CA1297265C - Process of producing lithium carbonate - Google Patents
Process of producing lithium carbonateInfo
- Publication number
- CA1297265C CA1297265C CA000537850A CA537850A CA1297265C CA 1297265 C CA1297265 C CA 1297265C CA 000537850 A CA000537850 A CA 000537850A CA 537850 A CA537850 A CA 537850A CA 1297265 C CA1297265 C CA 1297265C
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- Prior art keywords
- lithium
- ore
- process according
- leached
- sulfuric acid
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/08—Carbonates; Bicarbonates
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
In a process of producing lithium carbonate from decrepitable ores or ore concentrates which contain lithium, particularly from alpha-spodumene, petalite and lepidolite, the ore or ore concentrate is transformed at temperatures from about 800 to 1100°C to a form from which the lithium component can be leached, the lithium in the decrepitated material is converted to lithium sulfate by a solubilizing roasting treatment with a surplus of concentrated sulfuric acid. The roasted product is leached with water and the extract is filtered from the residue, precipitated impurities are removed from the filtrate and the latter is subsequently treated with a concentrated sodium carbonate solution to effect a precipitation of lithium carbonate, which is recovered to transform the disintegrated ore or ore concentrate into a leachable form. The disintegrated ore or ore concentrate is transformed to a leachable form in that it is subjected to a shock heating to at least 800°C and not in excess of 1300°C as it is introduced into a circulating fluidized bed.
In a process of producing lithium carbonate from decrepitable ores or ore concentrates which contain lithium, particularly from alpha-spodumene, petalite and lepidolite, the ore or ore concentrate is transformed at temperatures from about 800 to 1100°C to a form from which the lithium component can be leached, the lithium in the decrepitated material is converted to lithium sulfate by a solubilizing roasting treatment with a surplus of concentrated sulfuric acid. The roasted product is leached with water and the extract is filtered from the residue, precipitated impurities are removed from the filtrate and the latter is subsequently treated with a concentrated sodium carbonate solution to effect a precipitation of lithium carbonate, which is recovered to transform the disintegrated ore or ore concentrate into a leachable form. The disintegrated ore or ore concentrate is transformed to a leachable form in that it is subjected to a shock heating to at least 800°C and not in excess of 1300°C as it is introduced into a circulating fluidized bed.
Description
The present invention relates to a process of produciny lithium carbonate from lithium-containing de-crepitable ores or ore concentrates.
It is known that lithium ores or lithium ore concentrates, such as spodumene or petalite, can be subjected to a thermal treatment, which is usually described as decrepitation, and results in a state in which the material can be solubilized by an acid. By the decrepitation, which is usually effected in a rotary kiln at about 1000 to 1100C, spodumene is transformed from the alpha modification to the beta modification and petalite is transformed to beta-spodumene and quartz.
/
/
, / .
~2g~2fiS
After the decrepitation the beta-spodumene may be ground further and is treated with concentrated sulfuric acid used in a surplus with respect to the lithium content of the ore. The mixture which is ~irtually as moist as earth is charged into a suitable furnace, such as a rotary kiln, and is solubilized therein at temperatures from about 250 to 300 C. When tne lithium content of the ore is in the form of soluble lithium sulfate, the reaction mixture is charged into suitable l-achin~ tanks, in which the lithium sulfate is leached out by means of hot water, w!lich is usually conducted in a countercurrent to the re~ction mixture~ Sodium carbon_te is added to tne extract in a quantity Nhich is sufficient for the adjustment of a pH value of about 6 to 7 so that impurities such as calcium, magnesium, iron and aluminum will be precipitated as insoluble compounds~ When the residue has been separated, a ~ncentrated solution of lithium sulfate is available, which is treated with a concentrated sodium carbonate solution at elevated temperatures so ~at lithium carbonate is precipitated, which is subsequently recovered.
It is also known that the decrepitation can be effected in furnaces other than a rotary kiln, e.gO, in muffle furnaces and in fluidized bed reactors (U.S.
Patent 3~017~243)o The fact that rotary l~ilns, multiple-hearth furnaces or muLffle furnaces can be used just a~
fluidized bed reactors permits of th~ conclusion that it has been believed that the nature of the treatment and the manner in which the ground ore is heated to the transformation temperature are not significant (U.S. Patent 2,516,109).
It is an object of the invention to permit the production of ]ithium carbonate from decrepitable lithium ores or ore concentrates in a process which ensures that the lithium will be virtually completely extractable.
