With the increasing shortage of energy, countries are paying more and more attention to the development, production and use of energy-saving materials for high-temperature industries. Because of its high softening temperature under load, good volume stability at high temperature, and non-shrinkage in long-term use, silica bricks have been widely used and studied in lightweight refractory systems.
Due to the rapid crystalline transformation of silica during heating, large volume expansion is generated, making the firing of silica bricks more difficult than other refractory materials. The core technology of making silica bricks is the selection and application of mineralizers. Its purpose is to control the volume expansion caused by the large stress in the bricks due to the crystal transformation of silica during the firing process of the silica bricks, and to prevent the silica bricks from being Cracks during firing. It is required to convert quartz into stable high-temperature mineral phases tridymite and cristobalite as much as possible during the firing of silica bricks. In order to promote this conversion, mineralizers are usually added in the process of making silica bricks. Mineralizer is an oxide that can react with silica to form a liquid phase. Its function is to accelerate the conversion of quartz without significantly reducing the refractoriness of the product, and can inhibit the stress caused by expansion during the firing of the brick, and prevent the product from being loose Or cracking.
At present, most of the mineralizers actually used in the production of silica bricks are iron oxide and calcium oxide, which not only have the above characteristics, but also ensure that the silica bricks have good high-temperature mechanical properties. However, the iron oxide and calcium oxide used in the production are added in the form of fine powder and lime milk respectively. The particle size of the former is not fine enough and the dispersion in the silica brick is not even enough; the latter is actually calcium hydroxide and its lime milk solution It is easy to flocculate and not easy to disperse, so it is less effective as a mineralizer.
In 2004, Geim and Novoselov of the University of Manchester in the United Kingdom obtained independent two-dimensional graphene (Gra-phene, GN) crystals through tape stripping of highly oriented graphite. Graphene has become a research hotspot in the field of materials science. one. Graphene, actually a single atomic layer of graphite, has a unique two-dimensional structure and excellent force
Academic, thermodynamics, optical and electrical properties. Graphene is currently the world’s thinnest but hardest nanomaterial. It is almost completely transparent and absorbs 2.3% of light. Its thermal conductivity is as high as 5300W/m·k, which is higher than carbon nanotubes and diamonds. Graphene is a new material with a single-layer sheet structure composed of carbon atoms. It has the characteristics of high strength, large specific surface area, high chemical reaction activity, and high filling ability.
This article introduces a method for making silicon carbide bricks using graphene as a mineralizer. The purpose is to solve the problem that the iron oxide particle size is not fine enough when the existing silicon bricks are made, and the dispersion in the silicon bricks is not even enough; calcium oxide is actually added Calcium hydroxide, its lime milk solution is easy to flocculate, and it is not easy to disperse. By solving the above problems, a graphene silicon carbide brick with excellent thermal shock resistance, strong resistance to slag and alkali metal corrosion, erosion resistance, excellent heat insulation performance, and high temperature volume stability is made.
Technical solutions:
With silica as the main raw material, the main raw material of silica is divided into silica particles, silica powder, silica coarse powder and silica fine powder according to the particle size.
Graphene silicon carbide bricks are composed of the following weight percentages: 15-30% silica particles, 20-40% silica powder, 10-20% coarse silica powder, 9-13% silica fine powder, 10-20% graphene, composite Mineralizer 1.5-2.5%, binding agent 2-5% and nano silicon carbide 1.5-3%.
In this technical solution, graphene is a new material with a single-layer sheet structure composed of carbon atoms, which has the characteristics of high strength, large specific surface area, high chemical reaction activity, and high filling ability; graphite is added to silicon bricks The olefin makes the internal contact of the silica brick closer, thereby reducing the stress caused by expansion during firing and preventing the product from being loose Or cracking; the high strength of graphene ensures the excellent mechanical properties of silica bricks, and at the same time can improve the acid and alkali corrosion resistance of silica bricks.
