CN115611614A - Low-heat-conductivity magnesia-hercynite brick for cement kiln and preparation method thereof - Google Patents
Low-heat-conductivity magnesia-hercynite brick for cement kiln and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/03—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on magnesium oxide, calcium oxide or oxide mixtures derived from dolomite
- C04B35/04—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on magnesium oxide, calcium oxide or oxide mixtures derived from dolomite based on magnesium oxide
- C04B35/043—Refractories from grain sized mixtures
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
- C04B2235/30—Constituents and secondary phases not being of a fibrous nature
- C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
- C04B2235/3217—Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
- C04B2235/3222—Aluminates other than alumino-silicates, e.g. spinel (MgAl2O4)
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
- C04B2235/74—Physical characteristics
- C04B2235/77—Density
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- C—CHEMISTRY; METALLURGY
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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
- C04B2235/96—Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
- C04B2235/96—Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B2235/9607—Thermal properties, e.g. thermal expansion coefficient
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
- C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
- C04B2235/96—Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B2235/9669—Resistance against chemicals, e.g. against molten glass or molten salts
Abstract
The invention discloses a low-heat-conductivity magnesia-hercynite brick for a cement kiln and a preparation method thereof, wherein the brick comprises the following raw materials in percentage by weight: 50-60% of high-iron magnesite; 20-25% of sintered magnesia; 5-10% of fused magnesia-alumina spinel; 10-20% of magnesium aluminate spinel hollow sphere; 3-6% of a binding agent, and high-iron magnesite, sintered magnesite, fused magnesia-alumina spinel and magnesia-alumina spinel hollow spheres are creatively introduced, and the additive amount and the granularity of the substances are controlled to generate a synergistic effect, so that the microstructure inside the refractory brick can be effectively improved, the heat conductivity coefficient of the refractory brick is effectively reduced, and the normal-temperature compressive strength, the refractoriness under load and the thermal shock stability of the refractory brick are effectively improved.
Description
Technical Field
The invention belongs to the technical field of refractory materials, and particularly relates to a low-heat-conductivity magnesia-hercynite brick for a cement kiln and a preparation method thereof.
Background
In the process of implementing the invention, the inventor finds that the prior art has at least the following problems:
in the traditional industries such as cement, steel, chemical industry and the like, the pressure of energy conservation and emission reduction is increasing day by day. The rotary cement kiln is used as large-scale thermal equipment used in the cement production process, the refractory material used by the working lining of the rotary cement kiln plays an important role in energy conservation and emission reduction, and the magnesium oxide-based refractory material used in large amount in the conventional rotary cement kiln is high in heat conductivity coefficient, so that excessive heat dissipation of a kiln body is easily caused, and energy conservation and consumption reduction are not facilitated.
Disclosure of Invention
The invention aims to solve the technical problem of providing the low-heat-conductivity magnesia-hercynite brick for the cement kiln, which has the advantages of low heat conductivity coefficient, high refractoriness, good normal-temperature compressive strength, good thermal shock stability, high loaded softening temperature, excellent kiln coating property, structural flexibility and chemical erosion resistance, and can meet the requirements of energy conservation and consumption reduction of refractory materials of the cement kiln, and the preparation method thereof.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the low-heat-conductivity magnesia-hercynite brick for the cement kiln comprises the following raw materials in percentage by weight:
50-60% of high-iron magnesite;
20-25% of sintered magnesia;
5-10% of fused magnesia-alumina spinel;
10-20% of magnesium aluminate spinel hollow sphere;
3-6% of a binding agent.
The particle size of the high-iron magnesite comprises 5-3mm, 3-1mm or 1-0mm, the particle size of the sintered magnesite is less than or equal to 0.088mm, the particle size of the fused magnesia-alumina spinel comprises 3-1mm or 1-0mm, and the particle size of the magnesia-alumina spinel hollow sphere comprises 5-3mm, 3-1mm or 1-0mm.
The proportion of the high-iron magnesite to the sintered magnesite is 11.
