Method for preparation of granulated phosphogypsum

FIELD: technological processes; construction.

SUBSTANCE: invention solves problem of how to involve mass industrial waste phosphogypsum into production cycle as analog of construction material of natural origin. Method for preparation of granulated phosphogypsum includes mixing of initial phosphogypsum with binder and further rolling of mixture, at that binder used is return powder of phosphogypsum produced in mode of granulated material thermal treatment at the temperature of 170-200°C and its further crushing, at that portion of material recycle makes mostly up to 0.5 of total flow.

EFFECT: reduction of expenses in process of granulated phosphogypsum production.

4 ex

 

The invention relates to the production of building materials and can be used for granulation of phosphogypsum applied as a regulator of times of setting of cement and cementitious materials instead of natural gypsum stone.

There is a method of granulating phosphogypsum [USSR author's certificate No. 710616, CL 01J 2/28]. According to the method of phosphogypsum with a humidity of 25% is mixed with a solution of nitric acid, after which the resulting mass is fed into the granulator, and then the obtained granules are subjected to dusting carbonate agent, such as chalk.

The disadvantage of this method are the use of aggressive substances, the presence of which has a negative impact on the quality of cement and binders.

Known as the method of granulation of phosphogypsum by mixing it with a mixture of slag Portland cement and sodium sulfate, taken in an amount of 5-10 and 0.5-2%, respectively, of the dry weight of phosphogypsum, rolling the mass into the granulator followed by drying the pellets to a moisture content of 8 to 13% [USSR author's certificate No. 1446109, CL 01J 2/28]. The disadvantage of this method are the low strength of granules, their tendency to stick together.

Closest to the claimed adopted for the prototype, is a method of obtaining a granulated phosphogypsum, comprising mixing the placenta is it with cement dust and rolling the mixture, characterized in that obtained after rolling the pellets are subjected to a dusting of mineral fine powder with a specific surface area of 300-500 m2/kg [RF patent №2087420, CL 01J 2/28]. The disadvantages of the prototype should include double transportation costs associated with the use of cement dust.

The technical objective of the proposed solutions is to reduce costs. The specified technical task is achieved in that in a method of producing granulated phosphogypsum, comprising mixing the original with astringent and rolling the mixture, wherein the binder of the reflexive powder phosphogypsum produced by heat treatment of the granules at a temperature of 170-200°and further grinding, while the share of recycling material is preferably up to 0.5 percent of total flow.

The essence of the proposed method is that the final product is a granular material is divided into two streams. One of the threads removed from the cycle as a commercial product. The second stream is subjected to grinding and mixed with the original phosphogypsum. Source phosphogypsum powder waste in industrial production, mainly in the form dowolnego calcium sulphate. His mixing with semi-aquatic form of calcium sulfate in the mode of granulation with an aqueous solution provides the t necessary strength of the granules. On the basis of experimental data it is established that the shredding and recycling enough to send not more than 0.2 flow while increasing the share of recycling leads to hardening of the granules. The return of more than 0.5 flow has no effect on increasing the strength of the granules, but significantly impairs the technical-economic indicators of production. The essence of the proposed method is confirmed by the examples.

Example 1. Used phosphogypsum dump Sredneuralskaya smelter. For modeling process applied laboratory plate granulator and drying Cabinet type SNOL temperature-controlled. The first portion of the mixture of phosphogypsum source and standard of gypsum at a ratio of 8:2 with total mass of one kilogram was granulated in the mode conversion using water. After granulation 80% of the product was withdrawn from the cycle. 20% was subjected to heat treatment at a temperature of 170-200°C for 2 hours. Powdered and heat-treated powder was used as a binder in the next cycle with a fresh portion of phosphogypsum source. In the present mode performed 5 cycles. Received 4 kg of granulated phosphogypsum. The obtained pellets of phosphogypsum have an initial compressive strength of 1-1,4 MPa

Example 2. Used heat-treated and ground phosphogypsum obtained in example 1. The ratio of the main stream is recycled to was 6:4. Conducted five cycles. Received 3 kg of granulated phosphogypsum. The obtained pellets of phosphogypsum have an initial compressive strength of 1.5-1.8 MPa.

Example 3. The ratio of the main stream recycled to 5:5. Conducted 5 cycles. Received 2.5 kg of granulated phosphogypsum. The initial compressive strength of 2.1 to 2.2 MPa.

Example 4. The flow ratio of 6:4. Conducted 5 cycles. Received 2 kg of granulated phosphogypsum. The initial compressive strength of about 2.2-2.3 MPa.

Thus when implementing the proposed method achieves the formation of a granular product without the use of extraneous additives that extends the range of application of the material, similar to the natural gypsum stone.

A method of obtaining a granulated phosphogypsum, comprising mixing the original with astringent and then rolling the mixture, wherein the binder of the reflexive powder phosphogypsum produced by heat treatment of the granules at a temperature of 170-200°and further grinding, while the share of recycling material is mainly up to 0.5 of the total flow.



 

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