CA1265318A - Process of producing aluminum fluoride - Google Patents
Process of producing aluminum fluorideInfo
- Publication number
- CA1265318A CA1265318A CA000474437A CA474437A CA1265318A CA 1265318 A CA1265318 A CA 1265318A CA 000474437 A CA000474437 A CA 000474437A CA 474437 A CA474437 A CA 474437A CA 1265318 A CA1265318 A CA 1265318A
- Authority
- CA
- Canada
- Prior art keywords
- solids
- fluidized bed
- gas
- aluminum hydroxide
- bed system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- 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
- C01F7/48—Halides, with or without other cations besides aluminium
- C01F7/50—Fluorides
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- Glass Compositions (AREA)
- Catalysts (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
- Electrolytic Production Of Metals (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
- Treating Waste Gases (AREA)
- Removal Of Specific Substances (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Producing aluminum fluoride from aluminum hydroxide or alumina hydrate and hydrogen fluoride yields a highly concentrated product and an exhaust gas having a low hydrogen fluoride content when an initial isoling step is introduced. In the process, partly reacted aluminum hydroxide circulated in a cooling cycle is added to fresh aluminum hydroxide or alumina hydrate in a first stage, in which the aluminum hydroxide is contacted with the hydrogen floride-containing exhaust gases from the circulating fluidized bed system so as to form a gas-solids suspension at a temperature of 150 to 250°C. Thereafter, the solids are collected from the gas steam at least part of the collected solids are passed through a cooler, and cooled solids are re-contacted with fresh aluminum hydroxide or alumina hydrate. a partial stream of the collected solids is supplied to the circulating fluidized bed system and is reacted therein at a temperature of at least 450°C, preferably of 500 to 600°C, with hydrogen fluoride supplied in the form of a gas in a concentration up to 25 vol. % .
Producing aluminum fluoride from aluminum hydroxide or alumina hydrate and hydrogen fluoride yields a highly concentrated product and an exhaust gas having a low hydrogen fluoride content when an initial isoling step is introduced. In the process, partly reacted aluminum hydroxide circulated in a cooling cycle is added to fresh aluminum hydroxide or alumina hydrate in a first stage, in which the aluminum hydroxide is contacted with the hydrogen floride-containing exhaust gases from the circulating fluidized bed system so as to form a gas-solids suspension at a temperature of 150 to 250°C. Thereafter, the solids are collected from the gas steam at least part of the collected solids are passed through a cooler, and cooled solids are re-contacted with fresh aluminum hydroxide or alumina hydrate. a partial stream of the collected solids is supplied to the circulating fluidized bed system and is reacted therein at a temperature of at least 450°C, preferably of 500 to 600°C, with hydrogen fluoride supplied in the form of a gas in a concentration up to 25 vol. % .
Description
, .
~Z6~i3~
February 13, 1984 :
Process of Producing Aluminum Fluoride This invention relates to a process of producing aluminum fluoride from aluminum hydroxide and hydrogen fluoride in a circulating fluidized bed system including a 1uidized bed reactor, a cyclone ~eparator and a recycling line.
It 19 ~nown to produce aluminum fluoride from fluoride-containing materials by a reaction with mlneral acids and a subsequent crystallization (German Patent Pu~lication 10 62 681), or by a two-stage~reactlon of 1uorine compounds ~ith alumlnum chloride (Austrian Patent Specificatlon 130,199; German Patent S~ecification 837,690; U.S. Patent 1,831l430), or ~y a reaction of aluminum hydroxide with a~ueou3 hydrogen fluoride (German Patent Specifi~catlon 12 20 ~39; Laid-o~en German Appli-cations 15~ 92;~;09~9~ 15 92 100;;~15 92 1357 and~U.S Patent 3,432,086~ or by~a~decompos;ition;of aluminum alcoholates;~
wl~h~acid~(Ge~rran Patent Publi~tAon~12~94 35B~
~2~53~ ~3
~Z6~i3~
February 13, 1984 :
Process of Producing Aluminum Fluoride This invention relates to a process of producing aluminum fluoride from aluminum hydroxide and hydrogen fluoride in a circulating fluidized bed system including a 1uidized bed reactor, a cyclone ~eparator and a recycling line.
