CA2014485A1 - Process for the production of titanium dioxide - Google Patents
Process for the production of titanium dioxideInfo
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- CA2014485A1 CA2014485A1 CA002014485A CA2014485A CA2014485A1 CA 2014485 A1 CA2014485 A1 CA 2014485A1 CA 002014485 A CA002014485 A CA 002014485A CA 2014485 A CA2014485 A CA 2014485A CA 2014485 A1 CA2014485 A1 CA 2014485A1
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- hydrolysis
- hydrolyzate
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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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Abstract
A PROCESS FOR THE PRODUCTION OF TITANIUM DIOXIDE
Abstract of the Disclosure A process for the production of titanium dioxide by the sulfate process in which the liquid accumulating during washing of the titanyl sulfate hydrolysis hydro-lyzate is fractionated and the dilute fractions are returned to the process while the relatively concen-trated thin acid is fed to a waste disposal.
Le A 26 808
Abstract of the Disclosure A process for the production of titanium dioxide by the sulfate process in which the liquid accumulating during washing of the titanyl sulfate hydrolysis hydro-lyzate is fractionated and the dilute fractions are returned to the process while the relatively concen-trated thin acid is fed to a waste disposal.
Le A 26 808
Description
2!~ 4~
A PROCESS FOR THE PRODUCTION OF TITANIUM DIOXIDE
This invention relates to a process for the pro-duction 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 concen-trated waste acid is fed to a recycling process.
It is known that, apart from raw material and pro-cess cos~s, the economy of titanium dioxide production 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, a waste acid of high concen-tration is separated from dilute washing acid through careful monitoring of the sulfuric acid concentration in the liquid accumulating during washing of the hydro-lyzate. This dilute washing acid may advantageously beconcentrated, 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 separa-tion of the metal sulfa~es, and at least 95% pure sul-furic acid and the digestion cake is dissolved with water and part of the waste acid formed during the Le A 26 808 26~ 35 hydrolysi 5 0 f titanyl sulfate. However, thi 5 process is S specially designed for the use of ilmeni~e as raw mate-rial, in addition to which narrow limits are imposed by the metal sulfates, particularly chromium sulfate, re-cycled with the waste acid.
Another major disadvantage of this process is that the TiO2 production process is seriously impaired by the very high proportion of waste acid ~20 to 30~ used to dissolve the digestion cake. If the quantity of sulfuric acid used to digest the raw material is correspondingly reduced, a lower yield of Tioso4 is obtained when the autothermal discontinuous digestion reaction is carried out on an industrial scale. ~f, on the Gther hand, the H2S04:Tio2 ratio is kept constant during the digestion reaction, such a high H2SO~:TiO2 ratio is obtained in the titanyl sulfate solution through the waste acid used to dissolve the digestion cake that the hydrolysis yield ard 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, thereby minimizing both treatment costs and wastewater pollution, without adversely affecting the proces~ as 30 B whole or the quality of the titanium dioxide pigment.
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 80~
2~
digested material to form a titanyl sulfate solution, S hydrolysis of the titanyl sulfate, separation of the hydrolyzate from the metal-sulfate-containing sulfuric acid, the so-called waste acid, washing of the hydroly-zate and calcination to the TiO2 pigment, the solution accumulating during separation of the solids from the suspension formed during hydrolysis of the titanyl sul-fate being fed ent;rely as waste acid to a treatment orrecycling process and the liquid accumulating during washing of the hydrolyzate being divided into three or four fractions of decreasing sulfuric acid concentra-tion, the first fraction A accumulating being combined with the waste acid and fed to the treatment or re-cycling 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 di-gestion 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 pro-: 25 cess, the waste acid fed to the treatment or recycling process has a concentration of at least 23% by weight : H2S04 and preferably of at least 24X by weight H2S04 The fraction B returned to hydrolysis of the titanyl sulfate from washing of the hydrolyzate preferably contains 7 to 23% by weight H2SO~ and the fraction C used to dissolve the digested material 0.2 to 7% by weight H2SO4.
In one preferred embodiment of the process, hydrolysis of the titanyl sulfate is carried out using separately Le A 26 808 2~44~35 produced hydrolysis nuclei and fraction B is only added after at least 50% of the total duration of the hydrolysis 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 concentra-tion. These fractions are then specifically returned to the process or are removed.
