RU2836941C1 - Method of producing porous granular construction material - Google Patents

Abstract

FIELD: construction materials.

SUBSTANCE: invention relates to production of construction materials which can be used as light aggregate in production of dry construction mixtures, mortars and concrete. Disclosed method involves crushing silica raw material, mainly tripoli, to fraction of 0.5-10 mm; grinding this fraction to achieve a powdery state; preparation of a mixture by loading a powdered fraction into a mixer, moistening it with hot water, introducing an alkali into the mixer together with a pore-forming, reinforcing and water-retaining additive; mixing the obtained mixture, accompanied by self-heating, until a hot viscous mixture is obtained; step-by-step processing of the ready mixture with the possibility of obtaining a milled semi-finished product as a result; drying the semi-finished product and its further grinding to obtain a granulated fraction; loading the granulated fraction into a porous-forming furnace to obtain porous granules of the finished product; the latter are cooled in a cooler-classifier and distributed in a hopper-accumulator by fractions of granules of various sizes. Prior to grinding, crushed fraction of tripoli 5-10 mm is pre-dried to residual moisture content within 3-5%. Step-by-step processing of the ready viscous mixture is carried out by unloading the mixture into a proportioner-extruder with subsequent moulding of briquettes with size of 150×150 mm, rolling of briquettes on rolls on "pancakes" with thickness of 10-15 mm, followed by cooling on conveyor, grinding "pancakes" on belt-shredder to pellets with size of 10×10 mm. Pellets are dried to residual moisture content of 15-20% with subsequent crushing to granulated fraction of 0.25-1.5 mm. Powder fraction is milled within 80-100 mcm, finished product granules are fired and expanded in porous-forming furnace within 550-650 °C.

EFFECT: obtaining ceramic foam granules of a construction material with a closed cellular structure, having superior physical and mechanical characteristics to the prototype.

1 cl, 1 dwg, 1 tbl, 2 ex

Description

The invention relates to the field of production of building materials, namely, to methods for producing porous granulated building materials that can be used as a lightweight porous filler in the production of dry building mixtures, solutions and concrete. This invention can also be used in the production of structural and thermal insulation and thermal insulation building materials (wall blocks, panels, slabs, etc.), polymeric materials, decorative products, including the use of 3D printing, as well as as a thermal insulation backfill.

A method for producing a solid hydrosilicate gel is known from the prior art (RU 2448902 C1, published 27.04.2012), which includes grinding a porous siliceous raw material containing at least 70 wt. % amorphous SiO ₂ to obtain siliceous sand, dosing this sand and air-dry granulated caustic alkali, loading them into a reactor equipped with a stirrer and mixing, accompanied by self-heating, until a hot viscous semi-finished product is obtained, unloading the latter into containers and holding in the containers with gradual natural cooling to a temperature close to the ambient temperature until a mature solid silicate gel is obtained.

The disadvantage of the known method is the lack of continuity of the technological process. During the preparation of the mixture, the main difficulty is in visual control of the optimal viscosity of the mixture. If the viscosity exceeds the optimal value, difficulties arise both with cleaning the mixer from the part of the mixture stuck to it, and with unloading the mixture as a whole. Therefore, the mixture that has not reached the optimal viscosity is manually unloaded into containers, which is quite labor-intensive, and is kept until it hardens at ambient temperature. In this case, the hardening process is characterized by duration, and the readiness of the product is determined only visually. The porous material obtained by this method dissolves in water, and also does not have sufficient compressive strength, which causes it to crush during mixing.

A method for producing porous granulated building material is also known (BY 20524, C1, published 10/30/2016). The technological process of the known method for producing porous granulated building material is as follows.

The initial siliceous raw material - tripoli, with a _SiO2 content of at least 70% and a moisture content of 5-30%, is initially crushed to a fraction of no more than 0.5 mm, and then ground in a DM-2 disintegrator, obtaining a crushed fraction of up to 500 microns.

