Composite binder for ramming material, chrome corundum ramming material and preparation method thereof

Abstract

The present invention relates to a composite binder for ramming material, a chrome corundum ramming material and a preparation method thereof. The composite binder is composed of a base material, cationic starch, oxalic acid and alumina short fibers; the base material is composed of the following raw materials in parts by weight: 3-5 parts of Suzhou soil, 3-5 parts of alumina cement, and active SiO 2 3-5 parts of micro powder, 2-3 parts of ceramic ultrafine powder, 4-6 parts of magnesia fine powder, 1.5-2 parts of polyaluminium ferric chloride, Cr 2 O 3 The invention has the advantages that the obtained composite binder can effectively reduce the sintering temperature of the material, improve the sintering strength and thermal shock stability of the material; the obtained composite binder is applied to the chrome corundum ramming material, and can form Cr-rich chromium on the surface of the fused high chromium sand. 2 O 3 The aggregate structure is improved, and the high chromium sand aggregate is strongly connected with the matrix to form a chrome corundum ramming material with low chromium content and high thermal shock stability.

Description

Technical Field

[0001] The invention relates to the technical field of amorphous refractory materials, in particular to a composite binder for ramming material, a chrome corundum ramming material and a preparation method thereof. Background Art

[0002] The roasting process of large-scale pellet belt roasting machine includes drying, preheating, roasting, soaking, cooling and other processes, and each process is completed on the main equipment of the belt roasting machine. The key equipment of large-scale pellet belt roasting machine includes roasting system, hot air system and combustion system. The combustion system of this equipment uses heavy oil, natural gas and high calorific value coal gas. The temperature in the combustion chamber is high, which can reach 1500℃. The air flow in the combustion chamber is large and the temperature fluctuates frequently. The requirements for refractory performance are high. The refractory bricks used in the combustion chamber are required to have good thermal shock stability, wear resistance and high strength to meet the specific working conditions of the combustion chamber, ensure the long service life of the refractory materials, and ensure the safe and stable operation of the large-scale pellet belt roasting machine.

[0003] At present, the refractory bricks of the combustion chamber mainly use corundum-mullite composite bricks. The composite bricks use corundum and mullite as the main raw materials and need to be fired at a temperature of 1650-1750℃. When used in the combustion chamber of the belt sintering machine, cracking and peeling occur during use, which has a great impact on the service life of the combustion chamber and becomes a key factor restricting the safe and stable operation of large-scale pellet belt roasting. In order to ensure the service life of the combustion chamber, chrome corundum castables or chrome corundum ramming materials are often used at the bottom of the combustion chamber to protect the corundum-mullite composite bricks. The chrome corundum castables or ramming materials have a chromium oxide content of more than 30%, which is costly, has poor thermal shock stability, is easy to crack, and has a high hexavalent chromium content in the residual bricks, which will pollute the water body. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a composite binder for ramming material, a chrome corundum ramming material and a preparation method thereof. The obtained composite binder can effectively reduce the sintering temperature of the material and improve the sintering strength and thermal shock stability of the material; the obtained composite binder is applied to the chrome corundum ramming material to form a Cr-rich sintered material on the surface of the fused high chrome sand. 2 O 3 The aggregate structure is formed by strongly connecting the high chromium sand aggregate with the matrix to form a chrome corundum ramming mass with low chromium content; the chrome corundum ramming mass has the advantages of high high temperature strength, erosion resistance, low thermal expansion coefficient, high thermal shock stability and no cracking, and can meet the working conditions of the combustion chamber of a large-scale pellet belt roaster, effectively protect the corundum-mullite composite bricks in the combustion chamber, extend the service life of the refractory lining of the combustion chamber, and reduce the pollution of the residual refractory lining to the water body.

[0005] The present invention is realized by the following technical scheme: providing a composite binder for ramming material, the composite binder is composed of base material, cationic starch, oxalic acid and alumina short fibers; the base material is composed of the following raw materials in parts by weight: 3-5 parts of Suzhou soil, 3-5 parts of alumina cement, active SiO 2 3-5 parts of micro powder, 2-3 parts of ceramic ultrafine powder, 4-6 parts of magnesia fine powder, 1.5-2 parts of polyaluminium ferric chloride, Cr 2 O 3 0.5-1 part of micro powder, 0.5-1 part of calcium chromate; the cationic starch accounts for 0.5%-1wt% of the total weight of the base material; the oxalic acid accounts for 0.5%-1wt% of the total weight of the base material; the alumina short fibers account for 2%-2.5wt% of the total weight of the base material.

[0006] Through the above technical scheme, the traditional ramming material binding often uses phosphoric acid or aluminum dihydrogen phosphate as a binder. Phosphoric acid or aluminum dihydrogen phosphate as a binder has a certain degree of corrosiveness, which is harmful to the human body and the mold, and is not convenient for construction. Before the ramming construction, the ramming material with the binder needs to be trapped. Without the trapping, the ramming material will cause technical problems such as bulging and cracking. Generally, the trapping time is not less than 16 hours, and the material needs to be covered during trapping to prevent evaporation. The ramming material with phosphoric acid or aluminum dihydrogen phosphate as a binder has poor plasticity during construction, and a plasticizer needs to be added to ensure good construction performance. The ramming material with phosphoric acid or aluminum dihydrogen phosphate as a binder has low medium and low temperature strength and poor thermal shock stability. The binder has an adverse effect on high temperature resistance and has poor high temperature resistance.

