RU2344076C2 - Method of integrated processing of magnesium-chrome crude ore - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used for production of high-purity silicon dioxide within integrated processing of magnesium-chrome crude ore that is mixed serpentinite, chromite, pyroxene and other minerals. Method of integrated processing of magnesium-chrome crude ore includes as follows. Crude ore is decomposed by solution of mineral acids. Produced suspension is filtered, and insoluble residue is processed. Filtrate neutralisation is accompanied with sedimentation of contained metal hydroxides with washing and drying of produced end-products. Processing of insoluble residue includes annealing at temperature 350-600°C, following dissolution in caustic soda to residual alkalinity 40-60 g/l NaOH, filtering of prepared suspension, washing of residue that is chrome ore concentrate and sedimentation of silicon dioxide from produced filtrate with solution of hydrochloric acid to residual acidity 2-15 g/l HCl.

EFFECT: higher separation integrity of silica component with simultaneous integrated extraction of other components of crude ore that provides extended application of base mixtures.

6 tbl, 2 ex

Description

The invention relates to the field of hydrometallurgical processing of non-metallic minerals and can be used to obtain high-purity silicon dioxide (an analogue of white carbon) in the processes of complex processing of magnesium-containing ore raw materials (a mixture consisting of serpentinite, chromite, pyroxene, chlorite and other minerals).

When processing natural or technogenic raw materials, which include silica (SiO ₂ ) or silicon dioxide in the form of silicic acid (SiO ₂ × nH ₂ O), its silica component has traditionally been considered as a ballast and difficult to recycle part. At the same time, highly dispersed amorphous silicon dioxide, which is produced on the basis of acid processing of expensive liquid glass, is used in large quantities in various industries.

There are a number of minerals: nepheline, eudialyte, feldspar, olivine, serpentine, etc., the acid and alkaline decomposition of which is accompanied by the transfer into the solution of not only metal salts, but also silica in the form of silicic acid. Therefore, when processing this type of raw material, the urgent problem is the separation of the silica component in the form of a high-quality product - silicon dioxide, which is widely used in a number of industries - electronic, chemical, bus, etc., to obtain silicate materials with unique properties: optical fibers (devices for directional transmission light energy), semiconductors, additives to improve the physical and mechanical properties of polymers and rubbers, etc.

A known method of processing non-metallic minerals, in particular acidic glassy rocks (pumice or obsidian), in order to obtain silicon dioxide, including grinding, leaching with an alkali solution (concentration of 130-260 g / l NaOH) at 100-180 ° C and the ratio of W : T = 1: (2-4), filtering the suspension, electromagnetic treatment of the filtrate, in order to purify iron oxide impurities, precipitating silicic acid gel from the filtrate with a solution of mineral acids (hydrochloric or nitric) to pH = 6.5-7.0 s subsequent filtration of the suspension, washing y and drying of silicon dioxide. (SU 1791383 A1, C 01 B 33/12, publ. 1/30/1993)

However, the use of this processing method for magnesium-chromium-containing ore raw materials containing weakly magnetic and non-magnetic minerals such as fibrous asbestos, forsterite, chlorite, pyroxene, chromite, etc., is inefficient, since the electromagnetic method of purifying the filtrate (liquid glass) from part of the undecomposed raw material will not allow to obtain a high yield silica with a low content of impurities.

A known method of processing silicate raw materials, in particular nepheline concentrate, including: decomposition of raw materials with sulfuric or hydrochloric acid (5.0-30.0% concentration), filtering the suspension, heat treatment (dehydration) of the filtrate at 80-300 ° C, purification of the dehydrated product from impurities by leaching with hot water or a slightly acidic solution, filtering the suspension and separating silicon dioxide from the liquid phase, drying and packaging of the finished product. (RU 2179527, IPC С 01 В 33/187, publ. 02.20.2002)

The finished product is characterized by good physicochemical properties: a large specific surface area (at least 100 m ² / g) and a high content of silicon dioxide (at least 90%).

The disadvantage of this method is that it is suitable for processing mineral raw materials, well decomposed by weak solutions of mineral acids (5.0-30.0% concentration), for example, such as nepheline, eudialyte, feldspars and other minerals, with the formation of water-soluble potassium or sodium silicates, and cannot be used in the processing of serpentine-chromite ore mixtures, since the minerals included in its composition (chromite, chrompicotite, olivine, pyroxene, forsterite, etc.), such weak solutions of acids practically not are opened.

The closest in technical essence analogue is the method of complex processing of serpentinite. (RU No. 20973322, IPC S 01 B 33/142, publ. 11/27/1997)

The essence of the method is as follows.

