Abstract:
The present invention relates to a method for the pelletization of plastics and/or polymers, wherein a melt coming from a melt generator is supplied via a diverter valve having different operating positions to a plurality of pelletizing heads through which the melt is pelletized. The invention furthermore relates to a pelletizing apparatus for the pelletization of plastics and/or polymers having a diverter valve which has at least one melt generator connection, at least two pelletizer connections as well as a switching gate for selectively connecting the melt generator connection to at least one of the pelletizer connections, with a respective pelletizing head being connected to the at least two pelletizer connections and a melt generator having a variable melt volume flow being connected to the melt generator connection. Finally, the invention also relates to a diverter valve for such a pelletizing apparatus having a melt generator connection, a pelletizer connection as well as a melt passage for the connection of the melt generator connection to the pelletizer connection. The present invention therefore starts from the idea of using a plurality of pelletizing heads with different passage capacities and of hereby enlarging the throughput window to be able to work largely continuously without intermediate interruptions and to shorten unavoidable start-up processes by switching in pelletizing heads having small throughput capacities or to minimize them with respect to the start-up products which occur. In accordance with an aspect of the present invention, a plurality of pelletizing heads having different throughput capacities are used sequentially for the start-up of the pelletizing process, with the melt first being supplied to a first pelletizing head having a smaller throughput capacity and then the melt volume flow being increased and the diverter valve being switched over such that the melt is diverted by the diverter valve to a second pelletizing head having a larger throughput capacity. The time and thus the amount of the start-up product until the melt generator reaches the lower throughput limit of the pelletizing head and the pelletizing process can be started are cut by the use of initially one pelletizing head having a throughput capacity which is as low as possible. No further start-up product is incurred from the start onwards of the pelletizing process at the lower throughput limit of the said first pelletizing head. The melt volume flow is increased quantitatively for so long until the diverter valve can be switched to the second pelletizing head having the larger throughput capacity with no start-up product being incurred during this time period. Moreover, the throughput window is enlarged in total so that the number of unavoidable start-up procedures with start-up product arising therein is reduced since it is possible, on a ramping down of the melting performance below the lower throughput limit of the larger pelletizing head which may become necessary for various reasons, to switch back to the first pelletizing head.
Abstract:
A cutter hub and blade assembly supported and driven for rotational and axial movement in relation to the die face of a die plate in an underwater pelletizer including a positive control of such axial movement to obtain and maintain optimal axial position of the cutter hub and blades during the pelletizing operation and to minimize wear of the mechanical components involved. Positive control of the axial movement of the cutter hub and blades is obtained by a hydraulic/pneumatic actuation system controlling an elongated motion rod that extends through a driven hollow motor shaft. One end of the motion rod is connected with a hydraulic/pneumatic control and the other end of the rod is connected to a cutter hub holder that supports the cutter hub and blades for axial movement toward or away from the die face.
Abstract:
A filtration apparatus for filtering and separating solids from liquids is provided that includes at least one liquid-permeable, continuously or intermittently drivable filter belt, an intake for charging the liquid/solid mixture to be filtered onto the filter belt in a charging zone and a belt cleaner for removing the solids deposited at the filter belt from a belt section conveyed out of the charging zone in an expulsion zone. The belt cleaner has at least one rotatingly drivable brush with which a brush cleaner having a scraper is associated which is arranged in the path of the bristles of the rotating brush. The rotating brush efficiently removes the deposited solids from the filter belt, while the scraper of the brush cleaner simultaneously ensures that the dissolved solids do not settle at the brush and clog it.
Abstract:
A pelletizer, preferably in the form of an underwater pelletizer, having a cutter and/or grinding head and a tool carrier is provided. The tool carrier can rotatably be driven about a tool carrier axis of rotation, and at least one cutting and/or grinding tool, which is attached to the tool carrier and is spaced from the tool carrier axis of rotation, is used to knock off plastic melt emerging from a pelletizer die plate and/or for grinding the pelletizer die plate. In one embodiment, the cutting and/or grinding tool rotates together with the tool carrier about its tool carrier axis of rotation, and in another embodiment, the cutting and/or grinding tool can rotate about its own axis of rotation relative to the tool carrier.
