CA2084710A1 - Process for the disposal of residual materials which contain fluorine- and cyanide-containing compounds - Google Patents
Process for the disposal of residual materials which contain fluorine- and cyanide-containing compoundsInfo
- Publication number
- CA2084710A1 CA2084710A1 CA002084710A CA2084710A CA2084710A1 CA 2084710 A1 CA2084710 A1 CA 2084710A1 CA 002084710 A CA002084710 A CA 002084710A CA 2084710 A CA2084710 A CA 2084710A CA 2084710 A1 CA2084710 A1 CA 2084710A1
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- Prior art keywords
- fluidized bed
- process according
- stage
- bed system
- solids
- Prior art date
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- Abandoned
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Classifications
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D3/00—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances
- A62D3/30—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents
- A62D3/33—Processes for making harmful chemical substances harmless or less harmful, by effecting a chemical change in the substances by reacting with chemical agents by chemical fixing the harmful substance, e.g. by chelation or complexation
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
- A62D2101/40—Inorganic substances
- A62D2101/45—Inorganic substances containing nitrogen or phosphorus
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2101/00—Harmful chemical substances made harmless, or less harmful, by effecting chemical change
- A62D2101/40—Inorganic substances
- A62D2101/49—Inorganic substances containing halogen
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2203/00—Aspects of processes for making harmful chemical substances harmless, or less harmful, by effecting chemical change in the substances
- A62D2203/02—Combined processes involving two or more distinct steps covered by groups A62D3/10 - A62D3/40
-
- A—HUMAN NECESSITIES
- A62—LIFE-SAVING; FIRE-FIGHTING
- A62D—CHEMICAL MEANS FOR EXTINGUISHING FIRES OR FOR COMBATING OR PROTECTING AGAINST HARMFUL CHEMICAL AGENTS; CHEMICAL MATERIALS FOR USE IN BREATHING APPARATUS
- A62D2203/00—Aspects of processes for making harmful chemical substances harmless, or less harmful, by effecting chemical change in the substances
- A62D2203/10—Apparatus specially adapted for treating harmful chemical agents; Details thereof
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- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Processing Of Solid Wastes (AREA)
- Treating Waste Gases (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
To convert water-soluble fluorine compound to water-insoluble compounds, to decompose the cyanides and to ensure that NOx will be emitted only at a low rate, sulfates of calcium or of magnesium are added to the re-sidual materials and the latter are then treated at tem-peratures from 650 to 900°C in a two-stage fluidized bed system. The first stage is operated under slightly reducing conditions and the second stage under oxidizing conditions.
To convert water-soluble fluorine compound to water-insoluble compounds, to decompose the cyanides and to ensure that NOx will be emitted only at a low rate, sulfates of calcium or of magnesium are added to the re-sidual materials and the latter are then treated at tem-peratures from 650 to 900°C in a two-stage fluidized bed system. The first stage is operated under slightly reducing conditions and the second stage under oxidizing conditions.
Description
2~847 ~V
~etalloPsellschaft PG Frankfurt, dated January 22, 199Z
~euterweg 14 6Q00 Frankfurt-on-Main 1 Case ~!o. 88 00 84 Process for the nisposal of Resioual Materials l.lhich Conbain fluorine- an~ Cyanide-containino ComDounds nEscRIpTIo~l Some residual materials contain water-soluble fluorides and cyani~lles as well as nitro~en co~oounds an~
for this reason cannot readily be dumoed. ~uch a hazar~
dou9 residual ~at.erial is p~rticularly constituted b~
the material broken out from Furnaces used fnr the elec trolytic nro~uctinn of aluminum, which material consiats of the refractDry linin~ an~ L~f carhonaceoLIs cathsr~e ~na-terisl, or ma~ he sonstitute~ b\l the dust which is Forme~
in the electrolytic oroduction of alu~inum. For a safe ~u~noino, the blater-soluble comuounds must be converted to water~insoluble comoounds.
Fro~ JP-4~50 75 564 it is known to mix ~.~aste naterials which contain water~soluble Fluorine co~oounds, such as lininqs of electrolytic cells for the oraduction of alurninum, with calciurn salts, mainly calcium chloride and calcium sulfatel and to burn the resultinn mixtures in an oxidizinQ atrnosohere at 50U to goOaC. Electric retort furnaces and rotarv kilns are ~entioned as burninn units.
.:
z 2 ~ 0 In that process the water-soluble Fluorides are conver-ted to water-inYoluble calcium flu~rlde within a treatinq time of 30 to 60 minutes, an~ the nitrogen compound~ con-tained in the waste materials are converted to N0 , which i9 emitted with the exhaust gas. H01 gas will also be formed if calcium chloride is used.
From CE, ~1arch 19a6, oages 3L to ~8, and From "Poplication of the transoortable circulating bed com-bustor for the treatment of hazardous waste", Presenta-tion at the 79th Annual Meeting of the Air Pollution Oon-trol nssociation, ~1inneaoDlis, ~innesota, June 22-27, 19~6, it is known that after an addition of limestone ta the material broken ou-t From furnaces used for the electro-lytic production of aluminum said material can be burnt in a circulatinq flui~ized bed under oxidizing conditions at temoeratures from 790 to 870~C. The use of limestone will result in the for~ation of a molten phase, i.e., in an aqglomeration and formation of crusts.
It is an ob~ect of the invention to convert the l~ater-snluble f~uorides in the resirJual materials as comDletelv as possible to watrJr-insoluble comooun~s, to l~ecomnose t,he cvanides as completel~/ as oogsible, an~
also substantiallv to avoid a formation of ~x derived from the nitro~en ~oound3.
