CN103038174B - Process for recovery of alumina using tricalcium aluminate - Google Patents
Process for recovery of alumina using tricalcium aluminate Download PDFInfo
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- CN103038174B CN103038174B CN201180022301.9A CN201180022301A CN103038174B CN 103038174 B CN103038174 B CN 103038174B CN 201180022301 A CN201180022301 A CN 201180022301A CN 103038174 B CN103038174 B CN 103038174B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
- C01F7/14—Aluminium oxide or hydroxide from alkali metal aluminates
- C01F7/141—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by neutralisation with an acidic agent
- C01F7/142—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by neutralisation with an acidic agent with carbon dioxide
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/18—Carbonates
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/141—Feedstock
Abstract
A process for recovering alumina values from a caustic aluminate solution is disclosed. The process comprises the steps of: a) introducing a source of carbon dioxide to the caustic aluminate solution in the presence of aluminium hydroxide seed crystals to form a first treated stream comprising carbonate ions in solution and aluminium hydroxide in solid form; b) subjecting the first treated stream of step a) to solid/liquid separation to recover alumina values in the form of aluminium hydroxide and produce a first clarified treated stream; and, c) mixing the first clarified treated stream of step b) with tricalcium aluminate to form a second treated stream comprising calcium carbonate in solid form, aluminate ions in solution, and hydroxyl ions in solution.
Description
Technical field
The present invention relates to and use TCA to reclaim the method for oxidation aluminum values from caustic aluminate solution.
Background technology
In upper a century, Bayer process is for reclaiming oxidation aluminum values from bauxitic ore.The core of the method is following reversible equation, for gibbsite and boehmite or diaspore ore, is respectively (1):
Figure 1 illustrates the block diagram of the basic embodiment showing traditional Bayer process.First a part for mixed bauxite and the waste liquid of recirculation mixes, and stands grinding to reduce granularity.Then the soluble silica mineral that the slurry generated via the art breading being known as " desiliconization " or " holding slurry (slurry holding) " is present in bauxite with removal, typically with the form of insoluble sodium silicoaluminate.
Then the slurry of desiliconization and remaining waste liquid mix, via being called that the technique of " digestion (digestion) " extracts the oxidation aluminum values of bauxite.In digestion, manipulation condition is to advance equation (1) or (2) towards right hand side.Between the period of digestion, in free caustic fusion bauxite, aluminiferous mineral are to form concentrated sodium aluminate solution, be left behind body refuse and the impurity of non-dissolution of minerals, it is passive iron oxide compound, oxyhydroxide, (oxidation) oxyhydroxide, titanium oxide and silicon-containing compound mainly.Usually owing to there is iron mineral, body refuse appearance is red, is thus commonly referred to " red soil ".By using the condition promoting digestion of high temperature and high pressure, and these so that depend on the ore type of process.The balance that equation (1) and (2) represent also can be moved to right hand side by the concentration improving free caustic alkali (hydroxide ion).
After flash cooling, in the technique being called " clarification ", mother liquor is separated with body refuse.By slurry feed in one or more settling tank, wherein solid particles sediment is removed, typically via being pumped to mud cycles of washing to bottom.Assist being separated of mud and concentrated solution with flocculation agent, " former (the green) " liquid (or mother liquor) simultaneously only containing the meticulousst suspended solids overflows mud settling sump.
Then usually typically pressure filter is used, by filtering the liquid that clarification is further separated out.The step that it is called " filtering (polishing) " filters is guaranteeing that during mother liquor is not containing the mud in suspension particle causing product alumina to pollute in addition be crucial.Independently, the cloth adopted in these strainers blocks as quick as thought.Occur this is because the meticulous suspended solids in settling vessel overflow is absorbed in the knitmesh of filter cloth, then continue on the surface of strainer to form dense resistive formation.
In order to prevent this problem, usually with " flocculating aids " to filtering strainer supply feed, the effect of this flocculating aids prevents from being formed continuously the Solid Bed that mud particle is absorbed in block filter cloth, also makes liquid pass through the backlash freedom flowing of bed simultaneously.Desirable flocculating aids by be cheap, chemically inert, size be its mud particle can be made to be absorbed in and not confined liquid flowing or promote the blocking of filter cloth self.In most alumina refinery, this effect is undertaken by tricalcium aluminate (also referred to as TCA, C3A or C3AH6).
Mud cycles of washing depends on counter-current decantation technique to reclaim the sodium aluminate re-used as far as possible, to make the minimization of loss of aluminum oxide and causticity base number, and purifies body refuse so that its mode can allowed with environment is discarded.Make the washer overflow of flowing out first paragraph mud wash trough subsequently flow into settling tank, or mix with settling vessel spillage the mother liquor forming clarification.Typically, by the final stage of mud cycles of washing, the body refuse of washing is evacuated to mud emission pond.Adverse current mud cycles of washing washing water, the recirculated water (being called " Chi Shui (lakewater) ") typically in fresh water, phlegma (condensed steam) or mud emission pond or above-mentioned combination supply.
