CA2007902A1 - Process for the thermal decomposition of metal sulphates - Google Patents
Process for the thermal decomposition of metal sulphatesInfo
- Publication number
- CA2007902A1 CA2007902A1 CA002007902A CA2007902A CA2007902A1 CA 2007902 A1 CA2007902 A1 CA 2007902A1 CA 002007902 A CA002007902 A CA 002007902A CA 2007902 A CA2007902 A CA 2007902A CA 2007902 A1 CA2007902 A1 CA 2007902A1
- Authority
- CA
- Canada
- Prior art keywords
- roasting residue
- roasting
- residue
- metal
- thermal decomposition
- 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.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/48—Sulfur dioxide; Sulfurous acid
- C01B17/50—Preparation of sulfur dioxide
- C01B17/501—Preparation of sulfur dioxide by reduction of sulfur compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/48—Sulfur dioxide; Sulfurous acid
- C01B17/50—Preparation of sulfur dioxide
- C01B17/501—Preparation of sulfur dioxide by reduction of sulfur compounds
- C01B17/507—Preparation of sulfur dioxide by reduction of sulfur compounds of iron sulfates
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Fluidized-Bed Combustion And Resonant Combustion (AREA)
- Processing Of Solid Wastes (AREA)
- Catalysts (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
Process for the Thermal Decomposition of Metal Sulphates SO2-containing ABSTRACT OF THE DISCLOSURE
A process for the thermal decomposition of metal sulphate mixtures at temperatures from 800 to 1100°C under oxidizing conditions, in which the metal sulphate mixtures are mixed with roasting residue and reacted together with fuels in the decomposition reactor to form roasting residue and SO2-containing gases from roasting wherein the roasting residue admixed with the sulphate mixture is the finely divided fraction of the resulting roasting residue which is separated from the stream of gas in an electrostatic gas purification apparatus and returned to the decomposition reactor.
This procedure has an advantageous influence on the formation of coarse roasting residue and also significantly reduces the proportion of undecomposed, water soluble sulphates in the roasting residue.
Le A 26 535
A process for the thermal decomposition of metal sulphate mixtures at temperatures from 800 to 1100°C under oxidizing conditions, in which the metal sulphate mixtures are mixed with roasting residue and reacted together with fuels in the decomposition reactor to form roasting residue and SO2-containing gases from roasting wherein the roasting residue admixed with the sulphate mixture is the finely divided fraction of the resulting roasting residue which is separated from the stream of gas in an electrostatic gas purification apparatus and returned to the decomposition reactor.
This procedure has an advantageous influence on the formation of coarse roasting residue and also significantly reduces the proportion of undecomposed, water soluble sulphates in the roasting residue.
Le A 26 535
Description
200~790Z
Process for the Thermal Decomposition of Metal Sulphates This invention relates to a process for the thermal decomposition of metal sulphate mixtures at temperatures from 800 to 1100C under oxidizing conditions, in which the metal sulphate mix~ur~s are mixed wi~h ~he finely divided frac~ion of ~he roas~ing residue and reac~ed with fuels in ~he decomposi~iDn reactor ~o form rossting residue and roas~er gases con~aining SO2.
Metal sulphates, in particular metal sulphate mixtures containing sulphuric acid, are obtained as re~i~ues fro~
~ariouE ~rocesses. There ls no worthwh~le ufie for these metal sulphate mixtures, especially ~hose containlna malnly lron sulphate ~hlC~h are left over from the recovery o~ ~he sulphuric cid from ~ho wac~e acid formed in ~he produc~ion Or Tio2 by ~ho culpha~- procoss.
The only environmentally acceptable method hitherto available for disposing of these inevitable by-products is their thermal decomposition to SO2, 2 and metal oxides ~herein-after referred to as roasting residue) at temperatures from 800 to 1100C (Ullmanns Encyclopadie der technischen Chemie, 4th Edition, Volume 18, pages 579 to 580, Verlag Chemie, Weinheim, 1978) but the presence of magnesium sulphate has a deleterious effect because sufficiently rapid decomposition Le A 26 535 - 1 -200~902 of this sulphate can only be achieved under reducing conditions within the temperature range employed industrially.