The magnesium aluminate spinel hollow sphere has the following different particle size ratios:
the particle size of the electro-magnesium aluminate spinel hollow sphere is 5-3mm, 3-1mm or 1-0mm, and the electro-magnesium aluminate spinel hollow sphere is mixed according to one or more of any proportion. The beneficial influence on the heat-conducting property is limited by simply adding one granularity, and the effect is better when the granularity is added in a gradient manner. When the amounts of both are the same. Meanwhile, the mechanical property of the sample is bound to be adversely affected by adding the hollow spheres, and the influence can be reduced during gradient addition.
High-iron magnesia sand: mgO is more than or equal to 87 percent, fe 2 O 3 ≤6.0％，SiO 2 Less than or equal to 1.5 percent; sintering magnesia: mgO is more than or equal to 97 percent and SiO 2 Less than or equal to 0.8 percent; electric melting magnesia-alumina spinel: mgO:32 to 36 percent; al (Al) 2 O 3 :64-68 percent; hollow magnesium aluminate spinel balls: 28-32% of MgO and Al 2 O 3 ：67-72％。
The preparation method of the low-heat-conductivity magnesia-hercynite brick for the cement kiln comprises the following steps:
1) Weighing high-iron magnesite, sintered magnesite, fused magnesia-alumina spinel hollow spheres and calcium lignosulfonate for later use:
2) Adding the high-iron magnesia and the fused magnesia-alumina spinel into a mixer, mixing for 1-3 minutes, adding the fused magnesia-alumina spinel hollow spheres and the sintered magnesia, mixing for 2-4 minutes, adding the calcium lignosulfonate solution, mixing for 2-5 minutes, and finally blending for 10 minutes;
3) Putting the uniformly mixed raw materials into a hydraulic press for pressing and forming to obtain a green brick for later use;
4) Placing the green bricks in a drying kiln, and drying at 100-200 ℃ for 6-24h to obtain dried green bricks for later use;
5) And (3) placing the dried green brick into a tunnel kiln, sintering at the high temperature of 1400-1500 ℃, and cooling to obtain the finished product.
The magnesium hercynite refractory brick has excellent kiln coating hanging property, chemical erosion resistance and high-temperature mechanical property, and the main production modes of the magnesium hercynite refractory brick comprise the following steps: firstly, high-purity magnesite and presynthesized hercynite are used as raw materials and are prepared by processes of forming, sintering and the like, and secondly, the high-purity magnesite and the presynthesized hercynite are used as raw materials and are prepared by processes of forming, sintering and the like, and compared with the former, the former has the advantage of low raw material cost, and is more beneficial to industrial large-scale production.
The magnesia-alumina spinel hollow sphere is prepared by taking industrial alumina powder and light-burned magnesia powder as raw materials through an electric melting-blowing method, and has the characteristic of no interface abnormal expansion reaction when being combined with alkaline refractory raw materials. The magnesium-aluminum spinel hollow sphere aggregate is introduced into the magnesium-iron-aluminum spinel brick, so that the multi-scale pore structure characteristics of the material can be effectively improved, the heat conductivity coefficient of the material is reduced, and the aim of improving the energy-saving efficiency of the cement kiln is fulfilled.
One of the technical schemes has the advantages or beneficial effects of low heat conductivity coefficient, high refractoriness, good normal-temperature compressive strength, good thermal shock stability, high refractoriness under load, excellent kiln coating property, structural flexibility and chemical erosion resistance, and can meet the requirements of energy conservation and consumption reduction of the cement kiln refractory material.