It 19 ~nown to produce aluminum fluoride from fluoride-containing materials by a reaction with mlneral acids and a subsequent crystallization (German Patent Pu~lication 10 62 681), or by a two-stage~reactlon of 1uorine compounds ~ith alumlnum chloride (Austrian Patent Specificatlon 130,199; German Patent S~ecification 837,690; U.S. Patent 1,831l430), or ~y a reaction of aluminum hydroxide with a~ueou3 hydrogen fluoride (German Patent Specifi~catlon 12 20 ~39; Laid-o~en German Appli-cations 15~ 92;~;09~9~ 15 92 100;;~15 92 1357 and~U.S Patent 3,432,086~ or by~a~decompos;ition;of aluminum alcoholates;~
wl~h~acid~(Ge~rran Patent Publi~tAon~12~94 35B~
~2~53~ ~3
- 2 -Furth~rmore proc~sses using aluminum hydroxide and hydrogen fluoride are particularly significant. The reaction can be carried out in an aqueous phase and may be succeeded by a crystallizing step and, if desired, by a dewatering step (German Patent Specification 492,412)~ Alternatively~
the reaction can be carried out at elevated temperatures so that a dry aluminum fluoride product is obtained (British Patent Specification 328,688). Such processes are mainly carried out in a fluidized bed, in which alumina or aluminum hydroxide is reacted with hydrogen fluoride at elevated temperatures (Germ~n Patent Specifications 815,343j 10 92 889;
British Patent Speciflcation 656,3747 French Patent Speci-fications 1~011~5447 1~221~2997 1,517,952J U.S. Patent
the reaction can be carried out at elevated temperatures so that a dry aluminum fluoride product is obtained (British Patent Specification 328,688). Such processes are mainly carried out in a fluidized bed, in which alumina or aluminum hydroxide is reacted with hydrogen fluoride at elevated temperatures (Germ~n Patent Specifications 815,343j 10 92 889;
British Patent Speciflcation 656,3747 French Patent Speci-fications 1~011~5447 1~221~2997 1,517,952J U.S. Patent
3~057,6aO). A multi-stage process of producing aluminum fluoride from alumlna trihydrate and partly dehydrated alumina trihydrate by a treatment wlth a gas that contains hydrogen fluoride is described in Lald-open German Appli-cation 1~908~585; Laid-open French A~plication 2,002,335 and Canadian Patent Speclfication 537,403.
Those of the processes described hereinbeore which comprise a crystallization and drying of the aluminum fluoride are necessarily carried out ln a plurality of stages so that they require expensive equipment, They also involve considerable sewage~prob1ems or requlre a;circulation o`f large guantities of solvent. In all fluidized bed processe~, hydrogen fluoride~gas is required in a relatively high concentratlon.
~653~L~
In another process of producing aluminum fluoride, a circulating fluidized bed i~ employed, to which liquld hydrogen fluoride ~s directly supplied above the grate but below the inlet for the recycled solids (German Patent Specification 21 06 306). r~hereas that process affords the advantage that the hydrofluoric acid is heated virtually instantaneously through the temperature range of 60 to 250 C, which is critical as regards corrosion, the process depends on the availability of liquid hydrogen fluoride.
Processes of producing aluminum fluoride wlth the ald of gases whicn contain hydrogen fluoride in a relatively low concentration have recently become more significant.
Such gases may become available in processes involving the pyroh~dxolysis o solid residues ln the alumlnum industry, e.g.,o~ spentpot lining and in de~endence on the processlng conditions with respect to concentrating treat~ent and the subsequent evaporation contain hydrofluoride ln a concentration of only 8 to 12 vol. % or 20 to 25: VDl./~, Said gases have a very high water vapor content up to 70 vol.~. These condltions give rise to the following problems in the production o~
aluminum fluoride:
An increasing reaction temperature in the aluminum fluoride reactor and an ~llcreasing water vapor content ln the gas will~result in an increase of the equilibrlum hydrogen fluorlde partial pressure in the exhaust gas.
~26S3~
rate (yield) This means that the convers~on/of hydroge~ fluoride decreases drastically as the temperature and water vapor content of the exhaust gas increase. A decrease o the reaction temperature in view of the still existing o~ject to produce aluminum fluoride in the highest possible concentration of, e.g., at least 90 wt.% AlF3 does not g~ve the desired result because the reaction rate (kin~tics) of the rocess is drasticall~ decreased thereby although the rate e~uilibrium conditions for a high conversion /of hydrogen fluoride are improved~ The greatly decreasing reaction rate cannot be compensated ~n practice by a longer residence time of the solids in the reactor because sucb pxactlce would re~uire a reactor having excesslvely large dimensions.
It is an object of the invention to provide or the production of alu~inum fluoride a process in which gases containin~g hydrogen fluoride in a low concentratlon can be employed and which can be carrled out in a reactor having i~ensions that æereasonable from a structural aspect and rate(yield) which permits a maximum conversion/of hydrogen fluoride in conjunction with the recovery of a highly concentrated product, This object is accomplished in that the process of the kind described first hereinbefore is carried~out ln~accordance~wlth~;the~lnventlon ln such~a manner~that partly~reacted aluminum hydroxide~circulated in~a cooling aycle~ls added to~fresh~a1um1num hydroxlde~or alum1na~
hydrate in a first ., :
~2~6S3~3 or alu~ina hydrate stag~, in which the alum~num hydroxide/is contacted with the hydrogen fluoride-containing exhaust gases from the circulating fluldized bed system so as to form a gas~solids suspension at a temperature of 150 to 250 C, whereafter the solids are collected from the gas stream, a~ least part of the collected solids are passed through a cooler, cooled solids are re-contacted with fresh aluminum or alumina hydrate hydroxide~ and a partial stream of the collected solids is supplied to the circulating fluidized bed ~ystem and ts reacted therein at a temperature of at least 450 C
with hydrogen fluorlde supplied in the form of a gas in a concentration up to 25 vol~%.
In the productlon o alumlnum ~luoride it l~ known that alumina before its react,ion with hydrofluoric acid having a concentration of 70 to 80 % can be partly reacted in the exhaust gas plpe of a calcining furnace wlth the hot exhaust gases from said furnace, which co~tain hydrogen :
fluoride, and that the exhaust gas pipe can be so dimensioned that an intlmate contact between the exhaust gas and the alumina is achieved (German Patent Publication 19 56 943).
