AU626657B2 - A process for the production of titanium dioxide - Google Patents
A process for the production of titanium dioxide Download PDFInfo
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- AU626657B2 AU626657B2 AU53165/90A AU5316590A AU626657B2 AU 626657 B2 AU626657 B2 AU 626657B2 AU 53165/90 A AU53165/90 A AU 53165/90A AU 5316590 A AU5316590 A AU 5316590A AU 626657 B2 AU626657 B2 AU 626657B2
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- Prior art keywords
- fraction
- hydrolyzate
- hydrolysis
- weight
- washing
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-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/04—Oxides; Hydroxides
- C01G23/047—Titanium dioxide
- C01G23/053—Producing by wet processes, e.g. hydrolysing titanium salts
- C01G23/0532—Producing by wet processes, e.g. hydrolysing titanium salts by hydrolysing sulfate-containing salts
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
Description
i i Il--i Our Ref: 316420 626657
AUSTRALIA
Patents Act COMPLETE SPECIFICATION FORM
(ORIGINAL)
Application Number: Lodged: Complete Specification Lodged: Accepted: Published: 9 0 4 4
S
4* 4
S
4P Priority: Related Art: Applicant(s): BAYER AKTIENGESELLSCHAFT D-5090 Leverkusen, Bayerwerk, Germany o ot 1 Address for Service: ARTHUR S. CAVE CO.
Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 L Complete specification for the invention entitled "A process for the production of titanium dioxide".
The following statement is a full description of this invention, including the best method of performing it known to me:- 1 2061U/gs t A PROCESS FOR THE PRODUCTION OF TITANIUM DIOXIDE o oo *n 0 0 #000 4s~ 0004 00 a* 0 00~sol *i 0n This invention relates to a process for the production of titanium dioxide by the sulfate process, in which the liquid accumulating during washing of the hydrolyzate is fractionated and the dilute fractions are returned to the process while the relatively concentrated waste acid is fed to a recycling process.
It is known that, apart from raw material and process costs, the economy of titanium dioxide production 15 is being increasingly influenced by the costs involved in treatment of the waste acid and by government-imposed wastewater levies. Accordingly, various processes have already been proposed with a view to reducing treatment costs by increasing the concentration of the waste acid or by directly recycling waste acid to the process.
According to US 4,502,976, waste acid of high concentration is separated from dilute washing acid through careful monitoring of the sulfuric acid concentration in the liquid accumulating during washing of the hydro- 25 lyzate. This dilute washing acid may advantageously be concentrated, optionally in part, by waste heat in a first evaporation stage, According to DE-C 2,729,755, ilmenite is digested with a mixture of 62 to 75% sulfuric acid, recovered by concentration of waste acid by evaporation and separation of the metal sulfates, and at least 95% pure sulfuric acid and the digestion cake is dissolved with water and part of the waste acid formed during the 0000 O 0 0 4 0400 0 u 0904 a 0 0 t 0 f* 0 a 000400 0 0
S
Le A 26 808 lahydrolysis of titanyl sulfate, However, this process is Sspecially designed for the use of ilmenite as raw material, in addition to which narrow limits are imposed by the metal sulfates, particularly chromium sulfate, recycled with the waste acid, Another maj~or disadvantage of this process is that the TiO 2 production process is seriously impaired by the very high proportion of waste acid (20 to 30%A) used to dissolve the digestion cake. If the quantity of sulfuric a acid used to digest the raw material is correspondingly reduced, a lower yield of TiOSO 4 is obtained when the autothermal discontinuous digestion reaction is carried out on an industrial scale, If, on the other hand, the 4,4 H2* HSC 4 TiO 2 ratio is kept constant during the digestion reaction, such a high H 2 S0 4 ;Ti0-2 ratio is obtained in the titanyl sulfate solution through the waste acid used to dissolve the digestion cake that the hydrolysis yield and the TiO2 pigment properties are adversely affected, Accordingly, the problem addressed by the present invention was to provide a process by which it would be possible, both with ilmenite and with titanium slag as raw material, to obtain a maximal proportion of the sulfuric acid used to digest the titanium raw material as highly concentrated waste acid from the process, 0 thereby minimizing both treatment costs and wastewater pollution, without adversely affecting the process as a whole or the quality of the titanium dioxide pigmant.
