CA1061056A - Sprayable precipitating silica suspension - Google Patents
Sprayable precipitating silica suspensionInfo
- Publication number
- CA1061056A CA1061056A CA236,993A CA236993A CA1061056A CA 1061056 A CA1061056 A CA 1061056A CA 236993 A CA236993 A CA 236993A CA 1061056 A CA1061056 A CA 1061056A
- Authority
- CA
- Canada
- Prior art keywords
- dissolver
- tank
- process according
- silica
- stirring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
- C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
- C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/22—Rheological behaviour as dispersion, e.g. viscosity, sedimentation stability
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
- Mixers Of The Rotary Stirring Type (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a process for producing a sprayable highly concentrated precipitating silica suspension which has a low grit content and contains 12%, preferably more than 18% of solids, which comprises continuously feeding a silica filter cake and a dispersing agent by means of feed members into a dissolver tank while maintaining a pH value of not more than 4, and stirring the mixture in said tank by means of a stirring dissolver, the ratio of the tank diameter to the dia-meter of the stirring dissolver being 3:1, the maximum ratio of dissolver tank diameter to height of filling of the tank being 1:2, and at least 1.5 to 2 kg of silica suspension being present in the tank per 1 kg of silica filter cake fed therein, said stirring being carried out by the dissolver at a peripheral speed of 20 to 30 metres per second, the silica filter cake and dispersing agent being withdrawn from a zone of maximum turbu-lence by a separating member or a mixer.
The present invention provides a process for producing a sprayable highly concentrated precipitating silica suspension which has a low grit content and contains 12%, preferably more than 18% of solids, which comprises continuously feeding a silica filter cake and a dispersing agent by means of feed members into a dissolver tank while maintaining a pH value of not more than 4, and stirring the mixture in said tank by means of a stirring dissolver, the ratio of the tank diameter to the dia-meter of the stirring dissolver being 3:1, the maximum ratio of dissolver tank diameter to height of filling of the tank being 1:2, and at least 1.5 to 2 kg of silica suspension being present in the tank per 1 kg of silica filter cake fed therein, said stirring being carried out by the dissolver at a peripheral speed of 20 to 30 metres per second, the silica filter cake and dispersing agent being withdrawn from a zone of maximum turbu-lence by a separating member or a mixer.
Description
The present invention relates to a process for producing - a sprayable, highly concentrated precipitating silica suspension which has a low grit content and contains at least 12%, preferably more than 18% of solids.
Precipitating silica, which is produced in a conventional manner by wet-chemical processes, must be dried in order to satisfy engineering requirements. For this purpose a spray dryer may be used. However, in this kind of dryer the nozzle and the fan blower become clogged due to both the high solids content and the structure of the silica filter cake. Therefore, the structure of the silica filter cake must be such that the nozzle or the fan blower of the spray dryer will not be obstructed.
It is known that in order to adapt t~e structure of the silica filter cake to the re`quirements of the spray dryer, the filter cake is diluted with water. However, for a favourable dilution with water for the process a great amount of energy must be used in order to remove the water from the silica filter cake during the drying. In this method of treating the silica filter cake the structure of the filter mass obtained is inhomo-geneous and contains grit, i.e., it contains particles havingsizes of more than 45 ~m.
The present invention provides a process which so struc-tures a silica filter cake that the consumption of energy of vaporization required for the spray drying is only small and that the filter mass contains a homogenous grit-free silica.
According to the present invention therefore there is provided a process for producing a sprayable highly concentrated precipitating silica suspension which has a low grit content and contains at least 12%, preferably more than 18% of solids which process comprises continuously feeding by means of feed elements silica filter cake and dispersing agent into a dissolver tank while maintaining a pH value of not more than 4, and stirring the - 1 - ~
lQ61056 mixture in said tank by means of a stirring dissolver, the ratio of the tank diameter to the diameter of the stirring dissolver being 3:1, the maximum ratio of dissolver tank diameter to the height of filling of the tank being 1:2, and at least 1.5 to 2 kg of silica suspension being present in the tank per 1 kg of silica filter cake fed in, said stirring being carried out by means of the dissolver at a peripheral velocity of 20 to 30 metres per second, the silica filter cake and dispersing agent being withdrawn from a zone of maximum turbulence by way of a separating member or a mixer.
