CN1443712A

CN1443712A - Comprehensive utilization of coal gangue for producing alumina and electrolytic aluminium

Info

Publication number: CN1443712A
Application number: CN 02107204
Authority: CN
Inventors: 康仁
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-03-07
Filing date: 2002-03-07
Publication date: 2003-09-24
Anticipated expiration: 2022-03-07
Also published as: CN1226190C

Abstract

The present invention discloses a method for comprehensively-utilizing coal gauge to produce alumnia and electrolytic aluminium, and its technical scheme is that the coal gangue power generation process, electrolytic aluminium process and improved production proces sof Al2O3 by using flyash are combined together, the lectricity produced by coal gangue power plant, can be used as energy source for producing electrolytic aluminium and other power equipments, and the flyash produced by power plant can be used as raw material for producing Al2O3, and the Al2O3 also can be used as raw material for producing electrolytic aluminium.

Description

Comprehensive utilization of gangue to produce alumina and electrolytic aluminium

The technical field is as follows:

the invention belongs to the field of chemical industry and metallurgical industry, and relates to a production process for producing alumina and electrolytic aluminum by comprehensively utilizing coal gangue.

Background art:

the method for producing alumina in the world is basically to produce Al (OH) by using bauxite₃Intermediate step for Al production₂O₃The method is called an alkaline process, and mainly comprises a Bayer process, a sintering process and a combination method of the Bayer process and the sintering process. As the bauxite resources are reduced, the production of Al by utilizing the coal gangue is started in the seventies₂O₃After that, the acid method gradually appears to produce Al₂O₃And the clinker self-pulverization method for extracting Al (OH)₃Further deep processing to produce Al₂O₃The technique of (1). For the aluminum smelting process of low-grade ore, acid method is adopted for producingThe method for producing alumina has the advantages that the method can treat widely distributed aluminosilicate minerals (namely poor aluminum ore resources), but the method has the difficulties in the aspects of separating silicon slag, removing iron and purifying, recovering acid, adopting acid-proof equipment and the like, and the acid method process consumes a large amount of sulfuric acid and has poor economic benefit. Therefore, the domestic ammonium-alum-Ming-V pyrolysis production process and the salting-out method, namely the process adopting hot sulfuric acid and ammonium sulfate treatment, are also adopted. The method is a process for simply producing the alumina, so the process flow is long, the investment of fixed assets is large, the energy consumption is high, and the economic benefit is low.

With the wide use of circulating fluidized bed boilers, the process of generating electricity by adopting coal gangue is mature, and the coal gangue electricity generation is already used for production. But the consequent 40% Al content₂O₃The fly ash is white and is discharged, and the environment is polluted; toproduce Al exclusively₂O₃From coal gangue throughThe fly ash is produced through a series of processes of crushing, balling, calcining, re-crushing and the like. Thus, power generation and Al production₂O₃The cost is very high, so that the coal gangue is utilized to produce Al₂O₃The economic benefit is too poor to realize industrial production. Production of Al to date₂O₃The rich ore is used for production, so that on the one hand, the rich ore is less and less, on the other hand, the poor ore such as coal gangue and the 'garbage' are more and more, and Al₂O₃And metallic aluminum is used in larger and larger amounts. Therefore, the new process route is adopted, and the comprehensive utilization of the coal gangue is very important.

The invention content is as follows:

the invention aims to provide a production process which takes coal gangue as a raw material and a final product of metal aluminum, is technically advanced, economically feasible and meets the requirements of national conditions and environmental protection.

The technical scheme of the invention is as follows: the existing coal gangue power generation process, the electrolytic aluminum process and the improved fly ash are made into Al₂O₃The process is combined, the electricity produced by the gangue power plant is used as the energy source for electrolyzing aluminum and other powerUse of fly ash as Al production₂O₃Raw material of (2), Al₂O₃The main raw material entering the system is coal gangue, and main products from the system are aluminum hydroxide, aluminum oxide and electrolytic aluminum through various processes.

The beneficial technical effects of the invention are as follows: through the scientific configuration of the three processes, the products of the former process are the raw materials and energy of the latter process, the total process flow and equipment investment are reduced, the economic benefit is improved, and the comprehensive utilization of coal gangue for producing alumina and electrolytic aluminum is possible; the gangue power generation and electrolytic aluminum process is a mature technology applied to production, and the economic benefit is greatly improved by combining the improved aluminum oxide production technology with the improved aluminum oxide production technology. And (3) comprehensive evaluation: the invention has reliable process and strong feasibility; the method conforms to the national situation and the large direction of lean ore production and aluminum production by waste utilization, and the utilization of the coal gangue and the fly ash is beneficial to environmental protection.