But in that prior art it is not contemplated to admix partly reacted alumLna which is c~rculated in a coollng cycle, Such admixing 1s~not:required in the known process bècause owing to the high concentra~ion of the :hydrofluoric~acid which is:employed::the ratio of the' exhaust gas~and alumina rates~is~much more~favorablè ;
a~ xegards~the he:at:balanceO: ~
., . : ; . .. ~ ~ ~
- 6 - ~
or alumina hydrat Filter-m~ist or predried alumlnum hydroxide/may be used as starting solids in the process in accordance w~th the invention.
~ he proportion in which aluminum hydroxide circulated in a cooling cycle is added will mainly depend on the temperature of the cooled hydroxide and on the creating temperature of the gas / the gas-solids suspension. It is essential to obtain a suspension at a temperature of 150 to 250 C so that the converslon of hydrogen fluoride in the ~irst stage of the process will be con~iderably increa~ed.
In accordance with a preferred feature of the invention all solids collected from the gas-solids suspension are passed through the cooler. This will ensure that solids at an adequate rate will alway~ be available for cooling the exhaust gas to the desired temperature.
In accordance with another preferr~d feature of the invention the hydrogen fluoride supplied in the form of a gas i5 reacted in the circulating fludized bed at a temperature in the range o~ 500 to 600 C. The operation ln~
that temperature range will result in a sufficiently hlgh the temper2ture of reactlon rate and in an exhaust ga~/which~can be adjusted~
without a need for a cooling cycle involving an exces~ively high coollng expenditure, .
:~ :
:
i53~
In an advantageous embodlment of the invention, that part of the solids whlch is to be supplied to the circulating fluidized bed system ~s iDtroduced via the exhaust gas stream of the circulating fluldi~ed bed system and an interposed separator. As a result, the exhaust gas stream is considerably cooled and an additional reaction path is provided.
In a variant of the process in accordance with the invention the exhaust gas stream leaving the recycling cyclone of the circulating ~luidized bed Ls cooled not only with alumlnum hydroxide but i8 also cooled by a supply of cold gas~ such as alr at amblent temperature.
As a result, the rate at whlch aluminum hydroxide is circulated in the cooling cycle can be decreased.In particular additional influence, which is independent of the process streams, can be exerted on the gas temperature before the gas is contacted with the fresh starting solids.
The aluminum hydroxlde that has been collected fro~ thei gas-solids suspension can be cooled by any suitahle equipment. Particularly desirable equipment consists of a fluidi~ed bed cooler, which may include a plurality of cham~ers to be flown through by the aluminum ~
bydroxide in succession, and interconnected cooling~surfaces, which immierse~into respective chambers and are cooled by flowing water.
~, . : , , , : :
~ ~65?3 ~L8?~
The circulatlng fluidized bed system has the usual desiyn and mode of operation. The fluidlzed bed reactor may be circular or square or rectangular in cross-section and may contain a grate or a venturi device for the supply of tne fluidi7ing gas~ The reactor area and the gas rate are so selected that the mean density of the suspension in the fluidized bed reactor is in a range of approximately 50 to 400 kg/m of reactor volume. Whereas an orthodox fluidi~d bed is characterized by a distlnct density step between the fluidized bed and the overlying gas space, the entire fluidized bed reactor of a circulating fluidized bed system is occupied by a gas-solids suspension and the density of the ~uspension in said reactor decreases from bottom to top. ~The mode of operation of clrculatlng fluidized bed systems is described by L. Reh et al. in "'Xirbelschichtprozesse f~r die Chemie- und H~tten-Industrie, die Energieumwandlung un~ den Umweltschutz'i, Chem. Ing.
Techn.~ 55 (1983), No. 2, pages 87 to 93).
The lnvention will be explained more in detail by way~of example wlth reference to the drawing and the Examples.
The drawlng is a flow scheme illustrating the proceas in accordance with the invention.
A clrculati~ng fluidlzed bed system comprising a fluidized bed reactor 1,~a recycling cyclone 2 and a reoycling line~3 }s~supplied through line 4 wlth~a . ~ ~
"
~a2~i;53~3 g hydrogen fluoride-containing gas, which may have been brought to the required temperature by indirect heating or by an admixing of combustiorl gas~ The exhaust gas f the circulating fluidized bed system is discharged via the passed recycling cyclone 2 ~nd/through the venturi suspenslon heat exchanger 5, in which solids supplied from the fluidized be.d cooler 6 through line 7 are added to the gas.
The resulting gas-solids suspension is supplied through line 8 to the cyclone separator 9, in which solids are collected. Said solids are supplied through line 10 to the circulating flutdized bed system 1, 2, 3.
In the variant inv.olving an addltional cooling of the gas leaving the recycling cyclone 2, a cold ga9, such as air at ambient temperature, is supplied through line 24.
: In another venturi suspension heat exchanger 11, or alumina hydrate fresh aluminum hydroxide/supplièd through li~e 22 and addltional solids supplled from the fluldlzed bed cooler 6 : through line 12 and serving also to adjust the temperature are admlxed to the exhaust gas from the cyclone separator 9 so that another gas-solids suspension is formed. That suspension is supplied through line 13 to the cyclone separator 14, ln which solids are collected and are supplled through line 15 to the fluidized bed cooler 60 The exhaust gas~is flnally purlfied ina fine~dust collector 16~(cloth filter or~eleotrostatlc preolpltator)~and ~s then supplied to~a~wet or dry scrubber:for a~removal of residual hydrogen :
fluoride (not.~shown).
