WO2024114239A1

WO2024114239A1 - Physically modified fly ash and preparation method therefor

Info

Publication number: WO2024114239A1
Application number: PCT/CN2023/128037
Authority: WO
Inventors: 朱文尚; 马海军; 马兆模; 王行钦; 骆铭阳; 吴红安; 傅瀚葵; 邹昕妍
Original assignee: 孙志胜
Priority date: 2022-11-28
Filing date: 2023-10-31
Publication date: 2024-06-06
Also published as: CN116003012A

Abstract

A physically modified fly ash and a preparation method therefor. The obtained physically modified fly ash has a glass microbead perfectness ratio ≥ 80%, a circularity degree ≥ 0.85, a length-to-diameter ratio ≤ 1.30, and particle size characteristic parameters D50 ≤ 15.00 μm and D90 ≤ 45.00 μm. The device and the matched preparation method greatly reduces energy consumption; and the prepared physically modified fly ash glass microbeads remain intact, and have a more rational particle size distribution, which is closer to a Fuller curve, which is beneficial for improving the stacking density, reducing the water demand ratio, and improving the activity.

Description

Physically modified fly ash and preparation method thereof

Technical Field

The invention relates to the technical field of fly ash, and in particular to physically modified fly ash and a preparation method thereof.

Background technique

Fly ash refers to the powder collected from the flue gas of the boiling coal powder furnace of a thermal power plant. Due to the morphological effect, activity effect and micro-aggregate effect (commonly known as the "three major effects") of fly ash particles, it is widely used in cement concrete and other projects, and in some places there is even a situation of supply exceeding demand. The annual output of fly ash in my country is about 600 million tons, and the utilization rate is about 70%. Some fly ashes cannot be used due to reasons such as too coarse particles and low activity. Therefore, improving its utilization rate by studying physical modification of fly ash is an important way to improve the comprehensive utilization rate of fly ash.

technical problem

Physical modification of fly ash is mainly achieved through mechanical grinding. At present, fly ash is mainly ground by ball mills. Although the fineness can be reduced, the grinding medium is steel balls. The strong impact force destroys the fly ash glass beads, and the particle size distribution is unreasonable, which affects its role in cement concrete. In addition, the power consumption of grinding is high. Therefore, it is crucial to improve the particle size distribution and particle morphology while reducing the fineness of fly ash, improve the activity of fly ash, and reduce energy consumption.

Technical Solutions

In order to solve the above-mentioned existing technical problems, the present invention provides a physically modified fly ash and a preparation method thereof, which can significantly improve the intrinsic quality of fly ash products, reduce energy consumption, and improve concrete working performance.

In order to achieve the above object, the technical solution adopted by the present invention is:

In a first aspect, the present invention provides a physically modified fly ash, wherein the intact rate of the fly ash glass beads is ≥80%.

The intact rate of glass beads is the ratio of the content of glass beads after physical modification to the content of glass beads before modification. The content of glass beads is determined by electron microscopy or optical microscopy.

Beneficial Effects

The beneficial effects of the present invention are that the physically modified fly ash glass microspheres are kept intact to the maximum extent, the strength activity index can be improved, and the water demand ratio of the fly ash is reduced. The strength activity index is improved and the physically modified fly ash is used in concrete, which is beneficial to improving the working performance of the concrete.

Optionally, the physically modified fly ash has a circularity of ≥0.85 and an aspect ratio of ≤1.30.

The circularity is the ratio of the circumference of a circle with the same area as the particle's projection to the circumference of the particle's projection; the aspect ratio is the ratio of the length to the width of the smallest circumscribed rectangle of the particle's projection. The circularity and aspect ratio are measured and calculated using an electron microscope or an optical microscope.

From the above description, it can be seen that by limiting the aspect ratio and circularity of fly ash and improving the morphology of fly ash particles, the water demand ratio can be further reduced and the intrinsic quality of fly ash products can be improved.

Optionally, the particle size characteristic parameters of the physically modified fly ash are D50≤15.00 μm and D90≤45.00 μm.

From the above description, it can be seen that by limiting the fly ash particle size, the fly ash particle size distribution becomes more reasonable and closer to the Fuller curve. Better particle morphology helps to further increase the packing density and the strength activity index, thereby further significantly improving the intrinsic quality of the fly ash product.

In a second aspect, the present invention provides a method for preparing physically modified fly ash, wherein the preparation scheme adopts a novel energy-saving dry vertical grinding mill process system to grind the material, and the grinding medium is corundum balls.

During this preparation method, the surface of the physically modified fly ash powder particles is smooth and uniform, with a small friction temperature rise, less energy, and small surface energy, which can reduce the agglomeration of the powder particles and make it easy to mix evenly with other powders. The energy consumption of this preparation method is greatly reduced, which is at least half of the power consumption of ball mill grinding.

Among them, the technical effect corresponding to the preparation method of a physically modified fly ash provided in the second aspect refers to the relevant description of a fly ash provided in the first aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of an open circuit process according to an embodiment of the present invention;

FIG2 is a schematic diagram of a closed-circuit process according to an embodiment of the present invention;

[Description of Reference Numerals]

1. Rotor scale; 2. Batching bin; 3. Elevator; 4. Air chute; 5. Vertical grinder; 6. Spiral reamer scale; 7. Finished product warehouse; 8. Dust collector; 9. High-efficiency powder classifier.

