RU2171220C1 - Method of agglomeration and granulation of phosphate raw material - Google Patents

Abstract

FIELD: mining industry. SUBSTANCE: invention relates to preparing fine natural- origin zirconium-containing phosphate raw material used in production of yellow phosphorus. Raw material is rolled in presence of complex correcting additive possessing simultaneously fluxing and binding capacities and containing following components, wt %: phosphoric oxide 30-40, sodium oxide 18-25, calcium oxide 10-14, magnesium oxide 0.5-8.0, aluminum oxide 2-3, ferric oxide 2-3, potassium oxide 0.2-3, silicon dioxide 0.3-1.0, fluoride 5-17, crystallization water - the balance. pH value of 1% aqueous suspension of additive ranges from 5 to 6.5. Additive is used in amount of 1 wt part per 3-8 wt parts of phosphate material. Rolled material is dried and resulting pellets are fired at 1150-1350 C. Additive can be prepared by neutralizing extraction phosphoric acid by soda ash or caustic soda to give Na₂O/P₂O₅ ratio providing pH value ranging from 4 to 5, after which suspension is separated into purified alkaline solution and solid phase used as complex correcting additive. The latter is advantageously utilized with 40-55% of hygroscopic water. EFFECT: enabled firing of zirconium-containing phosphate raw material at 1150-1350 C leading to yield of product fractions 95-96% and increased strength of final product to 19024 MPa. 3 cl, 2 tbl, 2 ex

Description

 The present invention relates to techniques for preparing finely divided natural phosphate feedstocks (apatites and phosphorites, as well as their concentrates) for processing to yellow phosphorus by the electrothermal method. The essence of preparation is the enlargement of small things as a result of its agglomeration, agglomeration and granulation.

 Numerous methods are known for agglomerating natural phosphate raw materials by rolling the latter in the presence of solid fuel, fluxing and binder additives, followed by ignition of the fuel and sintering of the mass. The disadvantage of these methods is the use of solid fuels (coke, coke, carbon shale, lean coal) for agglomeration of natural phosphate, during the combustion of which the environment is polluted with nitrogen, sulfur and carbon oxides.

 Known methods for preparing the little things of natural phosphates for processing into yellow phosphorus, not requiring the use of these types of solid fuels and consisting in agglomeration or granulation of the material. Methods of pelletizing and granulating phosphate raw materials include pelletizing the latter in the presence of fluxing and binder (corrective) additives, drying and roasting pellets (granules).

 For example, there is a known method of granulating phosphate raw materials (ed. Certificate of the USSR N 409728, class C 01 B 25/01), including mixing it with a binder, which is used as a slurry formed by treating phosphate raw materials with phosphoric acid, drying and calcining the resulting granules. The binder (corrective additive) consists of 69 - 74% of an insoluble residue (silicon dioxide), 20-25% of undecomposed fluoroapatite (calcium phosphate); aluminosilicates are also present.

 The disadvantage of this method is the low efficiency of granulation when using a binder, consisting mainly of water-insoluble materials, and, as a result, the insufficient strength of the granules and the low yield of the commercial fraction (pieces of size 5-50 mm).

A known method of agglomeration of phosphate material (ed. Certificate of the USSR N 1692933, class C 01 B 25/01), according to which it is provided: 1) pelletizing (pelletizing) (phosphate raw materials in the presence of corrective additives (fluxing and binder materials, as limestone, dolomite, lime burnout, quartzite or silicon are used); 2) drying, 3) pellet firing in a rotary tube furnace at a gas-coolant temperature of 1200 - 1400 ^o C. The yield of a commercial fraction due to the optimization of the apparatus and technology process (application of a rotary tube furnace and regulation of heat transfer between gas and material) reaches 93-94%. The disadvantage of this method is the difficulty that arises when maintaining the required temperature gradient between the coolant and the material and the need to introduce additives of various compositions depending on the fixed temperature gradient. In addition, the process allows in the specified temperature range to process only fusible phosphate raw materials - phosphorites.