A single screw or a double screw may be used as the feed member.
The dispersing agent, which is preferably an aqueous dilute acid, and more preferably a 20 to 30% H2SO4, can be fed to the dissolver by a feed member simultaneously with the silica filter cake. The ratio of the diameter of the dissolver tank to that of the stirring dissolver may be approximately 2.5:1 while the ratio of filling height to tank diameter can be 1:1. A
double-disc dissolver can be used as the stirring dissolver. A
wire strainer can be used as the separator or the suspension can be drawn off by a forced circulation mixer connected at the outlet end or by means of a mixer pump. A portion of the silica suspension passing through the wire strainer or through the mixer can be returned to the dissolver tank. Because of this recycling shearing of the silica present in the filter cake the suspension has the desired freedom from lumps and grit.
The advantages of the process according to the invention lie inter alia in a restructuring of the silica filter cake such that the resulting silica suspension is homogeneous and free from grit and can be subjected to spray drying without additional consumption of energy and additional work.
The present invention will be further illustrated by ! way of the following Example in conjunction with the accompanying drawing in which Eig. 1 is a schematic representation of an apparatus for effecting a process according to one embodiment of the present in~ention.
Example 1 260 kg of silica filter cake having a water content of 82% by weight are fed into a 1.5 cu m dissolver tank 4 per minute by means of the double screw,l operating at 295 r.p.m.
through the narrowed discharge 2 simultaneously with 0.6 litre of a dilute aqueous 30% sulphuric acid passing from pipe 3 in order to increase the mixing-kneading effect. The concentration of acid is maintained such that the silica suspension has a pH
value of 3. The dissolver tank 4 is cylindrical and has a diame-ter of 1.2 m, a height of 1.5 m. The dissolver 5, which is a double-disc dissolver, has a diameter of the discs 6 and 7 of 0.4 m and is driven by the electric motor 8, which has an out-put of 36.7 kw (50 hp). The rotational speed of the two discs 6 and 7 is 21 metres per second (1000 r.p.m.). By means of the immersion probes 9 and 10 the height of the suspension in the tank 4 is kept between 0.8 and 1.20 metres, so that for 1 kg of silica filter cake fed there are 1.5 kg of silica suspension in the dissolver tank 4. The silica suspension is drawn off from the zone of maximum turbulence by means of the wire strainer 12.
A portion of this silica suspension is recycled through pipe 13 and the pump 14 in order to further decrease the proportion of grit and lumps. The fact that the liquid phase remains intact and is sprayable in this process if a critical concentration is not exceeded is surprising. The silica suspension obtained by means of the process according to the invention has a viscosity of approximately 200 cp, as measured in a Haake viscotester.
Precipitating silica, which is produced in a conventional manner by wet-chemical processes, must be dried in order to satisfy engineering requirements. For this purpose a spray dryer may be used. However, in this kind of dryer the nozzle and the fan blower become clogged due to both the high solids content and the structure of the silica filter cake. Therefore, the structure of the silica filter cake must be such that the nozzle or the fan blower of the spray dryer will not be obstructed.
It is known that in order to adapt t~e structure of the silica filter cake to the re`quirements of the spray dryer, the filter cake is diluted with water. However, for a favourable dilution with water for the process a great amount of energy must be used in order to remove the water from the silica filter cake during the drying. In this method of treating the silica filter cake the structure of the filter mass obtained is inhomo-geneous and contains grit, i.e., it contains particles havingsizes of more than 45 ~m.
The present invention provides a process which so struc-tures a silica filter cake that the consumption of energy of vaporization required for the spray drying is only small and that the filter mass contains a homogenous grit-free silica.
According to the present invention therefore there is provided a process for producing a sprayable highly concentrated precipitating silica suspension which has a low grit content and contains at least 12%, preferably more than 18% of solids which process comprises continuously feeding by means of feed elements silica filter cake and dispersing agent into a dissolver tank while maintaining a pH value of not more than 4, and stirring the - 1 - ~
lQ61056 mixture in said tank by means of a stirring dissolver, the ratio of the tank diameter to the diameter of the stirring dissolver being 3:1, the maximum ratio of dissolver tank diameter to the height of filling of the tank being 1:2, and at least 1.5 to 2 kg of silica suspension being present in the tank per 1 kg of silica filter cake fed in, said stirring being carried out by means of the dissolver at a peripheral velocity of 20 to 30 metres per second, the silica filter cake and dispersing agent being withdrawn from a zone of maximum turbulence by way of a separating member or a mixer.