The present invention relates to a process for the production of titanium dioxide by digestion of titanium raw materials with sulfuric acid, dissolution of the Le A 26 808 -2-
C_
UI,.
0 ftq oo 00 0 00 0 0 00 0 0 0t 0 0 CO 00 0 0000 0 0 0000 0 08* 04 1 o 0 0 00 004044 0 digested material to form a titanyl sulfate solution, hydrolysis of the titanyl sulfate, separation of the hydrolyzate from the metal-sulfate-containing sulfuric acid, the so-called waste acid, washing of the hydrolyzate and calcination to the TiO 2 pigment, the solution accumulating during separation of the solids from the suspension formed during hydrolysis of the titanyl sulfate being fed entirely as waste acid to a treatment or recycling process and the liquid accumulating during washing of the hydrolyzate being divided into three or four fractions of decreasing sulfuric acid concentra- 15 tion, the first fraction A accumulating being combined with the waste acid and fed to the treatment or recycling process, the second fraction B accumulating thereafter being used instead of water in the hydrolysis of the titanyl sulfate, the third fraction C being used to dissolve the digested material formed during digestion of the titanium raw material and, optionally, a fourth fraction D being used instead of water to wash the hydrolyzate or being removed as wastewater, In a particularly preferred embodiment of the process, the waste acid fed to the treatment or recycling process has a concentration of at least 23% by weight
H
2
SO
4 and preferably of at least 24% by weight H 2
SO
4 The fraction B returned to hydrolysis of the titanyl sulfate from washing of the hydrolyzate preferably contains 7 to 23% by weight H 2 S0 4 and the fraction C used to dissolve the digested material 0.2 to 7% by weight H 2
SO
4 In one preferred embodiment of the process, hydrolysis of the titanyl sulfate is carried out using separately Le A 26 808 3 a- 0240s:AB -4produced hydrolysis nuclei and fraction B is only added after at least 50% of the total duration of the hydrolyis process has elapsed.
Accordingly, the liquid accumulating during washing of the hydrolyzate is divided up into three or, optionally, four fractions according to the sulfuric acid concentration.
These fractions are then specifically returned to the process or are removed.
More particularly, the process comprises the following steps: Titanium raw materials, particularly ilmenite or titanium slag, are digested in known manner with 80 to sulfuric acid. The sulfuric acid used is preferably a mixture of at least 95% sulfuric acid, or more specifically of oleum (ie the solution of sulfur trioxide in concentrated sulfuric acid commercially known by that name), together with at least 60% sulfuric acid recovered by concentration of waste acid from the sulfate process by evaporation and separation of the metal sulfates from the sulfuric acid.
o. Alternatively, sulfuric acid recovered from waste acid by S other recycling processes may also be used.
According to the invention, the preferably solid digested material which accumulates during digestion of the raw materials is dissolved with the third fraction C of the solution accumulating during washing of the hydrolyzate.
The fraction in question has an H 2 S0 4 content of 0.2 to 7% by weight. Water or other solutions containing sulfuric ~acid may be used together with fraction C.
The low concentration of fraction C rules out any adverse effect on the subsequent hydrolysis process or on the pigment quality.
Solids and, optionally, iron sulfate heptahydrate are separated off in known manner from the titanyl sulfate solution obtained.
Ah Subsequent hydrolysis of the titanyl sulfate is carried out, for example, using separately produced hydrolysis nuclei, fraction B accumulating during washing of the hydrolyzate being added to the solution, Fraction B is preferably added after at least 50% of the total duration of the hydrolysis process has elapsed.
The quantity of fraction B is gauged in such a way that the suspension contains 160 to 200 g (Ti02/1 at the end of the hydrolysis process. The addition of fraction B containing 7 to 23% by weight H 2
SO
4 in accordance with 's the invention does not adversely affect pigment quality.
0409 o 15 However, the concentration of the waste acid is 04 00 a distinctly increased in relation to the concentration a0 obtained where water is added in accordance with the 4, .0 prior art.
