RU2630493C1 - Method for producing nitrogen-potassium sulfate fertiliser and hydrochloric acid - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: method for producing a nitrogen-potassium sulfate fertiliser and hydrochloric acid comprises converting fine potassium chloride and/or cyclone dust of potassium chloride of concentrated sulfuric acid at an elevated temperature to obtain a solution containing potassium hydrogen sulfate, hydrochloric acid, excess of sulfuric acid; separation of hydrochloric acid vapours from solution, condensation of vapors to produce hydrochloric acid, neutralisation of potassium hydrogen sulfate with ammonia, crystallization and separation of precipitate crystals from solution. The fine potassium chloride and/or the cyclonic dust of potassium chloride are dissolved in water before the conversion step, the resulting solution is converted with concentrated sulfuric acid at a ratio H₂O/KCl=1.5-2.5, keeping the concentration of sulfuric acid 35-46% in the reaction medium, separating the hydrochloric acid vapours from the solution under the boiling point of the solution and condensing, the resulting solution is cooled with crystallization of potassium hydrogen sulfate, which is separated from solution and neutralized with ammonia water by washing the precipitate in the filtration step, and the resulting filtrate is returned to the conversion step.

EFFECT: invention allows to increase the rate of conversion, to exclude the formation of a by-product - ammonium sulfate.

2 cl, 4 dwg, 4 tbl, 2 ex

Description

The invention relates to a technology for producing nitrogen-potassium sulfate fertilizer and hydrochloric acid and can be used in the chemical industry, in particular in the production of chlorine-free complex nitrogen-potassium sulfate mineral fertilizers and hydrochloric acid.

A known method of producing a chlorine-free fertilizer - potassium sulfate, from potassium chloride and ammonium sulfate in an aqueous medium by processing excess solutions into a complex NPK fertilizer (RF patent No. 2144000 from 01.10.2000). The method involves the preparation of potassium sulfate and complex fertilizer, and includes the interaction of a solution of ammonium sulfate and a suspension of potassium chloride, the allocation of a double salt of potassium ammonium sulfate and its treatment with a 5-15% solution of potassium chloride, separation of the formed potassium sulfate from the mother liquor, washing and returning the mother liquor solution for the preparation of a suspension of potassium chloride, and the solution obtained after isolation of the double salt is heated and ammonium phosphate is added to it with vigorous stirring in an amount that ensures determining the ratio of K ₂ O: P ₂ O ₅ in a solution of 1.0: (1.0-3.0), and then finely dispersed potassium chloride is added to the solution in an amount providing a predetermined ratio of K ₂ O: P ₂ O ₅ in the fertilizer , the resulting suspension is sprayed and dried. As finely dispersed potassium chloride, cyclone dust of potash dressing plants can be used. The method allows simultaneously with potassium sulfate to obtain complex NPK-fertilizer with a given ratio of nutrients from excess solutions of potassium sulfate production.

The disadvantage of this method is that the method eliminates the production of hydrochloric acid, and the resulting NPK fertilizer has a high content of chloride ion in the form of ammonium chloride.

The closest to the claimed invention in terms of essential features is a method for producing hydrochloric acid and chlorine-free potassium-sulfate nitrogen fertilizers, including: the interaction of sulfuric acid with potassium chloride to obtain a solution containing hydrochloric acid, potassium acid sulfate (KHSO ₄ hydrosulfate), excess sulfuric acid; separation of hydrochloric acid from a solution containing hydrochloric acid, potassium hydrogen sulfate, excess sulfuric acid; neutralization of potassium hydrogen sulfate and excess sulfuric acid by adding ammonia to the solution obtained after separation of hydrochloric acid to obtain a neutral mass; cooling the neutral mass to crystallize the double potassium sulfate and ammonium sulfate and obtain neutral crystals of the double potassium sulfate and ammonium; separation of neutral crystals of potassium and ammonium double sulfate from solution (Patent US 20020114759 A1; C01B 7/035, C01B 17/96, C01D 5/02; Process for the production of hydrochloric acid and neutralized sulfates / Jose Cabello-Fuentes; Publ. 22.08 .2002). This method is adopted as a prototype.

