reduce~ lower portion 17, the separator communicating with the autoclave under the prevailing pressure in the system.
As will be noted, the dense slurry 18 is caused to maintain a substantial head above the autoclave. Wash water 19 is injected into the bottom of the column as shown to fluidize the precipitate under conditions such khat the coarse particles are allowed to settle at the lower column portion 17 for removal as product 21 by means of valve 20.
The finer particles are maintained fluidized at the upper end of the column and, by means of the hydrostatic head, are recycled as seed material by gravity flow via valve 22 into clear liquid feed line 12 entering the autoclave. In the alternative, the seed may enter the autoclave directly.
As is clearly apparent, a process is provided for continuously precipitating metal values from solution in which part of the precipitate is recycled as seed material while the total system is under pressure~ the seed recycle being accomplished by maintaining a hydrostatic head of the slurry in the solids-liquid separator while under the pressura prevailing in the system. Because of the lmproved technique employed for effecting recycling of seed material, pumps need not be used in this phase of the process~
The invention is applicable to any high pressure precipitation system in which recycle seed materials is employed as a precipitation aid. However, the invention is particularly applicable to the recovery of nickel and/or cobalt from pregnant leach liquor obtained in the leaching of nickel lateritic ore. As illustrative of the invention, the following typical example is given.
XAMPLE
In the sulfuric acid leaching of nickel laterites, the nickel concentration in the pregnant liquor usually ranges from about 3 to 15 gpl. However, depending upon the starting feed material, e.g~, the addition of alloy scrap, the pregnant liquor concentration may broadly range from about 1 to 40 gpl, an~ optionally cobalt, the cobalt, when present, ranging up to about 5 gpl (e.g., 1 or 2 gpl)O The pH is adjusted to a range of about 1.5 to 4, e.gO, 2.5, following which the solution is subjected to sulfide pre-cipitation with H2S at a pressure ranging from about 5 to 50 psig and a temperature ranging from about 65 tv 110C~ while vigorously agitating the solution in the presence of seed material, for example, at least about 75 gpl of seed material, until substantially complete precipitation obtains.
The seed concentration is at least about 40 gpl may range from about 40 to 300 gpl, In a specific embodiment, reference being made to the clrawing, clear liquid feed 12 containing about 6 gpl nickel clS nickel sulfate and having an adjusted pH of about
3~1l5 This invention relates to the hydr~dynamic recycle of seed material, e.g., metallic sulfide seed, under pres-sure i~ the precipitation of precipitatio~-forming ions from solutions thereof, for example, the precipitation of 5 nickel and cobalt ions as sulfides ~rom dilute solutions ~tai~ed ~n ~he hydrometa~llurgical recov~ry of n~ckel and cobalt from lateritic ores.
Precipitation of nickel and cobalt as sulfides from either ammoniacal or acidic leach solutions i~ ~ c~m-1~ monly used commercial method. The Moa Bay pla~t in Cubais one of the few commercial operations where nickel and cobalt are precipitated rom acidic leach solutions.
Briefly, the process consists of neutralizi~g the leach llquor ~pressure leaching of lateritic ores wi~ sul~uric 15 acid~ with lime (coral mud) and decanting the ~eutralized liquor which is the~ treated with hydrogen sulfide gas.
T~e ~ulide precipitation is carried out in a ser~es o~
hlgh pressure autoclaves at a temperature of about 120C.
and a total pressure of about 150 psig. A choke controls 20 the ~low of the slurry from a high pressure autoclave to a flash tank. A large amount of H2S gas is dissolved i~
the solution at the high pressure prevalent i~ the auto-c}aves and is released in the flash tank. This released gas, which is several times the amount actually consumed 25 during precipitation, is washed, dried and compressed hy a compressor to high pressure prior to its recycle to the autoclaves. ~he slurry from the flash tank goes ts 3~
a solid~liquld separation step ~thickener~. About two-third~ of the ~ickel sulflde leaving the reactor is returned back to the process for recycl~ng and the remai~ing one-third leaves as the product concentrates.