Description of the drawings:

FIG. l is a block diagram of the process of the present invention.

FIG. 2 is a schematic process flow diagram of the present invention.

The specific implementation mode is as follows:

the principle and the process flow of the invention are described in the following with reference to the accompanying drawings:

the technical scheme of the invention is to prepare Al from coal gangue power generation process and fly ash₂O₃The process and the electrolytic aluminum production process. The electricity produced by gangue power plant is used as energy source for electrolyzing aluminium and other power, and the produced fly ash is used for producing Al₂O₃Raw material of (2), Al₂O₃The main raw material entering the system is coal gangue, and main products from the system are aluminum hydroxide, aluminum oxide and electrolytic aluminum through various processes.

Generating power by using coal gangue: the coal gangue or the aluminum-containing low-grade coal is crushed and sent to a circulating fluidized bed boiler of a power plant for combustion, the generated steam pushes a generator to operate for power generation, and the power is sent to an electrolytic aluminum process and a whole system for power utilization. The gangue power plant should be incorporated into the local power grid to facilitate load regulation. The steam of the power plant is used for the system; the generated fly ash is sent to an alumina process flow to be used as a main raw material.

(II) alumina production: the alumina production equipment consists of a leaching tank, a plate-and-frame filter press, a carbonization tower, a calcining furnace, a lime kiln and the like.

(1) Feeding the fly ash into a leaching tank, adding a proper amount of lime milk and soda ash into the leaching tank to control the content of sodium hydroxide to be 3-5%, adding sodium carbonate mother liquor after normal production, and simultaneously adding part of soda ash to control the content of sodium hydroxide to be in the range; the temperature is controlled to be about 80 ℃ and normal pressure.

The main reaction is as follows:

generation of NaAlO₂And (4) liquid.

(2) Filtering the product (a) with a plate-frame filter (or adding a thickener, thickening and then filtering), wherein the residue mainly contains SiO₂AndCaCO₃The clear liquid is crude NaAlO₂And (4) liquid. The slag can be used for preparing cement. (ingredients are shown in attached table 1)

(3) In the presence of crude NaAlO₂Adding a small amount of lime milk into the solution, and pressure-cooking with 0.5-0.6 MPa steam to obtain SiO in the solution₂Sodium aluminosilicate is separated out and removed by a plate-and-frame filter press, and clear liquid enters fine NaAlO₂A liquid tank.

(4) The refined NaAlO is added₂The liquid is pumped into a carbonization tower, and CO is fed into a lime kiln through an air compressor₂Gas (concentration 20% -25%), Na is generated by reaction₂CO₃And Al (OH)₃Precipitating, separating with plate-and-frame filter press (or centrifuge), and collecting mother liquor containing Na₂CO₃3-4%, and returning to the leaching tank for reuse. Formed Al (OH)₃And sending the product to a warehouse for standby.

The reaction formula is as follows:

(5) al (OH)₃Is sent to the outsideThermal converter calcination (550 ℃) to Al₂O₃，

The reaction formula is as follows:

Al₂O₃namely the raw materials for producing electrolytic aluminum and special alumina.

Inventive pair Al₂O₃The production process is greatly changed and mainly has three aspects:

(1) in the existing technological process, the process for preparing fly ash is very long, and the main raw materials (coal gangue, limestone and coal) are pulverized, pelletized, dried,Calcining, crushing the calcined material and the like, the used equipment is huge and heavy, and the investment of fixed assets is large and the energy consumption is high. The above-mentioned technological process of the invention is replaced by circulating fluidized bed boiler of power plant, to producing Al₂O₃In addition, the investment of fixed assets is greatly reduced (by about more than 60 percent), and the 'zero cost' (i.e. no charge) of main raw materials is made.

(2) In the current technological process, limestone and coal gangue are calcined together, and the invention is to additionally construct a lime kiln to prepare CaO and Ca (OH)₂Adding lime milk to prepare NaAlO₂Therefore, the process is easy to control, and the consumption of the soda ash is low (the slag discharge is reduced, and the taken away soda ash is reduced).

(3) In the current process, the catalyst is prepared from NaAlO₂Production of Al (OH)₃By changing the process conditions to Al (OH)₃The method adopts carbonization reaction and CO produced by the lime kiln₂With NaAlO₂Reaction to form Al (OH)₃And (4) precipitating. CO 2₂The concentration can reach more than 25 percent, so the reaction speed is high, and Al in the fly ash₂O₃High yield, and the recovery rate of soda ash can be more than 80%.

(III) electrolytic aluminum:

the electric energy generated by gangue power generation and Al generated by alumina production₂O₃Sending to an electrolytic aluminum plant to produce the metallic aluminum.

