SU1439092A1 - Apatite processing method - Google Patents

Abstract

The invention relates to methods for the processing of apatite by its acid decomposition with the production of complex fertilizers such as nitrophosphate. The aim of the invention is to increase the degree of decomposition of apatite, reducing the processing time, as well as increasing the share in the fertilizer in the digestible form. The method includes the decomposition of apatite raw materials; with a particle size of 100–260 µm of nitric acid in an amount that exceeds the stoichiometric value by 2.7–4.0 times, to obtain a phosphate solution and then feed it to the decomposition stage of the remaining part of apatite with a mixture of sulfuric acid and ammonium sulfate at a ratio of 1 $ 1.2-1.4. The amount of this mixture is adjusted in such a way as to bind 70-75% CaO in apatite as calcium sulfate. It is possible to decompose apatite with its simultaneous introduction together with a mixture of sulfuric acid and ammonium sulfate in a nitrophosphate solution, as well as preliminary mixing of a nitrophosphate solution and a mixture of sulfuric acid and ammonium sulfate. The resulting mixture is kept under stirring for 15-30 minutes, ammoniated and then fed for processing in N, P, K-fertilizer. 3 h, para. f-ly, 1 ill., 3 tab. § cl

Description

The invention relates to methods for producing complex: fertilizers — nitrophosphates used in agriculture, by decomposition of phosphate raw materials, in particular apatite, with acids.

The aim of the invention is to intensify the process by increasing the degree of decomposition of apatite and reducing the processing time as well as increasing the proportion in the fertilizer in water-soluble form.

The method involves the preliminary decomposition of part of apatite (15–30% raw material of the total amount) with a particle size of 100–260 µm of nitric acid at a rate of 270–400% of stoichiometry to obtain a nitrophosphate solution, and the remaining part being treated with a mixture of sulfuric acid and sulfate ammonium with a ratio of 1; 1.2-1.4 in the presence of a nitro-phosphate solution. A mixture of sulfuric acid and ammonium sulfate is fed to the treatment of apatite in an amount that provides 70-75% CaO binding in the apatite as calcium sulfate.

It is advisable to decompose the remaining part of apatite while simultaneously introducing apatite and ammonium sulfate solution in sulfuric acid into a nitrophosphate solution, followed by stirring for 15-30 minutes before further processing

It is possible before dor decomposition os. The pre-mixed nitrophosphate solution of apatite is mixed with ammonium sulfate solution in sulfuric acid for 10-15 minutes before further processing, which involves the ammonization of the mixture and its processing in M, XRD fertilizer,

The essence of the method is primarily in TOMj that large particles of apatite 100-260 µm in size, isolated from the total mass of phosphate and 5–3 of about 1/3 of its mass, are decomposed with nitric acid.

Particles with the specified size have a low specific surface. To decompose them, it is necessary to have increased acidity in the pulp. The decomposition of the entire mass of apatite with nitric acid reduces the efficiency of the decomposition process f, since the contact of phosphate with nitric acid first decomposes the fraction of apatite.

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having a particle size less than 100 microns. As a result, a solution of phosphoric acid and calcium nitrate is formed, in which large particles of apatite are suspended. Such a solution has buffer properties and slowly decomposes large particles of apatite, which have a small contact surface with the liquid phase.

With a separate decomposition of the separated coarse fraction of apatite feedstock, the amount of nitric acid taken exceeds the stoichiometric rate for its decomposition by 2.7–4 times. In this case, decomposition proceeds against the background of a significant excess of nitric acid, which sharply accelerates the process.

The drawing shows the dependence of the residence time of the nitric acid pulp in the reactor, which is required to achieve a degree of decomposition of 98%, approved by the technological regulations of nitrophosphate (NPK-fertilizer), on the rate of nitric acid.