According to the present invention there is provided a process of producing lithium carbonate from lithium-containillg decrepitable ores or ore concentrates, wherein the ore or ore concentrate is transformed at temperatures from about 800 to 1100C to a form from which the lithium component can be leached, the lithium in the decrepitated material is converted to lithium sulfate by a solubilizing roasting treatment with a surplus of concentrated sulfuric acid, the roasted product is leached with water and the extract is filtered from the residue, precipitated impurities are removed from the filtrate and the latter is subsequently treated with a concentrated sodium carbonate solution to effect a precipitation of lithium carbonate, which is recovered, characterized in that the disintegrated ore or ore concentrate is transformed to a leachable form in that it is subjected to a shock heating to at least 800C as it is introduced into a circulating fluidized bed.
The ore or ore concentrate is preferably shock-heated to a temperature which is not in excess of 1300 C.
The term shock heating means that ore or ore concentrate which has not been thermally treated before is charged into a circulating fluidized bed and the temperature of said bed is controlled by a combustion of gaseous, liquid or solid fuel, such as coal. Any fuel may be used which will not adversely affect the subsequent treatments.
Within the scope of the invention the decrepiting thermal treatment is effected in an expanded fluidized bed, which is basically known per se. From an "orthodox"
fluidi~ed bed, in which a dense phase is separated by a distinct stepindensity from the ove~
12972~S
an expanded fluidized bed differs in that it comprises states of distribution having no defined boundary layers.
There is ~o step in density between a dense phase and an overlying gas space but the solids concentration in the reactor decreases gradually from bottom to top.
On principle, the oxygen-containing gases required for the combustion can be added in one s~age. But it will be particularly desirable to supply the oxygen-containing gas required for the combustion process to the fluidized bed in two partial streams on different levels. That mode of operation will result in a SOI`t combustion in two stages so that there will be no local overheating and the formation of NOx gases will be suppres 5 ed.
In case of a multista~e combustion, vi~u-ally any gas which will not adversely affect the nature of the exhaust gas can be used as a fluidized gas. E~r instance, the fluidizing gas may consist of a gas which is non-reactive under the conditions existing in the circulating fluidized bed, e.g., of a recycled flue gas (exhaust gas), nitrogen and water vapor. But for an intensification of the combustion gas it will be desir-able to use a fluidizlng gas consisting of a partial stream of the ox~gen-containing gases to be supplied.
~ t is apparent that in a preferred embodiment the process may be carried out in the following ways:
~29~265 10 The fluidizing gas consists of a gas which is inert under -the conditions in the fluidized bed. In that case the oxygen-containing combustion gas is supplied as a secondary gas on at least two spaced apart levels.
20 An oxygen-containing gas is used also as a fluidizing gasO In that case it will be sufficient to suppl~y secondary gas on one level although in that case the secondary gas may also be supplied on a plurality of levels.
It will be desirable to provide a plurality of inlets for the secondary gas on each level on wnich said gas is suppliedO The volume ratio of fluidizing gas to second-ary ~as should be in the range from 1:20 to ~
l'he secondary gas is suitably supplied on a level ~ihich is spaced above the inlet for the fluidizing ~as at least 1 meter and up to 3~j~ of the overall hei~ht of ~he fluidized bed reactor. If the second~r~ gas is supplied on a plurality of levels, the reference to 3~/o is appli-~able to the uppermost inlet level for the secondary gas.
A supply on that level will provide for a sufficiently l~rge space for the first combustion st~ge for an almost complete reaction between combustible constituents and oxy~en-containing gas - whether it is sup~lied on a lower level as a fluidizing or secondary gas - and -~ill permit the provision of a sufficiently large zone for a complete combustion in the upper reaction space above the secondary 129~26S
gas inlet level.
The gas velocities maintained in the fluidized bed reactor above the secondary gas inlet may amount, as a rule, to more than 5 m/sec. and up to 15 m/sec..
The ratio of the diameter to the height of the fluidized-bed reactor should be selected to provide for gas residence times from 0.5 to 8.0 sec., preferably 1 to 4 seconds.
The mean suspension density to be maintained in the fluidized bed may vary within wide limits and may be as high as 100 kg/m3. To minimize the pressure drop, a mean suspension density in the range from 10 to 40 kg/m3 should be maintained above the secondar~ gas inlet level.
