WO2020206830A1

WO2020206830A1 - Method for recovering sodium, iron and titanium from red mud and directly cementing molten slag

Info

Publication number: WO2020206830A1
Application number: PCT/CN2019/090838
Authority: WO
Inventors: 张廷安; 刘燕; 豆志河; 吕国志; 赵秋月; 傅大学; 张伟光; 张子木
Original assignee: 东北大学
Priority date: 2019-04-11
Filing date: 2019-06-12
Publication date: 2020-10-15
Also published as: CN109913655A

Abstract

Disclosed is a method for recovering sodium, iron and titanium from red mud and directly cementing molten slag, comprising the following steps: (1) preparing red mud having high contents of iron and titanium as a raw material; (2) dehydrating and mixing the raw material with a solid-state carbonaceous reducing agent and a slagging agent to form a mixed material, and blowing the mixed material into the center of a vortex in a vortex-mixing high-temperature furnace and subjecting the mixed material to vortex-mixing reduction; (3) separating, from a titanium-containing molten slag, the molten iron formed after reduction, and casting the molten iron into a wear-resistant cast iron product; and (4) cooling the titanium-containing molten slag to allow titanium-containing components to enrich into a titanium-containing phase and separate from a residual slag, adjusting the composition of the residual slag, and crushing and grinding the same to prepare cement clinker, and recovering sodium by means of a flue gas dust collection system. The method can achieve extraction of sodium, iron and titanium from red mud all at the same time, with high extraction rates of sodium, iron and titanium.

Description

Method for directly cementing red mud recovery of sodium, iron and titanium while melting slag

Technical field

The invention relates to the technical field of environmental protection, and in particular to a method for recovering sodium, iron and titanium from red mud while directly cementing molten slag.

technical background

Red mud is a strong alkaline solid waste produced by preparing alumina or aluminum hydroxide from bauxite. At present, the global red mud reserve is estimated to exceed 3 billion tons, and it is growing at a rate of about 120 million tons per year. The average utilization rate of red mud in the world is 15%. The cumulative stock of red mud in China has grown to 600 million tons, and is growing at a rate of about 100 million tons per year. The red mud utilization rate in China is only 4%. Most of the red mud is still disposed of on land. Red mud storage not only wastes secondary resources and occupies a large amount of land, but also destroys the surrounding environment of the red mud storage yard, causing serious environmental problems, resulting in a sharp increase in environmental protection pressure on the aluminum industry. The environmental risks of red mud storage have long attracted the attention of the governments and enterprises of various alumina producing countries. The key to solving the red mud problem is to develop red mud comprehensive utilization technology.

In order to realize the efficient use of red mud and the extraction of valuable elements, China's aluminum industry has carried out a large amount of research and development. The existing red mud utilization technologies can generally be divided into two types: one is the overall utilization as a general industrial raw material, such as Zhao Guangming “A method for producing cement clinker using red mud” (application number: CN201210031710.1) invented by others is to add dealkalized gypsum and fly ash to dealkalized red mud, and put the above three materials in a mixing tank Mix it evenly, and add water to adjust its concentration to 30%. Use a plate and frame high-pressure filter press to filter the solid mixture until the water content of the solid mixture is less than 25%, and then send it to the rotary kiln for calcination into cement clinker; Wang Wenju and others invented "a kind of aluminum industrial process waste residue is transformed into an ecological building material "Techniques and Methods" (application number: CN200710105971), using solid waste red mud (sintering method, Bayer method), boiler slag, beneficiation tailings, ashing slag, gas generator slag, The six kinds of sludge waste residues have their own material properties, which are transformed into new road materials and building wall materials through drying, crushing, reasonable proportioning, processing and molding (rolling, extrusion) consolidation or sintering processes.

There are also technologies for extracting valuable metal elements such as Na, Al, Fe, and rare metals from red mud; Lou Dongmin and others invented "a Bayer process red mud dealkalization method" (application number: CN201810572642.7). The mud is ground to renew the surface of the red mud, and then the red mud that has undergone surface renewal treatment is mixed with the lime milk and then subjected to dealkalization reaction. After the dealkalization reaction, the red mud slurry is washed and separated from liquid to solid. The alkali-containing solution is returned to the alumina production process, and the separated red mud with low alkali content is sent to the red mud dam for storage;

Chen Huanyue et al. invented "a method for separating, extracting iron and removing sodium from red mud, application number CN108686828A". The red mud is crushed or ball milled into a fine red mud material mainly composed of fine particles. The material is classified to separate 10 to 98% of the fine particles with a particle size of less than 5 microns in the fine red mud. The separated products with a particle size of less than 5 microns are mainly sodium silica slag and calcium silica slag. In the product, the sodium oxide content is greater than 10%, and the remaining red mud material after classification is an iron ore product, and the iron oxide content is greater than 30%.

