RU2336251C2 - Method of obtaining complex nitrogen-phosphorous fertiliser - Google Patents

Abstract

FIELD: chemistry, agriculture.

SUBSTANCE: method of obtaining complex nitrogen-phosphorous fertiliser based on ammonium nitrate with addition of phosphate includes step-by-step neutralisation of nitric acid with ammonium, evaporating of neutralised solution, introduction of phosphate additive and product granulation. According to invention as phosphate additive, sediment of calcium phosphate, obtained by separation of preliminary ammonated pulp, formed in nitric-acid or hydrochloric-acid break-down of apatite concentrate, is used. Percentage of phosphates in fertiliser in terms of P₂O₅ constitutes 2-9 wt %, nitrogen - 27-32 wt %.

EFFECT: increase of fire-explosion safety of fertilizer and increase of phosphorus percentage.

2 cl, 1 tbl, 6 ex

Description

The invention relates to methods for producing complex nitrogen-phosphorus mineral fertilizers based on ammonium nitrate with the addition of phosphates for agriculture.

A complex nitrogen-phosphorus mineral fertilizer is known and a method for its production by nitric acid decomposition of natural phosphates, ammonization of the resulting solution, drying and granulation of the product. The resulting fertilizer contains 15-20% nitrogen and 30-40% phosphorus in terms of P ₂ O ₅ , and only 14-16% of the specified amount of phosphorus is in water-soluble form (ed. St. No. 68488, IPC 7 C05B 11/06 , publ. 09/30/1979). The disadvantage of this method is the low content of water-soluble forms of phosphorus and the relatively low nitrogen content, which reduces its agrochemical value.

A known method of producing a complex nitrogen-phosphorus mineral fertilizer that is closest to the claimed combination of essential features, by stepwise neutralizing ammonia with nitric acid with the addition of phosphoric and sulfuric acids, evaporation of the neutralized solution and granulation of the target product (US Pat. RF No. 2174970, IPC 7 C05C 1 / 00, G 1/06, publ. 20.10.2001). Known fertilizer is ammonium nitrate with the addition of phosphoric and sulfuric acids in the form of ammonium salts. The ratio of nutrient components in the fertilizer is N - 33 ± 1; P ₂ About ₅ - 2-6 wt.%. The disadvantage of this method is to reduce fire and explosion safety of the product in the presence of chlorides.

The technical problem solved by the claimed method is to eliminate this drawback, i.e. increasing the fire and explosion safety of fertilizers, as well as increasing the agrochemical value of fertilizers by increasing the phosphorus content in it.

The stated technical problem is solved in that in the method for producing complex nitrogen-phosphorus fertilizer based on ammonium nitrate with the addition of phosphate in terms of P ₂ O ₅ in an amount of 2-9 wt.%, Including stepwise neutralization of ammonia with nitric acid, evaporation of the neutralized solution, introduction phosphate additives and granulation of the product according to the invention as phosphate additives use phosphorus-containing calcium compounds.

As phosphorus-containing calcium compounds, a precipitate of calcium phosphates is used, obtained by separating the pre-ammoniated pulp formed during the nitric acid opening of the apatite concentrate [Complex nitric acid processing of phosphate raw materials. Ed. A.L. Goldinova, B.A. Kopyleva. L .: Chemistry, 1982, p. 122]. It is also possible to use as a phosphate additive a precipitate of calcium phosphates obtained by hydrochloric acid opening of an apatite concentrate.

The phosphate content in the fertilizer in terms of P ₂ O ₅ is 2-9 wt.%, N - 27-32 wt.%.

The phosphate additive is introduced into the melt of ammonium nitrate.

Example 1

In the experiments, the ammonium nitrate melt obtained by stepwise ammonia ammonia nitric acid with the addition of sulfuric acid and evaporation of the neutralized solution to a residual moisture content of not more than 0.5% (hereinafter wt.%) Is used. The chloride content in the melt is 0.02%. (In accordance with the EU Directive 80/876 / EEC and the EU Law on Fertilizers No. 2003/2003 of 10/13/2003 regarding the safety of handling, the chloride content in ammonium nitrate should not exceed 0.02%.)

As phosphorus-containing calcium compounds, a precipitate is used, which is formed by separation of pre-ammoniated pulp obtained after nitric acid decomposition of apatite concentrate and separation of part of calcium in the form of calcium nitrate tetrahydrate (calcium excretion 60%). The precipitate after separation is dried to a residual moisture content of about 1%.

The component composition of the precipitate,%: Ca - 33, P ₂ O ₅ - 40, N - 2, F - 6, H ₂ O - 1.

The calculated salt composition of the precipitate,%: CaHPO ₄ - 46, Ca ₃ (PO ₄ ) ₂ - 35, CaF ₂ - 12, NH ₄ NO ₃ - 6, H ₂ O - 1.

