A kind of by flyash extraction method of alumina
Technical field
The present invention relates to a kind ofly extract method of alumina, more particularly, relate to a kind of method of handling aluminous fly-ash extraction metallurgical-grade aluminum oxide with hydrochloric acid-bayer's process by flyash.
Background technology
Produce about 7,000 ten thousand tons of aluminum oxide every year in the world at present, and it is raw material that each alumina producer almost adopts bauxite entirely.China is maximum in the world alumina producing state, produces about 2,100 ten thousand tons of aluminum oxide, and accounts for 30% of Gross World Product in 2008.But China's bauxite resource is poor relatively, and the bauxite reserves only account for about 6% of world's total reserves, and ore grade is lower, and ore type is main with unmanageable diaspore mainly, complex treatment process, energy consumption height, and production cost is also higher.Because China's bauxite resource is not enough, China's import bauxite ore was about 2,500 ten thousand tons in 2008, accounted for about 50% of domestic bauxite usage quantity.Ore resource is not enough, has had a strong impact on the development of China's aluminum oxide industry, seeks new aluminum oxide industry raw material, researchs and produces the task of top priority that the new Technology of aluminum oxide becomes China's aluminium industrial development.
Coal resources in China is very abundant, and coal production accounts for the first in the world, more than 20 hundred million tons of coals of annual output, and the coal major part is used for thermal power plant's generating, will discharge a large amount of flyash behind the coal burning, and China's annual approximately discharging aluminous fly-ash (refers to Al in the flyash
2O
3>=38wt%) more than 100,000,000 tons.Analyze after deliberation; Aluminous fly-ash mainly is made up of aluminum oxide, silicon oxide; The content of 2 kinds of compositions accounts for 80wt%, and other compositions such as iron content, magnesium, titanium, calcium also contain abundant rare precious metals such as gallium in the flyash that has in addition; Be the raw material that metallurgical-grade aluminum oxide and GALLIUM metal pure 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 ground outputs such as Shanxi, Shaanxi, Inner Mongol, Ningxia usually about 40wt%; Belong to aluminous fly-ash, in the Erdos area flyash of the Inner Mongol there be alumina content up to 45~50wt%, almost with external bauxite trihydrate in alumina content suitable; From chemical composition analysis, can be used as one of raw material that extracts metallurgical-grade aluminum oxide 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, be unfavorable for the safe operation in lime-ash stockyard, also increased the production cost of power plant.The coastland because populous, industry is flourishing, sometimes with flyash be used to build the road, material of construction such as brickmaking, this only belongs to low-grade, low value-added application, 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, to the present situation of China's bauxite resource wretched insufficiency, many scientific research departments of China and universities and colleges actively develop non-bauxite resource production metallurgy grade aluminum oxide research, and emphasis is a research aluminous fly-ash comprehensive utilization production metallurgy grade aluminum oxide.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 big, the concentration of sodium aluminate solution is low, production energy consumption is high, and its investment and cost are high.
(2) acid system: mainly contain 2 kinds of sulfuric acid process, salt acid systems.Promptly adopt sulfuric acid or hydrochloric acid and aluminous fly-ash to prepare burden in proportion; Aluminum oxide under certain temperature and pressure in the stripping flyash; Obtain purified aluminum salt solution through slagging-off and deironing then; Obtain alumina product through evaporation, roasting, its advantage is that flow process is simple, the quantity of slag is little, production cost is low.Shortcoming is that deironing and removal of impurities are difficult, and alumina product quality and traditional national standard have difference, and some technological problemses still need be studied and tested.