Before delivering to precipitating phase, the clarified mother liquor of spilling settling tank is made to stand filtration described above.In precipitating phase, the balance of equation (1) (again copying hereinafter) is impelled to move towards left-hand side to form pure Al (OH)
3, also referred to as " gibbsite ".
Via the gibbsite of hydrocyclone, thickening material or strainer precipitation separation.Remaining liquid, evaporation is called " waste liquid " after removing excessive water, these excessive waters enter in technique along with bauxite and various washing step, and will containing aluminate ion and hydroxide ion, the amount of existence depends on temperature, the surface-area of crystal seed (seed) and the residence time of precipitating phase.Precipitation is promoted, as the concentration or the diluting soln that reduce temperature, add gibbsite crystal seed, improve aluminate ion by the oversaturated condition of increase liquid.In order to reclaim oxidation aluminum values and caustic alkali, recirculation waste liquid is with digestion.Thus the aluminum oxide containing dissolving through recirculation with the waste liquid of digestion is present in wherein.
According to the gibbsite crystallization classification that large young pathbreaker is formed during precipitating, fire product level material in rotary kiln or fluidized bed calcination stove, the particle of undergage is used as " crystal seed " simultaneously, and it contributes to the precipitation in the diaspore crystallization of precipitate phase period three.Firing period, gibbsite dehydroxylation is to form aluminum oxide.Meanwhile, the carbonic acid gas of generation is the by product of the combustion of fossil fuel for running calcining furnace.Also in stack gas, discharge carbonic acid gas, these stack gases produce with the power house powered to alumina refinery by running, and also can be produced by limestone kiln in some alumina refinery.At this moment waiting, there is restriction in the option that can be used for affecting the discharge of firing the greenhouse gases that period produces.
The major objective of Bayer process is from being supplied to solution to extract the oxidation aluminum values (Al) of maximum the bauxite of digestion economically, then reclaiming these aluminum oxide dissolved completely with the form precipitating period three diaspore from solution.The upper limit of refinery's precipitation productive rate (output) be by digestion temperature in particular liquid aluminum oxide solubleness and at the temperature for precipitating in liquid aluminum oxide solubleness between difference determine.Then thus conclude, the major objective of most of alumina refinery is that this species diversity is maximized.
In alumina refinery, a main path of alumina loss to be evacuated to from settling tank with body refuse in the liquid in mud cycles of washing.The liquid of this oversaturated mother liquor has the aluminate ion with the mother liquor same concentrations delivering to precipitation effectively.The liquid overflowed in each stage of adverse current mud cycles of washing becomes more dilution with more ice-cold gradually with washing water.This improves the supersaturation of liquid effectively, promotes the precipitation of the gibbsite according to equation (1).Mud particle in resistates has high surface-area, and it promotes this precipitation of gibbsite in mud cycles of washing further.Have lost any aluminum oxide precipitated by this way in mud cycles of washing, as the aluminum oxide of dissolving any in the liquid delivering to mud emission pond.
Another approach of alumina loss is that aluminum oxide is integrated with in TCA flocculating aids, uses this TCA flocculating aids to remove the fine solid suspended during clarifying.Along with the past of time, TCA flocculating aids was easily polluted by the external foreign matters and became " useless (using) ".TCA is relatively inexpensive and easily produces.Under suitable condition, the calcium with the Suitable sources from such as white lime is reacted to form thermodynamically stable and sl. sol. TCA by caustic aluminate solution.The most often use this reaction to produce the TCA crystal of Control granularity in aluminum oxide industry, to be used as flocculating aids.In a lot of alumina refinery, useless TCA flocculating aids is pumped down to red soil treatment zone, and can mean annual 40 to 90 for typical refinery, the loss of the oxidation aluminum values of 000 ton of (quantity) level.By this way, useless flocculating aids means that alumina refinery stores or discarded weight most " solid basicity " usually.
Need the maximized alternative method of oxidation aluminum values making to reclaim in alumina refinery.
Summary of the invention
According to an aspect of the present invention, provide the method for reclaiming oxidation aluminum values from caustic aluminate solution, the method includes the steps of:
A) under aluminium hydroxide crystal seed exists, in caustic aluminate solution, introduce carbon dioxide source flow with the first process forming the carbanion that comprises in solution and aluminium hydroxide in solid form:
B) make first of step a) the process flow through by solid/liquid separation to reclaim the oxidation aluminum values of aluminium hydroxide form, and produce the first clarifying treatment stream; And
C) the first clarifying treatment stream of step b) and tricalcium aluminate are mixed to be formed second of the calcium carbonate, the aluminate ion in solution and the hydroxide ion in solution that comprise solid form to process and flow.
In one form, at the temperature being not less than 50 ° of C, step c) is carried out.In another form, be not less than 50 ° of C and carrying out step c) at the temperature of the atmospheric boil do not flowed higher than the first process.In another form, heating steps b) the first clarifying treatment stream to carry out step c) at 50 ° of C and not higher than the temperature in the scope of atmospheric boil.
