DE1093783B - Process for the processing of lithium ores - Google Patents

Description

Process for the processing of lithium ores The invention relates refer to a process for the processing of lithium ores, in particular a- and f-spodumene, by roasting in order to obtain lithium and other alkali salts with a high degree of purity.

It is known to use ores containing lithium in the presence of calcium carbonate to roast, then leach the roasted product with water and the resulting To treat crude lithium carbonate solution using hydrochloric acid and the lithium chloride after various intermediate purification stages. At a Another known method is the lithium ore with sulfuric acid under roasting conditions treated, whereby the sulfate forms, and this is as an aqueous solution by Leaching obtained with water. Another method involves using potassium sulfate to fill the ore roasted to form lithium sulfate, and this is also leached won. The lithium sulfate obtained by this process is then through Treating with sodium carbonate is converted to lithium carbonate, and it becomes after extensive intermediate purification stages of technically pure lithium carbonate obtain.

From U.S. Patents 2,627,452 and 2,726,138 it is known Lithium ores, especially a- and ß-spodumene, by roasting with calcium carbonate, Treat sand and calcium chloride at around 1100 to 1200 ° C, using a cement clinker accumulates and chlorides of lithium, sodium and potassium escape in gaseous form, which separated and dissolved in water. The chloride solutions thus obtained are evaporated, the separated chlorides become potassium and sodium chloride separated, and from the remaining concentrated lithium salt solution only becomes technically pure lithium chloride obtained by extraction.

If in this way you also get relatively pure lithium chloride comes, these known processes leave much to be desired.

Lithium is from preparative organic chemistry, be it as a metal or be it as salt, indispensable, and even in some large-scale Proceedings can no longer be dispensed with. With this procedure is but it is essential that the purity of the lithium compounds used or the Lithium itself goes far beyond a technically pure quality. Using the However, such purity cannot be achieved in the known processes described last.

In addition, lithium ores are relatively rare in nature and usually only contain small amounts of lithium. In the previously known ones described above Processes now lead to considerable losses in lithium compounds by that in the separated sodium and potassium salts as well as in the: mother liquors Lithium compounds are still present in this way of the industry are lost with their increasing lithium demand.

This increasing industrial demand for lithium now makes it necessary to not to let these per se small amounts get lost.

It is therefore a primary object of the present invention to work up methods to show that make it possible to use even the smallest amounts of lithium salts of lithium manufacturing industry.

Based on the process of the US patents mentioned, the present invention therefore relates to a process for processing lithium ores, in particular a- or fl-spodumene, in which the lithium ores are roasted with calcium carbonate, sand and calcium chloride at about 1100 to 1200 ° C , separates the cement clinker that has formed and separates the chloride vapors that escape during roasting and dissolves them in water, whereupon the chloride solutions are worked up to lithium, sodium and potassium compounds. The process according to the invention is carried out in such a way that the chloride solutions thus obtained are admixed with the mixture of sodium chloride and lithium carbonate deposited in a subsequent process stage, and solid sodium chloride is separated from the resulting slurry at a temperature of about 25 to 30 ° C, from which Mother liquor precipitates by adding sodium carbonate and heating to 60 to 100 ° C lithium carbonate, the residual solution remaining after its separation evaporates to 40 to 65 "/ a solids and at 90 to 100 ° C the mixture of sodium chloride and lithium carbonate, with which the chloride solutions obtained by washing out the vapors are added, and potassium chloride is precipitated from the residual solution by cooling to about 0 to 5 ° C.

In a particular embodiment, the method according to the invention should be carried out so that the remaining after separation of the potassium chloride Solution for washing out the chlorides from the vapors escaping from the cement kiln is used.

