WO2010053397A1

WO2010053397A1 - A method to grind polymeric substances and a device to perform it

Info

Publication number: WO2010053397A1
Application number: PCT/RU2008/000698
Authority: WO
Inventors: Peter Nikitievich Kozlov
Original assignee: YUNITA-M Ltd
Current assignee: YUNITA-M Ltd
Priority date: 2008-11-10
Filing date: 2008-11-10
Publication date: 2010-05-14
Anticipated expiration: 2011-05-10

Abstract

This invention relates to mechanical engineering, in particular, to the devices for grinding fragile polymeric substances with different physicochemical properties, and can be applied in chemical, building industry, medicine, food and light industry, etc. The method implies the combination of cyclone, jet, centrifugal, axial and cyclonic-jet methods to grind fragile or cooled to the fragile state polymeric substances. The device comprises a refrigerated space; an accelerating block in the form of the first swirl chamber; a rotor with the centrifugal and axial-type blades, the rotor being combined with second swirl chamber housing; a separator and a cyclone; gas mains with valves and a fan. Application of this method and the device to perform it allows solving the problem of the efficient grinding of polymeric substances with different physicochemical properties, to the required degree of dispersion and grain size classification.

Description

A method to grind polymeric substances and a device to perform it

Technology area

This invention relates to mechanical engineering, in particular, to the devices for grinding fragile polymeric substances. The object of the invention is the method of fine grinding of fragile particles of polymeric substances, including elastic and viscous ones that were brought to the fragile state and the device to perform it.

Previous level of technology

A device to grind material (1) is known; the device comprises a centrifugal mill, a separator, a flap, a cyclone receiver for the final product. To improve the quality of separation, the device has an additional cyclone built in the upper part of the separator.

A high speed grinding in the percussion-type machines at the medium low temperatures to obtain polymer powder is known (2, 3, 4).

A method of cryogenic grinding is known, where a vibrating mill for plastics grinding contains a milling compartment connected to a vibratory drive (5).

A method of continuous cryogenic grinding of materials (plastics, rubber, metals, foodstuff) is known, where the materials are precooled by liquid nitrogen and are ground in hammer or rotary grinders (6).

The major drawbacks of the prototypes are unreliable operation, poor efficiency when obtaining the required quality and grain size distribution of the required products.

Description and Methods of implementation

The basis of the invention is the task of eliminating the above-mentioned drawbacks. As concerns the method, the assigned task is solved as follows. A combination of cyclonic, jet, centrifugal, axial and cyclonic-jet grinding methods are applied, while the material particles are being accelerated in a pulsating flow and are being ground in the first swirl chamber; then they are being injected to the plane of rotation of the centrifugal- type shoulder blades orthogonally or at an angle. Then the particles are being accelerated by a centrifugal method and injected to the plane of rotation of the axial-type shoulder blades, and then to the second swirl chamber. In this case the task can be solved as follows. The material particles are being accelerated and injected to the plane of rotation of the axial-type shoulder blades at an angle, for the first strike against the blades; then the material particles are being accelerated by a centrifugal method along the shoulder blades from the blades root section to the blade tips, while injecting their vortex flows between the perforated stator housing and the blade tips and for the second strike against stationary stator blades.