A single screw or a double screw may be used as the feed member.
The dispersing agent, which is preferably an aqueous dilute acid, and more preferably a 20 to 30% H2SO4, can be fed to the dissolver by a feed member simultaneously with the silica filter cake. The ratio of the diameter of the dissolver tank to that of the stirring dissolver may be approximately 2.5:1 while the ratio of filling height to tank diameter can be 1:1. A
double-disc dissolver can be used as the stirring dissolver. A
wire strainer can be used as the separator or the suspension can be drawn off by a forced circulation mixer connected at the outlet end or by means of a mixer pump. A portion of the silica suspension passing through the wire strainer or through the mixer can be returned to the dissolver tank. Because of this recycling shearing of the silica present in the filter cake the suspension has the desired freedom from lumps and grit.
The advantages of the process according to the invention lie inter alia in a restructuring of the silica filter cake such that the resulting silica suspension is homogeneous and free from grit and can be subjected to spray drying without additional consumption of energy and additional work.
The present invention will be further illustrated by ! way of the following Example in conjunction with the accompanying drawing in which Eig. 1 is a schematic representation of an apparatus for effecting a process according to one embodiment of the present in~ention.
Example 1 260 kg of silica filter cake having a water content of 82% by weight are fed into a 1.5 cu m dissolver tank 4 per minute by means of the double screw,l operating at 295 r.p.m.
through the narrowed discharge 2 simultaneously with 0.6 litre of a dilute aqueous 30% sulphuric acid passing from pipe 3 in order to increase the mixing-kneading effect. The concentration of acid is maintained such that the silica suspension has a pH
value of 3. The dissolver tank 4 is cylindrical and has a diame-ter of 1.2 m, a height of 1.5 m. The dissolver 5, which is a double-disc dissolver, has a diameter of the discs 6 and 7 of 0.4 m and is driven by the electric motor 8, which has an out-put of 36.7 kw (50 hp). The rotational speed of the two discs 6 and 7 is 21 metres per second (1000 r.p.m.). By means of the immersion probes 9 and 10 the height of the suspension in the tank 4 is kept between 0.8 and 1.20 metres, so that for 1 kg of silica filter cake fed there are 1.5 kg of silica suspension in the dissolver tank 4. The silica suspension is drawn off from the zone of maximum turbulence by means of the wire strainer 12.
A portion of this silica suspension is recycled through pipe 13 and the pump 14 in order to further decrease the proportion of grit and lumps. The fact that the liquid phase remains intact and is sprayable in this process if a critical concentration is not exceeded is surprising. The silica suspension obtained by means of the process according to the invention has a viscosity of approximately 200 cp, as measured in a Haake viscotester.
Claims (13)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for producing a sprayable highly concen-trated precipitating silica suspension which has a low grit content and contains at least 12% of solids, which comprises continuously feeding a silica filter cake and a dispersing agent by means of feed members into a dissolver tank while maintaining a pH value of not more than 4, and stirring the mixture in said tank by means of a stirring dissolver, the ratio of the tank diameter to the diameter of the stirring dissolver being 3:1, the maximum ratio of dissolver tank diameter to height of filling of the tank being 1:2, and at least 1.5 to 2 kg of silica suspension being present in the tank per 1 kg of silica filter cake fed therein, said stirring being carried out by the dissolver at a peripheral speed of 20 to 30 metres per second, the silica filter cake and dispersing agent being with-drawn from a zone of maximum turbulence by a separating member or a mixer.
2. A process according to claim 1, in which the feed member is a single screw.
3. A process according to claim 1, in which the feed member is a double screw.
4. A process according to the claim 1, 2 or 3, in which the dispersing agent is an acid.
5. A process according to the claim 1, 2 or 3, in which the dispersing agent is dilute aqueous sulphuric acid.
6. A process as claimed in claim 1, 2 or 3, in which the dispersing agent is 20 to 30% sulphuric acid solution.
7. A process according to the claim 1, 2 or 3, in which the dispersing agent and the silica filter cake are simultaneously fed into the dissolver tank by a feed member.
