RU2153416C1 - Installation for cryogenic milling of plastics - Google Patents

Abstract

FIELD: fine milling of thermoplastics, applicable in chemical industry, construction and mechanical engineering. SUBSTANCE: the installation has loading bin 1 with metering worm 2, cooling chamber 3, metering worm 4 for feeding the material from the cooling chamber to the mill, mill 5, collector of finished material 21 with a calibrating grate, dust filter 27 with a fan for removal of gaseous nitrogen from the mill. The mill has body 8 with tapered member 9 located inside the body and aligned with it, rigidly fitted on pipe 10 with a lateral hole in lower part 11. Worm 12 is positioned inside the pipe on sliding supports 13, 14, the upper part of the worm axle through flexible part 15 is linked with the body through diaphragm 16 with holes 17 for passage of material, and the lower part of the pipe through flexible part 18 and shaft 19 is linked with rotation drive 20. Two calibrating grates 22, 23 are installed one above the other in finished material collector 21. The space between the calibrating grates is connected to bin 24 for collection of narrow fraction. The finished material collector in the lower part is connected to hot granulation granulator 25 with cooling by gaseous nitrogen, which at the same time serves for transportation of granulite to cyclone separator 29 connected in the lower part to the cooling chamber through metering worm 30. Fan 26 for removal of gas formed as a result of evaporation of liquid nitrogen from the system serves for cooling and transportation of granulite of hot granulation installation 25. EFFECT: production of narrow fraction of milled material without production of byproducts. 1 dwg

Description

 The invention relates to fine grinding of thermoplastics and can be used in the chemical industry, construction and engineering.

 Known shredders: and.with. 1825657, a.s. 1,755,915; mill activator: a. with. 1796255, which consist of a body and a conical mass rotating inside it.

 These devices are not effective when grinding plastics with high heat sensitivity, as well as if it is necessary to obtain a narrow fraction of the crushed material.

 The closest technical solution is the installation for cryogenic grinding of plastics (EL Kalinchev. The current state and development trends of equipment for granulating and grinding plastics in the USSR and abroad. O. I. TSINTIneftekhimmash. M .: - 1975. 65 pp.), containing a loading hopper with a metering screw, a cooling chamber, a metering screw for feeding material to the mill, valves for supplying liquid nitrogen to the cooling chamber and for cooling the mill, mill, a collection of finished material with a calibrating grate, dust fi tr with a fan for the removal of nitrogen gas.

 However, the described installation does not allow to effectively isolate a narrow fraction of crushed thermoplastics. The present invention solves the problem of obtaining a narrow fraction in the grinding of thermoplastics with simultaneous processing of particles of larger and smaller sizes.

 This is achieved by the fact that in the installation for cryogenic grinding of plastics, a mill is used that contains a housing with a cone-shaped element rotating inside, rigidly axially mounted on the pipe with a side hole in the lower part and a worm located inside the pipe, the axis ends of which are in sliding bearings, while the upper part of the axis of the worm is provided with a screen and through the flexible part is connected to the housing through a diaphragm with holes for material passage, and the lower part of the pipe through the flexible part and shaft is connected to the rotary drive In the finished material collector, two calibrating gratings are installed one above the other, while the space between the calibrating gratings is connected to a hopper for collecting a narrow fraction, and the finished material collector in the lower part is connected to a granulation granulator with nitrogen gas, which simultaneously serves to transport the granulate into a cyclone connected in the lower part through a metering screw to the cooling chamber, while the fan is used to remove liquid formed as a result of evaporation from the system Zot gas is used for cooling and conveying installation hot granulation granulate.

 Comparative analysis with the prototype showed that the inventive installation for cryogenic grinding of plastics differs from the known one by the presence of an additional calibrating grate in the collection of finished material, which allows you to select a narrow fraction of the crushed material. The presence of the granulator allows the dispersed part of the crushed material to be returned for return, using gaseous nitrogen from the mill cooling. The presence of a worm inside a cone-shaped element allows larger particles to be returned to the inside of the mill through a hole in the pipe.

