RU2090528C1 - Method of manufacturing aluminosilicate non-vitrified sand - Google Patents

Abstract

FIELD: manufacture of building materials. SUBSTANCE: invention relates to non-vitrified aluminosilicate light sands applicable as additives (instead of haydite and aggloporite sands) to molding compounds when manufacturing structural and heat-insulation concretes and also as thinning agent in manufacturing porous coarse ceramics: bricks, drainage pipes, etc. Sand of invention is manufactured by mixing coal production and coal dressing wastes with clay-containing binder to form slurry which is further partially dried and mixed with combustible-containing nontoxic wastes, namely cellulose-containing waste and sub-quality brawn coal, contents of ingredients being the following (in wt %): coal-containing waste, 45-50; silica binder, 20- 26; cellulose-containing waste, 12-18; sub-quality fine-disperse brawn coal, 12-17; water (above 100%), 20-30. Finally mixture is fired at 750-950 C, disintegrated, and sorted. EFFECT: reduced cost due to utilizing wastes and low-quality materials. 3 cl, 3 tbl

Description

 The invention relates to methods for producing unglazed aluminosilicate light sands and may find application in the building materials industry as an additive (instead of expanded clay or agloporite sand) as a part of molding materials in the manufacture of structural heat-insulating concrete, as well as as an exhaustive additive in the production of porous rough ceramics (bricks, drainage pipes, etc.).

The traditional method of producing ceramic crushed stone and sand based on it by mixing a clay binder with crushed waste from coal mining or coal preparation, sawdust and coal, molding from a mixture of raw brick, drying or without it, firing at a temperature of 980-1050 ^o C, grinding is widely known brick rejection and sieving into fractions to obtain aluminosilicate crushed stone and sand, returning a larger fraction than crushed stone for re-grinding, and a fine fraction (less than 5 mm) to the initial calcining mixture, and the next in relation to all components, wt.

Loam 75-80
Coal Waste 15-17
Fireclay (brick fight) 5-8
Sawdust 5-7 in excess of 100%
The resulting brick scrap after grinding can be used not only as a thinning additive of chamotte sand in the composition of the brick, but also as a replacement for crushed agloparite or expanded clay sands in structural heat-insulating concrete with lightweight aggregates (see Industry building materials. Ser. 4. Industry of ceramic wall materials and porous aggregates. Express information. Russian experience, 1989, issue 3, article "Efficiency of the use of coal preparation waste in the production of ceramic bricks on Voro ilogradskom plant of building materials ", p. 9). Confirmation that crushed sand (chamotte) obtained from scrap brick, including the indicated analogue method, can be used as crushed stone and sand in concrete as shown in the source (Itskovich S.M. et al. Concrete aggregate technology: Textbook for construction universities / S.M. Itskevich, L.D. Chumakov, Yu.M. Bazhenov, M. Higher school, 1991, p. 230). Obtained in a known manner aluminosilicate non-vitrified aggregate, including non-vitrified sand, along with its advantage (waste from coal preparation, coal mining and many other waste specified in the mixture are utilized, there is a more economical method in comparison with the production of vitrified sand such as expanded clay or agloparite) :
1. The energy-intensive manufacturing process associated with the need not only for coarse and medium grinding of raw materials before firing, but also the need for molding raw bricks;
2. High bulk density of sand (1000-1100 kg / m ³ ), which limits its use in structural heat-insulating concrete, for example expanded clay concrete with a density of not more than 1100 kg / m ³ and rough ceramics with a density of not more than 1850 kg / m ³ ;
3. The coefficient of structural quality of concrete and ceramic products, the composition of which is introduced sand obtained in a known manner, does not increase.

The closest technical solution to the proposed method is given in ed. N 1158532, cl. C 04 B 14/10, publ. 05/30/85, B.I. N 20, which consists in a joint intermediate heat treatment at a temperature of 700-1000 ^o C of unburned waste from coal mining or coal preparation with liquid combustible waste products, followed by cooling of the product of firing, grinding, and the ratio by weight of coal waste and combustible waste production caprolactam PASCH-1 (plasticizer adipic alkaline) take respectively 90-92 and 8-10 wt. followed by mixing the crushed calcined powder with fusible clay, molding granules and final firing at a temperature of 1230-1250 ^o C. Along with the advantage of the method, there are significant disadvantages:
1. Heat-consuming process for producing aggregate and crushed sand based on it, associated with two-stage firing, i.e. intermediate at a temperature of 700-1000 ^o C and final at a temperature of 1230-1250 ^o C.