The method according to the invention differs from the previously known methods mainly in that the lithium is precipitated as carbonate from the solution of the chlorides in the heat and that the remaining mother liquor, which contains Na Cl, K Cl and Li C 03, is worked up by evaporating to 40 to 65% solids so that crude sodium chloride precipitates out together with the lithium carbonate at 90 to 100 ° C. This mixture of Na Cl and Li CO is then separated off and isolated from the mother liquor K C1 by cooling to about 0 to 5 ° C. Even if it is known per se that lithium can be precipitated as carbonate and that Na Cl and K Cl can be separated due to their different solubilities, one would have expected that the solutions remaining after the separation of the lithium carbonate, in addition to Na Cl and K C1 would only contain a little lithium carbonate and that with regard to the excretion of Na Cl or K C1 they would not behave much differently than solutions containing only Na Cl and K C1, and that the last traces of lithium carbonate could be extracted by recrystallization . The present invention now provides a further novel measure at this point, in which the NaCl contaminated by lithium salt is slurried in the chloride solution obtained by washing out the vapors leaving the cement kiln, whereby pure NaCl can be obtained and any loss of lithium can be avoided . Given the composition of the chloride solution and in view of the fact that this is not a matter of recrystallization at all, this result is to be rated as surprising. In addition, before the treatment with sodium carbonate, solid, pure sodium chloride is obtained from the slurry at a temperature of approximately 25 to 30 ° C., which corresponds to approximately room temperature. Since pure NaCl is to be deposited at room temperature and potassium chloride at 0 to 5 ° C., the temperature of the melting ice, temperature ranges are used which can easily be maintained without special technical measures. Together with the avoidance of any lithium loss, the present method thus achieves a combination of procedural criteria to achieve a maximum of yield and purity of the substances to be obtained. Example 1 A typical pegmatite ore from Kings Mountain North Carolina has the following components in percent by weight: 32 to 36% feldspar, 28 to 34% quartz, 26 to 32% spodumene, 4 to 6% mica, 0.03% casserite (tin ore) and 0.01 to 0.03% beryl, and these materials have the following mean analytical values: Spodu- Feldspar Quartz Glim- Zu- men mer together Si 02. . . . . . . . . 61.29 65.2 98.5 61.9 84.00 A1203 ........ 30.85 22.6 0.4 31.1 15.02 Fairy 03. . . . . . . 0.20 0.07 0.05 0.3 0.09 CaO. . . . . . . . 0.38 0.42 0.2 0.26 Mg0 ....... 0.26 0.18 0.2 0.07 Lit O ........ 6.84 0.32 0.4 1.92 Nag O. . . . . . . . 0.61 6.51 0.62 2.43 K2 0 ......... 0.82 4.32 6.10 1.92 This ore is broken into coarse pieces with a particle size of about 2.5 to 5.1 cm in diameter and then the spodumene is separated therefrom, e.g. B. by a sink or flotation process. The specific weights of the constituents of the pegmatite ore are as follows: Quartz. . . . . . . . . . . . . . . . . . . . 2.65 to 2.66 Beryl. . . . . . . . . . . . . . . . . . . . . 2.68 to 2.76 Feldspar ................... 2.70 Mica. . . . . . . . . . . . . . . . . . 2.80 to 2.90 Spodumene ................. 3.1 to 3.2 Casserit ................... 6.8 to 7.0 and the first four can be separated by "#" mixing with an aqueous ferrosilicon slurry having a flotation density of about 2.90, thereby floating these materials from the spodumene and casserite, the latter settling to the bottom. In this process the average lithium content of the concentrate is approximately three times that of the raw ore and the use of such a concentrate therefore markedly increases the lithium salt output per roasting stage. Likewise, the yield of lithium salt increases in relation to the amount of calcium chloride used.

The spodumene in this concentrate is in the hard a-form, and this is heated to a temperature of 900 to 1100 ° C until it becomes softer ß-form is converted, e.g. B. by roasting in an ordinary kiln with powdered Coal and air.

The resulting crude f-spodumene can then be passed through a magnetic Separators are led, with any iron oxide present, if any white Type of cement clinker desired is removed. It can also be a light one Are subjected to grinding to remove coarse pieces, and this type of work-up can precede the iron oxide deposition.