 The invention is illustrated in the drawing. Installation for cryogenic grinding consists of a loading hopper 1 with a metering screw 2 for feeding material into the cooling chamber 3 with a metering screw 4 for feeding material into the mill 5, valves 6,7 for feeding liquid nitrogen to the cooling chamber 3 and for cooling the mill 5, containing the housing 8 with a rotating inside the conical element 9, rigidly axially connected to the pipe 10 with a side hole in the lower part 11 for the passage of large particles. Inside the pipe 10 there is a worm 12, which serves to lift and return large-sized particles to the mill to the mill. The ends of the axis of the worm 12 are located in the sliding bearings 13, 14. In this case, the upper part of the axis of the worm 12 has a screen, is extended beyond the pipe and connected through the flexible part 15 to the mill body through the diaphragm 16 with openings 17 for passing material entering the mill for grinding. The lower part of the pipe through the flexible part 18 and the shaft 19 is connected to the rotation drive 20. In the finished material collector 21, two calibrating gratings 22, 23 are mounted one above the other. The space between the calibrating gratings is connected to the hopper 24 for collecting a narrow fraction. The lower part of the hopper 21 is connected to a granulator of hot granulation 25. To cool the granules formed after forcing the material in a visco-plastic state through dies and cutting with a knife, a fan 26 is used, which draws out gaseous nitrogen from the mill through a dust filter 27. The granulator 25 is connected by a pipe 28 to a cyclone 29 for feeding granular material into it. The cyclone 29 has a metering screw 30 at the bottom for feeding granules into the cooling chamber 3.

 Installation for cryogenic grinding of plastics works as follows. When the metering worm 2 is turned on, material from the feed hopper 1 enters the cooling chamber 3, into which liquid nitrogen is supplied through the valve 7. From the cooling chamber 3, the material is dispensed by the metering worm 4 through openings 17 to the diaphragm 16 to mill 5. To cool the mill, it is additionally fed through valve 6 liquid nitrogen. When you turn on the drive rotation of the mill 20 through the shaft 19, the flexible part 18, the pipe 27 comes into rotation conical element 9 and enters the rolling mode inside the housing 9, so the shaft 19 has a flexible part 18; while the worm 12 does not rotate, since it is connected to the diaphragm 16 and does not interfere with the lateral displacement of the internal cone-shaped element (in the rolling mode) due to the presence of the flexible part 15. The cooled material, passing the space between the mill body 8 and the cone-shaped element 9, is crushed and gets into the collection of finished material 21 on the upper grating 22. Large particles of material that did not pass the grating 22 through the hole 11 in the pipe 10, rotating together with the conical element 9, return to the worm 12 the upper part of the mill for regrinding. The dispersed part is separated from the material that has passed through the upper calibrating grating 22, using the calibrating grating 23, which enters the lower part of the hopper 21. A narrow fraction enters the hopper 24. The dispersed part of the material from the lower part of the hopper 21 enters the hot granulation granulator 25, in which the plasticized material is extruded from the granulating head through a forming grid with holes. The rods emerging from the holes are cut with a knife on the plane of the grill. The head and knife are enclosed in a tight chamber. To prevent deformation of the granules and their adhesion into lumps, a stream of nitrogen gas is passed from the fan 26, through which the granules are transported through a pipe 28 to the cyclone 29 and fed into the cooling chamber 3 through a metering screw 30. The fan 26 draws out nitrogen gas through a dust filter 27 from the finished material collector 21 .

 Thus, the proposed installation for cryogenic grinding of plastics allows to obtain a narrow fraction of the crushed material without obtaining by-products.

Claims (1)

 Installation for cryogenic grinding of plastics, containing a loading hopper with a metering screw, a cooling chamber, a metering screw for feeding material from the cooling chamber to the mill, mill, a finished material collector with a calibrating grate, a dust filter with a fan for removing nitrogen gas from the mill, characterized in that the mill comprises a housing with a conical element located coaxially with the inside of the housing, rigidly axially mounted on the pipe with a side opening in the lower part and located inside pipes in sliding bearings with a worm, the upper part of the axis of which is connected through a flexible part to the body through a diaphragm with holes for passing material, and the lower part of the pipe through a flexible part and shaft is connected to a rotation drive and two calibrating gratings are installed one above the other in the collector of finished material, the space between the calibrating gratings is connected to the hopper for collecting a narrow fraction, and the finished material collector in the lower part is connected to a granulator of hot granulation with cooling with gaseous nitrogen m, which simultaneously serves to transport the granulate into a cyclone connected in the lower part through a metering screw to the cooling chamber, while the fan to remove gas formed from the evaporation of liquid nitrogen from the system serves to cool and transport the granulate of the hot granulation unit.