RU2396227C1 - Method of obtaining cementing autoclave hardening - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to construction materials and can be used in production of cementing materials for autoclave products. In method of obtaining cementing autoclave hardening, which includes pre-burning preparation of sludge waste of soda production, burning, introduction of quartz sand into obtained burned solid residue, their milling, said preparation is carried out by means of press-filter with compaction of the solid residue to briquette state with moisture 11.09-15.3% and grinding to grain coarseness not larger than 20 mm, burning is carried out at temperature 850-950°C, milling is carried out with additional introduction of semi-water or double-water gypsum until specific surface is 3000-5000 cm²/g, with the following component ratio, wt %: burnt solid residue of soda production wastes 25.0-65.0; quartz sand 32.50-74.25; semi-water or double-water gypsum 0.75-2.5 (in terms of anhydrate).

EFFECT: increase of strength.

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Description

The invention relates to building materials and can be used in the production of binders for autoclaved products.

Known astringent, including, wt.% (AS USSR No. 772997, С04В 11/09):

semi-aquatic gypsum 46.3-80.5 solid residue waste soda production 19.5-53.7

The disadvantage of this binder is its low strength and a high proportion in the binder of expensive and scarce gypsum.

It is also known “Binder for the production of autoclaved concrete (as USSR USSR No. 505184, С04В 15/06) including, in wt.%:

solid residue firing product distillation wastewater 30-40 ground quartz sand 60-70

A method of obtaining this binder includes the preparation of sludge waste soda production, firing the solid residue of sludge waste at a temperature of 850-950 ° C, grinding the firing product and its subsequent mixing with ground quartz sand.

The disadvantage of this binder is its low strength and instability of quality indicators, due to the fact that the sludge received for processing from the sludge pool has an unstable chemical and mineralogical composition, including the content of products that form the basis of the binder - CaO and CaCO ₃ , as well as chlorides that affect the speed and temperature of the decarbonization process during the firing of the product.

The closest in technical essence and the achieved result is a method of producing a binder, including pre-firing preparation of sludge waste soda production, firing the solid residue and grinding it with silica. At the same time, the disadvantages inherent in the previous analogue (instability of the chemical composition of the solid residue and low binder strength) are eliminated by introducing silica in the solid residue before firing in an amount that provides a stoichiometric and constant content in the charge of 25-30%, in addition, the charge is adjusted according to the required chloride content (4-8%). Firing is carried out at a temperature of 1050-1100 ° C, and the grinding of the firing product is carried out with 30-50% silica.

The binder obtained by this method has the following composition, wt.%: (A.s. of the USSR No. 816986, С04В 7/14):

solid waste soda production 50-70 quartz sand (silica) 30-50

The disadvantages of this method of obtaining a binder are:

- the complexity and complexity of the technological process of preparing raw materials for firing (extraction and transportation of sludge to the place of processing, drainage, the need to compose a charge);

- high chloride content in the mixture and in the binder, the presence of which in the specified amount activates the corrosiveness of the mixture in relation to metal equipment and binder in relation to reinforcing steel, which limits its scope;

- high firing temperature (1050-1100 ° C), since the addition of silica before firing changes the conditions of chemical transformations of the charge components, shifting the reaction front to the region of higher temperatures, which leads to an excessive consumption of thermal energy;

- reduced strength of the binder.

The technical task of the claimed invention is to achieve stability of the chemical composition of the solid residue of sludge soda waste (by the ammonia method) with less labor and energy costs, reducing the amount of chlorides and increasing the strength of the binder.