' ~26~3~ !3 The fluidized bed cooler 6 contain~ two cooling chambers 17 and 18, into wh$ch interconnected coollng surfaces 19 extend. The fluidizing gases are supplled through llne 20. By means of a star feeder 21, the solids leaving the fluidized bed cooler are distributed between lines 7 and 12.
The final product ls withdrawn from ~e circulating fluidlzed bed syst~m through line 23.
Exam?le 1 The fluidized bed reactor 1 of the circulating fluidized bed system is supplied through line 4 with gas at a rate o~ 6906 m.N /h and at a temperature ~f 570 C7 that gas contains 10.1 vol.% HF. The temperature ln the circulating fluidized bed is 530C. The mean density of the suspension is about 150 kg/m reactor volume~ The quanity of solids circulated per hour through the fluidized bed reactor:1, the recycling cyclone 2 and the re~ycling line 3 is about 50 times~the quantity of solids contained in the fluidized bed reactor 1.
~ he exhaust gas which has left the circula~ing fluidized bed system is at a temperature of 530 C a~d contains 7.5~vol.% HF as it enters~khe venturi suspenslon heat exchanger~5.~In that heat:exchanger, solids at tO0 C, ; ;
;:wh;Lch have been:supplled~from ~he fluidLze~ bed reactor 6 th:rough l~ne 7~at~a:rate of 1797 kg/h~, are added to~the :
~21653~
exhaust gas, which ~ thus cooled to 453 C. The solids collected in the cyclone separator 9 are supplled through line 10 to the fluidized bed reactor l of the circulating fluidized bed system.
The exhaust gas from the cyc:lone separator 9 or alumina hydrate contains 4.0 vol.% HF. Fresh alumlnum hydroxlde/having a moisture content of 12.0~ is supplied through line 22 at a rate of 1030 kgJh. Solids at 100C are entrained at a rate of 16,500 kg~h in lin`e 12 by the fluidizing air from the fluidized bed cooler 6. In the venturi suspension heat exGhanger 11, said fxesh aluminum hydroxlde and said solid are added to the exhaust gas from the cyclone separator 9 so tnat said exhaust gas i9 cooled to 220 C. After ~eing passed through the ayclone separator 14 and the ine exhaust gas dust collector 16 the/is supplied to a dry scrubber.
The exhaust gas becomes avallable at a rate of 8100 mN3th and contains 0.15 vol. ~ HF.
The solids which have been collected in 14 and 16 become available at a temperature of 220 C and are cooled to 100C in the fluidi~ed bed cooler 6 and are su~sequently distributed between line 7 and 12 as descrlbed hereinbefore, in a ratio of 1:9.2.
, Aluminum fluoride 2roduct at a rate of 937 kg/h ~
is withdrawn from~:the fluidlzed bed reactor 1 through line ::
23. That product has:a pu~lty of:91% (balance Al203 and igniti:on:loss).
,. ~., .
~26~i3~
In thls Example, an additional cooling with air is effected in the process in accordance with the invention.
The conditions regarding the supply of gas and the operation of the circulating fluidizad bed system are the same as in Examole 1.
As in Example 1, the exhaust gas $rom the circulating fluLdized bed system is at a temperature o~ ~30C as it enters the venturi suspension heat exchanger 5, in which solids at 100C, which have been supplied at a rat~ of 1786 kg/h from tne fluidized ~ed cooler 6 through line 7, are added to the exhaust gaq as well as air at 40C~ whioh is supplied at a rate of 1052 ~ 3/h through line 24. The gas is thu3 cooled to 420 C. Sollds colleotad in the cyclone separator 9 are supplied throu~h line 10 to the fluidized :~ed reactor 1 of the circulating fluidized ~ed syqt2m.
The axhaust gas from the cyclone ssparator 9 ,or alumina hydrate contalns 2.0 vol.% ~F. Fresh aluminum hydroxide'having a moisture content of~12.0~ is su~plled through line 22 at a rate of 1D30 kg/ll. Solids at 100 C are entrained at a rate of 15,900 kg/h in line 12 by the~fluidizing air from the fluid1zed bed cooler 6. In the venturi suspension~heat excnanger 11,~said fresh aluminum hydroxide and said ~olids are~added to~the ex~aust gas from the~cycione~separator~9 ~
o ~ so that sai~d~e~laust gas is;~cooled~to~220 C.~After~ belng ~
~ .~. , ~ : ,: : :
~2~i53~8 pa~sed through the cyclone separator 14 and the finedust collector 16 the exhaust gas is supplied to a dry serubber. The exhaust gas becomes available 3 and at a rate of 5150 mN /h;/contains 0.13 vol. % HF.
The solids which have been collected in 14 and 16 become arailable at a temperature of 220 C and are cooled to 100 C in the fluidized bed cooler 6 and are subsequently distributed between l1nes 7 and 12 as described hereinbefore, at a ratio of 1:8.9.
Aluminum fluoride product at a rate of 937 kg/h is withdrawn from the fluidized bed reactor 1 through line 23. That product has a purity of 91 % (balance Al203 and ignition loss), .