Preferably, caustic aluminate solution is Bayer liquor.In one form, Bayer liquor be following one or more: the overflow stream of useless Bayer liquor, mud washing section or pond current.
In one form, the aluminium hydroxide reclaimed in step b) is made to stand to sieve the aluminium hydroxide crystal seed source to produce for being recycled to step a).
In one form, the aluminium hydroxide crystal seed of step a) is three aluminium hydroxide crystal seeds.Alternatively, wherein, the aluminium hydroxide crystal seed of step a) is boehmite or gibbsite crystal seed.
In one form, the method comprise make second of step c) process flow through by solid/liquid separation with removes calcium carbonate and generation the second clarifying treatment stream step d).
In one form, the method comprises further and processes the calcium carbonate removed in step d) to produce the step of lime.
In one form, the position that the method is included in digestive organ (digester) downstream and settling vessel upstream further makes the second clarifying treatment stream be back to the step of alumina refinery.
In one form, caustic aluminate solution has ' S ' concentration of 20 to 350g/L or 20 to 100g/L.
In one form, the tricalcium aluminate used in step c) is TCA flocculating aids or useless TCA flocculating aids.
According to a second aspect of the invention, with reference to drawings and Examples, and as illustrated, provide the method for reclaiming oxidation aluminum values substantially as described in this article wherein.
Accompanying drawing explanation
For the ease of understanding feature of the present invention in more detail, only by way of example, with reference to accompanying drawing, will several embodiments of method and apparatus be described in detail now, wherein:
Fig. 1 is the simplification conceptual flow chart of the basic embodiment of traditional prior art Bayer process;
Fig. 2 is the simplification conceptual flow chart of the embodiment illustrated for reclaiming the method according to aluminum oxide of the present invention;
Fig. 3 illustrates for RWB and AC two campaign, the C/S comparative result in time of embodiment 1;
Fig. 4 illustrates the result of the matrix test program of embodiment 2, shows under constant ' S ' of 17.9g/L, final ' C ' under 30 ° of C, 60 ° of C and 95 ° C;
Fig. 5 shows the result of the matrix test program of embodiment 2, shows under constant ' S ' of 37.1g/L, final ' C ' under 30 ° of C, 60 ° of C and 95 ° C;
Fig. 6 illustrates the result of the matrix test program of embodiment 2, shows under constant ' S ' of 56.5g/L, final ' C ' under 30 ° of C, 60 ° of C and 95 ° C;
Fig. 7 illustrates the result of the matrix test program of embodiment 2, shows under constant ' S ' of 81.4g/L, final ' C ' under 30 ° of C, 60 ° of C and 95 ° C; And
Fig. 8 illustrates the result of the matrix test program of embodiment 2, shows under constant ' S ' of 100.7g/L, final ' C ' under 30 ° of C, 60 ° of C and 95 ° C.
Embodiment
Whole specification sheets employs normally used various term in aluminum oxide industry.In order to clear, these terms of definition now.
The term " liquid " that whole specification sheets uses refers to and comprises aluminate (Al (OH)
4 -) ion and hydroxide radical or " causticity " (OH
-) any solution of ion.In Bayer liquor, main component is sodium aluminate (NaAl (OH)
4) and sodium hydroxide (NaOH).
' A ' refers to the alumina concentration of liquid, and more particularly the concentration of sodium aluminate in liquid, is expressed as equivalent aluminum oxide (Al
2o
3) g/L.
' C ' refers to the caustic sodium concentration of liquid, and it is sodium aluminate and the sodium hydrate content sum of liquid, is expressed as the g/L concentration of equivalent sodium carbonate.
Thus ' A/C ' is alumina concentration and the ratio of caustic sodium concentration.
" free caustic alkali " is that C-A(caustic sodium concentration deducts alumina concentration), C and A is expressed as the g/L concentration of equivalent sodium carbonate separately.
Any liquid stream after term " waste liquid " refers to gibbsite precipitating phase and before digestion.Typically waste liquid has low A/C ratio.Liquid after term " stoste " or " mother liquor " refer to digestion and before precipitation.Typically mother liquor has high A/C ratio.
" Chi Shui " be with collect rainwater be mixed in together with the clarified liq stream being back to refinery from mud emission pond (if use).Typically pond glassware for drinking water has the minimum A of any liquid stream.Due to the reaction of the carbonic acid gas in Chi Shui and air, typically pond glassware for drinking water has high carbonate concentration.
" S " refers to alkali concn, or more particularly " C " and actual concentration of sodium carbonate sum, and again, this adds and is expressed as the g/L concentration of equivalent sodium carbonate.Therefore, S-C(alkali concn deducts caustic sodium concentration) give in liquid with the actual concentrations (Na of the sodium carbonate of g/L
2cO
3).