The reducing conditions proposed in DE-A 1 173 074 are, however, virtually impossible to realise in fluidized bed reactors which are advantageously used for this process.
The metal sulphates are generally introduced into the fluidized bed reactor together with the fuels required for the highly endothermic decomposition reaction. Sufficient air or air/oxygen mixture is blown through a stationary fluidized bed of coarse roasting residue from below to ensure that the gases leaving the reactor at the top have a small oxygen content in the region of 0-5 to 2 volumes%.
Under reducing conditions, these gases contain elementary sulphur, whereas at higher oxygen contents they contain significant quantities of SO3; both these are undesirable.
~nder normal conditions, the gases contain almost the whole roasting residue as dust in addition to SO2, 2~ H2O, N2 and in some cases CO2.
The gases are normally cooled from 800-1100C to 300-350C
in a waste heat boiler, a significant proport~o~ ~' the roasting residuo separatlng off under thcse conditioos. The more finely divided comyonents of roasting residue are removed from the stre~m Or gas in ~,r e~ectrostatic gas purifica~ion ~pparatu~ ~EGR ~ Elektrostati-che Gasreini-~un~sanlag-) before the stream of gas ic wet cleaned.
It is an object of this invention to provide a process which does not have the disadvantages described above.
It has now been found that the decompositlon reaction in the fluidized bed reactor is advantageously influenced by mixing the metal sulphates with finely divided roasting residue from the olectrostatic g-s purifica~ion apparatus, Th- proc--5 according to tho inv-ntion pro-mot-s the formation of coarse rossting re~idue which is important for maintsining the ctation~ry fluidized bed.
~e A 26 535 - 2 -20~7902 This invention therefore relates to a process for the thermal decomposition of metal sulphate mixtures at temperatures from 800 to 1100C under oxidizing conditions, in which the metal sulphate mixtures are mixed with roasting residue and reacted together with fuels in the decomposition reactor to form roasting residue and So2-containing qases from roasting, and the finely divided fraction of the resulting roasting r~sidue i5 sepsrated from ~he s~ream of gas in an ele~tro~atic gas purific~ion apparatuc and re~urned to t~e decomposition resc~or.
The invention not only has an advantageous influence on the formation of coarse roasting residue but also significantly reduces the proportion of undecomposed, water soluble sulphates in the roasting residue.
The proportion of water soluble metal sulphates in the roasting residue can be substantially reduced by means of the process according to the invention. In a preferred embodiment of the process according to the invention, the fuels and the finely divided roasting residue are mixed together before being fed into the decomposition reactor.
It is particularly advantageous to employ this process if the metal sulphates are compacted, e.g. pe)letize~,, together with the fuels and finely dlvlded roaeting residue ~efore ~o the thermal decomposition. The fuels used in the context of this invention may be not only coal, tar, molasses, etc.
but also pyrites or sulphur.
In one particularly preferred embodlment, the meta1 sulphate ~5 mixtures contain culphurlc acld at a concentratlon of S to 96~ by welght as molsture content.
The advantages of the process according to the invention are Le A 26 535 - 3 -Z01~)7902 illustrated with the aid of examples which, however, should not be regarded as limiting the invention.
LeA 26 535 -200~7902 ComD~rison ExamPle In ~h~ process of working up was~e acid resulting from tha production of Tio2 by ~he sulphate proce~s, a metal sulphat~ mixture con~aining ~ulphuric aci~ and ha~ing the following COmpOBitiOn was ~eparat~d ~all p~rcentages are perc6ntage~ by weigh~):
26~7% FeSO4-H20 6~8~ Al2(SO4)3-H2SO4~8 H20 28-7% Fe2H2tSO4)3 H2O 2-8% Fe2(SO4)3-H2sO4-8 H2O
9~1% MgSO4 H2o 0~7% VOSO4 1~8% MnSO4'H2O 0~6% Cr2(S4)3 7~3% TiOSO4 0 5% CaSO4 0~1% ~a2SO4 9~7% H2SO4 5~2% H2O
The metal sulphate mixture, coal and roasting residue were mixed in ratiosby weight of 1:0~ 3:0~1 and shaped into green pellets in accordance with D~-A 1 173 074. The roasting residue used consisted of part of the total roasting residue obtained from the thermal decomposition.
