SU842081A1 - Method of producing complex fertilizer from carbonate-containing phosphate ores - Google Patents

Description

one

The invention relates to methods for producing complex complex fertilizers and can be used in the direct chemical processing of magnesium-containing phosphate ores.

Methods are known for producing complex fertilizers by nitric acid decomposition of phosphorites followed by the necessary separation of calcium salts and phosphate ions, which is achieved by freezing calcium nitrate, binding calcium to sulfate or carbonate by introducing into the reaction additional amounts of phosphoric acid, which reduces the CaO - ratio. or extraction of phosphoric acid with organic solvents.

After extracting a part of calcium in the form of calcium nitrate (freezing method) or binding it with sulfuric, carbonic, phosphoric acids or their salts, the solution is ammoniated, then subjected to evaporation 1.

However, such methods have a low extraction selectivity, i.e. high content in solution after leaching of harmful impurities:, AlaO-2) and MgO, as well as significant

excretion of nitrogen oxides into the environment.

The closest in technical essence and the achieved result to the proposed is a method of obtaining complex fertilizers from carbonate-containing phosphate ores by treating them with dilute nitric acid, separating sludge with subsequent

0 by neutralizing the solution with ammonia, filtration, drying and granulating. the end product.

According to this method, ore containing carbonate impurities (mainly magnesium) is treated with dilute (1.0–6.0%) nitric acid with and the ratio T: W in the pulp 1: 10–25. After separation

0 sludge sludge solution is neutralized with ammonia to pH 6-6.3, the resulting slurry is filtered, and the precipitate is dried and granulated 2.

However, in the process of decomposition of carbonate-containing phosphate, significant carboxylic dissolution occurs. which leads to contamination of the acid extract with magnesium, which impairs the properties of the resulting fertilizers,

0 and reduces the selectivity of extraction

phosphorus, while nitric acid is not productively consumed.

The use of nitric acid for decomposition at the indicated temperatures does not allow eliminating the release of nitrogen oxides, which actively interact with harmful impurities (iron and aluminum) and reduces the selectivity of extraction. A large amount of oxides is released into the atmosphere, which leads to pollution of the environment. The released nitrogen oxides float the insoluble residue and interfere with its settling and separation.

The purpose of the invention is to increase the selectivity of the extraction of phosphorus while simultaneously reducing the release of nitrogen oxides to the environment.

This goal is achieved by the fact that in the known method of obtaining complex fertilizers from carbonate-containing phosphate ores by treating them with a weak nitric acid.

4.0 CHNOj 4%

- with

The treatment is carried out in a stream of carbon dioxide with a concentration of 3.44, 5 kg / m at a temperature from 0 to -. .

A distinctive feature of the method is that the treatment is carried out in a stream of carbon dioxide at minus temperatures of the pulp.

With a decrease in temperature in the presence of carbon dioxide, the rate of decomposition of magnesium and calcium carbonates decreases sharply, the rate of dissolution of iron oxides and aluminum also decreases, and the release of nitrogen oxides into the environment decreases.

In tab. Table 1 presents the results showing the effect of decomposition temperature at a constant value of CO concentration on the selectivity of this process and on the release of oxides of nitrogen 0, and in Table. 2 — the effect of the concentration of CO, j at a constant temperature on the same process indicators.

Table

t -6 ° C; DRAIN 4%

Table 2

, -3

4.4-10 6.8- 10

-3

9.7. 10 2.9.10

-4 3.0. ten

From tab. 1 and 2 it follows that the optimal temperature range of the process is in the range from 0 to and at a concentration of carbon dioxide gas in the pulp from 3/4 to 4.5 kg / m

Example. A 500 mL 6% HNOj is poured into a jacketed reactor for cooling with a capacity of 800 ml, which is cooled to -6 ° C, and 50 g of ore () is charged with intensive stirring for 2025 min, maintaining the temperature in the reactor constantly and the concentration of CO, j is equal to 4.2 kg / m.

Selectivity of extraction taking into account

MDO, Kg

Extract target component

P Oy in solution,%

Removing impurities,%

Then the sludge is filtered, the filtration capacity is measured, the filtrate is analyzed, and then neutralized with ammonia to, 3. The resulting pulp is filtered, the resulting compound fertilizer is dried, granulated and analyzed. The content of the assimilable form of Р2 О582-90%, of the water-soluble form of P.2.% Is 15-20% with the total content of 32-35%, N 13-16%.

The presence of other components is shown in Table. 3, which provides comparative data of the known and proposed methods.

Table3

9.3-11.6 98.8

Claims (1)

Claim A method for producing complex fertilizer from carbonate-containing phosphate ores by treating them with diluted nitric acid, separating sludge, followed by neutralizing the solution with ammonia, filtering, drying and granulating the final product, characterized in that, in order to increase the selectivity of phosphorus extraction while reducing the emission of nitrogen oxides into the environment medium, acid treatment is carried out while the pulp is saturated with carbon dioxide to a concentration of 3.4-4.5 kg / m ³ and at a temperature of 0 to -10 ° C.