Preferably, the particle size of silica particles is 3.5-5 mm, the particle size of silica powder is 1-3 mm, the particle size of coarse silica powder is 220-400 µm, and the particle size of fine silica powder is 0.5-2 µm. Preferably, the weight parts of the components in the raw material composition of the composite mineralizer are: 40 parts granite, 20 parts fluorite, 25 parts potash feldspar, 20 parts diatom mud, 2 parts boron nitride, 3 parts Glass beads and 5 parts of nano-zinc oxide. In this technical solution,
The glass beads have suitable particle size, good fluidity, and high dispersion. Adding glass beads to the composite mineralizer can be highly uniformly dispersed inside the silica brick, promote sintering, and make the silica brick have a more uniform structure and improve the product The strength and thermal shock resistance of nano-zinc oxide are fine, which can fill fine pores, reduce the porosity of the product, and increase the volume density.
Production method 1.:
Using silica as the main raw material, the main raw material of silica is divided into silica particles, silica powder, silica coarse powder and silica fine powder according to the particle size. The graphene silicon carbide brick is composed of the following weight percentages: silica particles 15%, silica powder
The weight of each component in the raw material composition of the composite mineralizer is: 40 parts granite, 20 parts fluorite, 25 parts potash feldspar, 20 parts diatom mud, 2 parts boron nitride, 3 parts glass beads With 5 parts of nano zinc oxide. The composite mineralizer is made through the following steps:
1) Crush granite, fluorite, and potash feldspar through 100-300 mesh sieve and remove impurities;
2) Calcining the granite, fluorite and potash feldspar in step 1) to 1150°C and cooling to 25°C within 20 hours;
3) Weigh the processed granite, fluorite, and potash feldspar according to the formula, add diatom mud and boron nitride, and grind into slurry by wet ball milling process, and then pass 400-500 mesh screen;
4) Dry the slurry of step 3) at a drying temperature of 220°C and dry to a moisture content of ≤ 3-5%, then spray glass beads and nano-zinc oxide, and ultrasonically vibrate while spraying. The ultrasonic power is 100kw.
The binding agent is seaweed extract, and the preparation method of the binding agent is as follows:
1) Cleaning: Soak the seaweed raw materials in tap water at 45°C for 2 hours, and then clean them;
2) Crushing and centrifugation: clean the seaweed, crush it in vacuum, add 30 times the volume of the seaweed in ethanol and butanediester solution
Soak and boil, the volume ratio of ethanol and butanediol is 1:1, and then centrifuge to remove the residue to obtain the seaweed clear liquid. The speed of the centrifuge is
4000rpm, centrifugation time is 15min;
3) Nanofiltration: Dilute the seaweed clear liquid with 5 times the volume of pure water, and then use a nanofiltration membrane for dialysis and concentration.
Analyze and concentrate to 0.1 times the volume before dilution to obtain a nanofiltration concentrate, the molecular weight cut-off of the nanofiltration membrane is 600-700Da;
4) Concentration and drying: the nanofiltration concentrate is further vacuum concentrated to a solid content of 40%, and then in a spray dryer spray-dried to obtain a powdered seaweed extract with a water content of 2%.
The manufacturing method of graphene silicon carbide bricks is as follows: the raw materials are weighed according to the above ratio, and the bricks are made by mixing, forming, and molding vibration molding machine. The bricks are baked at 550°C for 20 hours, and then the baked bricks are placed Put it into the impregnating tank for vacuum treatment, the vacuum pressure is 0.05mpa, the pressure is maintained for 40 minutes, then the impregnant is added, and the pressure is maintained for 3 hours. The impregnated bricks are fired at 1200°C for 75 hours. The impregnant is molten petroleum coke, and the amount of impregnant added is that the liquid level exceeds the upper surface of the brick by 45 cm.