More particularly, the process comprises the followingsteps:
Titanium raw materials, particularly ilmenite or titanium slag, are disgested in known manner with 80 to 95%
sulfuric acid. The sulfuric acid used is preferably a mixture of at least 95% sulfuric acid or oleum and at least 60% sulfuric acid recovered by concen~ration of wss~e acid from the sulfate process by evaporation and sepa-ration of ~he metal sulfates from the sulfuric acid.
Alterna~ively, sulfuric acid recovered from waste acid by other recycling processes may also be used.
According to the invention, the preferably solid digested material which accumulates during digestion of the raw material is dissolved with the third fraction C of the solution accumulating during washing of the hydrolyzate.
The fraction in guestion has an H2S0~ 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 ~5 solution obtained.
Le A 26 808 2at~44~3s 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 dura~ion 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 (TiO211 at the end of the hydrolysis process. The addition of fraction B
containing 7 to 23% by weight H2S04 in accordance with the invention does not adversely affect pigment quality.
However, the concentration of the waste acid is distinctly increased in relation to the concentration obtained where water is added in accordance with the prior art.
The hydroly7ate is separated, optionally by filtra-tion, from the mother liquor, the waste acid containing H2S04 and metal sulfates, and subsequently washed with water, The concentration of H2S04 and metal sulfates of the solution, which accumulates during this washing of the hydrolyzate, changes characteristically during the washing process. Ini~ially, waste acid is displaced from the hydrolyzate by the washing water. The sulfuric acid concentration then falls slowly from the range of 24-27%
by weight to values of 18 to 23% by weight, According to the invention, this concentrated solution i5 fed as the first fraction A to the waste acid until the H2S04 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 2Q~4~35 contained in the titanyl sulfate solution after separa-tion of iron sulfate heptahydrate, corresponding to 80-93% of the sulfuric acid present in the suspension after hydrolysis of the titanyl sulfate. A fraction B is then separated off while the H2S04 concentration falls rapid-ly from 25-15 to 12-3K by weight. According to the invention, this fraction B with an average H2S04 content of 10-23% by weight contains 4-12X of the sulfuric acid present after hydrolysis and, as described above, is added during hydrolysis of the titanyI sulfate. The relatively highly dilute solution accumulating after the steep fall in concentration to l-ss than 12% by weight H2S04 is separated as the third fraction C. According to the invention, this fraction C with, on average, 0.2-7X by weight H2S04 contains 1 to SX 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 SX 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 21-2~X
by weight H2S04 and problems can be expected from the metal ions relevant to color of the pigment, particular-ly Cr or V ions, present in the recycled solutions, it has surprisingly been found that neither th- titanium d;oxide production proce-s its-lf nor the quality of the pigment obtained is ad~ersely affected by application of the process according to the invention. A major Le A 26 808 ;
'~ ,' ' 4~85 advan~age of ~he i~vention is t~a~ it gives a was~e acid of high concen~ra~ion bo~h where ilmenite and where ti~anium slag is used as the raw ma~erial and, at the same ~ime, minimizes wastewater pollu~ion. The was~e acid concen~ration obtained, which is at least 2~% by weight H2504 and preferably 24-27% by weight H2S04, enables the cost of treatment by recy~ling to be distinctly reduced c~mpared wi~h the prior art.
The advantages of th~ process according ~o ~he in~ention are illustrated by the following Examples.
Example 1 1,170 kg titanium slag containing 75~ by weight Tio2 and 405 kg ilmenite containing 54~ by weight Tio2 were digested with 1,996 kg 77.2% sulfuric acid and 970 kg 27%
oleum. (The 77.2% sulfuric acid had been recovered from waste acid in accordance with US 4,502,976. It contai~ed 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 3.4 m3 of the fraction C separated off during the washing of the hydrolyzate of a preceding batch and C.9 m3 wash solution from the washing of the digestion residues. The solution was filtered and the titanyl sulfate hydrolyzed.