The crushed fraction enters a planetary mixer through a dosing hopper, equipped with a heater and temperature and engine load control sensors with the ability to control the viscosity of the mixture during mixing. At the same time, when the humidity of the crushed fraction is 5-10%, it is necessary to add water, at the beginning of the process with a temperature of about 20 ° C, and then, to optimize the speed of the process, the water temperature is increased to 60-90 ° C.

Next, caustic alkali (NaOH) is loaded into the working mixer, pore-forming and strengthening additives are introduced, and during the process of self-heating of the mixture, a water-retaining additive is introduced. In this case, each of the additives is introduced in an amount of 1-7% of the mass of siliceous raw materials, calculated on a dry matter basis.

The following additives are used as water-retaining additives: boric acid, glycerin, sodium aluminate, tetraammine zinc hydroxide, ammonium orthoborate, which allows to reduce water absorption of the obtained porous material. The following additives are used as strengthening additives: alkali metal chloride, aqueous sodium silicate solution, silicic acid gel, sodium bicarbonate, fluorosilicate acid, which allows to achieve increased strength of the porous material and prevent its destruction during mixing. In particular, gas-forming additives are used as pore-forming additives: aluminum powder, carbon black, glycerin, silicon carbide, glycol, which provides increased porosity of the obtained material and, accordingly, low density and low thermal conductivity.

During the mixing process, the viscosity of the mixture gradually increases, which causes an increase in the load on the mixer motor. When the motor reaches certain load values, the thermal relay is triggered, which is an indicator of the optimal viscosity of the mixture.

The finished mixture is unloaded into a press-extruder or roller crusher. The semi-finished product obtained as a result of the mixture passing through the extruder or rollers is cooled and fed into the crusher. The size of the product coming out of the crusher depends on its subsequent purpose. A disintegrator is mainly used as a crusher. The disintegrator produces fractions of 1-3 mm depending on the purpose of the final product.

After grinding, the product is fed to a dryer to remove physical water and reduce humidity to 5%. If the product humidity is higher than the specified limit, the final product will have a torn shell. Then the product from the dryer is fed to a porous oven, which operates on the principle of a fluidized bed. In the oven, granules are porous at an operating temperature of 340-540°C.

Next, the porous granules are fed from the porous oven to a refrigerator-classifier, which cools the product to 60°C and distributes it into fractions: 0.5-1 mm, 1-2 mm, 2-3 mm. Then, the specified fractions are fed into bunkers or other containers and used for their intended purpose.

The above-described known method for producing a porous granulated building material can be taken as a prototype of the claimed invention based on the maximum number of essential features identical to it.

The disadvantages of the production method described in the prototype are as follows:

1. The rock (tripoli) after crushing to a fraction of 0.5 mm (500 µm) enters the mixer with natural moisture (from 5 to 30%), which complicates the precise dosing of added water and regulation of the viscosity of the prepared batch.

2. With a particle size of rock after grinding of 0.5 mm (500 µm) during the preparation of the batch with NaOH, the reactions of formation of silicate hydrogel proceed more slowly and incompletely than with a finer fraction of tripoli, which affects the quality of the final product (porous granules), which has less strength and greater water absorption.

3. The firing temperature in the porous furnace is in the range of 340-540°C, which is insufficient for sintering (obtaining) light porous granules with reduced water absorption and increased strength.

The problem that the claimed invention is aimed at solving is to obtain a porous granulated building material with improved physical and mechanical characteristics compared to the prototype: low water absorption, high strength of granules, low thermal conductivity by changing (adding) a number of technological operations.

The technical result is the production of porous (foamed) foam ceramic granules with a closed cellular structure, significantly superior in physical and mechanical characteristics to the prototype (see table).

It follows from the table that, in comparison with the prototype, the water absorption of the granules is 3.5-5 times lower, the strength of the granules is more than 2 times higher, and the thermal conductivity of the granules is 30-40% lower.