The carbonate impurities level of Bayer liquor is with the ratio of caustic alkali with sodium carbonate, or ' C/S ' represents.(not carbonato) bayer process liquor of complete causticization will have the C/S ratio of 1.00.
The term " aluminium hydroxide " used in whole specification sheets refers to the crystallization shape or amorphous compound that are made up of aluminum ion and hydroxide ion.An example of ' aluminium hydroxide ' is ' gibbsite ', and it is for having general formula Al (OH)
3three aluminium hydroxides.Sometimes gibbsite also means " hydrate " or " hibbsite " or three aluminium hydroxides in the literature ", the chemical formula Al of mistake in sometimes
2o
33H
2o represents.Term ' aluminium hydroxide ' also broadly enough cover ' boehmite (boehmite) ', it is single aluminium hydroxide.
Term ' crystal seed ' refers to the particle that general size is less than the Product size of nominal.The function of crystal seed is two kinds.First, crystal seed promotes/strengthens the generation of gibbsite, and secondly, crystal seed promotes the growth compared with macrocrystal.
' calcite ' is calcium carbonate (CaCO
3).
' TCA ' is tricalcium aluminate Ca
3[Al (OH)
6]
2, in Cement industry symbol, it also uses chemical formula 3CaOAl usually
2o
36H
2o, (TCA6) or C3AH6 write.In a lot of alumina refinery, TCA is obtainable as the by product of causticization.When using factory's liquid to prepare TCA, it can comprise impurity by making the anionic impurity be present in factory's liquid be incorporated in lattice." synthesis TCA " is in pure sodium aluminate solution instead of the material that uses factory's liquid to produce, because of but pure tricalcium aluminate.
" useless flocculating aids " refers to the TCA being used as flocculating aids in alumina refinery, and it is based on periodically discarded flocculating aids at the end of the cycle of operation of pressure filtration.About this point, useless flocculating aids keeps the chemical formula of TCA, and may be polluted by meticulous red mud solids.
" TS " refers to the sodium salt sum in all solution, is expressed as the sodium carbonate equivalent concentration with g/L.
Term ' autoprecipitation ' is commonly referred to as the growth of aluminium hydroxide and the generation of not accelerating oxidation aluminium.
" causticization " is the normally used term of technician in Bayer process field, to describe the method, by the method by adding white lime and precipitating insoluble calcium carbonate, removes carbonate, and replace with oxyhydroxide from Bayer liquor.As the term " causticization " used in whole specification sheets, broadly refer to and wherein from liquid, remove impurity anions and any method of replacing with hydroxide ion.
With reference to figure 2, describe now according to one embodiment of the present invention for reclaiming the method (10) of oxidation aluminum values.In this embodiment, under aluminium hydroxide crystal seed (16) exists, in the first reactor (18), in caustic aluminate solution (14), introduce carbon dioxide source (12) to form the first process stream (20) comprising the carbanion in solution and aluminium hydroxide in solid form.Any suitable device can be used, such as bubble systems, in the first reactor (18), introduce carbon dioxide source (12).Carbon dioxide source can be any purity.Suitable source comprises the carbonic acid gas in ' stack gas ' being present in flue or produced by power house or calcining furnace or is present in the carbonic acid gas in exhaust or " stack gas " that produced by limestone kiln.
When not wishing to be bound by theory, according to following reaction, carbon dioxide and the sodium hydroxide be present in the Bayer liquor stream of dilution react to produce sodium carbonate:
Alternatively or in addition, under suitable pH condition, carbon dioxide can react to produce sodium bicarbonate with the sodium hydroxide be present in the Bayer liquor stream of dilution.Lower than under the pH of 10.5, the formation of sodium bicarbonate becomes remarkable, thus, operates being for the operating method making sodium carbonate have precedence over sodium bicarbonate precipitation under higher than the pH of 10.5.
According to following reaction, carbonic acid gas also reacts with the sodium aluminate be present in the Bayer liquor of dilution and comprises sodium carbonate and gibbsite to produce.
Then in suitable the first solid/liquid separator (22), make the first process stream (20) stand solid/liquid separation to reclaim with the oxidation aluminum values of aluminium hydroxide (24) form, and produce the first clarifying treatment stream (26).
Aluminium hydroxide crystal seed (16) can be added as shown in Figure 2 or as shown in by the dotted line shown in Fig. 2, directly aluminium hydroxide crystal seed (16) is introduced caustic aluminate solution (14) upstream of the first reactor (18) in the first reactor.
Any suitable aluminium hydroxide crystal seed (16) may be used for the first reactor (18), such as, from the gibbsite crystal seed that is separated during the sizing of the gibbsite of pregnant Bayer process liquor precipitation during the precipitate phase measuring Bayer process.Equally, when operating under the pH in 10 to 12 scopes, boehmite crystal seed can be used.Alternatively or in addition, the aluminium hydroxide (24) reclaimed in step b) can stand screening operation with the aluminium hydroxide crystal seed source producing suitable size, as the product stream (28) of undergage being recycled to step a), and over dimensioning product stream (30), this over dimensioning product stream (30) is back to the suitable location (not shown) in alumina refinery, if or over dimensioning product stream (30) quality is enough, the product as alumina refinery is sold.If think that this over dimensioning product stream (30) quality is not enough to sell as product, can be back in bauxite charging by making over dimensioning product stream (30) to grind before digestion or to mill its quality can be improved, the oxidation aluminum values that recovery is present in over dimensioning product stream (30).