92 g of ammonium nitrate melt are mixed with 8 g of a precipitate of calcium phosphates, preheated to a temperature of 80-90 ° C, obtained by the above method. The mixed melt is granulated and thermal stability of the product is determined. This parameter - thermal stability - determines the fire and explosion safety of the fertilizer obtained.

The nutrient content in the resulting fertilizer is: N - 32.2%, P ₂ O ₅ - 3.2%, the chloride content in the finished product is 0.02%.

The analysis of the composition of the sediment and the fertilizer obtained was carried out according to the methods given in the regulatory documentation for fertilizers:

- mass fraction of calcium - according to GOST 24596.4 complex metric method;

- mass fraction of phosphates in terms of phosphorus oxide - GOST 2085.2-75 “Mineral fertilizers. Analysis Methods ”by differential photometric method for the formation of yellow-colored phosphorus-vanadium-molybdenum complex;

- mass fraction of water - according to GOST 20851.4, sec. one;

- mass fraction of chlorine ion - according to GOST 5382-91 p.18.3 phototurbidimetric method;

- mass fraction of fluoride ion - according to GOST 24596.7-81;

- mass fraction of total nitrogen - according to GOST 30181.1-94.

The thermal stability of the fertilizer is evaluated by the time before the decomposition of the test sample at a temperature of 190 ° C. The maximum exposure time of the sample is 3 hours.

The experimental results are shown in the table.

Example 2

A series of experiments is carried out similar to the above, in which the content of nutrient components in the fertilizer is changed in the range: N - 27-32%, P ₂ O ₅ - 2-9%, the chloride content in the granular fertilizer: 0.01-0.02%.

The results of the experiments are shown in the table.

Example 3

An experiment similar to example 1 is carried out, in which a precipitate obtained after hydrochloric acid decomposition of apatite with a 20% hydrochloric acid solution and neutralization of the hydrochloric acid suspension with a suspension of calcium carbonate to pH = 3 is used as phosphorus-containing calcium compounds.

The component composition of the precipitate,%: Ca - 32, P ₂ O ₅ - 43, F - 3, CO ₃ - 6, Cl - 0.1, H ₂ O - 1.

The calculated salt composition of the precipitate,%: CaHPO ₄ 82%, CaF ₂ 6.8, CaCO ₃ 10, CaCl ₂ 0.2, H ₂ O 1%.

The mass fraction of the carbonate ion was determined by the volumetric method on a calcimeter.

The chlorine content in the melt of ammonium nitrate is 0.001%.

The consumption of components is: 23 g of sediment per 77 g of melt.

The ratio of nutrient components in the resulting fertilizer is: N - 27.0%, P ₂ O ₅ - 9.2%, chloride content - 0.02%.

For the fertilizer obtained, thermal stability is determined.

The results are shown in the table.

Examples 4, 5 are shown in the table.

Example 6 (prototype)

A stepwise neutralization with ammonia of nitric acid with the addition of phosphoric and sulfuric acids, evaporation of the neutralized solution to a residual moisture content of 0.5% and granulation of the finished product.

The content of components in the finished product is: N - 32%, P ₂ O ₅ - 3%, S - 0.2%, chloride content - 0.02%.

The thermal stability of the obtained fertilizer sample is shown in the table.

Table Thermal stability of NP fertilizers No. p / p The content of components in the fertilizer,% Time before decomposition, min N P ₂ O ₅ Cl one 32,2 3.2 0.02 120 2 29.8 6.0 0.02 150 3 29.8 6.0 0.015 170 four 29.8 6.0 0.01 more than 180 5 27.0 9.2 0.02 180 Prototype 6 32 3 0.02 thirty

As can be seen from the data presented in the table, the introduction of phosphorus-containing calcium compounds as a phosphate additive increases the thermal stability of the fertilizer.

The lower limit of the content of P ₂ O ₅ in the fertilizer is determined by agrochemical requirements: when the content of P ₂ O _{5 is} less than 2%, the agrochemical value of the fertilizer decreases. The upper limit of the content of this component is determined by technological difficulties: the granulation process of mixed melt is complicated and the strength of the granules decreases.

The introduction of a phosphate additive in a solution of ammonium nitrate leads to complications in the evaporation of the mixed solution.

Claims (2)

1. A method of producing a complex nitrogen-phosphorus fertilizer based on ammonium nitrate with a phosphate additive, comprising the stepwise neutralization of ammonia with nitric acid, evaporation of a neutralized solution, the introduction of a phosphate additive and granulation of the product, characterized in that phosphorus-containing calcium compounds formed during phosphate addition are used separation of pre-ammoniated pulp obtained by nitric acid or hydrochloric acid opening of apatite concentrate. 2. The method according to claim 1, characterized in that the phosphate content in terms of P ₂ O ₅ in the fertilizer is 2-9 wt.%, Nitrogen - 27-32 wt.%.