Hydrolysis was carried out as follows:
49 l of a suspension of hydrolysis nuclei separately produced by precipitation of titanyl sulfate with sodium hydroxide were added to 4.35 m3 titanyl sulfate solution ~5 Le A 26 808 2~ 4RS
(corresponding to 1 t Tio2)~ The mixture was brought to the boiling temperature by introduction of steam and boiled to the Nmatch 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 m3 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 was 95.4%.
The suspension obtained was filtered, waste acid containing 26.9% by weight H2S04 accumulating as filtrate.
The filter cake was then washed with water. The solution accumulating as filtrate during washing of the filter cake was divided into 4 fractions:
At the beginning of the washing process, the concen-tration of the solution fell slowly from 26.4 to 22-23% by weight H2S04 and then rapidly to values below 5% by weight.
The first 2.9 m3 filtrate were separated off as fraction A
until a concentration of 23% by weight H2S04 had been reached. This fraction had an average ccncentration of 24.6% by weight H2S04 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 H2S0;, 345 ppm Cr and 580 ppm V. It contained 95.2% of the sulfate ions used during digestion of the raw material. 0.9 m3 of the filtrate were then separated off as fraction B while the concentration of the filtrate fell from 23 to 10.2% by weight H2S04. The fraction B had an average concentration of 19.6% by weight H2S04, 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 m3 solution were then separated off as fraction C. This filtrate fraction had a concentration of 5.5% by weight H2S04, 19 ppm Cr and 32 ppm Le A 26 808 8 ~44~35 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 filtrate contained 3.1% by weight H2S0~. The concentration fell to 0.3% by weight H2S0~. 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 hydroly-zate 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 filter cake, followed by calcination under standard conditions at 950C
in a rotary kiln to form rutile pigment.
The pigment thus obtained was substantially identical with the typical standard of normal production where water rather than fraction B was added during hydrolysis and the digested material was dissolved with water.
Example 2 In the digestion of the raw material, the same ore mixture as in Example 1 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.
Hydrolysis was carried out as in Example 1 with addition of 0.9 m3 washing filtrate (fraction B). The hydrolysis yield was 95.7%. The suspension obtained was filtered. The waste acid accumulating had a concentration of 26.3% by weight H2S0~. Tha filter cake was then washed with water and the washing filtrate separated into three fractions. Fraction A was separated off up to a concentra-tion of 20.5% by weight H2S04. 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 26 808 9 ~4485 fed to the recycling process contained 24.7% by weight H2S04, 334 ppm Cr and 562 ppm V. It contained 97% of the sulfate ions used in digestion of the raw material; the remaining 3~ were chemically fixed to the titanium oxide S hydrolyzate.
After fraction A, 0.9 m3 filtrate were separated off as fraction B while the H2SO~ concentration fell from 20;5 to 6% by weight. Fraction B contained on average 17.8% by weight H2S0~, corresponding to 9% of the total sulfuric acid present after hydrolysis~
A PROCESS FOR THE PRODUCTION OF TITANIUM DIOXIDE
This invention relates to a process for the pro-duction 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 concen-trated waste acid is fed to a recycling process.
It is known that, apart from raw material and pro-cess cos~s, the economy of titanium dioxide production 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, a waste acid of high concen-tration is separated from dilute washing acid through careful monitoring of the sulfuric acid concentration in the liquid accumulating during washing of the hydro-lyzate. This dilute washing acid may advantageously beconcentrated, 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 separa-tion of the metal sulfa~es, and at least 95% pure sul-furic acid and the digestion cake is dissolved with water and part of the waste acid formed during the Le A 26 808 26~ 35 hydrolysi 5 0 f titanyl sulfate. However, thi 5 process is S specially designed for the use of ilmeni~e as raw mate-rial, in addition to which narrow limits are imposed by the metal sulfates, particularly chromium sulfate, re-cycled with the waste acid.
Another major disadvantage of this process is that the TiO2 production process is seriously impaired by the very high proportion of waste acid ~20 to 30~ used to dissolve the digestion cake. If the quantity of sulfuric acid used to digest the raw material is correspondingly reduced, a lower yield of Tioso4 is obtained when the autothermal discontinuous digestion reaction is carried out on an industrial scale. ~f, on the Gther hand, the H2S04:Tio2 ratio is kept constant during the digestion reaction, such a high H2SO~:TiO2 ratio is obtained in the titanyl sulfate solution through the waste acid used to dissolve the digestion cake that the hydrolysis yield ard 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, thereby minimizing both treatment costs and wastewater pollution, without adversely affecting the proces~ as 30 B whole or the quality of the titanium dioxide pigment.
