US-12617721-B2 - Method for preparing cementing material by sintering activation of coal gangue

US12617721B2US 12617721 B2US12617721 B2US 12617721B2US-12617721-B2

Abstract

A method for preparing a cementing material by sintering and activating coal gangue is provided. The method includes the following steps: (1) crushing coarse-grained coal gangue to predetermined particle size; (2) fully and evenly mixing the crushed coal gangue, the composite additive and water according to a set proportion, and granulating the obtained mixture; (3) distributing, igniting and exhausting the granulated pellets in the sintering machine to obtain decarburized coal gangue sinter; (4) cooling the decarburized coal gangue sinter in a cooler; (5) crushing and finely grinding the cooled coal gangue sinter to obtain a coal gangue active mixture; and (6) mixing the coal gangue active admixture, the fly ash, the quicklime and the gypsum according to a predetermined ratio, and then carrying out injection moulding, mold removal and curing to obtain the coal gangue-based cementitious material.

Inventors

Zhengqi GUO
Jian Pan
Deqing ZHU
Congcong YANG
SIWEI LI
Qihou LI

Assignees

CENTRAL SOUTH UNIVERSITY

Dates

Publication Date: 20260505
Application Date: 20230831

Claims (10)

1 . A method for preparing a cementitious material by a sintering activation of a coal gangue, comprising following steps: (1) a pretreatment: crushing a coarse-grained coal gangue to a predetermined particle size to obtain a crushed coal gangue; (2) batching, mixing and granulating: fully mixing the crushed coal gangue obtained in step (1), a composite additive, and water according to a set proportion to obtain a first resulting mixture and granulating the first resulting mixture to obtain granulated pellets; (3) a sintering activation: distributing, igniting and exhausting the granulated pellets obtained in step (2) in a sintering machine for the sintering activation to obtain a decarburized coal gangue sinter; (4) cooling: cooling the decarburized coal gangue sinter obtained in step (3) in a cooler to obtain a cooled coal gangue sinter; (5) crushing and grinding: crushing and finely grinding the cooled coal gangue sinter obtained in step (4) to obtain a coal gangue active admixture; (6) compounding: mixing the coal gangue active admixture obtained in step (5), a fly ash, a quicklime, and a gypsum according to a predetermined ratio to obtain a second resulting mixture, and then performing a mold injection, a mold removal, and a curing on the second resulting mixture to obtain a coal gangue-based cementitious material.
2 . The method for preparing the cementitious material by the sintering activation of the coal gangue according to claim 1 , wherein a fixed carbon content in the coarse-grained coal gangue of step (1) is 1.5%-5.5%.
3 . The method for preparing the cementitious material by the sintering activation of the coal gangue according to claim 1 , wherein in step (1), the coarse-grained coal gangue is crushed to 15 mm by a jaw crusher and then crushed to 8 mm by a roller crusher; subsequently, a high-pressure roller mill is configured for crushing until the crushed coal gangue with a particle size of 6.3 mm accounting for 65%-85% and the crushed coal gangue with a particle size of 0.5 mm accounting for 15%-25%; and a working pressure is 2.0-6.0 MPa in the crushing of the high-pressure roller mill.
4 . The method for preparing the cementitious material by the sintering activation of the coal gangue according to claim 1 , wherein in step (2), a granulation is carried out by using a cylinder granulator, and a rotating speed of the cylinder granulator is 30-60 rpm, a granulation time is 2-4 min; a water content sprayed in a granulation process is 1%-2%, and a water content of the granulated pellets obtained is controlled at 6.5%-7.5%.
5 . The method for preparing the cementitious material by the sintering activation of the coal gangue according to claim 1 , wherein a sintering method in step (3) is a belt sintering; in a distribution process of the belt sintering, a height of a material layer is controlled to be 500-2000 mm; a thickness of a bedding material is controlled to be 15-25 mm, and the coal gangue with a particle size of 15-20 mm is configured as the bedding material; in an ignition process of the belt sintering, an ignition time is 1-2 min; an ignition temperature is 1050-1150° C.; an ignition negative pressure is 4-6 KPa, a heat preservation temperature is 700-1000° C., a heat preservation time is 3-5 min, and a heat preservation negative pressure is 4-6 KPa; and in a sintering process of a belt draft, a sintering negative pressure is 10-18 KPa.
