AU2019101452A4

AU2019101452A4 - Utilization method of red mud

Info

Publication number: AU2019101452A4
Application number: AU2019101452A
Authority: AU
Inventors: Yujing Jiang
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-11-26
Filing date: 2019-11-26
Publication date: 2020-01-16
Anticipated expiration: 2027-11-26

Abstract

The present invention discloses a utilization method of red mud, and relates to a comprehensive utilization method of red mud waste generated in an aluminum oxide production process. The method comprises the following steps: (1) filter-pressing red mud; (2) crushing fly ash slag; (3) mixing the filter-pressed red mud in step (1) with the crushed fly ash slag in step (2), and adding asphalt for kneading; (4) molding a kneaded material in step (3); and (5) sintering a molded material in step (4). A product obtained in the method of the present invention can be applied to reclamation engineering, seawall construction, island reef construction, desert treatment, river embankment construction, slope protection construction, parks, streets, roads, and thermal insulation, and the like, and can save huge building material resources, thereby opening up an effective way for the comprehensive utilization of red mud.

Description

UTILIZATION METHOD OF RED MUD

TECHNICAL FIELD

The present invention discloses a utilization method of red mud, and relates to a comprehensive utilization method of red mud waste generated in an aluminum oxide production process.

BACKGROUND

Red mud is solid waste with extremely fine particles, strong alkalinity and specific radioactivity that is produced in the process of producing aluminum oxide from bauxite. China is the world's largest producer of aluminum oxide, and produced 58.98 million tons of aluminum oxide and 70 million tons of red mud in 2015. China has produced approximately a total of 520 million tons of red mud, but the utilization rate of red mud is less than 5%.

Due to different production processes of bauxite and aluminum oxide, properties of red mud produced are also different. Generally, red mud produced in producing aluminum oxide by the Bayer process is referred to as Bayer red mud. Red mud produced in producing aluminum oxide by using a sintering method and red mud produced in producing aluminum oxide by a combination of a sintering method and the Bayer process is respectively referred to as sintering red mud and combined red mud.

Chemical components of red mud are roughly provided in the following table:

Unit: %

Component	Silicon oxide	Ferric oxide	Aluminum oxide	Calcium oxide	Titanium oxide	Sodium oxide	Others
Sintering red mud	16-21	7-10	8-12	33-38	2-5	2.9-3.5	11-27
Bayer red mud	13-18	12-33	19-22	3-21	2-5	5-8	11-22
Combined red mud	18-20	6-10	5-14	33-47	4-5	2.8-4.4	12-14

Red mud contains approximately 3%-14% of alkali metal oxides, and most of them are weakly alkali and half-free alkali. Main chemical components of the sintering red mud are silicon oxide and calcium oxide, accounting for approximately 50% of the total red mud. Chemical components of the Bayer red mud have characteristics of high sodium content, low content of calcium oxide, and relatively high iron content.

A particle size of red mud is roughly as follows:

2019101452 26 Nov 2019

Type	Particle size (mm) percentage %
2-0.5	0.5-0.25	0.25-0.075	0.075-0.005	,<0.005
Sintering red mud	14.37	38.14	30.2	14.23	2.79
Bayer red mud			2.10	46.73	51.17

Radioactive detection results of red mud are roughly as follows:

Unit: Bq/kg

Type	Uranium	Thorium	Radium	Potassium
Sintering red mud	460	454	420	593
Bayer red mud	281-362	406-491	361-605	196-317
Combined red mud	424	474	363	436
Bauxite	297-313	314-344	312-356	262-313

There is no ready-made standard in China. In Russian cement, no more than 740 Bq/kg is allowed and no more than 370 Bq/kg is generally allowed in special cement not used for building houses, public and productive buildings.

The moisture content of red mud filter-press material is generally 25%-35%.

As red mud produced in the production of aluminum oxide, red mud has the following main hazards: (1) a large amount of land resources are needed to pile up red mud. At present, the annual discharge of red mud in China reaches up to 80 million tons, which covers approximately an area of 712 hectares according to a stockpiling height of 10 meters. If the red mud is stockpiled for 10 years, and construction costs and maintenance costs of a storage yard are calculated at 10 yuan per ton per year, only the construction costs and maintenance costs will be 8 billion yuan. (2) Alkali liquor in red mud and dust from the storage yard cause increasingly serious pollution to the surrounding environment. Red mud has become an important pollution source that endangers the regional environment, and seriously affects the ecological balance and the sustainable development of human beings. (3) A red mud storage technology is difficult and has high costs and hidden trouble. Sintering red mud and combined red mud can be dammed and stockpiled by using a wet method according to their own coagulation characteristics, but it is difficult to resolve a problem of rapid stockpiling of a large amount of red mud, and a loss caused by dam break is huge. Bayer red mud generally needs to be stockpiled by using a dry method. The red mud needs large space of a storage