Patented claim CN 1927716A discloses method of alumina in a kind of extraction flyash; Its advantage is to have concentrated acid system and alkaline process to prepare the advantage of aluminum oxide; But owing to receive the restriction of processing unit; There is following problems in this method: adopt the unreasonable economically evaporization process that causes of " carrying out negative pressure in the concentration tank concentrates " technology industriallization to use, can only be used for laboratory study; Slip after the stripping in subsider, separate and wash after obtain soaking slag liquid contain rate up to 70~80wt%, directly be sent to the waste residue stockyard, big to surrounding environment influence; Acid stripping temperature is 90~110 ℃, finds that through test the hydrochloric acid solubility rate of aluminum oxide has only about 60% the too low manufacturing cost of aluminum oxide that then increased of solubility rate under this temperature.Improve the solubility rate that the stripping temperature can improve aluminum oxide in the flyash, but high temperature stripping meeting increases the weight of acid to corrosion on Equipment.Therefore be necessary to research and develop a kind of reliable process method with the result of extraction that improves aluminum oxide in the flyash and solve under the high temperature hydrochloric acid medium to the corrosion on Equipment problem.
Summary of the invention
The objective of the invention is provides a kind of method that adopts hydrochloric acid-Bayer process from flyash, to extract metallurgical-grade aluminum oxide to deficiency of the prior art.The alumina product that makes through method provided by the invention is the metallurgical grade first grade (n YS/T274-1998) that complies with the national standard requirements, and can satisfy electrolytic aluminum industry request for utilization fully.
Method provided by the invention comprises the steps:
A) acidic process: hydrochloric acid and flyash batching and the digester of sending into the inner liner polytetrafluoroethylene material are carried out stripping; The slip of stripping obtains active just aluminum oxide and hydrogen chloride gas through separation, evaporative crystallization, roasting decomposition;
B) Bayer process is handled: the active aluminum oxide just that obtains in the step a) is prepared burden with circulating mother liquor and sent into autoclave and carry out stripping, ratio of components α
kBe 1.35~1.55, while feeding-in liquid caustic alkali, the caustic sodium concentration Na in the said circulating mother liquor
2O
kBe controlled at 160~230g/l; The slip of stripping is after separation, smart filter, and gained seminal fluid and aluminium hydroxide crystal seed carry out kind of a branch decomposition and obtain white lake and decomposition nut liquid in decomposer; Said decomposition nut liquid returns active aluminum oxide stripping operation just and uses as circulating mother liquor after evaporation, said white lake obtains the metallurgical-grade aluminum oxide product through filtration, washing, roasting.
According to method provided by the invention, adopt flyash and hydrochloric acid reaction raw materials in the said step a), the Al of said flyash as the stripping reaction
2O
3Content>=38wt%, the concentration of said hydrochloric acid is 25~31wt%.
According to method provided by the invention, wherein, the flyash in the step a) is taked the mode of continuous stripping, the stripping temperature is 140~160 ℃, dissolution time is 1~2 hour, preferably under alr mode, flyash is carried out stripping, wherein Al
2O
3Solubility rate>=80%.
According to method provided by the invention, wherein settlement separate in subsider through the slip of step a) stripping, underflow is an acid sludge, and overflow is the thick liquid of aluminum chloride; Said acid sludge gets into rinse bath, carries out backflush 4~6 times with 60~85 ℃ hot water, and the add-on of hot water is 1.5~2.5t/t acid sludge, and the washing lotion behind the washing acid sludge is used for diluting the slip of digester stripping; Acid sludge after the last washing after filtering, gained filtrating is returned in the rinse bath and is recycled, the water ratio≤35wt% of gained filter cake is sent to the waste residue stockyard with filter cake.
According to method provided by the invention, wherein, the thick liquid of said aluminum chloride is imitated pump feed evaporator through 2~4 and is evaporated, and removes the moisture in the thick liquid of aluminum chloride and makes aluminum chloride with AlCl
36H
2The crystallization of O form is separated out.
According to method provided by the invention, wherein, adopt rotary kiln or fluidized roaster to AlCl
36H
2Roasting is carried out in the O crystallization, and maturing temperature is 600~800 ℃, and aluminum chloride resolves into active just aluminum oxide and hydrogen chloride gas, Al in the first aluminum oxide of said activity
2O
3Content>=92wt%.
According to method provided by the invention, wherein, the hydrogen chloride gas in the said step a) returns flyash stripping operation and recycles after the hydrochloric acid that concentration is 25~31wt% is processed on 2~3 grade hydrochloric acid absorption towers.
