WO2019184637A1 - Calcium magnesium silicate thermal insulation material, preparation method therefor and use thereof - Google Patents

Abstract

Disclosed are a magnesium xonolite thermal insulation material, a preparation method therefor and the use thereof. The method comprises the following steps: (1) a calcination pretreatment of magnesite and limestone, so as to prepare calcium oxide and magnesium oxide powders; (2) the preparation of a raw slurry; (3) dynamic hydrothermal synthesis, so as to prepare an active slurry of calcium magnesium silicate; and (4) pressure filtration and forming, and drying to obtain a finished product. The main crystal phase of the calcium magnesium silicate thermal insulation material prepared by the dynamic hydrothermal synthesis method is magnesium-containing xonotlite, has the advantages of a low thermal conductivity coefficient, a low bulk density, a high compressive strength and a good high-temperature stability, and can be used as a thermal insulation material for building interior walls, kilns, etc.

Description

Calcium silicate calcium thermal insulation material and preparation method and application thereof Technical field

The invention belongs to the field of thermal insulation materials and relates to magnesium oxide, in particular to a calcium silicate magnesium thermal insulation material prepared by partially replacing calcium raw materials by using magnesium oxide (or other magnesium raw materials such as magnesium hydroxide), and a preparation method thereof. application.

Background technique

Portland cement production needs to consume a large amount of non-renewable mineral resources. The most consumed is high-quality limestone. China only consumes 2 billion tons of high-grade limestone per year. It is estimated that China's cement industry alone will consume 30 billion tons of high-grade limestone in the next 20 years.

According to the mineral composition, limestone can be divided into high calcium limestone (CaCO ₃ > 95wt%), magnesium limestone (CaCO ₃ : 80 ~ 90wt%; MgCO ₃ : 5 ~ 15wt%) and dolomitic limestone (CaCO ₃ : 50 ~ 80wt %; MgCO ₃ : 15 to 45 wt%). According to relevant statistics, China's proven reserves of limestone are about 73 billion tons, of which about 30 billion tons of high-grade limestone and about 40 billion tons of low-grade limestone, and mainly magnesium-rich limestone. In cement production, the content of MgO in raw materials is strictly limited, and a large amount of high-quality limestone mineral resources are consumed. At the same time, it also caused idle waste of about 40 billion tons of magnesium-rich low-grade limestone. The invention replaces the calcium raw material with the magnesium raw material to prepare the magnesium-hard xonotlite thermal insulation material by high temperature and high pressure dynamic hydrothermal synthesis, and can remove the application limitation of the magnesium-rich low-grade limestone in the building materials field.

The dynamic hydrothermal synthesis of the xonotlite insulation material can reach a temperature of up to 1000 ° C, and the fibrous xonotlite crystals are interwoven under the action of centrifugal force to form hollow spherical secondary particles, which makes it have lower heat conduction. Coefficient, higher strength and relatively low bulk density. Different bulk density xonotlite insulation materials have different performance indexes, the bulk density is less than 130kg/m ³ , the thermal conductivity is less than 0.049W/m·K, the bulk density is less than 220kg/m ³ , and the thermal conductivity is less than 0.062W/m·K; The bulk density is less than 240kg/m ³ and the thermal conductivity is less than 0.095W/m·K. Moreover, the xonotlite type thermal insulation material has the advantages of fireproofing, soundproofing, and the like, and is harmless to the human body, and is a kind of all-green thermal insulation material. The main raw materials for the production of xonotlite products at home and abroad are quicklime, slaked lime, etc. The quality of calcium raw materials is relatively high, and a large amount of high-quality limestone is consumed. There have been no reports on the preparation of magnesium-hard xonotlite insulation materials from magnesium-containing low grade limestone. The invention prepares magnesium-hard xonotlite insulation materials with different magnesium content by means of compounding to guide the application of magnesium-containing low-grade limestone in the field of building materials.

Summary of the invention

In order to overcome the above disadvantages and disadvantages of the prior art, the primary object of the present invention is to provide a method for preparing a calcium silicate magnesium thermal insulation material by replacing a part of the calcium raw material with a magnesium raw material.

Another object of the present invention is to provide a calcium silicate magnesium thermal insulation material prepared by the above method.

Still another object of the present invention is to provide the use of the above calcium silicate magnesium thermal insulation material.