Then can mix the first clarifying treatment stream (26) and tricalcium aluminate (32) source to be formed second of calcium carbonate, the aluminate ion in solution and the hydroxide ion in solution comprising solid form to process and flow (36) in the second reactor (34).
When not wishing to be bound by theory, according to following reaction, TCA and the sodium carbonate be present in the first clarifying treatment liquid stream react to produce calcium carbonate (as solid), sodium aluminate (in solution) and sodium hydroxide (in solution):
Flow down at high temperature and lower ' S ', it is more favourable that TCA changes into calcite.As described in more detail in the examples below, along with ' S ' increases, the overall yield of ' C ' improves, but transformation efficiency reduces (as shown by C/S).
For the optimum that reaction kinetics is relevant, the second reactor (34) operates at the temperature being not less than 50 ° of C.When operating the second reactor (34) at the temperature of atmospheric boil being greater than the first process stream (36), preferably the second reactor operates under not flowing the temperature of the atmospheric boil of (26) higher than the first process being not less than 50 ° of C.Be to be understood that by direct heating second reactor or by one or two the first process stream (26) of indirect heating or TCA source (32) heating of the second reactor (34) can be carried out.As described in more detail in the examples below, in the sodium carbonate solution of 100g/L synthesis, adding useless TCA flocculating aids at the temperature within the scope of 90 ° of C to 98 ° of C and causing the TCA of 83% and 78% to be converted into calcite.
Agitation condition in first and second reactors (being respectively 18 and 34) is not critical, although the inclusion of each of the first and second reactors should be preferably and suspend completely.Depend on the relative concentration of various streams and the transformation efficiency of generation that add in correlative factor such as service temperature, separately container, the residence time in the first and second reactors (being respectively 18 and 34) can be changed.Thus residence time can be no more than in the 4 little scopes up to being no more than 20 hours.
The caustic aluminate solution (14) being supplied to the first reactor (18) can be useless Bayer liquor stream, such as, from the useless Bayer liquor stream of mud cycles of washing or the Bayer liquor of other dilutions, there is the optimum performance that ' S ' concentration is the liquid more the diluted acquisition of 20 to 100g/L.But can use stronger Bayer liquor equally, this liquid has ' S ' concentration of 100 to 350g/L.
Second process stream (36) is to remove calcium carbonate and producing the second clarifying treatment liquid stream.Use the second solid/liquid separator (38) to make the second process stream (36) stand solid/liquid separation to produce the second clarifying treatment stream (40) and the second efflux of solids (38), this second efflux of solids (38) is calcium carbonate and any unreacted TCA mainly.Can discard or wash and calcine the second efflux of solids (38) to produce the unslaked lime of recycling again.Strengthen the second clarifying treatment stream (40) with aluminate ion and hydroxide ion, it can be back to any suitable location in Bayer process, such as, and settling vessel or liquid filtering strainer.
First and second solid/liquid separator (being respectively 22 and 38) can be any suitable solid/liquid separator comprising one or more gravity settling basin, pressure filter, cyclonic separator or sedimentator, but optimum performance uses simple strainer to obtain.
Use TCA to make it possible to reclaim caustic alkali and oxidation aluminum values from mud cycles of washing by this way, otherwise due to precipitation or with soluble form and the liquid waste being attended by mud, these caustic alkali and oxidation aluminum values can be lost.Can be sent back to digest and be recycled in technique by gibbsite solid potentially, fixing (sequester) discards the CO in calcite solid effectively simultaneously
2gas, reduces the discharge of greenhouse gases.Also the waste disposal of useless TCA flocculating aids is considerably reduced.
With reference to the key element of the Bayer process schema shown in figure 1, the indicative flowchart of the example of the embodiment of Fig. 2 is described now.In adverse current mud cycles of washing (50), the alumina concentration from the washer overflow of the first mud washer (52) is very high, typically is in settling section the about half of the mother liquor overflowing settling tank (54).Use counter-current decantation, body refuse is pumped to second washer (56) etc. from the first washer (52), to the n-th washer (60), and first new water or Chi Shui (62) are introduced into (n-th) washer (60) last in mud cycles of washing (50), and be spilled over to (n-1)th washer (64) etc., until the first mud washer (52).In traditional Bayer process, in mud cycles of washing due to precipitation, and with soluble form in the liquid being attended by mud to body refuse treatment zone, have lost oxidation aluminum values.Washer spillage in all sections of mud cycles of washing, as most liquid, is oversaturated for gibbsite.Along with each washing section successively, washing spillage becomes more dilution and more ice-cold gradually, causes aluminum oxide to lose owing to being deposited on mud particle.