In this case the optimum angle to inject the material particles and their absolute velocity is selected according to the circumferential velocity of the blade rotation, to the blade pitch and width to increase the grinding efficiency. The preliminary cryocooling of the feed stock is applied to impart fragility, to form defects in the bulk of the material particles (these defects help reducing grinding costs), and unground cooled material particles are being returned to the input precooling charge capacity and are being mixed with uncooled material to be ground to reduce cooling agent consumption. Gas flow rotation is applied, where the gas flow carries the particles of ground material. A part of the flow is extracted to obtain the speed of the flow necessary for the particles separation. The extraction is performed using an angle-deviated blade in the lower part of the rotor and a main to remove gas with small particles of the finished product, via the adjustable valve. Big material particles that fall into the receiver are returned for grinding. As concerns the device, the assigned task is solved as follows. The device is equipped with an accelerating block in the form of the first swirl chamber, where the material particles are being ground and fed to the inlet of the centrifugal shoulder blades and to the axial shoulder blades orthogonally or at an angle. The material particles are being ground there, and then moved to the second swirl chamber for final grinding and for output to the separator and cyclone. The device can be equipped with a mill with axial-type blades with specially designed elements of the mill air-gas channel and the accelerating block of the particle input with the specified speed and angle relative to a normal line to the plain of the blade rotation, for the first strike against the specified section of the rotating blades, while the stationary stator elements are placed in the area of the material particles output from the blades to the area of the vortex flows, and for the second strike. Under the stationary stator elements there is a receiver of the falling ground material particles, with the mains to extract the latter to the separator and cyclone. The inlet to the accelerating tube housing can be made as an articulated joint with the variable angle of direct jet or swirl nozzle. The accelerating block can be made as a direct jet or swirl ejector.

In front of the accelerating block there is an installed refrigerated space with the collector of the inlet of a cooling agent, through the nozzles placed incrementally and at a certain angle. The cooling agent generates the swirling motion of the embrittled material particles and the acoustic vibrations in the reservoir. The refrigerated space also has a leak-proof sealing leg to feed the material through the cone fairing, in the center of which there is an installed main with the pressure pulsator, to extract gas to the embrittlement and activation zone, and through the second sealing leg to the accelerating device. The separator can be combined with the material particles outlet from the axial blades in the housing of the second swirl chamber. The essence of the invention is explained by the drawings (fig.l) of the suggested device, which contains the following: rotary discharger (1) to load the initial product to the loading hopper (2) with the mains to supply the underground material and cold gas and to remove waste gas into the atmosphere; rotary discharger (3) to insert the precooled particles to the refrigerated space (4), in which the particles get, via the fairing (5), into the area of acoustic, cyclone and pulsating perturbations generated by the pulsator (6) also; the cooled material is being tangentially fed, via the batcher (8), to the first perforated swirl chamber (9), where the particles are accelerated by the tangentially injected pulsating gas flow from the refrigerated space; nozzle (10) to inject the particles through the profile insertion (11) to the inlet of the centrifugal perforated blades (12); axial perforated blades (13); second perforated swirl chamber (14), where the centrifugal (12) and axial (13) blades are combined, with the outlet for ground (15) and underground (16) material particles; separator (17) and cyclone with the hopper (18); gas mains with valves (19) and fan C. The suggested method to grind polymer materials and the device to perform it imply the following. The material particles undergo blast cooling in the refrigerated space till they become fragile. As a result of the mutual particles collision and their collision with the perforated reservoir walls, and activation by acoustic vibrations, microcracks and other defects occur in the bulk of the material particles, where these defects facilitate particles destruction at lower costs. Material particles activated for the destruction are being accelerated by the pulsating cooling agent flow in the first perforated swirl chamber, where they are being ground partially. The accelerated particles pass the area of intensive vortexes through the nozzle, orthogonally to the plane of rotation of centrifugal and axial perforated blades, and parallel to it. With the strike against the insertion and the centrifugal blades, the particles get to the axial blades with the acceleration and a strike.

100 Further grinding takes place in the air-gas channel in the area of vortex flow, due to the mutual particles collision and their collisions with blades. The material particles that possess circumferential and axial velocity undergo final grinding in the second swirl chamber. At the outlet of the second swirl chamber, ground particles are fed to the separator, where the particles of the required fraction are selected and fed to the cyclone

105 to be separated from the gas medium, while big particles are returned to the loading hopper for regrinding. A built-in separator can be installed at the outlet of the second swirl chamber. In this case small particles are selected for the cyclone in the upper part of the separator, while big ones are collected for the loading hopper or for the inlet of the first swirl chamber from the lower part of the separator. It should be noted that the range