5 The amo~nt of solid recycle is proportio~ed to give about 20 gpl solids in the fee~ slurry.
The Moa Bay acid leaching proce~s is d}sclosed in an article entitled "Acid Leaching Moa Bay-Nickel"
by E.T. Carlson and C.SO Si~ons (Journal of Metals, 10 March, 1~6~, pp 206-213~
Another sulfide precipitation method is dis-closed in U.S. Patent NoO 2,722,480 (November 1, 1955~.
The method is particularly applicable in the treatment of nlckel solutions resulting from the leaching o~
15 later~tic ore, such solutions generally contain~ng 3 to 13 grams per liter ~gpl) of n~ckel, 0O2 to 0.7 gpl Co, Q.5 to 2.0 gpl Fe , 2 to 8 gpl Al, 1 to 5 gpl Mn, n . 5 to 2~0 gpl Mg, and about 15 to 30 gpl H2SO4. The method comprîses adjust}ng the free acid content of the solution to a p~ of about 1 to 3, adding to the adjusted solution a~out Q~03 to about 10 gpl of finely divided metallic po~der selected from the group consisting of Fe, Ni, and Co and mixtures thereof, confining the solution at a temperature of about 60C. to 90Cn under a positlve 25 over-pressure of hydrogen sulfide gas and contl~uing the treatment with agitation until sulfide precipitat~n su~stantially ceases According to the patent, sub-sta~tially all of the nickel (eOgO, 98 to 99~ i9 pre-clp~tated by this method in about 1 to 2 hour~e 3~ In U~SO Patent No 4,110,400, which issu~d on August 29, 1978, a method is disclosed for efficiently pxec~pitating nickel sulfide from an acidic nickel sulfate solution having a p~ ~etween 1O5 and 4, containing about 1 to 4Q gpl nickel, optionally containing cobalt, and 35 containing sufficient inert soluble sulfate salt to buffer the solution during the precipitation of nickel sulfide at relatively low temperature and pressure. As in the Moa Bay process, the precipitation is carried out ~ 3--under pressure ~n a series of autoclaves, the ~-olution with the precLpitate ~iOe~ the slurry~ ls flashed to ordi~ary pressure, and the flashed solution is then passed to a thickener ~here the slurry is elutriated to 5 recover the product, a portlon of the product being re-cycled as se~d material to the autocla~es as a precip~ta-tion aid.
A disadvantage of the foreg~lng methods i5 the requir~ment for pumps for maintainlng recirculation 10 throughout the autoclave system, particularly in the re-cycling of seed or solld catalysts In the case o~
metallic sulfide precipitation, a ma~or problem is the transport, reslurry and the general handling of der~se, abraslve metal sulfide seed which can result in pump 15 break-down and ther~by adversely affect the overall efficiency of the systemO
It would be desirable to have a precipitation system which does not require the need for a plurality of pumps for mo~ing leach liquor and seed through the auto-20 claves during the precipitation cycle In accordance with the invention there is pro-vided a process for continuously precipitating precLpltate-forming ions under elevated temperature and pressure from a solution of said ions using recycle precipltate seed as 25 a precipitation aid which comprises, establishing a solution of said precipitation-f~rming ionsl, feeding said solutlon at an elevated temperature and pressure through an autoclave having one or a series o~
30 precipitation compartments~
adding a precipitation agent to said solutiorl while it is maintained under said elevated temperature and pressure to form a precipitate of said precipitation-forming ions in the form of a slurry, and causing said slurry to flow out of said auto-clave by virtue of the prevalllng pressure in the sys~em to a serially co~nected solids-liquid separator i~
pjressure commu~ication with said autoclave, 3~
said separator having a lower, den~e ~luidized slurry column and being dLsposed at an elevatlon relative ~o said autoclave to ~rovide a hydrostatic head of said ~it~dra~n slurry ~.n gravity-flow relationship to said autocla~e, said hydrostat~c head being sufficient to provide pressure d~fferential to cause flow of the dense fluldized slurry to said autoclave as seed.