Drawings
FIG. 1 is a MgO-Al2O3 binary phase diagram of a low thermal conductivity magnesia-hercynite brick for a cement kiln provided in an embodiment of the present invention;
FIG. 2 is a sectional view of a green brick of a magnesia-hercynite brick with low thermal conductivity for a cement kiln;
FIG. 3 is a view of experimental brick slices and cross-sections of a low thermal conductivity magnesia-hercynite brick for a cement kiln;
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
1. Physical and chemical indexes of raw materials
TABLE 1 comparison of the detection data of the magnesium aluminate spinel hollow ball and the fused magnesium aluminate spinel
From the above table, it can be seen that, compared with the fused magnesia-alumina spinel, the magnesia-alumina spinel hollow sphere has a relatively high alumina content and a corresponding low magnesia content, which is influenced by the production process (the higher the alumina, the lower the viscosity of the melted solution, the easier it is to blow into spheres; conversely, the higher the magnesia content, the higher the viscosity of the solution, the harder it is to blow into spheres), we know that theoretically, the alumina content of the pure magnesia-alumina spinel is 71.8%, and the magnesia-alumina spinel hollow sphere is a slightly enriched spinel in chemical composition, and in the magnesium-alumina binary phase diagram (fig. 1), the alumina content is still in the magnesia-alumina spinel solid solution when the alumina content is about 75%, so that the spinel with the alumina content is used in the magnesia refractory material without the abnormality of cracks and the like caused by the expansion of the spinel generated in situ. The content of impurities such as calcium, iron and silicon is controlled at a low level, which is determined by the raw materials for producing the magnesium aluminate spinel. The cubic liter is seen, the hollow spheres are obviously smaller than the fused magnesia-alumina spinel, and the larger the particles are, the smaller the cubic liter is; the vertical lifting weights of different batches of hollow sphere samples are basically consistent under the condition of the same particle size, which indicates that the wall thicknesses of the hollow sphere samples are basically consistent. Generally speaking, the test material index of the batch of magnesium aluminate spinel hollow ball is controlled.
The sintered magnesite is obtained by calcining magnesite, brucite and magnesium hydroxide extracted from seawater or brine, and the high-iron magnesite is a magnesia refractory raw material which is prepared by adding iron ore concentrate or iron scale into magnesite and calcining at high temperature. The magnesium aluminate spinel can be divided into electric melting spinel and sintering spinel according to the synthesis process, and the electric melting is one of the synthesis processes of the magnesium aluminate spinel.
Example one
A preparation method of a low-heat-conduction magnesia-hercynite brick containing magnesium aluminate spinel hollow spheres for a cement kiln comprises the following raw materials in percentage by weight: 55 percent of high-iron magnesite, 25 percent of sintered magnesite, 7 percent of fused magnesia-alumina spinel, 13 percent of magnesia-alumina spinel hollow spheres and 3 percent of calcium lignosulfonate solution. The powder material is sintered magnesia with the granularity of less than 0.088mm, high-iron magnesia with the aggregate granularity of 5-3mm, 3-1mm and 1-0mm, fused magnesia-alumina spinel with the aggregate granularity of 3-1mm and 1-0mm, and magnesia-alumina spinel hollow balls with the aggregate granularity of 5-3mm and 3-1 mm. The beneficial influence on the heat-conducting property caused by only adding one granularity is limited, and the effect caused by the gradient addition is better. When the amounts of both are the same. Meanwhile, the mechanical property of the sample is inevitably influenced by adding the hollow spheres, and the influence can be reduced during gradient addition.
During production, weighing various raw materials according to a ratio for later use, adding the high-iron magnesia and the fused magnesia-alumina spinel into a mixer, mixing for 1-3 minutes, adding the fused magnesia-alumina spinel hollow spheres and the sintered magnesia, mixing for 2-4 minutes, adding the calcium lignosulfonate solution, mixing for 2-5 minutes, and finally blending for 10 minutes; putting the uniformly mixed raw materials into a hydraulic press for pressing and forming to obtain a green brick for later use; placing the green bricks into a drying kiln, and drying for 6-24 hours at 100-200 ℃ to obtain dried green bricks for later use; and (3) placing the dried green brick into a tunnel kiln, sintering at the high temperature of 1400-1500 ℃, and cooling to obtain the finished product.
The performance indexes of the obtained product are as follows: the apparent porosity is 18.9%, the volume density is 2.81g/cm < 3 >, the room-temperature compressive strength is 58MPa, the room-temperature flexural strength is 4.4MPa, and the refractoriness under load is at a temperature
T1.0, 1621 ℃, thermal shock stability (900 ℃, air cooling) is more than or equal to 90 times, thermal conductivity is 1000 ℃, 3.313W (m.K) -1, and the corrosion resistance, the wear resistance and the kiln coating hanging performance are all better.
Example two
The production process is the same as in example 1, except that:
the raw materials comprise the following components in percentage by weight: 55% of high-iron magnesite, 25% of sintered magnesite, 5% of fused magnesia-alumina spinel, 15% of magnesia-alumina spinel hollow spheres and 3% of calcium lignosulfonate solution.