According to method provided by the invention, wherein, the active stripping temperature of aluminum oxide just is 210~250 ℃ in the said step b), is preferably 230~240 ℃, and stripping pressure is 1.8~4.0MPa, is preferably 2.3~3.4MPa, and dissolution time is 0.5~1.5 hour.
Preferably, the mixed slurry of first aluminum oxide of said activity and circulating mother liquor carries out stripping under alr mode, Al in the active aluminum oxide just
2O
3Solubility rate>=93%.
According to method provided by the invention, wherein settlement separate in subsider through the slip of step b) stripping, underflow is a red mud, makes seminal fluid through overflow being carried out the essence filter; Content≤15mg/l of seston in the said seminal fluid; Said red mud gets into rinse bath; Carry out backflush 3~5 times with 80~90 ℃ hot water; The add-on of hot water is 2~4t/t red mud, and the washing lotion of washing behind the red mud is used for diluting the slip of autoclave stripping, interior temperature>=85 of subsider and rinse bath ℃; Red mud after the last washing after filtering, gained filtrating is returned rinse bath and is recycled, the water ratio≤35wt% of gained filter cake is sent to the waste residue stockyard with filter cake.
According to method provided by the invention, wherein, the add-on of aluminium hydroxide crystal seed is 500~850g/l in the said step b); The decomposer groove number that adopts is 12~16, and decomposing first-cell temperature is 59~72 ℃, and last groove temperature is 48~60 ℃; Resolving time is 38~45 hours, Al in the said seminal fluid
2O
3Rate of decomposition be 46~51%.
According to method provided by the invention, adopt multiple-effect falling film formula vaporizer or full flash vaporizer that the decomposition nut liquid in the step b) is evaporated, the mother liquor after the evaporation returns active aluminum oxide stripping operation just and uses as circulating mother liquor.
According to method provided by the invention, the white lake that obtains in the step b) obtains the metallurgical-grade aluminum oxide product after carrying out fluosolids roasting under 950~1100 ℃.
Compared with prior art, the present invention can overcome the technological deficiency that prior art is handled the aluminous fly-ash aluminium oxide extraction process, has following advantage:
(1) the stripping temperature of available technology adopting salt s.t. flyash is merely 90~110 ℃; Cause the solubility rate of aluminum oxide to have only 60%, the inventive method adopts the digester of inner liner polytetrafluoroethylene material and through stirring the mode of stripping, the stripping temperature is increased to 140~160 ℃; The solubility rate of aluminum oxide reaches more than 80%; Greatly improve result of extraction, improved the utilization of coal ash rate, had bigger economic benefit.
(2) subsider underflow acid sludge and red mud are being carried out in the process of backflush, the present invention adopts hot wash can keep system's heat balance, keeps the higher solubility of aluminum chloride in the solution, aluminum oxide, reduces soltion viscosity, helps the slag sedimentation; And acid sludge and red mud after the present invention washs last filter with filter; Water ratio≤the 35wt% of control filter cake can further reclaim filtrating, reduces discharging of waste liquid; Waste residue volume-diminished after the filtration; Save the stacking space of slag field, both effectively prolonged the working life of traditional slag field, practiced thrift valuable land resources again.
(3) in the methods of the invention, AlCl
36H
2O crystalline maturing temperature is 600~800 ℃, can make aluminum chloride crystalline dehydration reaction complete, and the cl ions of avoiding being mingled with in the active aluminum oxide just produces adverse influence to follow-up alkali process, equipment, has guaranteed the active activity of aluminum oxide just simultaneously.
(4) in the methods of the invention, through under alr mode, utilizing circulating mother liquor and replenishing small amount of liquid caustic alkali the first aluminum oxide of activity is carried out stripping, make Al in the active aluminum oxide just
2O
3Solubility rate>=93%, economic benefit is particularly considerable.
(5) decomposition nut liquid that obtains after kind of branch is decomposed of the present invention adopts multiple-effect falling film or full flash evaporation technology, can get rid of redundant moisture in the flow process, has guaranteed the water balance of production technique system.