The raw ß-Spodutnen is done with sand, calcium carbonate and calcium chloride mixed. The sand and calcium carbonate, e.g. B. well-ground limestone added to modify the composition of the ore residue to make a portland cement clinker with good properties is made possible, and the calcium carbonate supports this, by making the reaction mixture remain in a porous state and not Baked on the walls of the kiln. It is preferred to have these ingredients before Mix together before roasting to achieve a good touch between them. This mixing can be done, for example, by wet milling brought about will. The resulting mixture has the following composition: 100 parts of ß-spodumene, 64 parts of sand, 590 parts of limestone and 29.5 parts of calcium chloride (as 40% aqueous Solution).

This mixture is passed through a cement rotary roasting furnace at approximately 1100 passed through up to 1200 ° C. Higher temperatures should be avoided because they tend to melt the mixture, causing that it is not porous enough and therefore not reactive enough, and lower, temperatures, although still effective, are less desirable in that they are none Ensure complete conversion and no volatilization of the lithium compound. Theoretically, the gaseous material developed should contain: 19 parts Lithium chloride, 1.3 parts sodium chloride and 1.0 part potassium chloride, and at the In practice, these amounts are approximately 90 to 95%.

The Portland cement clinker obtained as a by-product has the following composition: S102. . . . . . . . 23.00o / 0 A1203 . . . . . . . 6.220 / 0 CAO. . . . . . . . 66,600 / 0 Fe20s ....... 0.044 ° / 0 Mg 0 . . . . . . . . 0.03 0/0 (neglecting of Mg 0 in lime). This is a high quality cement clinker with a low magnesium and iron content. It becomes powdered cement in the usual way, e.g. B. in a ball mill converted.

The gaseous mixture that escapes from the filling end of the kiln is preferably passed through a heat exchanger, e.g. B. a waste heat boiler, to recover as much heat as possible, which may be used for other purposes, e.g. B. to Generation of steam. At this stage of the process, the gaseous flow of dust, and this contains most of the volatilized Alkali chlorides of the gaseous mixture; this dust is mixed and stirred with water or the mother liquor from the potassium chloride recovery stage, and essentially all soluble chlorides in the dust are thereby dissolved. It will be sufficient Water is used to keep the slurry in liquid form and keep it forming of lumps to prevent entrapment and retention of substantial quantities to avoid the alkali chlorides. This slurry is filtered or centrifuged, and the separated solid matter or filter cake becomes the cement kiln returned or introduced in the next paragraph. That way will eventually the entire alkali chloride content of the dust is recovered as chloride.

On the other hand, the separated dust can go directly to the cement kiln be returned for re-treatment, ultimately resulting in losses in it Any alkali chlorides present are switched off.

After passing through the heat exchanger, the gaseous Mixture in contact with water or the filtrate or mother liquor from the dust leaching stage brought to recover any alkali salts contained therein, and the remainder Gas is discarded; the method just described is preferably carried out according to the countercurrent principle in a spray or sprinkling storm.

On the other hand, the gaseous mixture can be broken down into its solid components and their gas fractions are separated according to the Cottrell process, preferably according to Passing through a heat exchanger, or instead of passing through through a heat exchanger. The escaping gas can be washed or discarded and the alkali chlorides are made from the solid components as described above won.