Signs of the prototype, which coincides with the essential features of the claimed invention, is the conversion of finely dispersed potassium chloride and / or potassium chloride cyclone dust with concentrated sulfuric acid at elevated temperatures to obtain a solution containing potassium hydrogen sulfate, hydrochloric acid, an excess of sulfuric acid; separation of hydrochloric acid vapor from the solution; vapor condensation to produce hydrochloric acid; neutralization of potassium hydrosulfate with ammonia; crystallization and separation of precipitate crystals from solution.

The disadvantage of this method, adopted as a prototype, is that the method has a low conversion rate, high energy intensity, as well as the incomplete use of ammonia, increased consumption of ammonia to neutralize excess sulfuric acid, accompanied by the formation of a by-product of ammonium sulfate.

The problem to which the claimed invention is directed is to increase the conversion rate, reduce the energy intensity and consumption of ammonia to neutralize the excess sulfuric acid, eliminate the formation of a by-product - ammonium sulfate, upon receipt of potassium nitrate sulfate fertilizer and hydrochloric acid.

The problem was solved due to the fact that in the known method for producing potassium nitrate potassium sulfate fertilizer and hydrochloric acid, which includes the conversion of finely dispersed potassium chloride and / or potassium chloride cyclone dust with concentrated sulfuric acid at elevated temperature to obtain a solution containing potassium hydrogen sulfate, hydrochloric acid excess sulfuric acid; separating hydrochloric acid vapors from a solution, condensing vapors to produce hydrochloric acid, neutralizing potassium hydrogen sulfate with ammonia, crystallizing and separating precipitate crystals from a solution, according to the invention, finely dispersed potassium chloride and / or potassium chloride cyclone dust are dissolved in water before the conversion step to obtain a solution which is converted with concentrated sulfuric acid at a ratio of H ₂ O / KC1 = 1.5-2.5, 35-46% while maintaining in the reaction medium concentration of sulfuric acid, hydrochloric acid vapors separated from solution p d vacuo at boiling temperature and the solution was condensed, the resulting solution is cooled to crystallize potassium hydrogensulfate, which was separated from the solution and was neutralized with ammonia water by washing the precipitate on filter stage, and the filtrate is recycled to the conversion step.

It is recommended that the precipitate of potassium hydrogen sulfate be neutralized by a countercurrent three-stage washing with ammonia water.

Signs of the proposed technical solution, distinctive from the solution of the prototype, - dissolve finely dispersed potassium chloride and / or cyclone dust of potassium chloride in water before the conversion stage; converting the resulting solution with concentrated sulfuric acid at a ratio of H ₂ O / KC1 = 1.5-2.5, maintaining a concentration of sulfuric acid in the reaction medium of 35-46%; hydrochloric acid vapors are separated from the solution under vacuum at the boiling point of the solution and condensed; cooling the resulting solution with crystallization of potassium hydrosulfate; potassium hydrosulfate is separated from the solution and neutralized with ammonia water by washing the precipitate at the filtration stage, and the obtained filtrate is returned to the conversion stage; neutralization of the precipitate of potassium hydrosulfate is carried out by countercurrent three-stage washing with ammonia water.

The use of dissolution of KC1 in water before the stage of conversion of KC1 with concentrated sulfuric acid allows one to raise the temperature of the reaction medium due to the heat of dissolution of concentrated sulfuric acid in an aqueous solution of KC1 and increase the speed of the process, since the dissolution of crystalline potassium chloride in sulfuric acid proceeds slowly. Using the heat of dissolution of concentrated sulfuric acid can reduce the heat consumption for heating the reaction mixture, which reduces energy intensity.

