RU2302394C2 - Method of production of the gypsum binding agent - Google Patents

Abstract

FIELD: construction materials industry; ceramics industry; porcelain-faience industry; other industries, methods of production of the gypsum binding agents.

SUBSTANCE: the invention is pertaining to the field of the construction materials industry and may be used for manufacture of the molds in the ceramic, porcelain-faience and other industries. The method of production of the gypsum binding agent includes of the gypsum rock, separation of the produced gypsum crushed rock into fractions, the hydrothermal treatment of the fraction of the gypsum crushed rock with the subsequent thermal treatment and the grinding, The separation of the gypsum crushed rock they make for the fraction of 0-20 mm and the fraction of 20-40 mm, then the gypsum crushed rock of the fraction of 20-40 mm is subjected within 5-6 hours to the hydrothermal treatment in the interval of the temperatures of 120-150°C and under the air pressure of 1.1-1.5 atm. After that the gypsum crushed rock of the fraction of 20-40 mm is mixed with the crude gypsum crushed rock of the fraction of 0-20 mm in the ratio accordingly (1-3 : 1)in shares of the mass. Then the produced mixture is subjected to the thermal treatment at the temperature of 120-150°C in the rotating furnace. The technical result of the invention is the increased homogeneity of the gypsum binding agent, reduction of the contents in it of the two-aquatic calcium sulfate, the increased time intervals of hardening and the reduced volumetric expansion.

EFFECT: the invention ensures the increased homogeneity of the gypsum binding agent, the reduced contents in it of the two-aquatic calcium sulfate, the increased time intervals of its hardening and the reduced volumetric expansion.

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Description

The invention relates to the construction materials industry and can be used for the manufacture of molds in ceramic, porcelain and earthenware and other industries

A known method of producing a gypsum binder, including hydrothermal treatment of gypsum stone, drying, crushing, separation of crushed stone fractions of 3-10 mm, grinding the remaining part to a specific surface of 2500-3500 m ³ / kg, mixing the resulting powder with crushed stone in a ratio of 0.6-1 , 5 and heat treatment of the mixture in a gypsum boiler at 120-140 ° С (USSR author's certificate No. 1493632, 1987, Ml. C04B 11/00, published in the bulletin "Discoveries, inventions" No. 26, 1989).

It is known that hydrothermal treatment is carried out in a damper, which, like the gypsum boiler, according to the structure of the flows of reacting substances, is a product mixing device.

Mixing apparatuses have a significant drawback - the presence of stagnant zones, breakthroughs, etc., due to which chemical reactions are incomplete, in this case dehydration. Moreover, if a small fraction of gypsum crushed stone is subjected to dehydration, then quite large stagnant zones are formed in the material layer. With an increase in the size of the fraction (grain), intergranular voidness increases, the area of stagnant zones decreases according to the structure of the flows of reacting substances, but dehydration fractions are hindered due to an increase in diffusion resistance, and water from the central part of the grain is hindered by layers from hemihydrate or dehydrated calcium sulfate.

In this regard, in the known method after hydrothermal treatment, gypsum fractions of 50-100 mm are obtained, which have a high heterogeneity - from two-water in the center of the grain to dehydrated on its surface. In the process of drying, chemical reactions do not occur, only crystallization water is removed from the surface of the stone.

The closest in technical essence and the achieved result is a method of producing gypsum binder, including crushing gypsum stone, separation of gypsum crushed stone into fractions 0-25 and 25-50 mm, hydrothermal treatment of the fraction 25-50 mm with its subsequent drying and grinding (V. Baldin P. Production of gypsum binders. M., Higher School, 1988, p.23-25).

The disadvantage of this method is the low quality of the obtained gypsum binder, the high heterogeneity of the gypsum product in the binder content of the hemihydrate and dehydrated hemihydrate of calcium sulfate when mixing the fraction due to the presence in the mixing apparatus of stagnant zones, leakage, etc., as a result of which the chemical flow does not fully occur reactions, in this case dehydration.

The heterogeneity of the finished product leads to a reduction in the setting time and an increase in the volume expansion of the gypsum binder.

The technical result, the achievement of which the creation of this invention is directed, is to improve the quality of the obtained gypsum binder by increasing its uniformity, the dehydrated hemihydrate and calcium sulfate hemihydrate contained therein, with a decrease in the content of calcium hydrogen sulfate and, consequently, an increase in setting time and a decrease in volume expansion product.

The technical result achieved is achieved by the fact that in the method of producing gypsum binder, including crushing gypsum stone, separation of the obtained gypsum crushed stone into fractions, hydrothermal treatment of the fraction of gypsum crushed stone with subsequent heat treatment and grinding, separation of gypsum crushed stone is carried out into a fraction of 0-20 mm and a fraction of 20- 40 mm, then the gypsum crushed stone of a fraction of 20-40 mm is subjected to hydrothermal treatment for 5-6 hours in the temperature range 120-150 ° C and pressures of 1.1-1.5 atm, after which the gypsum crushed stone of a fraction of 20-40 mm is mixed fractions of 0-20 mm in a ratio of (1–3): 1 parts, respectively, with raw gypsum crushed stone, heat treatment of the resulting mixture is carried out at a temperature of 120-150 ° C in a rotary kiln.