[0007] The binder of the present invention adds cationic starch at a weight percentage of 0.5% to 1% of the base material, which promotes the uniform distribution of active SiO2 micropowder, ceramic ultrafine powder and Suzhou soil in the composite binder and forms a coupled state, so that the sintering temperature of the ramming material added with the composite binder is reduced to 1050°C, so that the low-temperature strength, medium-temperature strength and high-temperature strength are all higher than 35MPa. With the increase of temperature, the strength increases, and the strength in the high-temperature stage increases rapidly. The composite binder effectively improves the thermal shock stability of the ramming material. Oxalic acid is added at a weight percentage of 0.5% to 1% of the base raw material to improve the coagulation performance of the composite binder, and the ramming material has good construction performance.

[0008] In addition, at room temperature, polyaluminium ferric chloride enhances the plasticity of the composite binder and improves the construction performance of the material. Good construction performance enables the material to form a good organizational structure. Under high-temperature use conditions, polyaluminium ferric chloride reacts with magnesia fine powder and ceramic ultrafine powder in the composite binder to produce magnesia-aluminium spinel and magnesia-iron spinel that are evenly distributed in the matrix. The spinel whiskers are interspersed between the material matrix and aggregate to form a tightening effect, which effectively improves the thermal shock stability of the product.

[0009] Calcium chromate introduced into the composite binder decomposes in situ to generate Cr at a temperature higher than 1350°C during use. 2 O 3 Penetrates into the surface of fused high chromium sand (particle size 1-0 mm) to form a surface rich in Cr 2 O 3 The content of aggregate structure is improved, and the high chromium sand aggregate is strongly connected to the matrix. The test strength (after sintering at 1550℃×3h) is increased by more than 8.5MPa compared with that without adding calcium chromate, and the thermal shock stability is increased by more than 5 times compared with that without adding calcium chromate. In addition, while ensuring good high temperature strength and thermal vibration stability, the Cr content in the ramming material is reduced. 2 O 3 content.

[0010] Furthermore, the length L of the alumina short fibers is ≤25 mm.

[0011] Furthermore, the length-to-weight ratio of the alumina short fibers is L (21.2 mm to 24.5 mm): L (10.0 mm to 21.2 mm): L (5.0 mm to 10.0 mm) = 1:2:2.5.

[0012] Through the above technical scheme, short alumina fibers are introduced into the composite binder and interspersed in the ramming material matrix to improve the thermal shock stability. The short fibers are mixed and added in an orderly manner with a weight ratio of long (24.5mm~21.2mm): medium (21.2mm~10.0mm): short (10.0mm~5.0mm) = 1:2:2.5, which can significantly improve 5% compared with disordered addition.

[0013] Furthermore, preferably, the particle size of the composite binder is ≤320 mesh.

[0014] Through the above technical solution, the composite binder is co-grinded to a particle size less than 320 mesh, which reduces the sintering temperature of the binder and increases the sintering strength at 1000°C by more than 5MPa.

[0015] A method for preparing the composite binder for ramming material is also provided, characterized in that it comprises the following steps:

[0016] Step S1, premixing: weighing the base material according to the above ratio and grinding it in a ball mill to obtain a premix;

[0017] Step S2, mixing: add cationic starch and oxalic acid to the premix of step S1 and grind and mix them for 2-3 minutes, then add alumina short fibers and grind them for 1-2 minutes to obtain a composite binder.

[0018] Through the above technical scheme, by grinding the composite binder in a ball mill, the particle size of the basic raw material can be guaranteed to be below 320 meshes, the uniformity of the composite binder is good, the surface properties and activity of the micropowder constituting the composite binder are changed, the sintering temperature of the binder is reduced by 100°C, and the matrix can be sintered at 1000°C, which improves the sintering strength and thermal shock stability of the material, and at the same time changes the hydration characteristics of alumina cement. The ramming material is made of a low amount of alumina cement, and after 24 hours of room temperature curing, the strength reaches more than 30Mpa.

[0019] Furthermore, in step S1, the ball milling time is 5 to 8 minutes.

[0020] Through the above technical scheme, a ball mill is used for co-grinding. The basic raw materials of the composite binder are first co-grinded for 5-8 minutes to change the surface morphology and activity of the basic raw materials. Different components of the basic raw materials adsorb each other to form a homogenized fitting structure. Cationic starch and oxalic acid are then added and co-grinded for 2-3 minutes. Cationic starch is added to promote the uniform distribution of active SiO2 micropowder, ceramic ultrafine powder, and Suzhou soil. Oxalic acid is added to improve the coagulation and construction properties of the basic raw materials. Alumina short fibers are then added thereto for co-grinding so that the short fibers are evenly distributed in the basic raw materials to improve their thermal shock stability.

