Porous gradient reinforced ceramsite based on coal gangue and preparation method thereof

Abstract

The invention discloses porous gradient reinforced ceramsite based on coal gangue and a preparation method thereof, the ceramsite has a three-level gradient pore structure of macropores, mesopores and micropores, lithium aluminosilicate gel is generated through red mud-lithium silicate synergistic reaction under the autoclaved condition of less than or equal to 220 DEG C, and magnesium phosphate cement is adopted for wrapping to realize heavy metal solidification. The cylinder compressive strength of the obtained ceramsite is greater than or equal to 8MPa, the density is less than or equal to 700kg / m < 3 >, the water absorption is less than or equal to 5%, and The technical problems that light weight and high strength of traditional coal gangue ceramsite are difficult to consider at the same time, and high-temperature sintering pollution is large are solved.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization and building materials, and in particular to a porous gradient-reinforced ceramsite based on coal gangue and a preparation method thereof. Background Art

[0002] Gangue, the primary solid waste from coal mining, produces over 700 million tons annually. Traditional disposal methods, such as landfills and stockpiles, not only occupy land but also release harmful substances through weathering and spontaneous combustion. One of the primary technical solutions for its resource utilization is to convert gangue into ceramsite. Current technologies for producing gangue ceramsite fall into two main categories: one is high-temperature sintering, which uses calcination at 1100-1250°C and relies on the combustion of the gangue's own carbon. While this method can achieve high strength, such as a cylinder compressive strength of 6MPa-10MPa, it suffers from high energy consumption and severe sulfide volatilization pollution. The other is chemical coating, such as that described in patent CN117720291A, which uses alkaline solutions and water glass for modification. While this method reduces the sintering temperature, it only improves surface properties, leaving the core porosity as high as 30%-40%, resulting in high water absorption. Furthermore, existing technologies often suffer from a conflict between pore structure and strength: high-porosity ceramsite has low strength, while high-strength ceramsite often has high density, making it difficult to achieve both lightness and high strength. Therefore, it is necessary to propose a porous gradient-reinforced ceramsite based on coal gangue and its preparation method to address this issue. Summary of the Invention

[0003] The purpose of the present invention is to address the shortcomings of the existing technology and provide a porous gradient reinforced ceramsite based on coal gangue and a preparation method thereof, so as to solve the problem that the existing coal gangue ceramsite preparation technology is difficult to achieve both light weight and high strength.

[0004] In the first aspect, the present invention provides a porous gradient reinforced ceramsite based on coal gangue, comprising: a three-level gradient pore structure of macropores, mesopores and micropores, wherein the diameter of the macropores is 100 μm-300 μm, the diameter of the mesopores is 10 μm-50 μm, the diameter of the micropores is less than 1 μm, the cylinder pressure strength is ≥8 MPa, and the density is ≤700 kg / m 3 .

[0005] Furthermore, the surface coating layer is magnesium phosphate cement with a water absorption rate of ≤5%.

[0006] In a second aspect, the present invention provides a method for preparing the above-mentioned porous gradient reinforced ceramsite based on coal gangue, comprising the following steps:

[0007] Step 1: Grind the coal gangue with 15%-20% red mud until the specific surface area is ≥600m 2 / kg;

[0008] Step 2: Add 5%-8% lithium silicate solution to form a slurry;

[0009] Step 3: Add 0.5%-1% aluminum powder and 0.2%-0.5% H2O in stages v foaming agent;

[0010] Step 4: autoclave at 1.0-1.5 MPa and 180-220° C. for 8-10 hours;

[0011] Step 5: immerse the surface in 5% magnesium phosphate solution for surface modification.

[0012] The present invention has the following beneficial effects: the present invention provides a porous gradient reinforced ceramsite based on coal gangue and a preparation method thereof, and the lightweight and high-strength ceramsite prepared by gradient pore structure design and chemical bonding enhancement process solves the problem of light weight and high strength of the material, and solves the problem of heavy metal leaching by supplementing the curing agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 The present invention is a flow chart of the preparation method of the porous gradient reinforced ceramsite based on coal gangue. DETAILED DESCRIPTION

[0015] It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present application may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs.