Terminological interpretation:
" active aluminum oxide just " among the present invention is meant Al
2O
3The intermediate product of content>=92wt%.
" caustic sodium concentration Na among the present invention
2O
k" being meant the concentration of the sodium oxide that exists with the caustic alkali form in " circulating mother liquor ", unit is g/l.
" ratio of components α among the present invention
k" also refer to the causticization coefficient or the caustic ratio of sodium aluminate solution, the mol ratio of contained caustic alkali and aluminum oxide in the expression solution, method of calculation are α
k=1.645 * (caustic sodium concentration Na
2O
k/ alumina concentration), wherein alumina concentration unit is g/l.
" plant divide decompose " among the present invention be meant in oversaturated sodium aluminate solution and add aluminium hydroxide crystal seed, makes aluminum oxide in the sodium aluminate solution with the form process that crystallization is separated out from solution of white lake.
" decomposition nut liquid " among the present invention is meant the solution that oversaturated sodium aluminate solution obtains after " plant and decompose " separated out white lake.
" circulating mother liquor " among the present invention is meant that " decomposition nut liquid " returns the mother liquor that active aluminum oxide stripping operation just recycles after evaporation.
Description of drawings
Fig. 1 is the process flow diagram according to the inventive method.
Embodiment
Below in conjunction with accompanying drawing and specific embodiment the present invention is described further, still, the present invention is not limited in following examples.
Embodiment 1
Al by 85%
2O
3Solubility rate calculates the consumption of hydrochloric acid, with the aluminous fly-ash (Al of coal gangue power plant of accurate ability company of Shenhua
2O
3Content 48.2wt%, SiO
2Content 38.33wt%) is that the hydrochloric acid batching of 28wt% is processed the flyash slip with concentration, is sent to the digester of inner liner polytetrafluoroethylene material, under 150 ℃ of conditions, stopped 1.5 hours and constantly stir; The slip of stripping is sent to subsider carries out flash liberation, the underflow acid sludge of subsider gets into rinse bath, carries out backflush 5 times with 85 ℃ of hot water; The hot water add-on is the 2.0t/t acid sludge; Washing lotion behind the washing acid sludge can be diluted the slip of stripping, and the acid sludge after the last washing filters through filter, and filtrating is returned rinse bath; Water ratio≤the 35wt% of control filter cake; Said filter cake is sent to the waste residue stockyard, the subsider overflow is sent to 3 imitates pump feed evaporator, after evaporation concentration, obtain AlCl
36H
2The O crystallization obtains active just aluminum oxide, wherein Al through fluosolids roasting under 700 ℃
2O
3Content be 93wt%, the hydrogen chloride gas that produces in the roasting process is sent to 2 grade hydrochloric acid absorption towers and is prepared into the hydrochloric acid that concentration is 28wt%, return hydrochloric acid stripping operation and flyash the batching.
With first aluminum oxide of said activity and caustic sodium concentration Na
2O
kBe the circulating mother liquor batching of 200g/l, ratio of components α
kBe 1.40, be mixed with ore pulp and be sent to autoclave and carry out stripping that under 220 ℃ of conditions, stopped 1.5 hours and constantly stir, stripping pressure is 2.3MPa, the wherein active contained Al of aluminum oxide just
2O
3Solubility rate be 93%, the slip of stripping is sent to subsider carries out flash liberation, the underflow red mud of subsider gets into rinse bath; Carry out backflush 4 times with 90 ℃ of hot water, the hot water add-on is the 3t/t red mud, and subsider and rinse bath temperature are 90 ℃; Washing lotion behind the washing red mud can be diluted the slip of stripping; Red mud after the last washing filters through filter, and the water ratio≤35wt% of gained filter cake is sent to the waste residue stockyard with filter cake.The subsider overflow filters seminal fluid through essence, and the content of its seston is 12mg/l, and said seminal fluid is mixed with aluminium hydroxide crystal seed, forms aluminum hydroxide slime, and the content of crystal seed is 800g/l in the aluminum hydroxide slime, gets into decomposer and carries out kind of a branch decomposition.Adopt 13 decomposers, decomposing first-cell temperature is 61 ℃, and last groove temperature is 53 ℃, and the resolving time is 45 hours, Al
2O
3Rate of decomposition be 50%.Plant branch and decompose the decomposition nut liquid warp 5 effect falling film evaporations that obtain, the mother liquid evaporation that obtains returns the first aluminum oxide stripping operation of activity and uses as circulating mother liquor; The white lake that the kind decomposition obtains carries out fluosolids roasting through filtration washing under 1050 ℃ maturing temperature, obtain qualified metallurgical-grade aluminum oxide product, wherein Al
2O
3Content be 98.6wt%.