[0021] A chrome corundum ramming material is provided, which comprises the following raw materials in weight percentage: 10% to 15% plate-shaped corundum aggregate, 25% to 30% white corundum aggregate, 20% to 25% brown corundum aggregate, 3% to 5% fused high chrome sand, and α-Al 2 O 3 2% to 3% of micro powder, 30% to 35% of composite binder, and 2% to 3% of added water; the composite binder is made from the composite binder used for ramming material.

[0022] Furthermore, the particle size of the plate-shaped corundum aggregate is 15.5-18.5 mm, the particle size of the white corundum aggregate is 5-8 mm and 3-5 mm, the particle size of the brown corundum aggregate is 1-3 mm, and the particle size of the fused high chrome sand is 0-1 mm.

[0023] Through the above technical scheme, the ramming material is based on the four-level gradation of (8-5mm), (5-3mm), (3-1mm), and (1-0mm), with white corundum as large particles, brown corundum as medium particles, and electro-fused high chrome sand as small particles, and a specific amount (10% to 15%) of plate-shaped corundum aggregate (particle size 18.5-15.5mm) of specific particle size is added to form an island distribution in the material, effectively blocking the expansion of stress cracks caused by drastic temperature changes during the use of the material, and further improving the thermal shock stability of the ramming material. Plate-shaped corundum aggregate is used as super particles, white corundum is used as large particles, brown corundum is used as medium particles, and high chrome sand is used as small particles. They are mixed and interspersed with each other according to weight and filled to form an ultra-stable, discontinuous particle support structure, and the characteristics of the thermal expansion coefficients of plate-shaped corundum, white corundum, and brown corundum are close and different, which improves the strength and thermal shock stability of the material and reduces the thermal expansion coefficient of the chrome corundum ramming material.

[0024] Calcium chromate introduced into the composite binder decomposes in situ to generate Cr at a temperature higher than 1350°C during use. 2 O 3 Penetrates into the surface of fused high chromium sand (particle size 1-0 mm) to form a surface rich in Cr 2 O 3 The content of aggregate structure is improved, and the high chromium sand aggregate is strongly connected to the matrix. The test strength (after sintering at 1550℃×3h) is increased by more than 8.5MPa compared with that without adding calcium chromate, and the thermal shock stability is increased by more than 5 times compared with that without adding calcium chromate. In addition, while ensuring good high temperature strength and thermal vibration stability, the Cr content in the ramming material is reduced. 2 O 3 content.

[0025] The composite binder is added in an optimal amount (30% to 35%), and the ramming material has good plastic ramming construction performance, easy sintering, and good matrix thermal shock stability. The strength and thermal vibration stability are significantly improved when the binder is added in an amount of (30% to 35%). When the addition amount exceeds 35% or is less than 30%, the strength and thermal vibration stability show a significant downward trend. The composite binder is added in an optimal amount (30% to 35%) and is used for the ramming material of the combustion chamber of a large-scale pellet belt roasting machine. The ramming material has high strength, good construction performance, high thermal shock stability, and reduces the Cr of the ramming material. 2 O 3 The content meets the working conditions of the combustion chamber, and the erosion resistance, cracking resistance and thermal vibration stability are significantly improved.

[0026] Finally, a method for preparing the above-mentioned chrome corundum ramming material is provided, comprising the following steps:

[0027] 1) According to the above ratio, plate-shaped corundum aggregate, white corundum aggregate, brown corundum aggregate, and fused high chrome sand are weighed and added in order, and dry-mixed for 2-3 minutes using a mixer to obtain a first mixture;

[0028] 2) Add α-Al to the first mixture in step 1) 2 O 3 The powder is dry-mixed for 1-2 minutes to obtain a second mixture;

[0029] 3) Add the composite binder to the second mixture of step 2) and dry mix for 3-5 minutes to obtain chrome corundum ramming material.

[0030] The beneficial effects of the present invention are as follows: the obtained ramming material has high high temperature strength, erosion resistance, low thermal expansion coefficient, high thermal shock stability, no cracking, good construction performance, meets the working conditions of the combustion chamber of a large-scale pellet belt roasting machine, effectively protects the corundum-mullite composite bricks in the combustion chamber, prolongs the service life of the refractory lining of the combustion chamber, and the service life can reach more than 5 years, and reduces Cr 2 O 3 The content of refractory materials reduces the pollution of water bodies caused by residual lining of refractory materials and reduces the cost of materials. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the invention to clearly and completely describe the technical solutions in the embodiments of the invention. Obviously, the described embodiments are only part of the embodiments of the invention, not all of the embodiments. Based on the embodiments of the invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the invention.

