Cement-complexed magnesium-aluminum composite binder, carbon-free machine-pressed wall-coated brick and preparation method thereof

Abstract

The application provides a cement-complex magnesium-aluminum composite binder, a carbon-free machine-pressed wall-encased brick and a preparation method thereof. The preparation raw materials of the cement-complex magnesium-aluminum composite binder include the following components in mass fraction: 50-70 parts of aluminate cement, 20-35 parts of complex magnesium-aluminum cementing agent, 5-15 parts of coagulant, 0.3-1.0 parts of dispersant, 0.5-1.2 parts of sintering aid and 1-3 parts of reinforcing fiber; the preparation raw materials of the complex magnesium-aluminum cementing agent include the following components in mass fraction: 22-48 parts of magnesium oxide, 36-50 parts of aluminum oxide, 10-25 parts of organic carboxylic acid complexing agent and 2-5 parts of coordination control agent. The cement-complex magnesium-aluminum composite binder can form a "rigidity-toughness" double-network cementing structure with LDH embedded in C-S-H matrix, so that the wall-encased brick has better strength performance, resistance to molten steel scouring performance and thermal shock stability, and can meet the smelting requirements of clean steel, ultra-low carbon steel and stainless steel.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of refractory materials for ladle walls, and particularly relates to a cement-complex magnesium-aluminum composite binder, a carbon-free machine-pressed ladle wall brick and a preparation method thereof. BACKGROUND

[0002] As the core material of the ladle lining, the ladle wall brick needs to have excellent high-temperature resistance, thermal shock resistance and molten slag corrosion resistance. Traditional ladle wall bricks mostly rely on carbon-containing binders (such as phenolic resin, pitch, etc.) to improve high-temperature strength and corrosion resistance. For example, the Chinese patent document with the publication number CN102584292A discloses a low-carbon ladle wall brick and a production method thereof, which uses a carbon-containing binder. However, carbon-containing binders have significant defects in production and use: (1) carbon emission and pollution: carbon-containing binders release harmful gases such as CO and VOCs at high temperatures, exacerbating environmental pollution; (2) risk of oxidation failure: carbon components are easily oxidized in an oxidizing atmosphere, leading to loose structure of the brick body and rapid reduction of service life. In order to replace carbon-containing systems, the industry has tried to use silicate, phosphate or aluminate inorganic binders. For example, the Chinese patent document with the publication number CN112408947A discloses a high-temperature-resistant coating for a ladle and a preparation method thereof, which uses aluminate cement as a binder. However, silicate, phosphate or aluminate binders still have the following problems: (1) insufficient low-temperature strength: silicate binders rely on high-temperature sintering to form ceramic bonds, and the low-temperature strength is low, which leads to easy breakage of the machine-pressed body; (2) poor corrosion resistance: phosphate binders are prone to phase change or dissolution in a high-temperature molten slag environment, and have insufficient structural stability; (3) contradiction between environmental protection and cost: some carbon-free binders need to add rare earth oxides or nanomaterials to enhance performance, which is high in raw material cost and complex in preparation process, and is difficult to be applied on a large scale. SUMMARY

[0003] The technical problem solved by the present application is to provide a cement-complex magnesium-aluminum composite binder, a carbon-free machine-pressed ladle wall brick and a preparation method thereof. The cement-complex magnesium-aluminum composite binder can form a "rigidity-toughness" double-network cementitious structure with LDH embedded in the C-S-H matrix, so that the ladle wall brick has better strength performance, molten steel scouring resistance and thermal shock stability, and meets the smelting needs of clean steel, ultra-low carbon steel and stainless steel.

[0004] In order to solve the above problems, the first aspect of the present application provides a cement-complex magnesium-aluminum composite binder, and the preparation raw materials thereof include the following components in mass fraction:

[0005] aluminate cement 50-70 parts, complex magnesium-aluminum cementing agent 20-35 parts, coagulant 5-15 parts, dispersing agent 0.3-1.0 parts, sintering aid 0.5-1.2 parts, and reinforcing fiber 1-3 parts;

[0006] The preparation raw materials of the complex magnesium-aluminum cementing agent include the following components in mass fraction:

[0007] Magnesium oxide 22~48 parts, aluminum oxide 36~50 parts, organic carboxylic acid complexing agent 10~25 parts, coordination control agent 2~5 parts.

[0008] Preferably, the preparation raw materials thereof include the following components in mass fraction:

[0009] Aluminate cement 55~65 parts, complex magnesium-aluminum cementing agent 25~30 parts, coagulant 8~12 parts, dispersant 0.3~0.8 parts, sintering aid 0.5~1 part, reinforcing fiber 1.5~2.5 parts;

[0010] The preparation raw materials of the complex magnesium-aluminum cementing agent include the following components in mass fraction:

[0011] Magnesium oxide 27~41 parts, aluminum oxide 36~50 parts, organic carboxylic acid complexing agent 15~22 parts, coordination control agent 2~4 parts.

[0012] Preferably, the coagulant is sodium silicate;

[0013] The dispersant is a polycarboxylic acid water reducer;

[0014] The sintering aid is lithium borate;

[0015] The reinforcing fiber is basalt fiber;

[0016] The organic carboxylic acid complexing agent is one or a combination of several of citric acid, tartaric acid and gluconic acid;

[0017] The coordination control agent is disodium ethylenediaminetetraacetate.

[0018] Preferably, the molar ratio of magnesium oxide to aluminum oxide is 1.5~2.5:1;

[0019] The molar ratio of carboxylic acid in the organic carboxylic acid complexing agent to Mg 2+ is 1:1~3;

[0020] The mass ratio of aluminate cement to complex magnesium-aluminum cementing agent is 1.8~2.7:1.

[0021] Preferably, the molecular weight of the polycarboxylic acid water reducer is 5000~10000;

[0022] The particle size of lithium borate is <10 μm;

[0023] The length of the basalt fiber is 3~6 mm, and the diameter is 10~15 μm.

[0024] The second aspect of the present application provides a preparation method of the above cement-complex magnesium-aluminum composite binder, comprising the following steps:

[0025] S1. Mixing magnesium oxide, aluminum oxide, water, organic carboxylic acid complexing agent, coordination control agent, and reacting at 70~80℃ for 1~2h to obtain a complex magnesium-aluminum cementing agent;

[0026] S2. Mixing the complex magnesium-aluminum cementing agent, aluminate cement, setting accelerator, dispersing agent, sintering aid, and reinforcing fiber to obtain a mixed slurry;

[0027] S3. Drying and calcining the mixed slurry to obtain the cement-complex magnesium-aluminum composite binder.

