CN102642857A - Process method for producing metal aluminium by high-alumina fly ash - Google Patents

Abstract

The invention discloses a process method for producing metal aluminium by high-alumina fly ash, which comprises the following process steps: firstly, dissolving fly ash out, that is, mixing high-alumina fly ash containing not less than 38% of Al2O3 with hydrochloric acid with a concentration of 20-30% to prepare raw pulp, dissolving out alumina in the fly ash at a high temperature through a continuous dissolving mode of heat insulation dissolution by a preheater and an autoclave; secondly, separating and washing acid sludge, and purifying an aluminium chloride solution for impurity removal; thirdly, performing spray drying and dehydration to obtain anhydrous aluminium chloride crystal particles; fourthly, electrolyzing the molten salts, that is, adding the anhydrous aluminium chloride into an aluminium chloride electrolytic tank, dissolving the anhydrous aluminium chloride in a molten electrolyte, wherein the temperature in the electrolytic tank is 670-700 DEG C, performing electrolyzation to obtain aluminium liquid, delivering the aluminium liquid to a casting procedure, performing purification and clarification, then preparing aluminum ingots, delivering the chlorine generated at an anode of the electrolytic tank to a hydrochloric acid preparation procedure; fifthly, preparing hydrochloric acid. The process of the invention obtains aluminum ingots by treating high-alumina fly ash, which make reasonable use of fly ash.

Description

A kind of aluminous fly-ash is produced the metallic aluminium process method

Technical field

The present invention relates to a kind of aluminous fly-ash and produce the metallic aluminium process method.

Background technology

At present in the world aluminum electrolysis industry mainly to adopt aluminum oxide be raw material, aluminum oxide (Al₂O₃) and sodium aluminum fluoride (3NaFAlF₃) form the fused ionogen at more than 900 ℃ high temperature, form basic electrolyte ingredient, in electrolyzer, carry out electrolysis and obtain metallic aluminium.

Alumina producing mainly is raw material with bauxite, adopts the bayer's process production technique to make, and the purposes of aluminum oxide is a lot, but the overwhelming majority (more than 90%) is used to produce metallic aluminium as the raw material of electrolytic aluminium factory.

China is aluminum oxide, metallic aluminium largest production state in the world; Aluminum oxide and electrolytic aluminum output account for about 40% of Gross World Product; But China's bauxite resource is poor; Ore grade is lower, and ore type is main with unmanageable diaspore mainly, and complex manufacturing, energy consumption of unit product are high, production cost is also higher.

Because China's bauxite resource wretched insufficiency can only rely on Ore Imported to solve the raw material problem, about 3,000 ten thousand tons of year import bauxite accounts for about half of domestic bauxite usage quantity.The ore resource deficiency has restricted China's aluminium industrial development, seeks new alternative non-bauxite resource as the aluminum oxide industry raw material, and studies new electrolytic aluminium production process, and this has crucial meaning to China's aluminium industrial expansion.

Coal resources in China is very abundant, and coal production accounts for the first in the world, and more than 20 hundred million tons of coals of annual output will be discharged a large amount of flyash behind the coal burning, 3～400,000,000 tons of flyash of the annual discharging of China, and wherein aluminous fly-ash (refers to Al in the flyash₂O₃>=38%) more than 100,000,000 ton.Analyze after deliberation; Aluminous fly-ash mainly is made up of aluminum oxide, silicon oxide, and the content of 2 kinds of compositions accounts for 80%, in addition other compositions such as iron content, magnesium, titanium, calcium, gallium; Be the raw material that metallurgical-grade aluminum oxide and metallic aluminium are extracted in comprehensive utilization, have high industrial utilization and be worth.

Alumina content generally is higher than southern area in the flyash of north China; Like alumina content in the flyash of part mining area, ground outputs such as Shanxi, Shaanxi, Inner Mongol, Ningxia, Xinjiang usually about 40%; Belong to aluminous fly-ash, in the Erdos area flyash of the Inner Mongol there be alumina content up to 45～50%, and this is suitable with alumina content in the external bauxite trihydrate; From chemical composition analysis, can be used as the raw material that extracts metallurgical-grade aluminum oxide and metallic aluminium fully.

