WO1993008916A1 - Method for grinding finely divided material - Google Patents
Method for grinding finely divided material Download PDFInfo
- Publication number
- WO1993008916A1 WO1993008916A1 PCT/FI1992/000301 FI9200301W WO9308916A1 WO 1993008916 A1 WO1993008916 A1 WO 1993008916A1 FI 9200301 W FI9200301 W FI 9200301W WO 9308916 A1 WO9308916 A1 WO 9308916A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- jet mill
- coarse fraction
- pressure roller
- counter jet
- roller crusher
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
- B02C23/08—Separating or sorting of material, associated with crushing or disintegrating
- B02C23/10—Separating or sorting of material, associated with crushing or disintegrating with separator arranged in discharge path of crushing or disintegrating zone
- B02C23/12—Separating or sorting of material, associated with crushing or disintegrating with separator arranged in discharge path of crushing or disintegrating zone with return of oversize material to crushing or disintegrating zone
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C19/00—Other disintegrating devices or methods
- B02C19/06—Jet mills
- B02C19/065—Jet mills of the opposed-jet type
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C21/00—Disintegrating plant with or without drying of the material
Definitions
- This invention refers to a method for increasing the ef ⁇ ficiency of grinding finely divided material, wherein primary material is ground and dried in a counter jet mill and the formed product is classified into a fine fraction and a coarse fraction, and the coarse fraction obtained is returned to the counter jet mill for regrinding.
- the counter jet grinding technique is suitable in grinding a lot of different materials. With the above disclosed method very high quality end products will be obtained to moderate costs, but for some materials the coarse fraction part will increase rapidly and a lot of energy will be consumed to recirculate this increased part.
- the specific weight of the coarse fraction returning to the counter jet mill is also often remarkably lower than the specific weight of the primary feed material, and for this reason the grinding efficiency of the counter jet mill will dec ⁇ rease remarkably due to the changes in the specific weight of the materials to be ground. The specific weight changes of the material to be ground will thus increase the grin ⁇ ding costs.
- the purpose of the present invention is to eliminate these problems and to increase the efficiency of the grinding process. This is achieved by the method, which is charac ⁇ terized in that the coarse fraction is led via a pressure roller crusher to the feed funnel of the counter jet mill.
- the efficiency of the grinding process can be increased remarkably, because new micro cracks and cracks will be formed into the coarse fraction particles when they pass through the pressure roller crusher, which cracks will facilitate further grinding of these particles in the counter jet mill during the next grinding step. Due to the method according to the invention the weight ratio between the the coarse fraction and the fine fraction will decrease remarkably, i.e. the efficiency of grinding pro ⁇ cess will increase.
- Materials suitable for the counter jet ginding technique can be chared into three different groups due to their physical properties.
- the particles of materials belonging to group one are brittle and hard, and possibly hardened by water such as water granulated blast-furnace slag.
- the particles of materials belonging to group two are undama ⁇ ged and undisintegrated, such as natural minerals, quartz and zirconium sand.
- fig. 1 shows a flow sheet of a base device for carrying out the method according to this invention
- fig. 2 shows a flow sheet of an alternative device
- fig. 3 shows a flow sheet of a prefered device for car- rying out the method according to the invention.
- finely divided primary materi ⁇ al is fed from a silo 1 into a feed funnel 2 of a counter jet mill, and therefrom it is fed by means of a double valve feeder 3 into a pressurized equalizing tank 4 and therefrom by the influence of a srew feeder 5 further-as an uniform material flow into a fluidizing tank 6, wherein the material is fluidized by means of a working gas flow.
- a working gas material mixture is accelerated by means of the super pressure maintained in the fluidizing tank 6 through a bisecting device 7 and two substantially oppositely directed, long accelerating nozz ⁇ les 8 into a grinding chamber 9, wherein the material par ⁇ ticles rushing from the oppositely directed accelerating nozzles 8 collide against each other at a very high speed and are ground due to the strong collision influence.
- the ground material-working gas mixture rushes from the grin ⁇ ding chamber 9 further to a pneumatic centrifugal classi ⁇ fier 10 wherein the solid particles of the material wor ⁇ king gas mixture are classified into a fine fraction and a coarse fraction.
- the fine fraction i.e.
- the end product is removed from the classifier 10 as a continuous material working gas flow through the outlet pipe 11 for the fine fraction.
- the coarse fraction is accumulated into a pocket 12 outside the pheripheral face of the classifier 10, whe- refrom it is removed batchwise into a feed pipe 14 of a pressure roller crusher 13 beneath the pocket 12.