[0032] Example 1

[0033] A chrome corundum ramming material, the ramming material comprises the following raw materials in weight percentage: 15% of plate-shaped corundum aggregate with a particle size of (15.5-18.5mm), 15% of white corundum aggregate with a particle size of (5-8mm), 15% of white corundum aggregate with a particle size of (3-5mm), 20% of brown corundum aggregate with a particle size of (1-3mm), 3% of fused high chrome sand with a particle size of (0-1mm), α-Al 2 O 3 Micro powder (≤240 mesh) 2%, composite binder 30%; the required amount of added water accounts for 2wt% of the total weight of the ramming material;

[0034] The composite binder is composed of base material, cationic starch, oxalic acid and alumina short fibers; the base material is composed of the following raw materials in parts by weight: 3 parts of Suzhou clay, 3 parts of alumina cement, 3 parts of active SiO 2 3 parts of micro powder, 2 parts of ceramic ultrafine powder, 4 parts of magnesia fine powder, 1.5 parts of polyaluminium ferric chloride, Cr 2 O 30.5 parts of micro powder, 0.5 parts of calcium chromate; and cationic starch accounts for 0.5wt% of the total weight of the base material, oxalic acid accounts for 0.5wt% of the total weight of the base material, and alumina short fibers account for 2wt% of the total weight of the base material;

[0035] The preparation method of the obtained composite binder comprises the following steps:

[0036] Step S1, premixing: weighing the base material according to the above ratio and grinding it in a ball mill to obtain a premix;

[0037] Step S2, mixing; add cationic starch and oxalic acid to the premix of step S1 and grind and mix them for 2-3 minutes, then add alumina short fibers and grind them for 1-2 minutes, and grind the particles to a size of 320 mesh to obtain a composite binder.

[0038] Preferably, in step S2, the alumina short fibers are randomly added in a mixed manner with a length-to-weight ratio of long (21.2 mm to 24.5 mm): medium (10.0 mm to 21.2 mm): short (5.0 mm to 10.0 mm) = 1:2:2.5.

[0039] A method for preparing the above-mentioned chrome corundum ramming material comprises the following steps:

[0040] 1) According to the above ratio, plate-shaped corundum aggregate, white corundum aggregate, brown corundum aggregate, and fused high chrome sand are weighed and added in order, and dry-mixed for 2-3 minutes using a mixer to obtain a first mixture;

[0041] 2) Add α-Al to the first mixture in step 1) 2 O 3 The powder is dry-mixed for 1-2 minutes to obtain a second mixture;

[0042] 3) Add the obtained composite binder to the second mixture of step 2) and dry mix for 3-5 minutes to obtain chrome corundum ramming material.

[0043] Example 2

[0044] A chrome corundum ramming material, the ramming material comprises the following raw materials in weight percentage: 10% of plate-shaped corundum aggregate with a particle size of (15.5-18.5mm), 12.5% ​​of white corundum aggregate with a particle size of (5-8mm), 12.5% ​​of white corundum aggregate with a particle size of (3-5mm), 25% of brown corundum aggregate with a particle size of (1-3mm), 3% of fused high chrome sand with a particle size of (0-1mm), α-Al 2 O 3 Micro powder (≤240 mesh) 2%, composite binder 35%; the required amount of added water accounts for 2wt% of the total weight of the ramming material;

[0045] The composite binder is composed of base material, cationic starch, oxalic acid and alumina short fibers; the base material is composed of the following raw materials in parts by weight: 5 parts of Suzhou clay, 5 parts of alumina cement, 5 parts of active SiO 2 5 parts of micro powder, 3 parts of ceramic ultrafine powder, 6 parts of magnesia fine powder, 2 parts of polyaluminium ferric chloride, Cr 2 O 3 1 part of micro powder, 1 part of calcium chromate; and cationic starch accounts for 1wt% of the total weight of the base material, oxalic acid accounts for 1wt% of the total weight of the base material, and alumina short fibers account for 2.5wt% of the total weight of the base material;

[0046] The preparation method of the obtained composite binder comprises the following steps:

[0047] Step S1, premixing: weighing the base material according to the above ratio and grinding it in a ball mill to obtain a premix;

[0048] Step S2, mixing; add cationic starch and oxalic acid to the premix of step S1 and grind and mix them for 2-3 minutes, then add alumina short fibers and grind them for 1-2 minutes, and grind them to a particle size of 320 mesh to obtain a composite binder.

[0049] Preferably, in step S2, the alumina short fibers are randomly added in a mixed manner with a length-to-weight ratio of long (21.2 mm to 24.5 mm): medium (10.0 mm to 21.2 mm): short (5.0 mm to 10.0 mm) = 1:2:2.5.

[0050] A method for preparing the above-mentioned chrome corundum ramming material comprises the following steps:

[0051] 1) According to the above ratio, plate-shaped corundum aggregate, white corundum aggregate, brown corundum aggregate, and fused high chrome sand are weighed and added in order, and dry-mixed for 2-3 minutes using a mixer to obtain a first mixture;

[0052] 2) Add α-Al to the first mixture in step 1) 2 O 3 The powder is dry-mixed for 1-2 minutes to obtain a second mixture;

[0053] 3) Add the obtained composite binder to the second mixture of step 2) and dry mix for 3-5 minutes to obtain chrome corundum ramming material.