At present flyash thermal power plant's waste of discharging is normally stored up mainly as a kind of industrial residue, and this had both taken a large amount of soils, and severe contamination environment.The coastland is because populous, industry prosperity; Sometimes with flyash be used to build the road, material of construction such as brickmaking; This only belongs to low-grade, the low value-added application of flyash, and economically underdeveloped area or west area, flyash is still stored up mainly as industrial residue.On the whole, China and world developed country still are in the experimental study stage to the total utilization of PCA problem, are seeking the approach that it rationally utilizes.

In recent years; Be rich in the present situation of aluminum oxide to China's bauxite resource wretched insufficiency and flyash; The many scientific research departments of China actively develop non-bauxite resource production metallurgy grade aluminum oxide research, and aluminous fly-ash comprehensive utilization production metallurgy grade aluminum oxide is one of emphasis research topic.Each research unit's basis achievement in research has separately proposed some and has handled the new process of aluminous fly-ashs, and main direction of studying is following:

(1) alkaline process: the main stream approach that is the aluminous fly-ash comprehensive utilizating research.It mainly uses for reference the existing sophisticated sintering process production technique of alumina industry; Utilize sintering process technology can processing low-grade, the characteristics of low alumina silica ratio ore; Aluminous fly-ash, Wingdale (or lime), alkali are pressed certain proportioning; Be prepared into charge pulp and carry out sintering, sintered clinker is through stripping, desiliconization, decomposition, roasting and obtain the metallurgical-grade aluminum oxide product.The advantage of this method is that Technology is ripe, can obtain qualified alumina product.But the shortcoming of this method is a lot, mainly is that the lime dosage is huge, red mud amount is big, concentration sodium aluminate solution is low, production energy consumption is high, its investment and cost height, its art recognized of this method but unreasonable economically.

(2) acid system: adopt hydrochloric acid or sulfuric acid and aluminous fly-ash to prepare burden in proportion; Aluminum oxide under certain temperature and pressure condition in the stripping flyash; Aluminum oxide is got in the solution; After evaporative crystallization, roasting obtain alumina product, its advantage is that flow process is simple, the quantity of slag is little, production cost is low to solution through the removal of impurities purification.Shortcoming be removing iron from solution and removal of impurities difficult, the corrosion resistance nature of equipment and material is required height, some technologies and problem of materials need further be researched and solved.

To China's bauxite resource and utilization of fly ash present situation; The present invention proposes a kind of aluminous fly-ash and produces the metallic aluminium process method; All different with traditional process method and thinking, managing to remove with flyash production is the intermediates process of aluminum oxide, obtains metallic aluminium by the anhydrous chlorides of rase electrolysis of aluminum; Can simplify flyash significantly and produce the technical process of aluminium, reduce investment and production cost.

Summary of the invention

The technical problem that the present invention will solve is: provide a kind of aluminous fly-ash to produce the metallic aluminium process method; This process method is combined as a whole aluminum oxide and electrolytic aluminium production process; Simplify flyash and produce the technical process of aluminium; Reduce construction investment and production cost; Make enterprise have favorable economic benefit, the lime dosage that prior art exists is huge, red mud amount big to overcome, the concentration of sodium aluminate solution is low, production energy consumption is high, perhaps removing iron from solution and removal of impurities difficult, the corrosion resistance nature of equipment and material is required high deficiency.

In order to solve described technical problem, the present invention takes following technical scheme: it comprises following process step:

The first, flyash stripping: will contain Al₂O₃The mixed in hydrochloric acid of>=38% aluminous fly-ash and 20～30% concentration is prepared into raw pulp, adopts the continuous stripping mode of preheater, autoclave insulation stripping, the aluminum oxide in the stripping flyash at high temperature, and this operation main technique technical indicator is following:

The raw pulp temperature: normal temperature, or 15～35 ℃;

Stripping temperature: 150～180 ℃;

Dissolution time: 30～60min;

Stripping pressure: 0.8～1.1mPa;

Digesting efficiency of alumina: 85～92%.

Stripping proportioning: 0.95～1.0; Promptly adopt 0.95～1.0 proportioning of aluminum oxide and other MOX in the flyash (aluminum oxide and other MOX of pressing process in leaching actual participation reaction calculate) stripping chemical reaction calculated value; The hydrochloric acid dosage requires to be lower than the chemical reaction amount, to prevent in the slip after the stripping unreacted free hydrochloric acid effusion pollutant atmosphere being arranged.

