Method of Processing and Treatment of Alunite Ores

Abstract

The alunite ore processing method consists of crushing, grinding and flotation of raw alunite ore. The enriched alunite ore is roasted at 520 to 620 C., the roasting time is 1 to 3 hours. The roasted alunite is leached with 5 to 20% sodium carbonate solution, which is in 100 to 110% of the stoichiometric amount required to bond the SO.sub.3 aluminum sulfate in the alunite with leaching conditions of 70-100 C. for 0.5-2.0 hours. The obtained slurry contains all of the potassium sulfate from the alunite and all of the sodium sulfate obtained from sodium carbonate. In the insoluble residue remains all aluminium oxide and residual rock. The sulfate solution is separated from the insoluble residue and is converted with potassium chloride to potassium sulphate (fertilizer) and kitchen salt. The insoluble residue is treated by the Bayer method without the use of an autoclave and results in aluminium oxide (alumina) and quartz sand.

Claims

1. Process for the treatment of alunite ores comprises the following steps: crushing of alunite ore, grinding the alunite ore, enrichment of the alunite ore by flotation to the content of at least 50% of alunite by weight, roasting at 520 to 620 C. for 1 to 3 hours, preparation of a sodium carbonate solution, which is later used in a leaching process characterized in that the sodium carbonate solution comprises 5 to 20% sodium carbonate solution and is added to the alunite ore in a quantity of 100 to 110% of the stoichiometric amount required to bond the SO.sub.3 to the aluminum sulphate in the alunite ore, thereby forming a sodium sulphite solution, separation of the sodium sulphate solution from an insoluble residue, conversion of the sodium sulphate with KCl to potassium sulphate and sodium chloride to form a suspension, filtration and washing of the suspension to form a filtrate and washing water, evaporation of the filtrate and of the washing water, and treating the insoluble residue by the Bayer method without the use of an autoclave to form a product comprising aluminium oxide (alumina) and quartz sand.

2. The process of the treatment of alunite ores according to claim 1, characterized in that the solution of Na.sub.2CO.sub.3 is prepared in a 5% excess over the stoichiometric balance of the following equation: Al.sub.2(SO.sub.4).sub.3.2Al.sub.2O.sub.3+waste rock+3Na.sub.2CO.sub.3=K.sub.2SO.sub.4+3Na.sub.2SO.sub.4+3Al.sub.2O.sub.3+waste rock+3CO.sub.2, where 3Al.sub.2O.sub.3+waste rock is the insoluble residue and comprises one or more of silica, silica sand (SiO.sub.2) and aluminosilicate.

3. The process of the treatment of alunite ores according to claim 1, characterized in that the leaching is carried out at a temperature of 70 to 100 C. tor 0.5 to 2.0 hours during the course of a reaction characterized by the equation according to claim 2.

4. The process of the treatment of alunite ores according to claim 3, characterized in that the Bayer method without the use of an autoclave takes place with NaOH at a temperature below 100 C.

5. The process of the treatment of alunite ores according to claim 4, characterized in that the product from the Bayer method is processed by hydroseparation to produce a sand fraction comprising aluminosilicate and a clay fraction comprising -Al.sub.2O.sub.3.

6. The process of the treatment of alunite ores according to claim 5, characterized in that the clay fraction is precipitated to form a cake, which is washed, thereby forming a sludge in a resulting sediment and a resulting supernatant.

7. The process of the treatment of alunite ores according to claim 6, characterized in that the sand fraction formed by the hydroseparation is washed and filtered to produce silica sand and a filtrate.

8. The process of the treatment of alunite ores according to claim 7, characterized in that the filtrate after the filtration of the sand fraction and the supernatant after the precipitation of the clay fraction are combined and to form a solution, which undergoes desilication to form a white sludge and an aluminate solution.

9. The process of the treatment of alunite ores according to claim 8, characterized in that a reaction of the white sludge with sulfuric acid results in the formation of a coagulant.