The hydrolyzate is separated, optionally by filtration, from the mother liquor, the waste acid containing
H
2
SO
4 and metal sulfates, and subsequently washed with ooo0 water, The concentration of H 2 S0 4 and metal sulfates of 0040 06 the solution, which accumulates during this washing of the hydrolyzate, changes characteristically during the 25 washing process, Initially, waste acid is displaced from the hydrolyzate by the washing water, The sulfuric acid concentration then falls slowly from the range of 24-27% 0 0 by weight to values of 18 to 23% by weight, According 006 to the invention, this concentrated solution is fed as the first fraction A to the waste acid until the H 2
SO
4 concentration of the solution flowing off has fallen to a value in the range of 24-15% by weight, The waste acid thus obtained contains 85 to 97% of the sulfate ions Le A 26 808 rjzi~.
I
o o* 99 9 99 990*99 o *9 94 o 0 9 9 9 94 04 4 949 4 9904 9 9 9000 4004 94 90 4 *099 0994 4 o 944 9 9 4 940004 o 4 contained in the titanyl sulfate solution after separation of iron sulfate heptahydrate, corresponding to 93% of the sulfuric acid present in the suspension after hydrolysis of the titanyl sulfate, A fraction B is then separated off while the H 2 S0 4 concentration falls rapidly from 25-15 to 12-3% by weight. According to the invention, this fraction B with an average H 2 S0 4 content of 10-23% by weight contains 4-12% of the sulfuric a~rid present after hydrolysis and, as described above, is added during hydrolysis of the titanyl sulfate, The relatively highly dilute solution accumulating after the 15 steep fall in concentration to less than 12% by weight
H
2
SO
4 is separated as the third fraction C, According to the invention, this fraction C with, on average, 0,2- 7% by weight H 2 S0 4 contains 1 to 5% of the sulfuric acid present after hydrolysis and is used to dissolve the digested material, A highly dilute fourth fraction D is optionally used instead of water to wash the hydrolyzate or is removed as wastewater, According to the invention, it contains less than 5% and preferably less than 1% of the sulfuric acid present after hydrolysis, 25 Whereas, according to DE-C-2 729 755, it is only possible to obtain a waste acid concentration of 21-23% by weight H 2 S0 4 and problems can be expected from the metal ions relevant to color of the pigment, particularly Cr or V ions, present in the recycled solutions, it has surprisingly been found that neither the titanium dioxide production process itself nor the quality of the pigment obtained is adversely affected by application of the process according to the invention, A major Le A 26 8-08 -6 0240s:AB 7 advantage of the invention is that it gives a waste acid of high concentration both where ilmenite and where titanium slag is used as the raw material and, at the same time, minimizes wastewater pollution. The waste acid concentration obtained, which is at least 23% by weight
H
2
SO
4 and preferably 24-27% by weight H 2 S0 4 enables the cost of treatment by recycling to be distinctly reduced compared with the prior art.
The advantageSof the process according to the invention are illustrated by the following Examples.
Example 1 1,170 kg titanium slag containing 75% by weight TiO 2 and 405 kg ilmenite containing 54% by weight TiO 2 were digested with 1,996 kg 77.2% sulfuric acid and 970 kg oleum (27% SO 3 in H 2 S0 4 (The 77.2% sulfuric acid had been ,0 recovered from waste acid in accordance with US 4,502,976.
It contained 5.8% by weight metal sulfates, including 345 ppm Cr in the form of chromium sulfate and 36 ppm V in the form of vanadium sulfate). The solid reaction product formed during the digestion reaction was dissolved with S 3.4 m of the fraction C separated off during the washing of the hydrolyzate of a preceding batch and 0.9 m wash solution from the washing of the digestion residues. The ao solution was filtered and the titanyl sulfate hydrolyzed.
Hydrolysis was carried out as follows: 49 1 of a suspension of hydrolysis nuclei separately S produced a precipitation of titanyl sulfate with sodium hydroxide were added to 4.35 m titanyl sulfate solution a 0 A i (corresponding to 1 t TiOz). The mixture was brought to the boiling temperature by introduction of steam and boiled to the "match point". The introduction of steam was then interrupted for 30 minutes, after which more steam was introduced and the mixture boiled for 2.5 h. After a total process time of 2.5 h, 0.9 m 3 solution which had been separated as fraction B during washing of the hydrolyzate was added. 70 minutes after addition of the solution, the introduction of steam was stopped. The hydrolysis yield .'110 was 95.4%.
The suspension obtained was filtered, waste acid containing 26.9% by weight H 2 S0 4 accumulating as filtrate.