, .
.: :
~,:
:~ :
: ~ :
Those of the processes described hereinbeore which comprise a crystallization and drying of the aluminum fluoride are necessarily carried out ln a plurality of stages so that they require expensive equipment, They also involve considerable sewage~prob1ems or requlre a;circulation o`f large guantities of solvent. In all fluidized bed processe~, hydrogen fluoride~gas is required in a relatively high concentratlon.
~653~L~
In another process of producing aluminum fluoride, a circulating fluidized bed i~ employed, to which liquld hydrogen fluoride ~s directly supplied above the grate but below the inlet for the recycled solids (German Patent Specification 21 06 306). r~hereas that process affords the advantage that the hydrofluoric acid is heated virtually instantaneously through the temperature range of 60 to 250 C, which is critical as regards corrosion, the process depends on the availability of liquid hydrogen fluoride.
Processes of producing aluminum fluoride wlth the ald of gases whicn contain hydrogen fluoride in a relatively low concentration have recently become more significant.
Such gases may become available in processes involving the pyroh~dxolysis o solid residues ln the alumlnum industry, e.g.,o~ spentpot lining and in de~endence on the processlng conditions with respect to concentrating treat~ent and the subsequent evaporation contain hydrofluoride ln a concentration of only 8 to 12 vol. % or 20 to 25: VDl./~, Said gases have a very high water vapor content up to 70 vol.~. These condltions give rise to the following problems in the production o~
aluminum fluoride:
An increasing reaction temperature in the aluminum fluoride reactor and an ~llcreasing water vapor content ln the gas will~result in an increase of the equilibrlum hydrogen fluorlde partial pressure in the exhaust gas.
~26S3~
rate (yield) This means that the convers~on/of hydroge~ fluoride decreases drastically as the temperature and water vapor content of the exhaust gas increase. A decrease o the reaction temperature in view of the still existing o~ject to produce aluminum fluoride in the highest possible concentration of, e.g., at least 90 wt.% AlF3 does not g~ve the desired result because the reaction rate (kin~tics) of the rocess is drasticall~ decreased thereby although the rate e~uilibrium conditions for a high conversion /of hydrogen fluoride are improved~ The greatly decreasing reaction rate cannot be compensated ~n practice by a longer residence time of the solids in the reactor because sucb pxactlce would re~uire a reactor having excesslvely large dimensions.
It is an object of the invention to provide or the production of alu~inum fluoride a process in which gases containin~g hydrogen fluoride in a low concentratlon can be employed and which can be carrled out in a reactor having i~ensions that æereasonable from a structural aspect and rate(yield) which permits a maximum conversion/of hydrogen fluoride in conjunction with the recovery of a highly concentrated product, This object is accomplished in that the process of the kind described first hereinbefore is carried~out ln~accordance~wlth~;the~lnventlon ln such~a manner~that partly~reacted aluminum hydroxide~circulated in~a cooling aycle~ls added to~fresh~a1um1num hydroxlde~or alum1na~
hydrate in a first ., :
~2~6S3~3 or alu~ina hydrate stag~, in which the alum~num hydroxide/is contacted with the hydrogen fluoride-containing exhaust gases from the circulating fluldized bed system so as to form a gas~solids suspension at a temperature of 150 to 250 C, whereafter the solids are collected from the gas stream, a~ least part of the collected solids are passed through a cooler, cooled solids are re-contacted with fresh aluminum or alumina hydrate hydroxide~ and a partial stream of the collected solids is supplied to the circulating fluidized bed ~ystem and ts reacted therein at a temperature of at least 450 C
with hydrogen fluorlde supplied in the form of a gas in a concentration up to 25 vol~%.
In the productlon o alumlnum ~luoride it l~ known that alumina before its react,ion with hydrofluoric acid having a concentration of 70 to 80 % can be partly reacted in the exhaust gas plpe of a calcining furnace wlth the hot exhaust gases from said furnace, which co~tain hydrogen :
fluoride, and that the exhaust gas pipe can be so dimensioned that an intlmate contact between the exhaust gas and the alumina is achieved (German Patent Publication 19 56 943).
But in that prior art it is not contemplated to admix partly reacted alumLna which is c~rculated in a coollng cycle, Such admixing 1s~not:required in the known process bècause owing to the high concentra~ion of the :hydrofluoric~acid which is:employed::the ratio of the' exhaust gas~and alumina rates~is~much more~favorablè ;
a~ xegards~the he:at:balanceO: ~
., . : ; . .. ~ ~ ~
- 6 - ~
or alumina hydrat Filter-m~ist or predried alumlnum hydroxide/may be used as starting solids in the process in accordance w~th the invention.
~ he proportion in which aluminum hydroxide circulated in a cooling cycle is added will mainly depend on the temperature of the cooled hydroxide and on the creating temperature of the gas / the gas-solids suspension. It is essential to obtain a suspension at a temperature of 150 to 250 C so that the converslon of hydrogen fluoride in the ~irst stage of the process will be con~iderably increa~ed.
In accordance with a preferred feature of the invention all solids collected from the gas-solids suspension are passed through the cooler. This will ensure that solids at an adequate rate will alway~ be available for cooling the exhaust gas to the desired temperature.
