SU1731764A1 - Method of producing double superphosphate - Google Patents

Abstract

The invention relates to methods for the processing of phosphorus raw materials and improves the quality of mineral fertilizer by increasing its PaOs content, obtaining ammonium phosphate, expanding the raw material base for the production of double superphosphate. According to the invention, the decomposition of phosphate raw materials is carried out in two stages, where the invention relates to methods for the processing of phosphate raw materials by acid methods and can be used in industry for the production of phosphorus-containing mineral fertilizers. A known method for producing phosphorus-containing mineral fertilizers. Including obtaining in the first stage of primary phosphate raw material extraction phosphoric acid (EPA), decomposition of the secondary phosphate raw material in the second first stage is decomposed with sulfuric acid in the presence of a working solution to obtain extraction phosphoric acid and gypsum. The obtained phosphoric acid extraction is directed to the second stage of phosphate raw material decomposition, followed by the separation of phosphogypsum and further granulation and drying of the resulting pulp. A phosphate-acid solution containing mono-substituted calcium phosphate and phosphoric acid is used as a circulating solution in the first stage. In order to obtain ammonium phosphate, the phosphate-acid solution after filtration is subjected to ammonization. In order to obtain double superphosphate before the separation of phosphogypsum, 20-40% of phosphate raw material is supplied from its total demand in the second stage of decomposition. To expand the raw material base, phosphorites with a P20 content not exceeding 24.5% are used at both stages of the process. When using phosphate rock with a P20s content of not more than 24.5%, a product with a P20 content of 44.3% is obtained. 1 hp f-ly, 2 tab. stages of phosphoric acid in the presence of sulfuric with a mass ratio of H2S041 P20s of phosphoric acid, equal to (0.1-0.5): 1, and a mass ratio of HzP04: 2) CaO, MoO, PsOz in phosphate, equal to

Description

37.4%) R20busv content. in the processing of phosphate raw materials 24.5% PaOs. If phosphorites containing less than 24.5% PaOs are used, the nutrient content of the fertilizer is less than 28%.

The closest in technical essence and the achieved result to the invention is a method of obtaining phosphorus-containing mineral fertilizers, including a two-stage decomposition of phosphate raw material: in the first stage sulfuric acid in the presence of a circulating phosphoric acid solution to produce an EPA gypsum and gypsum, separation of an EPA from gypsum, decomposition in the second stage of phosphate raw material, the obtained EPA, granulation and drying of the finished product.

The disadvantages of the method are: low content of P20bus. (43.6-44.5%) in the finished product, high demands on the raw phosphate raw materials containing in the first phase 30-39% P20s (apatite concentrate) and 28% P20s per of the second stage (Kingisep phosphorite), when using Karatau phosphorite at both stages of the process (P20v content Ј 24.5%), the finished product contains less than 37% P20 bus, which requires an increase in energy consumption for its production, transportation and introduction into the soil .

The purpose of the invention is to increase the content of P20s in the finished product.

The goal is achieved by the fact that in the method of obtaining phosphorus-containing mineral fertilizers, including two-stage decomposition of phosphate raw materials: in the first stage with sulfuric acid in the presence of a working solution with obtaining EPA and gypsum, separation of EPA from gypsum, decomposition of phosphate raw materials in the second stage of the obtained EPA, granulation and drying the product, decomposing the phosphate raw material of EPA in the second stage begins before separating EPA from gypsum using in the first stage as a circulating washing phosphate-acid solution, containing monocalcium phosphate and phosphoric acid, and in preparing double superphosphate-type fertilizer, the phosphate raw material supplied before the phosphogypsum separation is taken in the amount of 20-40% of its total demand in the second stage and the decomposition of the remaining part of the secondary phosphate with the phosphate-acid solution after the gypsum is continued: when producing fertilizer of the type of ammonium phosphate, the entire amount of the secondary phosphate raw material decomposes EPA before the separation of the gypsum and the phosphate-acid solution obtained after filtration is subjected to ammonization . Conducting the process by the proposed method makes it possible to obtain mineral fertilizers with the content of P20busv. 48.2-51.7%, when using phosphate raw materials with the content of 39.4% P20s in the first stage and 28% P20s in the second, and when using phosphate in both stages

raw materials with a content of 24.5% PaOs and / or at the second stage in the preparation of ammophosphate 21% P20s — fertilizer with a P205usv content. not less than 44.3%.

The use of working solution

free of monophosphates, leads to the fact that in the production part of the solution supplied for further processing, free sulfuric acid is contained, which in subsequent stages leads to

the formation of sulfates in the final product and a decrease in the P20s content in fertilizers.

When phosphate raw materials are introduced before the separation of phosphogypsum upon receipt of double superphosphate in an amount of more than 40%, the loss of P2Qs increases due to the supersaturation of the pulp with calcium monophosphate, which leads to its crystallization and separation together with phosphogypsum.

When phosphate raw materials are introduced before the phosphogypsum is removed in an amount of less than 20%, free sulfuric acid remains in the working solution and the P20s content in the final product decreases.