The filter cake was then washed with water. The solution 0 accumulating as filtrate during washing of the filter cake was divided into 4 fractions: At the beginning of the washing process, the concentration of the solution fell slowly from 26.4 to 22-23% by weight H 2 S0 4 and then rapidly to values below 5% by weight.
0The first 2.9 M 3 filtrate were separated off as fraction A until a concentration of 23% by weight H 2 S0 4 had been reached. This fraction had an average concentration of 24.6% by weight H 2 S0 4 and was combined with the waste acid which had accumulated during filtration of the hydrolyzate suspension. The waste acid fed to the recycling process had an average concentration of 25.5% by weight H 2 S0 4 345 ppm S Cr and 580 ppm V. It contained 95.2% of the sulfate ions used during digestion of the raw material. 0.9 M 3 of the J filtrate were then separated of f as fraction B while the concentration of the filtrate fell from 23 to 10.2% by weight H 2 S0 4 The fraction B had an average concentration of 19.6% by weight H 2 S0 4 265 ppm Cr and 446 ppm V. it contained 9.3% of the sulfuric acid which was present in the suspension after hydrolysis. 2.4 M 3 solution were then separated off as fraction C. This filtrate fraction had a concentration of 5.5% by weight ",SO 4 19 ppm Cr and 32 ppm Le A26 808 8 V. It contained 5.4% of the sulfuric acid present on completion of hydrolysis.
When the filtrate stream was switched over as fraction D to the wastewater channel, the f iltrate contained 3. 1% by weight H2SOA. The concentration fell to 0.3% by weight
H
2 S0 4 1.8% by weight of the sulfate ions used in the digestion of the raw material were removed.
The filter cake obtained after washing of the hydrolyzate was bleached by the addition of Al powder and sulfuric acid. The standardizing chemicals phosphoric acid, alkalis and rutile nuclei were then added to the f ilter cake, 0004.4: followed by calcination under standard conditions at 9500C o in a rotary kiln to form rutile pigment.
04 0 *The pigment thus obtained w,.as substantially identical with the typical standard of normal production where water rather than fraction B3 was added during hydrolysis and the digested material was dissolved with water.
*boo Example 2, In the digestion of the raw material, the same ore mixture as in Example I was digested with 2,055 kg 77.2% recovered sulfuric acid and 1,000 kg oleum. The digestion cake was dissolved with 3.3 M3 of the filtrate separated off as fraction C. The digestion yield was 0.3% higher than in Example 1.
woo: Hydrolysis was carried out as in Example I with addition of 0. 9 m 3 washing filtrate (fraction B) The Ihydrolysis yield was 95.7%. The suspension obtained was filtered. The waste acid accumulating had a concentration of 26.3% by weight 112504. The filter cake was then wa-shed with water and the washing filtrate separated into three fractions. Fraction A was separated of f up to a concentration of 20.5% by weight H12504. it had an average sulfuric acid content of 23.3% by weight and was combined with the waste acid which had previously accumulated. The waste acid Le__A_1 .8
I-
fed to the recycling process contained 24.7% by weight
H
2
SO
4 334 ppm Cr and 562 ppm V. It contained 97% of the i sulfate ions used in digestion of the raw material; the remaining 3% were chemically fixed to the titanium oxide S 5 hydrolyzate.
After fraction A, 0.9 m 3 filtrate were separated off as fraction B while the H 2
SO
4 concentration fell from 20.5 to 6% by weight. Fraction B contained on average 17.8% by weight HzSO4, corresponding to 9% of the total sulfuric acid present after hydrolysis.
I 3.3 m 3 filtrate having an H 2
SO
4 concentration between 6 and 0.4% by weight, average 1.7% by weight, were separ- S* ated off as fraction C. It contained 2.5% of the sulfuric 0 acid present on completion of hydrolysis.
o 44 15 The hydrolyzate was processed to rutile pigment as in Example 1. The pigment substantially corresponded to the production standard.