Grinded to particle sizes of 0.074 mm, serpentinite is decomposed with sulfuric acid at a concentration of 20-50% and the resulting suspension is filtered. In the first stage, a precipitate is obtained consisting of amorphous silica and undecomposed minerals, and a filtrate. The precipitate is subjected to magnetic separation to separate the chromomagnetite concentrate from silicon dioxide. The filtrate is neutralized to a pH of 7.0-8.5, hydroxides Fe ³⁺ , Al ³⁺ , Cr ³⁺ , Ni ²⁺ are precipitated. From the remaining filtrate by carbonization, followed by precipitation and filtration, magnesium carbonate is obtained, which by calcination is converted into burnt magnesia, sintered or fused periclase. Silicon dioxide, after electromagnetic separation from undecomposed raw materials, is washed from water-soluble salts, dried and calcined.

The finished product is characterized by a high content of SiO ₂ :

- not lower than 87.7% (dried at 105 °),

- 99.0% (calcined at 900-1000 °).

The reasons that prevent the widespread use of the above method are as follows:

- the method of separating part of the undecomposed raw material from silica by magnetic separation can be used in the processing of ore mixtures containing minerals with magnetic properties. For example, such as magnetite, ovenite and other minerals, as well as chrompicotite and chromite with rich inclusions of iron oxides FeO and Fe ₂ O ₃ . It is the presence of disseminated iron oxides in chrome spinels that gives them magnetic properties;

- the application of the magnetic separation method for the separation of poor chromite ore mixtures containing non-magnetic or weakly magnetic minerals such as sarpentinite, olivine, pyroxene, chlorite, etc., is not economically feasible, since it requires the use of expensive and inefficient sophisticated special equipment. It was experimentally established that even the use of such equipment for the electromagnetic separation of the precipitate after leaching of serpentine-chromite ore with mineral acid does not guarantee the production of silicon dioxide free of impurities (see example 1);

- leaching of serpentinite with a particle size of less than 0.074 mm creates great difficulties in filtering the suspension and requires additional costs for grinding the ore mixture.

An object of the invention is to develop a cost-effective method for the integrated processing of magnesium-chromium-containing ore raw materials, ensuring maximum extraction of valuable components of the raw materials (magnesium, chromium, silicon, manganese, iron) and obtaining from any serpentine ore mixtures (including those that do not contain minerals) with magnetic properties) of finely divided silica.

The technical result from the application of the invention is to ensure the most complete separation of the silica component from the raw material while simultaneously comprehensively extracting valuable components of the raw material, which provides an extension of the scope of use of poor ore mixtures.

The technical result is achieved due to the fact that in the method of complex processing of magnesium-chromium-containing ore raw materials, including decomposing the raw material with a solution of mineral acids, filtering the resulting suspension, treating the insoluble residue, neutralizing the filtrate with precipitating the hydroxides of the metals contained therein, washing and drying the resulting final products, processing insoluble the residue consists in firing it at a temperature of 350-600 ° C, followed by dissolution in caustic soda with a residual alkalinity of 40-60 g / l NaOH, fil washing the obtained suspension, washing the precipitate — chromite concentrate, and precipitating silicon dioxide from the obtained filtrate with a hydrochloric acid solution to a residual acidity of the mother liquor of 2-15 g / l HCl.

The method is as follows: natural serpentine-chromite ore mixture (mineral and chemical composition, see table 1) is crushed to a particle size of less than 2 mm and leached with mineral acids (sulfuric 40-42% H ₂ SO ₄ or hydrochloric 10-20% HCl at 60 -80 ° C in the ratio t: g in the reaction zone 1: (2.5-4.0) for 1-2 hours until the residual acidity in the suspension (4.0-6.0 g / l H ₂ SO ₄ or 1.0-3.0 g / l HCl) After which the suspension is filtered.

The filtrate solution of sulfates (chlorides) of magnesium, iron, aluminum and manganese is neutralized in 2 stages: to pH = 7.0-8.5 in order to precipitate the hydroxides Fe ³⁺ , Al ³⁺ , Cr ³⁺ , Mn ^2+, and pH = 9.0-11.0 to obtain magnesium hydroxide. The neutralization is carried out with a solution of soda ash.

Modified iron oxide pigments are obtained from Fe ³⁺ , Al ³⁺ , Cr ³⁺ , Mn ²⁺ hydroxides, and periclase from Mg ²⁺ hydroxide.