The solids-liquid separatoL ~e.g., classifyi~g thickener~ may have an elutriation column the precipitate 1~ slurry being continuously elutriated in the column under the prevailing pressure so as to provide a dense fluidized slurry havi~g an upper portion of precipitate fines and a lower portio~ of product concentrate and the upper poxtlon of precipitate flnes being caused to flow by gravity 15 ~hydros~atically] as seed material to the autocla~e while the product concentrate is collected at the lower port~o~
of the elutriating columnO
A~ important advantage of the invent;on resides in recycling the precipitate seed under system pressure 20 without requiring the use of pumps. In the case of metal sulfide precipitate, such as nickel sulfide, the slurry of metal sulfide particles in the liquid substantlally barren of metal values flows to a solids-liquid separa~or ~e.g., a thickener~ characterized by a long vertical 25 colum~ or pipe~ The dense solids are caused in one embodiment to flow by gravity to the vertical p~pe sectio~ of the separator where the sollds are fluidized ~y wash water such as to exhibit the properties of a liquid of high density (e.gO, 2 grams~c.c ~ A head of 3~ slurry is developed in the vertical column or pipe of a~out three or four feet, which head is su~tained by the pressure in the system, the head being more than the head lost in discharging the dilute reaction slurry to the higher elevation of the solids-liquid separator ~including 35 friction loss in the discharge piping)~ As a result ~f this imbalance in head, seed solids are a~Le to flow from a point i~ the dense slurry column directly into the pressurized reactor or into the clear liquid feed line ~ 5--leading to the reactor~ The decant barren Liquid from the separator is throttled to atmospheric pressure ~or the next process step of further clarificatlon.
In a demonstration of this technique in the metal sulflde precipitation reaction, the dense slurry column was an elutriation and wash column fluidized by wash water~
The relati~ely coarse bottom slurry was withdrawn as a pro-duct while the finer particles were returned to the reaction vessel or autoclave as seed. The fluidizing wash water dis-places the acid reaction product from the recycle slurry9thus minimizing the circulating acid load to the reactor In one embodiment of the inventionr the recycle seed slurry was intxoduced through a jet in the clear l~quid feed to the reactor. This variation wa~ used to take into account limited headroom for the elevation of the sollds-liquid separator above the reaction autoclave.
In a particular system in which this lnvention was demonstrated, four agitation tanks and four trou~le-prone slurry pumps ~ere eliminated. The operating e~ficiency for the system increased from ~9 to 99 percent.
Mechanical reliability was also enhanced in that the bulk of the coarse slurry did not pass through the pressure let-down system.
The invention is particularly applicable to the continuous precipitation of metal sulfide under elevated temperature and pressure fxom an aqueous solution of sulfide-forming metal ions, such as nickel and/or cobalt, using recycle nickel sulfide seed as a precipitation aid.
The established aqueous solution may in this instance be a leach liquor obtained in the leaching of nickel lateritic ores. The process comprises feeding the solution or leach liquor at an elevated temperature and pressure through at least one autoclave having a series of precipitation com-partments, adding a sulfide-precipitation agent, e.gO, H2S, to the solution while maintaining it under elevated temperature and pressure to precipitate the metal sulfide and thus form a sulfide slurry, causing the slurry to flow out of the autoclave by virtue of the prevailing pressure 3~
in the system to a serially connected solids-liquid separator (e.g., classifying thickener) in pressure com-municat~on with the autoclav~, the separator being char-acterized by an elutriation column and being disposed at an elevation relative to the autoclave to provide a hydrostatic head of the withdrawn slurry so as to effect recycle gravity flow to the autoclave, continuously elutriating the sulfide slurry in the elutriation column while under the prevailing pressure so as to provide an upper slurry portion of sulfide fines in the elutriation column and a lower portion of pro-duct concentrate, and then causing the upper fines portion of the metal sulfide fines to flow by gravity (hydro-statically~ as seed material to the autoclave while collecting the product concentrate at the lower portion of the elutriating column.
