RU2696468C1 - Powder granulation method and device for its implementation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical industry, specifically to granulation of powders, for example zinc oxide, which eliminates dust inherent in powders and sticking them in equipment. Disclosed is a group of inventions, one of which relates to a method for granulating a powder, and a second to a device for granulating powder. Powders granulation method is characterized by that the powder is compacted (pre-pressing), then pressed at force in range from 10 to 60 kN with force spread within ±10 kN by roll or roll press. Rollers or rolls of press have wavy surface with mutual location of protrusion opposite to depression of rolls running towards each other. Pressed powder is strained through one or several sieves and the obtained powder is rolled. Device comprises in-series installed conical or cylindrical auger, one or several roller or roller press with pressing rolls or rolls, having wavy surface with the possibility of mutual arrangement of one roll opposite to depression of another roll at their movement towards each other, wiping screens, dish-shaped or tubular granulator.

EFFECT: invention enables to reduce spread of granule hardness values.

16 cl, 6 dwg

Description

The invention relates to the chemical industry, and in particular to granulation of powders, for example zinc oxide, eliminating the dusting and sticking inherent in powders in equipment.

A known method of wet granulation of powders, which consists in the fact that the powder located on the rotating surfaces of a disk or tubular granulator is moistened with a binder and doused with the formation of spherical granules [Chemical Encyclopedia - M .: Soviet Encyclopedia. Ed. I.L. Knunyantsa, 1988 . , p. 1188].

However, the use of a binder can lead to a change in the chemical composition of the granulated powder, which is unacceptable.

A known method of dry granulation of powders [Chemical encyclopedia. - M .: Soviet Encyclopedia. Ed. I.L. Knunyantsa, 1988 . , p. 1188], which consists in the fact that the pre-compacted powder is pressed, for example, between the rolls (rollers) of the press, into briquettes, tiles or strips, which are then crushed with knives and rubbed on sieves. In this case, granules of irregular shape of various sizes and dust are formed. The dust is returned to the feed hopper of the granulator for re-granulation.

 Equipment for its implementation consists of the following devices: pre-pressing screw, roller or roller press, chopping knives, wiping sieves and transport devices.

The method and device for its implementation do not allow to obtain spherical granules, which are needed, for example, to ensure maximum flowability and minimum abrasion during transportation due to the absence of protruding parts. The high hardness of the particles obtained by re-pressing the compacted dust limits the scope of the granules.

The closest way to obtain spherical granules is a method of granulating powders, in accordance with which the powder is pre-compacted, pressed, crushed (crushed) obtained forms (briquettes, strips, ribbons, plate tiles), wiped through one or more screens to obtain particles of a certain size ( calibration), and additionally carry out the pelletizing of the obtained compacted powder with unconsolidated powder. Equipment for its implementation includes sequentially installed feed pre-pressing screw, one or more roller or roller presses with pressing rollers or rollers, a grinder, wiping sieves, plate or tube granulator [RF Patent No. 2613917, IPC B01J 2/22, 2017. ].

 This method allows to obtain granules of spherical shape while maintaining the composition of the processed powder. However, the presence of the grinding operation of the obtained products and the operation of supplying the unconsolidated powder to the pelletizing zone leads to a complication of equipment and an increase in the cost of repairs and maintenance. In addition, the range of granule hardness values measured according to ASTM D5230 is in the range from 0 to 80-100 g, which limits the scope.

The technical result is to simplify the granulation process and equipment while maintaining the spherical shape of the granules, the composition of the processed powder and the hardness of the granules to 100 g, as well as reducing the dispersion of the values of the hardness of the granules.

The technical result is achieved by a method of granulating powders, characterized in that the powder is compacted (pre-pressed), then pressed with a roller or roller press, the rollers or rollers of which have a wavy surface with a mutually arranged protrusion opposite the cavity of the rolls / rollers rotating towards each other, obtained forms (briquettes, strips, tapes, tiles, plates) are wiped through one or more sieves to obtain particles of a certain size (calibration) and carry out rolling the obtained powder.

The powder compaction can be carried out with a cone or cylindrical screw.

The screw rotational speed is preferably maintained in the range from 10 to 100 rpm with a spread of values within ± 5 rpm.

Pressing can be carried out in two ways:

* The pressing pressure is ensured by a predetermined force due to the application of force to the movable axis of the roll (axis of the movable roll / drum, which can move along the direction of application of the pressing force directed from the center of rotation of the movable axis to the center of rotation of the fixed axis), while maintaining the stationary axis of the other roller / drum.