That object is accomplished in accordance with the invention by a process which serves for the ~isposal .
: , ~ 3 ~ 2~7~0 of resldual materials which contain fluorine- and cya-nide-containing compounds ano which is characterized in that a) the residual materials are thermally treated after an addition of calcium and/or magnesium, b) the thermal treatment is efFected in a two-stage fluidizeo bed system, c) a temoerature from 650 to 900C is maintained in the two-stage fluidized bed systern, d) the first stane of the fluidized bed svstem is ,slightly ooerat~d under'reducino conditions with an air ratio C1, e) th~ secwnd staoe of the Flui~ized berl system i5 Dperated under oxidizing conditians with an oxyqen content ~ 2~,'c by volume, a~d f) the treated material is withdrawn from the se-cond staqeO
The sulfates are used at a hyperstolchiometric rate as regaros the formation of CaFz or ~F2 From the water-soluble fluorides. Inexoensive waste gypsum can ~e-sirably be used as calcium sulFate and will thus be dis-Dosed oF at the same tirne. The tl,Jo-stao,e fluidize~ bed system may consist of a circulatino, Fluidized bed system, in which the First fluidized bed is Formed in the lawer oart of the Fluidized bed reactor bv means of the fluidiz-ing air flowino throunh the bottDm and the secon~ Fluidized bed is formed in an uooer part of the Fluidized bed reactor ~ 4 ~ 2~8~7~0 by means of secondary air and optionally tertiary air.
Alternatively, the two-stage fluidized beri system may comprise two separate orthodox fluidlzed be~ units and in that case the solids and the gas are withdrawn from the first fluidized bed unit and supplieo to the second flui-dized bed unit. The temoerature in the First fluidized bed will alwa~s lie in the lower oart of the temperature ranoe stated because en~othermic reactions are performed in the first fluidized bed awinq to the deficiency oF
oxygen. P9 the residual material i9 charged into a circu-lating fluidized bed system Lt has a particle size oelow ~ m, preferably below 1 mm, and as the material is charqed into an orthodox fluidized bed system it has a particle size below 3 mm, preferably balo~ ~ rnm. The ma-terial is always charoecl into the first staqe. The resiriual material rnay be suoDlied in 3 solid state or as a slurry. In case of a orocessinr-~ of material broken out from furnaces for the electrolytic production of aluminu~ the feed material will contain in most cases carbon in such an amount that its combustion will generate the reaction heat which i9 required. If the resi~ual material rloes not contain enouclh carbon, the additional amount required will be su~plierl as solid, liquid or gaseous Fuel. ~n ootimum temoerature for the reaction is suitablv adjusted bv 3 suitable coolino of the aolids and where twa orthodox fluidiz2d bed urlits - 5 - 2~8~7~0 are employeo that coolinq will be eFFected between said units whereas in case oF a circulating fluidized bed system the solids seDarated from the d;scharged suspe~-sion will be cooled before they are recyc:led to the flui-dized bed reactor.
The advanta~es afforded by the invention reside in that the water-soluble Fluorine compounds are substan-tially converted to oater-insoluble compounds, the cyanides are substantially decomposed and the resulting exhaust gas has a low content of N0 and this is accomDlished without an occurrence of aoolomnration and a formation of crusts, Pccordino to a oreferred feature a temperature oF 750 to ~50C is maintained in the two-stage fluidized becl system. Pn effective conversion to water-lnsoluble fluorides and an effective decomoosition of the cyanides in conjunction with a formation of ~lO at a low rate are achieved at temperatures in that range and HF will be even emitted at a low rate/in the oresence of water.
According to a preFerred feature the first stage of the fluioized bed system is operated with an air ratio of 0.7 to 0.9. This will result in an emission of ~10x at a very low rate.
According to a oreferred feature the second stacle of the fluioize~ bed svstem is ooerated with an oxyclen content of 6 to 10~', bv volume. This will result in a very %0~710 effective decomposition oF the cyanioes and in an effec-tive cnnversion tu water-lnsoluble fluQrides and in an emlssion of ~Ix at a very law rate.
According to a preferred feature, sulFates of calcium and/or of mar~nesium are added at a rate which i9 1.2 to 1.5 times the rate which is stoichiornetrically re-quired for thr-~ conversion of the water-soluble fluorides contained in the residual ~aterial to CaF2 or MgF2, In that case the addition of the sulfates at a relatively low rate will result in an efFective cQnversion to water-in-soluble fluorides.
Addording to a preferrecl feature in case of the processing of residual materials having a high SiO2 con-tent an Al203 content of at leas-t 15% by weioht i5 adjusted in the mixture by an addition of substances which contain Qlz03. That addition will be requried if the SiOz content i5 about 30~ ar more. The material which contains Al203 may consist of Al203, bauxite, clay, flue dust t sodium si-licate or the like. This will avoid the formation of a rnol ten phase in the presence of a high S~02 content.
~ccording to a ~referred featur~ the two-star~e /is effected and treat~ent in a circulatino fluidized bed svstern/is accornDa-nied by a supolv of secondary air and ootionally tertiary air to the uoper part of the fluidize~ bed reactor. The fluidized bed system consists of a fluidized bed reactor, a recycle cyclone and a recycle line. I~hereas in an .:
.
: ' .
