SU1701628A1 - Method of producing extraction phosphoric acid - Google Patents

Abstract

This invention relates to a method for extracting phosphoric acid from carbonate-containing phosphates used in the manufacture of mineral fertilizers and other phosphate salts. The aim of the invention is to increase filtration performance and reduce the consumption of sulfuric acid. Phosphoric acid The invention relates to a process for the production of extraction phosphoric acid from carbonate-containing phosphates used in the manufacture of mineral fertilizers and other phosphate salts. The aim of the invention is to increase filtration performance and reduce the consumption of sulfuric acid. PRI me R 1. 1000 may. including phosphorite Karatau containing, wt.%: dolomite 11,5; quartzite 6, fluorocarbonatapatite 56.7

Description

phosphate raw material having a composition, wt.%: diopside 11.7; fluorapatmt 58.9; calcium and magnesium oxides 1,3 (38.6 CaO; 2.7 MdO; 22.1 P205; 6.5 SI02).

This phosphate raw material is treated by heating (70-90 ° C) with a mixture of 327 wt.h. 93% sulfuric acid (the norm is 90% of stoichiometry for the binding of all CaO phosphate raw material, which was received at the extraction stage) and 1218 wt.h. circulating phosphoric acid concentration of 20% PaOs. The resulting suspension of phosphogypsum in phosphoric acid (2492 parts by weight, 5: 1) is filtered, the precipitate is washed on the filter 757 parts by weight water and separated 890 wt.h. wet (40%) precipitate of calcium sulfate dihydrate, 384 wt.h. production acid concentration of 28% PaOb (the degree of recovery of PaOs in the liquid phase is 97.5%). At the stage of acid decomposition of phosphate raw materials return 1218 wt.h. phosphoric acid concentration of 20% PaOs. In the gas phase extraction process, 310 parts by weight of water vapor is removed. Filtration capacity is 2.5 t / m -h.

According to a known method, extraction phosphoric acid is obtained by heat treatment of phosphate raw materials containing fluorine, iron and aluminum and melting at 1300-1400 ° C, 150-200 ° C below its melting point, followed by treatment with circulating phosphoric and sulfuric acids with the formation of a suspension, filtration with isolation of the product, washing the precipitate of calcium sulfate and the direction of the wash water to the acid treatment. By this method, raw materials of the following composition are processed,%: PaOs 18, CaO 27 Md 0.78; Si02 38, After calcination, the amount of diopside produced is 3.2%, which does not help to reduce the consumption of sulfuric acid (it is stoichiometric to bind all the calcium oxide contained in the raw material), and a significant increase in filtration capacity, which is 1.4-1.8 t / m2-h. If it is assumed that all of the silica contained in the raw material is active, its consumption for the binding of dolomite exceeds 1600% of stoichiometry. In this case, the process indicators are reduced due to the abrasive effect of quartzite on phosphogypsum.

According to the invention, during heat treatment of phosphate raw materials containing dolomite, calcium and active silica, diopside is formed.

CaMd (SOZ) 2 + 28Ю2 (act)

CaMg (Si20e) + 2C02t (1)

Diopside is an acid resistant mineral. The temperature range of the heat treatment is due to the fact that 900 ° C is the minimum thermal dissociation temperature of the carbonate components of the raw material, 1300 ° C is the beginning of diopside melting.

The presence of diopside in phosphate pulp allows it to be filtered with high productivity, which is illustrated in the table. one,

As can be seen from the table. 1, with an increase in the amount of diopside from 5 to 20% in the phosphate raw materials fed to the extraction, the filtering properties of the suspensions improve 1.15-1.5 times, as in the case of phosphoric acid (experiments 1-5 and 11-15), and in the case of sulfur phosphoric acid (experiments 6-10 and 16-20) decomposition of phosphate. This is due to the formation of a coarse-crystalline substrate from diopside insoluble in acid, which makes it possible to dissociate even a practically non-filtering suspension of dicalcium phosphate with satisfactory indicators. During the crystallization of phosphogypsum, the positive effect of diopside on the filtering properties is sharply enhanced: with a content of 5–20 wt.% Diopside, the filtration performance increases by 2.7–4 times, a further increase in the proportion of diopside to 30% leads to a decrease in filtration performance, which is due to the abrasive action of diopside particles. In this case, the greatest reduction in the consumption of sulfuric acid is achieved (the rate of sulfuric acid decreases by 1.2 times).

Silicon dioxide is present in phosphate raw materials in the form of acid-soluble (forsterite, opal, chalcedony, cristobalite, etc.) and acid-insoluble minerals (pyroxenes, quartz, quartzite, feldspar, etc.). The mineral composition of the raw material is also now unambiguously determined by quantitative X-ray fluorescence and X-ray phase analysis. The active form of silica is quartzites and phosphate-siliceous rocks.