During production, weighing various raw materials according to a ratio for later use, adding the high-iron magnesia and the fused magnesia-alumina spinel into a mixer, mixing for 1-3 minutes, adding the fused magnesia-alumina spinel hollow spheres and the sintered magnesia, mixing for 2-4 minutes, adding the calcium lignosulfonate solution, mixing for 2-5 minutes, and finally blending for 10 minutes; putting the uniformly mixed raw materials into a hydraulic press for pressing and forming to obtain a green brick for later use; placing the green bricks into a drying kiln, and drying for 6-24 hours at 100-200 ℃ to obtain dried green bricks for later use; and (3) placing the dried green bricks into a tunnel kiln, sintering at 1400-1500 ℃ and cooling.
The performance indexes of the obtained product are as follows: the apparent porosity is 20.1%, the volume density is 2.79g/cm < 3 >, the room-temperature compressive strength is 55MPa, the room-temperature flexural strength is 4.2MPa, and the refractoriness under load is at a temperature
T 1.0 1618 deg.C, thermal shock stability (900 deg.C, air cooling) not less than 95 times, thermal conductivity 1000 deg.C 3.220W (m.K) -1 The corrosion resistance, the wear resistance and the kiln coating hanging performance are all better.
EXAMPLE III
The production process was the same as in example 1, except that:
the raw materials comprise the following components in percentage by weight: the raw materials comprise the following components in percentage by weight: 55 percent of high-iron magnesite, 25 percent of sintered magnesite, 3 percent of fused magnesia-alumina spinel, 17 percent of magnesia-alumina spinel hollow spheres and 3 percent of calcium lignosulfonate solution.
During production, weighing various raw materials according to a ratio for later use, adding the high-iron magnesia and the fused magnesia-alumina spinel into a mixer, mixing for 1-3 minutes, adding the fused magnesia-alumina spinel hollow spheres and the sintered magnesia, mixing for 2-4 minutes, adding the calcium lignosulfonate solution, mixing for 2-5 minutes, and finally blending for 10 minutes; putting the uniformly mixed raw materials into a hydraulic press for pressing and forming to obtain a green brick for later use; placing the green bricks in a drying kiln, and drying at 100-200 ℃ for 6-24h to obtain dried green bricks for later use; and (3) placing the dried green brick into a tunnel kiln, sintering at the high temperature of 1400-1500 ℃, and cooling to obtain the finished product.
The performance indexes of the obtained product are as follows: the apparent porosity is 21.8 percent, and the volume density is 2.78g/cm 3 The normal temperature compressive strength is 50MPa, the normal temperature rupture strength is 4.0MPa, the refractoriness under load is 1602 ℃, the thermal shock stability (900 ℃, air cooling) is more than or equal to 100 times, and the thermal conductivity is 3.108W (m.K) -1 Its advantages are high resistance to corrosion, abrasion and hanging kiln skin.
Example four
The production process was the same as in example 1, except that:
the raw materials comprise: 55% of high-iron magnesite, 25% of sintered magnesite, 5% of fused magnesia-alumina spinel, 15% of magnesia-alumina spinel hollow spheres and 3% of calcium lignosulfonate solution. High-iron magnesia with aggregate granularity of 5-3mm, 3-1mm and 1-0mm, fused magnesia-alumina spinel with aggregate granularity of 3-1mm, and magnesia-alumina spinel hollow balls with aggregate granularity of 5-3mm, 3-1mm and 1-0mm.
During production, weighing various raw materials according to a ratio for later use, adding the high-iron magnesia and the fused magnesia-alumina spinel into a mixer, mixing for 1-3 minutes, adding the fused magnesia-alumina spinel hollow spheres and the sintered magnesia, mixing for 2-4 minutes, adding the calcium lignosulfonate solution, mixing for 2-5 minutes, and finally blending for 10 minutes; putting the uniformly mixed raw materials into a hydraulic press for pressing and forming to obtain a green brick for later use; placing the green bricks in a drying kiln, and drying at 100-200 ℃ for 6-24h to obtain dried green bricks for later use; and (3) placing the dried green brick into a tunnel kiln, sintering at the high temperature of 1400-1500 ℃, and cooling to obtain the finished product.