* Pressing pressure is ensured by the size of the gap between the rollers / rollers, the rotation speed of the rollers / rollers and the rotational speed of the screw pre-presser, which provides a change in the amount of powder supplied to the pressing zone between two rolls / rollers rotating towards each other with fixed axes. To increase the force, it is necessary to increase the amount of powder supplied to the seal zone, to reduce the force, it is necessary to reduce the amount of powder supplied to the seal zone. The force on the axis of one of the rolls or rollers is measured by strain gauges.

The preferred range of pressing forces is maintained at a level that provides powder density after pressing, preferably in the range of 1.0 -2.0 kg / dm³and ranges from 10 to 60 kN with a range of forces within ± 10% of the nominal value. For this, the rotation frequency of the rollers (rolls) is maintained in the range from 10 to 100 rpm with a spread of values within ± 5 rpm. For the same purposes, the screw rotational speed is maintained within the above limits: a range from 10 to 100 rpm with a spread of values within ± 5 rpm.

  The pressed powder can be wiped by wiping it through a sieve with a cell from 1.5 to 5 mm.

Pelletization can be carried out on a plate granulator, with a plate rotation frequency of 5 to 40 rpm, a plate diameter of 0.5 to 3 meters, a shoulder height of 0.2 to 1 meter, with a plate rotation axis inclined relative to the horizon by angle from 10 to 55 degrees.

Pelletization can be carried out on a tubular granulator, with a pipe rotation frequency of 5 to 40 rpm, a pipe diameter of 0.3 to 3 meters, a pipe length of 1 to 15 meters, an angle of inclination of the axis of rotation of the pipe relative to the horizon from 1 to 15 degrees.

After rolling, if necessary, it is possible to sort the finished granules, for example, by dispersing them on vibrating screens.

 The difference between the proposed method and the prototype is pressing with a roller or roller press, the rollers or rollers of which have a wavy surface with a mutually arranged protrusion opposite the cavity of the rolls rotating towards each other, as well as the exclusion of the grinding operation and rolling without using compacted powder.

 The technical result is also achieved by a device for implementing the method, including sequentially installed conical or cylindrical screw, one or more roller or roller presses with pressing rollers or rollers having a wavy surface with the possibility of relative positioning of one roller / roller opposite the cavity of another roller / roller during their rotation towards each other, as well as cleaning sieves and a plate or tubular granulator.

Rolls or vylts can have motionless or two or one axis.

The gap between the working surfaces of the rolls or rollers is preferably set to 1 to 5 mm.

In a preferred embodiment, the wiper sieves have cells of 1.5 to 5 mm.

In a preferred embodiment, the axis of rotation of the plate is inclined relative to the horizon by an angle of 10 to 55 degrees, the diameter of the plate is from 0.5 to 3 meters, the height of the shoulder is from 0.2 to 1 meter.

In a preferred embodiment, the angle of inclination of the axis of rotation of the pipe relative to the horizon is from 1 to 15 degrees, the diameter of the pipe is from 0.3 to 3 meters, the length of the pipe is from 1 to 15 meters.

The device may contain screening sieves for separating the obtained granules into fractions.

The device may comprise transport and packaging devices.

The difference between the proposed device and the prototype is that the rolls / rollers have a notch in the form of sequentially alternating protrusions and depressions, made in such a way that the protrusions of one roller during rotation are opposite the depression of another roller, rotating towards it. In addition, the absence of the need to supply uncompressed powder to the pelletizing zone does not require a screw batcher. The device does not contain a chopper.

In FIG. 1 is a diagram of a device containing a disk granulator, where 1 is a conical auger seal; 2 - pressing rolls (rollers); 3 - wiping sieve; 4 - plate granulator.

In FIG. 2 is a diagram of a device containing a tubular granulator, where 1 is a conical pre-press screw; 2 - pressing rolls / rollers) 3 - wiping sieve; 5 - tubular granulator.

In FIG. 3 shows the profile of the working surface of the rolls / rollers and the relative position of the rolls / rollers.

In FIG. 4 (a) and 4 (b), a diagram of providing a given pressing force with two (a) and one (b) fixed axes of rolls / rollers is presented.

The device operates as follows. The powder is fed with a conical or cylindrical screw (1) into the pressing zone between the press rolls / rollers (2), where the powder is pressed into a wavy strip. Then the pressed strip is rubbed through a sieve (3). The resulting mass enters the dish-shaped granulator (4), or a tubular granulator (5), where the spherical granules are rolled.