In accordance with another preferr~d feature of the invention the hydrogen fluoride supplied in the form of a gas i5 reacted in the circulating fludized bed at a temperature in the range o~ 500 to 600 C. The operation ln~
that temperature range will result in a sufficiently hlgh the temper2ture of reactlon rate and in an exhaust ga~/which~can be adjusted~
without a need for a cooling cycle involving an exces~ively high coollng expenditure, .
:~ :
:
i53~
In an advantageous embodlment of the invention, that part of the solids whlch is to be supplied to the circulating fluidized bed system ~s iDtroduced via the exhaust gas stream of the circulating fluldi~ed bed system and an interposed separator. As a result, the exhaust gas stream is considerably cooled and an additional reaction path is provided.
In a variant of the process in accordance with the invention the exhaust gas stream leaving the recycling cyclone of the circulating ~luidized bed Ls cooled not only with alumlnum hydroxide but i8 also cooled by a supply of cold gas~ such as alr at amblent temperature.
As a result, the rate at whlch aluminum hydroxide is circulated in the cooling cycle can be decreased.In particular additional influence, which is independent of the process streams, can be exerted on the gas temperature before the gas is contacted with the fresh starting solids.
The aluminum hydroxlde that has been collected fro~ thei gas-solids suspension can be cooled by any suitahle equipment. Particularly desirable equipment consists of a fluidi~ed bed cooler, which may include a plurality of cham~ers to be flown through by the aluminum ~
bydroxide in succession, and interconnected cooling~surfaces, which immierse~into respective chambers and are cooled by flowing water.
~, . : , , , : :
~ ~65?3 ~L8?~
The circulatlng fluidized bed system has the usual desiyn and mode of operation. The fluidlzed bed reactor may be circular or square or rectangular in cross-section and may contain a grate or a venturi device for the supply of tne fluidi7ing gas~ The reactor area and the gas rate are so selected that the mean density of the suspension in the fluidized bed reactor is in a range of approximately 50 to 400 kg/m of reactor volume. Whereas an orthodox fluidi~d bed is characterized by a distlnct density step between the fluidized bed and the overlying gas space, the entire fluidized bed reactor of a circulating fluidized bed system is occupied by a gas-solids suspension and the density of the ~uspension in said reactor decreases from bottom to top. ~The mode of operation of clrculatlng fluidized bed systems is described by L. Reh et al. in "'Xirbelschichtprozesse f~r die Chemie- und H~tten-Industrie, die Energieumwandlung un~ den Umweltschutz'i, Chem. Ing.
Techn.~ 55 (1983), No. 2, pages 87 to 93).
The lnvention will be explained more in detail by way~of example wlth reference to the drawing and the Examples.
The drawlng is a flow scheme illustrating the proceas in accordance with the invention.
A clrculati~ng fluidlzed bed system comprising a fluidized bed reactor 1,~a recycling cyclone 2 and a reoycling line~3 }s~supplied through line 4 wlth~a . ~ ~
"
~a2~i;53~3 g hydrogen fluoride-containing gas, which may have been brought to the required temperature by indirect heating or by an admixing of combustiorl gas~ The exhaust gas f the circulating fluidized bed system is discharged via the passed recycling cyclone 2 ~nd/through the venturi suspenslon heat exchanger 5, in which solids supplied from the fluidized be.d cooler 6 through line 7 are added to the gas.
The resulting gas-solids suspension is supplied through line 8 to the cyclone separator 9, in which solids are collected. Said solids are supplied through line 10 to the circulating flutdized bed system 1, 2, 3.
In the variant inv.olving an addltional cooling of the gas leaving the recycling cyclone 2, a cold ga9, such as air at ambient temperature, is supplied through line 24.
: In another venturi suspension heat exchanger 11, or alumina hydrate fresh aluminum hydroxide/supplièd through li~e 22 and addltional solids supplled from the fluldlzed bed cooler 6 : through line 12 and serving also to adjust the temperature are admlxed to the exhaust gas from the cyclone separator 9 so that another gas-solids suspension is formed. That suspension is supplied through line 13 to the cyclone separator 14, ln which solids are collected and are supplled through line 15 to the fluidized bed cooler 60 The exhaust gas~is flnally purlfied ina fine~dust collector 16~(cloth filter or~eleotrostatlc preolpltator)~and ~s then supplied to~a~wet or dry scrubber:for a~removal of residual hydrogen :
fluoride (not.~shown).
' ~26~3~ !3 The fluidized bed cooler 6 contain~ two cooling chambers 17 and 18, into wh$ch interconnected coollng surfaces 19 extend. The fluidizing gases are supplled through llne 20. By means of a star feeder 21, the solids leaving the fluidized bed cooler are distributed between lines 7 and 12.
The final product ls withdrawn from ~e circulating fluidlzed bed syst~m through line 23.
Exam?le 1 The fluidized bed reactor 1 of the circulating fluidized bed system is supplied through line 4 with gas at a rate o~ 6906 m.N /h and at a temperature ~f 570 C7 that gas contains 10.1 vol.% HF. The temperature ln the circulating fluidized bed is 530C. The mean density of the suspension is about 150 kg/m reactor volume~ The quanity of solids circulated per hour through the fluidized bed reactor:1, the recycling cyclone 2 and the re~ycling line 3 is about 50 times~the quantity of solids contained in the fluidized bed reactor 1.