To obtain high-purity silicon dioxide free of impurities of chromite, pyroxene, and other minerals, an insoluble residue - cake 1, obtained after sulfuric acid (or hydrochloric acid) leaching of the ore mixture and containing a mixture of amorphous silica and insoluble minerals (chromite, pyroxene, chlorite, etc.), washed from water-soluble salts (sulfates or chlorides), dried at 105-110 ° С, burned at 350-600 ° С for 2 hours in order to dehydrate the cake, dehydrate silica SiO ₂ × 4H ₂ O and destroy amorphous silica structures (Tables 2, 3, 4 show the mineral and dispersed chemical composition of the insoluble residue - cake 1). It is established that silicon dioxide (silica) after such a treatment acquires an increased ability to dissolve in alkalis.

Next, cake 1 is treated with a solution of caustic soda (with a concentration of 140-180 g / l NaOH) for 15-30 minutes, at 50-70 ° C and a ratio of t: w = 1: 4, until the NaOH content in the suspension is at least 40- 60 g / l The suspension is filtered, the insoluble residue is a chromite concentrate, washed from impurities by repulpation in hot water, dried and packaged. The finished product contains at least 55.0-58.0% Cr ₂ About ₃ .

The filtrate, after separation of chromite concentrate, the so-called a solution of silica in caustic soda (or water glass), a concentration of NaOH of at least 40% is treated with hydrochloric acid solution (not more than 20% HCl) at 70% to a residual acidity in the mother liquor of 2.0-15.0 g / l HCl. The suspension is filtered, the precipitated silica residue is separated from the mother solution of sodium chloride by filtration, washed from water-soluble salts with hot water and repulpation, dried at 105 ° C, calcined at 900 ° C and tarnished. In order to obtain highly pure silica containing a minimum concentration of impurities, the silica precipitate is washed with such a quantity of water that the volume of washing water would be 1.8-3.0 times the volume of the filtered suspension.

The finished product is characterized by high physical and mechanical properties (see table 5, 6).

Table 1 shows the mineral and chemical compositions of the initial serpentine-chromite ore mixture.

Table 2, 3 shows the mineral and chemical compositions of the insoluble residue (cake 1).

Table 4 shows the mineral and chemical compositions of a non-magnetic product obtained by electromagnetic separation of amorphous silica from insoluble minerals in cake 1.

Table 5 shows the technological indicators of the process of separation of silicon dioxide from alkaline solutions.

Table 6 shows the physicochemical properties of silicon dioxide obtained by the claimed method and calcined at 900 ° C.

Example 1 (processing of poor serpentine-chromite ore was carried out according to the technology of the prototype):

1000 grams of serpentine-chromite ore mixture, a particle size of 0.074 mm, is treated with a solution of sulfuric acid at a concentration of 520 g / l at 80-90 ° C for 2 hours. The suspension is filtered with a filtration rate = 0.021 cm / min. The filtrate is sent for further processing in order to isolate valuable components: magnesium, iron, aluminum, etc. An insoluble residue (cake 1) with a mass of 530 g, consisting of amorphous silicon dioxide and part of insoluble materials, is washed with hot water by repulpation and sent to electromagnetic separation in order to separate silica from chromites, magnetites, pyroxene and other minerals (mineral and chemical compositions of the insoluble residue dried at 105 ° C, before and after electromagnetic separation - see table 2-4).

Electromagnetic separation is carried out on a laboratory rotary separator equipped with special cassettes in which the separated mixture is divided into magnetic and non-magnetic products. After electromagnetic separation, the non-magnetic product is dried and packaged as a finished product.

Comparing Tables 2, 3, 4, it can be seen that the electromagnetic separation of cake 1 does not completely separate silica from undecomposed minerals and as a result does not provide high-quality silicon dioxide (for the quality of the finished product, see table 6).

In addition, the disadvantage of this technology is the very low filtration rate of the suspension (0.021 cm / min), the reason for which is the fine grinding of the initial ore mixture fed to leaching.

Example 2. 1000 g of serpentine ore mixture (composition see table 1) with a particle size of 2 mm is treated with a solution of sulfuric acid (volume of 3.7 l, a concentration of 42% H ₂ SO ₄ ). The suspension is filtered at a speed of 2.1 cm / min, the filtrate is sent for further processing in order to obtain Fe ³⁺ , Al ³⁺ , Mg ²⁺ oxides, and an insoluble residue (a mixture of amorphous silicon oxide, chromite and other minerals (see table. 2, 3)) weighing 480 g, are thoroughly washed from sulfates of iron, magnesium and other soluble salts, dried at 105 ° C and calcined at 550 ° C. After heat treatment, cake 1 is dissolved in caustic soda for 30 min at 70 ° C and t: g = 1: 4, to the NaOH content in the precipitated solution (suspension) - 49.0 g / L. The suspension is filtered, insoluble chromite concentrate is washed from impurities, dried and packaged. The filtrate is “liquid glass” with a concentration of 49.0 g / l NaOH precipitated with hydrochloric acid solution of 20% HCl at 70 ° C to a residual acidity in the mother liquor of 10.2 g / l HCl. The suspension is filtered with a filtration rate of 2.1 cm / min. The precipitated silica precipitate is washed with hot water with a volume of 2.1 times the volume of the filtered suspension. Then, the washed silica is dried at 105 ° C and calcined at 900 ° C. The quality of the finished product is given in table 5, 6.