[0028] The third aspect of the application provides a carbon-free machine-pressed wall-coated brick, and the preparation raw materials include the following components in mass fraction:

[0029] 36~46 parts of tabular corundum, 38~42 parts of white corundum, 2~4 parts of magnesia, 5~6 parts of alumina micropowder, 0.3 parts of silica micropowder, 5~7 parts of fused magnesium-aluminum spinel, 0.8 parts of glucose, and 3.5~4.5 parts of the cement-complex magnesium-aluminum composite binder.

[0030] Preferably, the tabular corundum includes tabular corundum with a particle size of 6~3mm and tabular corundum with a particle size of 3~1mm, and the mass ratio of the tabular corundum with a particle size of 6~3mm to the tabular corundum with a particle size of 3~1mm is 1:1~3; the content of aluminum oxide in the tabular corundum is ≥99wt%;

[0031] The white corundum includes white corundum with a particle size of 1~0.074mm and white corundum with a particle size of 325 mesh, and the mass ratio of the white corundum with a particle size of 1~0.074mm to the white corundum with a particle size of 325 mesh is 1~3:1; the content of aluminum oxide in the white corundum is ≥99wt%;

[0032] The magnesia is large-crystal magnesia; the magnesia includes magnesia with a particle size of 1~0.074mm and magnesia with a particle size of 200 mesh, and the mass ratio of the magnesia with a particle size of 1~0.074mm to the magnesia with a particle size of 200 mesh is 1:1~3; the content of magnesium oxide in the magnesia is ≥96.5wt%;

[0033] The particle size of the alumina micropowder is ≤1μm, and the content of aluminum oxide in the alumina micropowder is ≥99wt%;

[0034] The content of silicon dioxide in the silica micropowder is ≥95wt%;

[0035] The particle size of the fused magnesium-aluminum spinel is 325 mesh, and the content of aluminum oxide in the fused magnesium-aluminum spinel is ≥75wt%;

[0036] The content of residual carbon in the glucose is ≥8, and the pH value is 4.0~6.5.

[0037] The fourth aspect of the present application provides a preparation method of the carbon-free machine-pressed wall-included brick, comprising the following steps:

[0038] The preparation raw materials of the carbon-free machine-pressed wall-included brick are mixed, and then put into a mold to perform heat treatment, so as to obtain the carbon-free machine-pressed wall-included brick.

[0039] Preferably, the temperature of the heat treatment is 160-200 DEG C, and the time is 16-20 h.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] The cement-complexed magnesium-aluminum composite binder of the present application is a composite of aluminate cement and complexed magnesium-aluminum cementing agent, which is used as a binder. Based on the dynamic reaction path of complexation-decomposition-release-gelation reconstruction: 1. The complexed magnesium-aluminum cementing agent can release Mg 2+ / Al 3+ in a directional manner in the alkaline environment of the aluminate cement, and reacts with Ca(OH)2 in the aluminate cement to generate layered double hydroxide (LDH, such as Mg6Al2(OH) 16 ); 2+ 2. The LDH and the calcium silicate hydration product (C-S-H gel) in the aluminate cement are bridged and interwoven through Ca 2- to form a "rigid-tough" double network gelation structure of "LDH embedded in C-S-H matrix", the C-S-H gel forms a nanosheet skeleton, and the LDH is embedded in the matrix without cracks at the interface, which is used as a binder of the ladle wall-included brick refractory material, and can make the cold compressive strength of the ladle wall-included brick ≥ 50 MPa, and the high-temperature (1200 DEG C) strength ≥ 30 MPa; 3. The LDH is transformed into a eutectic structure of magnesium-aluminum spinel (MgAl2O4, grain size 0.5-2 μm) and mullite (3Al2O3·2SiO2) through ion exchange (CO3 - / Cl

[0042] The cement-complexed magnesium-aluminum composite binder of the present application can realize gradient gelation: in the low-temperature stage (25-80 DEG C), the complexed magnesium-aluminum cementing agent slowly releases Mg 2+ , which reacts with the silicon powder in the binder raw materials to generate nano-MgSiO3 transition phase (specific surface area > 150 m 2 / g), which can fill the micron-sized pores of the matrix of the wall-included brick refractory material and improve the initial density of the green body; in the high-temperature sintering stage (> 1000 DEG C), Al 3+ dominates the generation of a eutectic system of magnesium-aluminum spinel (MgAl2O4) and mullite (3Al2O3·2SiO2), and the thermal expansion coefficient (7.5×10 -6The cement-complexed magnesium-aluminum composite binder is highly matched with the matrix of the brick lining refractory material, significantly reduces the thermal stress concentration, and enables the brick body to maintain structural integrity under the conditions of rapid cooling and heating (heating rate of 50℃ / min).

[0043] In the cement-complexed magnesium-aluminum composite binder, the aluminate cement is used as the base material to provide Ca 2+ , SiO4 4- and other hydration active components to generate C-S-H gel skeleton; the complexed magnesium-aluminum cementing agent is used to provide Mg 2+ / Al 3+ and complexing stabilization mechanism; the silica micropowder is used as nanoscale filler to fill the pores, promote the high-temperature mullitization reaction, and react with the released Mg 2+ of the complexed magnesium-aluminum cementing agent to generate nanoscale MgSiO3 transition phase (specific surface area > 150 m 2 / g) to fill the micrometer-scale pores of the matrix of the brick lining refractory material; the lithium borate is used as a high-temperature fluxing agent to form a eutectic liquid phase at high temperature, promote the interface diffusion sintering of the particles, reduce the sintering temperature, promote the liquid-phase diffusion densification, reduce the apparent porosity of the brick body to below 12%, and reduce the slag penetration resistance layer thickness from 2-3 mm of the traditional product to below 0.5 mm; the dispersant is used to optimize the rheological properties of the slurry; and the reinforcing fiber is used to enhance the toughness and inhibit the crack propagation.

[0044] The cement-complexed magnesium-aluminum composite binder of the present application discards the carbon-containing components, avoids the emission of CO / VOCs, and generates a dense MgCO3 protective layer in a CO2 atmosphere, which is compatible with industrial solid waste, ultimately prolongs the service life of the ladle, reduces the comprehensive cost by 15-20%, and has the advantages of zero-carbon environmental protection, process adaptability (demolding strength increased by 30-50%), and long-term durability. DETAILED DESCRIPTION

[0045] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0046] The first aspect of the embodiments of the present application provides a cement-complexed magnesium-aluminum composite binder, and the preparation raw materials thereof include the following components in mass fraction:

[0047] aluminate cement 50-70 parts, complexed magnesium-aluminum cementing agent 20-35 parts, setting accelerator 5-15 parts, dispersant 0.3-1.0 parts, sintering aid 0.5-1.2 parts, and reinforcing fiber 1-3 parts;

[0048] The preparation raw materials of the complex magnesium-aluminum cementing agent include the following components in mass fraction:

[0049] Magnesium oxide 22~48 parts, aluminum oxide 36~50 parts, organic carboxylic acid complexing agent 10~25 parts, coordination control agent 2~5 parts.

