RU2215690C2 - Method for processing nepheline concentrate - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: invention relates to technology for processing alumosilicate raw, mainly nepheline or nepheline concentrate. Nepheline or nepheline concentrate is decomposed with sulfuric acid, insoluble precipitate is separated and washed out and potassium or ammonium sulfate as potassium or ammonium alum is added to the solution, washed out their from impurities followed by thermic treatment of alum and isolation of alumina from calcined product. Mother liquor after separation of alum is neutralized, mixture of aluminum and iron hydroxides is isolated and sodium sulfate is isolated by evaporation. Invention provides the enhancement of quality of preparing alumina by content of impurities of iron and silicon. EFFECT: improved processing method.

Description

 The method relates to a technology for processing aluminosilicate raw materials, in particular to the production of alumina from nepheline-containing raw materials, mainly nepheline or nepheline-containing concentrates, for example apatite flotation tailings.

 A known method of producing alumina by sintering nepheline-containing concentrate with limestone and subsequent leaching of aluminates (Talmud M.L. Nefelin - a new type of complex raw materials // Bulletin TSNIINTSM 8/85 / - 1957 - S. 30-34). The method is characterized by high economic performance due to the integrated use of all components and waste-free production.

 The disadvantages of the method are its bulkiness, high consumption of limestone and increased requirements for it, high energy consumption, insufficient quality of alumina in terms of the content of impurities of iron, alkali, silicon.

The method that is closest in essence (Yu.A. Liner. Complex processing of aluminum-containing raw materials by acid methods. M .: Nauka - 1982 - p. 184), including sulfuric acid decomposition of nepheline concentrate, the separation of potassium alum, purification of alum from iron by recrystallization and ( or) washing with a solution of potassium sulfate, heat treatment to obtain a mixture of alumina and potassium sulfate, washing alumina from potassium sulfate, the separation of alumina and their heat treatment to obtain sodium aluminates and processing aluminates alumina. It is recommended to restore Fe ⁺³ to Fe ⁺² to improve iron removal.

 The disadvantage of this method is that only a quarter of all the aluminum contained in nepheline is released in the form of pure alum-potassium alum, from which alumina suitable for various fields of technology is directly isolated. The main part of aluminum is released in the form of sodium alum, together with all acid-soluble impurities of nepheline. Therefore, the separation of alumina from them requires additional cleaning operations from impurities, in fact, conducting a cycle according to the Bayer method. The disadvantage of this method is the use for washing alum with a solution of potassium sulfate, because Further, purification of potassium sulfate from aluminum is required.

 The present invention is aimed at improving the method of sulfuric acid processing of nepheline or nepheline-containing concentrate and to improve the quality of the obtained alumina.

 The problem is solved in that in a method for processing nepheline or nepheline-containing concentrate, including decomposing it with sulfuric acid, separating and washing an insoluble residue, separating alum from the aluminum solution, washing them from impurities, heat treating the alum and isolating alumina from the calcined product, according to According to the invention, potassium or ammonium sulfates are introduced into the solution and aluminum is isolated in the form of potassium or potassium and ammonium alum, and the mother liquor is neutralized after separation of the alum. A mixture of aluminum and iron hydroxides is added and sodium sulfate is isolated by evaporation.

 The allocation of aluminum in the form of well-crystallizing potassium and ammonium alum allows you to clean them from impurities by washing and recrystallization to the required rate. Spent wash solutions are used to leach alumina and to wash the insoluble residue. The use of circulating solutions for leaching and washing promotes the formation of a well-filtered precipitate and allows the alumina dissolved in the washings to be returned to the process, and also avoids supersaturation of the solution and crystallization of alum on the filter during vacuum filtration.

 Thus, in addition to the insoluble residue, the loss of alumina can only be with the mother liquor after the precipitation of alum from the leach solution, therefore, the aluminum remaining after the precipitation of alum, 5-10% of its content in the nepheline-containing raw material, is precipitated together with iron by neutralizing the solution with soda or lime to pH 7-8. A precipitate containing a mixture of aluminum and iron hydroxides and in which gallium is concentrated can be processed into alumina or a coagulant by known methods. Sodium sulfate can be isolated from the solution by evaporation.

