RU2345828C1 - Method for preparation of granulated phosphogypsum - Google Patents

Abstract

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.

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Description

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

A known method of granulating phosphogypsum [USSR copyright certificate No. 710616, class. B01J 2/28]. According to this method, phosphogypsum with a moisture content of 25% is mixed with a solution of nitric acid, after which the resulting mass is fed to a granulator, then the granules obtained are subjected to dusting with a carbonate agent, for example chalk.

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

There is also known a method of granulating phosphogypsum by mixing it with a mixture of slag Portland cement and sodium sulfate, taken in amounts of 5-10 and 0.5-2%, respectively, of the mass of dry phosphogypsum, rolling the resulting mass into a granulator, followed by drying of the granules to a moisture content of 8-13% [USSR copyright certificate No. 1446109, cl. B01J 2/28]. The disadvantage of this method is the low strength of the granules, their tendency to stick together.

Closest to the claimed adopted as a prototype is a method for producing granular phosphogypsum, comprising mixing the latter with cement dust and rolling the mixture, characterized in that the granules obtained after rolling are subjected to dusting with mineral fine powder with a specific surface of 300-500 m ² / kg [patent RF №2087420, class B01J 2/28]. The disadvantages of the prototype include double transportation costs associated with the use of cement dust.

The technical task of the proposed solution is to reduce costs. The specified technical problem is achieved by the fact that in the method of producing granular phosphogypsum, including mixing the starting material with a binder and rolling the mixture, characterized in that the binder used is phosphogypsum powder obtained in the heat treatment mode of the granulate at a temperature of 170-200 ° C and subsequent grinding, wherein the proportion of material recycling is preferably up to 0.5 of the 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 flows is withdrawn from the cycle as a commercial product. The second stream is ground and mixed with the original phosphogypsum. The initial phosphogypsum is a powdery industrial waste product mainly in the form of calcium bicarbonate. Its mixing with the semi-aquatic form of calcium sulfate in the granulation mode with an aqueous solution provides the necessary strength of the granules. Based on experimental data, it was found that no more than 0.2 flow is sufficient to grind and recycle, while increasing the proportion of recycle leads to hardening of the granules. The return of more than 0.5 flow does not affect the increase in the strength of the granules, but significantly worsens the technical and economic indicators of production. The essence of the proposed method is confirmed by examples.

Example 1. Used phosphogypsum dump Sredneuralskogo smelter. To simulate the process, a laboratory plate granulator and a temperature controlled SNOL drying oven were used. The first portion of the mixture of phosphogypsum of the initial and standard gypsum at a ratio of 8: 2 with a total weight of one kilogram was granulated in the rolling mode using water. After granulation, 80% of the product was removed from the cycle. 20% were subjected to heat treatment at a temperature of 170-200 ° C for 2 hours. The ground heat-treated powder was used as a binder in the next cycle with a fresh portion of the initial phosphogypsum. In the presented mode, 5 cycles were carried out. Received 4 kg of granular phosphogypsum. The obtained granules 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 to recycled was 6: 4. Conducted five cycles. Received 3 kg of granular phosphogypsum. The obtained granules of phosphogypsum have an initial compressive strength of 1.5-1.8 MPa.

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

Example 4. The ratio of the streams 6: 4. Conducted 5 cycles. Received 2 kg of granular phosphogypsum. The initial compressive strength of 2.2-2.3 MPa.

Thus, when implementing the proposed method, the formation of a granular product is achieved without the use of foreign additives, which expands the range of applications of the material as an analogue of natural gypsum stone.

Claims (1)

A method of producing granular phosphogypsum, comprising mixing the starting material with a binder and subsequent rolling of the mixture, characterized in that the binder used is phosphogypsum powder obtained in the heat treatment mode of the granulate at a temperature of 170-200 ° C, and its subsequent grinding, while the proportion of material recycling predominantly up to 0.5 total flow.