[0050] The cement-complex magnesium-aluminum composite binder of the embodiment of the application is a composite of aluminate cement and complex magnesium-aluminum cementing agent as a binder. Based on the dynamic reaction path of complexing-decomposition-releasing-gelation reconstruction: 1. The complex magnesium-aluminum cementing agent can release Mg 2+ / Al 3+ in the alkaline environment of aluminate cement to react with Ca(OH)2 in the aluminate cement to generate layered double hydroxide (LDH, such as Mg6Al2(OH) 16 );2. LDH and calcium silicate hydration products (C-S-H gel) in the aluminate cement are bridged and interwoven through Ca 2+ to form a "rigidity-toughness" double network gelation structure of "LDH embedded in C-S-H matrix", C-S-H gel forms a nanosheet layer skeleton, and LDH is embedded in the matrix, and the interface is crack-free, which is used as a binder for ladle wall brick refractory materials, and can make the cold compressive strength of the ladle wall brick ≥50 MPa, and the high temperature (1200℃) strength ≥30 MPa. 3. LDH exchanges ions (CO3 2- / Cl -) and high-temperature phase transition into magnesium aluminate spinel (MgAl2O4, grain size 0.5~2 pm) and eutectic structure with mullite (3Al2O3·2SiO2), which can improve the slag penetration resistance of refractory materials by 40% (principle: 1. Dense barrier effect. LDH high-temperature phase transition: layered double hydroxide (LDH) decomposes into magnesium aluminate spinel (MgAl2O4) and magnesium olivine (Mg2SiO4) at 1000~1200℃. The spinel grain size is small (0.5~2 pm) and the density is high (theoretical density 3.6 g / cm³), forming a physical barrier to block the penetration of molten slag (such as CaO-SiO2-Al2O3 system) into the brick body. The penetration path blockage rate: spinel phase filling rate > 85%, reducing the penetration depth of molten slag from 2~3 mm of traditional products to less than 0.5 mm (reduction > 75%). 2. Spinel-mullite eutectic corrosion resistance: spinel (MgAl2O4) and mullite (3Al2O3·2SiO2) form a eutectic structure, which has extremely high chemical stability: acid slag corrosion resistance: SiO2 in mullite reacts with FeO in slag to form high-viscosity iron olivine (Fe2SiO4), slowing down the penetration rate; alkali slag corrosion resistance: MgO in spinel reacts with CaO in slag to form high-melting-point calcium magnesium olivine (CaMgSiO4, melting point 1450℃), preventing slag layer migration. Corrosion resistance efficiency: the eutectic phase increases the contact angle of molten slag from 35° of traditional materials to 65°, reducing the wettability of slag (penetration rate ↓ 40%). 3. Ion selective adsorption. LDH interlayer ion exchange: dynamic exchange between LDH interlayer anions (such as CO3 2- ) and molten slag corrosive ions (such as Fe 2+ , S 2- ): after exchange, stable magnesium ferrite (MgFe2O4) phase is formed, consuming the corrosion medium and plugging the pores (adsorption capacity ≥ 120 mg / g). And microcrack self-repair (principle: 1. Low-temperature self-repair (25~600℃): ion exchange and carbonation. LDH interlayer ion migration: the exposed LDH interlayer CO3 2- in the environment exchanges with Cl⁻ / SO4 2- , generating insoluble chlorides / sulfates (such as CaCl2·2H2O), filling microcracks (repair width < 0.1 mm): MgO carbonation reaction: unreacted free MgO reacts with CO2 to form sheet brucite (Mg(OH)2) and magnesite (MgCO3) with a volume expansion rate of about 110%, effectively sealing cracks (repair efficiency > 60%). 2. High-temperature self-repair (> 800℃): recrystallization. Spinel phase transition expansion: spinel (MgAl2O4) expands by about 5~8% at high temperatures, actively extruding the crack wall to achieve "active healing"), maintaining the strength after thermal shock cycle > 85%.

[0051] The cement-complexed magnesium-aluminum composite binder of the embodiment of the present application can realize gradient gelation: the complexed magnesium-aluminum cementing agent slowly decomposes and releases Mg 2+ at a low temperature stage (25-80℃) to react with the silica powder in the binder raw material to generate nano-MgSiO3 transition phase (specific surface area > 150 m 2 / g), which can fill the micron-sized pores of the wall brick refractory material matrix and improve the initial density of the green body; at a high-temperature sintering stage (>1000℃), Al 3+ dominantly generates a eutectic system of magnesium aluminate spinel (MgAl2O4) and mullite (3Al2O3·2SiO2), and the thermal expansion coefficient (7.5×10 -6 / ℃) of the eutectic system is highly matched with the wall brick refractory material matrix, significantly reducing thermal stress concentration, so that the brick body still maintains structural integrity under rapid cooling and heating conditions (heating rate 50℃ / min).

[0052] In the cement-complexed magnesium-aluminum composite binder of the embodiment of the present application, the aluminate cement serves as a matrix material to provide Ca 2+ , SiO4 4- and other hydration active components to generate C-S-H gel skeleton; the complexed magnesium-aluminum cementing agent is used to provide Mg 2+ / Al 3+ and complexing and stabilizing mechanisms; the silica powder serves as a nano-sized filler to fill pores, promote high-temperature mullitization reaction, and react with Mg 2+ released by the complexed magnesium-aluminum cementing agent to generate nano-MgSiO3 transition phase (specific surface area > 150 m 2 / g) to fill the micron-sized pores of the wall brick refractory material matrix; lithium borate serves as a high-temperature fluxing agent to form a eutectic liquid phase at high temperature, promote interfacial diffusion sintering of particles, reduce sintering temperature, promote liquid-phase diffusion densification, reduce the apparent porosity of the brick body to below 12%, and reduce the slag penetration resistance layer thickness from 2-3 mm of traditional products to within 0.5 mm; the dispersant is used to optimize the rheological properties of the slurry; and the reinforcing fiber is used to enhance toughness and inhibit crack propagation.

[0053] The binder abandons carbon-containing components to avoid CO / VOCs emissions, and MgO generates a dense MgCO3 protective layer in a CO2 atmosphere, which is compatible with industrial solid waste, ultimately prolongs the service life of the ladle, reduces the comprehensive cost by 15%-20%, and has the advantages of zero-carbon environmental protection, process adaptability (demolding strength increased by 30%-50%), and long-term durability.