*00o
I
Claims (5)
1. A process for the production of titanium dioxide comprising digesting titanium raw materials with sulfuric acid, forming a titanyl sulfate solution by dissolution of the digested material, hydrolyzing the titanyl sulfate to form a suspension of hydrolyzate and metal-sulfate-containing sulfuric acid, the so-called waste acid, separating the hydrolyzate and waste acid, i o" feeding the waste acid to a treatment or recycling pro- o cess, washing the hydrolyzate and separating the washing 15 liquid accumulating during the washing of the hydro- lyzate into fractions of decreasing concentrations, and calcining the hydrolyzate to form TiO 2 pigment wherein the first fraction of the separated fractions of the washing liquid is combined with waste acid and fed to the treatment or recycling process, the second fraction is used instead of water in titanyl sulfate hydro- lyses and the third fraction is used to dissolve U4 a 4 oo' digested material from digestion of titanium raw mate- rial, 0e 40 2, A process according to claim 1, wherein a fourth fraction D separated from the washing of the hydrolyzate is used instead of water to wash hydrolyzate 0 4 or is removed as wastewater.
3. A process according to claim 1, wherein 80 to 93% of the sulfuric acid present in the suspension after hydrolysis of the titanyl sulfate is fed as waste acid Le A 26, 808 11 4 to the treatment or recycling process, 4 to 12% of the sulfuric acid is returned to hydrolysis of the titanyl sulfate and 1 to 5% of the sulfuric acid is used to dissolve the digested material.
4. A process according to claim 1, wherein 0,1 to 5% of the sulfuric acid is used to wash the hydro- lyzate or is removed as waste water. o' 54 A process according to claim 1, wherein the waste acid fed to the treatment or recycling process has SOq 15 a concentration of at least 23% by weight H 2 SO0 4 4 O 6, A process according to claim 5, wherein the waste acid fed to the treatment or recycling process has a concentration of at least 24% by weight H 2 SO 4 .44 7, A process according to claim 1, wherein the fraction B from washing of the hydrolyzate returned to the hydrolysis of titanyl sulfate contains 7 to 23% by jg. weight H 2 SO0 4 o-
8. A process according to claim 1, wherein the r fraction C used to dissolve the digested material con- Stains 0,2 to 7% by weight H 2 S0 4
9. A process according to claim 1, comprising carrying out the hydrolysis of titanyl sulfate using separately produced hydrolysis nuclei and adding fraction B after at least 50% of the total duration of the hydrolysis process has elapsed, Le A 26 808 12 Titanium dioxide produced by the process of any one of the preceding claims. DATED this 16th day of March 1992. BAYER AKTIENGESELLSCHAFT By: Its Pent Attorneys 0 DAVIES COLLISON CAVE 044 44 44 13 206 lu/go
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3912554A DE3912554C1 (en) | 1989-04-17 | 1989-04-17 | |
| DE3912554 | 1989-04-17 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| AU5316590A AU5316590A (en) | 1990-10-18 |
| AU626657B2 true AU626657B2 (en) | 1992-08-06 |
Family
ID=6378838
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU53165/90A Ceased AU626657B2 (en) | 1989-04-17 | 1990-04-11 | A process for the production of titanium dioxide |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0393430B1 (en) |
| JP (1) | JPH02293323A (en) |
| AU (1) | AU626657B2 (en) |
| BR (1) | BR9001755A (en) |
| CA (1) | CA2014485A1 (en) |
| DE (2) | DE3912554C1 (en) |
| ES (1) | ES2054134T3 (en) |
| FI (1) | FI96840C (en) |
| NO (1) | NO901505L (en) |
| ZA (1) | ZA902824B (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI89901C (en) * | 1990-10-23 | 1993-12-10 | Kemira Oy | purification method |
| BR9005862A (en) * | 1990-11-20 | 1992-06-30 | Curua Mineracao Ltda | PROCESS OF PRODUCTION OF TITANIUM DIOXIDE FROM THE ANATASIO ORE, USING FLUID DIGESTATION WITH SULFURIC ACID AND UNDER CONDITION OF MINIMUM ACID CONSUMPTION AND MINIMUM EMISSION OF POLLUTING EFFLUENTS |