Referring to the drawing, the ore is fed through line 1 into mill 2, in which it is carefully ground, and then it is fed through line 3 to separator 4, from which feldspar, quartz, mica, etc., through line 5 are removed, and the enriched α-spodumene is led therefrom through the line 6 to the kiln 7, in which it is converted to β-spodumene by heating to a temperature of 900 to 1000 ° C. with fuel and air introduced through line 8. Then it is fed through line 9 to the magnetic separator 10, from which the iron oxide is removed through line 11 , and the remaining material is brought through line 12 to the mill 13, in which it is finely ground and then through line 14 to the mixer 15 is performed. There it is mixed with sand, limestone and calcium chloride as a 40% aqueous solution, the latter constituents being fed through line 16. Through the line 17, separated solid components or filter cakes can be returned to it in the circuit. The resulting mixture is fed through line 18 to the roasting furnace 19, in which it is roasted at a temperature of 1000 to 1200 ° C. with fuel and air introduced through line 20. The Portland cement clinker produced as a by-product is removed through line 21, and the evolved gaseous mixture is conducted therefrom through line 22 to the waste heat boiler 23, and the dust precipitated therein is conducted therefrom through line 24 to the extraction plant 25, in which it is carried along the line 26 supplied water or with the supplied through the line 27, circulated mother liquor or both is brought into contact, and the resulting mixture is brought through the line 28 to the separator 29 (filter or centrifugal), in which the solids separated therefrom and returned through line 17 to mixer 15. The filtrate or the liquid therefrom is brought via line 30 to the scrubber 31, in which it is brought into contact with gases supplied from the waste heat boiler through line 32, and the washed gases are discharged through line 33 and discarded. The resulting chloride solution is brought through line 34 to mixer 35, in which it is mixed with a mixture of sodium chloride and lithium carbonate circulated through line 36 and, if necessary, with mother liquor fed in through line 27a. The resulting mixture is passed through line 37 to the separation device 38 (filter or centrifuge), in which essentially pure, solid sodium chloride is separated off at 25 to 30.degree. C. and removed through line 39. The resulting filtrate or mother liquor is fed therefrom through line 40 to mixer 41, in which it is mixed with anhydrous sodium carbonate fed through line 42 and heated to a temperature of 60 to 100 ° C, e.g. B. 100 ° C, is brought, and the resulting mixture is passed through line 43 to the separator 44 (filter or centrifugal), in which lithium carbonate is separated as the end product and with high purity at this temperature and discharged through line 45.

The resulting filtrate or mother liquor is passed through line 46 to evaporator 47, in which it is reduced to a concentration of about 550 fo of total solids, e.g. B. by removing 100 parts of water, is concentrated, wherein the removed water can be drawn off through line 48 and discarded (or can be circulated to the extraction plant by feeding in line 27, not shown). The resulting concentrated mother liquor is passed therefrom through line 49 to separator 50 (filter or centrifuge) in which crude, solid sodium chloride containing a small amount of lithium carbonate is separated at about 100 ° C. and therefrom through line 36 to the mixer 35 is returned. The resulting filtrate or the mother liquor is brought therefrom through the line 51 to the cooler 52, in which it is cooled to temperatures of 0 to 5 ° C, and from there is passed through the line 53 to the separator 54 (filter or centrifuge), in which essentially pure potassium chloride is separated therefrom as a by-product at this temperature and removed through line 55. The resulting filtrate or the mother liquor is returned therefrom through line 27 to the extraction vessel 25 or, if necessary, through line 27a to the mixer 35.

For technical purposes it is preferred to run the process continuously Operate in a manner recovering essentially all of the alkali metal constituents of the ore, as lithium carbonate of high purity and as fairly pure By-products sodium chloride and potassium chloride, which are essentially free of lithium salts and with the extraction of valuable Portland cement clinker. Example 2 The procedure Example 1 is repeated with the difference that the pegmatite ore is ground and is processed directly in the cement kiln, the ore with as much sand as Calcium carbonate and calcium chloride (e.g. as a 40% aqueous solution) are mixed, to obtain cement clinker having essentially the same composition as in example 1 have.

During the roasting process, the alkali metals present become their chlorides converted, which escape in gaseous form. That added as calcium chloride Calcium is converted to oxide, which remains in the cement clinker. Of the Limestone is converted to calcium oxide and carbon dioxide and calcium aluminates and silicates and aluminum silicates are also formed.