Best Mode for Carrying Out the Invention

In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

The physically modified fly ash of the present invention has a glass microbead intact rate of ≥80%, which is beneficial to reducing the water demand ratio of the fly ash. The physically modified fly ash is used in concrete, which is beneficial to improving the working performance of the concrete.

At the same time, in this embodiment, the circularity of the physically modified fly ash is ≥0.85 and the aspect ratio is ≤1.30, thereby improving the morphology of fly ash particles, further reducing the water demand ratio, and improving the intrinsic quality of the fly ash product.

Correspondingly, in the prior art, the 45 μm square hole sieve residue of fly ash on Class I ash, Class II ash and Class III ash is ≤12.0, ≤30.0 and ≤45.0 respectively. However, the particle size characteristic parameters of the physically modified fly ash particles in this embodiment are D50≤15.00 μm and D90≤45.00 μm. Therefore, the fineness in this embodiment is significantly reduced, and it is more scientific to characterize using the median particle size, and the fineness of the fly ash is more appropriate.

The specific preparation method of the above-mentioned physically modified fly ash includes:

The preparation method adopts a new type of dry energy-saving vertical grinding machine 5 to grind the material, and the grinding medium is corundum ball, which greatly reduces energy consumption. The preparation process adopts two methods: open circuit or closed circuit.

Open circuit process: fly ash raw ash is transported through batching bin 2 and rotor scale 1, and then transported to vertical grinder 5 by elevator 3 and air chute 4 for grinding and shaping. Qualified products are transported through spiral reamer scale 6 and then enter finished product warehouse 7. The process diagram is shown in Figure 1.

Closed-circuit process: fly ash raw ash is transported by rotor scale 1 through batching bin 2, and then transported to vertical grinding machine 5 by elevator 3 and air chute 4 for grinding and shaping. The product is output to high-efficiency powder classifier 8 for powder selection through spiral reamer scale 6, and then qualified products are obtained through dust collector 9. Qualified products are transported to finished product warehouse 7 after metering, and unqualified products are returned to the mill for further grinding and shaping. The process diagram is shown in Figure 2.

Example

A physically modified fly ash, with a glass bead integrity rate of 90%, a roundness of 0.88, an aspect ratio of 1.25, and particle size characteristic parameters D50 of 10.59 μm and D90 of 36.32 μm.

The specific preparation method is described above.

Example

The difference between this embodiment and the first embodiment is that the limiting parameters for fly ash are different.

A physically modified fly ash, with a glass bead integrity rate of 85%, a roundness of 0.87, an aspect ratio of 1.27, and particle size characteristic parameters D50 of 11.81μm and D90 of 43.53μm.

Example

A physically modified fly ash, with a glass bead integrity rate of 82%, a roundness of 0.86, an aspect ratio of 1.28, a median particle size D50 of 12.99 μm, and a D90 of 42.24 μm.

Example

A physically modified fly ash, with a glass bead integrity rate of 80%, a roundness of 0.85, an aspect ratio of 1.30, a median particle size D50 of 15.00 μm, and a D90 of 45.00 μm.

Comparative Example 1

The difference between the comparative example and the first embodiment is that the fly ash is physically modified by a ball mill, the glass beads have a completeness rate of 62%, a circularity of 0.86, an aspect ratio of 1.28, a median particle size D50 of 12.03 μm, and a D90 of 44.31 μm.

Comparative Example 2

The difference between the comparative example and the first embodiment is that the fly ash is physically modified by a ball mill, the glass beads have a good rate of 81%, a circularity of 0.82, an aspect ratio of 1.37, a median particle size D50 of 14.21 μm, and a D90 of 44.23 μm.

Comparative Example 3

The difference between the comparative example and the first embodiment is that the fly ash is physically modified by a ball mill, the glass beads have a good rate of 82%, a circularity of 0.86, an aspect ratio of 1.29, a median particle size D50 of 15.72 μm, and a D90 of 46.51 μm.

The product properties of the above-mentioned embodiments 1 to 4 and comparative examples 1 to 3 are shown in Table 1.

Table 1

As can be seen from Table 1 above, according to Examples 1 to 4 and Comparative Example 1, when the intact rate of physically modified fly ash glass microspheres is ≥80%, its strength activity index is high, and the fly ash water requirement ratio is high. Similarly, according to Examples 1 to 4 and Comparative Example 2, when the aspect ratio and circularity of physically modified fly ash are within a limited range, the water requirement ratio can be further reduced, and the intrinsic quality of the fly ash product can be improved. According to Examples 1 to 4 and Comparative Example 3, when the particle size of physically modified fly ash is within a limited range, the fly ash particle size distribution is more reasonable, and therefore, the strength activity index can be improved, thereby further significantly improving the intrinsic quality of the fly ash product.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

A physically modified fly ash, characterized in that the intact rate of glass microspheres in the fly ash after physical modification is ≥80%.
The physically modified fly ash according to claim 1 is characterized in that the fly ash has a circularity of ≥0.85 and an aspect ratio of ≤1.30.
The physically modified fly ash according to claim 2 is characterized in that the fly ash particle size characteristic parameters D50≤15.00μm and D90≤45.00μm.
A preparation method of physically modified fly ash is characterized in that: the preparation method adopts a new energy-saving dry vertical grinding machine process system to grind and shape the material, and the grinding medium is corundum ball, which greatly reduces energy consumption.