Example 3. The mass, mineral, chemical and dispersed compositions of the ore mixture are similar to Project 2, the mixture is treated with 3.7 l of hydrochloric acid solution (concentration of 220 g / l HCl), the filtrate is sent for further processing in order to obtain Mg ²⁺ , Fe oxides ³⁺ and others, and an insoluble residue weighing 530 g is washed from magnesium chloride, iron and other soluble salts, dried at 105 ° C and fired at 600 ° C. Next, the insoluble residue is treated according to a scheme similar to pr.2.

The properties of silicon dioxide see table 5, 6. From table 5 and 6 it is seen that the leaching of the serpentine-chromite ore mixture is preferable to carry out a solution of sulfuric acid.

Example 4. The mass, mineral, chemical and dispersed compositions of the ore mixture, as well as the concentration of sulfuric acid and the firing temperature of cake 1 are similar to pr.2. The concentration of NaOH in the precipitated suspension was changed to 60.0 g / l NaOH, and the thoroughness of washing silica with hot water: the volume of washing water was 3.0 times the volume of the filtered suspension, after washing the suspension, the filter was repulped. As a result of this, silicon dioxide of maximum purity was obtained — SiO ₂ content = 99.97%.

Example 5-13 Leaching was carried out with sulfuric acid with various variations:

- firing temperature cake 1 - 300-700 ° C,

the concentration of NaOH in the precipitated suspension is 32.2-70.0 g / l,

- residual acidity of HCl - 1.0-16.0 g / l,

- the ratio of the volume of wash water to the volume of the filtered suspension is 1.0-3.0 + repulpation.

As can be seen from table 5:

1) the filtration rate of a silica suspension depends on:

- firing temperature of cake 1 (at a firing temperature below 350 ° C and above 600 ° C, the filtering speed decreases),

- NaOH concentration in the precipitated suspension (at a NaOH content below 40 g / l, the filtration rate is practically zero, using a suspension with a NaOH concentration above 60 g / l is not economically feasible);

2) the content of silicon dioxide in calcined silica at 900 ° C depends on the residual concentration of hydrochloric acid in the mother liquor (2-15 g / l HCl) after precipitation of silica and the volume of wash water, which should be 1.8-3 times the volume filtrate. The use of a suspension with a HCl concentration in the mother liquor above 15.0 g / l HCl is not economically feasible, and less than 2 g / l leads to a low content of silicon dioxide in the finished product and a high content of impurities (oxides Fe ³⁺ , Cr ³⁺ , Al ^{3 +} , Mg ²⁺ , Cs ²⁺ , etc. (see table 6)).

At a low filtration rate (op. 9, 10), a precipitate is practically not formed and the entire silica component remains in the mother liquor.

Table 1 Mineral and chemical compositions of serpentine-chromite ore mixture Name of minerals Soda% Name of components and their content,% Al ₂ O ₃ MgO SiO ₂ Fe ₂ O ₃ Cr ₂ O ₃ CaO MnO unaccounted for. 1. Serpentine 65.0 - 28.17 29.24 4.08 - - 1.95 - 2. Olivine (forsterite) 8.0 0.08 3.47 3.6 0.5 - - 0.16 - 3. Chromitis (chromicotitis) 10.0 1,5 1,0 0.05 2.5 5.98 - - - 4. Quartz 2.0 - - 2.0 - - - - - 5. Chlorite 6.0 1,02 1.8 1.8 0.72 - 0.3 0.12 - 6. Pyroxene 1,0 - 0.19 0.56 - 0.02 0.25 - - 7. RFP 8.0 - - - - - - - - TOTAL 100.0 2.6 34.63 37.25 7.8 6.0 0.55 2.23 8.94

table 2 The mineral composition of the insoluble residue (cake 1) Name of minerals Content% 1. Chrompicotitis (chromite) 18.9 2. Forsterite (olivine) 3.8 3. Pyroxene 1.9 4. Chlorite 11.3 5. Quartz 3.8 6. SiO ₂ amorph. 60.3 TOTAL 100.0