The definition of the operating conditions by the Froude ~nd ~rchimedes numbers results in the follow-ing ranges:
001 _ 3/4 x Fr2 x ~g --- ~ 10 ~ Pk Pg or 0.01 ~ Ar ~ 100 wherein Ar = k ~k ~g x Fr2 =
and ~97~6S
u = the relative gas velocity in m/sec.
Ar = the Archimedes number Fr = the Froude number ~g = density of the ga~ in kg/m3 k = the density of the solid particle in kg/m3 dk = the diameter of the spherical particls in m = the kinematic viscosity in m2/sec.
g = the acceleration due to gravity in m/sec.2 After the thermal treatment in the fluidized bed the product is usually cooled, suitably in a fluidized bed cooler, which may comprise a plurality of stagesc ~he sensible heat of the product may be used to generate steam and/or to heat the oxygen-containing gas which is to be supplied to the circulating fluid~zed bed.
~ he exhaust gases from the circulating fluidized bed are cooled in a waste heat boiler for a generation of steam, which may be used, e.g., in the subsequent leaching stages. Alternatively, if the su~se quent roasting is effected in a directly heated rotary kiln, the exhaust gases may be used to heat such kiln.
The invention permits of a high through-put rate and permits those components from which the lithium component can be leached out to be transformed to a particulerly highly reactive formO Besides, a material ~29726S
is made a~ailable which has a large surface area and in which the lithium ions are particularly easily and complete-ly accessible for chemical reactions. dn additional acti-~ation can be effected in that the thermal treatment in the fluidized bed reactor is effected in the presence of additives wnich are known per see and influence the modification.
In the process in accordance with the invention it is not critical to use an ore or ore concen-trate having a particularly small particle size. It is generally sufficient to effect a disin~egration to a particle size from 1 to lO mmO Smaller particle sizes, e.g., below 10CO!um, .~ill further increase the heating-up rateO
The decrepited material is subsequently solubilized in Xnown manner in a homogeneous mixture with sulfuric acid. Sulfuric acid having a concentration from 90 to 94 ~ is usually employed for that purpose in a surplus from 30 to lO0 ~ with respect to tne litnium content of the oreO In the process in accordance with the present invention t`ne homogeneous mixture of heat-treated ore or ore concen-trate an~ concentrated sulfuric acid is solubilized by a supp^-ly of heat at a temperature from 250 to 320 C. ~hat solubi-lizing roasting treatment is desirably ef ected in a rotary Xiln, which may be directly or indirectly heatedO An indirect heatin~ nill afford the special advantage tnat the surplus free sull'uric acid which has been expelled during the ~297Z6S
roastiug treatment can be directly re-u~ed and can be directly recycled to the solubilizing stageO Adirect heating will afford the advantage that the exhaust gases from the circulating fluidized bed can be used and that the expelled sulfuric acid can also be re-used.
For a recovery of the soluble lithium sul fate now contained in the roasted product, the latter is leached in known manner in a plurality of stirred vessels, which are connected in series and in which the roasted product and water flow in countercurrent streamsO After the leaching t~e residues, which mainly contain silicates, are separated. In accordance with the invention the process parameters are so selected that the resulting solution contains lithium sulfate in a concentration from about 200 to 250/1 Li2S04.
In addition to lithium sulfate and sodium sulfate, the filtrate may contain other impurities, such as magnesium, iron, aluminum, calcium. ~aid impurities are precipitated in known manner by a~ addition of alkali and/or sodium carbonate and the precipitates are removed.
A concentrated sodium carbonate solution is then added to tne filtra~e so that the lithium car~onate is precipi-tated under conditions known per se. The precipitate is recovered, washed a~d dried. ~n a special embodiment of the invention only 60 to 85 ~/0 ra~her than all of the lithium carbonate in the filtrate are precipitated and the mother liquor is recycled to tne leacning stage.
~29726S
lithium carbonate of high purity is thus recovered~
The process in accordance with the invention can be carried out to special advantage in co~junction with a continuous leaching process because this will permit lithium carbonate to be produced in a particularly economical manner. The process in accordance with the invention particularly distinguishes in that it can be used not only to prooess lithium ore concentrates in the usual manner but also to process so-called raw ores consisting of lithium ores which have not been processed before and this can be effected economically and with a high yieldD Such ores particularly include alpha-spodumene, petalite and lepidolite. ~or in~tance, it is possible to process an alpha-spodumene having the following approximate composition:
~i2o 3.3 to 401 ~ by -~veight SiO2 60 to 70 ,o "
r~123 15 t 25 j Fe203 0-3 tO 0.6 ~G~
CaO 0005 tO 0.2 1 K20 002 tO 0~5 1 Na20 3 to 0.8 ~
The invention will be described by way of example and more in detail with ~ference to the drawing and to the ~xample~
~ igure 1 is a simplified flo.v diagra~
illustrating the process in accordance with the invention.