The lower limit of the ratio of H ₂ O / KC1 = 1.5, at which the dissolution of finely dispersed potassium chloride and / or cyclone dust of potassium chloride in water is carried out, due to the solubility of potassium chloride in water. If the ratio of H ₂ O / KCl increases to more than 2.5, the concentration of reagents in the solution will be low, therefore, the process will proceed at a low rate, and the resulting hydrochloric acid will have a low concentration, which makes it difficult to use. The concentration limits of sulfuric acid 35-46% directly depend on the ratio of H ₂ O / KC1 (example 1, table. 1). The concentration of sulfuric acid in the present method (35-46%) is lower than in the known (70%).

It was experimentally established that the use of vacuum to separate hydrochloric acid vapors is effective for increasing the yield of hydrogen chloride (example 1, Fig. 1), and also allows to lower the process temperature, since under vacuum the boiling point of a solution containing potassium hydrogen sulfate, hydrochloric acid, excess sulfuric acid acid lower than at atmospheric pressure.

Compared with the prototype, in which the neutralization of a suspension of potassium hydrosulfate with ammonia is carried out at elevated temperatures (80-125 ° C), in our claimed method, the neutralization is carried out at a temperature of 20-25 ° C. This mode of neutralization helps to reduce ammonia losses by reducing the volatility of ammonia.

The preliminary operation of separating potassium hydrogen sulfate from the mother liquor containing an excess of sulfuric acid, and the subsequent neutralization of the precipitate of potassium hydrogen sulfate, can reduce the consumption of ammonia and reduce the time required to neutralize the excess sulfuric acid, as well as to eliminate the formation of an undesirable product - ammonium sulfate. In this case, the mother liquor to eliminate the loss of unused sulfuric acid contained in it, is returned to the stage of conversion of the potassium chloride solution with sulfuric acid.

To neutralize potassium hydrosulfate, washing of the precipitate is used by countercurrent three-stage washing with ammonia water. This method is simple in technological design and does not require additional equipment costs. In this case, a single washing operation to completely neutralize potassium hydrosulfate is not enough; therefore, it is recommended to carry out a three-stage washing of potassium hydrosulfate with ammonia water according to a countercurrent scheme with repeated use of washing solutions.

The invention is illustrated by drawings.

In FIG. 1 shows the dependence of the yield of hydrogen chloride on vacuum and the ratio of H ₂ O / KCl.

In FIG. 2 shows a direct-flow washing scheme for potassium hydrogen sulfate. The diagram shows 1-3 - vacuum filters.

In FIG. Figure 3 shows the X-ray diffraction pattern of the product obtained by neutralizing the hydrosulfate with a three-stage washing with an ammonia solution on the filter.

In FIG. 4 shows a countercurrent flushing scheme for potassium hydrosulfate sludge. The diagram shows 1-3 - vacuum filters.

The possibility of implementing the method is confirmed by the following examples.

Example 1

As a raw material for the production of nitrogen-potassium fertilizer and hydrochloric acid, cyclone dust of potassium chloride of the Bereznikovsky potash mine department No. 2 of OJSC Uralkali containing 93.2% KCl was used; 3.7% NaCl; 0.2% MgCl ₂ ⋅H ₂ O; 0.8% CaSO ₄ ; 2.1% H ₂ O. (insoluble residue), and concentrated sulfuric acid (95% H ₂ SO ₄ ). Cyclone dust (CP) in an amount of 100 g was previously dissolved in water in a weight ratio of H ₂ O / KC1 = 1.5; 2; 2.5. A solution of potassium chloride was fed to the conversion step, maintaining a sulfuric acid concentration of 35-46% in the reaction medium. In this case, the excess of sulfuric acid amounted to 10% of the stoichiometric ratio in the reaction:

The conversion of the potassium chloride solution with concentrated sulfuric acid was carried out without additional heating of the reaction mixture, which spontaneously warms up to a temperature of 65 ° C due to dilution of sulfuric acid. The conversion was carried out with recycle of the mother liquor (in an amount of 25% of the solution) obtained after the crystallization stage of potassium hydrosulfate. Then, the process of separation of hydrochloric acid vapor under vacuum was carried out with heating the resulting mixture to a boiling point at a constant stirring speed of 600 rpm, which ensures homogenization of the reaction mixture.

