RU2182884C1 - Method of treatment of wet-processing phosphoric acid used for production of liquid complex fertilizers - Google Patents

Abstract

FIELD: fertilizers. SUBSTANCE: method involves heating the parent wet-processing phosphoric acid with concentration 52-54 wt.-% of P₂O₅ with addition of magnesium compound to 50-60 C and addition of nitrate (ammonium or sodium, potassium, copper, magnesium nitrate) and urea taken in mass ratio = (0.00007-0.0004) : (0.0001- 0.00015) : 1, respectively, as measured for nitrogen followed by evaporation under pressure 0.002- 0.007 mPa at 185-205 C to the conversion degree of P₂O₅ 20-50% to polyforms. Invention ensures to production of complex liquid fertilizers from the purified wet-processing phosphoric acid corresponding to the world standard. Invention is designated for production of wet-processing phosphoric acid mined from the Khibini Mountains apatite concentrate and used for production of liquid phosphoric fertilizers. EFFECT: enhanced degree of treatment of phosphoric acid from organic impurities. 4 cl, 2 tbl, 1 ex

Description

 The invention is intended to produce extraction phosphoric acid (EPA) obtained from the Khibiny apatite concentrate, which is used to produce liquid complex fertilizers (HCF).

A known method of purifying EPA from organic impurities, including processing it with an aqueous solution of hydrogen peroxide. Previously, nitric acid is introduced into phosphoric acid in a mass ratio to hydrogen peroxide and phosphoric acid (0.0003-0.001) :( 0.002-0.008): 1. Treatment with hydrogen peroxide is carried out at a temperature of at least 40 ^o C (RU 2134233; op. 08/10/1999).

 The disadvantage of this method is the low cleaning efficiency due to the decomposition of hydrogen peroxide.

A known method of purification of EPA, containing as impurities sulfates, fluoride compounds and suspension, by evaporation of EPA, treatment with apatite concentrate, adding a coagulant, clarification and subsequent separation of the condensed precipitate from the product. After evaporation in the EPA solution, the mass ratio F: P ₂ O ₅ = 0.003-0.008 and the mass ratio SO ₄ : P ₂ O _{5 are} maintained in the range 0.02-0.05, and in the EPA solution after treatment with apatite concentrate, the mass ratio SO is maintained ₄ : P ₂ O ₅ = 0.003-0.010. To maintain the ratio F: P ₂ O ₅ within the range of 0.003-0.008 in the solution of EPA after evaporation, the concentration of EPA before evaporation is changed within the range of 34–40% P ₂ O ₅ , and the concentration of EPA after evaporation is changed within the range of 52-57% P ₂ O ₅ (RU 2131842; op. 06/20/1999).

 The disadvantage of this method is the multi-stage and the inability to clean from organic impurities.

The closest analogue is the method of purification of EPA used to obtain LCF, including heating EPA containing 52-54 wt.% P ₂ About ₅ , with the addition of magnesium compounds and subsequent evaporation to superphosphoric acid (Technology of phosphate and complex fertilizers. Ed. C D.Evenchik, A.A. Brodsky, M., Chemistry, 1987, p. 112-114).

 The disadvantage of this method is the low degree of purification from organic impurities (the resulting acid is black and brown in color and is not suitable for obtaining from it those grades of housing and communal services in which, according to world standards, the content of organic carbon is not allowed, for example housing and communal services of brand 11:37, and which must have a clear, light or light green color).

The objective of the invention is to increase the degree of purification from organic impurities. The problem is achieved by the method of purification of EPA used to produce liquid complex fertilizers, including heating the initial EPA containing 52-54 wt.% P ₂ O ₅ to 50-60 ^o With the addition of magnesium compounds, the introduction of salt of nitric acid and urea in bulk the ratio in terms of nitrogen (N) to extraction phosphoric acid, respectively (0.00007-0.0004) :( 0.0001-0.00015): 1 and subsequent evaporation at a temperature of 185-205 ^o With a pressure of 0.002-0.007 MPa

 Ammonium nitrate, sodium nitrate, potassium nitrate, copper nitrate, magnesium nitrate are taken as the nitric acid salt. Evaporation of extraction phosphoric acid is carried out to a degree of conversion of phosphoric acid into polyforms of 20-50%.