6 . The method for preparing the cementitious material by the sintering activation of the coal gangue according to claim 1 , wherein in step (4), a cooling method of the decarburized coal gangue sinter comprises one of a belt sintering machine cooling, an annular cooling, and a shaft furnace cooling.
7 . The method for preparing the cementitious material by the sintering activation of the coal gangue according to claim 6 , wherein a shaft furnace cooling device is adopted in a cooling process, and the shaft furnace cooling device comprises a shaft furnace body, and the shaft furnace cooling device further comprises a receiving system, a cooling system, and a discharging system sequentially arranged from a top to a bottom; the receiving system comprises a storage tank and a vibrating feeder; the storage tank is arranged above the vibrating feeder and configured for feeding from above the vibrating feeder, and a bottom end of the vibrating feeder is provided with a chute; a head end of the chute is connected to the storage tank, and a tail end of the chute is communicated with the shaft furnace body; and the tail end of the chute is provided with a baffle, and a height of the baffle is 3-8 cm.
8 . The method for preparing the cementitious material by the sintering activation of the coal gangue according to claim 7 , wherein the shaft furnace cooling device adopts a step-by-step cooling mode, and the shaft furnace cooling device sequentially comprises a primary cooling unit and a secondary cooling unit from a top to a bottom; the primary cooling unit comprises two groups of central hoods, wherein the two groups of central hoods are arranged up and down along a height direction, and each of the two groups of central hoods is provided with an air outlet; the primary cooling unit also comprises two fans symmetrically arranged on both sides of the shaft furnace body, each of the two fans is connected to three cold air pipes and an air inlet regulating valve is arranged at a joint of the two fans and the three cold air pipes; wherein a first cold air pipe and a second cold air pipe of the three cold air pipes are connected to the two groups of central hoods; a third cold air pipe of the three cold air pipes is arranged on a side of the shaft furnace body, and the side of the shaft furnace body is provided with a corresponding air outlet; a structure of the secondary cooling unit is consistent with a structure of the primary cooling unit; and an air supply system of the primary cooling unit is a dry-cooling blower with an air volume of 3,000-3,500 m 3 /t, and the dry-cooling blower is configured to perform a first-stage cooling on the decarburized coal gangue sinter for rapidly cooling and forming a high-temperature waste gas; an air supply system of the secondary cooling unit is a normal temperature blower with an air volume of 1,500-2,000 m 3 /t, and the normal temperature blower is configured to perform a second-stage cooling on the decarburized coal gangue sinter and form a low-temperature waste gas.
9 . The method for preparing the cementitious material by the sintering activation of the coal gangue according to claim 1 , wherein in step (5), the cooled coal gangue sinter is crushed to 3 mm by a toothed roller crusher, and then a specific surface area of a crushed coal gangue sinter is increased to 500-700 m 2 /kg by combining a high-pressure roller mill and a ball mill to obtain a coal gangue active mixture with a set fineness and specific surface area; in step (6), in raw materials of the coal gangue-based cementitious material, mass percentages of the coal gangue active admixture, the fly ash, the quicklime, and the gypsum are 55%-75%, 10%-20%, and 5%-20%, respectively.
10 . The method for preparing the cementitious material by the sintering activation of the coal gangue according to claim 2 , wherein in step (1), the coarse-grained coal gangue is crushed to 15 mm by a jaw crusher and then crushed to 8 mm by a roller crusher; subsequently, a high-pressure roller mill is configured for crushing until the crushed coal gangue with a particle size of 6.3 mm accounting for 65%-85% and the crushed coal gangue with a particle size of 0.5 mm accounting for 15%-25%; and a working pressure is 2.0-6.0 MPa in the crushing of the high-pressure roller mill.