 As a nepheline-containing concentrate, nepheline concentrate or other nepheline-containing products, for example apatite flotation tailings (HAF), which are currently discharged into the tailing dump, can be used.

 The invention can be illustrated by the following examples.

 Example 1

100 g of nepheline concentrate, composition, wt.%: Al ₂ About ₃ -27.9; SiO ₂ -44.1; Na ₂ O-13.9; K ₂ O-6.9; Fe ₂ O ₃ -3.4, mixed with 100 g of 93% sulfuric acid and 45 ml of water, the resulting reaction mixture is pulp in 400 ml of water and leached at 90 ^o 1 hour. The precipitate is filtered off (filtration time 25 minutes), washed with repulpation of 100 ml of water, filtered and washed on the filter with water. Get 480 ml of a solution containing, g / l: Al ₂ About ₃ -52,2; Na ₂ O-22.4; K ₂ O-11.8; Fe ₂ O ₃ -2.8. Extraction of aluminum in solution was 89%. The weight of the wet sediment is 142 g.

35 g of potassium sulfate is introduced into the solution with stirring, the pulp is cooled to 20 ^o C, the precipitated alum-potassium alum is filtered off, the weight of alum is 230 g, the volume of the mother liquor is 305 ml. Alum is washed twice with 500 ml of cold water by repulpation, dissolved in 500 ml of water by heating, the alum that is released upon cooling is filtered off and washed on the filter with cold water. 113 g of alum is obtained. Alum is calcined for 1 hour at 850 ^o C and the calcined product is treated with stirring in three portions of 300 ml of hot water, 16.5 g of potassium sulfate are isolated from the first portion of the washing solution by evaporation. The washed alumina is filtered off and calcined at 800 ^o C. The weight of the obtained alumina is 10.5 g, the form is corundum. The content of impurities, wt.%: Fe ₂ O ₃ -0,027; K ₂ O-0.25; Si0 ₂ <0.01.

After isolation of the alum, the solution was neutralized with soda to pH 8 and the precipitate formed was filtered off. The weight of the dry precipitate was 4.5 g, the content of Al ₂ O ₃ -48.3 wt.%, Fe ₂ O ₃ -27.4 wt.%, Ga ₂ O ₃ -0.01 wt.%.

The solution after separation of the aluminum and iron hydroxides is evaporated to 135 ml, after cooling to 18 ^{° C.} 55 g of sodium sulfate are isolated.

 Example 2

100 g of nepheline concentrate decompose 100 g of sulfuric acid, but the acid is diluted to 70% with 45 ml of the first wash solution and the first wash solution of Example 1 is used for leaching and repulpation. The filtration time is 5 minutes, the filtration rate is 950 cubic meters. m / m ² h. Receive 720 ml of solution and 127 g of insoluble residue. 27 g of ammonium sulfate are introduced into the solution with stirring and cooling to 15 ^{° C.} The separated mixture of potassium and ammonium alum is filtered off, the weight of alum is 255 g, the volume of the mother liquor is 520 ml. Alum is washed by repulpation in succession with two portions of the solutions of Example 1 (rinse and uterine after recrystallization), dissolved in 500 ml of water with heating, and the alum formed during cooling is filtered off and washed on the filter with cold water. 226 g of alum is obtained. Alum is calcined for 1 hour at 850 ^o C and the calcined product is treated with stirring in three portions of 300 ml of hot water, 20.6 g of potassium sulfate are isolated from the first portion of the washing solution by evaporation. The precipitate of alumina is filtered off and calcined at 800 ^° C. 23.8 g of gamma-alumina are obtained. The content of impurities, wt.%: Fe ₂ About ₃ -0,023; K ₂ O-0.14; SiO ₂ <0.01. Alumina recovery - 86.4%.

