LT4440B - Method for processing of phosphogypsum into mineral filler - Google Patents

Abstract

This invention can be used to produce technical rubber, artificial skin, paint, polymer products, civil engineering daubs and other products. The method for reprocessing phosphogypsum consists in the following processes: neutralisation by lime, vacuum-filtration, mincing of the product and burning at a specific temperature.

Description

The invention can be used in technical rubber articles, imitation leather, paints, polymeric articles, building coatings, etc. in the industry.

The extraction of phosphoric acid from apatites results in the production of phosphogypsum, which consists mainly of calcium sulphate dihydrate. The waste from this production pollutes the environment and the groundwater, so their recycling into technical products is promising.

There is a known way to make β from phosphogypsum. calcium sulphate pushhydrate (Authorization No. 1224287 of 15 April 1986). Phosphogypsum is fed into a reactor containing a lime suspension of 5-25 g / l CaO. Lime extinguishing time 10-30 minutes. The rate of decrease in the pH of the lime suspension depends on the amount of phosphorus, fluorine, etc. present in the phosphogypsum. concentration of acid compounds, initial concentration of lime suspension, mixing intensity. The pH of the lime suspension is controlled by adjusting the amount of phosphogypsum in the suspension. The rate of pH reduction of the lime suspension is as follows: pH 12.8-12.0 not more than 0.16 pH units / min, pH 12.0-6.5 not more than 0.6 pH units / min.

The process is controlled continuously by automatically measuring and recording the pulp pH curves, which must remain within the set limits throughout the neutralization process.

Phosphogypsum is fed to the reactor until the pulp pH is reduced to 6.5 and the water-solids ratio reaches one unit. After 10 minutes, this slurry is pumped into a drum vacuum filter and the filtered 27% moisture product is dried in a drum dryer to 2% humidity, then dehydrated in a gypsum boiler to a push tube.

We propose to make mineral fillers from phosphogypsum, which will replace natural chalk, thus reducing production costs in the technical rubber products, artificial leather, paints, post-limeric products, building putty etc. according to the following technological scheme:

Phosphogypsum dump

O

Excavation

O

transporting

O

Rough sieving

O

Flushing with water

O

Deposition

O

Neutralization

O

O

Grinding

O

Vacuum filtration

O

Combustion

O

Cooling

O

Pronunciation

O

Warehousing

Phosphogips is dumped in a landfill by a single-shovel excavator, loaded onto a dump truck or railroad platform and transported to a workshop for processing into mineral aggregates. The phosphogypsum is sieved with a vibrating sieve with a mesh size of 100 x 100 mm to separate large mechanical impurities. The screened phosphogypsum is fed into the sludge pool, which is equipped with a mixer and is flushed with water. Phosphogypsum is added to the sludge pool until the water solids ratio reaches 1-4.

Larger mechanical impurities, which were not separated by a vibrating sieve during coarse seeding, settle on the bottom of the sludge pool and therefore periodically purge the sludge pool from mechanical impurities.

The pulp from the sludge pool is pumped into the sand traps. Depending on the size of the sand particles that you want to settle, the pulp in the sand sedimenter lasts from a few to several hours.

The sludge from the sand setters is pumped into a reactor containing a pre-made lime suspension with a CaO (active) concentration of 0.2-3% by weight. Lime extinguishing time 10-30 minutes. The pH of the lime suspension is maintained at the following rate: pH 12.8-12.0 not more than 0.16 pH units / min, pH 12.0-6.5 not more than 0.6 pH units / min. The phosphogypsum pulp is fed to the reactor until the pulp pH drops to 7.5-8.5. The pulp is kept in the reactor for 10 minutes. The neutralization process is controlled by an automatic pH meter, measuring and recording the pulp pH curves.

The neutralized phosphogypsum pulp is pumped into a ball mill, which, depending on the duration of the milling process, achieves the required grinding fines, which must be at least 400 m ² / kg, depending on the use of mineral fillers.

The powdered phosphogypsum pulp is pumped into a vacuum filter, where it filters up to 15-20% moisture. The filtrate is pumped to produce a lime suspension.

The filtered mass of phosphogypsum is burned in a rotary kiln at 450-500 ° C with 15-20% moisture. Burning time 1-1,5 hours.

The burnt phosphogypsum is cooled to 50-65 ° C, 25 kg in polyethylene or paper bags, sealed and stored in a closed warehouse.

Claims (3)

DEFINITION OF INVENTION A process for the processing of phosphogypsum, comprising flushing with water, settling, milling, vacuum filtration, combustion, characterized in that the phosphogypsum is milled to a level of at least 400 m ² / kg after neutralization. 2. The process for processing phosphogypsum according to claim 1, wherein the phosphogypsum is burned at 450-500 ° C for 1-1.5 hours. 3. Use of the product obtained by the processing of phosphogypsum as a technical filler for mineral chalk substitutes in the manufacture of rubber products, imitation leather, paints, polymeric products, building coatings.