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 80~
2~
digested material to form a titanyl sulfate solution, S hydrolysis of the titanyl sulfate, separation of the hydrolyzate from the metal-sulfate-containing sulfuric acid, the so-called waste acid, washing of the hydroly-zate and calcination to the TiO2 pigment, the solution accumulating during separation of the solids from the suspension formed during hydrolysis of the titanyl sul-fate being fed ent;rely as waste acid to a treatment orrecycling process and the liquid accumulating during washing of the hydrolyzate being divided into three or four fractions of decreasing sulfuric acid concentra-tion, the first fraction A accumulating being combined with the waste acid and fed to the treatment or re-cycling 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 di-gestion 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 pro-: 25 cess, the waste acid fed to the treatment or recycling process has a concentration of at least 23% by weight : H2S04 and preferably of at least 24X by weight H2S04 The fraction B returned to hydrolysis of the titanyl sulfate from washing of the hydrolyzate preferably contains 7 to 23% by weight H2SO~ and the fraction C used to dissolve the digested material 0.2 to 7% by weight H2SO4.
In one preferred embodiment of the process, hydrolysis of the titanyl sulfate is carried out using separately Le A 26 808 2~44~35 produced hydrolysis nuclei and fraction B is only added after at least 50% of the total duration of the hydrolysis 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 concentra-tion. These fractions are then specifically returned to the process or are removed.
More particularly, the process comprises the followingsteps:
Titanium raw materials, particularly ilmenite or titanium slag, are disgested in known manner with 80 to 95%
sulfuric acid. The sulfuric acid used is preferably a mixture of at least 95% sulfuric acid or oleum and at least 60% sulfuric acid recovered by concen~ration of wss~e acid from the sulfate process by evaporation and sepa-ration of ~he metal sulfates from the sulfuric acid.
Alterna~ively, sulfuric acid recovered from waste acid by other recycling processes may also be used.
According to the invention, the preferably solid digested material which accumulates during digestion of the raw material is dissolved with the third fraction C of the solution accumulating during washing of the hydrolyzate.
The fraction in guestion has an H2S0~ 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 ~5 solution obtained.
Le A 26 808 2at~44~3s 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 dura~ion 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 (TiO211 at the end of the hydrolysis process. The addition of fraction B
containing 7 to 23% by weight H2S04 in accordance with the invention does not adversely affect pigment quality.
However, the concentration of the waste acid is distinctly increased in relation to the concentration obtained where water is added in accordance with the prior art.
The hydroly7ate is separated, optionally by filtra-tion, from the mother liquor, the waste acid containing H2S04 and metal sulfates, and subsequently washed with water, The concentration of H2S04 and metal sulfates of the solution, which accumulates during this washing of the hydrolyzate, changes characteristically during the washing process. Ini~ially, waste acid is displaced from the hydrolyzate by the washing water. The sulfuric acid concentration then falls slowly from the range of 24-27%
by weight to values of 18 to 23% by weight, According to the invention, this concentrated solution i5 fed as the first fraction A to the waste acid until the H2S04 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 2Q~4~35 contained in the titanyl sulfate solution after separa-tion of iron sulfate heptahydrate, corresponding to 80-93% of the sulfuric acid present in the suspension after hydrolysis of the titanyl sulfate. A fraction B is then separated off while the H2S04 concentration falls rapid-ly from 25-15 to 12-3K by weight. According to the invention, this fraction B with an average H2S04 content of 10-23% by weight contains 4-12X of the sulfuric acid present after hydrolysis and, as described above, is added during hydrolysis of the titanyI sulfate. The relatively highly dilute solution accumulating after the steep fall in concentration to l-ss than 12% by weight H2S04 is separated as the third fraction C. According to the invention, this fraction C with, on average, 0.2-7X by weight H2S04 contains 1 to SX 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 SX 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 21-2~X
by weight H2S04 and problems can be expected from the metal ions relevant to color of the pigment, particular-ly Cr or V ions, present in the recycled solutions, it has surprisingly been found that neither th- titanium d;oxide production proce-s its-lf nor the quality of the pigment obtained is ad~ersely affected by application of the process according to the invention. A major Le A 26 808 ;
'~ ,' ' 4~85 advan~age of ~he i~vention is t~a~ it gives a was~e acid of high concen~ra~ion bo~h where ilmenite and where ti~anium slag is used as the raw ma~erial and, at the same ~ime, minimizes wastewater pollu~ion. The was~e acid concen~ration obtained, which is at least 2~% by weight H2504 and preferably 24-27% by weight H2S04, enables the cost of treatment by recy~ling to be distinctly reduced c~mpared wi~h the prior art.