If it is necessary to separate the granules according to the given sizes, the granules are sorted, for example, on sorting vibrating screens. Granules larger and smaller than the specified size are returned to the wiper sieves, granules of the specified size are fed to the packaging.

A process diagram is shown in FIG. five.

Below are examples of the method using the proposed device.

The starting material is a powder of zinc oxide grade BTs0M GOST 202-84.

Example 1a

Device Operation Mode:

The pressing force on the rollers of the roller press is 60 ± 6kN;

- The diameter of the rollers - 0.9 m;

- Clearance - 5 mm;

- The frequency of rotation of the sealing conical screw 100 ± 5 rpm;

- Roller rotation frequency - 10 ± 5 rpm;

- Wiping sieve with a cell - 4.5 mm;

- Diameter of the plate - 3 m;

- The frequency of rotation of the plate - 5 rpm;

- The angle of the plate - 55 degrees .;

- The height of the plate shoulder is 1.0 m.

Results:

Spherical-shaped granules are obtained having the following characteristics:

Diameter of spherical granules Pellet Hardness ASTM D5230 More than 5 less than 6 mm 7.9% More than 50 less than 60 g 8.2% More than 4 less than 5 mm 50.3% More than 40 less than 50 g 47.2% More than 3 less than 4 mm 32.4% More than 30 less than 40 g 40.1% More than 2 less than 3 mm 7.4% More than 20 less than 30 g 4,5% More than 1 less than 2 mm 2.0% More than 10 less than 20 g 0 Less than 1 mm 0 Less than 10 g 0

- Humidity 0.1%.

- Bulk density 1284 g / dm.

- The chemical composition and specific surface area correspond to the starting material.

Example 1b

Device Modes:

- The pressing force on the rollers of the roller press is 10 ± 1 kN;

- The diameter of the rollers - 0.10 m;

- clearance -1 mm;

- The frequency of rotation of the sealing cylindrical screw 10 ± 5 rpm;

- Roller rotation frequency - 100 ± 5 rpm;

- Wiping sieve with a cell - 1.5 mm;

- Diameter of the plate - 0.5 m;

- The frequency of rotation of the plate - 40 rpm;

- The angle of the plate - 10 degrees .;

- The height of the plate shoulder is 0.2 m.

Results:

Spherical-shaped granules are obtained having the following characteristics:

Diameter of spherical granules Pellet Hardness ASTM D5230 More than 5 mm 0 More than 50 g 0 More than 4 less than 5 mm 0 More than 40 less than 50 g 0 More than 3 less than 4 mm 6.5 More than 30 less than 40 g 16.7 More than 2 less than 3 mm 41.1 More than 20 less than 30 g 33.3 More than 1 less than 2 mm 38.3 More than 10 less than 20 g 35.6 Less than 1 14.1 Less than 10 g 14,4

- Humidity 0.1%.

- Bulk density of 1018 g / dm.

- The chemical composition and specific surface area correspond to the starting material.

Example 2a

Device Modes:

- The pressing force on the rollers of the roller press is 60 ± 6kN;

- The diameter of the rollers - 0.9 m;

- Clearance - 5 mm;

- The frequency of rotation of the sealing conical screw 100 ± 5 rpm;

- Roller rotation frequency - 10 ± 5 rpm;

- Wiping sieve with a cell - 4.5 mm;

- Diameter of a pelletizing pipe - 3 m;

- The frequency of rotation of the pipe - 5 rpm;

- The angle of the pipe - 15 degrees .;

- The length of the pipe is 15 m.

Results:

Spherical-shaped granules are obtained having the following characteristics:

Diameter of spherical granules Pellet Hardness ASTM D5230 More than 5 mm 0 More than 50 g 0 More than 4 less than 5 mm 5.8% More than 40 less than 50 g 6.8% More than 3 less than 4 mm 44.1.3% More than 30 less than 40 g 24.2% More than 2 less than 3 mm 37.1% More than 20 less than 30 g 47.1% More than 1 less than 2 mm 10.8% More than 10 less than 20 g 18.7% Less than 1 mm 2.2% Less than 10 g 3.2%

- Humidity 0.1%.

- Bulk density 1171 g / dm.

- The chemical composition and specific surface area correspond to the starting material.