The green pellets were fed into the fluidized bed reactor from a doslng bin and reacted at 980 ~ 5C.
The roasting residue removed from the plant when a steady state had been reached had the following composition:
39~8% Fe 0~ 3% Cr 1-5% Al 0~6% Ca 3~9% Mg 0~1% Na 5~14 Ti 1~24 SlO2 1~5% Mn 8~8% S042-0~5% V 12~0% H20 ~ A 26 535 - 5 -~01~)~90Z
ExamPle A metal sulphate mixture (analogous to that of the Comparison Example) was mixed with coal and roasting residue in ratios by weight of 1:0-3:0-1 but instead of using a proportion of the total roasting residue, only the residue from the electrostatic gas purification apparatua was used. Subsequent working up and the de-composition reaction were carried out under the same conditions as in the Comparison Example.
The roasting residue which was withdrawn from the plant and not returned had the following composition:
41~1% Fe 0~34 Cr 1~64 Al 0-64 Ca 4~0% Mg 0-1% Na 5~3% Ti 1~2% SiO2 1^6% Mn 4~8% S042-0~5~ V 12~04 H2O
Process for the Thermal Decomposition of Metal Sulphates This invention relates to a process for the thermal decomposition of metal sulphate mixtures at temperatures from 800 to 1100C under oxidizing conditions, in which the metal sulphate mix~ur~s are mixed wi~h ~he finely divided frac~ion of ~he roas~ing residue and reac~ed with fuels in ~he decomposi~iDn reactor ~o form rossting residue and roas~er gases con~aining SO2.
Metal sulphates, in particular metal sulphate mixtures containing sulphuric acid, are obtained as re~i~ues fro~
~ariouE ~rocesses. There ls no worthwh~le ufie for these metal sulphate mixtures, especially ~hose containlna malnly lron sulphate ~hlC~h are left over from the recovery o~ ~he sulphuric cid from ~ho wac~e acid formed in ~he produc~ion Or Tio2 by ~ho culpha~- procoss.
The only environmentally acceptable method hitherto available for disposing of these inevitable by-products is their thermal decomposition to SO2, 2 and metal oxides ~herein-after referred to as roasting residue) at temperatures from 800 to 1100C (Ullmanns Encyclopadie der technischen Chemie, 4th Edition, Volume 18, pages 579 to 580, Verlag Chemie, Weinheim, 1978) but the presence of magnesium sulphate has a deleterious effect because sufficiently rapid decomposition Le A 26 535 - 1 -200~902 of this sulphate can only be achieved under reducing conditions within the temperature range employed industrially.
The reducing conditions proposed in DE-A 1 173 074 are, however, virtually impossible to realise in fluidized bed reactors which are advantageously used for this process.
The metal sulphates are generally introduced into the fluidized bed reactor together with the fuels required for the highly endothermic decomposition reaction. Sufficient air or air/oxygen mixture is blown through a stationary fluidized bed of coarse roasting residue from below to ensure that the gases leaving the reactor at the top have a small oxygen content in the region of 0-5 to 2 volumes%.
Under reducing conditions, these gases contain elementary sulphur, whereas at higher oxygen contents they contain significant quantities of SO3; both these are undesirable.
~nder normal conditions, the gases contain almost the whole roasting residue as dust in addition to SO2, 2~ H2O, N2 and in some cases CO2.
The gases are normally cooled from 800-1100C to 300-350C
in a waste heat boiler, a significant proport~o~ ~' the roasting residuo separatlng off under thcse conditioos. The more finely divided comyonents of roasting residue are removed from the stre~m Or gas in ~,r e~ectrostatic gas purifica~ion ~pparatu~ ~EGR ~ Elektrostati-che Gasreini-~un~sanlag-) before the stream of gas ic wet cleaned.