Abstract:
A method and apparatus for underwater pelletizing and subsequent drying of crystallizing polymers to crystallize the polymer pellets without subsequent heating is shown in FIG. 5. High velocity air or other inert gas is injected into the water and pellet slurry line (120) toward the dryer near the pelletizer exit (102) at a flow rate of from about 100 to about 175 m3/hour, or more. Such high-speed air movement forms a vapor mist with the water and significantly increases the speed of the pellets into and out of the dryer such that the polymer pellets leave the dryer with sufficient latent heat to cause self-crystallization within the pellets. A valve mechanism in the slurry line (150) after the gas injection further regulates the pellet residence time and a vibrating conveyor after the dryer helps the pellets to achieve the desired level of crystallinity and to avoid agglomeration.
Abstract:
A method and apparatus for underwater pelletizing and subsequent drying of polyethylene terephthalate (PET) polymers and other high temperature crystallizing polymeric materials to crystallize the polymer pellets without subsequent heating. High velocity air or other inert gas is injected into the water and pellet slurry line to the dryer near the pelletizer exit. The slurry line has a substantially straight component, and air is preferably injected at the end of the straight component nearest the pelletizer exit and in a direction substantially coincident with the axis of the straight component. The air injection significantly increases the speed of the pellets into and out of the dryer such that the PET polymer pellets leave the dryer above at least 135° C., and preferably above 145° C., to self-initiate crystallization.
Abstract:
Certain polyamide beads or granules are useful as a sustaining material for underground natural or artificial cracks of the earth's crust essentially employed for the extraction of hydrocarbons such as crude oil or natural gas; such polyamide beads have a spherical or ellipsoidal shape and have a surface free of concave portions, advantageously having a uniform shape, and having a mean diameter lower than or equal to 1.7 mm and a porosity lower than 0.1 ml/g, and are produced using a particular cutting device/extruder.
Abstract:
The present invention relates to a pelletizer, preferably in the form of an underwater pelletizer. In particular, this invention relates to a cutter and/or grinding head for such pelletizer, comprising a tool carrier which can rotatorily be driven about a tool carrier axis of rotation, and at least one cutting and/or grinding tool, which is attached to the tool carrier and is spaced from the tool carrier axis of rotation, for knocking off plastic melt emerging from a pelletizer die plate and/or for grinding said pelletizer die plate. In accordance with the invention, the cutting and/or grinding tool is rotatably mounted on the tool carrier about an axis of rotation spaced from the tool carrier axis of rotation. This provides a second component of movement for the cutting and/or grinding tool. On the one hand, the cutting and/or grinding tool rotates together with the tool carrier about its tool carrier axis of rotation, and on the other hand, the cutting and/or grinding tool can rotate about its own axis of rotation relative to the tool carrier. The tool carrier has a pivot bearing for the cutting and/or grinding tool, by means of which the cutting and/or grinding tool can rotate about itself.
Abstract:
A method and apparatus for underwater pelletizing and subsequent drying of polyethylene terephthalate (PET) polymers and other high temperature crystallizing polymeric materials to crystallize the polymer pellets without subsequent heating. High velocity air or other inert gas is injected into the water and pellet slurry line to the dryer near the pelletizer exit. Air is injected into the slurry line at a velocity of from about 100 to about 175 m3/hour, or more. Such high-speed air movement forms a vapor mist with the water and significantly increases the speed of the pellets into and out of the dryer such that the PET polymer pellets leave the dryer at a temperature sufficient to self-initiate crystallization within the pellets. A valve mechanism in the slurry line after the gas injection further regulates the pellet residence time and a vibrating conveyor after the dryer helps the pellets to achieve the desired level of crystallinity and to avoid agglomeration.
Abstract:
A method and apparatus for underwater pelletizing and subsequent drying of polyethylene terephthalate (PET) polymers and other high temperature crystallizing polymeric materials to crystallize the polymer pellets without subsequent heating. High velocity air or other inert gas is injected into the water and pellet slurry line to the dryer near the pelletizer exit. The slurry line has a substantially straight component, and air is preferably injected at the end of the straight component nearest the pelletizer exit and in a direction substantially coincident with the axis of the straight component. The air injection significantly increases the speed of the pellets into and out of the dryer such that the PET polymer pellets leave the dryer above at least 135° C., and preferably above 145° C., to self-initiate crystallization.