In one embodiment of the invention, the caustic aluminate solution (14) being supplied to the first reactor (18) is the washings overflowed from the (n-1)th washer (64).The present invention is equally applicable to process multiple washer overflow stream, and it is respectively processed in one or corresponding multiple first reactor (18) naturally.Be to be understood that the washer spillage that can similarly use from any other mud washer, but, when washer spillage take from the 2 to the (n-1)th washer (being respectively 56 and 64) any one or each time, the recovery of oxidation aluminum values is full blast, when caustic aluminate stream (14) is the overflow from first in mud cycles of washing (50) or final washer (being respectively 52 and 60), be worst.The overflow from the first washer (52) is used to be nonsensical, because be under any circumstance supplied to settling tank from the spillage of the first washer.The alumina concentration flowing to the spillage of final (n-th) washer (60) is similar to Chi Shui usually, therefore too low and do not have actual benefit.In addition, remove aluminum oxide in this stage almost not act on as far as mud cycles of washing (50) for preventing gibbsite from precipitating.
From the above description, be understood that the method for the present invention as used in this embodiment makes oxidation aluminum values can reclaim from mud cycles of washing and is delivered to precipitation circulation with the form of aluminium hydroxide.Flowing to this benefit is reduce the generation according to the autoprecipitation of equation (1) and (2) in mud cycles of washing.
The advantage of all respects of the present invention is further described and shows by following examples and experimental test results.These embodiments and experimental test results are that various possible embodiment is described, and should not be construed as and limit the present invention by any way.The person skilled in the art will easily understand the Bayer process not only having a kind of form, each alumina refinery must, according to factors, be the character of pending bauxite the most significantly, changes the specific process conditions used.Thus the restriction of the special value that do not describe by following examples of the present invention or the settling tank of type, mud washer, escharotic, solid-liquid separator.
embodiment 1:TCA is converted into calcite
Produce the TCA of synthesis in the lab, and in rotary water bath (RWB) and autoclave and at the temperature of 60 ° of C, make the sodium carbonate (Na of itself and 60g/L
2cO
3) reaction, the degree of calcite is converted into the kinetics and TCA that compare reaction.
When using RWB to test, the syringe of 20mL is used to sample with the interval of 5,10,20,30,45,60,90,120,180,240,300 minutes, 24,30,48,54 hours.By these sample filterings, cooling, then use analyzing purity, to measure ' A ', ' C ' and ' S ' concentration.After 54 hours, from RWB, remove remaining mixture and filter.Collect filtrate, XRD washs solid as before wet sample research in ice-cold DI water.
When using autoclave (AC) to test, in AC, add the 60g/LNa of 1000mL
2cO
3, then seal and balance to 60 ° of C.In AC, add the TCA of 73.09g synthesis, then reseal.So that RWB tests the identical time sampling provided above, terminate sampling 30 hours instead of 54 hours.Slurries also filter, wash and as study above by discharge AC.
Give result in figure 3, which show the test C/S comparison in time for RWB and AC two series.Result shows two serial test TCA and is substantially converted into calcite completely.
embodiment 2: matrix test
Matrix test is intended to the concentration ([Na proving temperature of reaction and sodium carbonate in the second reactor
2cO
3]) effect.The result of these tests demonstrates for given [Na
2cO
3], TCA is converted into calcite is at relatively high temperatures more favourable.Further, at a constant temperature, along with initial [Na
2cO
3] increase of (i.e. [S]), material Na
2cO
3reaction improves, but C/S realizes reducing.
Matrix test program is given in following table 1.
Table 1: matrix test condition
Each solution of 300mL cumulative volume is added in the polypropylene vial of 500mL, and is added in water-bath at each temperature.Once these bottles balance, add TCA with each amount.Carry out sampling under each time and analyze ' A ', ' C ' and ' S ' concentration.
dynamic test:
Design motivation test is being shown under the intermediate point condition provided in [1] with assessment, and TCA is converted into the speed of calcite.Thus, the Na of 40g/L is used
2cO
3test with 60 ° of C.Sampled at 5,15,30,45,60,90,120,180 and 240 minutes and analyze ' A ', ' C ' and ' S ' concentration.In each test, TCA is added (80% of final ' C ' concentration) in the carbonate of the consumption of 80%.The result of dynamic test is shown in following table 2.Can find out and achieve about 50% of ' C ' always change in 5 minutes in the beginning of 4 h run.This shows that speed of reaction is quickly.Expect that this speed increases with higher temperature and higher initial ' S '.
Table 2: dynamic test result
material:
The TCA slurry of 12L is collected from alumina refinery.To filter and with hot wash TCA slurry.Solid wet is stored in sealable bag.Get wet sub-sample and carry out X-ray diffraction (XRD).Another one's share of expenses for a joint undertaking sample dry and carry out x-ray fluorescence analysis (XRF).By preparing sodium carbonate solution by the volumetric flask of known Standard entertion 1L.Analytical standard is to measure ' C ' and ' S ' concentration.