The details of the invention will be clearly apparent by referring to the drawing which shows a hydrometallurgical system for precipitating nickel sulfide using H2S as the precipitant, the system comprising an autoclave 10 having a series of compartments A to F, each compartment having a stirrer 11.
Clear liquid feed 12, e.g , pregnant leach liquor, is fed to the autoclave where it is maintained under pressure (for example, 150 psig) as it passes through the autoclave. After pH adjustment in the known manner, H2S
xeagent 13 is injected under pressure into the autoclave to precipitate the metal sulfide (for example, at a solution temperature of about 1209C.). The dilute slurry 14 formed is caused to leave the autoclave by virtue of the pressure in the system and enter the upper end of the solids-liquid separator at 15A which is characterized by a vertical column 16 having a reduce~ lower portion 17, the separator communicating with the autoclave under the prevailing pressure in the system.
As will be noted, the dense slurry 18 is caused to maintain a substantial head above the autoclave. Wash water 19 is injected into the bottom of the column as shown to fluidize the precipitate under conditions such khat the coarse particles are allowed to settle at the lower column portion 17 for removal as product 21 by means of valve 20.
The finer particles are maintained fluidized at the upper end of the column and, by means of the hydrostatic head, are recycled as seed material by gravity flow via valve 22 into clear liquid feed line 12 entering the autoclave. In the alternative, the seed may enter the autoclave directly.
As is clearly apparent, a process is provided for continuously precipitating metal values from solution in which part of the precipitate is recycled as seed material while the total system is under pressure~ the seed recycle being accomplished by maintaining a hydrostatic head of the slurry in the solids-liquid separator while under the pressura prevailing in the system. Because of the lmproved technique employed for effecting recycling of seed material, pumps need not be used in this phase of the process~
The invention is applicable to any high pressure precipitation system in which recycle seed materials is employed as a precipitation aid. However, the invention is particularly applicable to the recovery of nickel and/or cobalt from pregnant leach liquor obtained in the leaching of nickel lateritic ore. As illustrative of the invention, the following typical example is given.
XAMPLE
In the sulfuric acid leaching of nickel laterites, the nickel concentration in the pregnant liquor usually ranges from about 3 to 15 gpl. However, depending upon the starting feed material, e.g~, the addition of alloy scrap, the pregnant liquor concentration may broadly range from about 1 to 40 gpl, an~ optionally cobalt, the cobalt, when present, ranging up to about 5 gpl (e.g., 1 or 2 gpl)O The pH is adjusted to a range of about 1.5 to 4, e.gO, 2.5, following which the solution is subjected to sulfide pre-cipitation with H2S at a pressure ranging from about 5 to 50 psig and a temperature ranging from about 65 tv 110C~ while vigorously agitating the solution in the presence of seed material, for example, at least about 75 gpl of seed material, until substantially complete precipitation obtains.
The seed concentration is at least about 40 gpl may range from about 40 to 300 gpl, In a specific embodiment, reference being made to the clrawing, clear liquid feed 12 containing about 6 gpl nickel clS nickel sulfate and having an adjusted pH of about
2.5 is fed to autoclave 10 as shown maintained under a circuit pressure (autoclave and solids-liquid separator 15) of about 20 psig and a temperature of about 95C.
Dilute slurry 14 is withdrawn under pressure and pa~sed to solids-liquid separator lS where the precipitate is fluidized by flowing wash water 19 upwardly in column 16-17 to provide a dense slurry of fines 18 and a coarse product 21 which is withdrawn from the bottom of column 17 via valve 20. The fines are recycled to the autoclave via valve 22 through clear liquid feed line 12, the amount of fines xecycled being sufficient to provide a seeds content in the autoclave of about 150 gpl.