[0054] Example 3

[0055] A chrome corundum ramming material, the ramming material comprises the following raw materials in weight percentage: 11% of plate-shaped corundum aggregate with a particle size of (15.5-18.5mm), 13.5% of white corundum aggregate with a particle size of (5-8mm), 13.5% of white corundum aggregate with a particle size of (3-5mm), 22% of brown corundum aggregate with a particle size of (1-3mm), 5% of fused high chrome sand with a particle size of (0-1mm), and α-Al 2 O 3 Micro powder (≤240 mesh) 3%, composite binder 32%; the required amount of added water accounts for 2.5wt% of the total weight of the ramming material;

[0056] The composite binder is composed of base material, cationic starch, oxalic acid and alumina short fibers; the base material is composed of the following raw materials in parts by weight: 4 parts of Suzhou clay, 4 parts of alumina cement, 4 parts of active SiO 2 4 parts of micro powder, 2.5 parts of ceramic ultrafine powder, 5 parts of magnesia fine powder, 1.5 parts of polyaluminium ferric chloride, Cr 2 O 3 0.5 parts of micro powder, 0.5 parts of calcium chromate; and cationic starch accounts for 0.5wt% of the total weight of the base material, oxalic acid accounts for 0.5wt% of the total weight of the base material, and alumina short fibers account for 2wt% of the total weight of the base material;

[0057] The preparation method of the obtained composite binder comprises the following steps:

[0058] Step S1, premixing: weighing the base material according to the above ratio and grinding it in a ball mill to obtain a premix;

[0059] Step S2, mixing; add cationic starch and oxalic acid to the premix of step S1 and grind and mix them for 2-3 minutes, then add alumina short fibers and grind them for 1-2 minutes, and grind the particles to a size of 320 mesh to obtain a composite binder.

[0060] Preferably, in step S2, the alumina short fibers are randomly added in a mixed manner with a length-to-weight ratio of long (21.2 mm to 24.5 mm): medium (10.0 mm to 21.2 mm): short (5.0 mm to 10.0 mm) = 1:2:2.5.

[0061] A method for preparing the above-mentioned chrome corundum ramming material comprises the following steps:

[0062] 1) According to the above ratio, plate-shaped corundum aggregate, white corundum aggregate, brown corundum aggregate, and fused high chrome sand are weighed and added in order, and dry-mixed for 2-3 minutes using a mixer to obtain a first mixture;

[0063] 2) Add α-Al to the first mixture in step 1) 2 O 3 The powder is dry-mixed for 1-2 minutes to obtain a second mixture;

[0064] 3) Add the obtained composite binder to the second mixture in step 2) and dry mix for 3 - 5 min to obtain the chrome corundum ramming mix.

[0065] Example 4

[0066] A chrome corundum ramming mix, the ramming mix comprising raw materials in the following weight percentages: tabular corundum aggregate with a particle size of (15.5 - 18.5 mm) 12.5%, white corundum aggregate with a particle size of (5 - 8 mm) 14.5%, white corundum aggregate with a particle size of (3 - 5 mm) 12.5%, brown corundum aggregate with a particle size of (1 - 3 mm) 21.5%, fused high-chromium sand with a particle size of (0 - 1 mm) 4%, α-Al 2 O 3 micropowder (≤240 mesh) 2.5%, composite binder 32.5%; the required additional water amount accounts for 2.5 wt% of the total weight of the ramming mix;

[0067] wherein the composite binder is composed of a base material, cationic starch, oxalic acid, and alumina short fibers; wherein the base material is composed of raw materials in the following weight parts: Suzhou clay 5 parts, bauxite cement 5 parts, active SiO 2 micropowder 5 parts, ceramic ultrafine powder 3 parts, magnesite fine powder 6 parts, polyaluminum ferric chloride 2 parts, Cr 2 O 3 micropowder 1 part, calcium chromate 1 part; and the cationic starch accounts for 1 wt% of the total weight of the base material, the oxalic acid accounts for 1 wt% of the total weight of the base material, and the alumina short fibers account for 2.5 wt% of the total weight of the base material;

[0068] Among them, the preparation method of the obtained composite binder includes the following steps:

[0069] Step S1, premixing; Weigh the base material according to the above ratio and co-grind it in a ball mill to obtain a premixed material;

[0070] Step S2, mixing; Add cationic starch and oxalic acid to the premixed material in step S1, co-grind and mix evenly for 2 - 3 min, and then add alumina short fibers to it and co-grind for 1 - 2 min. The co-grinding particle size is 320 mesh to obtain the composite binder.

[0071] Preferably, in step S2, the alumina short fibers are added in a disordered mixture with a length-to-weight ratio of long (21.2 mm - 24.5 mm): medium-long (10.0 mm - 21.2 mm): short (5.0 mm - 10.0 mm) = 1:2:2.5.

[0072] A method for preparing the above chrome corundum ramming mix includes the following steps:

[0073] 1) According to the above ratio, plate-shaped corundum aggregate, white corundum aggregate, brown corundum aggregate, and fused high chrome sand are weighed and added in order, and dry-mixed for 2-3 minutes using a mixer to obtain a first mixture;

[0074] 2) Add α-Al to the first mixture in step 1) 2 O 3 The powder is dry-mixed for 1-2 minutes to obtain a second mixture;

[0075] 3) Add the obtained composite binder to the second mixture of step 2) and dry mix for 3-5 minutes to obtain chrome corundum ramming material.