8. A process according to the claim 1, 2 or 3, in which the ratio of the diameter of the dissolver tank to that of the stirring dissolver is 2.5:1.
9. A process according to the claim 1, 2 or 3, in which the ratio of filling height of the tank to the tank diameter is 1:1.
10. A process according to the claim 1, 2 or 3, in which the dissolver is a double-disc dissolver.
11. A process according to the claim 1, 2 or 3 in which the separating member is a wire strainer.
12. A process according to the claim 1, 2 or 3, in which the suspension is drawn off by a forced circulation mixer connected at an outlet end or by means of a mixer pump.
13. A process according to the claim 1, 2 or 3, in which a portion of the withdrawn silica suspensions passing through a wire strainer or through the mixer is returned to the dissolver tank.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19742447613 DE2447613C3 (en) | 1974-10-05 | Process for the production of a sprayable precipitated silica suspension |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1061056A true CA1061056A (en) | 1979-08-28 |
Family
ID=5927651
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA236,993A Expired CA1061056A (en) | 1974-10-05 | 1975-10-03 | Sprayable precipitating silica suspension |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS589765B2 (en) |
| BE (1) | BE834209A (en) |
| CA (1) | CA1061056A (en) |
| ES (1) | ES441516A1 (en) |
| FR (1) | FR2286793A1 (en) |
| GB (1) | GB1511720A (en) |
| IT (1) | IT1047273B (en) |
| NL (1) | NL7511660A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI574917B (en) * | 2012-03-22 | 2017-03-21 | 隆迪亞營運公司 | Process for preparing precipitated silica using a mixer or extruder |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2453880A1 (en) * | 1979-04-13 | 1980-11-07 | Rhone Poulenc Ind | NOVEL SILICA-BASED PIGMENT IN BALL FORM, PROCESS FOR OBTAINING THE SAME AND APPLICATION, IN PARTICULAR AS REINFORCING FILLER IN ELASTOMERS |
| FR2536380B1 (en) * | 1982-11-24 | 1985-12-13 | Rhone Poulenc Chim Base | PROCESS FOR IMPROVING THE RHEOLOGICAL PROPERTIES OF A PRECIPITATED SILICA SUSPENSION |
| MY116513A (en) * | 1995-04-19 | 2004-02-28 | Ppg Ind Ohio Inc | Amorphous precipitated silica having large liquid carrying capacity |
| DE19807700A1 (en) * | 1998-02-24 | 1999-08-26 | Degussa | Precipitated silica granules |
-
1975
- 1975-09-26 GB GB39504/75A patent/GB1511720A/en not_active Expired
- 1975-10-02 FR FR7530252A patent/FR2286793A1/en active Granted
- 1975-10-03 CA CA236,993A patent/CA1061056A/en not_active Expired
- 1975-10-03 IT IT69462/75A patent/IT1047273B/en active
- 1975-10-03 NL NL7511660A patent/NL7511660A/en active Search and Examination
- 1975-10-03 BE BE6045202A patent/BE834209A/en not_active IP Right Cessation
- 1975-10-04 ES ES441516A patent/ES441516A1/en not_active Expired
- 1975-10-06 JP JP50120560A patent/JPS589765B2/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI574917B (en) * | 2012-03-22 | 2017-03-21 | 隆迪亞營運公司 | Process for preparing precipitated silica using a mixer or extruder |
Also Published As
| Publication number | Publication date |
|---|---|
| NL7511660A (en) | 1976-04-07 |
| GB1511720A (en) | 1978-05-24 |
| JPS5163396A (en) | 1976-06-01 |
| FR2286793A1 (en) | 1976-04-30 |
| DE2447613B2 (en) | 1976-08-26 |
| ES441516A1 (en) | 1977-04-01 |
| BE834209A (en) | 1976-04-05 |
| FR2286793B1 (en) | 1978-04-07 |
| JPS589765B2 (en) | 1983-02-22 |
| DE2447613A1 (en) | 1976-04-08 |
| IT1047273B (en) | 1980-09-10 |
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