The second, acid sludge separating, washing, liquor alumini chloridi purification and impurity removal: adopt subsider as acid sludge separation, washing plant, flash liberation, 4～5 backflushs, last subsider underflow filters with pressure filter, and filter cake is the acid sludge of wash clean, send the acid sludge stockyard.The separation tank overflow is the thick liquid of aluminum chloride, purifies through controlled filter, remove various impurity with resin absorption after, obtain purified liquor alumini chloridi, with pumping spraying drying operation.Separation and washing settling groove underflow contain 250～450g/l, filter cake moisture content≤35%, leaching requirement 1.5～2.5t/t-acid sludge admittedly.

Three, spraying drying and dehydration: liquor alumini chloridi is sent in the spray-dryer, and temperature is controlled at 120～180 ℃, to obtain the Aluminum chloride anhydrous crystal grain.

Four, fused salt electrolysis: Aluminum chloride anhydrous is joined the aluminum chloride electrolyzer, and Aluminum chloride anhydrous is dissolved in the fused ionogen, and ionogen is by NaCl+LiCl+AlCl₃+ MgCl₂+ KCl+CaCl₂Mixture is formed, because of AlCl₃Electroconductibility very poor, so select the NaCl+LiCl primary structure for use, can remedy AlCl₃Bad electroconductibility.Temperature is 670～700 ℃ in the electrolyzer, direct current consumption 10000～11000kWh/t-aluminium.The aluminium liquid that electrolysis obtains send casting process to prepare aluminium ingot, and the chlorine that anode electrolytic cell produces is sent to the hydrochloric acid preparation section.

Five, preparation hydrochloric acid: the chlorine by electrolysis obtains is delivered in the building-up reactions stove of hydrogenchloride, and chlorine and hydrogen reaction obtain the hydrogenchloride flue gas, and the hydrogenchloride flue gas absorbs the hydrogenchloride hydrochloric acid that obtains soluble in water through cooling, three grades of absorption towers.With the hydrochloric acid that makes, its concentration 28～36% is sent to the stripping operation, and hydrochloric acid is formed closed cycle.

Because in the production process; Other MOXs meeting subparticipation process in leaching chemical reactions that flyash contains; And in the acid sludge separating, washing process, can a small amount of muriate of not cleaning be taken to the acid sludge stockyard, the every circulation primary of hydrochloric acid need consume a small amount of sulfuric acid in the production; So need in the production process to replenish a small amount of eo-acid, expected acid consumption is 70～90kg/t-aluminium.

It is the raw material production metallic aluminium that the present invention adopts aluminous fly-ash; Be soluble in acid according to flyash; Aluminum chloride anhydrous carries out the characteristic that electrolysis can obtain metallic aluminium under the NaCl+LiCl electrolyte system, proposed the new process that a kind of aluminous fly-ash is produced metallic aluminium.

Adopt art breading aluminous fly-ash of the present invention, can be met the aluminium ingot that national standard requires, flyash is rationally utilized; Solved also simultaneously that China's bauxite resource is not enough, flyash is to the pollution difficult problem of environment.

Description of drawings

Fig. 1: aluminous fly-ash of the present invention is produced the metallic aluminium process flow diagram.

Embodiment

Embodiments of the invention: aluminous fly-ash of the present invention is produced metallic aluminium technical process meaning as shown in Figure 1,

Its technological process is following: the aluminous fly-ash of alumina content 45%, add the hydrochloric acid of 30% concentration, and proportioning adopts aluminum oxide stripping chemical reaction Theoretical Calculation amount 1.0 values; Flyash raw pulp temperature is 25 ℃; Send into the cannula primary heater of dissolving device with the stripping fresh feed pump, material will temperature reach 88 ℃ behind sleeve preheating, be heated to 150 ℃ with the live steam cannula primary heater again; 180 ℃ of live steam temperature, pressure 1.02MPa.The raw pulp that comes out through the live steam heating muff gets into autoclave insulation stripping 45min, and in the autoclave process in leaching, digesting efficiency of alumina can reach 90% in the flyash.Stripping slurry is lowered the temperature through 3 grades of self-evaporatint n.s; Temperature gets into after 180 ℃ are reduced to 118 ℃ the dilution slurry vessel; With pump slip is sent to acid sludge separating, washing operation again, the acid sludge separating, washing adopts subsider equipment, carries out 5 grades of backflushs; Washing back acid sludge is sent to the acid sludge stockyard and stores up after pressure filter filters.The settlement separate solution that obtains is behind controlled filter; Carrying out resin absorption again purifies; Liquor alumini chloridi after will purifying then is sent to spray-dryer; Aluminum chloride anhydrous is produced in drying and dehydration under 150 ℃ of conditions, and Aluminum chloride anhydrous obtains aluminium water through fused salt electrolysis, and aluminium water obtains metal aluminium ingot product through purifying casting.Temperature is 670～700 ℃ in the electrolyzer, direct current consumption 10000～11000kWh/t-aluminium.In the electrolytic process, the chlorine that produces from anode is together sent in the hydrogen chloride synthetic reaction device with hydrogen and to be prepared hydrogen chloride gas, adopts 3 grades of cooling and absorbing towers to prepare 30% hydrochloric acid again, and hydrochloric acid returns the stripping operation batching of front, forms closed cycle.