[0054] Preferably, the preparation raw materials include the following components in mass fractions:

[0055] Aluminate cement 55~65 parts, complex magnesium-aluminum binder 25~30 parts, coagulant 8~12 parts, dispersant 0.3~0.8 parts, sintering aid 0.5~1 part, reinforcing fiber 1.5~2.5 parts;

[0056] The preparation raw materials of the complex magnesium-aluminum binder include the following components in mass fraction:

[0057] Magnesium oxide 27~41 parts, aluminum oxide 36~50 parts, organic carboxylic acid complexing agent 15~22 parts, coordination control agent 2~4 parts.

[0058] With the above preferred mass fraction, the performance of the cement-complex magnesium-aluminum composite binder is better, and the binder used for ladle wall brick has better strength performance, thermal shock stability and slag erosion resistance.

[0059] Preferably, the coagulant is sodium silicate.

[0060] Preferably, the dispersant is polycarboxylic acid water reducer. The molecular weight of the polycarboxylic acid water reducer is 5000~10000.

[0061] Preferably, the sintering aid is lithium borate. The particle size of lithium borate is <10 μm.

[0062] Preferably, the reinforcing fiber is basalt fiber. The length of the basalt fiber is 3~6 mm, and the diameter is 10~15 μm.

[0063] Preferably, the organic carboxylic acid complexing agent is one or a combination of citric acid, tartaric acid and gluconic acid.

[0064] Preferably, the coordination control agent is disodium ethylenediaminetetraacetate.

[0065] Preferably, the molar ratio of magnesium oxide to aluminum oxide is 1.5~2.5:1. By further controlling the molar ratio of MgO to Al2O3, an appropriate amount of magnesium aluminate spinel (MgAl2O4) can be generated by high-temperature phase transition, thereby improving the strength performance of the refractory material. Further preferably, the molar ratio of magnesium oxide to aluminum oxide is 2:1.

[0066] Preferably, the molar ratio of carboxylic acid to Mg 2+ in the organic carboxylic acid complexing agent is 1:1~3. The formation of stable soluble complex can be better controlled.

[0067] Preferably, the mass ratio of aluminate cement to complex magnesium-aluminum binder is 1.8~2.7:1. Within this preferred ratio range, a "rigidity-toughness" double network cementitious structure of "LDH embedded in C-S-H matrix" can be better formed, so that the strength performance, thermal shock stability and slag erosion resistance of the ladle wall brick are better.

[0068] The second aspect of the embodiment of the present application provides a preparation method of the cement-complexed magnesium-aluminum composite binder.

[0069] S1. mixing magnesium oxide, aluminum oxide, water, an organic carboxylic acid complexing agent, and a coordination control agent, and reacting at 70-80℃ for 1-2h to obtain a complexed magnesium-aluminum cementing agent;

[0070] S2. mixing the complexed magnesium-aluminum cementing agent, an aluminate cement, a setting accelerator, a dispersing agent, a sintering aid, and a reinforcing fiber to obtain a mixed slurry;

[0071] S3. drying and calcining the mixed slurry to obtain the cement-complexed magnesium-aluminum composite binder.

[0072] Preferably, step S1 specifically comprises:

[0073] The magnesium oxide and the aluminum oxide are mixed in proportion and ball milled to a D50 particle size of ≤5μm; 0.5% of stearic acid is added as a grinding aid to prevent particle agglomeration; water, the organic carboxylic acid complexing agent, and the coordination control agent are mixed and stirred until completely dissolved, at a temperature of 50-60℃ and a pH of 2.5-3.5; the ball-milled mixed powder of magnesium oxide and aluminum oxide is added thereto, the reaction temperature is controlled at 70-80℃, and stirring is performed for 1.5h to obtain the complexed magnesium-aluminum cementing agent.

[0074] Preferably, step S2 specifically comprises:

[0075] The aluminate cement, the setting accelerator, the dispersing agent, and the sintering aid are added to the complexed magnesium-aluminum cementing agent, and ultrasonic dispersion is performed for 20min; the reinforcing fiber is added, and low-speed stirring is performed for 10min to avoid fiber breakage, to obtain the mixed slurry.

[0076] Preferably, step S3 specifically comprises:

[0077] The mixed slurry is spray dried, with an inlet temperature of 180℃ and an outlet temperature of 80℃, to obtain a powder with a particle size of 50-100μm; the powder is calcined at 250℃ for 1h to obtain the cement-complexed magnesium-aluminum composite binder.

[0078] The third aspect of the embodiment of the present application provides a carbon-free machine-pressed wall-coated brick, and the preparation raw materials thereof comprise the following components in mass fractions:

[0079] 36-46 parts of tabular corundum, 38-42 parts of white corundum, 2-4 parts of magnesia, 5-6 parts of aluminum oxide micropowder, 0.3 parts of silica micropowder, 5-7 parts of fused magnesium-aluminum spinel, 0.8 parts of glucose, and 3.5-4.5 parts of the cement-complexed magnesium-aluminum composite binder.

[0080] The carbon-free machine-pressed wall-coated brick of the embodiment of the present application adopts cement-complexed magnesium-aluminum combined binder, forms a "rigidity-toughness" double-network gel structure of "LDH inlaid in C-S-H matrix", and converts into magnesium-aluminum spinel and mullite eutectic structure through ion exchange and high-temperature phase transformation, so that the ladle wall-coated brick has better normal-temperature compressive strength, high-temperature strength, molten slag penetration resistance and thermal shock stability.

[0081] Preferably, the tabular corundum includes tabular corundum with a particle size of 6-3mm, tabular corundum with a particle size of 3-1mm, and the mass ratio of the tabular corundum with a particle size of 6-3mm to the tabular corundum with a particle size of 3-1mm is 1:1-3; the content of alumina in the tabular corundum is ≥99wt%;

[0082] Preferably, the white corundum includes white corundum with a particle size of 1-0.074mm, white corundum with a particle size of 325 mesh, and the mass ratio of the white corundum with a particle size of 1-0.074mm to the white corundum with a particle size of 325 mesh is 1-3:1; the content of alumina in the white corundum is ≥99wt%;

[0083] Preferably, the magnesia is large-crystal magnesia; the magnesia includes magnesia with a particle size of 1-0.074mm, magnesia with a particle size of 200 mesh, and the mass ratio of the magnesia with a particle size of 1-0.074mm to the magnesia with a particle size of 200 mesh is 1:1-3; the content of magnesia in the magnesia is ≥96.5wt%.