~297265 Figure 2 is a diagrammatic represent~-,tion of a reactor with a circulating ~hidized bed.
~ e feed and fuel are supplied through res-pective lances 5 and 6 to a circulation system consisting of a fluidized bed reactor 1, a cyclone separator 2 and a recycle line 3. A product stream at the same rate as the feed is withdrawn through line 24 and delivered to the fluidized bed cooler 17, in which the product stream first flows through four cooling stages to deliver a sub-stantial part of its heat by an indirect heat exchange to oxygen-containing gases which flow countercurrently to the solids. Said gases are then supplied as a dustfree fluidizing gas to the fluidized bed reactor 1. The solids are then cooled further in subsequent cooling chambers, which are cooled, e.g., with water. The product stream is subsequently discharged through line 19. ~he fluidized bed cooler 17 is supplied with an oxygen-containing fluidizing gas, which takes up a substantial further quantity of heat from the solids and after a dust-collecting treatment in the separator 20 is supp]ied in line 21 as a secondary gas to the fluidized bed reactor 1.
The exhaust gas from the fluidized bed reactor 1 flows throu~b line 4 to the waste heat boiler or heat exchanæer 11 and subsequently to an electrostatic preci-pitator 14 for a dust-collecting treatment and is dis-charged through line 15 into the chimney.
Lines 25 and 26 serve to supply fluidizing gas or entraining gasO
~,s7~is Example A pilot reactor for a single-stage combustion was supplied through lance 5 at a rate of 5007 kg/h with alpha-spodumene which had the above-mehtioned composition and had been ground to a particle size 1 mm (average particle diameter dp50 = 377 ~m) and was supplied through lance 6 with light fuel oil at a rate of 22 kg/ho Oxygen-enriched air (215 sm3/h air and 15 sm3/h oxygen) was supplied only as a fluidizing gas through line 1~ .
A temperature of 1070 C was obtained in the circulation sys~em consisting of the fluidized bed reactor 1, the cyclone separator 2 and the recycle line 3. The pressure drop across tbe fluidized bed reactor amounted to 40 millibars.
Solids (dp50 = 252 ~m) at a rate of 47~1 kg~h were withdr~wn through line 24. Solids (dp50 = 6.0 ~m) at a rate of 4050 k,~/h were discharged through line 4.
'~he solids were subsequently recovered.
The recovered solids were combined and subjected to conventional afterprocessing. ~he lithium introduced with the alpha-spodumene was recovered with a total yield of 52 to 93 ~ by ~eight.
~ranslation of the Inscriptions on Figure 1 of the Drawings alpha-Spodumen Reaktor mit zirkulO Wirbelschicht reactor with circulating fluidized bed beta-Spodumen beta-spodumene Mischstufe mixing stage . . .
concO H2S04 concentrated H2S04 Roststufe roasting stage Laugung leaching Na2S04-Abtrennung separation of Na2S04 Ruckstand (Silikat) residue (silicate) Filtration filtration Fallung Verunreinigung precipitation of impurities Alkali, Soda alkali, sodium carbonate Verunreinigungen Mg, Ca, Al, Fe impurities Mg, Ca, Al, Fe Filtration filtration Li2C03-Fàllung . precipitation of Li2C03 conc. Sodalosung concentrated sodium carbonate solution FiltratioD filtration Li/Na-Sulfat-Losung Li-Na sulfate solution Li2C3 Li2C3
It is known that lithium ores or lithium ore concentrates, such as spodumene or petalite, can be subjected to a thermal treatment, which is usually described as decrepitation, and results in a state in which the material can be solubilized by an acid. By the decrepitation, which is usually effected in a rotary kiln at about 1000 to 1100C, spodumene is transformed from the alpha modification to the beta modification and petalite is transformed to beta-spodumene and quartz.
/
/
, / .