Table 3 The chemical composition of the insoluble residue (cake 1) Name of components Content in% 1. Cr ₂ O ₃ 11.3 2. SiO ₂ 70,4 3. Al ₂ O ₃ 2.05 4. Fe ₂ O ₃ 6.2 5. MgO 7.3 6. MnO 0.01 7. unaccounted for, ppp 2.74

Table 4 Mineral and chemical compositions of a non-magnetic product Name of minerals content% Name of components and their content in% SiO ₂ Al ₂ O ₃ CaO MgO Cr ₂ About ₃ Fe ₂ About ₃ MnO volatile and ignorant. H ₂ O 1. chlorite 1,0 0.25 0.22 - 0.16 - 0.31 - - - 2. chromicotitis 1,0 - 0.24 - 0.11 0.51 0.15 - - - 3. forsterite 0.5 0.21 - - 0.29 - - - - - 4. quartz 2.0 2.0 - - - - - - - - 5. X-ray amorphous phase 95.5 79.56 0.54 0.87 1.18 0.23 0.46 0.01 - - TOTAL 100.0 82.02 1,02 0.87 1.73 0.74 0.46 0.01 9.7 3.45

Table 5 Technological indicators of the process of separation of silicon dioxide from alkaline solutions No. of examples The firing temperature of cake 1, ° C The concentration of NaOH in the precipitated suspension, g / l The residual concentration of HCl in the uterine solution, g / l The rate of filtration of a suspension of silicon dioxide in sodium hydroxide, cm / min The ratio of the volume of wash water to the volume of the filtered suspension The content of SiO ₂ in the sediment,% dried at 105 ° C calcined at 900 ° C one The experiment was carried out using prototype technology. 2.0 82.0 89.43 2 550 49.0 10.3 2.1 2.6 93.92 99.57 3 600 40,0 10,2 1,6 2.6 91.26 98.29 four 550 60.0 15,2 2,3 3.0 + repulpation 94.36 99.90 5 500 70.0 2,3 2.24 2.0 90.1 96.6 6 400 59.8 13.6 2.0 2,4 92.5 97.4 7 350 53.6 10,4 1.35 3.0 + repulpation 86.4 91.26 8 300 55.0 15.8 0.88 3.0 + repulpation 50.15 58.64 9 600 32,2 4.0 0.05 - - - 10 550 55.0 1,0 2.1 1.8 78.6 82.3 eleven 500 54.1 16,0 2.0 1,0 80.2 85.6 12 700 50,0 15.0 1,1 3.0 + repulpation 88.1 93.51 13 600 60.0 16 2.5 3.0 + repulpation 95.1 99.97

Table 6 Physico-chemical properties of silicon dioxide calcined at 900 ° C Defined indicators No. of examples one 2 3 four 10 1. Mass fraction of SiO ₂ ,% 89.43 99.57 98.29 99,99 82.3 2. Mass fraction of moisture,% - - - - - 3. Mass loss on ignition - - - - - 4. Mass fraction of iron in terms of Fe ₂ O ₃ ,% 2.26 0.09 0.04 0.01 3.1 5. Mass fraction of aluminum in terms of Al ₂ O ₃ ,% 1,02 0,03 0.1 0.06 5.4 6. Mass fraction of chlorides or sulfates,% 2.49 0.02 0.08 0.02 2,3 7. Mass fraction of calcium-magnesium in terms of CaO,% 3.60 0.18 1.28 0.01 5.2 8. Mass fraction of chromium in terms of Cr ₂ O ₃ ,% 1,2 0.11 0.21 absent 1.7 9. Specific surface area by VET, m ² / g 56.0 341.0 327.9 351.0 12.0 10. pH of the aqueous extract 7.5 7.0 5.5 8.0 7.8

Claims (1)

A method of complex processing of magnesium-chromium-containing ore raw materials, including its decomposition with a solution of mineral acids, filtering the resulting suspension, processing the insoluble residue, neutralizing the filtrate with the precipitation of hydroxides of the metals contained in it, washing and drying the resulting final products, characterized in that the processing of the insoluble residue consists in roasting it at a temperature of 350-600 ° C, followed by dissolution in caustic soda with a residual alkalinity of 40-60 g / l NaOH, filtering the resulting suspension, about myvaniem residue - chromite concentrate - and the precipitation of silica in the resulting filtrate a solution of hydrochloric acid to a residual acidity of 2-15 g / l HCl.