Technical field:
The invention belongs to the technical field of refractory materials, and specifically relates to a method for preparing mullite-anorthite lightweight refractories using waste
mullite-corundum bricks. The invention is suitable for the regeneration of discarded mullite-corundum refractories use.
Background technique:
Mullite-corundum refractories are widely used as kiln furniture, such as saggers, sheds, bricks, ceramic rollers, ferrite materials and electronic insulating ceramics for firing kiln linings, push plates, and bearings. Burning slabs, etc.; the market's consumption of mullite-corundum bricks is increasing year by year; correspondingly, mullite-corundum bricks are cracked, broken, adhered and deformed during actual use, resulting in a large number of discarded mullite-corundum bricks In addition to a small amount of these waste bricks are recycled and reused, a large number of them are discarded and stored. Because the surface of the used bricks contains metal oxides such as Zn, Mn, Ni, Cd, etc., metal ions are leached out by rain washing and the environment is polluted. On the other hand, there is very little natural mullite in nature, and it needs artificial high temperature synthesis. Therefore, after use, mullite-corundum bricks are disposed of and recycled and reused, which can save resources and reduce environmental pollution.
There have been reports on the production of corundum and mullite by recycling waste
refractory materials. Chinese patent CN201310478688.X discloses crushing waste high-alumina bricks into fine powder, after pulping, drying and granulating, and compression molding; the blank obtained by compression molding is sintered at 1570-1620°C, and the temperature is kept for 8-12 hours to synthesize corundum. Chinese patent CN201310478542.5 discloses that waste clay bricks are crushed into fine powder, which undergoes pulping, drying and granulation and compression molding; sintering the blanks obtained by compression molding at 1530 to 1560°C, and heat preservation for 8 to 12 hours to prepare synthetic mullite. There are also reports on mullite-anorthite composite materials. Chinese patent CN201110433179.6 discloses a method for preparing anorthite-mullite composite high-temperature resistant materials using limestone, quartz powder and γ-alumina as raw materials.
Summary of the invention:
In view of the technical problems existing in the comprehensive utilization of the existing waste mullite-corundum bricks, the present invention provides a method for preparing lightweight refractory materials by using the waste mullite-corundum bricks.
The specific steps of a method for preparing lightweight refractories using waste mullite-corundum bricks provided by the present invention are as follows:
(1) The selection of discarded mullite-corundum bricks uses a combination of artificial hammer percussion and mechanical cutting with diamond tools to remove the reaction layer on the surface of the discarded mullite-corundum bricks.
(2) Put the waste mullite-corundum bricks after removing the reaction layer into a jaw crusher for crushing, and use a magnetic separator to remove the waste mullite-corundum bricks by magnetic separation. -The iron-containing impurities contained in the corundum bricks are used to obtain waste mullite-corundum brick particles.
(3) Put the waste mullite-corundum brick particles obtained in step (2) into a roller machine for crushing, and sieving to obtain waste mullite-corundum brick particles with a particle size of less than 1mm.
(4) Take a sample of the obtained fine particles less than 1mm, and use X-ray fluorescence spectrometer to determine the chemical composition: Al 2O 3, SiO 2 and Fe 2 O 3.
(5) Preparation of mixture:
Mixing the waste mullite-corundum brick particles with a particle size of less than 1mm and calcium carbonate and a pore former obtained in step (3) to obtain a mixture, and the waste mullite-corundum brick particles with a particle size of less than 1mm The mass ratio with calcium carbonate and pore former is: (10-15):1:5, and the pore former is starch.
(6) Preparation of slurry:
The mixture obtained in step (5) is mixed with the forming agent and then put into a ball mill tank, and then ball milled for 5-10 hours using a planetary ball mill to obtain a slurry. The rotation speed of the planetary ball mill is 550 rpm.
The forming agent is an aqueous solution of a mixture of organic monomer acrylamide (AM) and N,N-methylene bispropionamide (MBAM), and the organic monomer acrylamide and N,N-methylene bispropionamide The mass ratio of the organic monomer acrylamide to N,N-methylene bispropionamide in the mixture is 10:1, and the mixture of the organic monomer acrylamide and N,N-methylene bispropionamide is prepared with water For a solution with a mass fraction of 5%, the volume ratio of the forming agent to the mixture is 3:10.
(7) Add an appropriate amount of initiator ammonium persulfate and catalyst tetramethylethylenediamine to the slurry obtained in step (6), stir it evenly and inject it into the steel mold, release the mold after solidification, and demold the blank The body is dehydrated in an ethanol aqueous solution with a volume fraction of 80% for 5 hours. After dehydration, the body is placed in a drying box and dried at 110°C for 24 hours.
(8) Put the dried green body in a high-temperature furnace and heat it at 1300-1500°C for 5-10 hours to obtain the light-weight refractory material.