- a pressure roller crusher 13 When the solid particles of the coarse fraction pass through the pressure roller crusher 13 as a thick material mat, they will be at least partly crushed and at the same time new micro cracks and cracks will be formed in the particles.
- the pressed material clods formed in the pressure roller crusher 13 are returned or dropped into the feed funnel 2 of the counter jet mill in order to be regrinded.
- micro cracks and cracks formed in the solid particles will remar ⁇ kably facilitate the further grinding of the material particles in the counter jet mill 9. Further the feeding of the material into the counter jet mill 9 will be more effective, because the specific weight of the material clods coming from the pressure roller crusher 13 is often many times higher than the specific weight of untreated coarse fraction.
- Primary materials belonging to group one, having brittle and hard particles, can preferably be ground in the device shown in fig.l ⁇
- the material to be ground belongs to group two having substantially undamaged and undisintegrated particles it will be prefered that primary material is led through a pressure roller crusher 15 of their own, as shown in fig. 2, to the feed funnel 2 of the counter jet mill 9, whereby these particles will be partly crushed and at the same ti ⁇ me new cracks and micro cracks facilitating grinding will be formed in the particles.
- a common pressure roller crusher cannot be used at least not without any auxiliary devices.
- the specific weight of the coarse fraction can preferably be mechani ⁇ cally increased by pressing away the air which is contained in the spaces between the solid particles of the coarse fraction during the feeding of the coarse fraction. This could be achieved for instance by means of a pressure screw 16 and a pair of rollers 17 cooperating with this screw or alternatively by means of one or several pressure pistons.
- the specific weight of the coarse fraction has been increased in this way its physical properties will be more similar to those of the primary material, whereby such a pressurized coarse fraction and primary material can be treated together without problems i a common pressure roller crusher, as disclosed in figure 3.
- test number 1 no pressure roller crusher was used at all, but the primary material was fed directly into the feed funnel of a jet mill acting in a closed loop with a FPC-classifier.
- test number two the primary material was predisintegra- ted with a pressure roller crusher before feeding into the jet mill used in the previous test.
- test number 3 In test number three primary material was fed directly into the feed funnel of the jet mill used in the previous tests but the feedback of the FPC-classifier i.e. the coarse fraction was fed via a pressure roller crusher back to the feed funnel in ac ⁇ cordance with figure 1 of this application. The results of these test are disclosed in the table below.
- Circulation load means the ratio between the feedback or Coarse fraction and the end product in per cent.
Landscapes
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Disintegrating Or Milling (AREA)
Abstract
This invention refers to a method for increasing the efficiency of the grinding of finely divided material, wherein primary material is ground in a counter jet mill (9) and the product formed is classified into a fine fraction and a coarse fraction and the coarse fraction received is returned to the counter jet mill (9). The method is characterized in that coarse fraction is led via a pressure roller crusher (13) to the feed funnel (2) of the counter jet mill.
Description
Method for grinding finely divided material
This invention refers to a method for increasing the ef¬ ficiency of grinding finely divided material, wherein primary material is ground and dried in a counter jet mill and the formed product is classified into a fine fraction and a coarse fraction, and the coarse fraction obtained is returned to the counter jet mill for regrinding.
The counter jet grinding technique is suitable in grinding a lot of different materials. With the above disclosed method very high quality end products will be obtained to moderate costs, but for some materials the coarse fraction part will increase rapidly and a lot of energy will be consumed to recirculate this increased part. The specific weight of the coarse fraction returning to the counter jet mill is also often remarkably lower than the specific weight of the primary feed material, and for this reason the grinding efficiency of the counter jet mill will dec¬ rease remarkably due to the changes in the specific weight of the materials to be ground. The specific weight changes of the material to be ground will thus increase the grin¬ ding costs.
The purpose of the present invention is to eliminate these problems and to increase the efficiency of the grinding process. This is achieved by the method, which is charac¬ terized in that the coarse fraction is led via a pressure roller crusher to the feed funnel of the counter jet mill.
By this method the efficiency of the grinding process can be increased remarkably, because new micro cracks and cracks will be formed into the coarse fraction particles when they pass through the pressure roller crusher, which cracks will facilitate further grinding of these particles in the counter jet mill during the next grinding step. Due
to the method according to the invention the weight ratio between the the coarse fraction and the fine fraction will decrease remarkably, i.e. the efficiency of grinding pro¬ cess will increase.
At the same time the feeding of material into the counter jet mill will be stabilized, because the material mat lea¬ ving the pressure roller crusher is in the form of pres¬ sed, easily breaking material clods. These material clods will at least be broken by the influence of a screw feeder and a rotator of the feeding device of the counter jet mill.