Production method 2.:
Using silica as the main raw material, the main raw material of silica is divided into silica particles, silica powder, silica coarse powder and silica fine powder according to the particle size. The graphene silicon carbide brick is composed of the following weight percentages: silica particles 20%, silica powder 30 %, silica coarse powder 20%, silica fine powder 9%, graphene 15%, composite mineralizer 1.5%, binder 3% and nano silicon carbide 1.5%
The weight parts of each component in the raw material composition of the composite mineralizer are: 40 parts granite, 20 parts fluorite, 25 parts potash
Stone, 20 parts of diatom mud, 2 parts of boron nitride, 3 parts of glass beads and 5 parts of nano zinc oxide. The composite mineralizer is made through the following steps:
1) Crush granite, fluorite, and potash feldspar through 100-300 mesh sieve and remove impurities;
2) Calcining the granite, fluorite and potash feldspar in step 1) to 1150°C and cooling to 25°C within 20 hours;
3) Weigh the processed granite, fluorite, and potash feldspar according to the formula, add diatom mud and boron nitride, and grind into slurry by wet ball milling process, and then pass 400-500 mesh screen;
4) Dry the slurry of step 3) at a drying temperature of 250°C and dry to a moisture content of ≤ 3-5%, then spray glass beads and nano-zinc oxide, and ultrasonically vibrate while spraying. The ultrasonic power is 110kw.
The binding agent is seaweed extract, and the preparation method of the binding agent is as follows:
1) Cleaning: Soak the seaweed raw material in tap water at 48℃ for 2.5 hours, and then clean it;
2) Crushing and centrifugation: clean the seaweed, crush it in vacuum, add 30 times the volume of the seaweed in ethanol and butanediester solution
Soak and boil, the volume ratio of ethanol and butanediol is 1:1, and then centrifuge to remove the residue to obtain the seaweed clear liquid. The speed of the centrifuge is
5000rpm, centrifugation time is 18min;
3) Nanofiltration: Dilute the seaweed clear liquid with 7 times the volume of pure water, and then use a nanofiltration membrane for dialysis and concentration.
Analyze and concentrate to 0.2 times the volume before dilution to obtain a nanofiltration concentrate, the molecular weight cut-off of the nanofiltration membrane is 600-700Da;
4) Concentration and drying: the nanofiltration concentrate is further concentrated in vacuum to a solid content of 20%, and then placed in a spray dryer
Spray-dried to obtain a powdered seaweed extract with a moisture content of 2.5%.
The method of making graphene silicon carbide bricks is as follows: each raw material is weighed according to the above ratio, mixed, formed, and made into bricks by a compression molding machine. The bricks are baked at 600°C for 23 hours, and then the baked bricks Put it into the dipping tank and vacuum treatment, the vacuum pressure is 0.06mpa, hold the pressure for 45 minutes, then add the impregnating agent, continue to hold the pressure for 4 hours, the impregnated bricks are roasted at 1250℃, and the holding time is 80 hours. The impregnant is molten petroleum coke, and the amount of impregnant added is such that the liquid level exceeds the upper surface of the brick by 55cm.
Production method 3:
Using silica as the main raw material, the main raw material of silica is divided into silica particles, silica powder, silica coarse powder and silica fine powder according to the particle size. The graphene silicon carbide brick is composed of the following weight percentages: silica particles 30%, silica powder 20 %, silica coarse powder 10%, silica fine powder 13%, graphene 20%, composite mineralizer 2%, binder 2% and nano silicon carbide 3%.
The weight parts of each component in the raw material composition of the composite mineralizer are: 40 parts granite, 20 parts fluorite, 25 parts potash
Stone, 20 parts of diatom mud, 2 parts of boron nitride, 3 parts of glass beads and 5 parts of nano-zinc oxide.