EXAMPLE 1.1000 kg of apatite with a content of 39.4% P20s are treated in the first stage with 988 kg of 93% sulfuric acid and 3143 kg of a working solution containing 560 kg of P20s, including 519 kg of P205 release. and

31 kg of P20s in the form of monophosphates. The result is 4842 kg of extraction intermediate pulp containing 954 kg of P20s (in the form of NZROz of 946 kg and 8 kg in undecomposed apatite), 1600 kg of phosphogypsum,

77.8 kg of free sulfuric acid. Prior to the separation of phosphogypsum, 201 kg (28% P20b) of the Kingisep flotation concentrate is fed into the obtained intermediate extraction pulp, which is 40.0% of

the total amount (507.5 kg) of the flotation concentrate supplied to the process, containing 56 kg of R20b, 26 kg of insoluble residue, 10 kg of CO2. The decomposition time of the first part of the secondary phosphate raw material is 1 h 40 min.

The resulting pulp in the amount of 5007 kg, having the composition: R20 total. 1010 kg, including Р20bsvorb. 945.7 kg, Pads in monophosphates 55.3 kg, P2U5 not decomposed 9 kg, gypsum 1762.5 kg, in the absence of free sulfuric acid

the acids are separated on a filter, washing the resulting cake.

The result is 1504 kg of a phosphate-acid solution containing 24 kg of P20b in the form of monophosphates and 400 kg of P205 liberated, 1820 kg in terms of the dry matter of phosphogypsum with undecomposed part of the flotation concentrate and 3143 kg of working solution (solution after washing) containing 31 kg of P20s in the form of monophosphates and 529 kg of RaOfree, which is fed to the head of the process.

Phosphogypsum is removed from the process, and the phosphate-acid solution is treated with the remaining 306.5 kg (from 507.5 kg) of flotation concentrate.

The decomposition time of the second part of the secondary phosphate raw material is 2 hours. As a result, 1764.5 kg of phosphate pulp of the following composition is obtained: Pa total. 510.1 kg; Р20бсвы. 164.3 kg, P20b in monophosphates 311.3 kg, P20s nerazlozhivshey 34.5 kg, insoluble residue 40 kg, moisture-containing 47%.

The obtained phosphate pulp is dried and granulated in a drum dryer-granulate at a product temperature at the outlet of the drum 130 ° C. The result is 950 kg of the finished product containing 510.1 kg (53.7%) of P205 total, 491.6 kg (51.7%) of P20 bus, including 38.6 kg (4.0%) of P20 free.

Example 2. Under conditions analogous to example 1, phosphorus-containing fertilizer is obtained, changing the amount of secondary phosphate raw material fed before the phosphogypsum separation.

The effect of these changes on the quality of the fertilizer is presented in Table. one.

Analysis of the tabular data shows that at the rate of phosphate feed in the second stage before the separation of phosphogypsum in an amount of less than 20 wt.%, Sulfuric acid is present in the working solution (experiments 5, 6), which leads to a decrease in P20s in the final product. At a rate of more than 40% (experiment 1), the loss of PaOs sharply increases. At the beginning of the decomposition of the phosphate raw material in the second stage after the separation of phosphogypsum (Example 6), the content of P20s in the product decreases. Thus, it can be concluded that the optimal rate is 2040% of phosphate raw material introduced before the phosphogypsum is removed in the second stage.

Froze Under the conditions analogous to example 1, fertilizer is obtained, feeding into both phases for decomposition the Karatau phosphorites containing not more than 24.5%

P205.

The research results are summarized in table 2.

When used at both stages of decomposition of Karatau phosphorites with a PaOs content of not more than 24.5%, a double superphosphate product with a P2U5 content of 44: 3% (examples 2 and 1) is obtained, which corresponds to or exceeds the product by a known method.

The implementation of the proposed method in the industry will improve the quality of phosphorus-containing fertilizer due to

increasing the content of PtzOs. In addition, the withdrawal of part of the ballast (CaS04 and the insoluble residue) resulting from the introduction of phosphate raw materials in the second stage reduces the energy consumption at the granulation stage and

reduces the abrasiveness of ammophosphate pulp.

Claims (2)

1. A method of producing double superphosphate, including decomposition of the primary phosphate raw material with sulfuric acid in the presence of a working solution to obtain phosphoric acid and phosphogypsum, decomposition of the secondary phosphate raw material formed by extraction phosphoric acid, granulation and drying of the product, characterized in that, in order to increase the P20s content in the finished product, the secondary phosphate raw material is fed to the decomposition in the amount of 20-40% of its total consumption, decomposition is carried out in the presence of phosphogypsum, followed by separation of the resulting pulp into phosphogypsum and phosphate-acid solution, washing of phosphogypsum and supply of washing water to a step of decomposing the primary raw material as a working solution and treating the remaining secondary raw material with a phosphate-acid solution. 2. Method pop. 1, characterized in that phosphate materials with a P20s content of not more than 24.5% are used as the phosphate raw material. Table 1 table 2