[0016] The embodiment of the present invention provides a porous gradient reinforced ceramsite based on coal gangue, comprising a three-level gradient pore structure of macropores, mesopores and micropores, wherein the macropore diameter is 100 μm-300 μm, the mesopore diameter is 10 μm-50 μm, the micropore diameter is less than 1 μm, the cylinder pressure strength is ≥8 MPa, and the density is ≤700 kg / m 3 The surface coating of ceramsite is magnesium phosphate cement with a water absorption rate of ≤5%.

[0017] Through controlled foaming and directional solidification, a three-level gradient pore system of "macropore (100μm~300μm)-mesopore (10μm~50μm)-micropore (<1μm)" is formed inside the ceramsite, ensuring lightness and a density of ≤700kg / m3 , and the skeleton strength is enhanced through micropores.

[0018] See also Figure 1 The preparation method of the porous gradient reinforced ceramsite based on coal gangue comprises the following steps:

[0019] Step 1: Grind the coal gangue with 15%-20% red mud until the specific surface area is ≥600m 2 / kg;

[0020] Step 2: Add 5%-8% lithium silicate solution to form a slurry;

[0021] Step 3: Add 0.5%-1% aluminum powder and 0.2%-0.5% H2O in stages v foaming agent;

[0022] Step 4: autoclave at 1.0-1.5 MPa and 180-220° C. for 8-10 hours;

[0023] Step 5: immerse the surface in 5% magnesium phosphate solution for surface modification.

[0024] The present invention utilizes the synergistic reaction of red mud and lithium silicate to generate lithium aluminum silicate gel (LAS) at low temperature, for example, ≤200°C. The bond energy of LAS is 30% higher than that of traditional CSH gel, which significantly improves the strength of the ceramsite body.

[0025] The present invention introduces magnesium phosphate cement to coat the coal gangue particles, and forms heavy metal phosphate minerals such as Pb3(PO4)2, so that the heavy metal leaching concentration is lower than the limit of GB 5085.3-2007 by more than 50%.

[0026] The following is a specific embodiment of the preparation method of porous gradient reinforced ceramsite based on coal gangue:

[0027] Example 1

[0028] 1. Preparation steps:

[0029] 1. Take the washed gangue (carbon content 8%) from a coal mine and crush it to ≤2mm;

[0030] 2. Mix gangue and red mud in a mass ratio of 85:15 and grind to a specific surface area of ≥600m 2 / kg;

[0031] 3. Add 6% lithium silicate solution with a modulus of 1.8 and mechanically stir for 30 minutes to form a uniform slurry;

[0032] 4. First add 0.8% aluminum powder and stir for 10 minutes, then add 0.3% H2O2 and stir for 5 minutes, then immediately inject into the mold;

[0033] 5. Autoclave at 1.2 MPa and 200°C for 9 hours, then cool naturally to 60°C and remove from the autoclave;

[0034] 6. Soak in 5% magnesium phosphate solution for 1 hour and dry at 80℃ to constant weight.

[0035] Table 1 Performance test results of Example 1

[0036] index Test results Cylinder pressure strength (MPa) 9.2 <![CDATA[Bulk density (kg / m 3 )]]> 680 Pb leaching (mg / L) 0.08

[0037] Example 2

[0038] 1. Preparation steps:

[0039] 1. Take the excavation waste of a coal mine (carbon content 3%) and crush it to ≤1mm;

[0040] 2. Mix gangue and red mud in a mass ratio of 80:20 and grind to a specific surface area of ≥700m 2 / kg; 3. Add 8% lithium silicate solution with a modulus of 2.0 and ultrasonically disperse for 20 minutes;

[0041] 4. First add 0.5% aluminum powder and stir for 8 minutes, then add 0.2% H2O2 and stir for 5 minutes;

[0042] 5. Autoclave at 1.5 MPa and 220°C for 10 h, then reduce the pressure stepwise (1 h to normal pressure); 6. Vacuum impregnate with 8% magnesium phosphate solution for 2 h, and dry at 80°C to constant weight.