~ he exhaust gas which has left the circula~ing fluidized bed system is at a temperature of 530 C a~d contains 7.5~vol.% HF as it enters~khe venturi suspenslon heat exchanger~5.~In that heat:exchanger, solids at tO0 C, ; ;
;:wh;Lch have been:supplled~from ~he fluidLze~ bed reactor 6 th:rough l~ne 7~at~a:rate of 1797 kg/h~, are added to~the :
~21653~
exhaust gas, which ~ thus cooled to 453 C. The solids collected in the cyclone separator 9 are supplled through line 10 to the fluidized bed reactor l of the circulating fluidized bed system.
The exhaust gas from the cyc:lone separator 9 or alumina hydrate contains 4.0 vol.% HF. Fresh alumlnum hydroxlde/having a moisture content of 12.0~ is supplied through line 22 at a rate of 1030 kgJh. Solids at 100C are entrained at a rate of 16,500 kg~h in lin`e 12 by the fluidizing air from the fluidized bed cooler 6. In the venturi suspension heat exGhanger 11, said fxesh aluminum hydroxlde and said solid are added to the exhaust gas from the cyclone separator 9 so tnat said exhaust gas i9 cooled to 220 C. After ~eing passed through the ayclone separator 14 and the ine exhaust gas dust collector 16 the/is supplied to a dry scrubber.
The exhaust gas becomes avallable at a rate of 8100 mN3th and contains 0.15 vol. ~ HF.
The solids which have been collected in 14 and 16 become available at a temperature of 220 C and are cooled to 100C in the fluidi~ed bed cooler 6 and are su~sequently distributed between line 7 and 12 as descrlbed hereinbefore, in a ratio of 1:9.2.
, Aluminum fluoride 2roduct at a rate of 937 kg/h ~
is withdrawn from~:the fluidlzed bed reactor 1 through line ::
23. That product has:a pu~lty of:91% (balance Al203 and igniti:on:loss).
,. ~., .
~26~i3~
In thls Example, an additional cooling with air is effected in the process in accordance with the invention.
The conditions regarding the supply of gas and the operation of the circulating fluidizad bed system are the same as in Examole 1.
As in Example 1, the exhaust gas $rom the circulating fluLdized bed system is at a temperature o~ ~30C as it enters the venturi suspension heat exchanger 5, in which solids at 100C, which have been supplied at a rat~ of 1786 kg/h from tne fluidized ~ed cooler 6 through line 7, are added to the exhaust gaq as well as air at 40C~ whioh is supplied at a rate of 1052 ~ 3/h through line 24. The gas is thu3 cooled to 420 C. Sollds colleotad in the cyclone separator 9 are supplied throu~h line 10 to the fluidized :~ed reactor 1 of the circulating fluidized ~ed syqt2m.
The axhaust gas from the cyclone ssparator 9 ,or alumina hydrate contalns 2.0 vol.% ~F. Fresh aluminum hydroxide'having a moisture content of~12.0~ is su~plled through line 22 at a rate of 1D30 kg/ll. Solids at 100 C are entrained at a rate of 15,900 kg/h in line 12 by the~fluidizing air from the fluid1zed bed cooler 6. In the venturi suspension~heat excnanger 11,~said fresh aluminum hydroxide and said ~olids are~added to~the ex~aust gas from the~cycione~separator~9 ~
o ~ so that sai~d~e~laust gas is;~cooled~to~220 C.~After~ belng ~
~ .~. , ~ : ,: : :
~2~i53~8 pa~sed through the cyclone separator 14 and the finedust collector 16 the exhaust gas is supplied to a dry serubber. The exhaust gas becomes available 3 and at a rate of 5150 mN /h;/contains 0.13 vol. % HF.
The solids which have been collected in 14 and 16 become arailable at a temperature of 220 C and are cooled to 100 C in the fluidized bed cooler 6 and are subsequently distributed between l1nes 7 and 12 as described hereinbefore, at a ratio of 1:8.9.
Aluminum fluoride product at a rate of 937 kg/h is withdrawn from the fluidized bed reactor 1 through line 23. That product has a purity of 91 % (balance Al203 and ignition loss), .
, .
.: :
~,:
:~ :
: ~ :
Claims (4)
1. A process of producing aluminum fluoride from aluminum hydroxide or alumina hydrate and hydrogen fluoride in a circulating fluidized bed system including a fluidized bed reactor, a cyclone separator and a recycling line, wherein partly reacted aluminum hydroxide circulated in a cooling cycle is added to fresh aluminum hydroxide or alumina hydrate in a first stage, in which the aluminum hydroxide is contacted with the hydrogen fluoride-containing exhaust gases from the circulating fluidized bed system so as to form a gas-solids suspension at a temperature of 150 to 250°C, whereafter the solids are collected from the gas stream, at least part of the collected solids are passed through a cooler, cooled solids are re-contacted with fresh aluminum hydroxide or alumina hydrate, and a partial stream of the collected solids is supplied to the circulating fluidized bed system and is reacted therein at a temperature of at least 450°C with hydrogen fluoride supplied in the form of a gas in a concentration up to 25 vol. %.
2. A process according to claim 1, wherein all solids collected from the gas-solids suspension are passed through the cooler.
3. A process according to claim 1, wherein the reaction in the circulating fluidized bed system is carried out at a temperature of 500 to 600°C.