[0076] Example 5

[0077] A chrome corundum ramming material, the ramming material comprises the following raw materials in weight percentage: 13.5% of plate-shaped corundum aggregate with a particle size of (15.5-18.5mm), 12.5% ​​of white corundum aggregate with a particle size of (5-8mm), 14.5% of white corundum aggregate with a particle size of (3-5mm), 23% of brown corundum aggregate with a particle size of (1-3mm), 3.2% of fused high chrome sand with a particle size of (0-1mm), α-Al 2 O 3 Micro powder (≤240 mesh) 2.8%, composite binder 30.5%; the required amount of added water accounts for 3wt% of the total weight of the ramming material;

[0078] The composite binder is composed of base material, cationic starch, oxalic acid and alumina short fibers; the base material is composed of the following raw materials in parts by weight: 3 parts of Suzhou clay, 3 parts of alumina cement, 3 parts of active SiO 2 3 parts of micro powder, 2 parts of ceramic ultrafine powder, 4 parts of magnesia fine powder, 1.5 parts of polyaluminium ferric chloride, Cr 2 O 3 0.5 parts of micro powder, 0.5 parts of calcium chromate; and cationic starch accounts for 0.5wt% of the total weight of the base material, oxalic acid accounts for 0.5wt% of the total weight of the base material, and alumina short fibers account for 2wt% of the total weight of the base material;

[0079] The preparation method of the obtained composite binder comprises the following steps:

[0080] Step S1, premixing: weighing the base material according to the above ratio and grinding it in a ball mill to obtain a premix;

[0081] Step S2, mixing; add cationic starch and oxalic acid to the premix of step S1 and grind and mix them for 2-3 minutes, then add alumina short fibers and grind them for 1-2 minutes, and grind them to a particle size of 320 mesh to obtain a composite binder.

[0082] Preferably, in step S2, the alumina short fibers are randomly added in a mixed manner with a length-to-weight ratio of long (21.2 mm to 24.5 mm): medium (10.0 mm to 21.2 mm): short (5.0 mm to 10.0 mm) = 1:2:2.5.

[0083] A method for preparing the above-mentioned chrome corundum ramming material comprises the following steps:

[0084] 1) According to the above ratio, plate-shaped corundum aggregate, white corundum aggregate, brown corundum aggregate, and fused high chrome sand are weighed and added in order, and dry-mixed for 2-3 minutes using a mixer to obtain a first mixture;

[0085] 2) Add α-Al to the first mixture in step 1) 2 O 3 The powder is dry-mixed for 1-2 minutes to obtain a second mixture;

[0086] 3) Add the obtained composite binder to the second mixture of step 2) and dry mix for 3-5 minutes to obtain chrome corundum ramming material.

[0087] Example 6

[0088] A chrome corundum ramming material, the ramming material comprises the following raw materials in weight percentage: 14% of plate-shaped corundum aggregate with a particle size of (15.5-18.5mm), 13% of white corundum aggregate with a particle size of (5-8mm), 12.5% ​​of white corundum aggregate with a particle size of (3-5mm), 24% of brown corundum aggregate with a particle size of (1-3mm), 4.5% of fused high chrome sand with a particle size of (0-1mm), and α-Al 2 O 3 Micro powder (≤240 mesh) 2%, composite binder 30%; the required amount of added water accounts for 3wt% of the total weight of the ramming material;

[0089] The composite binder is composed of base material, cationic starch, oxalic acid and alumina short fibers; the base material is composed of the following raw materials in parts by weight: 4 parts of Suzhou clay, 4 parts of alumina cement, 4 parts of active SiO 2 4 parts of micro powder, 2.5 parts of ceramic ultrafine powder, 5 parts of magnesia fine powder, 1.5 parts of polyaluminium ferric chloride, Cr 2 O 3 0.5 parts of micro powder, 0.5 parts of calcium chromate; and cationic starch accounts for 0.8wt% of the total weight of the base material, oxalic acid accounts for 0.8wt% of the total weight of the base material, and alumina short fibers account for 2.2wt% of the total weight of the base material;

[0090] The preparation method of the obtained composite binder comprises the following steps:

[0091] Step S1, premixing: weighing the base material according to the above ratio and grinding it in a ball mill to obtain a premix;

[0092] Step S2, mixing; add cationic starch and oxalic acid to the premix of step S1 and grind and mix them for 2-3 minutes, then add alumina short fibers and grind them for 1-2 minutes, and grind them to a particle size of 320 mesh to obtain a composite binder.

[0093] Preferably, in step S2, the alumina short fibers are randomly added in a mixed manner with a length-to-weight ratio of long (21.2 mm to 24.5 mm): medium (10.0 mm to 21.2 mm): short (5.0 mm to 10.0 mm) = 1:2:2.5.

[0094] A method for preparing the above-mentioned chrome corundum ramming material comprises the following steps:

[0095] 1) According to the above ratio, plate-shaped corundum aggregate, white corundum aggregate, brown corundum aggregate, and fused high chrome sand are weighed and added in order, and dry-mixed for 2-3 minutes using a mixer to obtain a first mixture;

[0096] 2) Add α-Al to the first mixture in step 1) 2 O 3 The powder is dry-mixed for 1-2 minutes to obtain a second mixture;

[0097] 3) Add the obtained composite binder to the second mixture of step 2) and dry mix for 3-5 minutes to obtain chrome corundum ramming material.