The main components of the waste mullite-corundum refractory material in the present invention are Al 2O 3 and SiO 2, which is a multi-phase material, that is, Al 2O 3 reacts with SiO 2 at high temperature to form a mullite phase (3Al 2O 3 +2SiO 2=3Al 2O 3·2SiO2), Al 2O 3 is still surplus and precipitates as corundum. For this reason, waste mullite-corundum bricks are recycled and disposed of, and CaO is added to it and pores are made. It retains the main crystalline phase of mullite, and at the same time makes CaO react with SiO 2 and excess Al 2O 3 to generate anorthite at high temperature, thereby preparing a lightweight refractory material: mullite-anorthite material. The method of the invention has the advantages of low preparation cost, simple process and reduced environmental pollution, and the prepared light refractory material can be widely used as a heat preservation and heat insulation material.
Detailed ways:
Example 1: Recycling waste mullite-corundum push slab bricks from the magnetic material industry. After manual sorting, a combination of manual hammer percussion and diamond tool mechanical cutting is used to remove the surface of the waste bricks and the reaction layer of magnetic materials; after removal The remaining bricks are thrown into the jaw crusher for crushing, and the crushed materials are magnetically separated by a magnetic separator to remove the iron-containing impurities entrained; the remaining brick particles obtained after the magnetic separation are thrown into the roller machine for fine crushing and screening Separate the fine particles with a particle size of less than 1mm, and return the particles with a particle size of 1mm or more to the roller machine to continue crushing; sample the obtained fine particles with a particle size of less than 1mm for chemical analysis, using X-ray fluorescence spectrometer Determine the chemical composition; the specific composition is Al 2O 388.20%, SiO 28.48%, Fe 2O 30.83%. The obtained fine particles of waste bricks with a particle size of less than 1 mm, calcium carbonate and starch are blended according to a mass ratio of 15:1:5 to obtain a mixture. The forming agent is an aqueous solution of organic monomers acrylamide (AM) and N,N-methylene bispropionamide (MBAM); the mass ratio of AM and MBAM is 10:1, mixed with water to prepare a solution with a mass fraction of 5wt% ; Mix the mixture and the forming agent according to the volume ratio of 10:3 and put them into the ball mill tank, use a planetary ball mill for 10 hours, at a speed of 550 rpm; add an appropriate amount of initiator ammonium persulfate and catalyst to the slurry obtained by ball milling Tetramethylethylenediamine, stir evenly, inject into the steel mold, solidify and demould; after demolding, the green body is placed in an ethanol aqueous solution with a volume fraction of 80% for dehydration for 5 hours; the sample is placed after dehydration Dry in a drying box at 110°C for 24h; place the dried body in a high-temperature furnace and fire at 1400°C to obtain a product. The sintering time is 5h, and the apparent porosity of the product is 50.5% and the bulk density is 1.23. g/cm 3, Figure 1 shows the X-ray diffraction pattern of the product. After analysis, mullite and corundum are the main crystalline phases, and anorthite is the secondary crystalline phase.
Example 2: Recycling waste mullite-corundum saggers from the ceramic industry. After manual sorting, a combination of manual hammer percussion and diamond tool mechanical cutting is used to remove the surface of the waste bricks and the ceramic reaction layer; the removed saggers Put into the jaw crusher for crushing, the crushed materials are magnetically separated by a magnetic separator to remove the iron-containing impurities; the residual brick particles obtained after magnetic separation are put into the roller machine for fine crushing, and the particles are obtained by sieving. Fine particles smaller than 1mm in diameter, and particles larger than or equal to 1mm in size are returned to the roller machine to continue crushing; sample the obtained fine particles smaller than 1mm in diameter, and conduct chemical analysis. Use X-ray fluorescence spectrometer to determine the content Chemical composition; specific composition is Al 2O 378.65%, SiO 220.86%, Fe 2O 30.57%. The obtained fine particles of waste bricks with a particle size of less than 1 mm, calcium carbonate and starch are blended according to a mass ratio of 10:1:5 to obtain a mixture. The forming agent is an aqueous solution of organic monomers acrylamide (AM) and N,N-methylenebispropionamide (MBAM); the mass ratio of AM and MBAM is 10:1, mixed with water to prepare a solution with a mass fraction of 5wt% ; Mix the mixture and the forming agent according to the volume ratio of 10:3 and put them into a ball mill tank, use a planetary ball mill for ball milling for 5 hours, at a speed of 550 rpm; add an appropriate amount of initiator ammonium persulfate and catalyst to the slurry obtained by ball milling Tetramethylethylenediamine, stir evenly, pour into the steel mold, solidify and demould; after demolding, the green body is placed in an ethanol aqueous solution with a volume fraction of 80% for dehydration for 5 hours; the sample is placed after dehydration Dry in a drying box at 110°C for 24h; place the dried body in a high-temperature furnace and fire at 1300°C to obtain a product. The firing and holding time is 10h. The product has a apparent porosity of 53.9% and a bulk density of 1.12 g/cm 3, Figure 2 shows the X-ray diffraction pattern of the product. After analysis, mullite is the main crystalline phase, and anorthite and corundum are the secondary crystalline phase.