110 of the selected small fractions can be increased and the costs for further particles grinding can be reduced when using the first swirl chamber as a cyclone or a vortex tube. The following method can be used as a component part of the above-mentioned method in some cases. The essence of this method and the device to implement it is explained by the drawings of the device (fig.2), which contains batcher (1) to load the initial product;

115 loading hopper (2), also used to precool the material particles; batcher (3) and refrigerated space (4), with cone fairing (5), collector to inject the cooling agent (7) and pulsator (6); batcher to extract embrittled particles (8) and the accelerating device (9) made as a direct jet ejector; grinding mill (10) with axial-type blades (11) and hopper to collect ground particles (12); separator (13) and cyclone (14); gas mains with valves (15) and fan C.

120 The suggested specific method to grind polymeric substances and the device to perform it imply the following. The embrittled particles are being accelerated in. the device and directed to the root section of the axial blades turned through 180°, via the nozzle hingedly mounted in the grinding mill housing, for the first percussion. Then the material particles are being centrifugally accelerated and injected into the vortex flows that occur

125 between the blade tips and the perforated grinding mill housing, and then to the stator blades for the second percussion. Following this the ground material particles are being fed to the separator, where big particles are sent for regrinding, while small ones are sent to cyclone to separate them from the gas medium. The separator can be built in the grinding mill housing.

Claims

The Invention Formula

1. A method to grind fragile or cooled to the fragile state polymeric substances with the material particles acceleration and collision against the grinding mill blades, the method being notable because it applies the combination of cyclone, jet, centrifugal, axial and cyclonic-jet grinding methods, and the material particles are being accelerated in the pulsating gas flow and are being ground in the first swirl chamber, and injected to the plane of rotation of the centrifugal-type shoulder blades orthogonally or at an angle. Then the particles are being accelerated by a centrifugal method and injected to the plane of rotation of the axial-type shoulder blades, and then to the second swirl chamber.

2. The grinding method as per clause 1, with the following difference. The material particles are being accelerated and injected, at an angle, to the plane of rotation of the axial-type blades for the first percussion; then the material particles are being accelerated by the centrifugal method along the blades from the root section to the blade tips and are being injected into the vortex flows between the perforated stator housing and the blade tips, for the second collision against the stationary stator blades.

3. The grinding method as per clauses 1, 2, with the application of preliminary cryocooling of the elastic and viscous material particles, to the fragile state, with the following difference. The pressure is being increased during the heat transfer between the cooling agent and the material particles, to the level required to accelerate the particles to the specified velocity and to eliminate the gas-dynamic losses during the particles transportation.

4. The grinding method as per clause 3, with the following difference. To intensify the heat transfer, to destruct the material particles, to eliminate the particles sealing and arching at the outlet of the refrigerated space, vortex flows, pressure pulsations and suspended layer of the material particles are being generated in the refrigerated space.

5. The grinding method as per clauses 3, 4, with the following difference. To intensify the heat transfer, to reduce costs for further grinding of the cooled particles and to increase the grinding efficiency, to eliminate the particles sealing and arching at the outlet of the refrigerated space, the cooling agent rotation, acoustic vibrations, mutual particles collision and their collision with the refrigerated space walls, boiling bed of the material particles are being generated in the refrigerated space.

6. The grinding method as per clause 3, with the following difference. To reduce cooling agent costs and increase the grinding efficiency, waste gaseous cooling agent and unground cooled material particles are being returned to the precooling charge capacity and mixed with the uncooled material to be ground.

7. The grinding method as per clause 2, with the following difference. To increase the grinding efficiency, an optimal angle to inject particles and their absolute velocity are selected according to the circumferential velocity of the axial rotor blades rotation, to the spacing and width of the blades, and to the physicochemical properties of the initial and ground material.

8. The grinding method as per clause 1, with the following difference. To increase the grinding efficiency, the unground particles are fed to the first swirl chamber.

9. The grinding method as per clause 1, with the following difference. To increase the grinding efficiency, small material particles are selected from the first swirl chamber.