The object of the invention is achieved by the following scheme:

A method for preparing a calcium silicate magnesium thermal insulation material by replacing a part of the calcium raw material with a magnesium raw material, which mainly comprises the following steps:

(1) Pretreatment of calcium raw materials and magnesium raw materials: the magnesite and limestone are respectively raised to 600-950 ° C at a heating rate of 5 to 10 ° C / min, and then calcined for 1 to 3 hours, and then cooled to room temperature after completion of calcination. After that, grinding and passing through a 200 mesh sieve to prepare active calcium oxide powder and active magnesium oxide powder;

(2) preparation of raw slurry: the active calcium oxide powder obtained in the step (1), the active magnesium oxide powder, the siliceous raw material and water are mixed in a certain ratio, and stirred to obtain a raw slurry;

(3) Dynamic hydrothermal synthesis: the raw slurry obtained in the step (2) is added to a high-temperature and high-pressure magnetically driven reaction vessel, and the high-temperature and high-pressure reaction is carried out under magnetic stirring conditions, and after cooling, the mixture is cooled to room temperature to obtain a magnesium-hard. Brasilite active slurry;

(4) Forming and drying: the active slurry obtained in the step (3) is allowed to stand and precipitate, the supernatant liquid is removed, and the lower active slurry is injected into the molding die, and the slurry is filtered at a pressurization rate of 5 to 10 N/s. The water in the water, 2 ~ 4KN for 60s, demoulding and drying, to obtain the finished product.

The siliceous material described in the step (2) is silica fume or quartz powder having an average particle size of 1 to 4 μm, preferably silica fume;

The amount of the active calcium oxide powder, the active magnesium oxide powder, the siliceous material and the water in the step (2) is such that the ratio of the sum of the moles of calcium oxide and magnesium oxide to the number of moles of SiO ₂ is 1:1; The ratio of the number of moles of magnesium oxide to the sum of the moles of calcium oxide and magnesium oxide is 0 to 0.2, preferably 0 to 15.15%, more preferably 10%; water and solid phase (calcium oxide + magnesium oxide + SiO ₂ ) The mass ratio of the total amount is 20 to 60:1;

The high temperature and high pressure reaction described in the step (3) means that the temperature is raised to 210 to 240 ° C at a rate of 2 to 3 ° C / min, the heat treatment reaction is 10 to 24 hours, and the pressure in the kettle is 2.0 to 3.0 MPa when the temperature is maintained;

The magnetic stirring described in the step (3) means magnetic stirring at a speed of 100 to 400 r/min.

The static precipitation described in the step (4) means standing precipitation for 20 to 40 minutes;

The dwell time described in the step (4) is calculated from the non-aqueous filtration; the drying is carried out in two steps, first drying at a low temperature of 40 to 60 ° C for 4 to 6 h, and then drying at a high temperature of 80 to 110 ° C to Constant weight.

A calcium silicate magnesium thermal insulation material prepared by the above method.

The above-mentioned calcium silicate magnesium thermal insulation material is applied in the interior wall of the building, the kiln, the metallurgy and the like.

The mechanism of the invention is:

The invention combines calcium raw material, magnesium raw material, siliceous raw material and water into a raw slurry in a certain proportion, and reacts in a high temperature and high pressure magnetic driven reaction kettle, and the reaction process is continuously stirred to make fibrous magnesium-hard silicon. The calcium carbide crystal forms a secondary particle having a "chestnut shell"-like structure under the action of eddy current, that is, an active slurry, and then is subjected to pressure filtration molding, drying, coating with a waterproof coating, and drying to obtain a finished product.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The magnesium-hard xonotlite heat insulating material of the present invention, the magnesium raw material replaces part of the calcium raw material, and the substitution amount is 0-15.15% by weight, which can be used for guiding magnesium limestone (CaCO ₃ : 80-90 wt%; MgCO ₃ : 5 ~ 15wt%) to prepare calcium silicate magnesium insulation material, reduce the use of high-quality limestone, but also avoid the idle waste of magnesium limestone.

(2) The calcium silicate magnesium thermal insulation material of the invention has the characteristics of low bulk density, small thermal conductivity, high strength and high use temperature, and has the same performance as the xonotlite insulation material, and can be used as a building inner wall and a kiln. Insulation Materials.