Materials suitable for the counter jet ginding technique can be chared into three different groups due to their physical properties. The particles of materials belonging to group one are brittle and hard, and possibly hardened by water such as water granulated blast-furnace slag. The particles of materials belonging to group two are undama¬ ged and undisintegrated, such as natural minerals, quartz and zirconium sand. Materials belonging to group three ha¬ ve their bulk density decreased dramatically during the grinding step. Such materials are for instance talc and syntetic quartz.
The further characteristics of the invention will appear from the enclosed claims 1 to 5.
Below the invention will be disclosed in more detail refe- ring to the enclosed drawing, wherein
fig. 1 shows a flow sheet of a base device for carrying out the method according to this invention,
fig. 2 shows a flow sheet of an alternative device and
fig. 3 shows a flow sheet of a prefered device for car-
rying out the method according to the invention.
According to this invention finely divided primary materi¬ al is fed from a silo 1 into a feed funnel 2 of a counter jet mill, and therefrom it is fed by means of a double valve feeder 3 into a pressurized equalizing tank 4 and therefrom by the influence of a srew feeder 5 further-as an uniform material flow into a fluidizing tank 6, wherein the material is fluidized by means of a working gas flow. From the fluidizing tank 6 a working gas material mixture is accelerated by means of the super pressure maintained in the fluidizing tank 6 through a bisecting device 7 and two substantially oppositely directed, long accelerating nozz¬ les 8 into a grinding chamber 9, wherein the material par¬ ticles rushing from the oppositely directed accelerating nozzles 8 collide against each other at a very high speed and are ground due to the strong collision influence. The ground material-working gas mixture rushes from the grin¬ ding chamber 9 further to a pneumatic centrifugal classi¬ fier 10 wherein the solid particles of the material wor¬ king gas mixture are classified into a fine fraction and a coarse fraction. The fine fraction i.e. the end product is removed from the classifier 10 as a continuous material working gas flow through the outlet pipe 11 for the fine fraction. The coarse fraction is accumulated into a pocket 12 outside the pheripheral face of the classifier 10, whe- refrom it is removed batchwise into a feed pipe 14 of a pressure roller crusher 13 beneath the pocket 12. When the solid particles of the coarse fraction pass through the pressure roller crusher 13 as a thick material mat, they will be at least partly crushed and at the same time new micro cracks and cracks will be formed in the particles. The pressed material clods formed in the pressure roller crusher 13 are returned or dropped into the feed funnel 2 of the counter jet mill in order to be regrinded. The micro cracks and cracks formed in the solid particles will remar¬ kably facilitate the further grinding of the material
particles in the counter jet mill 9. Further the feeding of the material into the counter jet mill 9 will be more effective, because the specific weight of the material clods coming from the pressure roller crusher 13 is often many times higher than the specific weight of untreated coarse fraction.
Primary materials belonging to group one, having brittle and hard particles, can preferably be ground in the device shown in fig.l^
If the material to be ground belongs to group two having substantially undamaged and undisintegrated particles it will be prefered that primary material is led through a pressure roller crusher 15 of their own, as shown in fig. 2, to the feed funnel 2 of the counter jet mill 9, whereby these particles will be partly crushed and at the same ti¬ me new cracks and micro cracks facilitating grinding will be formed in the particles.
Because the particle size of the primary material oftenly is many times larger than the particle size of the coarse fraction which is to be returned to the counter jet mill 9, a common pressure roller crusher cannot be used at least not without any auxiliary devices.
In order to increase the efficiency of the feeding of the coarse fraction pressure roller crusher 13, especially when the primary material belongs to group three, the specific weight of the coarse fraction can preferably be mechani¬ cally increased by pressing away the air which is contained in the spaces between the solid particles of the coarse fraction during the feeding of the coarse fraction. This could be achieved for instance by means of a pressure screw 16 and a pair of rollers 17 cooperating with this screw or alternatively by means of one or several pressure pistons.
When the specific weight of the coarse fraction has been increased in this way its physical properties will be more similar to those of the primary material, whereby such a pressurized coarse fraction and primary material can be treated together without problems i a common pressure roller crusher, as disclosed in figure 3.
When studying the influence of pressure roller crushing on the capasity of a counter jet mill, especially a PU VA FP jet mill, three different tests were carried out. During all tests the energy consumption of the jet mill was kept constant. In all tests water granulated blast-furnace slag was used as primary material and the fineness of the end products of these tests was held constant. In test number one no pressure roller crusher was used at all, but the primary material was fed directly into the feed funnel of a jet mill acting in a closed loop with a FPC-classifier. In test number two the primary material was predisintegra- ted with a pressure roller crusher before feeding into the jet mill used in the previous test. In test number three primary material was fed directly into the feed funnel of the jet mill used in the previous tests but the feedback of the FPC-classifier i.e. the coarse fraction was fed via a pressure roller crusher back to the feed funnel in ac¬ cordance with figure 1 of this application. The results of these test are disclosed in the table below.