2. High bulk density of aluminosilicate sand after the initial stage of firing (more than 950 kg / m ³ ), which limits its use in structural heat-insulating concrete with a density of not higher than 1100 kg / m ³ and ceramic brick with a density of not higher than 1850 kg / m ³ .

3. The sand obtained after the initial heat treatment at a temperature of 700-1000 ^o C, does not increase the coefficient of structural quality of structural heat-insulating concrete and porous ceramics (brick, etc.).

The objective of the invention is to reduce the bulk density of sand, to increase the coefficient of structural quality of structural heat-insulating concrete and rough ceramics with a density of not higher than 1800 kg / m ³ , into which this sand is introduced, to reduce the energy consumption of the technological process. In addition, the solution of environmental problems associated with the disposal of industrial waste.

To achieve this goal in the known method for producing aluminosilicate unglassified light sand, which consists in mixing waste coal or coal preparation with clay-containing binder and fuel-containing waste, heat treatment of the mixture, grinding and sieving it into fractions, the coal waste or coal-containing coal-type waste are mixed prior to mixing with clay-rich coal and sludge production, drying and subsequent mixing with combustible non-toxic waste, which are use cellulose-containing production waste and substandard finely divided brown coal, after which firing is carried out at a temperature of 750-950 ^o C the resulting mixture in the following ratio of components, wt.

Coal mining or enrichment waste 46-50
Clay-containing osprey-type ligament 20-26
Cellulose waste 12-18
Substandard fine brown coal 12-17
Water in excess of 100% dry mix 20-30%
As an osprey, waste from chemical treatment of waste water from cardboard production is used.

 As cellulose-containing waste, wood-plant-type waste is used, including paper-containing municipal waste.

 To conduct the experiment of the proposed method adopted components with the following characteristics.

Characterization of the components of the heat-treated mixture
1. Waste from coal mining and coal preparation.

Accepted non-burnt associated waste from coal mining of the Moscow Region basin and coal preparation at the Kimovsky coal mine in the Tula region. In the table. 1 shows the chemical composition of coal waste and coal preparation. The bulk density of the waste sifted through a sieve with a mesh diameter of 10 mm, 1000-1200 kg / m ³ , humidity 15-17 wt.

 2. Clay-containing binder: osprey waste chemical treatment of waste water from cardboard production (Aleksinsky factory, Tula region). Humidity - 70-80% The material composition of dry osprey, wt.

Cellulose Fiber 50-55
Kaolini 46.7-47.9
Organic impurities (rosin, organic acids) Else.

The chemical composition of the combustion ash of dry osprey, wt. SiO ₂ 26-30; Al ₂ O ₃ 17-20; CaO 0.15-0.18; MgO 0.1-0.12; Na ₂ O + K ₂ O 0.5-0.8; Fe ₂ O ₃ 0.1-0.3; TiO ₂ - 0.05-0.1; p.p.p. the rest. Bulk density 820-850 kg / m ³ . The color of the ash is light pink.

3. Cellulose-containing waste of wood-plant type: sawdust, wood chips, branches, reeds, reeds, crushed, stalks of corn, sunflower, tow from buckwheat, straw, and others, including paper-containing city waste. In the composition of urban waste, in addition to paper, the presence of glass is allowed 5-10% textiles, polymer waste, etc. up to 25% After burning the specified waste and calcining at a temperature of 750-950 ^o C, finely dispersed ash remains, containing an increased amount of alkali-containing potash component (K ₂ CO ₃ ). The yield of ash is 5-10%. The bulk density of ash depends on the combustible composition and is 500-800 kg / m ³ .

 4. Substandard brown coal near Moscow basin. Defective coal with a particle size of less than 10 mm has been adopted. Coal ash 40% Combustible component 60% The chemical composition of the ash meets the requirements of GOST 25818-83.