The technical result is achieved in that the pre-firing preparation of sludge soda waste is carried out using press filters, bypassing the intermediate stage of waste storage in sludge collectors. At the same time, the following are excluded from the technological process: transportation of raw materials to the place of processing, their thermal and mechanical processing (drying, grinding), there is no need to compose a charge before firing. In addition, when processing raw materials using press filters, due to the high degree of separation of solid and liquid phases, the stability of the chemical and mineralogical composition of the filtered solid residue is achieved, the chloride content is significantly reduced, since the chloride salts of calcium, sodium and ammonium, which are well soluble in water, are not concentrated in the filtered sludge, and are removed together with the filtrate. The exception from the technological process of the operation of composing the mixture and the additional addition of silica before firing can reduce the firing temperature from 1050-1100 ° C (in the prototype) to 850-950 ° C and thereby reduce labor and energy consumption.

A distinctive feature of the present invention from the prototype is also a new composition and ratio of ingredients in the binder, since in order to slow down the setting process of the binder and to ensure the conditions for the formation of crystallized low-basic calcium hydrosilicate such as tobermorite during autoclaving, increasing the durability of the autoclaved products, an additional semi-aqueous or two-water is introduced into the binder gypsum in the following ratio of components, wt.%:

solid residue waste soda production 25-65 silica sand (silica) 32.50-74.25 semi-aquatic or two-water gypsum 0.74-2.5 (in terms of anhydrite)

The use of one or the other of these modifications of gypsum does not affect the technical result, since when mixing semi-aquatic gypsum with water, it turns into two-water gypsum by reaction:

CaSO ₄ · 0.5H ₂ O + 1.5H ₂ O = CaSO ₄ · 2H ₂ O

To ensure a constant content of gypsum in the binder, the calculation of its quantity is carried out on an anhydrous substance (anhydrite).

Obtaining a binder of the proposed method is as follows.

Sludge waste from soda production goes to the press filter, which separates (squeezes) the liquid phase from the solid. In this case, the solid residue of the sludge is compacted to a briquette with a moisture content of 11.09-15.3%, which is then crushed (crushed) to a grain size of not more than 20 mm and fired at a temperature of 850-950 ° C. The firing mode is regulated by the activity of the fired product: the content of active CaO + MgO in it should be in the range of 40-55%.

The binder is obtained in a known manner: by co-grinding a mixture consisting of a calcined product, silica sand and, optionally, semi-aqueous or ^two- water gypsum to a specific surface of 3000-5000 cm ² / g.

The test results of the chemical composition of the solid residue and physico-mechanical properties of the binder are presented in tables 1, 2, 3, 4.

For comparison, Table 1 shows the chemical composition of samples of solid residues of sludge waste taken from an active sludge collector equipped with artificial drainage at various points in the upper layers at a depth of 1 to 20 cm. The data presented indicate that the solid residue prepared for firing In a known manner, it is characterized by an unstable chemical composition, high humidity from 22.0 to 66.29% and a high content of chlorine ions from 5.33 to 20.97%. It should be noted that in other sludge collectors that are not equipped with artificial drainage, the state of sludge waste is similar.

Table 2 shows the chemical composition of the samples of solid residues of sludge waste prepared on a press filter for firing. As can be seen from the table, the chemical composition of the dehydrated product varies insignificantly, the humidity (11.09-15.3%) is lower than that of the prototype 1.98-4.52 times, and the chloride content (2.33-3, 7%) decreased by 2.3-5.7 times. It should be noted that in the binder obtained by the proposed method, the activity of the calcined product is from 40 to 55%, and the amount of chloride salts, in terms of chlorine ions, is reduced to less than 1.3%. The low chloride content in the binder allows it to be used in the production of reinforced products, thereby expanding the scope.

Table 3 presents the results of the effect of the addition of gypsum on the setting time of the binder. From table 3 it follows that the setting time of the obtained binder without gypsum with high activity of the firing product is too short (start 7 min, end 10 min). The introduction of gypsum additives during grinding of the binder allows to extend the setting time (beginning from 11 to 55 minutes, the end from 15 to 72 minutes), which improves the manufacturability of the concrete mixture.

The binder compositions in the examples and the strength of the hardened stone obtained from them are given in table 4.