[0043] Table 2 Performance test results of Example 2

[0044] index Test results Cylinder pressure strength (MPa) 12.5 <![CDATA[Bulk density (kg / m 3 )]]> 850 Pb leaching (mg / L) 0.05

[0045] Example 3

[0046] 1. Preparation steps:

[0047] 1. Take the washed gangue (carbon content 5%) from a coal mine and crush it to ≤1.5mm;

[0048] 2. Mix gangue and red mud in a mass ratio of 75:25 and grind to a specific surface area of ≥650m 2 / kg; 3. Add 5% lithium silicate solution with a modulus of 1.5 and stir until the viscosity reaches 1500 cP;

[0049] 4. Simultaneously add 1.2% aluminum powder and 0.6% H2O2 and stir at high speed (800 rpm) for 10 minutes;

[0050] 5. Autoclave at 1.0 MPa and 180°C for 12 h, followed by rapid decompression (30 min);

[0051] 6. Spray with 4% magnesium phosphate solution and dry at 60℃ for 4h.

[0052] Table 3 Performance test results of Example 3

[0053] index Test results Cylinder compressive strength (MPa) 5.8 <![CDATA[Bulk density (kg / m 3 )]]> 550 Pb leaching (mg / L) 0.12

[0054] Example 4

[0055] 1. Preparation steps:

[0056] 1. Take the washed gangue (carbon content 6%) from a coal mine and crush it to ≤2mm;

[0057] 2. Mix the coal gangue and red mud in a mass ratio of 88:12 and grind to a specific surface area of ≥500m 2 / kg;

[0058] 3. Add 5% sodium silicate solution with a modulus of 1.2 and mechanically stir for 25 minutes to form a uniform slurry;

[0059] 4. First add 0.3% aluminum powder and stir for 8 minutes, then add 0.1% H2O2 and stir for 4 minutes;

[0060] 5. Autoclave at 0.8 MPa and 180°C for 10 hours, then cool naturally to 60°C and remove from the autoclave;

[0061] 6. Soak in 3% magnesium phosphate solution for 1 hour and dry at 80℃ to constant weight.

[0062] Table 4 Performance test results of Example 4

[0063] index Test results Cylinder pressure strength (MPa) 6.8 <![CDATA[Bulk density (kg / m 3 )]]> 700 Pb leaching (mg / L) 0.15

[0064] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0065] It should be noted that the terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the present application described herein can, for example, be implemented in an order other than that illustrated or described herein.

[0066] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A porous gradient reinforced ceramsite based on coal gangue, characterized in that: include: The three-level gradient pore structure of macropore, mesopore and micropore, the diameter of the macropore is 100μm-300μm, the diameter of the mesopore is 10μm-50μm, the diameter of the micropore is less than 1μm, the cylinder pressure strength is ≥8MPa, and the density is ≤700kg / m 3 .

2. The porous gradient reinforced ceramsite based on coal gangue according to claim 1, characterized in that: The surface coating is magnesium phosphate cement with a water absorption rate of ≤5%.

3. A method for preparing porous gradient reinforced ceramsite based on coal gangue according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: Grind the coal gangue with 15%-20% red mud until the specific surface area is ≥600m 2 / kg; Step 2: Add 5%-8% lithium silicate solution to form a slurry; Step 3: Add 0.5%-1% aluminum powder and 0.2%-0.5% H2O2 foaming agent in stages; Step 4: autoclave at 1.0-1.5 MPa and 180-220° C. for 8-10 hours; Step 5: immerse the surface in 5% magnesium phosphate solution for surface modification.

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