The concentration of sulfuric acid in the conversion depends on the ratio of H ₂ O / KC1, at which the dissolution of the cyclone dust of potassium chloride was carried out. The concentration of sulfuric acid in the reaction medium at different ratios of H ₂ O / KCl is shown in table 1.

Vapors of hydrogen chloride and water leaving the reactor were collected and condensed by cooling in a tubular glass refrigerator cooled with cold water. The concentration of hydrochloric acid obtained (depending on the ratio of H ₂ O / KCl and vacuum) was 20-28%. The resulting hydrochloric acid can be used in oil production. The selection of the H ₂ O / KC1 ratio during conversion and vacuum at the stage of distillation of hydrochloric acid vapor was made on the basis of the experimental dependences of the yield of hydrogen chloride, which are presented in FIG. one.

From the dependencies in FIG. 1 it follows that maintaining the ratio of H ₂ O / KC1 in the range of 1.5-2.5 at different vacuum allows to obtain a yield of hydrogen chloride of 66-93%. At a ratio of H ₂ O / KC1 = 1.5, the concentration of substances in the converted solution increases, and, consequently, the rate of the conversion process, which leads to the release of hydrogen chloride 78-93%. And when the ratio is less than H ₂ O / KC1 = 1.5, the potassium chloride content is higher than the KS1 saturation point of the solution, while the process of conversion of potassium chloride with sulfuric acid will occur not in the solution, but at the interface between the solid and liquid phases, the process speed will also will decrease, the product will contain a large proportion of chloride ions. When the ratio of H ₂ O / KC1 more than 2.5, the conversion process proceeds at a low speed and low yield of hydrogen chloride (less than 66%), which is unacceptable for use in industry.

As seen in FIG. 1, at a higher vacuum, the yield of hydrogen chloride is higher.

After the hydrochloric acid separation step, a solution (325 g) containing potassium hydrogen sulfate (54.4%), sulfuric acid (24.7%) and absorbed hydrogen chloride (2.1%) was obtained, from which potassium hydrogen sulfate was then crystallized by cooling the solution to 25 ° C at a constant stirring speed of 600 rpm with a cooling rate of 1.5 ° C per minute. Then, the precipitate of potassium hydrogen sulfate is separated from the solution and neutralized.

The neutralization of the obtained potassium hydrogen sulfate KHSO ₄ (170 g) was carried out by directly washing the precipitate with ammonia water (with an ammonia concentration of 25%) on a vacuum filter with an ammonia water / precipitate ratio = 3/1. When neutralizing potassium hydrosulfate, the reaction proceeds:

The sulfuric acid content in the precipitate of potassium hydrogen sulfate before and after washing the precipitate is presented in table 2.

From the data of table 2 it can be seen that a single washing of potassium hydrosulfate with ammonia water can reduce the sulfuric acid content in the product to 11.9%. A single wash is not sufficient to completely neutralize potassium hydrosulfate. In this regard, the neutralization of potassium hydrosulfate KHSO ₄ was carried out by washing it with ammonia water (with an ammonia concentration of 25%) on a vacuum filter in three stages with a ratio of ammonia water / precipitate = 3/1 according to the direct-flow diagram shown in FIG. 2.

With direct-flow washing, the solution and potassium hydrogen sulfate move in parallel. For washing, a solution was used with an initial concentration of ammonia of 25%, with a ratio of ammonia water / precipitate = 3/1. In this case, the washing solution from the vacuum filter 1, containing after a single washing of 21.3% NH ₃ , is supplied for washing the hydrosulfate on the vacuum filter 2, and the solution after the second washing, containing 10.3% NH ₃ , is used for washing on the filter 3. After the third washing, potassium double sulfate and a washing solution containing ammonium sulfate and unreacted ammonia in the amount of 1.6% are formed, which can be further processed to crystallize double potassium and ammonium sulfate. The sulfuric acid content in the precipitate of potassium hydrogen sulfate before and after washing the precipitate is presented in table 3.