The precipitation cycle is continued untll all o the pregnant liquor has been processed.
,~
Dilute slurry 14 is withdrawn under pressure and pa~sed to solids-liquid separator lS where the precipitate is fluidized by flowing wash water 19 upwardly in column 16-17 to provide a dense slurry of fines 18 and a coarse product 21 which is withdrawn from the bottom of column 17 via valve 20. The fines are recycled to the autoclave via valve 22 through clear liquid feed line 12, the amount of fines xecycled being sufficient to provide a seeds content in the autoclave of about 150 gpl.
The precipitation cycle is continued untll all o the pregnant liquor has been processed.
,~
Claims (17)
1. A process for continuously precipitating precipitate-forming metal ions under elevated temperature and pressure from a solution of said ions using recycle precipitate seed as a precipitation aid which comprises:
establishing a solution of said precipitation-forming ions under elevated temperature and pressure, feeding said solution at said elevated temperature and pressure in a closed system through an autoclave having one or a series of precipitation compartments, adding a sulfur containing precipitation agent under pressure to said solution while it is maintained under said elevated temperature and pressure to form a precipitate of said precipitation-forming ions in the form of a slurry, causing said slurry to flow out of said autoclave by virtue of the prevailing pressure in the closed system to a serially connected solids-liquid separator in pressure communication with said autoclave and connected as part of the closed pressurized system, said separator having an elutriation column and being disposed at an elevation relative to said autoclave by virtue of the pressure in the closed system to provide a hydrostatic head of recycle slurry of said withdrawn slurry within said closed system in re-cycle gravity-flow relationship to said autoclave while under the pressure of said system, continuously elutriating said precipitate slurry in said column while under said pres-sure in the closed system so as to provide an upper slurry portion of recyclable precipi-tate fines and a lower portion of product concentrate, and causing said upper portion of said pre-cipitate fines while under said system pres-sure to flow by gravity as recycle seed material to said autoclave while collecting and discharging said product concentrate at the lower portion of said elutriating column and while maintaining the closed system, including the elutriation column, under the pressure prevailing therein.
establishing a solution of said precipitation-forming ions under elevated temperature and pressure, feeding said solution at said elevated temperature and pressure in a closed system through an autoclave having one or a series of precipitation compartments, adding a sulfur containing precipitation agent under pressure to said solution while it is maintained under said elevated temperature and pressure to form a precipitate of said precipitation-forming ions in the form of a slurry, causing said slurry to flow out of said autoclave by virtue of the prevailing pressure in the closed system to a serially connected solids-liquid separator in pressure communication with said autoclave and connected as part of the closed pressurized system, said separator having an elutriation column and being disposed at an elevation relative to said autoclave by virtue of the pressure in the closed system to provide a hydrostatic head of recycle slurry of said withdrawn slurry within said closed system in re-cycle gravity-flow relationship to said autoclave while under the pressure of said system, continuously elutriating said precipitate slurry in said column while under said pres-sure in the closed system so as to provide an upper slurry portion of recyclable precipi-tate fines and a lower portion of product concentrate, and causing said upper portion of said pre-cipitate fines while under said system pres-sure to flow by gravity as recycle seed material to said autoclave while collecting and discharging said product concentrate at the lower portion of said elutriating column and while maintaining the closed system, including the elutriation column, under the pressure prevailing therein.
2. The process of claim 1, wherein the precipitate-form-ing ions are nickel in the form of nickel sulfate and wherein the precipitation agent is a sulfur-containing agent that reacts with nickel ions to form nickel sulfide.
3. The process of claim 1, wherein the solution elutri-ated results in a barren liquor portion at the top portion of the separator which is removed and passaged to pressure let-down.