~2g~2fiS
After the decrepitation the beta-spodumene may be ground further and is treated with concentrated sulfuric acid used in a surplus with respect to the lithium content of the ore. The mixture which is ~irtually as moist as earth is charged into a suitable furnace, such as a rotary kiln, and is solubilized therein at temperatures from about 250 to 300 C. When tne lithium content of the ore is in the form of soluble lithium sulfate, the reaction mixture is charged into suitable l-achin~ tanks, in which the lithium sulfate is leached out by means of hot water, w!lich is usually conducted in a countercurrent to the re~ction mixture~ Sodium carbon_te is added to tne extract in a quantity Nhich is sufficient for the adjustment of a pH value of about 6 to 7 so that impurities such as calcium, magnesium, iron and aluminum will be precipitated as insoluble compounds~ When the residue has been separated, a ~ncentrated solution of lithium sulfate is available, which is treated with a concentrated sodium carbonate solution at elevated temperatures so ~at lithium carbonate is precipitated, which is subsequently recovered.
It is also known that the decrepitation can be effected in furnaces other than a rotary kiln, e.gO, in muffle furnaces and in fluidized bed reactors (U.S.
Patent 3~017~243)o The fact that rotary l~ilns, multiple-hearth furnaces or muLffle furnaces can be used just a~
fluidized bed reactors permits of th~ conclusion that it has been believed that the nature of the treatment and the manner in which the ground ore is heated to the transformation temperature are not significant (U.S. Patent 2,516,109).
It is an object of the invention to permit the production of ]ithium carbonate from decrepitable lithium ores or ore concentrates in a process which ensures that the lithium will be virtually completely extractable.
According to the present invention there is provided a process of producing lithium carbonate from lithium-containillg decrepitable ores or ore concentrates, wherein the ore or ore concentrate is transformed at temperatures from about 800 to 1100C to a form from which the lithium component can be leached, the lithium in the decrepitated material is converted to lithium sulfate by a solubilizing roasting treatment with a surplus of concentrated sulfuric acid, the roasted product is leached with water and the extract is filtered from the residue, precipitated impurities are removed from the filtrate and the latter is subsequently treated with a concentrated sodium carbonate solution to effect a precipitation of lithium carbonate, which is recovered, characterized in that the disintegrated ore or ore concentrate is transformed to a leachable form in that it is subjected to a shock heating to at least 800C as it is introduced into a circulating fluidized bed.
The ore or ore concentrate is preferably shock-heated to a temperature which is not in excess of 1300 C.
The term shock heating means that ore or ore concentrate which has not been thermally treated before is charged into a circulating fluidized bed and the temperature of said bed is controlled by a combustion of gaseous, liquid or solid fuel, such as coal. Any fuel may be used which will not adversely affect the subsequent treatments.
Within the scope of the invention the decrepiting thermal treatment is effected in an expanded fluidized bed, which is basically known per se. From an "orthodox"
fluidi~ed bed, in which a dense phase is separated by a distinct stepindensity from the ove~
12972~S
an expanded fluidized bed differs in that it comprises states of distribution having no defined boundary layers.
There is ~o step in density between a dense phase and an overlying gas space but the solids concentration in the reactor decreases gradually from bottom to top.
On principle, the oxygen-containing gases required for the combustion can be added in one s~age. But it will be particularly desirable to supply the oxygen-containing gas required for the combustion process to the fluidized bed in two partial streams on different levels. That mode of operation will result in a SOI`t combustion in two stages so that there will be no local overheating and the formation of NOx gases will be suppres 5 ed.
In case of a multista~e combustion, vi~u-ally any gas which will not adversely affect the nature of the exhaust gas can be used as a fluidized gas. E~r instance, the fluidizing gas may consist of a gas which is non-reactive under the conditions existing in the circulating fluidized bed, e.g., of a recycled flue gas (exhaust gas), nitrogen and water vapor. But for an intensification of the combustion gas it will be desir-able to use a fluidizlng gas consisting of a partial stream of the ox~gen-containing gases to be supplied.
~ t is apparent that in a preferred embodiment the process may be carried out in the following ways:
~29~265 10 The fluidizing gas consists of a gas which is inert under -the conditions in the fluidized bed. In that case the oxygen-containing combustion gas is supplied as a secondary gas on at least two spaced apart levels.
20 An oxygen-containing gas is used also as a fluidizing gasO In that case it will be sufficient to suppl~y secondary gas on one level although in that case the secondary gas may also be supplied on a plurality of levels.