2019101452 26 Nov 2019 yard after being subject to dehydration, transportation, tedding, compaction, and other processes, and stockpiling and maintenance costs are high. (4) A comprehensive utilization technology of red mud is a worldwide problem. Due to the existence of alkali, the influence of radioactivity, the influence of costs, and the like, the problem of comprehensive utilization of red mud has not been fundamentally resolved so far. (5) There are radioactive hazards. After an aluminum oxide production process is conducted by using bauxite, radioactive substances in produced red mud are enriched, which brings certain harm to the environment and people's health.

At present, comprehensive utilization of red mud is a worldwide problem, and most foreign countries adopt stockpiling and reclamation. After more than 60 years of research and development, China has made some progress, such as iron extraction of Bayer red mud, baking-free brick, sintered ceramsite, road construction, land filling, microcrystalline glass, and desulfurizer, but in general, there is still no fundamental solution. At present, the utilization rate of red mud in China is less than 5%, which needs to be resolved urgently.

SUMMARY

An objective of the present invention is to provide a utilization method of red mud in view of deficiency in the foregoing existing technologies, which can effectively resolve a problem of longterm and effective consolidation of alkali substances infiltrated or attached to red mud, has good effects of consolidating alkali and preventing alkali infiltration, and does not cause harm to underground and overground environments.

The objective of the present invention is achieved according to the following technical solution:

A utilization method of red mud is provided, including the following steps:

(1) filter-pressing red mud;

(2) crushing fly ash slag:

(3) mixing the filter-pressed red mud in step (1) with the crushed fly ash slag in step (2), and adding asphalt for kneading; and (4) conducting vibration molding or extrusion on a kneaded material in step (3) to obtain molded building material blocks.

In the utilization method of red mud of the present invention, after vibration molding or extrusion is conducted on the kneaded material to obtain the molded building material blocks, the molded building material blocks are sintered.

In the utilization method of red mud of the present invention, moisture content of the filter4

2019101452 26 Nov 2019 pressed red mud in step (1) is l%-39%.

In the utilization method of red mud of the present invention, a particle size of the crushed fly ash slag in step (2) is less than 110 mm.

In the utilization method of red mud of the present invention, a mixing ratio of the filter-pressed red mud in step (3) and the crushed fly ash slag in step (1) is 1:0-1:5, and an amount of asphalt added is 5%-35%.

In the utilization method of red mud of the present invention, sintering temperature of a material obtained through molding in step (4) is 300°C-1350°C, and sintering time of the material is 5 h-40 h.

In the utilization method of red mud of the present invention, based on long-term production practice, theoretical research, and scientific experiments, a principle of two negatives make a positive is fully utilized, red mud waste generated in an aluminum oxide production process and waste such as fly ash slag generated in power generation of thermal power plants are used as aggregates, asphalt generated in the coal chemical industry or petrochemical industry is used as a binder, and these materials are subject to kneading, molding, and other processes, so as to obtain various useful materials with different shapes.

According to the present invention, asphalt organic macromolecules are utilized to surround red mud particles, thereby successfully resolving the worldwide problem of long-term effective consolidation of alkali substances infiltrated or attached to the red mud. Red mud products have functions of consolidating alkali and preventing alkali infiltration, can be stockpiled and used for a long time, can play a good role in many fields such as seawall construction, slope protection, river flood control, levee construction, island reef construction, desert control, and on the like, and do not cause harm to underground and overground environments, fully embodying the change of waste into treasure, and benefiting human beings.

In addition, due to the surrounding of asphalt organic macromolecules and the addition of wastes such as fly ash slag, the activity of radioactive substances in red mud is effectively reduced to reach the radiation activity allowed by the environment, and the radiation hazard is effectively avoided.

Besides, the asphalt organic macromolecular material is an effective barrier material for water molecules, which effectively resolves a problem of mutual infiltration and exchange between extraterritorial water and red mud products and preventing re-pollution. In addition, asphalt is a good bonding material, and tightly bonds wastes such as red mud together, so that various physical properties of the products are good. The method in the present invention can implement utilization

2019101452 26 Nov 2019 of a large amount of red mud and large-scale production of red mud products, has a simple process, low investment, and wide product application, can fully utilize the red mud, benefits enterprises and human beings, and brings particularly great economic and social benefits.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a process flowchart of a utilization method of red mud according to the present invention.