[0098] Example 7

[0099] A chrome corundum ramming material, the ramming material comprises the following raw materials in weight percentage: 14% of plate-shaped corundum aggregate with a particle size of (15.5-18.5mm), 13% of white corundum aggregate with a particle size of (5-8mm), 12.5% ​​of white corundum aggregate with a particle size of (3-5mm), 24% of brown corundum aggregate with a particle size of (1-3mm), 4.5% of fused high chrome sand with a particle size of (0-1mm), and α-Al 2 O 3 Micro powder (≤240 mesh) 2%, composite binder 30%; the required amount of added water accounts for 3wt% of the total weight of the ramming material;

[0100] The composite binder is composed of base material, cationic starch, oxalic acid and alumina short fibers; the base material is composed of the following raw materials in parts by weight: 4 parts of Suzhou clay, 4 parts of alumina cement, 4 parts of active SiO 2 4 parts of micro powder, 2.5 parts of ceramic ultrafine powder, 5 parts of magnesia fine powder, 1.5 parts of polyaluminium ferric chloride, Cr 2 O 30.5 parts of micro powder, 0.5 parts of calcium chromate; and cationic starch accounts for 0.8wt% of the total weight of the base material, oxalic acid accounts for 0.8wt% of the total weight of the base material, and alumina short fibers account for 2.2wt% of the total weight of the base material;

[0101] The preparation method of the obtained composite binder comprises the following steps:

[0102] Step S1, premixing: weighing the base material according to the above ratio and grinding it in a ball mill to obtain a premix;

[0103] Step S2, mixing; add cationic starch and oxalic acid to the premix of step S1 and grind and mix them for 2-3 minutes, then add alumina short fibers and grind them for 1-2 minutes, and grind them to a particle size of 320 mesh to obtain a composite binder.

[0104] Preferably, in step S2, the alumina short fibers are randomly added in a mixed manner with a length-to-weight ratio of long (21.2 mm to 24.5 mm): medium (10.0 mm to 21.2 mm): short (5.0 mm to 10.0 mm) = 1:2:2.5.

[0105] A method for preparing the above-mentioned chrome corundum ramming material comprises the following steps:

[0106] 1) According to the above ratio, plate-shaped corundum aggregate, white corundum aggregate, brown corundum aggregate, and fused high chrome sand are weighed and added in order, and dry-mixed for 2-3 minutes using a mixer to obtain a first mixture;

[0107] 2) Add α-Al to the first mixture in step 1) 2 O 3 The powder is dry-mixed for 1-2 minutes to obtain a second mixture;

[0108] 3) Add the obtained composite binder to the second mixture of step 2) and dry mix for 3-5 minutes to obtain chrome corundum ramming material.

[0109] Performance Testing:

[0110] The chrome corundum ramming materials prepared in the above-mentioned embodiments 1-7 were subjected to various performance tests, and the specific data are shown in the following table:

[0111]

[0112] According to the above table, the binder of the present invention adds cationic starch at a weight percentage of 0.5% to 1% of the base material, which promotes the uniform distribution of active SiO2 powder, ceramic ultrafine powder, and Suzhou soil in the composite binder and forms a coupled state, so that the sintering temperature of the ramming material added with the composite binder is reduced to 1050°C, so that the low-temperature strength, medium-temperature strength, and high-temperature strength are all higher than 35MPa. With the increase of temperature, the strength increases, and the high-temperature stage strength increases quickly. The composite binder effectively improves the thermal shock stability of the ramming material. Adding oxalic acid at a weight percentage of 0.5% to 1% of the base raw material improves the coagulation performance of the composite binder, and the ramming material has good construction performance.

[0113] The ramming material is based on four-level grading of (8-5mm), (5-3mm), (3-1mm), and (1-0mm), with white corundum as large particles, brown corundum as medium particles, and fused high chrome sand as small particles. A specific amount (10% to 15%) of plate-shaped corundum aggregate (size 18.5-15.5mm) of specific particle size is added to form an island distribution in the material, which effectively blocks the expansion of stress cracks caused by drastic temperature changes during the use of the material, and further improves the thermal shock stability of the ramming material. Plate-shaped corundum aggregate is used as super particles, white corundum is used as large particles, brown corundum is used as medium particles, and high chrome sand is used as small particles. They are mixed and interspersed with each other according to weight and filled to form an ultra-stable, discontinuous particle support structure, and the characteristics of the thermal expansion coefficients of plate-shaped corundum, white corundum, and brown corundum are close and different, which improves the strength and thermal shock stability of the material and reduces the thermal expansion coefficient of the chrome corundum ramming material.

[0114] Calcium chromate introduced into the composite binder decomposes in situ to generate Cr at a temperature higher than 1350°C during use. 2 O 3 Penetrates into the surface of fused high chromium sand (particle size 1-0 mm) to form a surface rich in Cr 2 O 3 The content of aggregate structure is improved, and the high chromium sand aggregate is strongly connected to the matrix. The test strength (after sintering at 1550℃×3h) is increased by more than 8.5MPa compared with that without adding calcium chromate, and the thermal shock stability is increased by more than 5 times compared with that without adding calcium chromate. In addition, while ensuring good high temperature strength and thermal vibration stability, the Cr content in the ramming material is reduced. 2 O 3 content.