[0084] Preferably, the particle size of the alumina micropowder is ≤1μm, and the content of alumina in the alumina micropowder is ≥99wt%.

[0085] Preferably, the content of silicon dioxide in the silicon micropowder is ≥95wt%.

[0086] Preferably, the particle size of the fused magnesium-aluminum spinel is 325 mesh, and the content of alumina in the fused magnesium-aluminum spinel is ≥75wt%.

[0087] Preferably, the residual carbon in the glucose is ≥8, and the pH value is 4.0-6.5.

[0088] The fourth aspect of the embodiment of the present application provides a preparation method of the above-mentioned carbon-free machine-pressed wall-coated brick, including the following steps:

[0089] The preparation raw materials of the carbon-free machine-pressed wall-coated brick are mixed, and then put into a mold to perform heat treatment, so as to obtain the carbon-free machine-pressed wall-coated brick.

[0090] Preferably, the temperature of the heat treatment is 160℃-200℃, and the time is 16h-20h.

[0091] In the following examples, the polycarboxylic acid water reducing agent has a molecular weight of 5000-10000; the lithium borate has a particle size of <10 μm; the basalt fiber has a length of 3-6 mm and a diameter of 10-15 μm; the tabular corundum has an alumina content of ≥99 wt%; the white corundum has an alumina content of ≥99 wt%; the magnesia has a magnesium oxide content of ≥96.5 wt%; the alumina micropowder has a particle size of ≤1 μm and an alumina content of ≥99 wt%; the silica micropowder has a silicon dioxide content of ≥95 wt%; the fused magnesia-alumina spinel has a particle size of 325 mesh and an alumina content of ≥75 wt%; and the glucose has a residual carbon content of ≥8 and a pH value of 4.0-6.5.

[0092] In the following examples, the aluminate cement is a product of type 80sc21 of Shengchuan Environmental Technology Co., Ltd.

[0093] Example 1

[0094] The carbon-free machine-pressed wall brick of the present example is prepared from raw materials including the following components in mass fractions:

[0095] Tabular corundum with a particle size of 6-3 mm 15 parts, tabular corundum with a particle size of 3-1 mm 31 parts, white corundum with a particle size of 1-0.074 mm 24 parts, white corundum with a particle size of 325 mesh 14 parts, large crystalline magnesia with a particle size of 1-0.074 mm 1 part, large crystalline magnesia with a particle size of 200 mesh 1 part, alumina micropowder 5 parts, silica micropowder 0.3 parts, fused magnesia-alumina spinel 5 parts, glucose 0.8 part, cement-complexed magnesia-alumina composite binder 3.5 parts.

[0096] The cement-complexed magnesia-alumina composite binder is prepared from raw materials including the following components in mass fractions:

[0097] Aluminate cement 60 parts, complexed magnesia-alumina cementing agent 27 parts, sodium silicate 10 parts, polycarboxylic acid water reducing agent (Leikete Chongqing Chemical Products Co., Ltd., type KR55S) 0.4 part, lithium borate 0.6 part, basalt fiber 2 parts.

[0098] The complexed magnesia-alumina cementing agent is prepared from raw materials including the following components in mass fractions:

[0099] Magnesium oxide 34 parts, alumina 43 parts, citric acid 20 parts, EDTA-2Na 3 parts.

[0100] In the present example, the cement-complexed magnesia-alumina composite binder is prepared by the following method:

[0101] S1. Mix magnesium oxide and aluminum oxide in proportion, ball mill to D50 particle size ≤5 μm; add 0.5% of the total mass of stearic acid as a grinding aid to prevent particle agglomeration; mix water, citric acid and EDTA-2Na, stir until completely dissolved, temperature is 60℃, pH is 3; add the ball-milled magnesium oxide and aluminum oxide mixed powder to it, control the reaction temperature to 70℃, stir for 1.5 h, to obtain a complex magnesium-aluminum cementing agent.

[0102] S2. Add aluminate cement, sodium silicate, polycarboxylate superplasticizer and lithium borate to the complex magnesium-aluminum cementing agent, ultrasonic dispersion for 20 min; add basalt fiber, low-speed stirring for 10 min to avoid fiber breakage, to obtain a mixed slurry.

[0103] S3. Spray dry the mixed slurry, inlet temperature 180℃, outlet temperature 80℃, to obtain a powder with particle size of 50-100 μm; calcine the powder at 250℃ for 1 h, to obtain a cement-complex magnesium-aluminum composite binder.

[0104] The preparation method of the carbon-free machine-pressed wall-encased brick of the present embodiment comprises the following steps:

[0105] Mix the granular materials with particle sizes of 6-3 mm, 3-1 mm and 1-0.074 mm in the preparation raw materials, dry mix for about 1 min, then uniformly and slowly add the weighed water, further add the cement-complex magnesium-aluminum composite binder, mix for about 5 min, finally add the 325 mesh and 200 mesh powders, aluminum oxide micropowder, silicon micropowder and glucose in the preparation raw materials, mix for 20 min, check for qualification, and then discharge; put the qualified prepared materials into a mold, form according to the type and shape of the brick on a corresponding tonnage press, and use a 630T electric screw brick press; push the qualified brick into a heat treatment kiln for heat treatment, the internal temperature of the heat treatment kiln is 200℃, and the baking time is 18 h, to obtain the carbon-free machine-pressed wall-encased brick.

[0106] Example 2

[0107] The preparation raw materials of the carbon-free machine-pressed wall-encased brick of the present embodiment comprise the following components in mass fractions:

[0108] 12 parts of tabular corundum with particle size of 6-3 mm, 24 parts of tabular corundum with particle size of 3-1 mm, 28 parts of white corundum with particle size of 1-0.074 mm, 14 parts of white corundum with particle size of 325 mesh, 2 parts of large crystalline magnesia with particle size of 1-0.074 mm, 2 parts of large crystalline magnesia with particle size of 200 mesh, 6 parts of aluminum oxide micropowder, 0.3 parts of silicon micropowder, 7 parts of electrically fused magnesium-aluminum spinel, 0.8 parts of glucose, and 4.5 parts of cement-complex magnesium-aluminum composite binder.

[0109] In the present embodiment, the preparation raw materials of the complex magnesium-aluminum cementing agent are the same as those in Example 1.

[0110] In this embodiment, the preparation method of the complex magnesium-aluminum cement and the carbon-free machine-pressed wall-coated brick is the same as that in Embodiment 1.

