SU1313841A1 - Method for defluorination of natural phosphates - Google Patents

Abstract

The invention relates to methods for solid-phase defluorization of natural calcium phosphates and can be used in the manufacture of fertilizers. The purpose of the invention is to improve the quality of the finished product due to an increase in the concentration of P OV in the assimilable form while maintaining a high degree of defluorization, as well as an increase in the productivity of the process. The method of de-fluorinating natural phosphates consists in pre-mixing the raw material with a liquid glass solution heated to 30-90 ° C with a density of 1.1-1.4 g / cm in an amount corresponding to 0.5-2.0% SiO by weight of phosphate. The resulting mixture is treated with phosphoric acid and served for heat treatment at 1100-1600 C in the presence of water vapor. 1 hp f-ly, 1 tab. with (L with

Description

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The invention relates to methods for solid-phase defluorization of natural calcium phosphates and can be used in the manufacture of fertilizers or mineral phosphate supplements for farm animals.

The purpose of the invention is to improve the quality of the finished product due to an increase in the concentration of P Oy in an assimilable form while maintaining a high degree of defluorization, as well as an increase in the productivity of the method.

The essence of the method is that the phosphate raw material is mixed with a pre-heated to 30-90 ° C solution of liquid glass, treated with phosphoric acid and subjected to heat treatment at 1100 - 1600 ° C.

It is advisable to use a solution of liquid glass with a density of 1.1-1.4 g / cm in the amount of 0.5-2.0% SiO by weight of the phosphate raw material.

The basis of the process of defluorization is the reaction of the interaction of the phosphate mineral with the products of the dehydration of calcium hydrophosphates, added to the raw material or formed at the stage of mixing with phosphoric acid,.

When feeding the reagents in a manner known per se, the acidic calcium phosphates added or formed at the mixing stage interact with the liquid glass by the reaction

(SiO) + Ca () ,. - -SAHPO + Na2HPO + nSiO, H, jO.

with the formation of compounds that, when heated, pass into low-active pyrophosphates. To carry out the defluorization reaction at a sufficient rate, an increase in the added reagents is required.

In the proposed method, first liquid glass is added to the phosphate raw material, which envelops the phosphate, mainly interacts with phosphoric acid or its subsequent addition by the reaction

NajO-nSiO + H PO - H ,,. PO fnE O + nSiO -. .

The formation of monosubstituted sodium phosphate (and in a small amount of calcium)

qi), which, upon dehydration, are transferred to active metaphosphates that react with a phosphate mineral at a high rate, provides

the high quality of the product and the intensity of the defluorization process already in the initial parts of the furnace with a reduced amount of liquid glass.

The use of pre-heating a solution of liquid glass to 30-90 ° C allows the use of dilute solutions that ensure good mixing with the phosphate raw material, which also intensifies the process,

increases yield in assimilable form and reduces the consumption of activating additives.

The use of liquid glass in the form of a concentrated flow and the

more, silicate blocks worsen the contact of reagents. Therefore, to obtain a product of standard quality, an increase in their quantities is required. It is recommended to introduce liquid glass with a specific density of 1.1-1.4 g / cm. The table shows the results of experiments on defluorization of Kovdorsky apatite (CaO 53.4%; 36.0%), where the addition of liquid glass (in terms of

on SiOj) it is 1.0%, phosphoric acid (c. in terms of PjOy) is 7.0%, the firing temperature is 1350 ° C,

As can be seen from the table, the decrease

the heating temperature of the liquid glass solution less leads to a decrease in the defluorization and a decrease in the productivity of the furnace, and an increase in temperature by 90 ° C with

use as a heating agent - waste steam is not feasible, since such a temperature is not technologically achievable,

Lowering the temperature to less than 30 ° C requires the use of liquid density glass (above 1.4 g / cm) to prevent the formation of a pasty mass that is difficult to apply.

in the furnace due to clogging of the leakage, which does not allow to achieve the required degree of homogenization when mixing the components and causes a sharp decrease in productivity, worsens the de-energizing and the quality of the product.

It was experimentally shown that in the proposed conditions the introduction of liquid glass in the amount of 0.5-2.0%

313

SiOj to the mass of phosphate (0.03-0.1 mol of SiO / PjOy). Provides good absorption with high intensity and obtaining a product containing no more than 0.2% F and 39-43% in digestible form. A decrease in the density of the liquid glass solution to less than 1.1 g / cm leads to the formation of a mixture with high moisture content at the mixing stage, which causes disruption of the granulation process, and clogging of the leaks. An increase in the density of the liquid glass solution above 1.4 g / cm leads to poor homogenization when mixed, which causes an increase in the number of added activating reagents.

Example -1. Liquid glass (5.1% and 15.6% SiO) with a density of 1.1 g / cm is heated to 90 ° C and mixed in a screw mixer with the Kovdorsky apatite concentrate (35.8%, 53.2% CaO) in an amount of 125 kg / t apatite (2.0% SiO). An acid with a concentration of 50% 2 is added to the mixture obtained in the amount of 140 kg / ton of apatite.

The charge in the amount of 10 tons per hour enters the 100-meter rotary kiln where it is heated to 1350 ° C. The resulting product contains,%: commonly. 42.6; sr 42.0; F 0.13.

PRI mme R 2. Liquid glass (23.2% SiO and 7.6%) with a density of 1.4 g / cm, heated to 30 ° C, is mixed in an auger mixer with an apatite concentrate (36.8% 52.3 % CaO) in the amount of 26 kg / t apatite (0.5% SiOj). To the mixture was added 130 kg of phosphoric acid with a concentration of 50%. The 8 t / h charge enters the 100 m rotary kiln, where it gradually heats up to 1350 s. The resulting product contains,%: commonly. 42.8; .r 42.2; F 0.18.

Example 3. Liquid glass (6.6% and 21.0% SiOa) with a density of 1.25 g / cm, heated to, is mixed with apatite concentrate (36.8%. And 52.3% CaO) in an amount of 50 kg. / t apatite (1.0% Zyug). To the mixture was added 130 kg of phosphoric acid with a concentration of 50% P-j Oj. The mixture in the amount of 9 t / h enters the 100-meter rotary kiln, where gradually at 3841 .4

heated to 1350 ° C. The resulting product contains,%: commonly. 42.5;

 sr

42.1; F 0.13.

Thus, the proposed method allows to improve the quality of the finished product by increasing the concentration in the hydrochloric acid form while maintaining a high degree of de-fluorination (not more than 0.2%) and reduced consumption of input components, as well as increasing the productivity of the process to 8-10 t / h

Claims (2)

1. A method of defluorinating natural phosphates, including the processing of phosphate raw materials with phosphoric acid, mixing with liquid glass, thermal treatment in the presence of water vapor, characterized in that, in order to improve the quality of the finished product by increasing the concentration of PjOj in it in an assimilable form while maintaining a high degree of defluorization, as well as increasing the productivity of the process, phosphate raw materials before phosphorus processing acid is mixed with a pre-heated to 30-90 ° C solution of liquid glass. 2. Method according to P-. 1, that is, in order to use a solution of liquid glass with a density of 1.1-1.4 g / cm in an amount corresponding to 0.5-2.0% SiO by weight of the phosphate raw material.