Results comparable to the previous ones are made possible by numerous modifications, such as B. the following obtained. The ore used can be any ore containing an appropriate lithium content, e.g. B .: Mineral lithium content in percent by weight Spodumene. . . . . . . . . . . . . . . . . . ... 2 to 3 Lepidolite. . . . . . . . . . . . . . . . . . . . . . 2 to 4 Amblygonite. . . . . . . . . . . . . . . . . . . . 8 to 9 Triphylite. . . . . . . . . . . . . . . . . . . . . . 2 to 6 Petalit ............. .......... 2 to 4 Zinnwaldite. . . . . . . . . . . . . . . . . . . . 2 to 3 The lithium content thereof can be converted to lithium chloride by roasting with calcium chloride and the desired chloride escapes therefrom in a gaseous state along with any other alkali chloride present.

The fuel can be coal or oil or natural gas or the like, and the air can be enriched with oxygen.

The crude, aqueous lithium chloride solution can contain about 2 to about 44% lithium chloride, preferably 15 to 30%, at room temperature. The separation of the solid, essentially pure sodium chloride is carried out at a temperature of approximately 25 to 30 ° C. The deposition of the lithium carbonate as the end product with high purity is carried out at a temperature in the range from 60 to 100.degree. C., preferably 95 to 100.degree. The filtrate or mother liquor resulting therefrom is concentrated to a total solids content of 40 to 65%, preferably 50 to 60%. The concentration is preferably selected such that substantially no precipitates of potassium chloride from the solution at 90 to 100 'C. The crude sodium chloride is separated from the concentrated --Mutterlauge at a temperature of 90 to 100 'C, preferably about 100 ° C. The essentially pure potassium chloride is separated from the resulting mother liquor or the filtrate at a temperature of 0 to 5 ° C, preferably 0 ° C.

The amount of calcium chloride present in the roast mixture is at least stoichiometrically equal to the total alkali present in the ore and preferably in about a 5 to 158 percent excess. The amount of 2 "sodium carbonate needed to is added to the aqueous chloride solution is at least stoichiometrically the same the lithium present therein and preferably in about 2 to 50% Excess.

The mixture to be roasted in the cement kiln should be finely ground (e.g. sieved through a DIN sieve 0.075 mm clear mesh size = 80 meshes per cm) and a clinker that has an average composition in percent by weight from 4 to 11 0 / a aluminum oxide and 19 to 26% silicon oxide and in which the remainder consists essentially only of calcium oxide, with the exception of only small amounts of magnesium oxide and iron oxide, etc. The weight ratio from silicon oxide to the sum of aluminum oxide and iron oxide in it lies in that Range from 1.7 to 2.7 and preferably 2.4 to 2.7.

Claims (2)

PATENT CLAIMS. 1. Process for the processing of lithium ores, in particular of a- or f-spodumene, in which the lithium ores are mixed with calcium carbonate, sand and Calcium chloride roasts the cement clinker formed at around 1100 to 1200 ° C separates and those escaping during roasting Separates chloride vapors and dissolves in water, whereupon the chloride solutions turn to lithium, sodium and potassium compounds are worked up, characterized in that the chloride solutions obtained with the mixture of sodium chloride deposited in a subsequent process stage and lithium carbonate are added, solid sodium chloride from the slurry thus obtained at a temperature of about 25 to 30 ° C, separated from the mother liquor Addition of sodium carbonate and heating to 60 to 100 ° C precipitates lithium carbonate, the remaining solution after its separation to 40 to 65 a / o solids evaporated and at 90 to 100 ° C the mixture of sodium chloride and lithium carbonate separates, with which you get the chloride solutions obtained by washing out the vapors added, and that from the remaining solution by cooling to about 0 to 5 ° C potassium chloride ruled out. 2. The method according to claim 1, characterized in that the solution remaining after the potassium chloride has been separated off is used to wash out the chlorides from the vapors escaping from the cement kiln. Documents considered: German Patent No. 431 257; U.S. Patent Nos. 2,627,452, 2,726,138; Gmelins Handbuch der inorganic Chemie, B. Edition, Volume Lithium, 1927, p. 223; D'Ans-Lax, "Pocket book for chemists and physicists", 1943, p. 918; D'Ans, "The solution equilibria of the systems of the salts of oceanic salt deposits", 1933, pp. 63 to 70.