WO2018236247A1

WO2018236247A1 - Composition of charge mixture for producing foamed thermal insulation material

Info

Publication number: WO2018236247A1
Application number: PCT/RU2017/000696
Authority: WO
Inventors: Константин Владимирович КУРСИЛЕВ; Виктор Александрович КАТУГИН; Василий Агафонович ЛОТОВ
Original assignee: Константин Владимирович КУРСИЛЕВ
Priority date: 2017-06-22
Filing date: 2017-09-22
Publication date: 2018-12-27
Also published as: RU2655499C1

Abstract

The invention relates to the manufacturing of thermal insulation materials with rigid structure, which have low density and low thermal conductivity. The charge mixture for producing the foamed thermal insulation material comprises amorphous siliceous rock - 50-52 mass%, sodium hydroxide – 14-16 mass %, calcined dolomitic meal - 4-6 mass %, and water – 26-28 mass %. The invention makes it possible to produce articles with pre-determined dimensions and shape from the foamed thermal insulation material with a more uniform, strong and rigid structure, a chemically stable and water-resistant glass matrix, with the minimal heat and energy consumption and at a low foaming temperature of 750-780°C.

Description

CHARGE COMPOSITION FOR OBTAINED

HEAT INSULATING MATERIAL

The invention relates to the production of heat-insulating materials with a rigid structure with low density and thermal conductivity.

Of the currently known insulation materials with a rigid structure and high construction and technical properties, foam glass is the most effective.

Thus, in the prior art, the composition of the charge for producing foam glass is known (A.S. NS1073199, SSA 11/00, BHNs6, 1984), in which the mixture does not contain either specially welded glass or broken glass, and the object of the invention is solved by use of the mixture containing (wt.%) sedimentary siliceous rock 15-70, sodium hydroxide 6-15, a blowing agent 0.02-1, 5, perlite rock - the rest.

The disadvantages of this composition are insufficient water resistance of the foam glass, as well as the need for fine grinding of difficult-to-grind perlite rock (volcanic glass) in the environment of soft siliceous rock (diatomite, tripoli, flask), which reduces the efficiency of grind perlite rock, increases its duration and energy consumption for grinding the mixture.

Also known is the composition of the mixture to obtain finely granulated foam glass-ceramic material containing silica-containing raw materials, alkaline component, dolomite and water (RU N22563861, SOPW 19/08, SOPC 11/00, published 20.09.2015, Bul. M ° 26).

The disadvantage of this composition is insufficient water resistance of the obtained insulating material, since dolomite in the non-calcined state is included in the mixture, and heating the mixture during firing and foaming of the granules to temperatures of 750-780 degrees does not lead to its complete decomposition, as a result of which the glass is enriched with magnesium oxide, and calcium carbonate, which is part of dolomite, remains in its original state, being a mechanical impurity; in addition, when heated, carbon dioxide, removing from the dolomite and already partially porous water mass of the array, destroys the latter, forming a non-uniform porous structure of the partitions, which leads to a decrease in strength and water resistance obtained material. However, since in the known composition the components of the mixture do not react to the formation of sodium hydrosilicates (due to the low concentration of the alkali solution), but simply represent a mechanical mixture, very fine grinding of the components and mechanical activation are required for the formation of glass (wet grinding to a particle size of 80 -40 microns with the formation of Zola), which entails an additional stage of drying the mixture with the removal of significant quantities of water.

In addition, in a solution with a low - less than 30% may. the concentration of sodium hydroxide does not completely dissolve the amorphous silica rock in alkali and part of the amorphous silica rock does not form part of the sodium hydrosilicate resulting from this interaction, which leads to the formation of a mechanical mixture of silica and sodium hydrosilicate. In this case, predominantly tape silicates with a silicon-oxygen motif [S14O11] ^{6 "are formed} , containing a small amount of water of crystallization and have a low porous capacity. In addition, silicates with a [S14O11] ^6" motif are not able to embed cations of metals such as Ca in their silica-oxygen motif ²⁺ , Mg ²⁺ , Fe ³⁺ , Al ³⁺ . This fact suggests that it is difficult to obtain silicates with increased water resistance from such hydrosilicates.