4. A process for continuously precipitating metal sulfide under elevated temperature and pressure from an aqeuous solution of sulfide-forming metal ions using recycle metal sulfide seed as a precipitation aid which comprises, establishing an aqueous solution of sulfide-forming metal ions, feeding said solution at said elevated temperature and pressure in a closed system through an autoclave having a series of precipitation compartments, adding a sulfide-precipitation agent under pressure to said solution while maintained under said elevated temperature and pressure to precipitate said metal sulfide and thus form a sulfide slurry, causing said slurry to flow out of said auto-clave by virture of the prevailing pressure in the closed system to a serially connected solids-liquid separator in pressure communication with said auto-clave and connected as part of the closed pressurized system, said separator having an elutri-ation column and being disposed at an elevation relative to said autoclave by virtue of the pres-sure in the closed system to pro-vide a hydrostatic head of recycle slurry of said withdrawn slurry within said closed system so as to effect recycle gravity flow to said autoclave while under the pressure of said system, continuously elutriating said sulfide slurry in said column while under said pressure in the closed system so as to provide an upper slurry portion of recyclable sulfide fines and a lower portion of product concentrate, and causing said upper fines portion of said metal sulfide fines while under said system pressure to flow by gravity as recycle seed material to said autoclave while collecting said product concentrate at the lower portion of said elutriating column and while main-taining the closed system, including the elutriation column, under the pressure pre-vailing therein.
5. The process of claim 4, wherein the sulfide-forming ions in solution are nickel.
6. The process of claim 4, wherein the solution of sulfide-forming ions is a sulfuric acid solution containing nickel as nickel sulfate and wherein the sulfide-precipitation agent is H2S.
7. The process of claim 6, wherein the pH of the solution ranges from about 1.5 yo 4.
8. The process of claim 7, wherein the pressure in the system ranges from about 5 to 50 psig and the temperature from about 65 to 110°C.
9. The process of claim 4, wherein the solution elutri-ated results in a barren liquor portion at the top of the sepa-rator which is removed and passed to pressure let-down.
10. The process of claim 8, wherein the recycle of seed is adjusted such as to provide a seed concentration in the auto-clave of at least about 40 gpl.
11. The process of claim 10, wherein the concentration of recycle seed in the autoclave ranges from about 40 to 300 gpl.
12. A process for continuously precipitating nickel sulfide under elevated temperature and pressure from an aqueous solution of sulfide-forming metal ions using recycle metal sulfide seed as a precipitation aid which comprises, establishing an aqueous solution of nickel obtained by leaching a nickel laterite ore, feeding said solution containing about 1 to 40 gpl nickel ions at said elevated tempera-ture and pressure in a closed system through an autoclave having a series of precipitation compartments, said solution having a pH ranging from 1.5 to 4, adding a sulfide-precipitation agent under pressure to said solution while maintained under said elevated temperature and pressure to precipitate and metal sulfide and thus form a sulfide slurry, causing said slurry to flow out of said auto-clave by virtue of the prevailing pressure in the closed system to a serially connected solids-liquid separator in pressure communication with said autoclave and connected as part of the closed pressurized system, said separator having an elutri-ation column and being disposed at an elevation relative to said autoclave by virtue of the pres-sure in the closed system to pro-vide a hydrostatic head of said withdrawn slurry within said closed system so as to effect re-cycle gravity flow to said auto-clave while under the pressure of said system, continuously elutrlating said sulfide slurry in said column while under said pressure so as to provide an upper slurry portion of re-cyclable sulfide fines and a lower portion of product concentrate, and causing said upper fines portion of said metal sulfide fines while under said system pressure to flow by gravity as recycle seed material to said autoclave while collecting said product concentrate at the lower portion of said elutriating column and while main-taining the closed system, including the elutriation column, under the pressure pre-vailing therein.
13. The process of claim 12, wherein the temperature of the solution ranges from about 65 to 110°C and the pressure from about 5 to 50 psig.
