SU1460058A1 - Method of defluorination of phosphate raw material - Google Patents

Abstract

The invention relates to a process for the processing of phosphate phosphate, containing up to 70% silicates in terms of SiO. The method involves mixing silicate-containing phosphate raw material with phosphoric acid preheated to 40-95 ° C, granulating the resulting mixture and firing it, while phosphoric acid is fed to the mixture in an amount that provides the ratio in the processed CaO: (P205- + SiO) equal to 1 1-1.25. 2 tab.

Description

The invention relates to a process for the processing of phosphate raw materials containing silicates into defluorinated phosphates.

The aim of the invention is to prevent the formation of melts and wallings during the heat treatment of phosphate raw materials with a high concentration of silicates in it while maintaining a high degree of de-fluorination of the finished product.

The method of processing phosphate, raw materials containing silicates up to 7% in terms of SiO involves mixing it with phosphoric acid, granulating the resulting mixture and burning it, with the phosphoric acid being preheated to 40-95 ° C and fed to the mixing in the amount of providing a ratio in the processed raw material CaO: (+ S) equal to 1.1-1.25.

Phosphate phosphate contains silicates — in the form of forsterite, antigorite, and phononite, whose presence as well as the products of interaction with phosphoric acid is determined by the amount of the liquid phase in the defluorinating zone of the material. Therefore, by adding phosphoric acid to such raw materials to obtain a CaO: P2 / P5 ratio of 1.1-1.2, as in the known method, leads to the formation of an excess amount of the liquid phase. Raw materials begin to actively dissolve in it, forming melts. The presence of intermediate fluorine ions in the liquid phase accelerates the process of melt formation. During the processing of raw materials containing reduced amounts of silicates, but elevated levels of calcium, for example in the form of calcite, the amount of the liquid phase decreases as a result of interaction with it

ABOUT)

SP

(50

1460058

calcium with the formation of high-temperature phosphate-calcium compounds.

Thus, the amount of liquid phase determines the optimal conditions for the processing of phosphate raw materials into de-fluorinated phosphates. The regulation of this process is carried out by varying the ratio of the reactants forming the liquid phase. Since the starting reagents are phosphoric acid and silicates, changing their amount (.SiO) in a wide range allows you to successfully carry out the process without the formation of melts and scum to obtain a high-quality product on fluorine content.

Heating of phosphoric acid to 40-90 ° C allows, when it is mixed, to carry out a partial decomposition of silicates, which speeds up the defluorization of the material with an increase in its thermal stability.

Silica compounds, as well as alkali metal silicates or aluminosilicates, are present in the raw materials as silicate compounds.

The effect of phosphoric acid preheating on the processing of the mixture in the ratio of CaO: (Pji05- + SiOj) equal to 1.15 is illustrated in Table 1.

Acid temperature below 40 ° C shows a low reactivity with silicates, which does not prevent the formation of melts in the furnace. Temperature rise above 95 ° C is not feasible due to the increased corrosion of the equipment

The effect of the ratio of CaO: (+ SiOj) in a mixture at a temperature of phosphoric acid, W ° C, on the formation of melts and walling in the furnace is given in Table 2.

When the CaO: (+ SiO) ratio is equal to 1.05, melts and walling are formed due to an increased amount of the liquid phase in the material.

 An increase in the CaO: - (SiO,) ratio greater than 1.25 ensures the heat resistance of the furnace material, but due to the reduced amount of the liquid phase, the process is slowed down, therefore, while maintaining the furnace performance, the quality of the product deteriorates and

0

0

 fluorine.

the fluorine content in it exceeds the permissible amount (0.2%).

Thus, the regulation of the ratio in a mixture of CaO: (+ SiO) in the range of 1.1-1.25 in the processing of raw materials containing silicate impurities 2-7% in terms of SiO. provides the ability to conduct the process without violations to obtain a quality product on the content of fluorine.

Example 1. 1000 kg of phosphate raw materials containing 2.1% silicates 5 in terms of SiOj are mixed with phosphoric acid, taken in an amount of 85 kg, with a temperature of 40 ° C to obtain a CaO: (+5102) ratio equal to 1 , 1, in the product and burned in the kiln. Boiling layer. No melt or bulk is formed. The fluorine content in the product is 0.14%,

Example 2: 1000 kg of phosphate raw materials containing 4.5% silicates 5 in terms of SiO, are mixed with phosphoric acid, taken in an amount of 55 kg, with a temperature of 50 ° C to obtain a CaO ratio: (SiO,), equal to 1.17, in the product and burned in a rotary kiln. Melt and wallings are not formed. The fluorine content in the product is 0.12%.

Example 3: 1000 kg of phosphate raw materials containing 7% silicates in terms of SiO are mixed with phosphoric acid, taken in an amount of 45 kg, with a temperature of 60 ° C to obtain a CaO: ratio (equal to 1.25, in the product and burned, g, in a rotary kiln. No melt or buildup is formed. Soderhanie fluoride a in the product 0.17%.

Thus, the proposed method allows the process to be carried out. fluorination of phosphate raw materials with a content of 2.5-7% silicates in terms of SiO without the formation of melts and scraps to obtain a finished product containing not more than 0.2%

35

 fluorine.

55

Claims (1)

Formula invented and A method of defluorinating phosphate raw materials, including mixing it with phosphoric acid, granulating the resulting mixture and annealing it, characterized in that, in order to prevent the formation of melting, 514600586 During heat treatment, BOB and walling phosphoric acid is heated to 40-phosphate feedstock with a high concentration of 95 ° C and fed to the mixture of silicates in it at the same time, providing a ratio in the exchange preservation of a high degree of raw material CaO: (+ SiO) , defluorinate the finished product,. equal to 1.1-1.25. Table 1 Melt formation, walling Yes No No No No Pet No Ratio CaO: (PjOg- + SiO) 1.05 1.1 1.15 1.2 1.25 1.3 Melt formation, walling Yes No no no no no Table 2