Also, when mixing the components, sodium hydrosilicates are not obtained due to the low concentration of reactants and their low reactivity (in the case of using soda ash), which leads to the formation of glass with low water resistance under conditions of low-temperature calcination (750-780 ° С), t. to. silicate and glass formation requires either a higher temperature (950-1200 ° C) or chemical activation (for example, the formation of active sodium hydrosilicates) to complete the reactions.

In addition, it is impossible to obtain block glass from a known composition, since when heated during the course of silicate-forming reactions, and then at the glass formation stage at temperatures of 750-780 ° C due to insufficient viscosity due to the specified composition with the specified ratio of C0 _{2, the} resulting when removing water vapor from the foam mass, the mass will shrink after the stage glass formation will result in foam glass with an extremely uneven porous structure and a pore diameter of from 3 to 20 mm with a thickness of interporous partitions of 2-5 mm. Therefore, only after pre-dispersing the suspension in a spray dryer (D1) to a particle size of 0.1 -1, 5 mm, a more uniform porisation with a residual amount of CO2 and a granule production of 0.2-3 mm is possible.

The closest in technical essence and the achieved result is the composition of the charge (RU N22606539, C OZS 1 1/00, SOPS 19/08, publ. 10.01.2017, B m.NsI), which uses the charge for the next content of components ( wt.%): amorphous silica rock - 48-55, dry sodium hydroxide - 15-18, silica-alumina component - 3-5, water - 24- 35.

The disadvantage of the closest analogue is the lack of water resistance of the foamed insulation material obtained from the mixture of known composition, which leads to the destruction of the interporous partitions and degradation of the strength of the structure of the foam glass.

The task of the patented solution is to eliminate these drawbacks, to develop the composition of the charge, which provides glass synthesis with a chemical composition similar to that of container glass, which provides for the synthesis of sodium hydrosilicates during the mixing of silica, dry sodium hydroxide and water for 5-7 minutes. and obtaining a waterproof insulating block foam glass at a foaming temperature in the range of 750-780 ° C.

The technical result of the patented solution is to obtain products - block foam glass with specified dimensions and shape of foam insulation material with high resistance to water, as well as a more uniform, durable and rigid structure, chemically resistant glass matrix, with minimal heat and energy costs and at a low foaming temperature of 750 -780 ° C.

The claimed technical result is achieved in the mixture to obtain foamed insulating material containing amorphous silica rock, sodium hydroxide, calcined dolomite flour and water in the following ratio, wt.%: Amorphous Siliceous Rock 50-52,

Sodium hydroxide 14-16,

Calcined dolomite flour 4-6,

Water 26-28. The introduction of calcined, at a temperature of 920-930 ° C, dolomite flour into a mixture of this component composition in an amount of 4-6% provides the required amount of calcium and magnesium oxides in glass, which positively affects the properties of the thermal insulation material: high water resistance, chemical resistance and strength, at a low foaming temperature of 750-780 ° C. For a successful foaming process, glasses of a certain chemical composition are used. Multicomponent oxide silicate systems have a complex interrelation of parameters. The best conditions for the formation of stable foams is a high viscosity of the melts with low surface tension. To form a charge that perfectly meets these requirements is very problematic, since the influence of many oxides on these parameters is often the opposite. It is possible to form a mixture with a certain agglomerate of technological properties, allowing to realize the foaming process and to obtain a durable, chemically resistant product. It is established that the content of calcium oxide in the glass within 5-10% positively affects the foaming process, the chemical resistance and strength of the heat-insulating material obtained, however, the excess reduces the viscosity and leads to crystallization of the glass, and the content of magnesium oxide most favorable for the foaming process calcium oxide is in the range of 2-6%, since the excess content of magnesium oxide will reduce the water resistance of glasses and increases their tendency to crystallization.