[0111] Embodiment 3

[0112] The carbon-free machine-pressed wall-coated brick of this embodiment is prepared from the following components in mass fraction:

[0113] 12 parts of tabular corundum with particle size of 6-3 mm, 26 parts of tabular corundum with particle size of 3-1 mm, 27 parts of white corundum with particle size of 1-0.074 mm, 14 parts of white corundum with particle size of 325 mesh, 1.5 parts of large crystalline magnesia with particle size of 1-0.074 mm, 1.5 parts of large crystalline magnesia with particle size of 200 mesh, 5 parts of alumina micropowder, 0.3 parts of silica micropowder, 5 parts of fused magnesium-aluminum spinel, 0.8 parts of glucose, and 3.5 parts of cement-complex magnesium-aluminum composite binder.

[0114] In this embodiment, the preparation raw materials of the complex magnesium-aluminum cement are the same as those in Embodiment 1.

[0115] In this embodiment, the preparation method of the complex magnesium-aluminum cement and the carbon-free machine-pressed wall-coated brick is the same as that in Embodiment 1.

[0116] Embodiment 4

[0117] The carbon-free machine-pressed wall-coated brick of this embodiment is prepared from the following components in mass fraction:

[0118] 12 parts of tabular corundum with particle size of 6-3 mm, 26 parts of tabular corundum with particle size of 3-1 mm, 27 parts of white corundum with particle size of 1-0.074 mm, 14 parts of white corundum with particle size of 325 mesh, 1.5 parts of large crystalline magnesia with particle size of 1-0.074 mm, 1.5 parts of large crystalline magnesia with particle size of 200 mesh, 5 parts of alumina micropowder, 0.3 parts of silica micropowder, 5 parts of fused magnesium-aluminum spinel, 0.8 parts of glucose, and 3.5 parts of cement-complex magnesium-aluminum composite binder.

[0119] In this embodiment, the preparation raw materials of the complex magnesium-aluminum cement are the same as those in Embodiment 1.

[0120] In this embodiment, the preparation method of the complex magnesium-aluminum cement and the carbon-free machine-pressed wall-coated brick is the same as that in Embodiment 1.

[0121] Embodiment 5

[0122] The carbon-free machine-pressed wall-coated brick of this embodiment is prepared from the following components in mass fraction:

[0123] Tabular corundum with particle size of 6-3 mm 14 parts, tabular corundum with particle size of 3-1 mm 28 parts, white corundum with particle size of 1-0.074 mm 24 parts, white corundum with particle size of 325 mesh 14 parts, large crystalline magnesia with particle size of 1-0.074 mm 2 parts, large crystalline magnesia with particle size of 200 mesh 2 parts, alumina micropowder 6 parts, silica micropowder 0.3 parts, fused magnesia-alumina spinel 5 parts, glucose 0.8 parts, cement-complexed magnesia-alumina composite binder 4.5 parts.

[0124] In the embodiment, the preparation raw materials of the complexed magnesia-alumina cementing agent are the same as those in Embodiment 1.

[0125] In the embodiment, the preparation raw materials of the complexed magnesia-alumina cementing agent and the preparation method of the carbon-free machine-pressed wall-hung brick are the same as those in Embodiment 1.

[0126] Embodiment 6

[0127] In the embodiment, the preparation raw materials of the carbon-free machine-pressed wall-hung brick, the preparation method are the same as those in Embodiment 3, and the difference lies in that the preparation raw materials of the cement-complexed magnesia-alumina composite binder are different.

[0128] In the embodiment, the preparation raw materials of the cement-complexed magnesia-alumina composite binder include the following components in mass fraction:

[0129] Aluminate cement 65 parts, complexed magnesia-alumina cementing agent 25 parts, sodium silicate 8 parts, polycarboxylic acid water reducer (Leikete Chongqing Chemical Products Co., Ltd., model KR55S) 0.3 parts, lithium borate 1 part, basalt fiber 1.5 parts. Among them, the preparation raw materials of the complexed magnesia-alumina cementing agent are the same as those in Embodiment 3.

[0130] Embodiment 7

[0131] In the embodiment, the preparation raw materials of the carbon-free machine-pressed wall-hung brick, the preparation method are the same as those in Embodiment 3, and the difference lies in that the preparation raw materials of the cement-complexed magnesia-alumina composite binder are different.

[0132] In the embodiment, the preparation raw materials of the cement-complexed magnesia-alumina composite binder include the following components in mass fraction:

[0133] Aluminate cement 55 parts, complexed magnesia-alumina cementing agent 30 parts, sodium silicate 12 parts, polycarboxylic acid water reducer (Leikete Chongqing Chemical Products Co., Ltd., model KR55S) 0.8 parts, lithium borate 0.5 parts, basalt fiber 2.5 parts. Among them, the preparation raw materials of the complexed magnesia-alumina cementing agent are the same as those in Embodiment 3.

[0134] Embodiment 8

[0135] In the embodiment, the preparation raw materials of the carbon-free machine-pressed wall-hung brick, the preparation method are the same as those in Embodiment 3, and the difference lies in that the preparation raw materials of the cement-complexed magnesia-alumina composite binder are different.

[0136] In this embodiment, the preparation raw materials of the cement-complex magnesium-aluminum composite binder include the following components in mass fraction:

[0137] Aluminate cement 70 parts, complex magnesium-aluminum cementing agent 20 parts, sodium silicate 5 parts, polycarboxylic acid water reducer (Leikete Chongqing Chemical Products Co., Ltd., model KR55S) 0.3 parts, lithium borate 1.2 parts, basalt fiber 3 parts. Among them, the preparation raw materials of the complex magnesium-aluminum cementing agent are the same as those in Example 3.

[0138] Example 9

[0139] The carbon-free machine-pressed wall-coated brick of this embodiment has the same preparation raw materials and preparation method as those of Example 3, except that the preparation raw materials of the cement-complex magnesium-aluminum composite binder are different.

[0140] In this embodiment, the preparation raw materials of the cement-complex magnesium-aluminum composite binder include the following components in mass fraction:

[0141] Aluminate cement 50 parts, complex magnesium-aluminum cementing agent 35 parts, sodium silicate 15 parts, polycarboxylic acid water reducer (Leikete Chongqing Chemical Products Co., Ltd., model KR55S) 1 part, lithium borate 0.5 part, basalt fiber 1 part. Among them, the preparation raw materials of the complex magnesium-aluminum cementing agent are the same as those in Example 3.

[0142] Example 10

[0143] The carbon-free machine-pressed wall-coated brick of this embodiment has the same preparation raw materials and preparation method as those of Example 3, except that the preparation raw materials of the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binder are different.

[0144] In this embodiment, the molar ratio of magnesium oxide to aluminum oxide in the preparation raw materials of the complex magnesium-aluminum cementing agent is 1.5:1. It includes the following components in mass fraction:

[0145] Magnesium oxide 29 parts, aluminum oxide 48 parts, citric acid 20 parts, EDTA-2Na 3 parts.