In Fig. 4 to 8, illustrate the result of matrix test program, these figures show that final ' C ' under constant ' S ' of three temperature.It is more favourable that result shows that at high temperature TCA is converted into calcite, and the overall yield of ' C ' increases along with the increase of ' S ', but efficiency reduces (as shown by C/S).
In matrix test program, be successfully made the conversion of TCA to calcite, result shows that higher temperature and lower ' S ' are conducive to the generation of conversion reaction.Conversion yield display is higher with higher initial ' S ', but the efficiency as measured by C/S reduces along with higher initial ' S '.The dynamic test display conversion rate of carrying out in the sodium carbonate solution of 40g/L and under 60 ° of C is fast, reaches final ' C ' of about 50% in 5 minutes.
embodiment 3: mixing effect
At [the NaL of 60 ° of C and 40g/L
2cO
3] under repeat the test method that provides in embodiment 2 and stir (if there is) to the impact of reaction kinetics to measure.Determine the test using vigorous agitation autoclave to carry out and be no faster than the equivalent test using rotary water bath.
Owing to describe in detail some embodiments of the present invention, therefore the technician of field of chemical engineering can make a lot of modification and change by understanding when not deviating from basic inventive concept.Think all these change and modification within the scope of the invention, essence of the present invention is determined by description above and the claim of enclosing.
To be expressly understood, although refer to many prior art publications in this article, this quote do not form admit in these documents arbitrary section formed this area, Australia or any other national in the part of general knowledge.In the explanation of invention with subsequently in description of the invention, except the implication due to representation language or necessity, outside linguistic context needs in addition, word " comprises " or such as " comprises " or the modification of " containing " uses with inclusive meaning, namely specifies there is described characteristic in various embodiment of the present invention instead of get rid of this existence or add further feature.
Claims (24)
1., for reclaiming a method for aluminum oxide from caustic aluminate solution, said method comprising the steps of:
A) under aluminium hydroxide crystal seed exists, in caustic aluminate solution, carbon dioxide source is introduced to form the first process stream of the aluminium hydroxide of carbanion and the solid form comprised in solution;
B) make step described first process a) flow through by solid/liquid separation to reclaim the aluminum oxide of aluminium hydroxide form, and produce the first clarifying treatment stream; And
C) by step b) described first clarifying treatment stream and tricalcium aluminate mix to be formed second of calcium carbonate, the aluminate ion in solution and the hydroxide ion in solution comprising solid form and process and flow.
2. the method for reclaiming aluminum oxide according to claim 1, wherein, step c) be carry out being not less than at the temperature of 50 DEG C.
3. the method for reclaiming aluminum oxide according to claim 1, wherein, step c) be not less than 50 DEG C and carrying out at the temperature of the atmospheric boil do not flowed higher than described first process.
4. the method for reclaiming aluminum oxide according to claim 1, wherein, heating steps b) described first clarifying treatment stream so as at 50 DEG C and do not carry out step c higher than at the temperature in the scope of atmospheric boil).
5. according to the method for reclaiming aluminum oxide in any one of the preceding claims wherein, wherein, described caustic aluminate solution is Bayer liquor.
6. the method for reclaiming aluminum oxide according to claim 5, wherein, described Bayer liquor be selected from useless Bayer liquor, the overflow stream of mud washing section and pond current one or more.
7. the method for reclaiming aluminum oxide according to claim 1, wherein, makes step b) in reclaim aluminium hydroxide stand screening with produce be recycled to step aluminium hydroxide crystal seed source a).
8. the method for reclaiming aluminum oxide according to claim 1, wherein, step described aluminium hydroxide crystal seed a) is three aluminium hydroxide crystal seeds.
9. the method for reclaiming aluminum oxide according to claim 1, wherein, step described aluminium hydroxide crystal seed a) is boehmite or gibbsite crystal seed.
10. the method for reclaiming aluminum oxide according to claim 1, comprises further and makes step c) described second process flow through by solid/liquid separation with removes calcium carbonate and generation the second clarifying treatment stream steps d).
11. methods for reclaiming aluminum oxide according to claim 10, comprise treatment step d further) in remove calcium carbonate to produce the step of lime.
12. methods for reclaiming aluminum oxide according to claim 1, the position being included in digestive organ downstream and settling vessel upstream further makes described second clarifying treatment stream be back to the step of alumina refinery.
13. methods for reclaiming aluminum oxide according to claim 1, wherein, described caustic aluminate solution has the alkali concn being expressed as the g/L concentration of equivalent sodium carbonate of 20 to 350g/L.
14. methods for reclaiming aluminum oxide according to claim 1, wherein, described caustic aluminate solution has the alkali concn being expressed as the g/L concentration of equivalent sodium carbonate of 20 to 100g/L.