Preparation of a binder and mortar mixture from it is as follows.

Quartz sand and semi-aqueous or two-water gypsum (gypsum are dosed using an anhydrous substance) are introduced into a metered amount of a solid residue annealed at a temperature of 850-950 ° С, and gypsum is dosed using an anhydrous substance) and grinding is carried out in a ball mill until a binder with a specific surface of 3000- 5000 cm ² / g. The resulting binder is shut with water until plasticity corresponding to a cone fusion of 107-110 mm in diameter. All mixtures indicated in table 4 are prepared with equal plasticity. The mixture is poured into prepared molds measuring 4 × 4 × 16 cm, vibrated on a vibrating table for 30 s and loaded into an autoclave. Autoclave treatment is carried out according to the regime: 8 + 2 + 6 + 3 h (pre-autoclave exposure at room temperature, pressure rise to 0.8 MPa, exposure at this pressure, pressure reduction of saturated steam). After that, the samples are removed from the autoclave, freed from the molds and tested for their strength on the press, designed to determine the compressive strength (average load rise rate during the test 20 ± 5 kgf / cm ² per second).

From table 4 it is seen that the stone of the proposed binder has a strength of 63.92 to 72.30 MPa, which on average exceeds the strength of the stone of the prototype (42.20-63.00 MPa).

Table 3 Binder setting time The amount of additive semi-aquatic or two-water gypsum, wt.% (In terms of anhydrite) 0 0.75 0.8 1,0 1,5 2.5 Start, min 7 eleven 16 19 39 55 End, min 10 fifteen 21 28 57 72

Table 4 No. p / p Astringent Firing temperature, ° С Roasting Product Activity The specific surface of the binder, cm ² / g The composition of the binder, wt.% The limit of compressive strength, MPa Firing product Quartz sand Semi-aquatic or two-aquatic gypsum,% in terms of anhydrite one Famous 1050-1100 - - fifty fifty - 63.00 2 - - 60 40 - 57.10 3 - - 70 thirty - 42,20 one Proposed 850 40 5000 25 74.25 0.75 63.92 2 850 40 5000 40 59.00 1.00 65.40 3 850 40 5000 fifty 48.00 2.00 67.90 four 850 40 5000 65 32,50 2,50 65.90 5 900 52 4000 25 74.25 0.75 67.30 6 900 52 4000 40 59.00 1.00 64.10 7 900 52 4000 fifty 48.00 2.00 66.77 8 900 52 4000 65 32,50 2,50 69.97 9 950 55 3000 25 74.25 0.75 70.06 10 950 55 3000 40 59.00 1.00 67.83 eleven 950 55 3000 fifty 48.00 2.00 67.00 12 950 55 3000 65 32,50 2,50 72.30

The binder obtained by the proposed method can be used for the manufacture of autoclaved products, for example, heavy or cellular concrete, silicate brick and other autoclaved products, including reinforced ones.

Thus, the proposed method will expand the field of resource-saving technologies and contribute to improving the environmental situation in the region.

Information sources

1. A.S. USSR №772997, С04В 11/09.

2. A.S. USSR No. 505184, С04В 15/06.

3. A.S. USSR No. 816986 С04В 7/14.

Claims (1)

A method of producing a knitting autoclave hardening, including pre-firing preparation of soda slurry waste, firing, introducing quartz sand into the obtained fired solid residue, grinding them, characterized in that the said preparation is carried out using a press filter with compaction of the solid residue to a briquette with a moisture content of 11 , 09-15.3% and grinding to a grain size of not more than 20 mm, firing is carried out at a temperature of 850-950 ° C, and grinding is carried out with the addition of semi-aqueous or two-water gypsum to specific surface 3000-5000 cm ² / g in the following ratio of components, wt.%:
solid residue waste soda production 25.0-65.0 quartz sand 32.50-74.25 semi-aquatic or two-water gypsum (in terms of anhydrite) 0.75-2.5