Example 2b

Device Modes:

- The pressing force on the rollers of the roller press is 10 ± 1 kN;

- The diameter of the rollers - 0.10 m;

- Clearance - 1 mm;

- The frequency of rotation of the sealing cylindrical screw 10 ± 5 rpm;

- Roller rotation frequency - 100 ± 5 rpm;

- Wiping sieve with a cell - 1.5 mm;

- The diameter of the pipe is 0.3 m;

- The frequency of rotation of the pipe - 40 rpm;

- The angle of the pipe - 1 deg .;

- The length of the pipe is 1 m.

Results:

Spherical-shaped granules are obtained having the following characteristics:

Diameter of spherical granules Pellet Hardness ASTM D5230 More than 5 mm 0 More than 50 g 0 More than 4 less than 5 mm 6.2% More than 40 less than 50 g 2.8% More than 3 less than 4 mm 32.9% More than 30 less than 40 g 12.6% More than 2 less than 3 mm 36.8% More than 20 less than 30 g 53.7% More than 1 less than 2 mm 15.4% More than 10 less than 20 g 24.5% Less than 1 mm 8.7% Less than 10 g 6.4%

- Humidity 0.1%.

- Bulk density 1108 g / dm3.

- The chemical composition and specific surface area correspond to the starting material.

Similar results are obtained using a roll press.

Thus, the proposed method allows to obtain spherical granules with preserving the composition of the processed powder and hardness, measured according to ASTM D5230, up to 100 g. The spread (the difference between the maximum and minimum values in the batch) of the granules hardness of the proposed method does not exceed 50 g (in the method prototype up to 80 g). The method does not require the operation of grinding and feeding the unconsolidated powder into the pelletizing zone, which simplifies the process and makes equipment less complicated.

Claims (16)

1. A method of granulating powders, characterized in that the powder is compacted, then pressed with a roller or roller press, the rollers or rollers of which have a wavy surface with a mutually arranged protrusion opposite the cavity of the rolls / rollers rotating towards each other, wiped through one or more screens and carried out rolling of the obtained powder. 2. The method according to claim 1, characterized in that the powder is densified with a cone or cylindrical screw. 3. The method according to claim 2, characterized in that the screw rotational speed is from 10 to 100 rpm with a range of values within ± 5 rpm. 4. The method according to claim 1, characterized in that the frequency of rotation of the rolls / rollers is from 10 to 100 rpm with a range of values within ± 5 rpm. 5. The method according to claim 1, characterized in that the cleaning of the pressed powder is carried out by wiping it through a sieve with a cell from 1.5 to 5 mm. 6. The method according to claim 1, characterized in that the pelletizing is carried out on a plate granulator, with a plate rotation speed of 5 to 40 rpm, a plate diameter of 0.5 to 3 meters, a shoulder height of 0.2 to 1 meter, with the axis of rotation of the plate, tilted relative to the horizon at an angle of 10 to 55 degrees. 7. The method according to claim 1, characterized in that the rolling is carried out on a tubular granulator, with a pipe rotation speed of 5 to 40 rpm, a pipe diameter of 0.3 to 3 meters, a pipe length of 1 to 15 meters, an angle of inclination the axis of rotation of the pipe relative to the horizon from 1 to 15 degrees. 8. The method according to claim 1, characterized in that after pelletizing, sorting the finished granules is carried out, for example, by dispersing them on vibrating screens. 9. A device for implementing the method, characterized in that it includes sequentially installed conical or cylindrical auger, one or more roller or roller presses with pressing rollers or rollers having a wavy surface with the possibility of relative positioning of one roller / roller opposite the cavity of another roller / roller with their movement towards each other, wiping sieves, plate or tubular granulator. 10. The device for implementing the method according to claim 9, characterized in that the rolls or rollers have fixed or two, or one axis. 11. The device according to claim 9, characterized in that the gap between the working surfaces of the rolls or rollers is set from 1 to 5 mm. 12. The device according to claim 9, characterized in that the cleaning sieves have cells from 1.5 to 5 mm 13. The device according to claim 9, characterized in that the axis of rotation of the plate is inclined relative to the horizon by an angle of 10 to 55 degrees, the diameter of the plate is from 0.5 to 3 meters, the height of the shoulder is from 0.2 to 1 meter. 14. The device according to claim 9, characterized in that the angle of inclination of the axis of rotation of the pipe relative to the horizon is from 1 to 15 degrees, the diameter of the pipe is from 0.3 to 3 meters, the length of the pipe is from 1 to 15 meters. 15. The device according to claim 9, characterized in that it contains sorting sieves for separating the obtained granules into fractions. 16. The device according to claim 9, characterized in that it contains transportation and packaging devices.

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