Example. 5.4 kg of unburned coal waste with a moisture content of 20% (or 4.5 kg by dry weight, i.e. 45%) were weighed through a sieve with a hole diameter of 10 mm and mixed with liquid (humidity 80%), taken in an amount of 10 kg (or 2 kg by dry weight, i.e. 20%). The resulting slurry with a moisture content of 57.8% in an amount of 15.4 kg was dried to a moisture content of 20% and a weight of 9.579 kg, and then mixed with chopped waste of plant type (stalks of corn, sunflower, straw, tow from buckwheat, leaves, chopped reed, etc. .), taken in equal amounts and with a total mass of 2.7 kg and a moisture content of 15% (or 1.8 kg by dry weight, i.e. 18%), were also mixed additionally with substandard fine brown coal with a moisture content of 20% in an amount 2.4 kg (or 1.7 kg by dry weight, i.e. 17%). The resulting mixture in an amount of 14.319 kg with a total humidity of 21.7% was heat treated for 30 minutes in a muffle laboratory furnace at a temperature of 850 ^o C. The resulting product (loose in structure) in an amount of 7.56 kg (the yield of the calcined product was 52.8% and the total loss during roasting 47.2 mass.) crushed and sieved through a set of standard sieves for sand. The resulting aluminosilicate sand had a particle size modulus 261, bulk density 575 kg / m ³ (grade 600). Using light aluminosilicate sand obtained by the proposed method, prepared claydite-concrete mixture of the following composition, wt.

Portland cement M400 19.8
Silica-alumina sand with fineness modulus 2.1 33
Expanded clay gravel with a bulk density of 500 kg / m ³ 47.2
Water in excess of 100% mixture 30.

Expanded concrete mixture was molded on a vibrating platform expanded clay concrete samples measuring 15x15x15 cm, which hardened under normal conditions (t = 20 ± 2 ^o C and relative humidity 95%) for 28 days. Then the samples were tested for compressive strength, average density, the coefficient of structural quality was determined. The test results of the samples of expanded clay concrete are given in table. 2 (mixture 2).

 In a similar way shown in the example, aluminosilicate sand and claydite concrete samples were prepared with its use, and carbon-containing waste was mixed with osprey and various types of cellulose-containing waste, are given in table. 2 (mixtures 3, 4, 5, 6 including the transcendental 1 and 7).

The dusty sand obtained by screening a fraction of less than 0.14 mm is not recommended to be reintroduced into the composition of the calcined mixture for two reasons:
1. The dust fraction of sand fraction (less than 0.14 mm) contains 80-90% of wood ash and 10-20% of coal ash, i.e. the composition differs sharply from the porous composition of aluminosilicate sand with a size of 0.14-5 mm, in which, on the contrary, the aluminosilicate composition containing wood ash is not more than 15-20%
2. In the case of repeated firing of pulverized sand in the composition of the calcined mixture of the reduced composition, the pulverized sand (due to lightness and micro particle sizes) will fly away with the flue gases into the cyclones, and after repeated returns and firing, the claimed method and composition of the mixture for firing will be violated and the goal no technical solution will be reached.

 The composition, yield and corresponding properties of aluminosilicate sand and expanded clay obtained by a known prototype method (8) and proposed (2, 3, 4, 5, 6), examples with compositions 1 and 7 are beyond the limit, are given in table. 2.

The analysis of the test results of aluminosilicate sand introduced into the expanded clay concrete composition shows:
1. The proposed method reaches the goal for compounds 2, 3, 4, 5, 6, and compounds 1 and 7 are transcendent and not economically feasible, because there is a tendency to an increase in average density with a lower share of utilization (less than 45%) of coal waste (composition 1) and a decrease in the coefficient of structural quality (composition 7), in addition, the proportion of cellulose-containing, and hence alkaline-containing waste (less than 12%) is reduced.

2. The total bulk density of sand obtained by the proposed method is reduced by 300-325 kg / m ³ (by 33.3-36.1%) in comparison with sand obtained after the initial heat treatment according to the prototype method.

3. The coefficient of structural quality (R _cr / p _n ) expanded clay with sand of the proposed method is increased by 30-40%
When comparing the properties of bricks (see table. 3) obtained with aluminosilicate sand (instead of the chamotte of the analogue and prototype methods), it was revealed:
1. The decrease in average density by 130-240 kg / m ³ (6.5-12.1%).