., 20~471 ~
"orthodox" Fluidlzed bed 9y9tem a d~n~e phase i~ ~epa-rated by a distinct density step ~rom the ouerlying gas space, a circulating fluidized bed system involves states of distribution having no deFined boundary layer. There i9 no density steo between a dense ,ohase and an overlying dust soace but in the fluldized bed reactor the solids concentration decreases qradually From bottom to too. A
gas-solids suspension is discharged from the upper part of the reactor. The followin~ ranges will be obtained if the operating conditions are defineo by the Froude and Archimedes numbers: g û.1 < 3/4 x Fr2 x ~ ~ 10 an~0.01 ~ ar C 10Q
wherein 3 d x q (~
~r = D
J g X .~) 2 FrZ = u g x dk and u = the relative oas velocity in m/sec.
ar = the Prchimedes number Fr = the Froude number ~;9 = the densitv of the gas in kn/mZ
~k = the density of the solid particle in kq/mZ
dk = the diameter of thesolidspherical particle in m ~ = the kinematic viscosity in mZ/sec.
g - the constant o~ aravitation in m/secZ.
2~47~
- B -The suspen3ion discharged form the fluidized bed reastnr i~ supplied to the recycle cyclone of the circu-lating fluldized bed system and solids are subatantially removed in that cyclone and are recycled to the flui-dized bed reactor of such a rate that the amount of solids within the circulatinn fluidized bed system per hour is at lea~t four times the b~eight of the solids contained in the fluidized bed reactor. The solids which have been se-parated and are to be recycled are recycled to the first staqe of the fluidized bed reactor. The first stage ex-tends form the bottom of the fluidized bed reactor over about 20 to 4U~ of the total height oF the fluidized bed reactor. In the circulating fluidized bed system the re-quired operating parameters can be very exactly maintained so that particularly good results can be oroduced.
According to a preferred feature the solids to be recyoled are cooled in a fluidized bed cooler before they are charged into the fluidized bed reactor. The flui-dized bed cooler consists of an orthodox fulidized bed unit. The heated fluidizing air leaving the fluidized bed cooler may be supplied to the unit for purifying the ex-hauat qas that has leFt the circulating Fluidized bed sys-tem, or may be supplied as secondary air to the Fluidized bed reactor. The coolinn in the fluidized bed cooler per-mits an effective and ~imple automatic con-trol of the tem-perature in the circulatinq fluidized bed system.
- ~ 208~7~
~ ccording to a preferred feature the solids which have been withdrawn are aFtertreated by being slur-ried. 50 much water is added that a transportakion withoLIt a raising of dust and/or a dumping without a raising of dust will be possible. The ~lurrying will also result in a ~urther decrease of the solid fluorine compound~. If the thermally treated solids are aftertreated it will be preferable to add a part of the calcium ~ulfate or magne-sium sulfate during the aftertreatment rather than during the thermal treatment.
The ~nveotion will be explained more in detail with reFerence to a flow scheme and to examples.
Figure 1 i9 a Flow scheme of a plank cnmprising a circulating fluirlized bed sy~tem.
The Fluidizecl bed system comprises a fluidized bed reactor 1, a recycle cyclone 2 and a recycle line 3.
Material broken out of a furnace and having a suitable particle size i3 charged through line 4 into a mixer ~, which is supplied with calcium suifate through line 6 and with an Alz03-containing material khrouqh line 7. Through line U the mixture is charged into the lo~er part of the Fluidized bed reactor 1. Fluidizing air is supplied to the reactor through its bottom from line 9 and in the lower part of the Fluidized bed reactor is used to form the first fluidized bed. 5econdary air from line 10 and tertiary air from line 11 are suoPlied to the upper part of the fluidized bed reactor and in said upper part are used to form the '~ ' ' ,.
. : `
2~8~
_ 10 -second fluidized bed. The gas-salids suspension is conduc-ted in line 1Z from the Fluidized bed reactor 1 to the recycle cyclone Z. ~he collected solids are recycled in the recycle line 3 to the lower part of the Fluidized bed reactor. All or part of the separated solids can be supplied through line 13 to the fluidized bed cooler 14, which consists of an orthodox fluidized bed unit and is supplied with fluidizing air through line 15. The cooled solids are recycled in line 16 to the lower part of the Fluidized bed reactor 1. From the separating cyclone Z
the gas phase is conducted in line 17 to a second cyclone 1B, from which the collected solids are recycled in line 19 to the lower part oF the Fluidized bed reactor 1. The gas phase From the cyclone 1e i9 conducted in line Z0 to the venturi scrubber Z1. Dust-containing fluidized air which has been heated in the Fluidized bed cooler 14 is supplied in line ZZ also to the venturi scruboer Z1, from which the gas is supplied in line 23 to a wet-proces~ de-duster Z4. The puriFied gas is discharged through line 75. The sludge Formed in the wet-orocess deduster is sup-plied in line 26 to the sedimentatian tank Z7. The over-Flow is suoolied ln line ZB to the venturi scrubber Z1 and the underflow is supplied in line 29 to the stirred tank 30, which is supplied with calcium sulfate From line 31.
The suspension is supplied in line 3Z to the mixer 33, .
:, - ' :
2~8~710 which i9 supplied in line 34 with separated salids from the fluidized bed cooler. The separated solids are after-treated in the stirred tank 30 and in the mixer 33. The solids are conducted in line 35 to the dump.