When red mud is used as a general industrial raw material, there are problems such as red mud alkalinity restriction, low product price, poor profitability, etc.; most of the methods for extracting valuable elements have low extraction rate and low purity of element-enriched products, which cannot be used directly. problem. Therefore, despite the numerous studies on the utilization of red mud in the alumina industry, the problem of red mud storage has not been properly resolved.

Summary of the invention

In order to better realize the comprehensive utilization of red mud, the present invention provides a method for recovering sodium, iron and titanium from red mud while molten slag is directly cemented. The high-iron and high-titanium red mud is used as a raw material and mixed with a reducing agent and a slag-forming agent. Then it is sprayed to the vortex center of the high-temperature reduction furnace to reduce iron, sodium enters the flue gas for recovery, the molten slag is slowly cooled to enrich and separate the titanium-containing phase, and the remaining slag adjusts the components to be ground directly into cement clinker.

The method of the present invention is carried out in the following steps:

(1) Prepare raw material high-iron and high-titanium red mud. The high-iron and high-titanium red mud is 20-40% by mass percentage TFe, containing TiO ₂ 3-10%, Na ₂ O 2-15%, Al ₂ O ₃ 15-25%, SiO ₂ 15-25%, CaO 5-25%, H ₂ O 5-20%;

(2) Dry the raw materials until the mass percentage of water is ≤1% to obtain dehydrated raw materials; mix the dehydrated raw materials with solid carbonaceous reducing agent and slagging agent into a mixture, which is directly sprayed into the vortex center of the vortex stirring high-temperature furnace , The mixture is rolled into the molten pool, and vortex stirring reduction is performed at 1300～1450℃ for 10～60min; the solid carbonaceous reducing agent is coking coal, and the molar ratio of the amount of solid carbonaceous reducing agent to Fe in the raw material is 1.2 ~1.5, the slagging agent is a mixture of CaO and CaF ₂ , in which CaO is added according to the basicity of the mixture at 1.0 to 1.4, and CaF ₂ accounts for 10 to 30% of the total mass of CaO:

(3) The molten iron formed after reduction is layered with the titanium-containing molten slag, and is separated by continuous overflow; adding ferrochrome and ferromanganese to the separated molten iron to directly smelt and cast into wear-resistant cast iron products;

(4) During the cooling process of the separated titanium-containing molten slag, the titanium-containing components are gradually enriched to form a titanium-containing phase, which is separated from the residual slag; the titanium-containing phase is taken out, and the composition of the residual slag is adjusted to meet the requirements of cement clinker. It is crushed and ground to make cement clinker.

The above calculation formula for alkalinity is as follows

Wherein, mCaO mixed powder mass percent of calcium oxide, mAl ₂ O ₃ as the weight percentage of alumina in the mixed powder, mSiO ₂ mixed oxide powder mass percent of silicon, mTiO ₂ mixed powder The mass percentage of titanium oxide.

In the above method, the main reaction of iron oxide reduction is:

Fe _x O _y +yC=yCO+xFe (2),

Fe _x O _y +yCO=yCO ₂ +xFe (3)

with

Fe _x O _y +y/2C=y/2CO ₂ +xFe (4).

In the above method, sodium enters the flue gas during the vortex stirring reduction process, and is recovered by the flue gas dust collection system.

In the above method, the iron recovery rate is ≥90%.

In the above method, the recovery rate of sodium is ≥95%.

In the above method, the main component of the titanium-rich phase is titanium oxide, and the recovery rate of titanium is ≥60%.

Compared with the prior art, the features and beneficial effects of the present invention are:

(1) The high-speed iron and high-titanium red mud is reduced by vortex smelting. After the red mud is mixed with the reducing agent and the slagging agent, it is directly sprayed into the vortex area of the vortex smelting reduction furnace without any request. Sodium enters the flue gas recovery during the reduction process to obtain The molten iron is directly smelted into wear-resistant cast iron products by adding ferrochrome and ferromanganese, which can simultaneously extract sodium and iron in the red mud;

(2) The process steps are simple, the Na ₂ O content of the molten slag after dealkalization is less than 0.5%, which can better meet the composition requirements of cement clinker, and can increase the amount of cement clinker burned with red mud;

(3) The extraction rate of sodium and iron is higher, above 90% and 95%, respectively. The molten slag is cooled to enrich and separate the titanium-containing phase. The extraction rate of titanium can reach more than 60%, and the tailings after extraction are completely Used in the production of cement clinker, the utilization rate of red mud reaches 100%.