10. The process of the treatment of alunite ores according to claim 8, characterized in dial the supernatant formed from desilication is decomposed to form Al(OH).sub.3 and a mother liquor, which is further evaporated to form a working solution which is used as a starting reagent in a second Bayer method reaction (re-concentration and recycling of water).

11. The process of the treatment of alunite ores according to claim 10, characterized in that metallurgical -Al.sub.2O.sub.3 is formed by the calcination of Al(OH).sub.3.

12. The use of sodium carbonate Na.sub.2CO.sub.3 in the leaching process according to claim 1 for the treatment of alunite ores and the production of one or more of aluminium oxide potassium sulphate, quartz sand, coagulant for the purification of utility and potable water and kitchen salt.

Description

EXAMPLES OF EMBODIMENTS OF THE INVENTION

Example 1

[0021] We take an alunite ore with an alunite content of 60% by weight, with the following composition, % by weight:

TABLE-US-00001 K.sub.2O Al.sub.2O.sub.3 SO.sub.3 H.sub.2O nn 6.82 22.17 23.18 7.82 40 99.9

[0022] 100 g of alunite (alumina) is crushed. Alunite (alunite ore) is further grinded, after the flotation enrichment it is roasted in an oven at T=550 C. for 1 hour and then leached in the solution of Na.sub.2CO.sub.3.

[0023] A sodium salt solution is prepared: 22.2 g of Na.sub.2CO.sub.3 is dissolved in 350 ml of water, the amount of soda is 105% wt. from stoichiometric. The leaching time is 1.5 hours at T.sub.leach 90 C.

[0024] Into solution are transferred: K.sub.2O99% by weight; Na.sub.2CO.sub.3-100% by weight; Al.sub.2O.sub.3 0.5% wt.; SO39 8% wt. or K.sub.2O=6.8 g, Na.sub.2O=13 g, SO.sub.3=2.3 g, Al.sub.2O.sub.3=0.1 g.

[0025] In the insoluble residue remains 62.2 g. CO.sub.2 gas is formed.

[0026] The suspension is filtered and washed.

[0027] The filtrate with the washing water is evaporated.

[0028] We obtain a mixture of sulphates K, Na, where the sulphate K is 12.5 g, Na sulphate29.8 g, the total of 42.3 g of the mixture. This is a mixture of sulphates obtained from the evaporated mixture of the filtrate and washed water.

[0029] It is required 23.7 g of KCl to produce 29.8 g of Na.sub.2SO.sub.4. This is reaction number 2: K.sub.2SO.sub.4+3Na.sub.2SO.sub.4+6KCl=4K.sub.2SO.sub.4+6NaCl, with K.sub.2SO.sub.4 already present in the alunite in the amount of 12.5 g.

[0030] The result is 36.6 g of K.sub.2SO.sub.4 plus 12.5 g of K.sub.2SO.sub.4 from alunite. Total of 49 g of K.sub.2SO.sub.4 and NaCl of 16.8 g.

Example 2

[0031] The method of treating the alunite ore consists of the following steps: [0032] 1. The alunite ore from the mine is crushed resulting in particles of 10 to 20 mm in size. [0033] 2. Followed by wet milling with a resulting particle size of the resulting powder under 0.074 micron (passed through a 200 mesh). [0034] 3. Enrichment of the ground alunite ore by means of flotation. The resulting weight of the enriched ore containing 60% of alunite is 5.02 t. [0035] 4. Drying and roasting of the enriched alunite ore from step 3 at 530 to 550 C. for one hour. After drying and roasting, the weight of alunite ore is 4.63 tons. [0036] 5. A solution from 1.12 t of Na.sub.2CO.sub.3 (100%) is prepared, the solution is prepared in a 5% excess over the stoichiometric balance of equation (1).