10. The grinding method as per clause 1, with the following difference. To increase the grinding efficiency, the refrigerant gas is being fed tangentially to the second swirl chamber.

11. The grinding method as per clause 1, with the following difference. To increase the grinding efficiency, the surfaces of the swirl chambers, centrifugal and axial blades are perforated, while cyclone and acoustic perturbations are being generated at the inlet of the centrifugal blades.

12. The grinding method as per clause 1, with the following difference. The centrifugal, axial rotors and second swirl chamber are combined in single housing.

13. The grinding method as per clause 1, with the following difference. The gas flow rotation is applied at the outlet of the second swirl chamber, where the gas carries the ground material particles, and a part of the flow is extracted to obtain the speed of the flow necessary for the particles separation. The extraction is performed using an angle- deviated blade in the lower part of the rotor and a main to remove gas with small particles of the finished product, via the adjustable valve. Big material particles that fall into the receiver are returned for grinding.

14. The grinding method as per clauses 1, 9, with the following difference. To increase the grinding efficiency, small material particles are being selected from the first swirl chamber, while big ones are being fed to the inlet of the centrifugal blades in the rotating gas flow.

15. A device to perform grinding of fragile or cooled to fragile state polymer substances according to clause 1. The device contains loading hopper, centrifugal mill, separator, a main with a valve, cyclone with the final product receiver, and differs in the following characteristics. The devices is equipped with the first swirl chamber, where the material particles are being ground and fed with the specified speed to the inlet of the centrifugal blades and to the axial blades, orthogonally or at an angle. The material particles are being ground there, and are then being fed to the second swirl chamber for final grinding and for output to the separator and to the cyclone.

16. A device as per clause 2, with the following difference. The device is equipped with the centrifugal mill with the axial type blades, with specially made flow section elements and with an accelerating block to inject particles at a specified speed and angle relatively to the normal line to the blade rotation plane, for the first collision against the specified section of the rotating blades. The stationary stator elements are placed in the area of the material particles output from the blades to the area of the vortex flows, and for the second strike. Under the stationary stator elements there is a receiver of the falling ground material particles, with the mains to extract the latter to the separator and cyclone.

17. A device as per clause 16 to implement the method as per clause 2, with the following difference. The accelerating block is made as an accelerating tube with a mixer at the beginning, where a dispenser to feed the fragile material particles and mains to supply the 100 compressed cool gas are being connected to the mixer.

18. A device as per clauses 3, 4, 5 to implement the methods as per clauses 1, 2, with the following difference. In front of the accelerating block there is an installed refrigerated space with the collector of the input of a cooling agent, through the nozzles placed

105 incrementally and at a certain angle. The cooling agent generates the swirling motion of the embrittled material particles and the acoustic vibrations in the reservoir. The refrigerated space also has a leak-proof sealing leg to feed the material through the cone fairing, in the center of which there is an installed main with the pressure pulsator, to extract gas to the material particles cooling and activation zone, and through the second

110 sealing leg to the accelerating device in the form of a swirl chamber.

19. A device as per clause 7 to implement the method as per clause 2, with the following difference. The inlet of the housing of the accelerating tube mill is made as a leak-proof joint with an adjustable angle of the gas flow with embrittled material particles, relatively

115 to the normal line to the blade rotation plane.

20. A device as per clause 8 to implement the method as per clause 1, with the following difference. Big particles selected from the separator, are being fed to the inlet of the first swirl chamber operating as a vortex ejector.

120

21. A device as per clause 8 to implement the method as per clause 1, with the following difference. The preliminary ground material particles are being selected from the central part of the first swirl chamber operating as a cyclone.

125 22. A device as per clause 13 to implement the method as per clause 1, with the following difference. The first swirl chamber is made as a vortex tube; the ground material particles are being selected through the cold end of the tube, while the rotating big particles are being fed to the inlet of the centrifugal blades through the hot end.