| WO1993018193A1 (en) * | 1992-03-09 | 1993-09-16 | Pivot Mining Nl | Acid washing of leached solids from the beneficiation of titaniferous ores |
| ZA946864B (en) * | 1993-09-07 | 1995-09-04 | Tech Resources Pty Ltd | Upgrading titaniferous materials. |
| DE4344359C2 (en) * | 1993-12-24 | 1996-09-19 | Bayer Ag | Process for the production of titanium dioxide by the sulfate process |
| AU2002952155A0 (en) | 2002-10-18 | 2002-10-31 | Bhp Billiton Innovation Pty Ltd | Production of titania |
| AU2002952157A0 (en) | 2002-10-18 | 2002-10-31 | Bhp Billiton Innovation Pty Ltd | Production of titania |
| AU2002952158A0 (en) | 2002-10-18 | 2002-10-31 | Bhp Billiton Innovation Pty Ltd | Production of titania |
| AP2006003593A0 (en) * | 2003-10-17 | 2006-04-30 | Bhp Billiton Innovation Pty | Production of Titania. |
| JP2006103999A (en) * | 2004-10-01 | 2006-04-20 | Murata Mfg Co Ltd | Method of manufacturing titanium oxide fine particle |
| CN112624189B (en) * | 2021-01-14 | 2023-03-28 | 上海安赐环保科技股份有限公司 | Method and system for recycling waste acid and white water of titanium dioxide produced by sulfuric acid process |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0297275A1 (en) * | 1987-06-04 | 1989-01-04 | Bayer Ag | Process for producing titaniumdioxide |
| EP0313715A1 (en) * | 1987-10-26 | 1989-05-03 | KRONOS TITAN-Gesellschaft mbH | Process for treating, thereby saving energy and material, diluted acid released during the production of titanium dioxide according to the sulphate process |
| AU2577288A (en) * | 1987-11-23 | 1989-05-25 | Sulzer-Escher Wyss Ag | Method for producing titanium dioxide |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3327769A1 (en) * | 1983-08-02 | 1985-02-14 | Bayer Ag, 5090 Leverkusen | METHOD FOR THE TREATMENT OF THICK ACID |
| DE3742838A1 (en) * | 1987-12-17 | 1989-07-13 | Kronos Titan Gmbh | METHOD FOR PRODUCING TITANIUM DIOXIDE PIGMENTS |
-
1989
- 1989-04-17 DE DE3912554A patent/DE3912554C1/de not_active Expired - Lifetime
-
1990
- 1990-04-03 NO NO90901505A patent/NO901505L/en unknown
- 1990-04-05 ES ES90106528T patent/ES2054134T3/en not_active Expired - Lifetime
- 1990-04-05 EP EP90106528A patent/EP0393430B1/en not_active Expired - Lifetime
- 1990-04-05 DE DE9090106528T patent/DE59000737D1/en not_active Expired - Fee Related
- 1990-04-11 AU AU53165/90A patent/AU626657B2/en not_active Ceased
- 1990-04-12 FI FI901874A patent/FI96840C/en not_active IP Right Cessation
- 1990-04-12 CA CA002014485A patent/CA2014485A1/en not_active Abandoned
- 1990-04-12 JP JP2095242A patent/JPH02293323A/en active Pending
- 1990-04-12 ZA ZA902824A patent/ZA902824B/en unknown
- 1990-04-16 BR BR909001755A patent/BR9001755A/en not_active Application Discontinuation
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0297275A1 (en) * | 1987-06-04 | 1989-01-04 | Bayer Ag | Process for producing titaniumdioxide |
| EP0313715A1 (en) * | 1987-10-26 | 1989-05-03 | KRONOS TITAN-Gesellschaft mbH | Process for treating, thereby saving energy and material, diluted acid released during the production of titanium dioxide according to the sulphate process |
| AU2577288A (en) * | 1987-11-23 | 1989-05-25 | Sulzer-Escher Wyss Ag | Method for producing titanium dioxide |
Also Published As
| Publication number | Publication date |
|---|---|
| FI96840C (en) | 1996-09-10 |
| DE59000737D1 (en) | 1993-02-25 |
| FI96840B (en) | 1996-05-31 |
| AU5316590A (en) | 1990-10-18 |
| ZA902824B (en) | 1991-02-27 |
| BR9001755A (en) | 1991-06-04 |
| EP0393430B1 (en) | 1993-01-13 |
| DE3912554C1 (en) | 1990-07-12 |
| EP0393430A2 (en) | 1990-10-24 |
| NO901505D0 (en) | 1990-04-03 |
| ES2054134T3 (en) | 1994-08-01 |
| NO901505L (en) | 1990-10-18 |
| EP0393430A3 (en) | 1991-03-27 |
| JPH02293323A (en) | 1990-12-04 |
| CA2014485A1 (en) | 1990-10-17 |
| FI901874A0 (en) | 1990-04-12 |
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