DETAILED DESCRIPTION

A utilization method of red mud is provided, including the following steps: (1) filter-pressing red mud, where moisture content of the filter-pressed red mud is l%-39%; (2) crushing fly ash slag, where a particle size of the crushed fly ash slag is less than 110 mm; (3) mixing the filter-pressed red mud in step (1) with the crushed fly ash slag in step (2), adding asphalt for kneading, where a mixing ratio of the filter-pressed red mud and the crushed fly ash slag in step (2) is 1:0-1:5, and an amount of asphalt added is 5%-35%; (4) molding the kneaded material in step (3) into molded building material blocks through a vibration molding or extrusion molding method. The molded material in step (4) can also be sintered to improve its performance, and sintering temperature of the material is 300°C-1350°C, and sintering time of the material is 5 h-40 h.

According to the utilization method of red mud, a sintered product not only eliminates the harm brought because original red mud contains alkali and certain radioactivity, but also achieves various excellent indexes such as strength, corrosion resistance, permeability, and waterproof performance after asphalt organic macromolecules are used as a binder and vibration molding or extrusion molding (whether sintering is required is determined according to a requirement) is conducted. Therefore, the product has a wide application range, and can be mainly applied in the following application fields:

1. Reclamation and seawall and reef construction

China has 18,000 kilometers of coastline and many islands and reefs, and needs building materials with good strength and seawater erosion resistance. Large, medium, and small mixed materials produced by the present invention can be completely suitable for reclamation engineering, seawall construction, and island and reef construction, which not only implements waste utilization, but also effectively resolves a pollution problem and saves a large quantity of other building material resources. The present invention has characteristics of low production costs, high construction speed, and the like.

2. River levee construction

2019101452 26 Nov 2019

There are many rivers and rivers in China, and floods have occurred over the years, causing great disasters to people's lives and property. A red mud composite material in the present invention is very good cheap materials that can be used to reinforce or build river levees and resist and improve flood control capability. Making full use of the red mud composite material not only does not cause new pollution, but also saves a large quantity of resources, implements comprehensive and effective waste utilization, and benefits human beings.

3. Slope protection materials

China has a vast territory, a complex geological structure, and frequent natural disasters. In order to reinforce various dangerous slopes more effectively and prevent natural disasters such as slope failure and mudslides, products produced by using the method in the present invention can effectively reduce disasters.

4. Desert control

The desert area in the north of China is vast but desert control is slow. Sandstorms occur every year, which seriously affect people's life and environment. In order to effectively control desert and prevent or reduce sandstorms, the product in the present invention can be used to build a new Great Wall Against Sand in the deep zone of desert, and also create favorable conditions for effective desert control.

5. Construction of parks, streets, roads, and the like

According to construction requirements of parks, streets, roads, and the like, construction materials satisfying various requirements can be produced by using the method in the present invention, to satisfy requirements of park construction, street construction, and road construction.

6. Thermal insulation construction materials

According to construction requirements, the present invention can be used to fabricate plates, pipes, blocks, and special-shaped products through stirring and pressing, and these products can be applied to heat preservation and heat insulation building materials of pipelines, related walls, related equipment, and the like.

7. Wall construction

The product in the present invention is suitable for wall construction of various venues, factories, and the like.

In the utilization method of red mud, various asphalt (including but not limited to coal asphalt, petroleum asphalt, natural asphalt, and the like) is used as a binder, and the asphalt is mixed with

2019101452 26 Nov 2019 red mud. Various asphalt (including but not limited to coal asphalt, petroleum asphalt, natural asphalt, and the like) is used as an effective anti-pollution material to consolidate alkalis in red mud for infiltration prevention and anti-erosion. Materials of various shapes are formed by vibration molding, extrusion molding, calendaring, and the like of a mixture obtained by mixing various asphalt (including but not limited to coal asphalt, petroleum asphalt, natural asphalt, and the like) as a binder and waste such as red mud, fly ash slag, and the like as aggregates at all ratios. Large red mud mixed blocks are produced by adopting a kneading machine and a vibration molding machine in the carbon industry for aluminum.