(3) The invention adopts high temperature and high pressure dynamic hydrothermal synthesis to exchange magnesium ions with calcium ions in the xonotlite crystal, and the product has no magnesium hydroxide or other magnesium containing phase, thus ensuring the calcium silicate. High temperature stability of magnesium insulation materials.

DRAWINGS

1 is an X-ray diffraction (XRD) pattern of magnesium-hard xonotlite of a calcium silicate magnesium thermal insulation material prepared in Examples 1, 2, 3, and 4;

2 is a scanning electron microscope (SEM) image of secondary particles of the magnesium-hard xonotlite of the calcium silicate magnesium thermal insulation material prepared in Examples 1, 2, 3, and 4 at the same scale.

detailed description

The present invention will be further described in detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

The reagents used in the examples are commercially available from the market unless otherwise specified.

The magnesite used in the examples is the first product of Liaoning Haicheng. The calcined magnesium content can reach 97% after calcination, and the calcium oxide content after calcination can reach 98%.

Example 1

The magnesite and limestone were calcined at 950 ° C, incubated for 2 h, cooled to room temperature, and ground through a 200 mesh sieve. According to the molar ratio of (CaO+MgO) to SiO _{2 of} 1:1, the molar ratio of MgO to (CaO+MgO) is 0.1, the mass ratio of water to solid phase is 40:1, mixed with quartz powder and water with an average particle size of 2.24 μm, and stirred. Make a raw slurry evenly. The raw slurry was added to a high-temperature and high-pressure magnetic stirring reactor, the stirring speed was 250 r/min, the temperature was raised to 220 ° C in 90 minutes, the pressure was 2.1 MPa, and the dynamic hydrothermal synthesis of magnesium-hard xonotlite was carried out for 12 hours. Immediately after the completion of the heat preservation, the circulating water was cooled, and cooled to room temperature to obtain a magnesium-hard xonotlite active slurry. The active slurry was allowed to stand and precipitated for 30 min, the supernatant liquid was removed, and the lower active slurry was injected into a molding die, and the water in the slurry was filtered at a pressure rate of 5 N/s, and the pressure was dried for 2 s for 60 s, and the mold was dried. It is dried at a low temperature of 60 ° C for 4 h, and then dried at a high temperature of 80 ° C to a constant weight to obtain a finished product.

Example 2

The magnesite and limestone were calcined at 950 ° C, incubated for 2 h, cooled to room temperature, and ground through a 200 mesh sieve. According to the molar ratio of (CaO+MgO) to SiO _{2 of} 1:1, the molar ratio of MgO to (CaO+MgO) is 0.2, the mass ratio of water to solid phase is 40:1, mixed with quartz powder and water with an average particle size of 2.24 μm, and stirred. Make a raw slurry evenly. The raw slurry was added to a high-temperature and high-pressure magnetic stirring reactor, the stirring speed was 250 r/min, the temperature was raised to 220 ° C in 90 minutes, the pressure was 2.1 MPa, and the dynamic hydrothermal synthesis of magnesium-hard xonotlite was carried out for 12 hours. Immediately after the completion of the heat preservation, the circulating water was cooled, and cooled to room temperature to obtain a magnesium-hard xonotlite active slurry. The active slurry was allowed to stand and precipitated for 30 min, the supernatant liquid was removed, and the lower active slurry was injected into a molding die, and the water in the slurry was filtered at a pressure rate of 5 N/s, and the pressure was dried for 2 s for 60 s, and the mold was dried. It is dried at a low temperature of 60 ° C for 4 h, and then dried at a high temperature of 80 ° C to a constant weight to obtain a finished product.

Example 3

The magnesite and limestone were calcined at 950 ° C, incubated for 2 h, cooled to room temperature, and ground through a 200 mesh sieve. According to the molar ratio of (CaO+MgO) to SiO _{2 of} 1:1, the molar ratio of MgO to (CaO+MgO) is 0.1, the mass ratio of water to solid phase is 40:1, mixed with silica fume and water, and stirred to form raw meal. Pulp. The raw slurry was added to a high-temperature and high-pressure magnetic stirring reactor, the stirring speed was 250 r/min, the temperature was raised to 220 ° C in 90 minutes, the pressure was 2.1 MPa, and the dynamic hydrothermal synthesis of magnesium-hard xonotlite was carried out for 12 hours. Immediately after the completion of the heat preservation, the circulating water was cooled, and cooled to room temperature to obtain a magnesium-hard xonotlite active slurry. The active slurry was allowed to stand and precipitated for 30 min, the supernatant liquid was removed, and the lower active slurry was injected into a molding die, and the water in the slurry was filtered at a pressure rate of 5 N/s, and the pressure was dried for 2 s for 60 s, and the mold was dried. It is dried at a low temperature of 60 ° C for 4 h, and then dried at a high temperature of 80 ° C to a constant weight to obtain a finished product.