The stated task can be implemented, and its technical result can be achieved by means of the declared method, which includes the following technological operations:

- crushing of siliceous raw materials, - tripoli (is a suitable raw material, - a fine-pored opal sedimentary rock) containing at least 80 wt.% amorphous SiO ₂ , until a crushed fraction of 0.5-10 mm is obtained (which will facilitate its better drying);

- grinding this fraction in a disintegrator until it reaches a powdery state (which will subsequently contribute to the complete homogenization of the batch: tripoli + water + NaOH + technological additives, in a mixer);

- preparation of the batch by dosing and loading the powder fraction into the mixer, moistening with hot water to bring the humidity to 45-50%, introducing air-dry granulated alkali NaOH into the mixer, introducing pore-forming, strengthening and water-retaining additives during the preparation of the mixture (which will ensure the production of a porous finished product with improved qualities);

- mixing of the prepared moistened batch, accompanied by self-heating, until a hot viscous mixture is obtained (ready for further processing);

- step-by-step processing of this mixture with the possibility of obtaining a crushed semi-finished product as a result (the step-by-step process increases the duration of the preparation time of the semi-finished product);

- drying of the semi-finished product and its further grinding to obtain a granulated fraction (the physical and mechanical properties of which indicate the complete readiness of the semi-finished product for heat treatment);

- loading this granulated fraction into a porous furnace to obtain porous granules of the finished product;

- cooling it in a refrigerator-classifier and distributing it in a granule storage bin by fractions;

in this case:

- before crushing the crushed fraction of tripoli 5-10 mm in the disintegrator, it is pre-dried to a residual moisture content of 3-5% (which will further optimize the dosing of water introduced into the prepared batch), and the step-by-step processing of the hot viscous mixture with the possibility of obtaining a crushed semi-finished product is carried out in three stages:

the mixture is unloaded into a dosing extruder, followed by forming it into 150x150 mm briquettes, the briquettes are rolled on rollers into 10-15 mm thick "pancakes" with subsequent cooling on a conveyor to a temperature close to the ambient temperature, and the "pancakes" are crushed on a grinding belt into 10x10 mm pellets (a longer period of preparation of the semi-finished product pellets contributes to a more complete chemical reaction of sodium disilicate formation, which affects the improvement of the quality of the semi-finished product);

- drying of semi-finished product pellets is carried out in a drying drum to a residual moisture content of 15-20% (low water absorption will ensure better swelling of the granules in the aerating furnace), followed by crushing of the dried pellets in a crusher to a granulated fraction of 0.25-1.5 mm (this size range of the fraction of granules prepared for the process of swelling and firing in the aerating furnace is optimal for obtaining three types of fractions of the finished product - 0.5-1.0 mm, 1.0-2.0 mm, 2.0-3.0 mm);

- the grinding of the powder fraction in the disintegrator is carried out within the range of 80-100 µm (which will ensure a more complete course of the physicochemical reaction of the interaction of SiO ₂ with NaOH in the mixed batch);

- firing and porization of the granules of the finished product in the porization furnace is carried out at a temperature of 550-650° C. (a higher temperature in the furnace will ensure optimal silicate formation with the production of a closed cellular structure of foamed granules, which in turn will ensure improved physical and mechanical characteristics of the granules of the resulting product: low water absorption, high strength, low thermal conductivity);

- alkali, pore-forming, strengthening and water-retaining additives are introduced each in an amount of 0.5-17% of the mass of silica raw materials, calculated on a dry matter basis (which will more optimally balance the quantitative composition of the introduced ingredients and the original raw materials and ensure the required conditions for the chemical reaction between them during the preparation of the batch);

- whereby alkali, pore-forming and strengthening additives are introduced into the working mixer, and a water-retaining additive is introduced during the self-heating process

The claimed invention is explained by a block diagram of a method (technology) for producing a porous granulated building material (Fig. 1).

The claimed method is carried out as follows.

The original siliceous raw material is tripoli, a finely porous opal sedimentary rock containing at least 80 wt.% amorphous SiO ₂ .

The initial crushing of tripoli to a fraction of 0.5-10 mm is carried out in a crusher. The operation of preliminary crushing of raw materials contributes to its better drying.

The crushed fraction of 0.5-10 mm is subjected to preliminary drying in a drying drum to a residual moisture content of 3-5%, which is one of the features of the declared technology, since such a procedure allows for further optimization of the dosing of water introduced into the prepared batch, which in turn will ensure control of the viscosity of the batch.

The crushed tripoli dried to a moisture content of 3-5% is ground in a disintegrator to a powder state, forming a fraction of 80-100 μm. Such fine grinding of tripoli (100 μm), in contrast to the prototype (500 μm), which is another feature of the declared technology, will further facilitate the complete homogenization of the batch (tripoli + water + NaOH + technological additives) in the mixer and will ensure the complete flow of physicochemical reactions of the interaction of SiO ₂ with NaOH.

SiO ₂ +2NaOH+(n-1)H ₂ O → Na ₂ O2SiO ₂ nH ₂ O

Next, the batch is prepared. To do this, the powder fraction of 80-100 μm is dosed and loaded into the mixer, hot water with a temperature of 85-90°C is supplied, bringing the humidity of the powder fraction of tripoli to 45-50%. The resulting mixture (tripoli + water) is pre-mixed, and then a measured amount of granulated NaOH is supplied through the loading hatch of the mixer, and a pore-forming, strengthening and water-retaining additive is introduced, continuing the mixing. In this case, each of the additives is introduced in an amount of 0.5-17% of the mass of siliceous raw materials in terms of dry matter.

The pore-forming additive can be selected from the group comprising: aluminum powder, glycerin, glycol, carbon black, a strengthening additive from the group comprising: sodium hydrogen carbonate, alkali metal chloride, an aqueous solution of sodium silicate, silicic acid gel, sodium bicarbonate and hydrofluorosilicate acid.

During the process of preparing the batch, it self-heats to 72-74°C. During the process of self-heating of the mixture, a water-retaining additive selected from the group including: boric acid, glycerin, sodium aluminate, tetraammine zinc hydroxide and ammonium orthoborate can be introduced.

The batch is prepared in a planetary mixer equipped with a heater until the required viscosity is achieved.

During the mixing process, the viscosity of the mixture gradually increases, which leads to an increase in the load on the mixer motor. The viscosity of the batch during the mixing process is controlled based on the readings of the motor load control sensor.

When the required viscosity of the mixture is reached, the engine is subjected to maximum load, and the thermal relay is triggered, which is an indicator of the optimal viscosity of the mixture, i.e. the mixture is ready for further processing. This processing is carried out in stages, with the possibility of obtaining a crushed semi-finished product as a result. The crushed semi-finished product is obtained in three stages. The mixture with optimal viscosity is unloaded into a dispenser-extruder, our own design, in which 150x150 mm briquettes are formed from the mixture mixed in the mixer. Then the briquettes go to the rollers, where they are rolled into "pancakes" of a certain thickness of 10-15 mm, which are fed to the conveyor, where they cool to a temperature close to the ambient temperature. Then on the chopper belt the "pancakes" are crushed into pellets of 10x10 mm in size, which will be the crushed semi-finished product.

It should be especially noted that such a step-by-step grinding of the batch: briquettes → “pancakes” → pellets increases the duration of the preparation time of the semi-finished product and promotes a more complete reaction of the formation of sodium disilicate (Na ₂ O ₂ SiO ₂ nH ₂ O), which is also a technological feature of the claimed method.

After passing through the crusher belt, the semi-finished product pellets enter the drying drum, where they are dried to a residual moisture content of 15-20%, which is slightly higher than the moisture content of the product after drying in the prototype, but this will contribute to better swelling of the granules in the porosity oven.

Next, the dried pellets are fed into a crusher, where they are further crushed into granules with a fraction of 0.25-1.5 mm.

Next, the granulated fraction from the crusher enters the porizer furnace, where porization (swelling) and sintering of the granules occurs in the temperature range of 550-650°C. Increasing the heating temperature of the granulated material to 550-650°C, in contrast to the sintering temperature of 340-540°C in the prototype, is another feature of the declared technology.

A higher temperature range ensures the optimal course of silicate formation processes, which are the processes of sodium disilicate formation due to the dehydration of sodium disilicate crystal hydrates formed from colloidal sodium hydrosilicates during heating. At the glass formation stage, during foaming of the granulated material, due to the melting of the eutectic, a primary melt is formed and, then, amorphous silica (SiO ₂ ) and additives dissolve in the primary melt, which causes the formation of a sodium silicate melt, which hardens in the form of a glass phase upon cooling, which in turn helps to obtain strong and water-resistant porous granules of the finished product.

From the porous oven, the porous and fired granules of the finished product are fed into a refrigerator-classifier, where they are cooled to a temperature of 60°C and classified into three fractions: 0.5-1.0 mm, 1.0-2.0 mm, 2.0-3.0 mm, with further distribution into storage bins.

Example 1.

Tripoli was used as a silica-containing raw material, the _SiO2 content of which was 80%, and the humidity was 30%. The rock was pre-crushed to a fraction of 0.5 mm, then the crushed fraction of tripoli was dried to a residual humidity of 3%.

The 0.5 mm fraction tripoli was ground to a powder fraction of 80 µm using a disintegrator.

The powder fraction was poured into the dosing hopper and then fed into the operating mixer, the humidity of the tripoli was brought to 45% by moistening with hot water. At the beginning of the process, the temperature of the tripoli was 20 ° C. A planetary mixer equipped with a heater, temperature sensors, and a thermal relay was used for the process. Then granulated NaOH was fed into the mixer through the loading hatch. During the process of mixing the tripoli and dry caustic soda, self-heating of the mixture was carried out. Mixing of the batch was carried out to a certain viscosity, until the thermal relay was triggered. Then the mixture was unloaded into the dosing extruder, briquettes measuring 150 × 150 mm were obtained. Then, the briquettes were rolled on rollers into "pancakes" 10-15 mm thick. The “pancakes” were cooled to a temperature close to the ambient temperature on a conveyor and then the cooled “pancakes” were fed to a grinding belt, where they were ground into pellets measuring 10×10 mm.

The resulting crushed semi-finished product (in the form of pellets) was dried in a drying drum to a residual moisture content of 15%, after which they were further crushed in a crusher to a granulated fraction of 0.25 mm.

The granules were fed into a porizer furnace, where the granules were fired and porized at a temperature of 550°C. The device operates on the fluidized bed principle. After that, the resulting finished product was fed into a classifier refrigerator to separate it into three fractions. The classifier refrigerator performs two functions: cooling and classification. In the classifier refrigerator, the product was cooled to 60°C. As a result, the finished product was obtained, divided into three fractions: from 0.5 to 1 mm, from 1 to 2 mm, from 2 to 3 mm.

The specified fractions were used in the production of thermal insulation decorative dry plaster mixes for facades.

Example 2.

Tripoli was used as a silica-containing raw material, the SiO content of which was 80%, and the humidity was 30%. The rock was pre-crushed to a fraction of 10.0 mm, then the tripoli was dried to a residual humidity of 5%.

The 10.0 mm fraction tripoli was ground to a powder fraction of 100 µm using a disintegrator.

The powder fraction was poured into the dosing hopper and then fed into the operating mixer, the humidity of the tripoli was brought to 50% by moistening with hot water. At the beginning of the process, the temperature of the tripoli was 20 ° C. A planetary mixer equipped with a heater, temperature sensors, and a thermal relay was used for the process. Then granulated NaOH was fed into the mixer through the loading hatch. During the process of mixing the tripoli and dry caustic soda, self-heating of the mixture was carried out. Mixing of the batch was carried out to a certain viscosity, until the thermal relay was triggered. Then the mixture was unloaded into the dosing extruder, briquettes measuring 150 × 150 mm were obtained. Then, the briquettes were rolled on rollers into "pancakes" 10-15 mm thick. The “pancakes” were cooled to a temperature close to the ambient temperature on a conveyor and then the cooled “pancakes” were fed to a grinding belt, where they were ground into pellets measuring 10×10 mm.