The closest in technical essence and the achieved result to the claimed is the process described in ed. testimonial. USSR N 575805, class C 01 B 25/01. In this method of granulation of phosphate raw materials (including refractory apatite flotation concentrate of the Kovdor deposit, which includes zirconium-containing minerals, for example, baddeleyite - ZrO ₂ ), including rolling phosphate raw materials in the presence of a corrective additive, which is used as a natural mineral shungite (containing dioxide silicon, aluminosilicate, carbon), drying and firing the granules at a temperature of 1150-1350 ^o C, achieve a product yield of 93%, with the strength of the granules 13.7 MPa. The latter is due to the fact that the upper limit of the amount of introduced shungite is 10% of the mass of phosphate raw materials (or 1 part by weight of mineral per 10 parts by weight of Kovdor apatite), otherwise the burning out (oxidation) of excess carbon can lead to recovery and loss phosphorus during firing.

 The aim of the present invention is the implementation of the pelletizing and roasting of zirconium-containing phosphate raw materials in the presence of a larger amount of corrective additives, providing accordingly higher strength of the granules with a yield of commodity fraction reaching 95 - 96%.

The goal is achieved according to the present invention by the fact that in the known method, including the rolling of zirconium-containing phosphate raw materials in the presence of corrective additives - compounds of silicon, calcium, magnesium, phosphorus and sesquioxides, drying and firing of granules at a temperature of 1150 - 1350 ^o C, rolling of phosphate raw materials carried out in the presence of a complex corrective additives that have both fluxing and binder effect and containing the following components, wt.% in terms of: phosphorus oxide (V) 30-40, oxide on Riya 18 - 25, calcium oxide 10 - 14, magnesium oxide 0.5 - 8.0, alumina 2 - 3, iron oxide (III) 2 - 3, potassium oxide 0.2 - 3.0, silicon dioxide 0, 3 - 1.0, fluorine 5-17, as well as crystallization water up to 100%, providing a hydrogen index of a 1% aqueous suspension of the additive in the range of 5 - 6.5 units. pH, and taken in the ratio of 1 wt. including additives for 3 to 8 wt. including phosphate raw materials.

In the claimed technical solution, the following additional novelty elements are provided, indicating a priority option for the synthesis of a complex corrective additive, as well as enhancing the usefulness of the technology with respect to its use: 1) obtaining a complex corrective additive by neutralizing extraction phosphoric acid with calcined or caustic soda to a Na ₂ O ratio: P ₂ O5, providing the value of the hydrogen index of the suspension in the range of 4 to 5 units. pH, followed by separation of the latter into purified liquor and solid phase, used as a complex corrective additives; 2) the use of the latter when the content of hygroscopic water in it is equal to 40 - 55 wt.%.

 Thus, the main differences of the proposed method from the known one consist, firstly, in the rolling of zirconium-containing phosphate raw materials in the presence of a synthetic complex corrective additive, which simultaneously has a fluxing and binding effect and containing phosphates of sodium, potassium, calcium, magnesium and fluorine compounds, which when The claimed concentrations provide a hydrogen indicator of a 1% aqueous suspension of the additive in the range of 5-6.5 units. pH, instead of a natural mineral - shungite, consisting of silicon dioxide, aluminosilicates and carbon, and, secondly, in a larger proportion of the added additive relative to natural phosphate (12.5 - 33% compared to 10.0% of the prototype) . In the table. 1 compares the characteristics of additives used in various processes.

The use of the claimed complex corrective additives in the amount of 1 wt. hours for 3-8 parts by weight phosphate raw materials is particularly useful and effective in the agglomeration and granulation of refractory zirconium-containing raw materials, for example Kovdor apatite concentrate or its mixtures with other types of phosphate raw materials. Studies have shown that the melting temperature of such a material can be reduced by 250 - 350 ^o C (see table. 2), which will allow for the agglomeration of raw materials at temperatures not exceeding 1350 ^o C, due to the presence in the additive of alkali metals and fluorine compounds in accordance with selected concentrations and ratios of components at which the effect of mutually reinforcing fluxing effect is ensured.