In the following table the results are stated which have been produced by a treatment of material which has been broken out from a furnace used in the electroly-tic production of aluminum. In experiments 7 and ~ the material broken out from the furnace and having the sta-ted comoosition was used as feed material without an addi-tive. In experiments 1 to 6 an identical material bro~en out from the furnace was mixed with AlzO~ In experiments 9 ta 17 a different material broken out from a furnace and having the stated composition was usPd without an addition of Plz03-containinq substances. In all cases, calcium 5ul-fate or calcium carbonate was added in a molar ratio of Ca:F oF 0.6. The data for exoeriments 1 to 3 and 8 reflect the results of control exoeriments in which calicum sulfate was not added. The data for experiments 5 and 6 reflect the results produced when calcium carbonate rather than calcium sulfate was added. The data for experiments 7 and S
reflect the results produced when the m~terial broken out from the furnace had a very high SiOz content. In the column "Solubility" the solubility is stated which was obtained by a leaching accordinn to DEV-S4. In experiment 12, 5% CaS04 were added during the thermal treatment and Z.7% CaS04 were added durin~ the aftertreatment.
v ., ~ 0 8 4 7 ~ 0 E ¦ h h h h C: I ~ ~ ~ O ~o~ Jl '', .
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F.r~ ~ O O O CO C~l O ca co a a ~ ca ~a c~
L~ ~ ~ ~0. cn I~ O
2~ N O CO ~ CO 1~ CO
w o ~ n a; co a ~ I a ~ D ~ O O O O
C E O ~ O O co ~ C`~! CO
IJ_ ~ ~ ~ ~ ~ I I I I
U~ I
2 o. ~ I I I I
I ~ I
Ll~c~N Cl ¦ o o O O m o o O
~e ~ cO co r ~ ~ r o uJ O
~ m r~ n .~1 1:1 OJ Or~ O O C:) C~ O 0 o ,i u~ o o UJ UJ U~ U ~) hct:`f EO L.l N N N N N N N N N N N N
.rl hh ~ ~ ~ ~- ~ ~ ~ ~ ~ ~ ~ ~ ~
h ,1 N cT~ cr cr cn cr~ CJ~ ~ cr~ C~ cn cr cL ~ O O O O O O O O O O o ~.
hE O u~ o O O O O O O O O O O
~ o C~ m m In m m m ~n O O O O
~ U~ co co rO CO ~0 ~0 a~ ~0 ~ J J J
2 ~3 O o O O O O O O O O O O
~ucl ae I ~ O w ~ ~ ~
hIU Ul ~ ~ ~ ~ ~ ~ ~ O O O O
r~3 ooooooooc;OOO
E o~~ C
t~ ~
h ~ ~EIe N N N co C~J N ~ ~-- CO CO LO CO
O ,~ ~ ~ ~ ~ ~ ~- ~ ~ ~ ~ ~ ~
O ~ U~ 43 u~ IQ I ~o ~ O J t ~ O
m E~o ~ co co ~D co co co r ~ o w ~ h Z 3 ~ ~ ~ ~
CN ae ~ o ~ o ~o ~ .,~ +~ o o o o o o ~ r N N N N
'N tl~ 3 N N N N N N J J
C
~1 ON ~e ¦ cO cO cO cO cO co CO CO CO CO CO CO
r h '~ +' I 1~ 1 ~ ~i .L! ~D
L~ ~ ~: 3 ~ J ~ J ~ ~ ~ ~ r~
~ . . I
.
.
~etalloPsellschaft PG Frankfurt, dated January 22, 199Z
~euterweg 14 6Q00 Frankfurt-on-Main 1 Case ~!o. 88 00 84 Process for the nisposal of Resioual Materials l.lhich Conbain fluorine- an~ Cyanide-containino ComDounds nEscRIpTIo~l Some residual materials contain water-soluble fluorides and cyani~lles as well as nitro~en co~oounds an~
for this reason cannot readily be dumoed. ~uch a hazar~
dou9 residual ~at.erial is p~rticularly constituted b~
the material broken out from Furnaces used fnr the elec trolytic nro~uctinn of aluminum, which material consiats of the refractDry linin~ an~ L~f carhonaceoLIs cathsr~e ~na-terisl, or ma~ he sonstitute~ b\l the dust which is Forme~
in the electrolytic oroduction of alu~inum. For a safe ~u~noino, the blater-soluble comuounds must be converted to water~insoluble comoounds.
Fro~ JP-4~50 75 564 it is known to mix ~.~aste naterials which contain water~soluble Fluorine co~oounds, such as lininqs of electrolytic cells for the oraduction of alurninum, with calciurn salts, mainly calcium chloride and calcium sulfatel and to burn the resultinn mixtures in an oxidizinQ atrnosohere at 50U to goOaC. Electric retort furnaces and rotarv kilns are ~entioned as burninn units.
.:
z 2 ~ 0 In that process the water-soluble Fluorides are conver-ted to water-inYoluble calcium flu~rlde within a treatinq time of 30 to 60 minutes, an~ the nitrogen compound~ con-tained in the waste materials are converted to N0 , which i9 emitted with the exhaust gas. H01 gas will also be formed if calcium chloride is used.
From CE, ~1arch 19a6, oages 3L to ~8, and From "Poplication of the transoortable circulating bed com-bustor for the treatment of hazardous waste", Presenta-tion at the 79th Annual Meeting of the Air Pollution Oon-trol nssociation, ~1inneaoDlis, ~innesota, June 22-27, 19~6, it is known that after an addition of limestone ta the material broken ou-t From furnaces used for the electro-lytic production of aluminum said material can be burnt in a circulatinq flui~ized bed under oxidizing conditions at temoeratures from 790 to 870~C. The use of limestone will result in the for~ation of a molten phase, i.e., in an aqglomeration and formation of crusts.
It is an ob~ect of the invention to convert the l~ater-snluble f~uorides in the resirJual materials as comDletelv as possible to watrJr-insoluble comooun~s, to l~ecomnose t,he cvanides as completel~/ as oogsible, an~
also substantiallv to avoid a formation of ~x derived from the nitro~en ~oound3.
That object is accomplished in accordance with the invention by a process which serves for the ~isposal .
: , ~ 3 ~ 2~7~0 of resldual materials which contain fluorine- and cya-nide-containing compounds ano which is characterized in that a) the residual materials are thermally treated after an addition of calcium and/or magnesium, b) the thermal treatment is efFected in a two-stage fluidizeo bed system, c) a temoerature from 650 to 900C is maintained in the two-stage fluidized bed systern, d) the first stane of the fluidized bed svstem is ,slightly ooerat~d under'reducino conditions with an air ratio C1, e) th~ secwnd staoe of the Flui~ized berl system i5 Dperated under oxidizing conditians with an oxyqen content ~ 2~,'c by volume, a~d f) the treated material is withdrawn from the se-cond staqeO
The sulfates are used at a hyperstolchiometric rate as regaros the formation of CaFz or ~F2 From the water-soluble fluorides. Inexoensive waste gypsum can ~e-sirably be used as calcium sulFate and will thus be dis-Dosed oF at the same tirne. The tl,Jo-stao,e fluidize~ bed system may consist of a circulatino, Fluidized bed system, in which the First fluidized bed is Formed in the lawer oart of the Fluidized bed reactor bv means of the fluidiz-ing air flowino throunh the bottDm and the secon~ Fluidized bed is formed in an uooer part of the Fluidized bed reactor ~ 4 ~ 2~8~7~0 by means of secondary air and optionally tertiary air.
Alternatively, the two-stage fluidized beri system may comprise two separate orthodox fluidlzed be~ units and in that case the solids and the gas are withdrawn from the first fluidized bed unit and supplieo to the second flui-dized bed unit. The temoerature in the First fluidized bed will alwa~s lie in the lower oart of the temperature ranoe stated because en~othermic reactions are performed in the first fluidized bed awinq to the deficiency oF
oxygen. P9 the residual material i9 charged into a circu-lating fluidized bed system Lt has a particle size oelow ~ m, preferably below 1 mm, and as the material is charqed into an orthodox fluidized bed system it has a particle size below 3 mm, preferably balo~ ~ rnm. The ma-terial is always charoecl into the first staqe. The resiriual material rnay be suoDlied in 3 solid state or as a slurry. In case of a orocessinr-~ of material broken out from furnaces for the electrolytic production of aluminu~ the feed material will contain in most cases carbon in such an amount that its combustion will generate the reaction heat which i9 required. If the resi~ual material rloes not contain enouclh carbon, the additional amount required will be su~plierl as solid, liquid or gaseous Fuel. ~n ootimum temoerature for the reaction is suitablv adjusted bv 3 suitable coolino of the aolids and where twa orthodox fluidiz2d bed urlits - 5 - 2~8~7~0 are employeo that coolinq will be eFFected between said units whereas in case oF a circulating fluidized bed system the solids seDarated from the d;scharged suspe~-sion will be cooled before they are recyc:led to the flui-dized bed reactor.
The advanta~es afforded by the invention reside in that the water-soluble Fluorine compounds are substan-tially converted to oater-insoluble compounds, the cyanides are substantially decomposed and the resulting exhaust gas has a low content of N0 and this is accomDlished without an occurrence of aoolomnration and a formation of crusts, Pccordino to a oreferred feature a temperature oF 750 to ~50C is maintained in the two-stage fluidized becl system. Pn effective conversion to water-lnsoluble fluorides and an effective decomoosition of the cyanides in conjunction with a formation of ~lO at a low rate are achieved at temperatures in that range and HF will be even emitted at a low rate/in the oresence of water.
According to a preFerred feature the first stage of the fluioized bed system is operated with an air ratio of 0.7 to 0.9. This will result in an emission of ~10x at a very low rate.
According to a oreferred feature the second stacle of the fluioize~ bed svstem is ooerated with an oxyclen content of 6 to 10~', bv volume. This will result in a very %0~710 effective decomposition oF the cyanioes and in an effec-tive cnnversion tu water-lnsoluble fluQrides and in an emlssion of ~Ix at a very law rate.
According to a preferred feature, sulFates of calcium and/or of mar~nesium are added at a rate which i9 1.2 to 1.5 times the rate which is stoichiornetrically re-quired for thr-~ conversion of the water-soluble fluorides contained in the residual ~aterial to CaF2 or MgF2, In that case the addition of the sulfates at a relatively low rate will result in an efFective cQnversion to water-in-soluble fluorides.
Addording to a preferrecl feature in case of the processing of residual materials having a high SiO2 con-tent an Al203 content of at leas-t 15% by weioht i5 adjusted in the mixture by an addition of substances which contain Qlz03. That addition will be requried if the SiOz content i5 about 30~ ar more. The material which contains Al203 may consist of Al203, bauxite, clay, flue dust t sodium si-licate or the like. This will avoid the formation of a rnol ten phase in the presence of a high S~02 content.
~ccording to a ~referred featur~ the two-star~e /is effected and treat~ent in a circulatino fluidized bed svstern/is accornDa-nied by a supolv of secondary air and ootionally tertiary air to the uoper part of the fluidize~ bed reactor. The fluidized bed system consists of a fluidized bed reactor, a recycle cyclone and a recycle line. I~hereas in an .:
.
: ' .
., 20~471 ~
"orthodox" Fluidlzed bed 9y9tem a d~n~e phase i~ ~epa-rated by a distinct density step ~rom the ouerlying gas space, a circulating fluidized bed system involves states of distribution having no deFined boundary layer. There i9 no density steo between a dense ,ohase and an overlying dust soace but in the fluldized bed reactor the solids concentration decreases qradually From bottom to too. A
gas-solids suspension is discharged from the upper part of the reactor. The followin~ ranges will be obtained if the operating conditions are defineo by the Froude and Archimedes numbers: g û.1 < 3/4 x Fr2 x ~ ~ 10 an~0.01 ~ ar C 10Q
wherein 3 d x q (~
~r = D
J g X .~) 2 FrZ = u g x dk and u = the relative oas velocity in m/sec.
ar = the Prchimedes number Fr = the Froude number ~;9 = the densitv of the gas in kn/mZ
~k = the density of the solid particle in kq/mZ
dk = the diameter of thesolidspherical particle in m ~ = the kinematic viscosity in mZ/sec.
g - the constant o~ aravitation in m/secZ.
2~47~
- B -The suspen3ion discharged form the fluidized bed reastnr i~ supplied to the recycle cyclone of the circu-lating fluldized bed system and solids are subatantially removed in that cyclone and are recycled to the flui-dized bed reactor of such a rate that the amount of solids within the circulatinn fluidized bed system per hour is at lea~t four times the b~eight of the solids contained in the fluidized bed reactor. The solids which have been se-parated and are to be recycled are recycled to the first staqe of the fluidized bed reactor. The first stage ex-tends form the bottom of the fluidized bed reactor over about 20 to 4U~ of the total height oF the fluidized bed reactor. In the circulating fluidized bed system the re-quired operating parameters can be very exactly maintained so that particularly good results can be oroduced.
According to a preferred feature the solids to be recyoled are cooled in a fluidized bed cooler before they are charged into the fluidized bed reactor. The flui-dized bed cooler consists of an orthodox fulidized bed unit. The heated fluidizing air leaving the fluidized bed cooler may be supplied to the unit for purifying the ex-hauat qas that has leFt the circulating Fluidized bed sys-tem, or may be supplied as secondary air to the Fluidized bed reactor. The coolinn in the fluidized bed cooler per-mits an effective and ~imple automatic con-trol of the tem-perature in the circulatinq fluidized bed system.
- ~ 208~7~
~ ccording to a preferred feature the solids which have been withdrawn are aFtertreated by being slur-ried. 50 much water is added that a transportakion withoLIt a raising of dust and/or a dumping without a raising of dust will be possible. The ~lurrying will also result in a ~urther decrease of the solid fluorine compound~. If the thermally treated solids are aftertreated it will be preferable to add a part of the calcium ~ulfate or magne-sium sulfate during the aftertreatment rather than during the thermal treatment.
The ~nveotion will be explained more in detail with reFerence to a flow scheme and to examples.
Figure 1 i9 a Flow scheme of a plank cnmprising a circulating fluirlized bed sy~tem.
The Fluidizecl bed system comprises a fluidized bed reactor 1, a recycle cyclone 2 and a recycle line 3.
Material broken out of a furnace and having a suitable particle size i3 charged through line 4 into a mixer ~, which is supplied with calcium suifate through line 6 and with an Alz03-containing material khrouqh line 7. Through line U the mixture is charged into the lo~er part of the Fluidized bed reactor 1. Fluidizing air is supplied to the reactor through its bottom from line 9 and in the lower part of the Fluidized bed reactor is used to form the first fluidized bed. 5econdary air from line 10 and tertiary air from line 11 are suoPlied to the upper part of the fluidized bed reactor and in said upper part are used to form the '~ ' ' ,.
. : `
2~8~
_ 10 -second fluidized bed. The gas-salids suspension is conduc-ted in line 1Z from the Fluidized bed reactor 1 to the recycle cyclone Z. ~he collected solids are recycled in the recycle line 3 to the lower part of the Fluidized bed reactor. All or part of the separated solids can be supplied through line 13 to the fluidized bed cooler 14, which consists of an orthodox fluidized bed unit and is supplied with fluidizing air through line 15. The cooled solids are recycled in line 16 to the lower part of the Fluidized bed reactor 1. From the separating cyclone Z
the gas phase is conducted in line 17 to a second cyclone 1B, from which the collected solids are recycled in line 19 to the lower part oF the Fluidized bed reactor 1. The gas phase From the cyclone 1e i9 conducted in line Z0 to the venturi scrubber Z1. Dust-containing fluidized air which has been heated in the Fluidized bed cooler 14 is supplied in line ZZ also to the venturi scruboer Z1, from which the gas is supplied in line 23 to a wet-proces~ de-duster Z4. The puriFied gas is discharged through line 75. The sludge Formed in the wet-orocess deduster is sup-plied in line 26 to the sedimentatian tank Z7. The over-Flow is suoolied ln line ZB to the venturi scrubber Z1 and the underflow is supplied in line 29 to the stirred tank 30, which is supplied with calcium sulfate From line 31.
The suspension is supplied in line 3Z to the mixer 33, .
:, - ' :
2~8~710 which i9 supplied in line 34 with separated salids from the fluidized bed cooler. The separated solids are after-treated in the stirred tank 30 and in the mixer 33. The solids are conducted in line 35 to the dump.
In the following table the results are stated which have been produced by a treatment of material which has been broken out from a furnace used in the electroly-tic production of aluminum. In experiments 7 and ~ the material broken out from the furnace and having the sta-ted comoosition was used as feed material without an addi-tive. In experiments 1 to 6 an identical material bro~en out from the furnace was mixed with AlzO~ In experiments 9 ta 17 a different material broken out from a furnace and having the stated composition was usPd without an addition of Plz03-containinq substances. In all cases, calcium 5ul-fate or calcium carbonate was added in a molar ratio of Ca:F oF 0.6. The data for exoeriments 1 to 3 and 8 reflect the results of control exoeriments in which calicum sulfate was not added. The data for experiments 5 and 6 reflect the results produced when calcium carbonate rather than calcium sulfate was added. The data for experiments 7 and S
reflect the results produced when the m~terial broken out from the furnace had a very high SiOz content. In the column "Solubility" the solubility is stated which was obtained by a leaching accordinn to DEV-S4. In experiment 12, 5% CaS04 were added during the thermal treatment and Z.7% CaS04 were added durin~ the aftertreatment.
v ., ~ 0 8 4 7 ~ 0 E ¦ h h h h C: I ~ ~ ~ O ~o~ Jl '', .
C~
F.r~ ~ O O O CO C~l O ca co a a ~ ca ~a c~
L~ ~ ~ ~0. cn I~ O
2~ N O CO ~ CO 1~ CO
w o ~ n a; co a ~ I a ~ D ~ O O O O
C E O ~ O O co ~ C`~! CO
IJ_ ~ ~ ~ ~ ~ I I I I
U~ I
2 o. ~ I I I I
I ~ I
Ll~c~N Cl ¦ o o O O m o o O
~e ~ cO co r ~ ~ r o uJ O
~ m r~ n .~1 1:1 OJ Or~ O O C:) C~ O 0 o ,i u~ o o UJ UJ U~ U ~) hct:`f EO L.l N N N N N N N N N N N N
.rl hh ~ ~ ~ ~- ~ ~ ~ ~ ~ ~ ~ ~ ~
h ,1 N cT~ cr cr cn cr~ CJ~ ~ cr~ C~ cn cr cL ~ O O O O O O O O O O o ~.
hE O u~ o O O O O O O O O O O
~ o C~ m m In m m m ~n O O O O
~ U~ co co rO CO ~0 ~0 a~ ~0 ~ J J J
2 ~3 O o O O O O O O O O O O
~ucl ae I ~ O w ~ ~ ~
hIU Ul ~ ~ ~ ~ ~ ~ ~ O O O O
r~3 ooooooooc;OOO
E o~~ C
t~ ~
h ~ ~EIe N N N co C~J N ~ ~-- CO CO LO CO
O ,~ ~ ~ ~ ~ ~ ~- ~ ~ ~ ~ ~ ~
O ~ U~ 43 u~ IQ I ~o ~ O J t ~ O
m E~o ~ co co ~D co co co r ~ o w ~ h Z 3 ~ ~ ~ ~
CN ae ~ o ~ o ~o ~ .,~ +~ o o o o o o ~ r N N N N
'N tl~ 3 N N N N N N J J
C
~1 ON ~e ¦ cO cO cO cO cO co CO CO CO CO CO CO
r h '~ +' I 1~ 1 ~ ~i .L! ~D
L~ ~ ~: 3 ~ J ~ J ~ ~ ~ ~ r~
~ . . I
.
.
Claims (15)
1. A process which serves for the disposal of residual materials which contain fluorine- and cyanide-containing compounds, characterized in that:
a) the residual materials are thermally treated after an addition of calcium and/or magnesium, b) the thermal treatment is effected in a two-stage fluidized bed system, c) a temperature from 650 to 900°C is maintained in the two-stage fluidized bed system, d) the first stage of the fluidized bed system is operated under slightly reducing conditions with an air ratio < 1, e) the second stage of the fluidized bed system is operated under oxidizing conditions with an oxygen content > 2% by volume, and f) the treated material is withdrawn from the second stage.
a) the residual materials are thermally treated after an addition of calcium and/or magnesium, b) the thermal treatment is effected in a two-stage fluidized bed system, c) a temperature from 650 to 900°C is maintained in the two-stage fluidized bed system, d) the first stage of the fluidized bed system is operated under slightly reducing conditions with an air ratio < 1, e) the second stage of the fluidized bed system is operated under oxidizing conditions with an oxygen content > 2% by volume, and f) the treated material is withdrawn from the second stage.
2. A process according to claim 1, characterized in that a temperature from 750 to 850°C is maintained in the two-stage fluidized bed system.
3. A process according to claim 1 or 2, characte-rized in that the first stage of the fluidized bed system is operated with an air ratio from 0.7 to 0.9.
4. A process according to claim 1, characterized in that the second stage of the fluidized bed system is operated with an oxygen content from 6 to 10% by volume.
5. A process according to claim 1, characterized in that sulfates of calcium and/or of magnesium are added at a rate which is 1.2 to 1.5 times the rate which is stoichiometrically required for the conversion of the water-soluble fluorides contained in the residual material to CaF2 or MgF2.
6. A process according to claim 1, characterized in that in case of the processing of residual materials having a high SiO2 content an Al2O3 content of at least 15%
by weight is adjusted in the mixture by an addition of substances which contain Al2O3.
by weight is adjusted in the mixture by an addition of substances which contain Al2O3.
7. A process according to claim 1, characterized in that the two-stage treatment is effected in a circulating fluidized bed system and is accompanied by a supply of secondary air and optionally tertiary air to the upper part of the fluidized bed reactor.
8. A process according to claim 7, characterized in that the solids to be recycled are cooled in a fluidized bed cooler before they are charged into the fluidized bed reactor.
9. A process according to claim 1, characterized in that the solids which have been withdrawn are aftertreated by being slurried.
10. A process according to claim 3, characterized in that the second stage of the fluidized bed system is operated with an oxygen content from 6 to 10% by volume.
11. A process according to claim 10, characterized in that sulfates of calcium and/or of magnesium are added at a rate which is 1.2 to 1.5 times the rate which is stoichiometrically required for the conversion of the water-soluble fluorides contained in the residual material to CaF2 or MgF2.
12. A process according to claim 1, 2, 4, 5, 10 or 11, characterized in that in case of the processing of residual materials having a high SiO2 content an Al2O3 content of at least 15% by weight is adjusted in the mixture by an addition of substances which contain Al2O3.
13. A process according to claim 1, 2, 4, 5, 10 or 11, characterized in that the two-stage treatment is effected in a circulating fluidized bed system and is accompanied by a supply of secondary air and optionally tertiary air to the upper part of the fluidized bed reactor.
14. A process according to claim 13, characte-rized in that the solids to be recycled are cooled in a fluidized bed cooler before they are charged into the fluidized bed reactor.
15. A process according to claim 1, 2, 4, 5, 10, 11 or 14, characterized in that the solids which have been withdrawn are aftertreated by being slurried.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19924201831 DE4201831A1 (en) | 1992-01-24 | 1992-01-24 | METHOD FOR THE DISPOSAL OF RESIDUES CONTAINING FLUORINE AND CYANIDE CONTAINERS |
| DEP4201831.5 | 1992-01-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2084710A1 true CA2084710A1 (en) | 1993-07-25 |
Family
ID=6450128
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002084710A Abandoned CA2084710A1 (en) | 1992-01-24 | 1992-12-07 | Process for the disposal of residual materials which contain fluorine- and cyanide-containing compounds |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0553511A1 (en) |
| AU (1) | AU652881B2 (en) |
| CA (1) | CA2084710A1 (en) |
| DE (1) | DE4201831A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1917209A1 (en) * | 2005-08-23 | 2008-05-07 | Studsvik, Inc. | Mineralization of alkali metals, sulfur and halogens |
| CN103239828A (en) * | 2013-05-31 | 2013-08-14 | 吴正建 | Harmless production process of program-control and manual-control electrolytic aluminum overhaul residues |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5558690A (en) * | 1994-12-23 | 1996-09-24 | Vortec Corporation | Manufacture of ceramic tiles from spent aluminum potlining |
| US5660125A (en) * | 1995-05-05 | 1997-08-26 | Combustion Engineering, Inc. | Circulating fluid bed steam generator NOx control |
| DE19723194C2 (en) * | 1996-09-18 | 2000-05-18 | Kerr Mcgee Pigments Gmbh & Co | Process for the processing of nitrogenous organic waste |
| US6371970B1 (en) | 1999-07-30 | 2002-04-16 | Incept Llc | Vascular filter having articulation region and methods of use in the ascending aorta |
| US6540768B1 (en) | 2000-02-09 | 2003-04-01 | Cordis Corporation | Vascular filter system |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4355017A (en) * | 1981-05-14 | 1982-10-19 | Martin Marietta Corporation | Aluminum electrolytic cell cathode waste recovery |
| DE3426913A1 (en) * | 1984-07-20 | 1986-01-30 | Adsorptionstech Lab | METHOD FOR THE REMOVAL OF NITROGEN OXIDES AND FOR THE COMMON REMOVAL OF NITROGEN OXIDS AND SULFUR OXIDS FROM GASES |
| CA1294111C (en) * | 1986-08-08 | 1992-01-14 | Douglas J. Hallett | Process for the destruction of organic waste material |
| DE3640318A1 (en) * | 1986-11-26 | 1988-06-09 | Boehringer Mannheim Gmbh | METHOD AND TEST CARRIER FOR DETERMINING AN ANALYT |
| GB2198722B (en) * | 1986-12-22 | 1991-04-17 | Comalco Alu | Process for the recovery of fluoride values |
| NO176648C (en) * | 1991-11-07 | 1995-05-10 | Elkem Technology | Method of treating used cathode bottom |
-
1992
- 1992-01-24 DE DE19924201831 patent/DE4201831A1/en not_active Withdrawn
- 1992-12-03 EP EP92203736A patent/EP0553511A1/en not_active Withdrawn
- 1992-12-07 CA CA002084710A patent/CA2084710A1/en not_active Abandoned
-
1993
- 1993-01-22 AU AU31941/93A patent/AU652881B2/en not_active Ceased
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1917209A1 (en) * | 2005-08-23 | 2008-05-07 | Studsvik, Inc. | Mineralization of alkali metals, sulfur and halogens |
| EP1917209A4 (en) * | 2005-08-23 | 2008-12-03 | Studsvik Inc | Mineralization of alkali metals, sulfur and halogens |
| CN103239828A (en) * | 2013-05-31 | 2013-08-14 | 吴正建 | Harmless production process of program-control and manual-control electrolytic aluminum overhaul residues |
Also Published As
| Publication number | Publication date |
|---|---|
| AU652881B2 (en) | 1994-09-08 |
| DE4201831A1 (en) | 1993-07-29 |
| EP0553511A1 (en) | 1993-08-04 |
| AU3194193A (en) | 1993-07-29 |
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| EEER | Examination request | ||
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19991207 |