The resulting crushed semi-finished product (in the form of pellets) was dried in a drying drum to a residual moisture content of 20%, after which they were further crushed in a crusher to a granulated fraction of 1.5 mm.

The granules were fed into a porizer furnace, where the granules were fired and porized at a temperature of 650°C. The device operates on the fluidized bed principle. After that, the resulting finished product was fed into a classifier refrigerator to separate the product into three fractions. The classifier refrigerator performs two functions: cooling and classification. In the classifier refrigerator, the product was cooled to 60°C. As a result, a product was obtained divided into three fractions: from 0.5 to 1 mm, from 1 to 2 mm, from 2 to 3 mm.

The specified fractions were used in the production of thermal insulation decorative dry plaster mixes for facades.

The finished product obtained by the claimed method is a light porous filler used mainly in the production of thermal insulation decorative dry plaster mixes for facades of buildings and structures. Due to its porosity, low weight, stable state in any climatic conditions, it is ideal for leveling walls and finishing facades of both load-bearing and facing structures of all bases (types of surfaces) - from large reinforced concrete panels, bricks, foam gas silicate blocks.

The closed-cell structure of such a building mixture is capable of reliably retaining the heat of a living space, and has also proven itself well in the insulation of loggias and balconies.

At the same time, there is no need for additional insulation, which means that the costs of purchasing materials are significantly reduced, since this technology makes it possible to do without primers and meshes, reducing the amount of work and time spent.

Claims (4)

A method for producing a porous granulated building material comprising crushing a siliceous raw material, tripoli, containing at least 80 wt. % amorphous SiO ₂ , to obtain a crushed fraction of 0.5-10 mm; grinding this fraction in a disintegrator until a powdery state is achieved; preparing a batch by dosing and loading the powdery fraction into a mixer, moistening with hot water to bring the humidity to 45-50%, introducing air-dry granulated alkali NaOH into the mixer, introducing a pore-forming, strengthening and water-retaining additives during the preparation of the mixture; mixing the prepared moistened batch, accompanied by self-heating, until a hot viscous mixture is obtained; stage-by-stage processing of this mixture with the possibility of ultimately obtaining a crushed semi-finished product; drying the semi-finished product and further grinding it to obtain a granulated fraction; loading this granulated fraction into a porous furnace to obtain porous granules of the finished product; cooling it in a refrigerator-classifier and distributing it in a granule storage bin by fractions, characterized in that before crushing the crushed fraction of tripoli 0.5-10 mm in a disintegrator, it is pre-dried to a residual moisture content of 3-5%; and the step-by-step processing of the hot viscous mixture with the possibility of obtaining a crushed semi-finished product is carried out in three stages: - the mixture is unloaded into a dosing extruder, followed by forming it into 150x150 mm briquettes, rolling the briquettes on rollers into 10-15 mm thick “pancakes”, followed by cooling on a conveyor to a temperature close to the ambient temperature, and crushing the “pancakes” on a grinding belt to obtain 10x10 mm pellets; - drying of semi-finished product pellets is carried out in a drying drum to a residual moisture content of 15-20%, followed by crushing of the dried pellets in a crusher to a granulated fraction of 0.25-1.5 mm; - in this case, grinding in a disintegrator is carried out to obtain a powder fraction of 80-100 μm in size, firing and porization of granules of the finished product in a porizer furnace is carried out at a temperature of 550-650°C, and alkali, pore-forming and strengthening additives are introduced into the working mixer in an amount of 0.5-17% of the mass of siliceous raw materials in terms of dry matter, and a water-retaining additive is introduced during the self-heating process.

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