 Acting as binding components of calcium, magnesium, aluminum and iron salts, it is possible to increase the strength of the agglomerated material in the claimed ranges of changes in their content to 19 - 24 MPa.

As follows from the data given in table. 2, with an increase in the amount of apatite over 8 parts by weight per 1 part by weight complex corrective additives, the sintering temperature of the raw material exceeds a value of 1350 ^o C and increases sharply at 9 wt. hours to 1720 ^o C; at the same time, the strength of the granular material decreases by ~ 2 times. At the same time, a decrease in the mass fraction of apatite in the feed mixture to 66% (2: 1 ratio) is undesirable due to the negative effect of the increased amounts of the individual components of the complex corrective additives on the subsequent electrothermal processing of phosphate raw materials into yellow phosphorus (the appearance of fluorine and silicon, increased wear of the lining of the ore-thermal furnace, an increase in phosphorus losses with slag, etc.). The decrease in the content of fluxing and binder components in the additive below the stated concentration limits also does not allow to achieve the goal for the agglomeration temperature corresponding to the range 1150 - 1350 ^o C. In the examples 6, 11, 16 of the table. 2 these values are 1415 - 1480 ^o C. The increase in the content of individual components in the additive in excess of the optimal (examples 2, 7, 12 of table. 2) is not rational due to the practical absence of an additional positive effect on temperature and strength. The noted negative factors for the processing of agglomerated raw materials are exacerbated.

One of the main indicators of the patented technological process is the use of a complex corrective additive of a salt composition that meets not only the range of the component (mainly oxide) composition given by the formula, but also provides the required hydrogen index of a 1% aqueous solution of the additive of at least 5 units. pH and not higher than 6.5 units pH This is due to the requirements for the operation of electrothermal furnaces. Acidic additives are undesirable due to the increased vapor pressure of SiF ₄ during phosphorus reduction; alkaline additives are dangerous because the furnace lining is intensively washed out when applied.

A complex corrective additive can be synthesized by mixing phosphate salts of alkali and alkaline earth metals (including crystalline hydrates), iron and aluminum phosphates, hexafluorosilicates and fluorides of these metals. The multicomponent nature of the system, combined with the imposition of restrictions not only on composition but also on the magnitude of the hydrogen index, determines the complexity of the synthesis process. At the same time, the authors found that a solid phase formed by neutralizing extraction phosphoric acid with calcined or caustic soda to a ratio of Na ₂ O: P ₂ O ₅ , providing a pH value of the suspension in the range of 4–5 units, can be used as the indicated additive. . pH The impurities contained in the extraction phosphoric acid are precipitated during neutralization in the form of calcium, magnesium, iron, aluminum, silicofluoride phosphates, and during their subsequent separation, for example, by filtration, the precipitate also contains a liquid phase, which is represented by sodium phosphates.

 At the indicated neutralization pH, the salt and component composition of the wet sediment obtained on the basis of extraction phosphoric acid from apatite concentrates from the Kirov and Kovdor deposits most fully meet the declared concentration limits and the acidity range of the additive. The purified liquor formed after separation of the wet cake (complex corrective additive) is a solution of sodium dihydrogen phosphate, which can be processed into sodium ortho- and polyphosphates by known methods. For example, sodium tripolyphosphate or trisodium phosphate according to the processes described in the patent application of the Russian Federation N 95114712/12, cl. 6 C 01 B 25/41, declared 03/15/95, FIPS decision on the grant of a patent dated 06/18/99; RF patent N 2148010, CL 7 C 01 B 25/41; RF patent application N 95114710/12, cl. 6 C 01 B 25/30, declared 08/15/95; FIPS decision on the grant of a patent dated 06/18/99; RF patent N 2147552, cl. 7 C 01 B 25/30, declared 12/17/98.