It will be desirable to provide a plurality of inlets for the secondary gas on each level on wnich said gas is suppliedO The volume ratio of fluidizing gas to second-ary ~as should be in the range from 1:20 to ~
l'he secondary gas is suitably supplied on a level ~ihich is spaced above the inlet for the fluidizing ~as at least 1 meter and up to 3~j~ of the overall hei~ht of ~he fluidized bed reactor. If the second~r~ gas is supplied on a plurality of levels, the reference to 3~/o is appli-~able to the uppermost inlet level for the secondary gas.
A supply on that level will provide for a sufficiently l~rge space for the first combustion st~ge for an almost complete reaction between combustible constituents and oxy~en-containing gas - whether it is sup~lied on a lower level as a fluidizing or secondary gas - and -~ill permit the provision of a sufficiently large zone for a complete combustion in the upper reaction space above the secondary 129~26S
gas inlet level.
The gas velocities maintained in the fluidized bed reactor above the secondary gas inlet may amount, as a rule, to more than 5 m/sec. and up to 15 m/sec..
The ratio of the diameter to the height of the fluidized-bed reactor should be selected to provide for gas residence times from 0.5 to 8.0 sec., preferably 1 to 4 seconds.
The mean suspension density to be maintained in the fluidized bed may vary within wide limits and may be as high as 100 kg/m3. To minimize the pressure drop, a mean suspension density in the range from 10 to 40 kg/m3 should be maintained above the secondar~ gas inlet level.
The definition of the operating conditions by the Froude ~nd ~rchimedes numbers results in the follow-ing ranges:
001 _ 3/4 x Fr2 x ~g --- ~ 10 ~ Pk Pg or 0.01 ~ Ar ~ 100 wherein Ar = k ~k ~g x Fr2 =
and ~97~6S
u = the relative gas velocity in m/sec.
Ar = the Archimedes number Fr = the Froude number ~g = density of the ga~ in kg/m3 k = the density of the solid particle in kg/m3 dk = the diameter of the spherical particls in m = the kinematic viscosity in m2/sec.
g = the acceleration due to gravity in m/sec.2 After the thermal treatment in the fluidized bed the product is usually cooled, suitably in a fluidized bed cooler, which may comprise a plurality of stagesc ~he sensible heat of the product may be used to generate steam and/or to heat the oxygen-containing gas which is to be supplied to the circulating fluid~zed bed.
~ he exhaust gases from the circulating fluidized bed are cooled in a waste heat boiler for a generation of steam, which may be used, e.g., in the subsequent leaching stages. Alternatively, if the su~se quent roasting is effected in a directly heated rotary kiln, the exhaust gases may be used to heat such kiln.
The invention permits of a high through-put rate and permits those components from which the lithium component can be leached out to be transformed to a particulerly highly reactive formO Besides, a material ~29726S
is made a~ailable which has a large surface area and in which the lithium ions are particularly easily and complete-ly accessible for chemical reactions. dn additional acti-~ation can be effected in that the thermal treatment in the fluidized bed reactor is effected in the presence of additives wnich are known per see and influence the modification.
In the process in accordance with the invention it is not critical to use an ore or ore concen-trate having a particularly small particle size. It is generally sufficient to effect a disin~egration to a particle size from 1 to lO mmO Smaller particle sizes, e.g., below 10CO!um, .~ill further increase the heating-up rateO
The decrepited material is subsequently solubilized in Xnown manner in a homogeneous mixture with sulfuric acid. Sulfuric acid having a concentration from 90 to 94 ~ is usually employed for that purpose in a surplus from 30 to lO0 ~ with respect to tne litnium content of the oreO In the process in accordance with the present invention t`ne homogeneous mixture of heat-treated ore or ore concen-trate an~ concentrated sulfuric acid is solubilized by a supp^-ly of heat at a temperature from 250 to 320 C. ~hat solubi-lizing roasting treatment is desirably ef ected in a rotary Xiln, which may be directly or indirectly heatedO An indirect heatin~ nill afford the special advantage tnat the surplus free sull'uric acid which has been expelled during the ~297Z6S
roastiug treatment can be directly re-u~ed and can be directly recycled to the solubilizing stageO Adirect heating will afford the advantage that the exhaust gases from the circulating fluidized bed can be used and that the expelled sulfuric acid can also be re-used.