Embodiment 1

Red mud is filter-pressed, where moisture content of the filter-pressed red mud is 10%. Fly ash slag is crushed, where a particle size of the crushed fly ash slag is less than 30 mm. The filterpressed red mud and the crushed fly ash slag are mixed according to a weight ratio 1:0.5 of the red mud to the fly ash slag and asphalt accounting for 15% of a weight of the red mud and the fly ash slag is added for kneading. Vibration molding or extrusion molding is conducted to form rectangular blocks. The molded rectangular blocks are sintered at 600°C for 35 h, and the obtained rectangular blocks are used for building factory walls, and has a good application effect.

Embodiment 2

Red mud is filter-pressed, where moisture content of the filter-pressed red mud is 15%. Fly ash slag is crushed, where a particle size of the crushed fly ash slag is less than 30 mm. The filterpressed red mud and the crushed fly ash slag are mixed according to a weight ratio 1:0.8 of the red mud to the fly ash slag, and asphalt accounting for 16% of a weight of the red mud and the fly ash slag is added for kneading. Vibration molding or extrusion molding is conducted to form rectangular blocks. The molded rectangular blocks are sintered at 800°C for 30 h, and the sintered rectangular blocks have a good application effect in reclamation dike engineering.

Embodiment 3

Red mud is filter-pressed, where moisture content of the filter-pressed red mud is 20%. Fly ash slag is crushed, where a particle size of the crushed fly ash slag is less than 40 mm. The filterpressed red mud and the crushed fly ash slag are mixed according to a weight ratio 1:1 of the red mud to the fly ash slag and asphalt accounting for 18% of a weight of the red mud and the fly ash slag is added for kneading. Extrusion forming is conduced to form ground bricks. The molded ground bricks are directly used for river levee construction and park-related pool and dam construction, and a dam built by using the ground bricks is firm.

Embodiment 4

2019101452 26 Nov 2019

Red mud is filter-pressed, where moisture content of the filter-pressed red mud is 30%. Fly ash slag is crushed, where a particle size of the crushed fly ash slag is less than 35 mm. The filterpressed red mud and the crushed fly ash slag are mixed according to a weight ratio 1:2 of the red mud to the fly ash slag and asphalt accounting for 20% of the weight of the red mud and the fly ash slag is added for mix and kneading. Extrusion molding is conducted to form rectangular brick blanks. The rectangular brick blanks are sintered at 1100°C for 20 h, and sintered bricks are applied to the construction of seawalls, river levees and park walls and have a good application effect.

Embodiment 5

Red mud is filter-pressed, where moisture content of the filter-pressed red mud is 39%. Fly ash slag is crushed, where a particle size of the crushed fly ash slag is less than 110 mm. The filterpressed red mud and the crushed fly ash slag are mixed according to a weight ratio 1:5 of the red mud to the fly ash slag and asphalt accounting for 5% of a weight of the red mud and the fly ash slag is added for kneading. Extrusion molding is conducted to form rectangular brick blanks. The rectangular brick blanks are sintered at 1360°C for 5 h, and sintered bricks are applied to the construction of seawalls, river levees and park walls and have a good application effect.

Embodiment 6

Red mud is filter-pressed, where moisture content (weight) of the filter-pressed red mud is 1%. Asphalt accounting for 35% of a weight of the red mud is added to the filter-pressed red mud for kneading. Extrusion molding is conducted to form rectangular brick blanks. The rectangular brick blanks are sintered at 300°C for 40 h, and sintered bricks are applied to the construction of seawalls, river levees, and park walls and have a good application effect.

Claims

What is claimed is:

(1) filter-pressing red mud;

1. A utilization method of red mud, comprising the following steps:
2. The utilization method of red mud according to claim 1, wherein after vibration molding or extrusion is conducted on the kneaded material to obtain the molded building material blocks, the molded building material blocks are sintered, preferably, wherein sintering temperature of the molded building material blocks obtained through molding in step (4) is 300°C-1350°C, and sintering time of the molded building material blocks is 5 h-40 h.

(2) crushing fly ash slag;
3. The utilization method of red mud according to claim 1, wherein moisture content of the filter-pressed red mud in step (1) is l%-39%.

(3) mixing the filter-pressed red mud in step (1) with the crushed fly ash slag in step (2), and adding asphalt for kneading; and (4) conducting vibration molding or extrusion on a kneaded material in step (3) to obtain molded building material blocks.
4. The utilization method of red mud according to claim 1, wherein a particle size of the crushed fly ash slag in step (2) is less than 110 mm.
5. The utilization method of red mud according to claim 1, wherein a mixing ratio of the filterpressed red mud in step (3) and the crushed fly ash slag in step (1) is 1:0-1:5, and an amount of asphalt added is 5%-35%.