Thus, the introduced calcined dolomite, which contains calcium and magnesium oxides (48-58% CaO and 35-42% MgO), in an amount of 4-6 wt.%, In combination with the other components in the specified range, allows to form the most technologically advanced composition, the closest in chemical composition to tare glass, providing foamed heat-insulating material, which has a low temperature of porosity, but has high water resistance and durability. Through the use of calcined dolomite flour, both oxides (CaO and MDO) are introduced into the mixture, which react with water, which leads to a multiple increase in the dispersion of the products. Calcium and magnesium oxides undergo sequential transformation first into hydrates, which then enter into a physicochemical interaction with the rest of the charge (amorphous silica and sodium hydroxycate), causing gelation, then again decompose to oxides when heated and enter into silicate reactions, and then and glass formation. The transition of oxides to the hydrate form, and then again to the oxide form, is accompanied by a decrease in the particle size of 100–10,000 times, which leads to a significant decrease in the required energy for the required reactions to take place.

At the same time, due to the introduction of both oxides (CaO and MDO) into the mixture, which, in combination with the other components in the indicated range, are additionally dispersed during hydration and enter into silicate-forming reactions more intensely, heat and energy costs are reduced. Also, when using calcined dolomite flour, when a mixture of calcium and magnesium oxides comes into contact with sodium hydrosilicate water, these oxides are quenched with the formation of nanodispersed calcium and magnesium hydroxides, which leads to the accelerated formation of sodium calcium and sodium magnesium silicates, which leads to more intensive silicate formation and subsequently glass formation. At the same time, the quenching of calcium and magnesium oxides is accompanied by the release of heat of dissolution of NaOH - 1237 J / g, CaO - 1160 J / g, MDO - 1222 J / g. The heat released allows the mixture to heat up to temperatures of 108-110 ° C, as a result the mixture boils and the dissolution of amorphous silica in alkali is carried out more efficiently.

Thus, the use of calcined dolomite flour leads to additional heating of the mixture and, in addition, the binding of free water of sodium hydrosilicate due to the formation of calcium and magnesium hydroxides, which cause the mixture to harden, both due to chemical interaction with sodium hydrosilicate and due to the binding of free water in an amount of from 1, 7 to 2.6% by weight. The effect of chemical binding of free water allows you to dramatically increase the viscosity of the mixture and exclude the operation of drying the mixture before its granulation, as well as reducing energy costs for the necessary reactions of silicate formation and glass formation.

Use in the composition of the mixture of sodium hydroxide 14-16 wt.% And water 26-28 wt.% Allows to obtain an aqueous solution of sodium hydroxide with a concentration of 33-38%, and introduced with this amorphous silica rock in the amount of 40-41, 6 wt.%, which is 80% of the total amount of the entire amorphous kremenzydy breed in the mixture (only 50-52 wt.%), completely dissolved in an alkaline solution of sodium hydroxide, forming mainly sodium hydrosilicate with a silicate module m = Si0 ₂ / Na ₂ 0 = 2.7-3.3, which is able, especially under hydrothermal conditions, to absorb an additional 10% of emnezomistoy breed introduced together with the calcined dolomite flour (4-6%), to interact with calcium and magnesium oxides to form glass, similar in composition to the glass container.

The remaining part of the amorphous siliceous rock, which makes up 10% of the total amount of the amorphous kreminzydy rock in the charge (only 50-52 wt.%), Is used to dust the resulting granules, resulting in sticking of the granules during granulation of the charge and forming a honeycomb structure of the products during porization .

Diatomite, flask or tripilla in finely dispersed state - less than 0.1 mm in size can be used as a siliceous rock, consisting mainly of amorphous silica, which leads to the formation of sodium hydrosilicate, which is the basis for the synthesis of glass, which is similar in composition to glass.