The advantages of th~ process according ~o ~he in~ention are illustrated by the following Examples.
Example 1 1,170 kg titanium slag containing 75~ by weight Tio2 and 405 kg ilmenite containing 54~ by weight Tio2 were digested with 1,996 kg 77.2% sulfuric acid and 970 kg 27%
oleum. (The 77.2% sulfuric acid had been recovered from waste acid in accordance with US 4,502,976. It contai~ed 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 3.4 m3 of the fraction C separated off during the washing of the hydrolyzate of a preceding batch and C.9 m3 wash solution from the washing of the digestion residues. The solution was filtered and the titanyl sulfate hydrolyzed.
Hydrolysis was carried out as follows:
49 l of a suspension of hydrolysis nuclei separately produced by precipitation of titanyl sulfate with sodium hydroxide were added to 4.35 m3 titanyl sulfate solution ~5 Le A 26 808 2~ 4RS
(corresponding to 1 t Tio2)~ The mixture was brought to the boiling temperature by introduction of steam and boiled to the Nmatch 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 m3 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 was 95.4%.
The suspension obtained was filtered, waste acid containing 26.9% by weight H2S04 accumulating as filtrate.
The filter cake was then washed with water. The solution accumulating as filtrate during washing of the filter cake was divided into 4 fractions:
At the beginning of the washing process, the concen-tration of the solution fell slowly from 26.4 to 22-23% by weight H2S04 and then rapidly to values below 5% by weight.
The first 2.9 m3 filtrate were separated off as fraction A
until a concentration of 23% by weight H2S04 had been reached. This fraction had an average ccncentration of 24.6% by weight H2S04 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 H2S0;, 345 ppm Cr and 580 ppm V. It contained 95.2% of the sulfate ions used during digestion of the raw material. 0.9 m3 of the filtrate were then separated off as fraction B while the concentration of the filtrate fell from 23 to 10.2% by weight H2S04. The fraction B had an average concentration of 19.6% by weight H2S04, 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 m3 solution were then separated off as fraction C. This filtrate fraction had a concentration of 5.5% by weight H2S04, 19 ppm Cr and 32 ppm Le A 26 808 8 ~44~35 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 filtrate contained 3.1% by weight H2S0~. The concentration fell to 0.3% by weight H2S0~. 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 hydroly-zate 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 filter cake, followed by calcination under standard conditions at 950C
in a rotary kiln to form rutile pigment.
The pigment thus obtained was substantially identical with the typical standard of normal production where water rather than fraction B was added during hydrolysis and the digested material was dissolved with water.
Example 2 In the digestion of the raw material, the same ore mixture as in Example 1 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.
Hydrolysis was carried out as in Example 1 with addition of 0.9 m3 washing filtrate (fraction B). The hydrolysis yield was 95.7%. The suspension obtained was filtered. The waste acid accumulating had a concentration of 26.3% by weight H2S0~. Tha filter cake was then washed with water and the washing filtrate separated into three fractions. Fraction A was separated off up to a concentra-tion of 20.5% by weight H2S04. 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 26 808 9 ~4485 fed to the recycling process contained 24.7% by weight H2S04, 334 ppm Cr and 562 ppm V. It contained 97% of the sulfate ions used in digestion of the raw material; the remaining 3~ were chemically fixed to the titanium oxide S hydrolyzate.