The performance indexes of the obtained product are as follows: apparent porosity of 19.0%, volume density of 2.81g/cm 3 Room temperature compressive strength of 58MPa, room temperature flexural strength of 4.3MPa, softening temperature under load T 1.0 1622 deg.C, thermal shock stability (900 deg.C, air cooling) not less than 95 times, thermal conductivity 1000 deg.C 3.183W (m.K) -1 Its advantages are high resistance to corrosion, abrasion and hanging kiln skin.
EXAMPLE five
The production process was the same as in example 1, except that:
the raw materials comprise: 55 percent of high-iron magnesia, 25 percent of sintered magnesia, 5 percent of fused magnesia-alumina spinel, 15 percent of magnesia-alumina spinel hollow spheres and 3 percent of calcium lignosulfonate solution. According to the weight percentage, the aggregate granularity is 5-3mm, 3-1mm, 1-0mm of high-iron magnesia, 3-1mm of electric melting magnesia-alumina spinel, 5-3mm, 3-1mm, 1-0mm of magnesia-alumina spinel hollow sphere.
During production, weighing various raw materials according to a ratio for later use, adding the high-iron magnesia and the fused magnesia-alumina spinel into a mixer, mixing for 1-3 minutes, adding the fused magnesia-alumina spinel hollow spheres and the sintered magnesia, mixing for 2-4 minutes, adding the calcium lignosulfonate solution, mixing for 2-5 minutes, and finally blending for 10 minutes; putting the uniformly mixed raw materials into a hydraulic press for pressing and forming to obtain a green brick for later use; placing the green bricks into a drying kiln, and drying for 6-24 hours at 100-200 ℃ to obtain dried green bricks for later use; and (3) placing the dried green brick into a tunnel kiln, sintering at the high temperature of 1400-1500 ℃, and cooling to obtain the finished product.
The performance indexes of the obtained product are as follows: the apparent porosity is 18.7 percent, and the volume density is 2.81g/cm 3 Normal temperature compressive strength of 61MPa, normal temperature flexural strength of 4.3MPa, softening temperature under load T 1.0 1625 deg.C, thermal shock stability (900 deg.C, air cooling) not less than 95 times, thermal conductivity 1000 deg.C 3.111W (m.K) -1 The corrosion resistance, the wear resistance and the kiln coating hanging performance are all better.
On-site bench test is based on MI1 formula without hollow sphere, henan and finished magnesium aluminate spinel hollow sphere samples are selected, and the pressing force is controlled to be 1.5T/cm 2 . The addition amount of the magnesia-alumina spinel is controlled to be 20% in the experiment, the addition amounts of the magnesia-alumina spinel hollow spheres are respectively 13%, 15% and 17%, and the specific formula is as follows:
TABLE 2 Experimental formulation
The magnesium aluminate spinel hollow sphere with one grain size is added into the sample only, so that the beneficial influence on the heat-conducting property of the sample is limited, and the effect generated when multiple grain sizes are added in a gradient manner is better. Meanwhile, the addition of the hollow spheres inevitably has adverse effect on the normal-temperature mechanical property of the sample, and the influence can be reduced when various particle size gradients are added.
And detecting data of the mixture and the green bricks.
TABLE 3 semi-finished product inspection data
As can be seen from the above table, the particle size distribution of the experimental material is stably controlled; from the appearance and the section (figure 2) of the green brick, the surface is smooth, the structure of the hollow ball can be well preserved and is uniformly distributed, and the situation of fragmentation does not occur.
Kiln-out experimental brick detection data
Taking the experimental brick out of the kiln, sampling and carrying out conventional performance detection, wherein specific detection data are as follows.
TABLE 4 detection data of finished brick
As can be seen from the table above, the experimental brick has good performance indexes. In examples 1,2 and 3, the added spinel hollow spheres have the same particle size, but the difference is that the addition amount is such that the mechanical properties of the test brick are obviously reduced although the heat conductivity of the test brick is obviously improved with the addition amount; in examples 4 and 5, the thermal conductivity was improved by adjusting the particle size of the added hollow spheres, while the mechanical properties were improved. The brick is good in integrity, the hollow spheres are uniformly distributed, and no obvious broken spheres exist in the view of the slicing and fracture surfaces (figure 3) of the experimental brick taken out of the kiln.