In particular, calcined dolomite flour contains 48-58 wt.% Calcium oxide and 35-42 wt.% Magnesium oxide in its composition (by weight of the calcined dolomite flour).

The invention is illustrated by examples of obtaining foamed insulating material from the presented composition of the charge, the data table, which shows the chemical composition of various glasses obtained from the mixture represented by the chemical composition and the chemical composition of the prototype, and test data. Obtaining foamed insulation material in the particular case is as follows.

Example 1

1. As raw materials in the preparation of the charge used Tripoli Zikeevsky field (Kaluga region) with S1O2 content - 84.5% and a particle size less than 0.1 mm, granulated sodium hydroxide (less than 2 mm), calcined at a temperature of 920-930 ° C dolomite flour with a CaO content of 48-58%, MDO 35-42%.

2. Preparation of the charge began with the synthesis of sodium hydrosilicate with a silicate module m = 2.7-3.3 by mixing 16 wt.% Dry sodium hydroxide, 40.8 wt.% Amorphous silica rock, which is 80% of the total amount of amorphous Kremenzydy breed (in the mixture of all - 51 wt.%), and 28 wt.% hot water temperature 80-85 ° C. In this case, the concentration of an aqueous solution of sodium hydroxide was 36.4 wt.%, In which the silica rock was intensively dissolved, and their mixture was heated to a temperature above 100 ° С (boiling). After stirring the hot mixture for 10 minutes. a mixture was obtained, mainly containing sodium hydrosilicate with a density of 1400 kg / m ³ .

3. In the resulting sodium hydrosilicate, a mixture of 5.1 wt.% Of silica rock was injected, which is 10% of the total amount of all amorphous kremenemisty rock in the charge (51 wt.% In total), and 5 wt.% Of calcined dolomite flour, the mixture was thoroughly mixed. to obtain a plastic, solid-like mass, which was fed into a screw granulator equipped with a knife-lattice forming pair, which allows thoroughly homogenizing the mixture, from which granules with a diameter of 3-5 mm and a length of 5-10 mm were molded. The CaO and MDO oxides, introduced with calcined dolomite flour, interacted with the free water of sodium hydrosilicate and turned into hydroxides Ca (OH) g and MD (OH) g, which accelerated the hardening of the mass and the granules.

4. At the exit from the granulator, the granules were powdered with 5.1% by weight of amorphous silica rock, which is 10% of the total amount of the entire amorphous kreminesy rock in the charge (51% by weight), then the granules together with the dusting additive were fed into a dish granulator surface pelleting, after which the granules were dried to a residual moisture content of 16-18%.

5. Granulated mixture was loaded into a metal form with an internal volume of 0.5 dm ³ (10x10x5) cm, the form was closed with a lid with clamps and placed in a muffle furnace, preheated to a temperature of 750-780 ° C and kept at this temperature for 20 30 min.

When a high temperature is applied to the charge, various physical and chemical processes begin to take place in it. First of all, as a result of heating the mixture to 150-300 ° C, sodium hydrosilicate dehydrates with water being released in the form of water vapor, which, under conditions of a persistent alkaline environment, contributes to a very intensive and aggressive dissolution of free silica and the formation of an additional amount of sodium hydrosilicate. The dissolution of silica and its transition into sodium hydrosilicate increases the silicate modulus of the mixture to m = 3.4-4.1 and leads to an increase in the porosity of the mixture. In the temperature range of 350–450 ° C, the process of dehydration of sodium hydrosilicates coincides with the process of transition of the mixture to the pyroplastic state, and the evolved water vapor penetrates the sodium silicate glass, which up to the final temperature of the porization is actively enriched with oxides of calcium, magnesium, iron and aluminum. the composition of dolomite flour and amorphous silica rock.

6. After foaming, the form with the product was cooled together with the furnace for 5 hours. The form was disassembled and the product was removed from it, in which the density, strength, thermal conductivity and water absorption were determined.