After isolation of the alum, the solution was neutralized with soda to a pH of 8.5 and the precipitate formed was filtered off. The weight of the dry precipitate is 5.7 g, the content of Al ₂ O ₃ -38.3 wt.%, Fe ₂ About ₃ -24.6 wt.%.

The solution after separation of the aluminum and iron hydroxides is evaporated to 120 ml, after cooling to 18 ^{° C.} , 69 g of sodium sulfate are isolated.

 Example 3

100 g of nepheline concentrate decompose, as in example 2. But for leaching and repulpation use the solutions of example 2. Filtration rate - 945 cubic meters. m / m ² h. Receive 700 ml of solution and 148 g of insoluble residue. 27 g of ammonium sulfate are introduced into the solution with stirring and cooling to 15 ^{° C.} The separated mixture of potassium and ammonium alum is filtered off, the weight of alum is 252 g, the volume of the mother liquor is 505 ml. Alum is washed by repulpation in succession with two portions of the solutions of Example 2 (washing and uterine after recrystallization), dissolved in 500 ml of water by heating, the alum formed during cooling is filtered off and again dissolved in 500 ml of water, crystallized and washed on a filter with cold water. 220 g of alum are obtained. Alum is calcined for 1 hour at 850 ^o C and the calcined product is treated with stirring in three portions of 300 ml of hot water, 10.7 g of potassium sulfate are isolated from the first portion of the washing solution by evaporation. The precipitate of aluminum oxide is filtered off and calcined at 800 ^° C. 23.6 g of gamma-alumina are obtained. The content of impurities, wt. %: Fe ₂ O ₃ -0.009; K ₂ O-0.04; SiO ₂ <0.01. Alumina recovery - 85.8%.

After isolation of the alum, the solution was neutralized with soda to a pH of 8.5 and the precipitate formed was filtered off. The weight of the dry precipitate is 6.1 g, the content of Al ₂ O _{3 is} 39.3 wt.%, Fe ₂ O _{3 is} 21.2 wt.%.

The solution after separation of aluminum and iron hydroxides is evaporated to 130 ml, after cooling to 18 ^o C, 70 g of sodium sulfate are isolated.

 Example 4

100 g of nepheline concentrate are decomposed, as in Example 3, the acid is diluted to 70% with 45 ml of the first wash solution, and the solutions of Example 3 are used for leaching and repulpation. The filtration rate is -1060 m ³ / m ² h. 705 ml of solution and 131 are obtained g of insoluble residue. The solution is cooled to 20 ^o C, the weight of the released potassium alum is 56 g. The alum is filtered off, washed by repulpation in succession with three portions of 150 ml of the solutions of Example 3 (washing and uterine after recrystallization), dissolved by heating in 150 ml of the 2nd recrystallization solution and the precipitated upon cooling, the alum is filtered off and washed on the filter with cold water. Obtain 52 g of potassium alum. Alum is calcined for 1 hour at 850 ^o C and the calcined product is treated with stirring in three portions of 150 ml of hot water. The precipitate was filtered off and calcined at 800 ^° C. The weight of the obtained alumina was 5.1 g, corundum. The content of impurities, wt.%: Fe ₂ About ₃ -0,035; K ₂ O-0.3; SiO ₂ <0.1.

After separation of potassium alum, 27 g of ammonium sulfate are introduced into the solution with stirring, the weight of the released ammonium alum is 191 g, the volume of the mother liquor is 506 ml. The alum is filtered off and washed by repulpation in successions of 350 ml of the solutions of Example 3 (washing and uterine after recrystallization), dissolved by heating in 350 ml of the 2nd recrystallization solution, the alum released by cooling is recrystallized in 350 ml of hot water, filtered and washed with cold water filter. 162 g of ammonium alum is obtained. Alum is calcined for 1 hour at 850 ^o C and the calcined product is treated with four portions of 300 ml of hot water with stirring. The precipitate is filtered off and calcined at 800 ^° C. The weight of the obtained alumina is 18.1 g, gamma alumina. The content of impurities, wt. %: Fe ₂ O ₃ -0.009; K ₂ O-0.03; SiO ₂ <0.01.