For a recovery of the soluble lithium sul fate now contained in the roasted product, the latter is leached in known manner in a plurality of stirred vessels, which are connected in series and in which the roasted product and water flow in countercurrent streamsO After the leaching t~e residues, which mainly contain silicates, are separated. In accordance with the invention the process parameters are so selected that the resulting solution contains lithium sulfate in a concentration from about 200 to 250/1 Li2S04.
In addition to lithium sulfate and sodium sulfate, the filtrate may contain other impurities, such as magnesium, iron, aluminum, calcium. ~aid impurities are precipitated in known manner by a~ addition of alkali and/or sodium carbonate and the precipitates are removed.
A concentrated sodium carbonate solution is then added to tne filtra~e so that the lithium car~onate is precipi-tated under conditions known per se. The precipitate is recovered, washed a~d dried. ~n a special embodiment of the invention only 60 to 85 ~/0 ra~her than all of the lithium carbonate in the filtrate are precipitated and the mother liquor is recycled to tne leacning stage.
~29726S
lithium carbonate of high purity is thus recovered~
The process in accordance with the invention can be carried out to special advantage in co~junction with a continuous leaching process because this will permit lithium carbonate to be produced in a particularly economical manner. The process in accordance with the invention particularly distinguishes in that it can be used not only to prooess lithium ore concentrates in the usual manner but also to process so-called raw ores consisting of lithium ores which have not been processed before and this can be effected economically and with a high yieldD Such ores particularly include alpha-spodumene, petalite and lepidolite. ~or in~tance, it is possible to process an alpha-spodumene having the following approximate composition:
~i2o 3.3 to 401 ~ by -~veight SiO2 60 to 70 ,o "
r~123 15 t 25 j Fe203 0-3 tO 0.6 ~G~
CaO 0005 tO 0.2 1 K20 002 tO 0~5 1 Na20 3 to 0.8 ~
The invention will be described by way of example and more in detail with ~ference to the drawing and to the ~xample~
~ igure 1 is a simplified flo.v diagra~
illustrating the process in accordance with the invention.
~297265 Figure 2 is a diagrammatic represent~-,tion of a reactor with a circulating ~hidized bed.
~ e feed and fuel are supplied through res-pective lances 5 and 6 to a circulation system consisting of a fluidized bed reactor 1, a cyclone separator 2 and a recycle line 3. A product stream at the same rate as the feed is withdrawn through line 24 and delivered to the fluidized bed cooler 17, in which the product stream first flows through four cooling stages to deliver a sub-stantial part of its heat by an indirect heat exchange to oxygen-containing gases which flow countercurrently to the solids. Said gases are then supplied as a dustfree fluidizing gas to the fluidized bed reactor 1. The solids are then cooled further in subsequent cooling chambers, which are cooled, e.g., with water. The product stream is subsequently discharged through line 19. ~he fluidized bed cooler 17 is supplied with an oxygen-containing fluidizing gas, which takes up a substantial further quantity of heat from the solids and after a dust-collecting treatment in the separator 20 is supp]ied in line 21 as a secondary gas to the fluidized bed reactor 1.
The exhaust gas from the fluidized bed reactor 1 flows throu~b line 4 to the waste heat boiler or heat exchanæer 11 and subsequently to an electrostatic preci-pitator 14 for a dust-collecting treatment and is dis-charged through line 15 into the chimney.
Lines 25 and 26 serve to supply fluidizing gas or entraining gasO
~,s7~is Example A pilot reactor for a single-stage combustion was supplied through lance 5 at a rate of 5007 kg/h with alpha-spodumene which had the above-mehtioned composition and had been ground to a particle size 1 mm (average particle diameter dp50 = 377 ~m) and was supplied through lance 6 with light fuel oil at a rate of 22 kg/ho Oxygen-enriched air (215 sm3/h air and 15 sm3/h oxygen) was supplied only as a fluidizing gas through line 1~ .
A temperature of 1070 C was obtained in the circulation sys~em consisting of the fluidized bed reactor 1, the cyclone separator 2 and the recycle line 3. The pressure drop across tbe fluidized bed reactor amounted to 40 millibars.
Solids (dp50 = 252 ~m) at a rate of 47~1 kg~h were withdr~wn through line 24. Solids (dp50 = 6.0 ~m) at a rate of 4050 k,~/h were discharged through line 4.
'~he solids were subsequently recovered.
