SU688488A1 - Method of preparing complex fertilizers from phosphate ores - Google Patents

Description

one

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

Methods are known for producing complex fertilizers by nitric acid processing of phosphorites, which provide for the necessary separation of calcium salts and phosphate ions, achieved by freezing calcium nitrate, by binding calcium B sulfate or carbonate by introducing into the reaction additional amounts of phosphoric acid, which reduces the CaO: P2O ratio 5 or extraction of phosphoric acid with organic solvents.

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

Closest to the described method of obtaining complex fertilizers, consisting in decomposing phosphate with dilute nitric acid with a concentration of from 1.0 to 6.0 weight. %, at 4-26 ° C and the ratio of T; G In the pulp 1: 10-25. The nitrophosphoric acid stretch is then separated from the insoluble precipitate and neutralized with ammonia. The resulting slurry fertilizer pulp is filtered, the precipitate is dried and granulated.

In the process of phosphorite decomposition by nitric acid, nitrogen oxides are released, actively interacting with harmful impurities — iron and aluminum; part of OXIDES pollutes the atmosphere and prevents the insoluble residue from settling after selective leaching.

The purpose of the invention is to increase the selective extraction of phosphorus from phosphate-containing ores while reducing the release of nitrogen oxides to the environment.

The goal is achieved by the fact that the process of decomposed ore with dilute acid is carried out in the presence of ammonium carbamate at a concentration of the latter in the pulp In the range of 0.01-0.1 vol. %

A distinctive feature of the process is that the decomposition process is wedge in the presence of ammonium carbamate, which reacts with nitrogen oxides to form nitrogen, carbon dioxide and water.

Claims (1)

Results showing the effect of ammonium carbamate injected into the reaction mixture on the process selectivity coefficient are presented in the table. It follows from the table that the introduction of insignificant amounts of ammonium carbamate during the decomposition process sharply increases the selectivity of the process, since the solubility of harmful impurities of iron and aluminum entering the glauconitic crystal lattice decreases with a decrease in the release of nitrogen oxides. The addition of carbamate above 0.1% does not affect the growth of selectivity, since basically all of the extracts and nitrogen oxides are practically bound by ammonium carbamate. The excretion of nitrogen oxides in the surrounding medium at selective high, the yelichivan of phosphate is significantly reduced when the concentration of ammonium carbamate is 0.01%, and with an increase in the concentration of carbamate to 0.1%, the excretion of oxides becomes 1.0-10%. The further addition of ammonium carbamate does not affect the reduction in the release of nitrogen oxides, which can be explained by the kinetic factors of the reaction and is associated with the level of partial equilibrium of diluted nitric acid. Example. 200 g of ore from the Verkhnekamskoye deposit are placed in a 2.5 l reactor, 2000 ml of 6% nitric acid (T: W 1: 10) are added, 2.2 g of ammonium carbamate are added and mixed for 10 minutes. The concentrations of substances in solution and in the gas phase are measured. Then filtered, the sludge and the resulting solutions are analyzed. The filtrate is ammoniated to a pH of 6.3. The resulting pulp is filtered, the resulting precipitate is dried and granulated. The content of the assimilable form of P2O5 is 78-81%, water-soluble 14-16%, with a total content of 35-40% and nitrogen 15-20%. Production of complex fertilizers from phosphate ores according to the proposed method provides the following advantages compared to the known ones: the possibility of selective processing (the coefficient of selectivity of decomposition increases from 9.01 to 12.01, i.e. by 33%) iron and aluminum-containing phosphate ores into high-quality phosphorus and nitrogen-containing fertilizers; reducing the concentration of nitrogen oxides released into the environment to the level of the MPC; improving the processability of the process (conditions of separation of the slime and the leaching solution). The method of obtaining complex fertilizers from phosphate ores by decomposing phosphate with dilute nitric acid, followed by neutralization, drying and granulation of the final product, characterized in that, in order to increase the selectivity of phosphorus extraction from phosphate ores while reducing the release of nitrogen oxides into the environment, decomposition lead in the presence of ammonium carbamite at a concentration of the latter in the decomposing pulp in the range of 0.01-0.1 vol. %