15. methods for reclaiming aluminum oxide according to claim 1, wherein, for step c) described tricalcium aluminate be TCA flocculating aids or useless TCA flocculating aids.
16. methods for reclaiming aluminum oxide according to claim 6, wherein, make step b) in reclaim aluminium hydroxide stand screening with produce be recycled to step aluminium hydroxide crystal seed source a).
17. methods for reclaiming aluminum oxide according to claim 6, wherein, step described aluminium hydroxide crystal seed a) is three aluminium hydroxide crystal seeds.
18. methods for reclaiming aluminum oxide according to claim 6, wherein, step described aluminium hydroxide crystal seed a) is boehmite or gibbsite crystal seed.
19. methods for reclaiming aluminum oxide according to claim 6, comprise further and make step c) described second process flow through by solid/liquid separation with removes calcium carbonate and generation the second clarifying treatment stream steps d).
20. methods for reclaiming aluminum oxide according to claim 19, comprise treatment step d further) in remove calcium carbonate to produce the step of lime.
21. methods for reclaiming aluminum oxide according to claim 6, the position being included in digestive organ downstream and settling vessel upstream further makes described second clarifying treatment stream be back to the step of alumina refinery.
22. methods for reclaiming aluminum oxide according to claim 6, wherein, described caustic aluminate solution has the alkali concn being expressed as the g/L concentration of equivalent sodium carbonate of 20 to 350g/L.
23. methods for reclaiming aluminum oxide according to claim 6, wherein, described caustic aluminate solution has the alkali concn being expressed as the g/L concentration of equivalent sodium carbonate of 20 to 100g/L.
24. methods for reclaiming aluminum oxide according to claim 6, wherein, for step c) described tricalcium aluminate be TCA flocculating aids or useless TCA flocculating aids.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2010901879 | 2010-05-03 | ||
| AU2010901879A AU2010901879A0 (en) | 2010-05-03 | Process for Recovery of Alumina | |
| PCT/AU2011/000505 WO2011137481A1 (en) | 2010-05-03 | 2011-05-02 | Process for recovery of alumina using tricalcium aluminate |
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| CN (1) | CN103038174B (en) |
| AU (1) | AU2011250647B2 (en) |
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| GB648248A (en) * | 1941-06-14 | 1951-01-03 | Jean Charles Seailles | Method for making a water solution of raw aluminates of lime and its application to the manufacture of alumina |
| CN1273943A (en) * | 2000-06-28 | 2000-11-22 | 王立卓 | Process for preparing soium aluminate solution with calcium aluminate clinker |
| CN1473762A (en) * | 2003-08-06 | 2004-02-11 | 姜树宽 | Process for producing aluminium hydroxide using biological fermenting waste gas CO2 |
| CN1562756A (en) * | 2004-03-19 | 2005-01-12 | 邝中 | Technique for extracting alumina from materiel containing calcium aluminate |
| CN101186324A (en) * | 2007-12-17 | 2008-05-28 | 中国铝业股份有限公司 | Deep decomposition method for sodium aluminate solution |
| CN101450843A (en) * | 2008-12-22 | 2009-06-10 | 广西投资集团有限公司 | Iron and aluminum complex ore comprehensive utilization method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SK287753B6 (en) * | 1998-09-25 | 2011-08-04 | Worsley Alumina Pty Ltd | Process for the caustification of Bayer liquors |
| GB0018592D0 (en) * | 2000-07-29 | 2000-09-13 | Univ Leeds | Production of oxides of iron aluminium and titanium from bauxite and red mud |
| CN101182022B (en) * | 2007-12-11 | 2010-11-10 | 中国铝业股份有限公司 | Preparation method of powder aluminum hydroxide |
-
2011
- 2011-05-02 AU AU2011250647A patent/AU2011250647B2/en not_active Ceased
- 2011-05-02 BR BR112012027265A patent/BR112012027265A2/en not_active Application Discontinuation
- 2011-05-02 WO PCT/AU2011/000505 patent/WO2011137481A1/en active Application Filing
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| GB648248A (en) * | 1941-06-14 | 1951-01-03 | Jean Charles Seailles | Method for making a water solution of raw aluminates of lime and its application to the manufacture of alumina |
| CN1273943A (en) * | 2000-06-28 | 2000-11-22 | 王立卓 | Process for preparing soium aluminate solution with calcium aluminate clinker |
| CN1473762A (en) * | 2003-08-06 | 2004-02-11 | 姜树宽 | Process for producing aluminium hydroxide using biological fermenting waste gas CO2 |
| CN1562756A (en) * | 2004-03-19 | 2005-01-12 | 邝中 | Technique for extracting alumina from materiel containing calcium aluminate |
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| AU2011250647B2 (en) | 2013-11-07 |
| CN103038174A (en) | 2013-04-10 |
| WO2011137481A1 (en) | 2011-11-10 |
| BR112012027265A2 (en) | 2017-03-14 |
| AU2011250647A1 (en) | 2012-11-08 |
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