Description of the drawings

Fig. 1 is a schematic flow diagram of a method for recovering sodium, iron and titanium from red mud while directly cementing molten slag.

Specific implementation

Examples cement clinker composition embodiment of the present invention containing mass percent _{CaO 62 ~ 64%, SiO 2} 20 ~ 23%, Al 2 O 3 4 ~ 6%, Fe 2 O 3 3 ~ 5%.

In the embodiment of the invention, the Na ₂ O mass percentage of the molten slag is less than 0.5%.

The wear-resistant cast iron product in the embodiment of the present invention is wear-resistant cast iron of the brand HBW555Cr13 (ISO 21988/JN/HB).

In the embodiment of the present invention, the temperature when the raw material is dried is 150-200°C.

The vortex stirring reduction of the present invention refers to the method disclosed in the invention of "a method for vortex stirring smelting reduction ironmaking", and the involved vortex stirring reduction high-temperature furnace is the equipment used for this method.

A vortex stirring smelting reduction ironmaking method of the present invention is a patent application with publication number CN106435080A.

In the embodiment of the present invention, the adjusting component is adding calcium raw material, siliceous raw material and/or iron raw material. The calcareous raw material is at least one of limestone and calcium carbide slag; the siliceous raw material is at least one of kaolin, clay, fly ash, and tailings slag; the iron raw material is at least one of high-speed iron red mud, iron slag, and steel slag. Kind.

In the embodiment of the present invention, the recovery rate of sodium is ≥95%, and the recovery rate of iron is ≥90%.

In the embodiment of the present invention, the main component of the titanium-rich phase is titanium oxide, and the recovery rate of titanium is ≥60%.

The present invention will be further described in detail below in conjunction with embodiments.

Example 1

(1) Prepare the raw material high-iron and high-titanium red mud. The high-iron and high-titanium red mud is TFe 40% by mass, containing 10% TiO _{2 and} 12% Na ₂ O;

(2) Dry the raw materials until the mass percentage of water is ≤1% to obtain dehydrated raw materials; mix the dehydrated raw materials with solid carbonaceous reducing agent and slagging agent into a mixture, which is directly sprayed into the vortex center of the vortex stirring high-temperature furnace , The mixture is drawn into the molten pool and reduced by vortex stirring at 1300°C for 60 minutes; the solid carbonaceous reducing agent is coking coal, and the molar ratio of the amount of solid carbonaceous reducing agent to Fe in the raw material is 1.2. It is a mixture of CaO and CaF ₂ , in which CaO is added according to the alkalinity of the mixture of 1.4, and CaF ₂ accounts for 10% of the total mass of CaO: sodium enters the flue gas during the vortex stirring reduction process, and is recovered by the flue gas dust collection system;

(4) During the cooling process of the separated titanium-containing molten slag, the titanium-containing components are gradually enriched to form a titanium-containing phase, which is separated from the residual slag; the titanium-containing phase is taken out, and the composition of the residual slag is adjusted to meet the requirements of cement clinker. After crushing and grinding to make cement clinker, the mass percentages of CaO, SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ in the cement clinker are 62%, 23%, 5% and 4% respectively, which meet the requirements of cement clinker The composition requirements.

Example 2

(1) Prepare the raw material high-iron and high-titanium red mud, which is TFe 20%, TiO ₂ 4%, and Na ₂ O 3% by mass percentage;

(2) Dry the raw materials until the mass percentage of water is ≤1% to obtain dehydrated raw materials; mix the dehydrated raw materials with solid carbonaceous reducing agent and slagging agent into a mixture, which is directly sprayed into the vortex center of the vortex stirring high-temperature furnace , The mixture is drawn into the molten pool, vortex stirring reduction is carried out at 1450°C for 10 minutes; the solid carbonaceous reducing agent is coking coal, and the molar ratio of the amount of solid carbonaceous reducing agent to Fe in the raw material is 1.5. It is a mixture of CaO and CaF ₂ , where CaO is added according to the alkalinity of the mixture at 1.2, and CaF ₂ accounts for 20% of the total mass of CaO: sodium enters the flue gas during the vortex stirring reduction process, and is recovered by the flue gas dust collection system;

(4) During the cooling process of the separated titanium-containing molten slag, the titanium-containing components are gradually enriched to form a titanium-containing phase, which is separated from the residual slag; the titanium-containing phase is taken out, and the composition of the residual slag is adjusted to meet the requirements of cement clinker. After crushing and grinding to make cement clinker, the mass percentages of CaO, SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ in the cement clinker are 64%, 20%, 6%, and 5% respectively, which meet the requirements of cement clinker The composition requirements.