To ensure uniform distribution of the components of the complex corrective additives in the mass of phosphate raw materials, it is possible to use the latter with a hygroscopic water content of 40 - 55%. When the content of H ₂ O gig. less than 40% uniformity of mixing is ensured only with intensive intervention of the additive in phosphate raw materials. When the content of H ₂ O gig. 55.0% uniform distribution of components is achieved easily due to the thixotropy of the system. An increase in water content is not required, especially since this is associated with additional fuel costs during drying and firing.

 To specify the technology in addition to the table. 2 provide examples of the process according to the claimed method in an industrial installation.

 Example 1

9 t / h of finely dispersed flotation concentrate of apatite-baddeleyite ore of the Kovdor deposit (Russia), containing (wt.%): P ₂ O ₅ - 37.3; CaO 49.4; CO ₂ - 3.5; MgO - 1.3; F is 1.0; Al ₂ O ₃ - 0.8; Fe ₂ O ₃ - 0.5; SiO ₂ - 0.5 is mixed with 3.4 t / h of sand (94.4% SiO ₂ ) and 2.9 t / h of a complex correction additive containing 42% H ₂ O. The ratio of phosphate raw material: dry weight of the additive 4.62: 1. The additive is composed of the following components (% wt. In terms of dry matter): oxide (phosphorus (V) - 31.4; sodium oxide - 20.3; calcium oxide - 12.8; magnesium oxide - 4.1; aluminum oxide - 2.3; iron (III) oxide - 2.7; potassium oxide - 2.0; silicon dioxide - 0.4; fluorine - 16.5; crystallization water - 7.5. 1% aqueous solution at the same time 5.3 pH units Estimated (with an accuracy of 2%) salt composition the corrective additive is as follows: sodium dihydrogen phosphate - 18.6%, calcium hydrogen phosphate - 15.5%, magnesium hydrogen phosphate - 6.3%, iron hydrogen phosphate - 6.7%, aluminum hydrogen phosphate - 7.7%, sodium fluoride - 21%, calcium fluoride - 8.9%, magnesium fluoride - 3.1%, potassium fluoride - 2.5%, silicon dioxide - 0.4%, as well as crystallization water - 7.5%. 3 t / h are doused in a drum or plate granulator or twin-shaft auger mixer. Next, the granulate is fed into a rotary tube furnace, where it passes into the sub-melting and agglomeration zone by heating the mixture to a temperature of 1260 ^o C with a counter-flowing gas (1300 - 1400 ^o C).

As a result of water evaporation and decarbonization, 13.8 t / h of phosphate material are obtained with a content (wt.%): P ₂ O ₅ - 28.2; CaO 33.5; SiO ₂ 22.8; Al ₂ O ₃ - 0.90; Fe ₂ O ₃ - 0.70; MgO - 1.4; F 2.9; Na ₂ O - 2.8; K ₂ O - 0.28. The agglomerated material is cooled and classified. The yield of the conditioned material of a fraction of 5–50 mm is 95% with a granule strength of 21 MPa.

 Example 2

The process of agglomeration and granulation is carried out, as described in example 1, with the only difference being that a complex corrective additive containing 50% H ₂ O is used in an amount of 3.4 t / h (the composition on a dry substance is similar to example 1). In this case, the additive is prepared as follows. 9.1 t / h of extraction phosphoric acid (27% P ₂ O ₅ ) are neutralized in two steps with soda ash (98% Na ₂ CO ₃ ) taken in an amount of 3.12 t / h. At the first stage serves 2.1 t / h of soda, providing a pH value of suspension equal to 4.8 units. pH At a temperature of 80 ^o C for 60 min from extraction phosphoric acid 1.2 t / h of precipitate consisting of calcium phosphates, magnesium and sesquioxides, sodium hexafluorosilicates and potassium, as well as silicon dioxide. The precipitate is filtered under a pressure of 0.7 MPa, repulped in water, filtered for the second time and get 3.4 t / h of a complex corrective additives (total humidity 65%) containing, in addition to the above compounds, dissolved sodium phosphate. 9.0 t / h of purified liquor (21% P ₂ O ₅ ) in the second stage are treated with the remaining 1.02 t / h of soda to a pH of 6.8, impurities that are not precipitated by the wound are separated and transferred to the first stage. The result is 9.5 t / h of purified second-stage liquor containing 19.5% P ₂ O ₅ . Removing water by evaporation, drying and calcination at 300 - 400 ^o C get 3.28 t / h sodium tripolyphosphate (56.5% P ₂ O ₅ ). In the process of agglomeration and granulation, 13.8 t / h of phosphate material with a strength of 20.8 MPa is formed. The yield of the conditioned fraction (5-50 mm) is 95.2%.