Claims (5)

1. an aluminous fly-ash is produced the process method of metallic aluminium, and it is characterized in that: it comprises following process step:

The first, flyash stripping; Be about to contain Al₂O₃The mixed in hydrochloric acid of>=38% aluminous fly-ash and 20～30% concentration is prepared into raw pulp, adopts the continuous stripping mode of preheater, autoclave insulation stripping, at high temperature the aluminum oxide in the stripping flyash;

The second, acid sludge separating, washing, liquor alumini chloridi purification and impurity removal;

Three, spraying drying and dehydration; Be about to liquor alumini chloridi and send in the spray-dryer, temperature is controlled at 120～180 ℃, obtains the Aluminum chloride anhydrous crystal grain;

Four, fused salt electrolysis; Be about to Aluminum chloride anhydrous and join the aluminum chloride electrolyzer; Aluminum chloride anhydrous is dissolved in the fused ionogen, and temperature is 670～700 ℃ in the electrolyzer, and the aluminium liquid that electrolysis obtains send casting process; Preparation aluminium ingot after purifying, clarifying, the chlorine that anode electrolytic cell produces is sent to the hydrochloric acid preparation section;

Five, preparation hydrochloric acid; The chlorine that is promptly obtained by electrolysis is delivered in the building-up reactions stove of hydrogenchloride, and chlorine and hydrogen reaction obtain the hydrogenchloride flue gas, and the hydrogenchloride flue gas absorbs the hydrogenchloride hydrochloric acid that obtains soluble in water through cooling, three grades of absorption towers.

2. aluminous fly-ash according to claim 1 is produced the process method of metallic aluminium, and it is characterized in that: the main technique technical indicator in first process step is following:

The raw pulp temperature: normal temperature, or 15～35 ℃;

Stripping temperature: 150～180 ℃;

Dissolution time: 30～60min;

Stripping pressure: 0.8～1.1mPa;

Digesting efficiency of alumina: 85～92%;

The stripping proportioning: 0.95～1.0, promptly adopt 0.95～1.0 proportioning of aluminum oxide and other MOX stripping chemical reaction calculated value in the flyash, the hydrochloric acid dosage requires to be lower than the chemical reaction amount.

3. aluminous fly-ash according to claim 1 is produced the process method of metallic aluminium; It is characterized in that: in second process step, adopt subsider as acid sludge separation, washing plant, flash liberation; 4～5 backflushs; Last subsider underflow filters with pressure filter, and filter cake is the acid sludge of wash clean, send the acid sludge stockyard; The separation tank overflow is the thick liquid of aluminum chloride, purifies through controlled filter, remove various impurity with resin absorption after, obtain purified liquor alumini chloridi, with pumping spraying drying operation; Separation and washing settling groove underflow contain 250～450g/l, filter cake moisture content≤35%, leaching requirement 1.5～2.5t/t-acid sludge admittedly.

4. aluminous fly-ash according to claim 1 is produced the process method of metallic aluminium, and it is characterized in that: in the 4th process step, ionogen is by NaCl+LiCl+AlCl₃+ MgCl₂+ KCl+CaCl₂Mixture is formed; Electrolyzer direct current consumption 10000～11000kWh/t-aluminium.

5. aluminous fly-ash according to claim 1 is produced the process method of metallic aluminium, and it is characterized in that: in the 5th process step, the concentration of hydrochloric acid that makes is 28～36%, is sent to the stripping operation, and hydrochloric acid is formed closed cycle.

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