2. The increase in the coefficient of structural quality by 10.6-11.29%
The positive effect of aluminosilicate sand instead of chamotte or crushed sand, respectively obtained by the method of analogue or prototype, is explained by two factors:
low bulk density of aluminosilicate sand (less than 600 kg / m ³ );
the content of wood ash in the sand and, consequently, flux (K ₂ CO ₃ potash), i.e. sand plays the role of not only a thinner additive, but also flux.

The technical solution to achieve the goal is explained by the following physicochemical factors:
1. Porization of rock particles (empty) rocks due to the burning out of the organic component in their composition, as well as dehydration of clay particles contained as a basis in coal mining and coal preparation waste, as well as in the solid component of osprey.

 2. By mixing porous aluminosilicate particles of sand with lighter particles of ash, ash generated from the combustion of coal and cellulose-containing industrial wastes.

 Due to the processes described in clauses 1, 2, the average density of sand grains from 0.14-5 mm in size decreases and, accordingly, their bulk density.

 3. The degree of hydration of the minerals of clinker cement (alite, belita) increases, which contributes to an increase in strength and, accordingly, the coefficient of structural quality of expanded clay concrete. The essence of the chemistry of action is as follows.

The resulting sand also contains ash from the combustion of cellulose-containing waste and osprey. Such ash is known to be enriched with potassium ions, potash. Potash is a water-soluble salt that forms an alkaline environment during hydrolysis
K ₂ CO ₃ + 2H ₂ O 2KOH + H ₂ CO ₃ (1)
Received 2KOH dissociates in the mixing water of expanded clay according to the scheme:
2KOH _ → 2K ⁺ + 2OH ^- (2)
The resulting hydroxylions (2OH ^- ) are more active as is well known than water molecules, and therefore they enter the hydration reaction with clinker minerals faster than water molecules, and due to their greater mobility they penetrate more deeply into the mass of cement clinker particles. This process helps to increase the strength and, accordingly, the coefficient of structural quality of expanded clay concrete. The carbonic acid remaining in reaction (1) also contributes to the strength of concrete, since the formed Ca (OH) ₂ molecules during hydration of the alite mineral (C ₂ S) reacts with H ₂ CO ₃ , forming a more durable and hardly soluble component of CaCO ₃ in water, which plugs the pores of concrete.

 Thus, the simultaneous positive effect of sand obtained by the proposed method on reducing the average density of expanded clay and ceramic bricks and increasing the strength of expanded clay leads to an increase in the coefficient of their structural quality.

The proposed method for producing light aluminosilicate sand for expanded clay concrete and ceramics has the following technical and economic advantages in comparison with sand obtained in a known manner:
1. The fuel consumption for heat treatment is reduced by 35-37% due to the utilization (burning) of osprey and cellulose-containing industrial wastes. The role of the latter can also be played by half-rotten wooden racks, which, together with coal waste, are thrown into dumps of heaps from lava mines.

2. The consumption of sand (in volume fractions) is reduced by 1 m ^{3 of} expanded clay concrete due to a decrease in its average density.

 3. A comprehensive utilization of 3 types of industrial waste is carried out, which expands the resources of the raw materials for the production of expanded clay concrete and rough ceramics; environmental issues are being addressed.

 4. The cost of the resulting small aggregate is reduced by 25-30%

Claims (3)

 1. The method of producing aluminosilicate unglassified sand by mixing waste coal or enrichment with combustible waste, followed by firing, grinding and sieving in fractions, characterized in that before mixing the waste of coal mining or coal enrichment with combustible waste, the waste is mixed with coal-containing coal or coal before receiving the sludge, drying it and subsequent mixing with combustible waste, which are used as dissolved toxic waste from the group consisting of cellulose waste, and inferior particulate lignite, wherein the resulting mixture has the following component ratio, wt. Coal waste from coal mining or coal preparation 45 50
Clay-containing osprey bond 20 26
Cellulose waste 12 18
Substandard finely divided lignite 12 17
Water in excess of 100% 20 30
and firing the mixture is carried out at a temperature of 750 950 ^o C.  2. The method according to p. 1, characterized in that as a clay-containing binder of the osprey type, waste from chemical wastewater treatment of cardboard production is used.  3. The method according to claim 1, characterized in that as a cellulose-containing waste, wood-waste type waste is used, including paper-containing city waste.

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