Example 3

(1) Prepare the raw material high-iron and high-titanium red mud. The mass percentage of high-iron and high-titanium red mud is TFe 30%, TiO ₂ content 3%, and Na ₂ O 15%;

(2) Dry the raw materials until the mass percentage of water is ≤1% to obtain dehydrated raw materials; mix the dehydrated raw materials with solid carbonaceous reducing agent and slagging agent into a mixture, which is directly sprayed into the vortex center of the vortex stirring high-temperature furnace , The mixture is drawn into the molten pool and reduced by vortex agitation at 1400°C for 30 minutes; the solid carbonaceous reducing agent is coking coal, and the molar ratio of the amount of solid carbonaceous reducing agent to Fe in the raw material is 1.4. It is a mixture of CaO and CaF ₂ , where CaO is added according to the alkalinity of the mixture at 1.0, and CaF ₂ accounts for 30% of the total mass of CaO: Sodium enters the flue gas during the vortex stirring reduction process, and is recovered by the flue gas dust collection system;

(4) During the cooling process of the separated titanium-containing molten slag, the titanium-containing components are gradually enriched to form a titanium-containing phase, which is separated from the residual slag; the titanium-containing phase is taken out, and the composition of the residual slag is adjusted to meet the requirements of cement clinker. After crushing and grinding to make cement clinker, the mass percentages of CaO, SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ in the cement clinker are respectively 63%, 21%, 4% and 3%, which meet the requirements of cement clinker The composition requirements.

Claims

A method for recovering sodium, iron and titanium from red mud while melting slag and directly cementing it is characterized in that it is carried out in the following steps:

(1) Prepare raw material high-iron and high-titanium red mud. The high-iron and high-titanium red mud is 20-40% by mass percentage TFe, containing TiO 2 3-10%, Na 2 O 2-15%, Al 2 O 3 15-25%, SiO 2 15-25%, CaO 5-25%, H 2 O 5-20%;

(2) Dry the raw materials until the mass percentage of water is ≤1% to obtain dehydrated raw materials; mix the dehydrated raw materials with solid carbonaceous reducing agent and slagging agent into a mixture, which is directly sprayed into the vortex center of the vortex stirring high-temperature furnace , The mixture is rolled into the molten pool, and vortex stirring reduction is performed at 1300～1450℃ for 10～60min; the solid carbonaceous reducing agent is coking coal, and the molar ratio of the amount of solid carbonaceous reducing agent to Fe in the raw material is 1.2 ~1.5, the slagging agent is a mixture of CaO and CaF 2 , in which CaO is added according to the basicity of the mixture at 1.0 to 1.4, and CaF 2 accounts for 10 to 30% of the total mass of CaO:

(3) The molten iron formed after reduction is layered with the titanium-containing molten slag, and is separated by continuous overflow; adding ferrochrome and ferromanganese to the separated molten iron to directly smelt and cast into wear-resistant cast iron products;

(4) During the cooling process of the separated titanium-containing molten slag, the titanium-containing components are gradually enriched to form a titanium-containing phase, which is separated from the residual slag; the titanium-containing phase is taken out, and the composition of the residual slag is adjusted to meet the requirements of cement clinker. It is crushed and ground to make cement clinker.
The method for recovering sodium, iron and titanium from red mud and simultaneously melting slag for direct cementation according to claim 1, characterized in that the calculation formula of alkalinity is

Wherein, mCaO mixed powder mass percent of calcium oxide, mAl 2 O 3 as the weight percentage of alumina in the mixed powder, mSiO 2 mixed oxide powder mass percent of silicon, mTiO 2 mixed powder The mass percentage of titanium oxide.
The method for recovering sodium, iron and titanium from red mud while direct cementation of molten slag according to claim 1, characterized in that in step (2), sodium enters the flue gas during the vortex stirring reduction process, and dust is collected through the flue gas. System recycling.
The method for recovering sodium, iron and titanium from red mud and directly cementing molten slag according to claim 1, characterized in that the iron recovery rate is ≥90%.
The method for recovering sodium, iron, and titanium from red mud while directly cementing molten slag according to claim 1, characterized in that the recovery rate of sodium is ≥95%.
The method for recovering sodium, iron and titanium from red mud while directly cementing molten slag according to claim 1, wherein the main component of the titanium-rich phase is titanium oxide, and the recovery rate of titanium is ≥60%.