The composite mineralizer is made through the following steps:
1) Crush granite, fluorite, and potash feldspar through 100-300 mesh sieve and remove impurities;
2) Calcining the granite, fluorite and potash feldspar in step 1) to 1150°C and cooling to 25°C within 20 hours;
3) Weigh the processed granite, fluorite, and potash feldspar according to the formula, add diatom mud and boron nitride, and grind into slurry by wet ball milling process, and then pass 400-500 mesh screen;
4) Dry the slurry of step 3) at a drying temperature of 280°C and dry to a moisture content of ≤ 3-5%, then spray glass beads and nano-zinc oxide, and ultrasonically vibrate while spraying, with an ultrasonic power of 120kw.
The binding agent is seaweed extract, and the preparation method of the binding agent is as follows:
1) Cleaning: Soak the seaweed raw materials in tap water at 50°C for 3 hours, and then clean them;
2) Crushing and centrifugation: clean the seaweed, crush it in vacuum, add 30 times the volume of the seaweed in ethanol and butanediester solution
Soak and boil, the volume ratio of ethanol and butanediol is 1:1, and then centrifuge to remove the residue to obtain the seaweed clear liquid. The speed of the centrifuge is
6000rpm, centrifugation time is 20min;
3) Nanofiltration: Dilute the seaweed clear liquid with 10 times the volume of pure water, and then use a nanofiltration membrane for dialysis and concentration.
Dialysis and concentration to 0.2 times the volume before dilution to obtain a nanofiltration concentrate, the molecular weight cut-off of the nanofiltration membrane is 600-700Da;
4) Concentration and drying: the nanofiltration concentrate is further concentrated in vacuum to a solid content of 60%, and then placed in a spray dryer
Spray-dried to obtain a powdered seaweed extract with a water content of 3%.
The method of making graphene silicon carbide bricks is as follows: the raw materials are weighed according to the above ratio, and the bricks are made by mixing, forming, and molding vibration molding machine. The bricks are baked at 650℃ for 25 hours, and then the baked bricks Put it into the impregnation tank and vacuum treatment, the vacuum pressure is 0.08mpa, hold the pressure for 50 minutes, then add the impregnating agent, continue to hold the pressure for 5 hours, the impregnated bricks are roasted at 1285°C, and the holding time is 85 hours. The impregnant is molten petroleum coke, and the amount of impregnant added is 65 cm above the upper surface of the brick.
Comparative Example 1. Commercially available silica bricks.
Production method 1-3 The properties of the silica bricks made in 1-3 and the silica bricks of Comparative Example 1 are shown in Table 1.
|
Item
|
Porosity %
|
Bulk density%
|
Compressive strength Mpa
|
Residual Quartz %
|
Rate of qualified products %
|
|
Method 1
|
14.3
|
2.12
|
66.5
|
0.3
|
96
|
|
Method 2
|
14.7
|
2.08
|
68.1
|
0.7
|
95
|
|
Method 3
|
15.6
|
1.99
|
63.7
|
0.5
|
94
|
|
Example 1
|
22.3
|
1.9
|
45.6
|
2.1
|
80
|
Table 1.
1) The silicon brick of this method has excellent thermal shock resistance, strong resistance to slag and alkali metal corrosion, excellent erosion resistance, excellent heat insulation performance, and good high-temperature volume stability. Graphene silicon carbide bricks;The advantages of this production method :
2) Adding glass beads to the composite mineralizer can be highly uniformly dispersed inside the silica brick, promote sintering, and make the silica brick have a more uniform structure, and improve the strength and thermal shock resistance of the product;
3) The particle size of nano zinc oxide is fine, which can fill fine pores, reduce the porosity of the product, and increase the volume density;
4) Graphene makes the internal contact of the silicon brick closer, thereby reducing the stress caused by expansion during firing, and preventing the product from loosening or cracking;
5) The high strength of graphene ensures the excellent mechanical properties of silica bricks, and at the same time can improve the acid and alkali corrosion resistance of silica bricks;
6) This method is simple, rich in raw materials, and suitable for factory production.