Example 3. 6.1 t / h of finely dispersed flotation concentrate of apatite-baddeleyite ore of the Kovdor deposit (for the composition see Example 1) is mixed with 6.1 t / h of finely dispersed flotation concentrate of phosphate rock of Kingisepp deposit (Russia) containing (wt.%): P ₂ O ₅ - 28.3; CaO - 43.0; CO ₂ - 6.0; MgO - 2.1; F - 2.8; Al ₂ O ₃ - 1.0; Fe ₂ O ₃ - 1.0; SiO ₂ - 12.0. The resulting mass is then mixed with 3.5 t / h of sand (94.4% SiO ₂ ) and 4.0 t / h of a complex corrective additive containing 50% H ₂ O. The ratio of zirconium-containing phosphate raw materials: dry weight of the additive in this case 3, 05: 1. The composition of the anhydrous part of the additive is similar to example 1. The mixture in an amount of 19.7 t / h is doused and fed into a rotary tube furnace, where it passes into the melting and agglomeration zone by heating the mixture with a counter-current gas supplied with a heat carrier (1300 - 1400 ^o C) to a temperature 1250 ^o C. As a result of water evaporation and decarbonization, 17.1 t / h of phosphate material are obtained with a content (wt.%): P ₂ O ₅ - 27.1; CaO 34.6; SiO ₂ 23.7; MgO - 1.7; F is 3.3; Al ₂ O ₃ - 1.0; Fe ₂ O ₃ - 0.91; Na ₂ O - 2, 4; K ₂ O - 0.23. The agglomerated material is cooled and classified. The yield of a conditioned product of a fraction of 5-50 mm is 96% with a piece strength of 23 MPa.

Thus, the claimed technical solution allows firing of zirconium-containing phosphate raw materials at a temperature of 1150 - 1350 ^o C instead of 1500 - 1700 ^o C with a yield of commodity fraction of 95-96% and the strength of the finished product 19 - 24 MPa.

Claims (3)

 1. The method of sintering and granulation of zirconium-containing phosphate raw materials, including sizing of the latter in the presence of corrective additives - compounds of silicon, calcium, magnesium, phosphorus and sesquioxides, drying and firing of granules at a temperature of 1150 - 1350 ° C, characterized in that the sizing of phosphate materials is carried out in the presence of a complex corrective additive having both a fluxing and binding effect and containing components, wt.% in terms of phosphorus oxide (V) 30-40; sodium oxide 18-25; calcium oxide 10-14; magnesium oxide 0.5 to 8.0; alumina 2 to 3; iron oxide (III) 2 to 3; potassium oxide 0.2 to 3; silicon dioxide 0.3 to 1; fluorine 5-17, as well as crystallization water up to 100%, providing a hydrogen index of a 1% aqueous suspension of the additive in the range of 5-6.5 units. pH, and taken in the ratio of 1 wt.h. additives for 3 to 8 parts by weight phosphate raw materials. 2. The method according to claim 1, characterized in that the complex corrective additive is obtained by neutralizing the extraction phosphoric acid with calcined or caustic soda to a ratio of Na ₂ O: P ₂ O ₅ , providing a pH of the suspension in the range of 4 to 5 units. pH, followed by separation of the latter into purified liquor and solid phase, used as a complex corrective additives.  3. The method according to claim 1 or 2, characterized in that the complex corrective additive is used with a content of absorbent water equal to 40-55 wt.%.

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