From the data of table 3 it follows that a three-time straight-through washing of potassium hydrosulfate with ammonia water can reduce the sulfuric acid content in the sediment to 0.1%.

The composition of the obtained product upon neutralization of potassium hydrosulfate by three-stage washing with an ammonia solution on a filter was determined by X-ray phase analysis on an XRD0-7000 X-ray diffractometer. The X-ray diffraction pattern is shown in FIG. 3.

The x-ray in FIG. 3 confirms that when the hydrosulfate is neutralized by a three-stage washing with an ammonia solution, a neutral product is formed on the filter, which consists of double potassium and ammonium sulfate mixed with potassium sulfate.

Example 2

The stages of conversion and production of hydrochloric acid were carried out according to example 1. The difference was that the neutralization of potassium hydrosulfate KHSO ₄ was carried out by washing it with ammonia water (with an ammonia concentration of 25%) on a vacuum filter in three stages with an ratio of ammonia water / precipitate = 3 / 1 according to the countercurrent circuit shown in FIG. 4. In countercurrent washing, an ammonia solution (NH ₃ concentration _of 25%) and neutralizable potassium hydrosulfate move towards each other. In this case, potassium hydrosulfate is fed into the first vacuum filter, and the ammonia solution into the third. Wash solution from a third solvent containing 17.4% NH ₃ goes into the second. After the second washing, the solution leaving solvent 2 contains 12.6% NH ₃ and is supplied to solvent 1 for subsequent neutralization. The final solution obtained after a three-stage countercurrent washing contains 1.7% ammonia. The sulfuric acid content (%) in the precipitate of potassium hydrosulfate after operations three times countercurrent washing is shown in table 4.

From the data in table 4 it follows that a three-time countercurrent washing of potassium hydrosulfate with ammonia water allows to completely neutralize sulfuric acid in the precipitate of potassium hydrosulfate to obtain a neutral product, which consists of double potassium sulfate and ammonium, as confirmed by x-ray phase analysis.

The proposed method for producing nitrogen-potassium sulfate fertilizer and hydrochloric acid allows to obtain chlorine-free nitrogen-potassium sulfate fertilizer and hydrochloric acid with a concentration of 20-28%). The resulting hydrochloric acid can be used in oil production. The method provides a higher conversion rate, lower energy consumption due to the use of the heat of reaction, lower consumption of ammonia to neutralize the excess sulfuric acid (more complete use of ammonia), eliminating the formation of a by-product of ammonium sulfate.

Claims (2)

1. A method of producing nitrogen-potassium sulfate fertilizer and hydrochloric acid, comprising the conversion of finely dispersed potassium chloride and / or cyclone dust of potassium chloride with concentrated sulfuric acid at elevated temperatures to obtain a solution containing potassium hydrogen sulfate, hydrochloric acid, an excess of sulfuric acid; separation of hydrochloric acid vapors from the solution, condensation of vapors to produce hydrochloric acid, neutralization of potassium hydrosulfate with ammonia, crystallization and separation of precipitate crystals from the solution, characterized in that finely dispersed potassium chloride and / or potassium chloride cyclone dust are dissolved in water before the conversion step, the resulting solution is converted with concentrated sulfuric acid at a ratio of H ₂ O / KCl = 1,5-2,5, while maintaining in the reaction medium concentration of 35-46% sulfuric acid, hydrochloric acid vapors separated from the solution in vacuo When the boiling temperature of the solution and condensed, the resulting solution is cooled to crystallize potassium hydrogensulfate, which was separated from the solution and was neutralized with ammonia water by washing the precipitate on filter stage, and the filtrate is recycled to the conversion step. 2. The method according to p. 1, characterized in that the neutralization of the precipitate of potassium hydrosulfate is carried out by countercurrent three-stage washing with ammonia water.

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