K.sub.2SO.sub.4.Al.sub.2(SO4).sub.3.2Al.sub.2O.sub.3+waste rock+3Na.sub.2CO.sub.3=K.sub.2SO.sub.4+3Na.sub.2SO.sub.4+3Al.sub.2O.sub.3+waste rock+3CO.sub.2,(1)

where 3Al.sub.2O.sub.3+waste rock is the insoluble residue. The waste rock contains silica, silica sand (SiO.sub.2) and aluminosilicate (alumosilicate). [0037] 6. The enriched alunite ore, after drying and roasting from step 4, is leached in a solution of Na.sub.2CO.sub.3 prepared according to step 5 for 1.5 hours at 90 C. in the course of the reaction (1). [0038] 7. The slurry suspension from leaching (step 6) is filtered and the filter cake is washed. 2.133 t of solution for evaporation is formed (mother liquors containing Na.sub.2SO.sub.4 and K.sub.2SO.sub.4 and an insoluble residue). [0039] 8. The water after the washing of the cake can be used to prepare the solution of Na.sub.2CO.sub.3. The mother liquors from step 7 are evaporated/concentrated and converted according to the reaction (2) to K.sub.2SO.sub.4 fertilizer (2.47 t) and kitchen salt NaCl (0.845 t).

K.sub.2SO.sub.4+3Na.sub.2SO.sub.4+6KCl=4K.sub.2SO.sub.4+6NaCl(2)

[0040] 1.19 t of KCl is used for the conversion. [0041] 9. The insoluble residue from step 5 (3Al.sub.2O.sub.3+waste rock) is processed by the Bayer method according to the reaction (3) without using an autoclave at a temperature below 100 C. 0.05 t of NaOH and the working solution are introduced into the reaction.

Al.sub.2O.sub.3+2NaOH=2NaAlO.sub.2+H.sub.2O.(3)

[0042] Aluminium oxide (alumina) is formed and remains unchanged waste rock, i.e. silica sand (SiO.sub.2) and aluminosilicate. [0043] 10. The products from step 9 are hydroseparated into the sand fraction and the clay fraction (aluminosilicate and alumina). [0044] 11. The clay fraction from step 10 is precipitated and the filter cake is rinsed, with the formation of sludge in the sediment and the supernatant. [0045] 12. The sand fraction is washed and filtered to form the silica sand (2.0 t) and the filtrate. [0046] 13. The filtrate after filtration of the sand from step 12 and the supernatant after precipitation of the clay fraction from step 11 are combined. Thusly formed solution undergoes desilication to form a white sludge and aluminate solution (supernatant). [0047] 14. A reaction of the white sludge with H.sub.2SO.sub.4 (0.05 t) gives the coagulant from the white sludge (0.33 t). [0048] 15. The solution of aluminates resulting from the desilication from step 13 is further decomposed to form Al(OH).sub.3 and the mother liquor. The mother liquor may be further evaporated to form a working solution which may enter step 9 (re-concentration and recycling of water).

[0049] 16. One ton of -Al.sub.2O.sub.3 is formed by calcination of Al(OH).sub.3.

BRIEF DESCRIPTION OF DRAWINGS

[0050] Diagram in FIG. 1 shows the method for processing and treating of alunite ores.

ADVANTAGES OF THE INVENTION OVER THE PRIOR ART

[0051] Production of metallurgical aluminium oxide (alumina, Al.sub.2O.sub.3) reaches 90 [0052] The amount of SOP produced is increased 4 times, with a yield of 90%. [0053] Procedures that pollute the environment with dust and gas (SO.sub.2) are eliminated. [0054] There is no need to use precious and expensive raw materials. [0055] This method is in fact free of solid waste. [0056] In addition to the efficient production of metallurgical aluminite and SOP, this method allows to simultaneously produce other products: kitchen salt, quartz sand and coagulant for cleaning potable and industrial water.

INDUSTRIAL APPLICABILITY

[0057] According to the present invention, the method for the treatment of alunite is used to treat alunite ores with the production of Al.sub.2O.sub.3, as well as potassium sulphate, quartz sand, utility and potable water purification coagulant and kitchen salt as a by-product.