In tab. 2 shows data on the effect of consumption of active silica on process indicators,

As can be seen from the table. 2, the optimal quartzite content in the initial magnesium carbonate-containing phosphorus is 100–200% of stoichiometry for the binding of dolomite to diopside. When the SI02 rate is reduced to 80%, the filtering properties deteriorate (1.5–1.7 times) This is due to the presence in the raw material after preliminary heat treatment of km of calcium and magnesium oxides, which are formed as a result of thermal dissociation of dolomite, but not bound to diopside. Exceeding the quartzite norm by more than 200% of stoichiometry for binding 5 dolomite to diopside is accompanied by a decrease in filtration performance, which is explained by the abrasive action of quartzite,

PRI mme R 2. 1000 ma.ch. phosphorite 10 Karatau containing 27% dolomite, 16% quartzite and 51% fluorocarbonate apatite (5.9% MgO, 37.6 CaO P205, 16) is mixed with 192.2 ma.ch. of quartzite (to obtain the rate of active silica 15 equal to 200% of the stoichiometry for the binding of the carbonate component to diopside) and subjected to preliminary heat treatment at 1300 ° C for 0.1–0.2 hours. the phase is 20- 152.2 ma.ch.h. carbon dioxide, and 1040 mac. a cake containing 30.5% diopside, 16.9% quartzite and 46.8 fluorapatite (5.6% MgO; 36.1% CaO; 17.9 P205; 16.9% Si02) is crushed and to the 25th wish, after which 500 May. including a small (8 (5) -0 mm) fraction of the agglomerate is directed (to obtain EPA as a starting phosphate raw material. This phosphate raw material is processed by heating (70-3090 ° C) with a mixture of 265.9 wt.h. 93 % sulfuric acid (the norm is 80% of the stoichiometry for the binding of all CaO phosphate raw materials received for extraction) and 1750 masses of circulating phosphoric acid concentration of 35% P20s 2515.9 masses of the resulting suspension of phosphogypsum in phosphoric acid (5: 1) filtered, washed precipitate

1054.7 ma.ch. water and separated 1167 wt.h.

wet (40%) precipitate of calcium sulfate dihydrate 40, 363.5 wt.h. production acid concentration of 24% P20s (the degree of extraction of P20s into the solution is 97.5%). At the stage of acid decomposition of raw materials return 1750 wt. H. phosphoric acid 45 concentration of 18% P20b. The extraction process removes 290 mash into the gas phase. water vapor. Filtration capacity is 1 3 t / m -h.

Example 3..1000 mah. phosphorite 50 Karatau containing May. %: dolomite 11.5; fluorocarbonatepatitis 56.7; quartzite 8 (20.3 P20s, 35.5 CaO; 2.5 MdO; 8 SiOa). subjected to preliminary heat treatment at 900 ° C for 0.5 h to convert 55 dolomite and quartzite (the rate of active SiO2 in the feedstock is 105% of stoichiometry

for the binding of dolomite to dioxide) to acid-insoluble dioxide. At the same time, decarbonization of fluorocarbonate-apatite proceeds at the same time. As a result, 135 wt.h. 80 wt.h. carbon dioxide The obtained sinter (920 parts by weight) is subjected to crushing and screening, fractions 8 (5) - О mm (500 parts by weight) are sent to obtain EPA as a feedstock, having in its composition, wt.%: dioxide 14.7; fluoropatite 58.9 (22.1 P2U5; 38.6 CaO 2.7 MdO; 8.6 SiOa). This phosphate raw material is treated by heating (70-90 ° C) with a mixture of 327 wt.h. 93% sulfuric acid (the norm is 90% of stoichiometry for the binding of total calcium oxide supplied with raw materials) and 1218 May, h. treated phosphoric acid concentration of 20% P20s. The resulting suspension of phosphogypsum in phosphoric acid (2492 parts by weight, 5: 1) is filtered, the precipitate is washed on the filter 757 parts by weight water and separated 890 wt.h. wet (40%) sediment dihydrate calcium sulphate and 384 wt.h. production acid concentration of 28% P203 (the degree of extraction of P2Os in the liquid phase is 97.5%). At the stage of decomposition of raw materials return 1218 wt.h. phosphoric acid (20% P20s). In the process of decomposition into the gas phase, 310 wt.h. water vapor.

Filtration capacity is 4.2 t / m -h.

Claims (2)

Invention Formula 1, A method for producing phosphoric acid from carbonate-containing phosphate raw materials, including heat treatment, subsequent processing of circulating phosphoric and sulfuric acids, crystallization of calcium sulfate dihydrate precipitate, separating the product from the precipitate by filtration, washing it and sending the wash water to the treatment as working phosphoric acid, characterized in that. In order to increase filtration performance and reduce the consumption of sulfuric acid, heat treatment is carried out at 900-1300 ° C in the presence of silicon dioxide, taken in the amount of 100-200% of stoichiometry for the binding of carbonates - dolomite and calcite to diopside. 2. A method according to claim 1, characterized by heme, which takes quartzite or siliceous phosphate rocks as silica. Table I The effect of diopside in phosphorite after preliminary heat treatment on the consumption of sulfuric acid and the filtering properties of phosphogypsum upon the production of extraction phosphoric acid at 70-90 ° С (SiOa content in the form of quartzite in the initial phosphate is 150% of stoichiometry for binding dolomite to diopside) The effect of Si02 content in the form of quartzite in the initial phosphate on the filtering properties of phosphogypsum in the preparation of EPA at 70-90 ° C (the SiOa content in the raw material is 12.8%) table 2 Continuation of table 2