The presented results testify to the expediency of conducting the process of decomposition of apatite HNO in the amount of 270-400% of the stoichiometric rate, which allows reducing the decomposition time to 15-30 minutes. The decomposition of a large fraction of apatite under the same conditions with the 200% norm of 1 teOz already requires 125. min. A further increase in the norm of nitric acid in excess of 400% is impossible, since it is necessary to withstand a ratio of 1: 1: 1 in the content of basic nutrients in nitrophosphate, which requires no more than 60-65% nitric acid to be supplied from the total acid consumption for decomposition.

The ratio between ammonium sulfate and sulfuric acid in the mixture should be 1.2-1.4, since an increase in the ratio of ammonium sulfate in a mixture of more than 1.4, as follows from table 1, will lead to underdegradation of apatite, since in decomposition of apatite Only sulfuric acid is involved, while ammonium sulfate serves only for the binding of calcium ions.

If the amount of sulfuric acid in the mixture is increased and the fraction of ammonium sulfate decreases, the stage of ammonization of the nitric acid extract worsens. The introduction of a mixture of sulfuric acid and ammonium fate improves the decomposition process.

apatite, while the pulp is less viscous than when it is divided. The supply of sulfuric acid and ammonium sulfate. In ammonium sulfate and -5miax is in a bonded form, which simplifies the process at the stage of ammonization of the nitrophosphate solution.

The amount of sulfation introduced into the process should be such that 70-75% CaO apatite is bound. In this case, the ratio of the water form to the absorbable form will be not less than 50%. An increase in the content of the S0 ion in the nitrophore will result in the appearance of a ballast ion in the fertilizer, as a result of which the ratio of the main nutrients in the fertilizer, nitrogen and phosphorus, is disturbed. Standard nitrophosphate contains 11% N and 10% PjO and with an increase in the amount of sulfation introduced, the content of these components will become below normal.

The dependence of the proportion of the water form in the product absorbed in the product on the degree of calcium binding in the form of CaSO is given in Table 2, (Mass ratio (NH4) 2.S04; it is assumed to be 1.2: 1).

As follows from Table 2, the degree of bonding of calcium introduced into the process with apatite should be 70-75%. When 68% CaO is bound, the content of the water form in nitrophoska is below 50%, with an increase in the proportion of CaO in excess of 75% in fertilizer, the content of ballast calcium sulfate increases, which results in a decrease in the concentration of nutrients in nitrophoska.

The dependence of the degree of decomposition of apatite in the second stage on the time of decomposition of the raw material is presented in the table.

As follows from Table 3, the most appropriate time interval for the addition of apatite is 15-30 minutes. With a time of less than 15 minutes, the duration of interaction between the particles of phosphate and the sulfate mixture is insufficient, and during 30 minutes the degree of decomposition reaches almost the maximum due to the slowing down of the reaction rate. To achieve a higher ratio, a much longer time is needed, which is irrational due to the increase in power consumption and increase in the volume of equipment.

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Example 1. Separated in a known manner, 15 kg (15% of the total kvolne- s.tva phosphate) of a large fraction of apatite with a particle size of 100-260 µm is dissolved in 128.5 kg (the norm is 100%) of nitric acid (in terms of monohydrate hereafter) at a concentration of 60% HNO for 15 minutes. The degree of decomposition of the coarse fraction of apatite is 98.75%. Then, 85 kg of apatite (the remaining amount) and 75.74 kg of a solution of ammonium sulfate in sulfuric acid were introduced into the nitrophosphate solution in the sulfuric acid ratio (NH), S04: H.SO 152; 1 in order to bind 70% CaO Calcium sulfate apatite and pulp are mixed for 15 minutes. The total decomposition time is 30 minutes. Then the pulp is ammoniated with 10.27 kg am (Iac, after adding amization to 67.8 kg of potassium chloride. The resulting mixture is granulated and dried. The resulting product is a nitrophosphate of the following composition, wt.%: N 11.48,

aOsOB14 11 ,, Pi VycB 10.49. 5.97, 11.48, H orkgr 1.0.