Example 4

The magnesite and limestone were calcined at 950 ° C, incubated for 2 h, cooled to room temperature, and ground through a 200 mesh sieve. According to the molar ratio of (CaO+MgO) to SiO _{2 of} 1:1, the molar ratio of MgO to (CaO+MgO) is 0.2, the mass ratio of water to solid phase is 40:1, mixed with silica fume and water, and stirred to form raw meal. Pulp. The raw slurry was added to a high-temperature and high-pressure magnetic stirring reactor, the stirring speed was 250 r/min, the temperature was raised to 220 ° C in 90 minutes, the pressure was 2.1 MPa, and the dynamic hydrothermal synthesis of magnesium-hard xonotlite was carried out for 12 hours. Immediately after the completion of the heat preservation, the circulating water was cooled, and cooled to room temperature to obtain a magnesium-hard xonotlite active slurry. The active slurry was allowed to stand and precipitated for 30 min, the supernatant liquid was removed, and the lower active slurry was injected into a molding die, and the water in the slurry was filtered at a pressure rate of 5 N/s, and the pressure was dried for 2 s for 60 s, and the mold was dried. It is dried at a low temperature of 60 ° C for 4 h, and then dried at a high temperature of 80 ° C to a constant weight to obtain a finished product.

The X-ray diffraction (XRD) pattern of the magnesium-hard xonotlite of the calcium silicate magnesium thermal insulation material prepared in Examples 1 to 4 is shown in Fig. 1. It can be seen from Fig. 1 that the phase composition of the product is only hard silicon. Calcium stone, the magnesium oxide added to the raw material disappeared, neither magnesium hydroxide nor hydrated magnesium silicate was formed. At the same time, the diffraction peak of the xonotlite produces a distinct secondary peak at about 27 degrees, which also reflects the magnesium ion entering the xonotlite lattice to form calcium magnesium silicate.

Scanning electron microscopy (SEM) images of the secondary particles of the magnesium-hard xonotlite of the calcium silicate thermal insulation material prepared in Examples 1 to 4 are shown in Fig. 2.

Magnesium content test: X-ray fluorescence spectroscopy (XRF) of PANalytical, the Netherlands, was used to analyze the composition of the synthetic product magnesium-hard xonotlite. The synthesized products of Examples 1, 2, 3, and 4 were washed with deionized water, filtered three times, and dried. The XRF component analysis results are shown in Table 1.

Table 1 Results of XRF component analysis of the synthesized products in Examples 1 to 4

Sample	Example 1	Example 2	Example 3	Example 4
CaO (wt%)	46.58	47.23	45.95	48.45
MgO (wt%)	39.12	36.42	38.24	36.39
SiO 2 (wt%)	2.88	5.12	3.39	5.74
MgO/(CaO+MgO)	0.09	0.16	0.11	0.18
(CaO+MgO)/SiO 2	0.99	0.99	1.00	0.98

As can be seen from Table 1, the magnesium content of the products in Examples 1 to 4 is equivalent to the amount of the magnesium raw material added before the reaction, that is, the magnesium ion replaces the xonotlite lattice during the reaction. The calcium ions in the form form magnesium-hard xonotlite crystals rather than magnesium hydroxide or other magnesium-containing phases.

Insulation material performance test: performance test mainly according to GB/T 5486-2008 "Inorganic hard insulation products test method" for thermal insulation material thermal conductivity, bulk density, compressive strength, etc., the specific performance indicators are shown in Table 2.

