RU1839167C - Method for briquetting phosporogypsum - Google Patents

Description

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Chad

Sh.

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The invention relates to a technology for processing gypsum-containing materials, in particular to methods for briquetting phosphogypsum - a waste product from the extraction of phosphoric acid, and may find application in the production of cement, building materials, as well as in agriculture for soil treatment.

The purpose of the invention is to increase the strength of briquettes and reduce energy costs.

The method is carried out as follows.

Phosphogypsum with hygroscopic humidity of 20-25 wt.% Repulse in water at a ratio of 3-1.6. The resulting slurry is filtered to obtain cake containing 10-15 wt.%, Moisture. The isolated cake is dried with gta / heme dispersion in a gas stream at 90-300 ° C and a speed of 10-25 m / s to obtain a product with a particle size of 1-5 mm and a humidity of 0.1-4.0 wt.%, Followed by pressing by rolling under pressure of 300-2000 MPa in plates with a thickness of 4-10 mm.

The method allows to increase the strength of phosphogypsum briquettes under compression up to 10-25 MPa, to reduce energy consumption in the process of dehydration of the material by 25-30%.

EXAMPLE 1 Phosphogypsum with an initial hygroscopic humidity of 25% by weight is diluted with water to a water-solid ratio of 1.6 in a batch repulpator. Then, the resulting slurry is pumped into a precipitating two-stage centrifuge. At the first cascade of the centrifuge, phosphogypsum is additionally washed, and the filtrate containing Pads is returned to the production cycle of the extraction of phosphoric acid. In addition, up to 1% is additionally recovered. In the second cascade of centrifuges, phosphogypsum is washed with lime milk with a content of 3% Ca (OH) 2 (in terms of dry substance) during filtration of the sludge until the filtrate reaches a pH of 7. Filtration is completed when cake is obtained with a moisture content of 13 wt.%, Which is then they are sent for drying to the dryer pipe, where it is dispersed (broken) by a stream of gas sor at a speed of 18 m / s. The temperature of the gases in the working zone is 170 ° C; the time of dispersion and drying to a moisture content of 2.5% by weight is 3 minutes. In this case, phosphogypsum is obtained in the form of porous grains with a size of 1-5 mm in an amount of 90-92%. smaller grains comprise 8-10%. Phosphogypsum prepared in this way is pressed on a roller press with a pressure roll.

1200 MPa in 7 mm thick plates. Due to the mismatch of the roll rotation speed by 0.1%, the plates are divided into measuring pieces measuring 10-20 mm. The temperature of the phosphogypsum being pressed is 100 ° C. and in the course of pressing in 0.02 s the material is heated to 120 ° C. Since the process of heat exposure (dislocation + pressing) is a little over 3 minutes, the material practically does not dehydrate and the final product - granules are composed of calcium bicarbonate.

Physico-mechanical properties of the granules are given in table. 1.

Example 2. Phosphogypsum with an initial free moisture content of 20% by weight is repulped, water is added to a water-solid ratio of 1.45. Then the sludge is passed through a hydrocyclone, at the outlet of which phosphogypsum is aerated (blown in an air stream) and a cake with a 10% free moisture content is obtained. During feeding into the hydrocyclone, the milk of lime is introduced into the sludge in an amount providing a filtrate of pH 7.5. The resulting cake is dispersed in a gas stream at a speed of 25 m / s at 300 ° C and the humidity of phosphogypsum is adjusted to 0.1 wt.% Within 2 minutes. Thus dehydrated phosphogypsum in the form of grains 1-5 mm in size (up to 85%, the remaining grains less than 1 mm) is fed to a roller press, where it is pressed under a pressure of 2000 MPa for 0.01 s into 4 mm thick plates with a size of 3-10 mm The material arriving for pressing has a temperature of 120 ° C, and during compression is heated to 170 ° C. After screening on a screen, the granules are transported to a warehouse, and particles smaller than 3 mm and more than 10 mm are crushed and returned to the production cycle.

The properties of the granules are given in table. 1.

Example 3. Phosphogypsum with an initial moisture content of 22 wt.% Repulpate, diluted with water in a ratio of .3. The slurry is sent to a filter press. In the process of pumping, milk of lime is introduced into the sludge until a pH of 8 is obtained. After filtration, the cake is dispersed in a gas stream at a speed of 10 m / s at 90 ° C and adjusted to a moisture content of 4 wt.% With a grain size of 1-5 within 5 minutes mm (up to 95%, the rest - grains less than 1 mm). Thus dried phosphogypsum is pressed on a rolling mill under a pressure of 300 MPa for 0.01 s into 10 mm thick plates with a size of 3-50 mm. For pressing phosphoshpg comes with temperature. n g-+, -i is heated to 95 ° C. The finished product is sent to the warehouse.

The conditions for the implementation of the method for gri-ierem, reflecting the extreme and average

values of parameters, and in comparison with prohibitive values are presented in table,

Thus, the proposed method), compared with the known method, makes it possible to obtain phosphogypsum granules with a strength greater than 8–9 times, while reducing the energy consumption for preliminary dehydration of the product by 25–30%.

(56) Copyright certificate of the USSR No. 925867. cl. C 01 F 11/46, 1980.

USSR copyright certificate IM 494364. cl. From 04 to 11/02. 1974.

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Table 1

Claims (1)

The claims METHOD OF PHOSPHOGIPS BRIQUETTING, including filtration of phosphogypsum sludge, drying of the obtained cake with subsequent pressing, characterized in that, in order to increase the briquette strength and reduce energy consumption, sludge is subjected to filtration from 0 by a Zh / T solution of 1.3 - 1.6 to obtain a cake with a moisture content of 10-15 wt.%, drying of the cake obtained is carried out by dispersing in a gas stream at 90 ° C and at a speed of 10-25 m / s to obtain product with a particle size of 1 to 5 mm and a moisture content of 0.1 to 4.0 wt.%, followed by pressing by rolling under a pressure of 300 to 2000 MPa into plates with a thickness of 4-10 mm.