Prash-1er 2. 25 kg (25% of the total amount) of the coarse fraction of apatite decompose 250 kg (a norm of 350%) of nitric acid with a concentration of 45% HNOj within 25 minutes (KRd., 98.5%). 75 kg of apatite and 78.8 kg of a mixture of a solution of a sulfate a mono in sulfuric acid are introduced into the resulting nitrophosphate solution at a ratio of the components of the mixture (NH4) 2504: H, SO 1.25; 1, taken in such quantity to bind 72 % CaO from apatite. Apatite is decomposed within 25 minutes. Total decomposition time 50 min. The obtained ammonium pulp with gaseous ammonia in the amount of 17.83 kg and 67.8 kg of potassium chloride with a concentration of 57.5% are added. The resulting pulp is granulated and. The finished product has the following composition, wt.%; N 11.31, Prg05o6wl 30, R.g05, sv11.13, RO 6.12, K, 0 11.31; 1, C,

Example 3. 30 kg (30% of total Phosphate) of a large fraction of apatite with a particle size of 100-260 µm decompose within 30 minutes 190.3 kg of 55% nitric acid (acid norm is 270%). The degree of decomposition of apatite is 98%. To the resulting solution was added 81.97 kg of a solution of ammonium sulfate in sulfuric acid, taken in. honeycomb

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the ratio (NH4) i S04: Hj SO 1.3: 1 to bind 75% CaO apatite and stirred for 10 minutes. Then, pulp is treated with 70 kg of apatite for 30 minutes. The pulp is ammoniated with 13.88 kg of miak, 67.8 kg of potassium chloride is added. The resulting pulp is granulated and dried. The result is a nitrophosphate of the following composition, wt.%: N 11,18; P ,,, 19, P., 10,24, PaO.od 6.66; K, 0 11.18, - H ,, 0, j, 1.0.

Thus, the proposed method allows to increase the degree of decomposition of apatite and significantly intensify the production of nitrophosphate, while reducing the consumption of scarce sulfuric acid.

Claims (3)

Invention Formula / 1, A method of processing apatite, which includes decomposing part of the apatite raw material with nitric acid to produce a nitrophosphate solution, decomposing the remaining portion of the raw material with sulfuric acid, processing the nitrophosphate solution and sulfuric acid decomposition pulp, and processing the resulting mixture into a fertilizer characterized in that process by increasing the degree of decomposition of apatite and sokra390926 At the stage of nitric acid decomposition, the fraction of apatite with a particle size of 100–260 µm is supplied to the stage of nitric acid decomposition and decomposition is carried out with nitric acid in an amount exceeding the stoichiometric ratio of 2.7–4.0 times and the treatment of the remaining part of apatite. carried out with a mixture of sulfuric acid and 10 ammonium sulfate at a ratio of 1: 1.2-1.4 in the presence of a nitrophosphate solution. 2. The method according to claim 1, about tl and h and u and with the fact that, in order to increase in / fertilizer content in water form, a mixture of sulfuric acid and ammonium sulfate is fed to the treatment in an amount that provides 70–75% CaO binding in apatite. 20 in the form of calcium sulfate. 3. The method according to claim 1, wherein the treatment is carried out with the fact that, prior to the treatment of the remaining part of apatite, the solution of sulfuric acid and ammonium sulfate is preliminarily mixed with the nitrophosphate solution for 10-15 minutes. 4 The method of pop. 1, which is different from that with the processing of the remaining part of the apatite raw material 30 are blown with the simultaneous introduction of apatite and a mixture of sulfuric acid and ammonium sulfate into the nitrophosphate solution, followed by stirring: by drying for 15-30 minutes. Table 1 L °,% ot.4548 50 55 60 65  W b. Decomposition time. min Degree of decomposition, rel.% 97.5 98.0 98.2 98.5 98.5 99.0 Gablitz2 That blitz 3 12 15 25 thirty 35 60