After isolation of the alum, the solution is neutralized with soda to pH 8.0 and the precipitate formed is filtered off. The weight of the dry precipitate is 5.3 g, the content of Al ₂ O ₃ -49.2 wt.%, Fe ₂ O ₃ -28.3 wt.%.

The solution after separation of the aluminum and iron hydroxides is evaporated to 140 ml, after cooling to 16 ^{° C.} , 79 g of sodium sulfate are isolated.

 Example 5

100 g of tailings of apatite flotation (HAF), composition, wt.%: Al ₂ O ₃ -21.7; SiO ₂ -41.1; Na ₂ O-11.3; K ₂ O-6.2; Fe ₂ O ₃ -8.4; P ₂ O ₅ -2.4 is mixed with 100 g of 70% sulfuric acid, the resulting reaction mixture is pulped in 300 ml of mother liquor from the first recrystallization of Example 4 and leached at 90 ^{° C. for} 0.5 hours. The precipitate is filtered off (filtration time 3 min), washed with repulpation of 100 ml of mother liquor from the recrystallization of the alum of Example 4, filtered and washed on the filter with water. The weight of the wet cake is 136 g. 24 g of ammonium sulfate are introduced into the resulting 380 ml of the solution with stirring, the pulp is cooled to 18 ^° C, the alum precipitated is filtered off and washed on the filter with the mother liquor from recrystallization of Example 4. The weight of the alum is 142 g, the volume of the mother liquor is 285 ml Alum is dissolved by heating in 250 ml of a solution of 2nd recrystallization, the alum released by cooling is again recrystallized in 250 ml of hot water, filtered and washed on a filter with cold water. 122 g of alum are obtained. Alum is calcined for 1 hour at 900 ^o C and the calcined product is treated with stirring in three portions of 150 ml of hot water. The washed alumina is filtered off and calcined at 800 ^° C. The weight of the obtained alumina is 13.8 g. Impurity content, wt.%: Fe ₂ O ₃ -0.013; K ₂ O-0.05; SiO ₂ <0.01. Extraction into alumina is not considered because 15-20% of the aluminum in the CAF is associated with acid-insoluble minerals.

After isolation of the alum, the main mother liquor, containing 2.7 g / l Al ₂ O ₃ and 4.7 g / l Fe ₂ O ₃ , is treated with stirring CaO to pH 7.5 and the precipitate is filtered off. The weight of the precipitate is 31.2 g, the content of Al ₂ O ₃ -2.4 wt.%, Fe ₂ O ₃ -4.2 wt. %

The solution after separation of the precipitate is evaporated to 95 ml, after cooling to 15 ^o With 51 g of sodium sulfate.

 The above examples indicate that, according to the proposed method, from alpheline-containing raw materials, including from apatite enrichment waste, apatite flotation tailings, alumina can be obtained that exceeds the best grades of industrial alumina in the content of basic limiting impurities. Given that losses can only be with the mother liquor, the yield of high-quality alumina should be high enough.

 When nepheline is processed by additional extraction from the mother liquor, about 7% of alumina is additionally released during gallium concentration by about 10 times. The use of leaching solutions for leaching improves filtering by 4-5 times.

Potassium or ammonium sulfates for the precipitation of alum are circulating, formed respectively when washing a calcined product containing a mixture of alumina and potassium sulfate or calcining ammonium alum at 550-600 ^o C.

Claims (1)

 A method of processing nepheline concentrate, including its decomposition with sulfuric acid, separation and washing of an insoluble residue, separation from aluminum solution in the form of alum, washing them from impurities, heat treatment of alum and separation of calcined alumina product, characterized in that potassium sulfates or ammonium and aluminum are isolated in the form of potassium or potassium and ammonium alum. and the mother liquor after neutralization of alum is neutralized, a mixture of aluminum and iron hydroxides is isolated and sodium sulfate is isolated by evaporation.