Table 2 Data of thermal conductivity, bulk density and compressive strength of the products in Examples 1-4

As can be seen from Table 2, the magnesium-hard xonotlite insulation materials prepared in Examples 1-4 substantially satisfy the performance indexes of the hard xonotlite insulation materials, wherein the magnesium-hard silicon prepared by the molar ratio of MgO and CaO+MgO is 0.1. Calcium stone insulation material has low bulk density and low thermal conductivity, and it is better to use silica fume as siliceous material to synthesize magnesium-hard xonotlite insulation material.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and combinations thereof may be made without departing from the spirit and scope of the invention. Simplifications should all be equivalent replacements and are included in the scope of the present invention.

Claims (9)

1. A method for preparing a calcium silicate magnesium thermal insulation material, characterized in that the method comprises the following steps:

   (1) Pretreatment of calcium raw materials and magnesium raw materials: the magnesite and limestone are respectively raised to 600-950 ° C at a heating rate of 5 to 10 ° C / min, and then calcined for 1 to 3 hours, and then cooled to room temperature after completion of calcination. After that, grinding and passing through a 200 mesh sieve to prepare active calcium oxide powder and active magnesium oxide powder;

   (2) preparation of raw slurry: the active calcium oxide powder obtained in the step (1), the active magnesium oxide powder, the siliceous raw material and water are mixed in a certain ratio, and stirred to obtain a raw slurry;

   (3) Dynamic hydrothermal synthesis: the raw slurry obtained in the step (2) is added to a high-temperature and high-pressure magnetically driven reaction vessel, and the high-temperature and high-pressure reaction is carried out under magnetic stirring conditions, and after cooling, the mixture is cooled to room temperature to obtain a magnesium-hard. Brasilite active slurry;

   (4) Forming and drying: the active slurry obtained in the step (3) is allowed to stand and precipitate, the supernatant liquid is removed, and the lower active slurry is injected into the molding die, and the slurry is filtered at a pressurization rate of 5 to 10 N/s. The water in the water, 2 ~ 4KN for 60s, demoulding and drying, to obtain the finished product.
2. The method for preparing a calcium silicate magnesium thermal insulation material according to claim 1, wherein:

   The siliceous material described in the step (2) is silica fume or quartz powder having an average particle size of 1 to 4 μm.
3. The method for preparing a calcium silicate magnesium thermal insulation material according to claim 2, wherein:

   The siliceous material described in the step (2) is silica fume.
4. The method for preparing a calcium silicate magnesium thermal insulation material according to claim 1, wherein:

   The amount of the active calcium oxide powder, the active magnesium oxide powder, the siliceous material and the water in the step (2) is such that the ratio of the sum of the moles of calcium oxide and magnesium oxide to the number of moles of SiO ₂ is 1:1; The ratio of the number of moles of magnesium oxide to the sum of the moles of calcium oxide and magnesium oxide is 0 to 0.2; and the mass ratio of water to solid phase is 20 to 60:1.
5. The method for preparing a calcium silicate magnesium thermal insulation material according to claim 1, wherein:

   The amount of the active calcium oxide powder, the active magnesium oxide powder, the siliceous material and the water in the step (2) is such that the ratio of the sum of the moles of calcium oxide and magnesium oxide to the number of moles of SiO ₂ is 1:1; The ratio of the number of moles of magnesium oxide to the sum of the moles of calcium oxide and magnesium oxide is from 0 to 15.15%; the mass ratio of water to solid phase is 40:1.
6. The method for preparing a calcium silicate magnesium thermal insulation material according to claim 1, wherein:

   The high temperature and high pressure reaction described in the step (3) means that the temperature is raised to 210 to 240 ° C at a rate of 2 to 3 ° C / min, the heat treatment reaction is 10 to 24 hours, and the pressure in the kettle is 2.0 to 3.0 MPa when the temperature is maintained;

   The magnetic stirring described in the step (3) means magnetic stirring at a speed of 100 to 400 r/min.
7. The method for preparing a calcium silicate magnesium thermal insulation material according to claim 1, wherein:

   The static precipitation described in the step (4) means standing precipitation for 20 to 40 minutes;

   The dwell time described in the step (4) is calculated from the non-aqueous filtration; the drying is carried out in two steps, first drying at a low temperature of 40 to 60 ° C for 4 to 6 h, and then drying at a high temperature of 80 to 110 ° C to Constant weight.
8. A calcium silicate silicate thermal insulation material prepared by the method according to any one of claims 1 to 7.
9. The use of the calcium silicate magnesium thermal insulation material according to claim 8 in interior walls, kiln and metallurgy of buildings.

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