After fraction A, 0.9 m3 filtrate were separated off as fraction B while the H2SO~ concentration fell from 20;5 to 6% by weight. Fraction B contained on average 17.8% by weight H2S0~, corresponding to 9% of the total sulfuric acid present after hydrolysis~
3.3 m3 filtrate having an H2S04 concentration between 6 and 0.4% by weight, average 1.7% by weight, were separ-ated off as fraction C. It contained 2.5% of the sulfuric acid present on completion of hydrolysis.
- The hydrolyzate was processed to rutile pigment as in Example 1. The pigment substantially corresponded to the production standard.
Le A 26 808 10
- The hydrolyzate was processed to rutile pigment as in Example 1. The pigment substantially corresponded to the production standard.
Le A 26 808 10
Claims (9)
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, feeding the waste acid to a treatment or recycling pro-cess, washing the hydrolyzate and separating the washing liquid accumulating during the washing of the hydro-lyzate into fractions of decreasing concentrations, and calcining the hydrolyzate to form TiO2 pigment wherein the first fraction (A) of the separated fractions of the washing liquid is combined with waste acid and fed to the treatment or recycling process, the second fraction (B) is used instead of water in titanyl sulfate hydro-lyses and the third fraction (C) is used to dissolve digested material from digestion of titanium raw mate-rial.
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 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-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.
5. A process according to claim 1, wherein the waste acid fed to the treatment or recycling process has a concentration of at least 23% by weight H2SO4.
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 H2SO4.
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 weight H2SO4.
8. A process according to claim 1, wherein the fraction C used to dissolve the digested material con-tains 0.2 to 7% by weight H2SO4.
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
Le A 26 808
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3912554.8 | 1989-04-17 | ||
| DE3912554A DE3912554C1 (en) | 1989-04-17 | 1989-04-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2014485A1 true CA2014485A1 (en) | 1990-10-17 |
Family
ID=6378838
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002014485A Abandoned CA2014485A1 (en) | 1989-04-17 | 1990-04-12 | 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) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005038060A1 (en) * | 2003-10-17 | 2005-04-28 | Bhp Billiton Innovation Pty Ltd | Production of titania |
| US7429364B2 (en) | 2002-10-18 | 2008-09-30 | Bhp Billiton Innovation Pty. Ltd. | Production of titania |
| US7485268B2 (en) | 2002-10-18 | 2009-02-03 | Bhp Billiton Innovation Pty. Ltd. | Production of titania |
| US7485269B2 (en) | 2002-10-18 | 2009-02-03 | Bhp Billiton Innovation Pty. Ltd. | Production of titania |
Families Citing this family (7)
| 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 |
| 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 |
Family Cites Families (5)
| 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 |
| DE3718674A1 (en) * | 1987-06-04 | 1988-12-15 | Bayer Ag | METHOD FOR PRODUCING TITANIUM DIOXIDE |
| DE3736111A1 (en) * | 1987-10-26 | 1989-05-03 | Kronos Titan Gmbh | METHOD FOR THE ENERGY-SAVING AND MATERIAL-SAVING RENEWAL OF THE DUENOUS ACID INVOLVED IN TITANIUM OXIDE MANUFACTURE AFTER THE SULPHATE PROCESS |
| CH672633A5 (en) * | 1987-11-23 | 1989-12-15 | Escher Wyss Ag | |
| 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
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7429364B2 (en) | 2002-10-18 | 2008-09-30 | Bhp Billiton Innovation Pty. Ltd. | Production of titania |
| US7485268B2 (en) | 2002-10-18 | 2009-02-03 | Bhp Billiton Innovation Pty. Ltd. | Production of titania |
| US7485269B2 (en) | 2002-10-18 | 2009-02-03 | Bhp Billiton Innovation Pty. Ltd. | Production of titania |
| WO2005038060A1 (en) * | 2003-10-17 | 2005-04-28 | Bhp Billiton Innovation Pty Ltd | Production of titania |
| EA009207B1 (en) * | 2003-10-17 | 2007-12-28 | Би Эйч Пи БИЛЛИТОН ИННОВЕЙШН ПТИ ЛТД. | Production of titania |
| US7326390B2 (en) | 2003-10-17 | 2008-02-05 | Bhp Billiton Innovation Pty Ltd. | Production of titania |
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 |
| AU626657B2 (en) | 1992-08-06 |
| 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 |
| FI901874A0 (en) | 1990-04-12 |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Discontinued |