Description

CROSS REFERENCE TO THE RELATED APPLICATIONS This application is based upon and claims priority to Chinese Patent Application No. 202211054213.3, filed on Aug. 31, 2022, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to the field of comprehensive utilization of solid waste, in particular to the method for preparing cementing material by sintering activation of coal gangue. BACKGROUND Coal gangue is a type of solid waste created during the mining, washing, processing, and usage of coal. Its main components are Al2O3, SiO2, etc. in the form of minerals such as kaolinite and quartz. China's coal resources are very abundant, and the energy structure is mainly coal. The yield of coal gangue is about 5%-20% of coal mining, so the output of coal gangue is particularly high. More than 8 billion tons of coal gangue have been accumulated in China, covering an area of more than 110,000 hectares, with more than 1,100 coal gangue storage mountains, and coal gangue emissions are still growing rapidly. Since the main components of coal gangue are SiO2 and Al2O3, it is similar to building materials. Therefore, one of the important ways to attain widespread consumption and application of coal gangue is to figure out how to use it as a building material (such as cementitious material). If coal gangue is used to prepare building materials such as cement admixture, appropriate methods must be used to increase its activity and reduce organic matter in coal gangue, such as residual carbon. An important technique for decarburizing and activating coal gangue is high-temperature thermochemical activation, which primarily uses the roasting and sintering methods of rotary kilns. The Chinese patent CN1236748A releases a process for calcining coal gangue to create activated cement mixture. The method uses a straightforward kiln, an oxidation atmosphere, and calcination temperatures controlled between 850 and 1150° C. to prepare coal gangue into activated cement mixture. However, despite the process is simple, the rotary kiln has a number of issues, including its circumference, high energy consumption, and difficulty controlling environmental pollution. The Chinese patent CN110078401B discloses a process for producing active mixed materials by band-type sintering of coal gangue. The Chinese patent CN113526883A discloses a coal-free self-heating ultra-high material layer decarbonization process. The Chinese patent CN113526895B discloses a method for coal gangue double-layer oxygen-enriched sintering and decarburization. All of these techniques use the sintering process to roast, decarburize, and activate the coal gangue to increase its activity. Among the disclosed techniques for preparing active mixtures from coal gangue that active mixtures can be made by separating, such as belt sintering and rotary kiln calcination. However, the two processes are calcined and decarburized, and the sintering utilization coefficient is not great, with the highest being only 1.48 t/(m2h), and the activity index of the combination is less than 90°/%, limiting its further application. Among the prior art is the Chinese patent CN106966620A, which discloses a cementitious material made of coal gangue bottom slag, fly ash, and a method of preparing it. The components of the cementitious material have the following weight percentage contents: coal gangue bottom slag 10-35%, fly ash 25-55%, quicklime 5-50%, gypsum 8-12%. Coal gangue bottom slag is the byproduct of coal gangue combustion in coal gangue power plants after 800-1000° C. Due to the low activity of coal gangue bottom slag, the maximum addition ratio is only 35%, making it impossible to use in cementitious materials with high proportions and big scales. SUMMARY Aiming at the technical problem of “coal gangue has poor activity effect and low sintering utilization coefficient, so it cannot be applied to cementitious materials in a high proportion” in the previous art. The goal of this prevent invention is to provide the method for preparing cementing material by sintering activation of coal gangue to improve the activity of coal gangue mixture and its proportion in cementitious materials, allowing coal gangue to be used on a large scale and for a high value. The objective of the present disclosure is achieved by using the following technical solution: The method for preparing cementing material by sintering activation of coal gangue, wherein it includes the following steps: (1) Pretreatment: Coarse-grained coal gangue is crushed to a predetermined particle size;(2) Ingredients, mixing and granulation: The crushed coal gangue, composite additive, and water obtained in step (1) are fully mixed according to the predetermined ratio, and the resulting mixture is then granulated to obtain granulation pellets;(3) Sintering activation: The pellets obtained in step (2) are distributed, ignited, exhausted and sintered in the sintering machine to o