Al produced by this method₂O₃Can also be used for preparing special alumina and crystalline aluminum chloride with higher value through deep processingAnd polyaluminium chloride.

The invention has the main technical effects that:

the comprehensive utilization of the coal gangue is carried out according to the process, the technical effect, the economic benefit and the social benefit are very obvious, and the process comprises the following steps:

1. the coal gangue generally contains 15 percent of combustible materials, and when the coal gangue is calcined according to the prior art, not only the part of heat energy can not be utilized, but also part of fuel can be added,the energy consumption is very large. The heat energy in the coal gangue can be converted into electric energy by adopting the production process, so that the comprehensive utilization of the heat energy is realized (the components of the coal gangue are shown in an attached table 1); SiO in gangue₂The slag is taken out and can be used as a cement raw material, so that the real comprehensive utilization of coal gangue is achieved.

2. The process can realize high economic benefit. Through measurement and calculation, the cost of each ton of aluminum is reduced by more than 50O0 yuan compared with the cost of the existing process, a 10-kiloton aluminum plant is built, and the annual increase of economic benefit can reach 5 hundred million yuan. The gangue power station replaces a plurality of heavy equipment in the original process, the investment of fixed assets (about 60 percent) can be greatly reduced, and the method is used for manufacturing Al₂O₃In other words, the raw material fly ash can be disregarded for the cost, so that Al is ensured₂O₃The production cost is reduced by 40-50%.

3. The production is organized by the process, so that the environmental pollution can be greatly reduced. At present, a lot of coal mine waste rocks are piled up to form a mountain, spontaneous combustion is carried out in the long term, dust and SO discharged are generated₂And harmful gases such as CO seriously pollute the environment. 70 ten thousand tons of coal gangue can be eaten by a 10 ten thousand ton aluminum plant constructed by the process every year. And the fly ash discharged by a power plant is changed into valuable.

4. Because the metal aluminum and the alloy thereof have special physical and chemical properties, the metal aluminum and the alloy thereof are widely applied in various departments of national economy and are in short supply. However, the raw material for extracting aluminum according to the prior art, namely the aluminum-containing rich ore, is less and less, and can not adapt to the requirement of national economic development. The successful development of the process of the invention necessarily greatly expands the raw material source of the aluminum industry and produces Al₂O₃And metal aluminum provides abundant raw material resources, and greatly promotes the development of the aluminum production industry.Attached table 1:

composition of various materials in Wuhai region

Name of material	nnn	SiO₂	Al₂O₃	Fe₂O₃	CaO	Mg0	R₂0	Remarks for note
Name of material	nnn	SiO₂	Al₂O₃	Fe₂O₃	CaO	Mg0	R₂0	Remarks for note	Coal gangue	16.6	41.5	38.3	0.7	0.2	0.44	0.56
Fly ash		49.2	40.3	6.0	2.6	0.3		West Water Co Ltd	Coal gangue	16.6	41.5	38.3	0.7	0.2	0.44	0.56
Fly ash		49.2	40.3	6.0	2.6	0.3		West Water Co Ltd	General coal ash		48.0	38.0	5.0	3.5	0.5
Gangue dump ash	3.5	52.0	35.0	3.5	0.7	0.7		Old stone denier ore	General coal ash		48.0	38.0	5.0	3.5	0.5
Gangue dump ash	3.5	52.0	35.0	3.5	0.7	0.7		Old stone denier ore	Clay clay	10.0	54.0	14.0	5.5	8	3
Silicon slag		91.08	4.28	0.18	4.5				Clay clay	10.0	54.0	14.0	5.5	8	3

Claims

1. A method for producing alumina and electrolytic aluminum by comprehensively utilizing coal gangue is characterized by comprising the following steps: the technical scheme is that the existing coal gangue power generation process, the electrolytic aluminum process and the improved fly ash are prepared into Al₂O₃The process is combined, the electricity produced by the gangue power plant is used as the energy source for electrolyzing aluminum and other power, and the produced fly ash is used forproducing Al₂O₃Raw material of (2), Al₂O₃The main raw material entering the system is coal gangue, and main products from the system are aluminum hydroxide, aluminum oxide and electrolytic aluminum through various processes.

2. The method for producing alumina and electrolytic aluminum by comprehensively utilizing coal gangue as claimed in claim 1, wherein the method comprises the following steps: the alumina production equipment consists of a leaching tank, a plate-and-frame filter press, a carbonization tower, a calcining furnace and a lime kiln; the main process flow is as follows: leaching reaction in leaching tank, filtering with plate-and-frame filter to remove SiO₂Reaction in carbonizer to remove NaCO₃，Al(OH)₃Calcination, and the like.