[0146] Example 11

[0147] The carbon-free machine-pressed wall-coated brick of this embodiment has the same preparation raw materials and preparation method as those of Example 3, except that the preparation raw materials of the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binder are different.

[0148] In this embodiment, the molar ratio of magnesium oxide to aluminum oxide in the preparation raw materials of the complex magnesium-aluminum cementing agent is 2.5:1. It includes the following components in mass fraction:

[0149] Magnesium oxide 38 parts, aluminum oxide 39 parts, citric acid 20 parts, EDTA-2Na 3 parts.

[0150] Example 12

[0151] The carbon-free machine-pressed wall brick of this example has the same raw materials and preparation method as those of Example 3, except that the preparation raw materials of the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binder are different.

[0152] In this example, the molar ratio of magnesium oxide to aluminum oxide in the preparation raw materials of the complex magnesium-aluminum cementing agent is 1.38:1. The components include the following mass fractions:

[0153] Magnesium oxide 27 parts, aluminum oxide 50 parts, citric acid 20 parts, EDTA-2Na 3 parts.

[0154] Example 13

[0155] The carbon-free machine-pressed wall brick of this example has the same raw materials and preparation method as those of Example 3, except that the preparation raw materials of the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binder are different.

[0156] In this example, the molar ratio of magnesium oxide to aluminum oxide in the preparation raw materials of the complex magnesium-aluminum cementing agent is 2.9:1. The components include the following mass fractions:

[0157] Magnesium oxide 41 parts, aluminum oxide 36 parts, citric acid 20 parts, EDTA-2Na 3 parts.

[0158] Example 14

[0159] The carbon-free machine-pressed wall brick of this example has the same raw materials and preparation method as those of Example 3, except that the preparation raw materials of the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binder are different.

[0160] In this example, the molar ratio of carboxylic acid in citric acid to Mg 2+ in the preparation raw materials of the complex magnesium-aluminum cementing agent is 1:0.85. The components include the following mass fractions:

[0161] Magnesium oxide 23 parts, aluminum oxide 32 parts, citric acid 43 parts, EDTA-2Na 2 parts.

[0162] Example 15

[0163] The carbon-free machine-pressed wall brick of this example has the same raw materials and preparation method as those of Example 3, except that the preparation raw materials of the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binder are different.

[0164] In this example, the molar ratio of carboxylic acid in citric acid to Mg 2+ in the preparation raw materials of the complex magnesium-aluminum cementing agent is 1:5. The components include the following mass fractions:

[0165] Magnesia 38 parts, alumina 48 parts, citric acid 12 parts, EDTA-2Na 2 parts.

[0166] Example 16

[0167] The carbon-free machine-pressed wall-inlaid brick of the present example has the same raw materials and preparation method as those of Example 3, except that the mass fractions of the aluminate cement and the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binding agent are different. In the present example, the aluminate cement is 63 parts and the complex magnesium-aluminum cementing agent is 24 parts. That is, the mass ratio of the aluminate cement to the complex magnesium-aluminum cementing agent is 2.625:1.

[0168] Example 17

[0169] The carbon-free machine-pressed wall-inlaid brick of the present example has the same raw materials and preparation method as those of Example 3, except that the mass fractions of the aluminate cement and the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binding agent are different. In the present example, the aluminate cement is 56 parts and the complex magnesium-aluminum cementing agent is 31 parts. That is, the mass ratio of the aluminate cement to the complex magnesium-aluminum cementing agent is 1.81:1.

[0170] Example 18

[0171] The carbon-free machine-pressed wall-inlaid brick of the present example has the same raw materials and preparation method as those of Example 3, except that the mass fractions of the aluminate cement and the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binding agent are different. In the present example, the aluminate cement is 65 parts and the complex magnesium-aluminum cementing agent is 22 parts. That is, the mass ratio of the aluminate cement to the complex magnesium-aluminum cementing agent is 2.95:1.

[0172] Example 19

[0173] The carbon-free machine-pressed wall-inlaid brick of the present example has the same raw materials and preparation method as those of Example 3, except that the mass fractions of the aluminate cement and the complex magnesium-aluminum cementing agent in the cement-complex magnesium-aluminum composite binding agent are different. In the present example, the aluminate cement is 54 parts and the complex magnesium-aluminum cementing agent is 33 parts. That is, the mass ratio of the aluminate cement to the complex magnesium-aluminum cementing agent is 1.64:1.

[0174] Comparative Example 1

[0175] The carbon-free machine-pressed wall-inlaid brick of the present example has the same raw materials and preparation method as those of Example 3, except that the cement-complex magnesium-aluminum composite binding agent is replaced by the aluminate cement.

[0176] The cold compressive strength, high-temperature strength, molten slag penetration resistance, and thermal shock stability of the carbon-free machine-pressed wall-inlaid bricks of the above examples were tested, and the test results are shown in Table 1 below.

[0177] From the data in Table 1, compared with the carbon-free machine-pressed wall-encased brick of Comparative Example 1, the carbon-free machine-pressed wall-encased bricks of each embodiment of the present application all have significantly better cold compressive strength, high-temperature strength, slag penetration resistance and thermal shock stability.

[0178] Comparative Examples 3, 6-9 differ in that the raw material ratio in the cement-complexed magnesium-aluminum composite binder is different, wherein the raw material ratio in Examples 3, 6 and 7 is within the preferred range, and the carbon-free machine-pressed wall-encased bricks thereof have better performance than Examples 8 and 9.

[0179] Comparative Examples 3, 10-13 differ in that the molar ratio of magnesium oxide to aluminum oxide in the raw materials for preparing the complexed magnesium-aluminum cementing agent is different, wherein the molar ratio of magnesium oxide to aluminum oxide in Examples 3, 10 and 11 is within the preferred range, and the carbon-free machine-pressed wall-encased bricks thereof have better performance than Examples 12 and 13.

[0180] Comparative Examples 3, 14 and 15 differ in that the molar ratio of carboxylic acid in citric acid to Mg 2+ in the raw materials for preparing the complexed magnesium-aluminum cementing agent is different, and the molar ratio of carboxylic acid in citric acid to Mg 2+ in Example 3 is within the preferred range, which can better control the formation of stable soluble complexes, and the carbon-free machine-pressed wall-encased bricks thereof have better performance than Examples 14 and 15.