The recovered solids were combined and subjected to conventional afterprocessing. ~he lithium introduced with the alpha-spodumene was recovered with a total yield of 52 to 93 ~ by ~eight.
~ranslation of the Inscriptions on Figure 1 of the Drawings alpha-Spodumen Reaktor mit zirkulO Wirbelschicht reactor with circulating fluidized bed beta-Spodumen beta-spodumene Mischstufe mixing stage . . .
concO H2S04 concentrated H2S04 Roststufe roasting stage Laugung leaching Na2S04-Abtrennung separation of Na2S04 Ruckstand (Silikat) residue (silicate) Filtration filtration Fallung Verunreinigung precipitation of impurities Alkali, Soda alkali, sodium carbonate Verunreinigungen Mg, Ca, Al, Fe impurities Mg, Ca, Al, Fe Filtration filtration Li2C03-Fàllung . precipitation of Li2C03 conc. Sodalosung concentrated sodium carbonate solution FiltratioD filtration Li/Na-Sulfat-Losung Li-Na sulfate solution Li2C3 Li2C3
Claims (12)
1. A process of producing lithium carbonate from lithium-containing decrepitable ores or ore concentrates, wherein the ore or ore concentrate is transformed at temperatures from about 800 to 1100°C to a form from which the lithium component can be leached, the lithium in the decrepitated material is converted to lithium sulfate by a solubilizing roasting treatment with a surplus of concentrated sulfuric acid, the roasted product is leached with water and the extract is filtered from the residue, precipitated impurities are removed from the filtrate and the latter is subsequently treated with a concentrated sodium carbonate solution to effect a precipitation of lithium carbonate, which is recovered, characterized in that the disintegrated ore or ore concentrate is transformed to a leachable form in that it is subjected to a shock heating to at least 800°C as it is introduced into a circulating fluidized bed.
2. A process according to claim 1, characterized in that the ore or ore concentrate is shock-heated to a temperature not in excess of 1300°C.
3. A process according to claim 2, characterized in that the roasting treatment with sulfuric acid is effected by a direct or indirect supply of heat in a rotary kiln.
4. A process according to claim 3, characterized in that the free sulfuric acid which has been expelled during the roasting treatment is re-used for a solubilizing treatment.
5. A process according to claim 4, characterized in that the roasted product is leached in a countercurrent operation and a concentration of 200 to 250 g/l Li2SO4 is maintained in the extract.
6. A process according to claim 5, characterized in that only 60 to 85% of the lithium carbonate are precipitated from the solution and the mother liquor is recycled to the leaching stage.
7. A process according to claim 1, 4 or 6, for processing of alpha-spodumene, petalite and lepidolite.
8. A process according to claim 1, characterized in that the roasting treatment with sulfuric acid is effected by a direct or indirect supply of heat in a rotary kiln.
9. A process according to claim 1, characterized in that the free sulfuric acid which has been expelled during the roasting treatment is re-used for a solubilizing treatment.
10. A process according to claim 1, 8 or 9 characterized in that the roasted product is leached in a countercurrent operation and a concentration of 200 to 250 g/l Li2SO4 is maintained in the extract.
11. A process according to claim 1, characterized in that only 60 to 85% of the lithium carbonate are precipitated from the solution and the mother liquor is recycled to the leaching stage.
12. A process according to claim 8, 9 or 11 for processing of alpha-spodumene, petalite and lepidolite.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19863622105 DE3622105A1 (en) | 1986-07-02 | 1986-07-02 | Process for winning lithium carbonate |
| DEP3622105.8 | 1986-07-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1297265C true CA1297265C (en) | 1992-03-17 |
Family
ID=6304169
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000537850A Expired - Lifetime CA1297265C (en) | 1986-07-02 | 1987-05-25 | Process of producing lithium carbonate |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU601990B2 (en) |
| CA (1) | CA1297265C (en) |
| DE (1) | DE3622105A1 (en) |
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-
1986
- 1986-07-02 DE DE19863622105 patent/DE3622105A1/en not_active Withdrawn
-
1987
- 1987-05-25 CA CA000537850A patent/CA1297265C/en not_active Expired - Lifetime
- 1987-07-01 AU AU74995/87A patent/AU601990B2/en not_active Ceased
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Also Published As
| Publication number | Publication date |
|---|---|
| AU601990B2 (en) | 1990-09-27 |
| DE3622105A1 (en) | 1988-01-07 |
| AU7499587A (en) | 1988-01-07 |
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