The introduction of a salt of nitric acid (ammonium, sodium, potassium nitrates, etc.) leads to the oxidation of organic impurities contained in EPA. When redox reactions occur with organic impurities in EPA, nitrogen is reduced (in the form of NO ₃ -) with the oxidation state (Y) to nitrogen oxides with the oxidation state (IY). Organic compounds are oxidized to CO ₂ . The oxidation process is accompanied by the formation of nitrogen oxides released into the gas phase.

To prevent emissions of nitrogen oxides into the atmosphere, urea is introduced into the reaction mass, which interacts with nitrogen oxides by the following reaction:
2CO (NH ₂ ) ₂ + 3NO ₂ -> 3,5N ₂ + 2CO ₂ + 4Н ₂ О
Example
EPA obtained from Khibiny apatite concentrate containing 52-54 wt. % P ₂ About _{5 is} heated to 60 ^o With the addition of magnesite to a concentration of MgO in the liquid phase of 0.25-0.29 wt.% By weight of acid. At the end of the dissolution of magnesite, ammonium nitrate, sodium nitrate, potassium nitrate, copper nitrate and urea are introduced (the dosage is indicated in Table 1). Evaporation is carried out at a temperature of 185-195 ^o C, the load on the original EPA - 5.9 m ³ / h and a pressure of 0.0035-0.0040 MPa.

In this case, phosphoric acid is obtained with a degree of conversion to polyforms of 21-27%. The amount of purified phosphoric acid obtained is 3.4-4.75 m ³ / h. It is used to produce liquid complex fertilizers.

 Depending on the dosage of nitrates and urea, the color of phosphoric acid changes from black, dark brown to light green and light yellow.

 Table 1 gives the data on the color of phosphoric acid depending on the dose of nitrates (ammonium, sodium, potassium, copper, magnesium) and urea.

 The experimental conditions are indicated in the above example.

 As can be seen from the data in Table 1, outside the mass ratio of nitrates to phosphoric acid 0.0004 in terms of nitrogen (N): 1, the addition of additional amounts of nitrates does not have a positive effect on the color of the obtained phosphoric acid. Also, outside the mass ratio of urea 0.00015 in terms of nitrogen (N): 1 with respect to EPA, its effect on the quality of acid is not detected, and an increase in the amount of urea leads to its excessive consumption.

The content of heavy metal impurities in the initial EPA, wt.%: Mn - 0,038; Cr - 0,00023; Co - 0,00026; Ni 0.0005; Fe ₂ O ₃ - 0.67; As - 0.0019. The release of nitrogen oxides in the gas phase with a mass ratio of urea to EPA of 0.0001-0.00015 (in terms of N) does not occur.

 Acid of green, light green and light yellow color provides further production of housing and communal services having a transparent, light and light green color.

 The color of liquid complex fertilizers (LCF), obtained on the basis of phosphoric acid purified by this method, correlates with the dosage of nitrates upon receipt of EPA, as can be seen from the data in Table 2.

During the pilot test period, 429 tons of 100% P ₂ O ₅ HCF grade 11:37 with the following quality indicators (average sample) are shown in Table 3 from the EPA purified from this organic matter from organic impurities.

 This invention improves the quality of phosphoric acid for the production on its basis of liquid complex fertilizers that meet international standards.

Claims (4)

1. The method of purification of extraction phosphoric acid used to obtain liquid complex fertilizers, comprising heating the extraction phosphoric acid containing 52-54 wt. % P ₂ O ₅ , with the addition of magnesium compounds and subsequent evaporation, characterized in that the heating is carried out to 50-60 ^o C and before evaporation enter the nitric acid salt and urea in a mass ratio in terms of nitrogen (N) to extraction phosphoric acid, respectively (0.00007-0.0004): (0.0001-0.00015): 1 and evaporation is carried out at 185-205 ^o C.  2. The method according to p. 1, characterized in that as the salt of nitric acid take ammonium nitrate, sodium nitrate, potassium nitrate, copper nitrate or magnesium nitrate.  3. The method according to p. 1, characterized in that the evaporation is carried out to a degree of conversion of phosphoric acid into polyforms of 20-50%.  4. The method according to p. 1, characterized in that the evaporation is carried out under a pressure of 0.002-0.007 MPa.

Images