[0115] The composite binder is added in an optimal amount (30% to 35%), and the ramming material has good plastic ramming construction performance, easy sintering, and good matrix thermal shock stability. The strength and thermal vibration stability are significantly improved when the binder is added in an amount of (30% to 35%). When the addition amount exceeds 35% or is less than 30%, the strength and thermal vibration stability show a significant downward trend. The composite binder is added in an optimal amount (30% to 35%) and is used for the ramming material of the combustion chamber of a large-scale pellet belt roasting machine. The ramming material has high strength, good construction performance, high thermal shock stability, and reduces the Cr of the ramming material. 2 O 3 The content meets the working conditions of the combustion chamber, and the erosion resistance, cracking resistance, and thermal shock stability are significantly improved. In addition, the introduction of alumina short fibers in the composite binder interspersed in the ramming material matrix plays a role in improving the thermal shock stability. The short fiber length is mixed and added in an orderly manner with a weight ratio of long (24.5mm~21.2mm): medium (21.2mm~10.0mm): short (10.0mm~5.0mm) = 1:2:2.5, which can significantly improve by 5% compared with random addition.

[0116] In summary, the chrome corundum ramming material prepared by the present invention is applied to the combustion chamber of a large-scale pelletizing belt roaster and has the following performance indicators:

[0117]

[0118] Therefore, the ramming material obtained by the binder has high high temperature strength, erosion resistance, low thermal expansion coefficient, high thermal shock stability, no cracking, good construction performance, and meets the working conditions of the combustion chamber of a large-scale pellet belt roaster. It effectively protects the corundum-mullite composite bricks in the combustion chamber, prolongs the service life of the refractory lining of the combustion chamber, and the service life can reach more than 5 years, and reduces Cr 2 O 3 The content of refractory materials reduces the pollution of water bodies caused by residual lining of refractory materials and reduces the cost of materials.

[0119] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite binder for ramming material, It is characterized in that The composite binder is composed of a base material, cationic starch, oxalic acid, and alumina short fibers; the base material is composed of the following raw materials in parts by weight: 3-5 parts of Suzhou clay, 3-5 parts of alumina cement, and active SiO 2 3~5 parts of micro powder, 2~3 parts of ceramic ultrafine powder, 4~6 parts of magnesia fine powder, 1.5~2 parts of polyaluminium ferric chloride, Cr 2 O 3 0.5~1 part of micro powder, 0.5~1 part of calcium chromate; Among them, the cationic starch accounts for 0.5%~1wt% of the total weight of the base material; the oxalic acid accounts for 0.5%~1wt% of the total weight of the base material; and the alumina short fibers account for 2%~2.5wt% of the total weight of the base material.

2. The composite binder for ramming material according to claim 1, It is characterized in that The length L of the alumina short fibers is ≤25 mm.

3. The composite binder for ramming material according to claim 2, It is characterized in that The weight ratio of the alumina short fibers with lengths of 21.2 mm to 24.5 mm, 10.0 mm to 21.2 mm, and 5.0 mm to 10.0 mm is 1:2:2.

5.

4. The composite binder for ramming material according to claim 1, It is characterized in that The particle size of the composite binder is ≤320 meshes.

5. A method for preparing the composite binder for ramming material according to any one of claims 1 to 4: It is characterized in that The following steps are involved: Step S1, premixing: weighing the base material according to the above ratio and grinding it in a ball mill to obtain a premix; Step S2, mixing: add cationic starch and oxalic acid to the premix of step S1 and grind and mix them for 2-3 minutes, then add alumina short fibers and grind them for 1-2 minutes to obtain a composite binder.

6. The method for preparing the composite binder for ramming material according to claim 5, It is characterized in that In step S1, the ball milling time is 5 to 8 minutes.

7. A chrome corundum ramming mass, It is characterized in that The ramming material comprises the following raw materials in percentage by weight: 10% to 15% plate-shaped corundum aggregate, 25% to 30% white corundum aggregate, 20% to 25% brown corundum aggregate, 3% to 5% fused high chrome sand, and α-Al 2 O 3 2%~3% of micro powder, 30%~35% of composite binder, and 2%~3% of added water; the composite binder is the composite binder according to any one of claims 1-4.

8. The chrome corundum ramming mass according to claim 7, It is characterized in that The particle size of the plate-shaped corundum aggregate is 15.5-18.5 mm, the particle size of the white corundum aggregate is 5-8 mm and 3-5 mm, the particle size of the brown corundum aggregate is 1-3 mm, and the particle size of the fused high chrome sand is 0-1 mm.

9. A method for preparing the chrome corundum ramming mass according to claim 8, It is characterized in that The following steps are involved: 1) According to the above ratio, plate-shaped corundum aggregate, white corundum aggregate, brown corundum aggregate and fused high chrome sand are weighed and added in order, and dry mixed for 2-3 minutes using a mixer to obtain a first mixture; 2) Add α-Al to the first mixture in step 1) 2 O 3 The powder is dry-mixed for 1-2 minutes to obtain a second mixture; 3) Add the composite binder to the second mixture in step 2) and dry mix for 3-5 minutes to obtain chrome corundum ramming material.

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