[0181] Comparative Examples 3, 16-19 differ in that the mass ratio of aluminate cement to complexed magnesium-aluminum cementing agent in the cement-complexed magnesium-aluminum composite binder is different, wherein the mass ratio of aluminate cement to complexed magnesium-aluminum cementing agent in Examples 3, 16 and 17 is within the preferred range, which can better form the "rigidity-toughness" dual-network cementitious structure of "LDH embedded in C-S-H matrix", and the strength performance, thermal shock stability and slag erosion resistance of the wall-encased bricks are better.

[0182] Table 1

[0183] Room temperature pressure resistance, MPa High temperature bending resistance, MPa Slag resistance, mm Thermal shock resistance, times Example 1 120 0.9 9 13 Example 2 123 1.0 10 12 Example 3 140 1.2 8 15 Example 4 116 1.0 10 10 Example 5 120 1.1 10 9 Example 6 132 1.1 10 13 Example 7 128 1.1 9 12 Example 8 112 0.9 13 8 Example 9 114 0.8 12 7 Example 10 129 1.1 10 14 Example 11 122 1.0 9 13 Example 12 105 0.9 16 8 Example 13 108 0.8 13 9 Example 14 113 0.9 11 7 Example 15 118 0.8 12 6 Example 16 135 1.2 8 15 Example 17 139 1.2 9 13 Example 18 124 0.8 13 9 Example 19 116 1.0 15 9 Comparative Example 1 95 0.7 18 5

[0184] Obviously, the above embodiments are merely examples for the sake of clarity, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can also be made by those of ordinary skill in the art. It is not necessary or possible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A cement-complexed magnesium-aluminum composite binder, characterized in that: The raw materials for its preparation include the following components in parts by mass: 50-70 parts of aluminate cement, 20-35 parts of complex magnesium-aluminum binder, 5-15 parts of coagulant, 0.3-1.0 parts of dispersant, 0.5-1.2 parts of sintering aid, 1-3 parts of reinforcing fiber; The raw materials for preparing the complex magnesium-aluminum binder include the following components in parts by mass: 22-48 parts of magnesium oxide, 36-50 parts of aluminum oxide, 10-25 parts of an organic carboxylic acid complexing agent, and 2-5 parts of a coordination regulator; the coordination regulator is disodium ethylenediaminetetraacetic acid; The preparation method of the cement-complexed magnesium-aluminum composite binder comprises the following steps: S1. Mixing magnesium oxide, aluminum oxide, water, an organic carboxylic acid complexing agent, and a coordination regulator, and reacting at 70-80°C for 1-2 hours to obtain a complex magnesium-aluminum binder; S2. The magnesium-aluminum complex binder, aluminate cement, a coagulant, a dispersant, a sintering aid, and reinforcing fibers are mixed to obtain a mixed slurry; S3. Drying and calcining the mixed slurry to obtain the cement-complexed magnesium-aluminum composite binder.

2. The cement-complexed magnesium-aluminum composite binder according to claim 1, characterized in that: The raw materials for its preparation include the following components in parts by mass: 55-65 parts of aluminate cement, 25-30 parts of complex magnesium-aluminum binder, 8-12 parts of coagulant, 0.3-0.8 parts of dispersant, 0.5-1 parts of sintering aid, 1.5-2.5 parts of reinforcing fiber; The raw materials for preparing the complex magnesium-aluminum binder include the following components in parts by mass: 27-41 parts of magnesium oxide, 36-50 parts of aluminum oxide, 15-22 parts of organic carboxylic acid complexing agent, and 2-4 parts of coordination regulating agent.

3. The cement-complexed magnesium-aluminum composite binder according to claim 1, characterized in that: The coagulant is sodium silicate; The dispersant is a polycarboxylate water reducer; The sintering aid is lithium borate; The reinforcing fiber is basalt fiber; The organic carboxylic acid complexing agent is one or a combination of citric acid, tartaric acid and gluconic acid.

4. The cement-complexed magnesium-aluminum composite binder according to claim 1, characterized in that: The molar ratio of magnesium oxide to aluminum oxide is 1.5 to 2.5:1; Carboxylic acid and Mg in organic carboxylic acid complexing agents 2+ The molar ratio is 1:1~3; The mass ratio of aluminate cement to complex magnesium-aluminum binder is 1.8~2.7:

1.

5. The cement-complexed magnesium-aluminum composite binder according to claim 3, characterized in that: The molecular weight of polycarboxylate water reducer is 5000~10000; The particle size of lithium borate is <10 μm; The length of basalt fiber is 3~6 mm and the diameter is 10~15μm.

6. A carbon-free machine-pressed wall brick, characterized in that: The raw materials for its preparation include the following components in parts by mass: 36-46 parts of plate-shaped corundum, 38-42 parts of white corundum, 2-4 parts of magnesia, 5-6 parts of alumina powder, 0.3 part of silicon powder, 5-7 parts of fused magnesium-aluminum spinel, 0.8 part of glucose, and 3.5-4.5 parts of the cement-complexed magnesium-aluminum composite binder according to any one of claims 1 to 5.

7. The carbon-free machine-pressed wall brick according to claim 6, characterized in that: Tabular corundum includes tabular corundum with a particle size of 6~3mm and tabular corundum with a particle size of 3~1mm. The mass ratio of tabular corundum with a particle size of 6~3mm and tabular corundum with a particle size of 3~1mm is 1:1~3. The alumina content in the tabular corundum is ≥99wt%; White corundum includes white corundum with a particle size of 1~0.074mm and white corundum with a particle size of 325 mesh. The mass ratio of white corundum with a particle size of 1~0.074mm and white corundum with a particle size of 325 mesh is 1~3:

1. The alumina content in white corundum is ≥99wt%; The magnesia is large crystalline magnesia; the magnesia includes magnesia with a particle size of 1 to 0.074 mm and magnesia with a particle size of 200 mesh, and the mass ratio of the magnesia with a particle size of 1 to 0.074 mm and the magnesia with a particle size of 200 mesh is 1:1 to 3; the magnesium oxide content in the magnesia is ≥96.5wt%; The particle size of the alumina powder is ≤1μm, and the alumina content in the alumina powder is ≥99wt%; The silicon dioxide content in silicon micropowder is ≥95wt%; The particle size of the fused magnesia-alumina spinel is 325 mesh, and the alumina content in the fused magnesia-alumina spinel is ≥75wt%.

8. A method for preparing carbon-free machine-pressed wall bricks according to claim 6 or 7, characterized in that: The following steps are involved: The raw materials for preparing the carbon-free machine-pressed wall bricks are mixed, then placed into a mold, and subjected to heat treatment to obtain the carbon-free machine-pressed wall bricks.

9. The preparation method according to claim 8, characterized in that: The heat treatment temperature is 160° C. to 200° C., and the time is 16 hours to 20 hours.