14. The process of claim 12, wherein the solution entering the autoclave contains about 3 to 15 gpl nickel and wherein the precipitation agent is H2S.
15. The process of claim 12, wherein the solution elutri-ated results in a barren liquor portion at the top portion of the separator which is removed and passed to pressure let-down.
16. The process of claim 12, wherein the recycle seed is adjusted such as to provide a seed concentration in the auto-clave of at least about 40 gpl.
17. The process of claim 16, wherein the concentration of recycle seed in the autoclave ranges from about 40 to 300 gpl.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US39045182A | 1982-06-21 | 1982-06-21 | |
| US390,451 | 1982-06-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1214335A true CA1214335A (en) | 1986-11-25 |
Family
ID=23542506
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000430187A Expired CA1214335A (en) | 1982-06-21 | 1983-06-10 | Hydrodynamic recycle of metallic sulfide seed under pressure |
Country Status (6)
| Country | Link |
|---|---|
| AU (1) | AU1578883A (en) |
| BR (1) | BR8303263A (en) |
| CA (1) | CA1214335A (en) |
| FR (1) | FR2528719B1 (en) |
| GR (1) | GR78311B (en) |
| PH (1) | PH18469A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103397185A (en) * | 2013-06-24 | 2013-11-20 | 中南大学 | Method for calcium removal during iron precipitation of nickel sulfate solution containing iron and free sulfuric acid |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI75868C (en) * | 1986-10-03 | 1988-08-08 | Outokumpu Oy | SAETT ATT UTFAELLA OCH AVSKILJA METALLER. |
| CA1324724C (en) * | 1986-08-18 | 1993-11-30 | George Houlachi | Process for the removal of cobalt impurities from zinc sulphate solutions |
| FI106635B (en) * | 1999-11-09 | 2001-03-15 | Outokumpu Oy | Process for reducing nickel out of an aqueous solution |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2722480A (en) * | 1954-06-21 | 1955-11-01 | Chemical Construction Corp | Catalytic precipitation of nickel, cobalt and zinc sulfides from dilute acid solutions |
| FR1226788A (en) * | 1959-05-05 | 1960-08-16 | Sherritt Gordon Mines Ltd | Process for the treatment of lateritic ores |
| FR1384908A (en) * | 1962-07-25 | 1965-01-08 | Sherritt Gordon Mines Ltd | Process for the recovery by sulphation of oxidized nickel and cobalt in ores and concentrates |
| CA1035152A (en) * | 1974-09-19 | 1978-07-25 | Inco Limited | Recovery of nickel from nickel sulfate solutions |
| US4110400A (en) * | 1977-08-01 | 1978-08-29 | Amax Inc. | Selective precipitation of nickel and cobalt sulfides from acidic sulfate solution |
-
1983
- 1983-06-10 CA CA000430187A patent/CA1214335A/en not_active Expired
- 1983-06-14 PH PH29051A patent/PH18469A/en unknown
- 1983-06-15 GR GR71681A patent/GR78311B/el unknown
- 1983-06-15 AU AU15788/83A patent/AU1578883A/en not_active Abandoned
- 1983-06-20 BR BR8303263A patent/BR8303263A/en unknown
- 1983-06-20 FR FR8310180A patent/FR2528719B1/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103397185A (en) * | 2013-06-24 | 2013-11-20 | 中南大学 | Method for calcium removal during iron precipitation of nickel sulfate solution containing iron and free sulfuric acid |
Also Published As
| Publication number | Publication date |
|---|---|
| GR78311B (en) | 1984-09-26 |
| AU1578883A (en) | 1984-01-05 |
| PH18469A (en) | 1985-07-18 |
| FR2528719A1 (en) | 1983-12-23 |
| FR2528719B1 (en) | 1988-12-09 |
| BR8303263A (en) | 1984-02-07 |
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