The method is as follows.

Gypsum stone with a piece size of up to 300 mm is crushed in a jaw crusher and is divided into fractions of 0-20 mm and 20-40 mm on a screen.

Crushed stone fractions of 20-40 mm are subjected to hydrothermal treatment in a damper at a temperature of 150 ° C and a pressure of 1.1 atm for 6 hours.

After hydrothermal treatment, gypsum crushed stone of a fraction of 20-40 mm is mixed with crude gypsum crushed stone of a fraction of 0-20 mm, respectively, in the ratio (1-3): 1.

Next, the obtained gypsum mixture is subjected to heat treatment in a rotary kiln in the temperature range 120-150 ° C for 40-45 minutes

Then the heat-treated gypsum mixture is crushed to a residue on sieve No. 2 of not more than 1%.

In the proposed method for the production of gypsum binder, mixing previously subjected to hydrothermal treatment of gypsum crushed stone fraction 20-40 mm before heat treatment (firing) with raw gypsum crushed stone fraction 0-20 mm contributes to the uniform movement of the layer of gypsum crushed stone at a constant speed along the entire length of the furnace, equal to the speed of gypsum crushed stone fractions of 20-40 mm. Gypsum crushed stone fraction 20-40 mm is the carrier medium for crushed stone fraction 0-20 mm, therefore, a change in the surface forces of the internal interaction between its grains does not affect the movement of the entire layer of the mixture of gypsum crushed stone in the mixing apparatus. The constant thickness of the crushed stone layer and the speed of its movement provide the same heat supply to each particle of the layer and, therefore, a more complete dehydration process is ensured. When mixing gypsum crushed stone of a fraction of 20-40 mm with raw gypsum crushed stone of a fraction of 0-20 mm in a ratio of (1-3): 1, uniform movement of a layer of crushed stone is ensured.

The constant thickness of the layer of gypsum crushed stone and the speed of its movement in the mixing apparatus, for example a damper, provide an equal, constant supply of heat to each particle of crushed stone along the thickness of the layer and, therefore, a more complete course of the dehydration process.

Table 1 shows the results of comparing the indicators of the process of obtaining a gypsum binder according to the proposed and known method adopted as a prototype.

Table 1 Indicators The proposed method Known method The ratio of crushed stone, by weight: - fractions of 20-40 mm one 1.3 1.15 0.9 2,4 one - fractions 0-20 mm one one one one one one Setting time, min: - Start 7 8 7 5 6 four - end eleven 12 eleven 9 10 8 Volume expansion,% 0.14 0.13 0.14 0.17 0.15 0.22 Water absorption of the product,% 25 28 26 22 24 fifteen

The implementation of the method allows to obtain molding gypsum on the number of dampers, one and a half times less than by the known method, to increase the setting time of the binder, as well as the setting interval, reduce volume expansion by 23-41%, increase water absorption of products by 1.5-1.9 times.

The analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information and identification of sources containing information about analogues of the claimed invention, allowed to establish that the applicant did not find an analogue characterized by features identical (identical) to all essential features of the claimed invention.

The determination from the list of analogues of the closest technical solution (prototype) made it possible to identify a set of essential distinguishing features with respect to the technical result seen in the claimed method for producing gypsum binder, set forth in the claims.

Therefore, the claimed invention meets the criterion of "novelty."

To verify the conformity of the claimed invention to the criterion of "inventive step", the applicant conducted an additional search for known solutions to identify signs that match the distinctive features of the prototype of the claimed.

The search results showed that the claimed invention does not follow explicitly from the prior art as determined by the applicant. In the present invention, the technical result is not determined by the known influence of the distinguishing features and it could not be predicted in advance, based on the information contained in the prior art.

Therefore, the claimed invention meets the criterion of "inventive step".

The criterion of "industrial applicability" is confirmed by the fact that the proposed method for the production of gypsum binder can be successfully, with great efficiency, used at enterprises of the building materials industry for the manufacture of ceramic and porcelain and faience products.

Claims (1)

A method of producing gypsum binder, including crushing gypsum stone, separating the resulting gypsum crushed stone into fractions, hydrothermally treating a fraction of gypsum crushed stone, followed by heat treatment and grinding, characterized in that the separation of gypsum crushed stone is made into a fraction of 0-20 mm and a fraction of 20-40 mm, then gypsum crushed stone of a fraction of 20-40 mm is subjected to hydrothermal treatment for 5-6 hours in the temperature range 120-150 ° C and a pressure of 1.1-1.5 atm, after which gypsum crushed stone of a fraction of 20-40 mm is mixed with raw gypsum crushed stone fractions 0-20 mm in the ratio, respectively (1-3): 1 parts by weight, then the resulting mixture is heat treated at a temperature of 120-150 ° C in a rotary kiln.