Example 2

Foamed insulation material was obtained in the above sequence from the mixture of the following composition (in wt.%) Amorphous silica rock 50, sodium hydroxide 16, calcined dolomite flour 6, water 28.

Example 3

Foamed insulation material was obtained in the above sequence from the mixture of the following composition (in wt.%) Amorphous silica rock 52, sodium hydroxide 14, calcined dolomite flour 6, water 28.

Example 4

Foamed thermal insulation material was obtained in the above sequence from the mixture of the following composition (in wt.%) Amorphous silica rock 52, sodium hydroxide 16, calcined dolomite flour 4, water 28.

Example 5

Foamed insulating material was obtained in the above sequence from the mixture of the following composition (in wt.%) Amorphous silica rock 52, sodium hydroxide 16, calcined dolomite flour 6, water 26.

All experimental samples had a clear geometric shape and specified dimensions. The properties of the samples obtained are as follows: density - 150-280 kg / m ³ , compressive strength - 1, 8-3.5 MPa, thermal conductivity coefficient - 0.063-0.086 W / (m glad), water absorption - 5-8% (vol. ).

The table shows the chemical compositions of glasses obtained from various components, including the composition of the glass according to the prototype and the claimed composition.

Table

Comparative water resistance of the products was evaluated by the pH value (extract of the obtained samples in distilled water for 7 days). For sodium silicate glass, obtained by the method specified in the prototype, pH = 8.0-8.7, and for the claimed composition, pH = 7.3-7.8, the pH of the tare glass under similar conditions is 7.7, and silicate - clumps - 10-11, 2 (depending on the chemical composition).

Thus, the proposed composition of the mixture to obtain a foamed thermal insulation material allows us to obtain sodium-calcium magnesium silicate glass with high water resistance, from which the porous matrix of heat-insulating material is formed.

Thermal insulation material obtained from the presented composition of the charge with minimal heat and energy costs has a rigid structure, specified characteristics, dimensions and shape. In addition, compared with the known composition of the mixture, in the present invention, the introduction of calcined dolomite flour in the specified amount and when interacting with other components of the mixture in the specified amount leads to an increase in chemical resistance and water resistance of the glass matrix of products.

The proposed composition of the mixture allows to obtain products in the form of blocks, since the porisation of the array occurs at a temperature of 750-780 ° C due to the release of water vapor during the decomposition of sodium hydrosilicate and the transformation of the gel-like structure of the raw granules into xerogel with the subsequent transition of the xerogel to the priroplastic state. Upon reaching the priroplastic state in the porous mixture, the formation of sodium calcium calcium and sodium magnesium silicates starts to flow, from which at the glass formation stage strong interpore partitions with a given glass chemical composition are formed that provide the necessary water resistance not inferior to the water resistance of the container glass. In the proposed composition, the release of CO2 and its harmful effects are excluded due to the use of calcined dolomite flour. Upon receipt of products in the form of blocks, non-calcined dolomite flour cannot be used, since the evolved C0 _{2 will} destroy the porous structure formed during the release of water vapor.

Obtained according to the invention, the insulating material can be used in construction, for thermal insulation of power plants and pipeline transport.

Claims

Claim

1. The mixture to obtain foamed insulating material containing amorphous silica rock, sodium hydroxide and water, characterized in that it further contains calcined dolomite flour in the following ratio, wt.%:

Amorphous Siliceous Rock 50-52,

Sodium hydroxide 14-16,

Calcined dolomite flour 4-6,

Water 26-28.

2. The mixture according to claim 1, characterized in that use dolomite flour calcined at a temperature of 920-930 ° C.

3. The mixture according to claim 1, characterized in that diatomite is used as an amorphous silica-bearing rock, a flask or a tripoli in a finely dispersed state - less than 0.1 mm in size.

4. The mixture according to claim 1, characterized in that the calcined dolomite flour contains 48-58 wt.% Calcium oxide and 35-42 wt.% Magnesium oxide in its composition.