Test No. Circulation load/% Capacity ratio
1 600 1
2 400 1,3
3 250 1,7
Circulation load means the ratio between the feedback or Coarse fraction and the end product in per cent. When the capasity of test number 1 was given ratio 1 the capasities of the other tests received the ratios disclosed in the
table. As will appear from the table, the capasity of the jet mill increases remarkably when a pressure roller crus¬ her is connected to it in accordance with the present in¬ vention.
Claims
1. Method for increasing the efficiency of the grinding of finely divied material, wherein primary material is ground in a counter jet mill (9) and the product formed is classi¬ fied into a fine fraction and a coarse fraction and the coarse fraction received is returned to the counter jet mill (9), characterized in that coarse fraction is led via a pressure roller crusher (13) to the feed funnel (2) of the counter jet mill.
2. Method according to claim 1, characterized in that the primary material is fed into the feed funnel (2) of the counter jet mill via a pressure roller crusher of its own.
3. Method according to claim 1 or 2, characterized in that the specific weight of the coarse fraction to be led into the pressure roller crusher (13) is increased mechanically by pressing away air from the spaces between the particles.
4. Method according to claim 3, characterized in that the mechanical increasing of the specific weight takes place by means of a pressurize screw (16) and a pair of pressurize rollers (17).
5. Method according to claim 3 or 4, characterized in that primary product and coarse fraction with increased specific weight are fed into a common pressure roller crusher.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI915230 | 1991-11-06 | ||
FI915230A FI915230A (en) | 1991-11-06 | 1991-11-06 | Foerfarande Foer malning av finfoerdelat material |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1993008916A1 true WO1993008916A1 (en) | 1993-05-13 |
Family
ID=8533439
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FI1992/000301 WO1993008916A1 (en) | 1991-11-06 | 1992-11-06 | Method for grinding finely divided material |
Country Status (3)
Country | Link |
---|---|
AU (1) | AU2911192A (en) |
FI (1) | FI915230A (en) |
WO (1) | WO1993008916A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001045848A1 (en) * | 1999-12-20 | 2001-06-28 | Bcde Group Waste Management Ltd. Oy | Method and equipment for feeding a counter jet mill |
DE102022003499A1 (en) | 2022-09-22 | 2024-03-28 | Hosokawa Alpine Aktiengesellschaft | Process for reducing the specific energy consumption when comminuting material by combining good bed grinding and jet grinding |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1987003220A1 (en) * | 1985-11-29 | 1987-06-04 | Larox Oy | Procedure and apparatus for producing classified fines product |
WO1988001906A1 (en) * | 1986-09-10 | 1988-03-24 | Larox Oy | Method and equipment for the production of particularly finely divided dry powders |
WO1989009652A1 (en) * | 1988-04-05 | 1989-10-19 | Olmar Ab | Method and apparatus for autogenous comminution primarily of overcompetent, heterogeneous mineral material |
-
1991
- 1991-11-06 FI FI915230A patent/FI915230A/en not_active Application Discontinuation
-
1992
- 1992-11-06 WO PCT/FI1992/000301 patent/WO1993008916A1/en active Application Filing
- 1992-11-06 AU AU29111/92A patent/AU2911192A/en not_active Abandoned
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1987003220A1 (en) * | 1985-11-29 | 1987-06-04 | Larox Oy | Procedure and apparatus for producing classified fines product |
WO1988001906A1 (en) * | 1986-09-10 | 1988-03-24 | Larox Oy | Method and equipment for the production of particularly finely divided dry powders |
WO1989009652A1 (en) * | 1988-04-05 | 1989-10-19 | Olmar Ab | Method and apparatus for autogenous comminution primarily of overcompetent, heterogeneous mineral material |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001045848A1 (en) * | 1999-12-20 | 2001-06-28 | Bcde Group Waste Management Ltd. Oy | Method and equipment for feeding a counter jet mill |
DE102022003499A1 (en) | 2022-09-22 | 2024-03-28 | Hosokawa Alpine Aktiengesellschaft | Process for reducing the specific energy consumption when comminuting material by combining good bed grinding and jet grinding |
Also Published As
Publication number | Publication date |
---|---|
FI915230A0 (en) | 1991-11-06 |
AU2911192A (en) | 1993-06-07 |
FI915230A (en) | 1993-05-07 |
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