RU2223245C1 - Method of elimination of sulfate salting-out deposits on surface of ceramic bricks - Google Patents

Abstract

FIELD: manufacture of facing materials; manufacture of ceramic face bricks. SUBSTANCE: proposed method includes application of crystallizing components of saturated solutions on front surface followed by subsequent heating of clay bar to temperature of 60-80 C to depth of 0.5- 1 mm. Used as components of protective layers are saturated solutions of soda ash, boric acid, borax and mixture of boric acid and soda ash which are crystallized during drying, thus closing through pores on end surfaces. Solutions of selected components are applied on front surfaces by pouring or spraying after protruding of ceramic bar from vacuum press which is subjected to fast heating to depth of 0.5-1 mm and to temperature of 60-80 C before cutting it into air-dried bricks. Heating is effected by infra-red radiation or blowing with hot air. EFFECT: possibility of obtaining smooth and deep color. 3 tbl, 1 ex

Description

The invention relates to the production of ceramic cladding materials and can be used for the manufacture of, for example, facial ceramic bricks.

There is a method of eliminating sulfate efflorescence, which consists in neutralizing the action of soluble salts due to their volumetric binding and translation into an inactive state, for example, barium salts / Handbook for the production of building ceramics. Volume 3. Wall and roofing ceramics. Ed. Naumova M.M. and Nokhratyan K.A. Moscow: State Publishing House of Literature on Buildings, 1962, p. 64-65 /. The disadvantages of this method are the increased consumption of an expensive and scarce barium-containing component (for example, when the content of CaSO ₄ in clay is only 0.5% per 1000 pieces of brick, 29 kg of barium carbonate will be required) and the complexity of mass preparation in order to ensure uniform distribution of the introduced dry additive in volume ceramic mass.

The method for eliminating sulfate efflorescences due to the introduction of cement based on alumina clinker in an amount of 0.5-1.5 wt. % of the mass of the charge / Chulachenko N.G., Evsteev S.N. The way to eliminate sulfate efflorescence on the surface of ceramic cladding products. Patent No. 2161596, BiPM No. 1, 2001 /. In addition, the processes of hydration of minerals of alumina cement at the stage of raw molding and subsequent dehydration at the stage of firing the product are accompanied by volumetric changes that cause the risk of stresses in the forming ceramic structure and a decrease in the strength characteristics of the product.

Closest to the proposed one is a method of creating surface moisture-retaining films on the spoon and bump faces of a raw brick in order to improve the drying conditions of the semi-finished product by weakening the sensitivity to drying of the raw brick (or other ceramic product) while the sensitivity to drying of the clay itself is unchanged (M. Higerovich I., Bayer, V.E. Clay Brick Production, Moscow: Stroyizdat, 1984, 95 pp.). As components of moisture-insulating compositions, liquids characterized by low vapor elasticity (glycerin and ethylene glycol stabilized by lime solutions), and technical emulsions and emulsions of the “water in oil” type, including with suspended mineral particles (oil-lime emulsion suspension, fuel oil-water and bituminous, were used) emulsions, emulsified bottoms of synthetic fatty acids). The disadvantages of this method is its low efficiency in the direction of eliminating salt formation in facing ceramic technologies for a number of reasons: firstly, the term “moisture-retaining films” is very arbitrary, since they have a certain degree of air and moisture permeability, and secondly, they have a limited life , since these films maintain their integrity, playing the role of regulators of the drying speed, only in the initial period of drying, and over time, when the drying process is wet st products decreases, emulsion compositions disintegrate. In addition, the presence in the compositions of such compositions of a calcium-containing (calcareous) component and the use of sulfur-containing components (fuel oil and bitumen) increases the risk of lime-sulphate efflorescence on firing ceramics when fired.

The task of the invention is to eliminate vysolobrazovaniya on the front surfaces of ceramic cladding materials.

The invention consists in the directed regulation of moisture transfer from the front surfaces of a facing brick to a bed during drying and roasting of raw material by creating a moisture and vapor impermeable protective layer, which is ensured by a set of operations consisting in applying a protective solution to these surfaces with subsequent accelerated heating of the clay beam from the surface to depth of 0.5-1 mm to a temperature of 60-80 ° C.

The protective functions of the applied solution consist in the ability to crystallize during drying and to melt during firing and close through pores on the front surfaces of the semi-finished product. As crystallizing materials, saturated solutions of soda ash, boric acid, borax, and combinations thereof are used.

A decrease in the content of components in protective solutions to amounts less than necessary for saturation is insufficient to ensure the completeness of the protective effect of crystallizing components. An increase in the concentration of components more than is necessary to obtain saturated solutions leads to an overexpenditure of components, since when applying supersaturated solutions, insoluble components are not absorbed by the pores and remain on the raw surface.

Example.

A combination of two varieties of low-melting red-burning clays is used as clay raw materials for facing bricks.

The first sample in appearance is brown clay in an unbaked state, which is the main clay component of the ceramic mass, the second sample is dark gray in color and is used as an additive in up to 20% of the brick mass.

The varieties used differ in the different quantitative composition of soluble salts given in Table 1.

Drying and firing of ceramic bricks based on these clay in the factory is accompanied by the appearance of efflorescence on surfaces that worsen its decorative qualities.

The criterion for the choice of materials for protective layers, eliminating efflorescence by blocking through pores, is their ability to crystallize during drying and to melt at practically used firing temperatures.

As components for such protective layers, saturated solutions of soda ash, boric acid, borax, and also mixtures of boric acid and soda ash are used, which crystallize during drying and thereby clog through the pores on the front surfaces, blocking the exit paths of water vapor from the product volume to front surfaces and forcing them to diffuse onto the bed. In addition, when melted during firing, the components of these coatings react with sulfur compounds deposited on the surface of the semi-finished product from water vapor and flue gases, are absorbed by the glass phase and neutralize their negative effect on the surface condition of the fired material.

Prepared saturated solutions of the selected components (Table 2) are applied to the front surfaces (stick and spoon) of a ceramic beam by irrigation or spraying after the beam leaves the vacuum press, which is rapidly heated up from the vacuum press to its cutting into the raw brick with surface to a depth of 0.5-1 mm to a temperature of 60-80 ° C or infrared radiation, or a sharp blowing with hot air in order to activate the formation of crystalline hydrates from saturated solutions of the components of the protective layer. Next, the raw material is evenly dried in dryers to a moisture content of 4-6%.

Drying is fired at a temperature of 1000-1050 ° C for 24 hours with aging at a final temperature of at least 2 hours.

The front surfaces of the calcined products are distinguished by evenness of color and color saturation (Table 3).

The absence of efflorescence on the front surfaces is due to the shielding effect of the protective layers created during the molding of raw materials, which change the direction of moisture transfer during the drying of raw materials in dryers and the preparation of the semi-finished product in the heating zone in a tunnel oven (Table 3).

Claims (1)

A method for eliminating sulfate efflorescences on the surface of ceramic bricks by changing the direction of moisture and vapor transfer, including creating a protective layer on the surface of the raw brick, characterized in that saturated solution of soda ash, boric acid, borax, and combinations thereof are used as components of the applied solution the outgoing clay bar is subjected to accelerated heating from the surface to a depth of 0.5-1 mm to 60-80 ° C.