The heat conductivity coefficient test method is a parallel hot wire method
TABLE 5 thermal conductivity of the test bricks
| Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | |
| Coefficient of thermal conductivity | 3.313 | 3.220 | 3.108 | 3.183 | 3.111 |
From the above, the conventional performance index of the on-site small-test brick of the magnesium aluminate spinel hollow sphere is good and basically reaches the expectation.
By adopting the scheme, the high-iron magnesite, the sintered magnesite, the fused magnesia-alumina spinel and the magnesia-alumina spinel hollow spheres are creatively introduced, the synergistic effect can be generated by controlling the addition amount and the granularity of the substances, the microstructure structure in the refractory brick can be effectively improved, the heat conductivity coefficient of the refractory brick is effectively reduced, and the normal-temperature compressive strength, the refractoriness under load and the thermal shock stability of the refractory brick are also effectively improved. The product has the advantages of low heat conductivity coefficient, high refractoriness, good normal-temperature compressive strength, good thermal shock stability, high refractoriness under load, excellent kiln coating property, structural flexibility and chemical erosion resistance, and can meet the requirements of energy conservation and consumption reduction of the cement kiln refractory material.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (8)
1. The low-heat-conductivity magnesia-hercynite brick for the cement kiln is characterized by comprising the following raw materials in percentage by weight:
50-60% of high-iron magnesite;
20-25% of sintered magnesia;
5-10% of fused magnesia-alumina spinel;
10-20% of magnesium aluminate spinel hollow sphere;
3-6% of a binding agent.
2. The low thermal conductivity magnesia-hercynite brick for cement kilns as claimed in claim 1, wherein the grain size of the high-iron magnesite is 5-3mm, 3-1mm or 1-0mm, the grain size of the sintered magnesite is less than or equal to 0.088mm, the grain size of the electric melting magnesia-hercynite is 3-1mm or 1-0mm, and the grain size of the magnesia-hercynite hollow sphere is 5-3mm, 3-1mm or 1-0mm.
3. The low thermal conductivity magnesia-hercynite brick for cement kilns as recited in claim 2, wherein the ratio of high-iron magnesite sand to sintered magnesite sand is 11.
4. The low thermal conductivity magnesia-hercynite brick for cement kilns as claimed in claim 3, wherein the weight ratio of high-iron magnesite: mgO is more than or equal to 87 percent, fe 2 O 3 ≤6.0％，SiO 2 Less than or equal to 1.5 percent; sintering magnesia: mgO is more than or equal to 97 percent and SiO 2 Less than or equal to 0.8 percent; electric melting magnesia-alumina spinel: mgO:32 to 36 percent; al (Al) 2 O 3 :64-68 percent; hollow magnesium aluminate spinel balls: 28-32% of MgO and Al 2 O 3 ：67-72％。
5. The low-thermal-conductivity magnesia-hercynite brick for cement kilns as claimed in claim 2, wherein the proportions of different particle sizes of the magnesia-hercynite hollow spheres are as follows:
6. the low thermal conductivity magnesia-hercynite brick for cement kilns as claimed in claim 5, characterized in that said binder is calcium lignosulfonate.
7. The low thermal conductivity magnesia-hercynite brick for cement kilns as claimed in claim 1, wherein the particle size of said electro-magnesia-hercynite hollow sphere is 5-3mm, 3-1mm or 1-0mm, and is mixed according to one or more of any proportion.
8. The preparation method of the magnesia-hercynite brick with low thermal conductivity for the cement kiln as claimed in any one of claims 1 to 6, characterized by comprising the following steps:
1) Weighing high-iron magnesite, sintered magnesite, fused magnesia-alumina spinel hollow spheres and calcium lignosulfonate for later use:
2) Adding the high-iron magnesia and the fused magnesia-alumina spinel into a mixer, mixing for 1-3 minutes, adding the fused magnesia-alumina spinel hollow spheres and the sintered magnesia, mixing for 2-4 minutes, adding the calcium lignosulfonate solution, mixing for 2-5 minutes, and finally blending for 10 minutes;
3) Putting the uniformly mixed raw materials into a hydraulic press for pressing and forming to obtain a green brick for later use;
4) Placing the green bricks into a drying kiln, and drying for 6-24 hours at 100-200 ℃ to obtain dried green bricks for later use;
5) And (3) placing the dried green bricks into a tunnel kiln, sintering at 1400-1500 ℃ and cooling.
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