Embodiment 2
Al by 80%
2O
3Solubility rate calculates the consumption of hydrochloric acid, the aluminous fly-ash that power plant's fluidized-bed combustion boiler is produced (Al
2O
3Content 42.5wt%, SiO
2Content 40.38wt%) be that the hydrochloric acid batching of 25wt% is processed the flyash slip with concentration, be sent to embodiment 1 in identical digester, under 142 ℃ of conditions, stopped 2.0 hours and constantly stir; The slip of stripping is sent to subsider carries out flash liberation, the underflow acid sludge of subsider is sent into rinse bath, carry out backflush 6 times with 80 ℃ of hot water; The hot water add-on is the 2.5t/t acid sludge; Washing lotion behind the washing acid sludge can be diluted the slip of stripping, and the acid sludge after the last washing filters through filter, and filtrating is returned rinse bath; Water ratio≤the 35wt% of control filter cake; The gained filter cake is sent to the waste residue stockyard, the subsider overflow is sent to 4 imitates pump feed evaporator, after evaporation concentration, obtain AlCl
36H
2The O crystallization obtains active just aluminum oxide, wherein Al through fluosolids roasting under 800 ℃
2O
3Content be 92wt%, the hydrogen chloride gas that produces in the roasting process is sent to 2 grade hydrochloric acid absorption towers and is prepared into the hydrochloric acid that concentration is 25wt%, return hydrochloric acid stripping operation and flyash the batching.
With first aluminum oxide of said activity and caustic sodium concentration Na
2O
kBe the circulating mother liquor batching of 220g/l, ratio of components α
kBe 1.35, be mixed with ore pulp and be sent to autoclave and carry out stripping that under 245 ℃ of conditions, stopped 1.0 hours and constantly stir, stripping pressure is 3.5MPa, the wherein active contained Al of aluminum oxide just
2O
3Solubility rate be 95%, carry out flash liberation at the bottom of the slip of stripping is sent to subsider, the underflow red mud of subsider gets into rinse bath; Carry out 5 washings with 85 ℃ of hot water, the hot water add-on is the 2.5t/t red mud, and subsider and rinse bath temperature are 90 ℃; Washing lotion behind the washing red mud can be diluted the slip of stripping; Red mud after the last washing filters through filter, and the water ratio≤35wt% of control filter cake is sent to the waste residue stockyard with the gained filter cake.The subsider overflow filters seminal fluid through essence, and the content of its seston is 15mg/l, and said seminal fluid mixes with aluminium hydroxide crystal seed, forms aluminum hydroxide slime, and the content of crystal seed is 820g/l in the aluminum hydroxide slime, gets into decomposer and carries out kind of a branch decomposition.Adopt 15 decomposers, decomposing first-cell temperature is 70 ℃, and last groove temperature is 56 ℃, and the resolving time is 42 hours, Al
2O
3Rate of decomposition be 48%.Kind divide to decompose the decomposition nut liquid that obtains through full flash evaporation, the mother liquid evaporation that obtains returns active aluminum oxide stripping operation just and uses as circulating mother liquor.The white lake that the kind decomposition obtains carries out fluosolids roasting through filtration washing under 1020 ℃ maturing temperature, obtain qualified metallurgical-grade aluminum oxide product, wherein Al
2O
3Content be 98.8wt%.