It is an object of this invention to provide a process which does not have the disadvantages described above.
It has now been found that the decompositlon reaction in the fluidized bed reactor is advantageously influenced by mixing the metal sulphates with finely divided roasting residue from the olectrostatic g-s purifica~ion apparatus, Th- proc--5 according to tho inv-ntion pro-mot-s the formation of coarse rossting re~idue which is important for maintsining the ctation~ry fluidized bed.
~e A 26 535 - 2 -20~7902 This invention therefore relates to a process for the thermal decomposition of metal sulphate mixtures at temperatures from 800 to 1100C under oxidizing conditions, in which the metal sulphate mixtures are mixed with roasting residue and reacted together with fuels in the decomposition reactor to form roasting residue and So2-containing qases from roasting, and the finely divided fraction of the resulting roasting r~sidue i5 sepsrated from ~he s~ream of gas in an ele~tro~atic gas purific~ion apparatuc and re~urned to t~e decomposition resc~or.
The invention not only has an advantageous influence on the formation of coarse roasting residue but also significantly reduces the proportion of undecomposed, water soluble sulphates in the roasting residue.
The proportion of water soluble metal sulphates in the roasting residue can be substantially reduced by means of the process according to the invention. In a preferred embodiment of the process according to the invention, the fuels and the finely divided roasting residue are mixed together before being fed into the decomposition reactor.
It is particularly advantageous to employ this process if the metal sulphates are compacted, e.g. pe)letize~,, together with the fuels and finely dlvlded roaeting residue ~efore ~o the thermal decomposition. The fuels used in the context of this invention may be not only coal, tar, molasses, etc.
but also pyrites or sulphur.
In one particularly preferred embodlment, the meta1 sulphate ~5 mixtures contain culphurlc acld at a concentratlon of S to 96~ by welght as molsture content.
The advantages of the process according to the invention are Le A 26 535 - 3 -Z01~)7902 illustrated with the aid of examples which, however, should not be regarded as limiting the invention.
LeA 26 535 -200~7902 ComD~rison ExamPle In ~h~ process of working up was~e acid resulting from tha production of Tio2 by ~he sulphate proce~s, a metal sulphat~ mixture con~aining ~ulphuric aci~ and ha~ing the following COmpOBitiOn was ~eparat~d ~all p~rcentages are perc6ntage~ by weigh~):
26~7% FeSO4-H20 6~8~ Al2(SO4)3-H2SO4~8 H20 28-7% Fe2H2tSO4)3 H2O 2-8% Fe2(SO4)3-H2sO4-8 H2O
9~1% MgSO4 H2o 0~7% VOSO4 1~8% MnSO4'H2O 0~6% Cr2(S4)3 7~3% TiOSO4 0 5% CaSO4 0~1% ~a2SO4 9~7% H2SO4 5~2% H2O
The metal sulphate mixture, coal and roasting residue were mixed in ratiosby weight of 1:0~ 3:0~1 and shaped into green pellets in accordance with D~-A 1 173 074. The roasting residue used consisted of part of the total roasting residue obtained from the thermal decomposition.
The green pellets were fed into the fluidized bed reactor from a doslng bin and reacted at 980 ~ 5C.
The roasting residue removed from the plant when a steady state had been reached had the following composition:
39~8% Fe 0~ 3% Cr 1-5% Al 0~6% Ca 3~9% Mg 0~1% Na 5~14 Ti 1~24 SlO2 1~5% Mn 8~8% S042-0~5% V 12~0% H20 ~ A 26 535 - 5 -~01~)~90Z
ExamPle A metal sulphate mixture (analogous to that of the Comparison Example) was mixed with coal and roasting residue in ratios by weight of 1:0-3:0-1 but instead of using a proportion of the total roasting residue, only the residue from the electrostatic gas purification apparatua was used. Subsequent working up and the de-composition reaction were carried out under the same conditions as in the Comparison Example.
