SU71744A3 - The method of obtaining granular superphosphate - Google Patents

Description

Methods are known for producing granular superphosphate by agglomerating and drying crude superphosphate. The present invention relates to a method for producing solid grains with reduced fluorine content from raw superphosphate.

According to the proposed process, the raw material — the crude superphosphate — is mixed with finely powdered dry material, for example, with fully ripe powdered superphosphate, or phosphate-containing rock, or dust, obtained by sifting crushed superphosphate.

Water is added to the resulting mixture, the amount of which is minimized. This process step is a conditioning step, resulting in the formation of grains of the agglomerated material.

Air conditioning is carried out in a rotating drum. Water is supplied by jets directed inside the drum.

After agglomeration, the material enters the drying apparatus, where the grains are dried with constant stirring and precisely controlled mode of temperature and speed of passage from the awl

gases, with bringing the moisture content of the material to 4-6%. The established mode of drying ensures a decrease in the fluorine content by at least 35% against the initial one.

The change in the moisture content of the material during processing is characterized by the following indicators; freshly prepared superphosphate contains about 10.5% moisture. 1; air-conditioned material from the aggls generator is about the same humidity. When leaving the dryer, humidity decreases to 5%.

The ripened product, shipped to customers, has about 1.5% humidity, i.e., about 3.5% less. Studies have shown that the actual moisture loss during storage of the product (overfilling, carrying grain in warehouses, etc.) is only about 1.5%. The remaining 2% of the moisture enter into a chemical compound with the material.

Exact regulation of humidity and total consistency of superphosphate freshly prepared in the agglomerator provides a uniform grain size distribution, thanks to which screenings

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small things and large grains is negligible.

During processing, the following humidity limits should be observed: directly at the exit of the dryer - no higher than 8%, since the wetter product is soft and, although it hardens after cooling in the warehouse, its grains retain the ability to stick together; minimum humidity (the most important limit) is 4%, since a further decrease in humidity affects the maturation of superphosphate; optimum humidity - 5%. Practically with strict regulation of the regime, the optimal prtsept can be maintained with fluctuations from 4.5 to 5.5%.

According to experimental data, the chemical composition of the grains coming from the dryer, is as follows:

Moisture. g s. . . . 5.15% Total PsOs ..... 21.08% Absorbable PsOs. . . 18.33% Unassimilable PaOs. . 2.75%

Fresh grains ripen in stock for at least 10 days. Chemical composition of ripened grains:

Moisture1.67%

Total PaOs21.44%

Assimilable raOz. . . 20.26% Unassimilable P2O5. . 1.18% The process is regulated so that the finished product contains digestible PaOb slightly more than 20%, since the standard P2O5 content in the granular superphosphate is set at 20%.

Patent Subject

Claims (2)

1. A method of producing granular superphosphate by agglomeration and drying of crude superphosphate, characterized in that drying is carried out to a moisture content of 4-6% and bringing the fluorine content in the finished product to 1.1 - 1.45% in a list of 20% P2O5. 2. A method according to claim 1, characterized in that dry, finely divided superphosphate is added to the crude superphosphate.