4. A process according to claim 1, 2 or 3, wherein part of the solids supplied to the circulating fluidized bed system is introduced via the exhaust gas stream of the circulating fluidized bed system and an interposed separator.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19843405452 DE3405452A1 (en) | 1984-02-16 | 1984-02-16 | METHOD FOR PRODUCING ALUMINUM FLUORIDE |
| DEP3405452.9 | 1984-02-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1265318A true CA1265318A (en) | 1990-02-06 |
Family
ID=6227834
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000474437A Expired - Lifetime CA1265318A (en) | 1984-02-16 | 1985-02-15 | Process of producing aluminum fluoride |
Country Status (14)
| Country | Link |
|---|---|
| EP (1) | EP0152133B1 (en) |
| JP (1) | JPS60186415A (en) |
| AT (1) | ATE32054T1 (en) |
| AU (1) | AU575121B2 (en) |
| BR (1) | BR8500675A (en) |
| CA (1) | CA1265318A (en) |
| CS (1) | CS274602B2 (en) |
| DE (2) | DE3405452A1 (en) |
| HU (1) | HU199353B (en) |
| IN (1) | IN159125B (en) |
| MA (1) | MA20348A1 (en) |
| PL (1) | PL143342B1 (en) |
| YU (1) | YU44489B (en) |
| ZA (1) | ZA851180B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4025083A1 (en) * | 1990-08-08 | 1992-02-13 | Vaw Ver Aluminium Werke Ag | METHOD FOR REPRODUCING FLUORINATE BACKPACKS |
| CN104084095A (en) * | 2014-07-04 | 2014-10-08 | 长沙矿冶研究院有限责任公司 | Vibratory fluidized bed reactor for continuous production of rare earth fluorides and production method |
| CN104163448A (en) * | 2014-07-16 | 2014-11-26 | 宁夏金和化工有限公司 | Method and device using double fluidized bed tail gas for drying aluminum hydroxide in dry method aluminum fluoride production |
| CN108840358B (en) * | 2018-09-13 | 2023-07-18 | 衢州市鼎盛化工科技有限公司 | Device and method for preparing anhydrous aluminum fluoride |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2996354A (en) * | 1956-10-11 | 1961-08-15 | Pechiney Prod Chimiques Sa | Process for treating powdered materials with gases and resultant products |
| NL7100858A (en) * | 1970-01-27 | 1971-07-29 | ||
| GB1290749A (en) * | 1970-05-04 | 1972-09-27 | ||
| JPS5033992B1 (en) * | 1970-12-23 | 1975-11-05 | ||
| US4160809A (en) * | 1978-07-24 | 1979-07-10 | Kaiser Aluminum & Chemical Corporation | Modified pyrohydrolysis process for spent aluminum reduction cell linings |
-
1984
- 1984-02-16 DE DE19843405452 patent/DE3405452A1/en not_active Withdrawn
- 1984-06-25 IN IN442/CAL/84A patent/IN159125B/en unknown
-
1985
- 1985-01-24 EP EP85200071A patent/EP0152133B1/en not_active Expired
- 1985-01-24 DE DE8585200071T patent/DE3561454D1/en not_active Expired
- 1985-01-24 AT AT85200071T patent/ATE32054T1/en not_active IP Right Cessation
- 1985-02-05 YU YU168/85A patent/YU44489B/en unknown
- 1985-02-08 MA MA20572A patent/MA20348A1/en unknown
- 1985-02-13 BR BR8500675A patent/BR8500675A/en not_active IP Right Cessation
- 1985-02-14 CS CS105285A patent/CS274602B2/en unknown
- 1985-02-15 AU AU38788/85A patent/AU575121B2/en not_active Ceased
- 1985-02-15 CA CA000474437A patent/CA1265318A/en not_active Expired - Lifetime
- 1985-02-15 HU HU85572A patent/HU199353B/en not_active IP Right Cessation
- 1985-02-15 ZA ZA851180A patent/ZA851180B/en unknown
- 1985-02-15 PL PL1985251971A patent/PL143342B1/en unknown
- 1985-02-16 JP JP60029179A patent/JPS60186415A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE3405452A1 (en) | 1985-08-22 |
| EP0152133A1 (en) | 1985-08-21 |
| HUT36426A (en) | 1985-09-30 |
| AU3878885A (en) | 1985-08-22 |
| DE3561454D1 (en) | 1988-02-25 |
| JPS60186415A (en) | 1985-09-21 |
| CS105285A2 (en) | 1990-08-14 |
| PL143342B1 (en) | 1988-02-29 |
| EP0152133B1 (en) | 1988-01-20 |
| IN159125B (en) | 1987-03-28 |
| HU199353B (en) | 1990-02-28 |
| BR8500675A (en) | 1985-10-01 |
| YU16885A (en) | 1987-06-30 |
| YU44489B (en) | 1990-08-31 |
| MA20348A1 (en) | 1985-10-01 |
| AU575121B2 (en) | 1988-07-21 |
| ZA851180B (en) | 1986-10-29 |
| ATE32054T1 (en) | 1988-02-15 |
| CS274602B2 (en) | 1991-09-15 |
| PL251971A1 (en) | 1985-11-19 |
| JPH0446895B2 (en) | 1992-07-31 |
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