The roasting residue which was withdrawn from the plant and not returned had the following composition:
41~1% Fe 0~34 Cr 1~64 Al 0-64 Ca 4~0% Mg 0-1% Na 5~3% Ti 1~2% SiO2 1^6% Mn 4~8% S042-0~5~ V 12~04 H2O
Claims (4)
1. In a process for the thermal decomposition of metal sulphate mixtures at temperatures from 800 to 1100°C under oxidizing conditions, comprising mixing the metal sulphate mixtures with roasting residue and reacting together with fuels in a decomposition reactor to form roasting residue and SO2-containing roaster gases, the improvement comprising separating off the finely divided fraction of the resulting roasting residue in an electrostatic gas purification apparatus and returning the finely divided fraction to the decomposition reactor.
2. A process according to Claim 1, comprising mixing together the metal sulphate mixture, the fuels and the finely divided roasting residue before feeding into the decomposition reactor.
3. A process according to Claim 2, comprising compacting the mixture before its introduction into the decomposition reactor.
4. A process according to Claim 1, wherein the metal sulphate mixtures contain sulphuric acid at a concentration of 5 to 96% by weight H2SO4 as moisture.
Le A 26 535 - 7 -
Le A 26 535 - 7 -
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3901459A DE3901459A1 (en) | 1989-01-19 | 1989-01-19 | METHOD FOR THE THERMAL DECOMPOSITION OF METAL SULFATES |
| DEP3901459.2 | 1989-01-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2007902A1 true CA2007902A1 (en) | 1990-07-19 |
Family
ID=6372379
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002007902A Abandoned CA2007902A1 (en) | 1989-01-19 | 1990-01-17 | Process for the thermal decomposition of metal sulphates |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP0379016B1 (en) |
| JP (1) | JPH02233507A (en) |
| CA (1) | CA2007902A1 (en) |
| DE (2) | DE3901459A1 (en) |
| ES (1) | ES2055169T3 (en) |
| FI (1) | FI92046C (en) |
| NO (1) | NO301321B1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19506252A1 (en) * | 1995-02-23 | 1996-09-19 | Bayer Ag | Prodn. of magnesium sulphate-contg. metal oxide mixt. useful as fertiliser |
| DE19512614C2 (en) * | 1995-04-05 | 1998-05-20 | Bayer Ag | Use of solutions containing magnesium sulfate as fertilizer |
| DE19513511C2 (en) * | 1995-04-10 | 1998-04-30 | Bayer Ag | Process for the production of a lime-magnesium mixture for sustainable soil improvement |
| DE19623408C1 (en) * | 1996-06-12 | 1998-02-12 | Bayer Ag | Production of coarse grained metal oxide(s) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL273476A (en) * | 1961-01-26 | 1900-01-01 |
-
1989
- 1989-01-19 DE DE3901459A patent/DE3901459A1/en not_active Withdrawn
-
1990
- 1990-01-06 DE DE9090100248T patent/DE59001379D1/en not_active Expired - Fee Related
- 1990-01-06 ES ES90100248T patent/ES2055169T3/en not_active Expired - Lifetime
- 1990-01-06 EP EP90100248A patent/EP0379016B1/en not_active Expired - Lifetime
- 1990-01-08 NO NO900069A patent/NO301321B1/en unknown
- 1990-01-16 JP JP2004639A patent/JPH02233507A/en active Pending
- 1990-01-17 CA CA002007902A patent/CA2007902A1/en not_active Abandoned
- 1990-01-17 FI FI900264A patent/FI92046C/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| FI900264A0 (en) | 1990-01-17 |
| EP0379016A1 (en) | 1990-07-25 |
| NO301321B1 (en) | 1997-10-13 |
| EP0379016B1 (en) | 1993-05-12 |
| ES2055169T3 (en) | 1994-08-16 |
| FI92046B (en) | 1994-06-15 |
| DE3901459A1 (en) | 1990-07-26 |
| NO900069D0 (en) | 1990-01-08 |
| JPH02233507A (en) | 1990-09-17 |
| NO900069L (en) | 1990-07-20 |
| DE59001379D1 (en) | 1993-06-17 |
| FI92046C (en) | 1994-09-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |