DE19926035B4 - Process and apparatus for the separation of polymer granules after granulation - Google Patents

Abstract

A process for the separation of oversizes and malformations arising in the granulation of polymer by means of underwater granulation, underwater strand granulation or strand granulation, characterized in that
the granules
is introduced directly from an underwater granulation with the liquid via a circuit in a liquid-filled separator for oversize on the above-arranged inlet nozzle (1),
or with the working fluid of an underwater strand granulation in a container
or without working fluid in the container filled with liquid
and then transferred to the separator,
in the separator, the oversizes are deposited by means of a screen plate (3) inclined in the direction of flow,
wherein the granules fall through the perforation of the sieve plate (3) into a collecting space (4) and from there via an outlet nozzle (6) is derived with a liquid flow,
the oversizes at the end of the sieve plate fall into a collecting space (7),
the sockets (1) and (6) are closed,
the liquid from the collecting chamber (7) via a drainage nozzle ...

Description

• – Verfahren der Unterwasser-Granulierung (UWG)
• – Verfahren der Unterwasser-Strang-Granulierung (USG)
• – Verfahren der Strang-Granulierung (SG)

In the production of polymers, the melt produced in the polymerization is usually solidified in the granulation process section and cut into granules. Three methods are generally used for this:

• - Underwater Granulation Process (UWG)
• - Underwater Strand Granulation Process (USG)
• - Method of strand granulation (SG)

At the UWG process, the melt passes through immediately after the reactor Nozzle holes pressed and cut under water from a cutting unit to defined granules. The granules are then detected by the upcoming water flow, solidified and forwarded.

• – Das Granulat-Flüssigkeits-Gemenge strömt beim UWG- und USG-Verfahren in einen Abscheider zur Abscheidung der Betriebsflüssigkeit vom Granulat und erfährt anschließend mittels entsprechender Ausrüstungen eine aktive Oberflächentrocknung an Luft. Danach wird das Granulat auf eine Vibrationssiebmaschine geleitet, die gewöhnlich mit einer ca. waagerecht angeordneten Siebplatte versehen ist, auf der an der Luft die Abscheidung der Übergrößen vom Granulat erfolgt.
• – Das Granulat wird nach der Abscheidung der Übergrößen allgemein wieder in einen Behälter eingeführt, der mit Flüssigkeit, gewöhnlich Wasser, gefüllt ist. Das Granulat wird von hier an wieder unter Luftabschluss geführt und weiterbehandelt.

In the USG process, the melt exits the nozzle bores in the form of strands, which then slide in air on a baffle and are cooled and solidified here by applied water. Thereafter, in the granulator, the cut of the solid strands to granules. In the SG process, the cooling and solidification of the polymer melt takes place in an open water bath. The solid strands are then fed to granulators and cut into granules. The three methods have the peculiarity that, in particular when the granulators are started up, particles of oversize and defective forms are formed which must be separated before the granules are conveyed to the further processing stages. The solution used for this deposition is generally the following method:

• - The granulate-liquid mixture flows in the UWG and USG process in a separator for separating the operating fluid from the granules and then experienced by means of appropriate equipment an active surface drying in air. Thereafter, the granules are passed to a vibrating sieve, which is usually provided with an approximately horizontally arranged sieve plate, on which takes place in the air, the oversize of the granules.
• - The granules are generally reintroduced into a container filled with liquid, usually water, after the oversize is removed. The granules are led from here again under exclusion of air and further treated.

The Method of surface drying after The granulation is therefore necessary because subsequently the Separation of the oversized granules done on the vibrating screen in a dry classification in the atmosphere. The surface drying The goal here is to exclude lumps of granulate produced by adhesion as a result of current Liquid arise and that would interfere with optimal deposition (ejection of granules in the oversize fraction).

This means additional Expenses in terms of equipment, energy and operational aspects. Mostly this also arises in addition an emission of polymer abrasion by the forcible and intense Friction of granules on separation walls, the further processing of the product and sales in the production of high quality reduced quality product. In addition, occurs with respect to the UWG procedure one unnecessary forced opening of the granules to the atmosphere with disadvantages with respect to possible oxidative damage is connected and avoided with the method and apparatus according to the invention can be.

In DE-OS 35 15 891 A1 discloses a screening device at atmospheric operation presented for separating solid-liquid mixtures into solid and liquid is used. The deposition takes place first in a spiral inlet area, in which the mixture is introduced tangentially via nozzles at high speed is, and then in a strainer, consisting of several conical rings is composed with the tapering downwards Diameter are executed. The rings have successively an increasing angle against the perpendicular. The task is on the whole Sieve surface one to achieve optimum screening effect.

For the in object of the present invention for the separation of oversize polymer granules is the design of steps with decreasing inclination on the flow path not suitable, because this is to deposits of oversize and stowing in it Lead granules can. Furthermore is a rotationally symmetric screen body unfavorable for this task and consuming. The entry of the goods via nozzles in a spiral inlet area is for this just as disturbing and consuming, since usually resulting in the granulation of polymer oversizes irregular shapes have the nozzles would clog. Besides, they are for the Separation of oversizes from Granules have an optimal low velocity of the solid as well a suitable angle of inclination of the screen surface is essential. A possible application of deposition presented here in the open atmosphere for the deposition from oversizes Polymer granules would in addition to the disadvantages mentioned above, an upstream active surface drying of the polymer require, as already listed above, consuming is.

• – eine Einrichtung zur Beschickung des Siebes,
• – eine mechanisch angetriebene kreisförmige Siebfläche mit mehreren langgestreckten, radial überstehenden Gliedern,
• – eine an den Außenumfang der Siebfläche angrenzende erste Sammeleinrichtung für das Übergrößenmaterial,
• – eine unter der Siebfläche angeordnete zweite Sammeleinrichtung für das Untergrößenmaterial,
• – eine unter der ersten und zweiten Sammeleinrichtung angeordnete Entleerungseinrichtung mit einem mechanisch angetriebenen Drehtisch, der zum Tragen des Über- bzw. Untermaterials in verschiedene Teile unterteilt ist, wobei jedem Teil eine entsprechende Auslasseinrichtung zugeordnet ist,
• – eine Drückeinrichtung zum Drücken des Materials in die jeweilige angeordnete Auslasseinrichtung für die Teile zum Tragen des Über- und Untermaterials.

DE-OS 29 38 950 describes a Klas siersieb with emptying device at atmospheric operation. The task is the deposition of a moist, sticky, particulate material with a particle size <25 mm and the improved discharge of oversize and undersize from the sizing. The task is solved by:

• A device for feeding the sieve,
• A mechanically driven circular screen surface with a plurality of elongate, radially projecting members,
• A first collecting means for the oversize material adjoining the outer periphery of the sieve surface,
• A second collecting device for the undersize material arranged below the screen surface,
• An emptying means arranged below the first and second collecting means, having a mechanically driven turntable which is subdivided into different parts for carrying the over or under material, each part being associated with a corresponding outlet device,
• - A pressing means for pressing the material in the respective arranged outlet device for the parts for supporting the upper and lower material.

to solution the object set in this invention of a separation of the oversize granules the device listed in DE-OS 29 38 950 is unsuitable. The oversize material, which can arise at the granulation of polymer usually has strongly divergent and irregular shapes and would be in the above-mentioned Device inevitably to malfunction in the way of blockages to lead. Furthermore this device is for the task presented here is very complicated with respect to the apparatus Construction and the energy and operating costs and does not provide simple operating principle. The separation process would also be an upstream and elaborate active surface drying require.

The font SU 1 632 495 presents a device for the separation of granular materials in liquid environment in the treatment of mineral resources, which can also find application in the chemical, metallurgical and agricultural industries. Ore-containing pulp is passed over a sieve plate. Water is introduced under the sieve plate and flows over waves, whereby sinusoidal pulses are transmitted to the material passed over the sieve plate. The material has a high density difference with respect to the water. The pulses cause effective washing out of small parts from the pulp and active movement of the material in the direction of the downward sloping device. The material is in a lower and upper fraction and discharged. The use of this device for the separation of oversizes from the granulate / liquid flow is unsuitable. The pulsation of the guided under the screen plate water creates a dynamic, which is detrimental to the calmed system of deposition in the medium liquid. It is intended to achieve a reduction in the speed and uniformity of its flow by taking advantage of the reduction in the density of the polymer in the quenched liquid and the resulting dynamic pressure in its relative movement to the liquid: the objective is to allow the passage of nominal granules through the perforation to favor the inclined screen and to ensure a small bearing force for the oversizes on the screen plate, which is to avoid the anchoring of bizarre shapes on the holes of the screen plate.

Of the in the claims 1 and 2 indicated invention is based on the problem, a method to develop with a device that provides the necessary separation of the oversizes of the Granules immediately after granulation without an intermediary active surface drying guaranteed and, regarding the UWG process, the contact with the air absolutely avoids; whereby a corresponding quality improvement can be achieved can. It should be the apparatus, energy and operational Effort of surface drying saved and the additional Emission excluded from abrasion by the granules and a simple mode of action be based on.

This Problem is solved by the in the characterizing part of claims 1 and 2 listed Characteristics solved.

The polymer is fed in the UWG process after cutting into granules with the operating fluid directly into a circuit via a top entry into a separator for oversizes. Here, under the liquid, the deposition of the oversizes from the defined granules occurs, whereby the viscosity of the liquid and the specific reduction of the density of the polymer in the liquid due to the buoyancy cause a delay of the kinetics of the polymer in the separator compared to a deposition process in air and the deposition thereby becomes more intense and efficient. The defined granules fall through slots of a slanted in the flow direction sieve plate slots in an underlying collection space. From here it is derived via a nozzle with the liquid flow. The oversizes are guided downwards on the sieve plate and fall into a collecting space after the end of the sieve plate. The collecting space is closed when operating. After shutting off the separator, the liquid can be emptied via a shut-off nozzle. After opening the collection gray mes can then be removed the oversize and flooded after closing the catchment area of the separator again with the liquid and put into operation.

Of the Separator has a top entry, a curved distributor plate and a subsequent one Sieve plate. It is installed so that the screen plate in the flow direction an expiring angle α of 15 ° to 80 ° against has the vertical. The sieve plate is provided with oblong holes, the transverse and offset to the flow direction are arranged and overlap in the flow direction. The dimension a of the slots are 1.5 to 20 times, the dimension b greater than 1.5 to 50 times the largest dimension of the defined granules and the distances of the slots x and y is 0.1 to 50 times the largest dimension of the defined granules. The ratio L: D of the sieve plate is 0.3: 1 to 50: 1. Under the sieve plate and bounded by an end plate is the plenum for the granules formed; at the end of the collection room is the Outlet of the defined granules with the liquid and after the sieve plate a catchment area for the oversizes. Of the Catchment area is provided with a closable opening for removal of the oversizes, and at the lower end of the collecting space allows an arranged neck the previously required emptying of the liquid.

The Advantages of the design according to the invention in the process and apparatus over the previous methods the deposition in air in the improvement of the deposition conditions for the Polymer as well as saving on the required for the deposition in air apparatus, energy and operational costs for the active surface drying of granules after granulation and avoidance of it connected Granulatabriebes. The inventive method is based on a simple principle and ensures an undisturbed operation of the deposition. Allows regarding the UWG process by transporting the polymer directly from under liquid lying cut point a generation of polymer granules absolutely with the exclusion of air and thus the achievement of highest qualities for high demands to the corresponding products.

Embodiment

The inventive method and device will be explained in more detail in a subsequent embodiment, which is shown in the drawing.

It demonstrate:

1 : Scheme with the method according to the invention

2 : the separator according to the invention in side view

3 : the separator according to the invention in view "A"

4 : Section BB and Section CC of the separator according to the invention

• 1. im UWG-Verfahren nach der Granulierung erfindungsgemäß – direkt in den flüssigkeitsgefüllten Abscheider (2 und 3),
• 2. im USG-Verfahren erfindungsgemäß direkt nach dem Granulator – mit der Betriebsflüssigkeit in einen Behälter 18 geleitet und von hier in den flüssigkeitsgefüllten Abscheider, oder – nach Abscheidung von der Betriebsflüssigkeit in einen flüssigkeitsgefüllten Behälter 18 eingeleitet und von hier in den flüssigkeitsgefüllten Abscheider;
• 3. im SG-Verfahren erfindungsgemäß direkt nach dem Granulator – in einen flüssigkeitsgefüllten Behälter 18 eingeleitet und von hier in den flüssigkeitsgefüllten Abscheider.

The polymer can be conveyed in the following ways for the separation of the oversizes ( 1 ):

• 1. in the UWG process after granulation according to the invention - directly into the liquid-filled separator ( 2 and 3 )
• 2. in the USG process according to the invention directly after the granulator - with the operating fluid in a container 18 passed and from here into the liquid-filled separator, or - after separation of the operating fluid in a liquid-filled container 18 introduced and from here into the liquid-filled separator;
• 3. in the SG process according to the invention directly after the granulator - in a liquid-filled container 18 introduced and from here into the liquid-filled separator.

The liquid-filled separator is integrated in a circuit in which the liquid serves as a transport means for the polymer. In a second separator 16 the granules are separated from the liquid and sent for further processing. Not in 1 the known for the circuits described each required heaters or cooling and filtration for the deposition of abrasion, which arises during the granulation.

The invention according to the invention after granulation without water separation and drying direct feeding of the polymer in the liquid-filled separator according to the invention includes in addition to the granules to be defined and the oversize, which arise especially when starting the granulators and occasionally in normal operation. The polymer passes over the top of the inlet pipe 1 in the separator, which may be arranged at an angle α depending on the type of polymer, the granule size, the granular form and the polymer throughput of about 15 ° to 80 ° inclined to the vertical and flooded by the liquid is and flows here first on a distributor plate 2 , At the end of the distributor plate 2 closes immediately a screen plate 3 on, which has a perforation of oblong holes, which are arranged transversely to the flow direction and overlapped. The polymer flows from the distributor plate 2 evenly to the width D of the screen plate 3 distributed on the latter due to the inclination of the separator down. In this case, the granules to be defined on its way L down through the slots in the plenum 4 come to mind. The oversize will continue to run on the screen plate and ultimately fall at the end of the screen plate 3 in the collection room 7 , The collection room 4 is bounded below by the end plate 5 ; at the bottom of the area is the outlet nozzle 6 attached at an angle β of about 160 ° to the vertical, through which the granules are continued with the liquid in a known manner to the Abscheidet 16 in which the separation of the granules from the conveying liquid takes place with the abrasion from the granulation. The granulate is fed to the further processing, the delivery liquid passes through filtration and heating or cooling (according to the respective conditions of supply) in the container 18 or back to the UWG.

By the inventive method of deposition of the oversizes of the granules to be defined under a liquid and in an inclination of the sieve plate 3 In the direction of flow, the following principles of action are exploited:

• - Specific Reducing the gravity of the polymer by guiding in the liquid (finite amount of lift),
• - effect the reduction in the rate of flow of the polymer due to Increase the dynamic toughness of the surrounding medium (change from air to liquid, for example water, in the relationship from about 17: 1),
• - Reduction of the vector of the contact pressure of the polymer on the screen plate 3 , in particular for the oversize, by the inclination angle α.

These three factors cause the kinetics of polymer flow to be lowered, allowing for smooth motion of the polymer on the mesh plate 3 which favor the deposition in terms of an improved distribution of polymer on the screen surface and a reduction in the tendency for hooking and possibly the passage of bizarrely shaped oversizes through the holes of the screen plate 3 compared with the known deposition in air (here approximately horizontal position of the screen plate).

The operation of the separator can because of the required short-term interruption to remove the oversizes from the collection space 7 for operating cases with a large amount of oversizes, also be carried out with two alternately connected devices and proceeds in the following manner:

To leave:

• - Polymer supply from container 18 or UWG locked.
• - By pump 19 Liquid circuit via: container 18 or UWG - inventive separator - separator 16 - Container 18 or turn on UWG.
• - vents 20a and 20b carry out.

Business:

• - Polymer supply from container 18 or UWG open.
• - Deposition over the sieve plate 3 takes place, oversizes fall into catchment area 7 , Granules flow through the slots in the plenum 4 and from here with the liquid through the outlet nozzle 6 to the separator 16 and fed to the further processing.

Removing the oversizes:

• - Switch on the second separator.
• - Shut off the fittings before the nozzle 1 and after the neck 6 ,
• - Opening the valve after emptying nozzle 10 and draining the liquid from the separator via the conduit 17 in the container 18 or UWG (possibly installed collection container), ventilation via piping 21 from the inertized gas space of the further processing stage (for the production process of polyamide 6 eg extractor for extraction of the granules).
• - opening the lid 12 and removal of the strainer basket 9 ,
• - emptying the strainer basket 9 and insertion into the separator, closing the lid 12 ,
• - Separators flood and over 20a bleed, operational readiness exists.

The removal of the oversizes can also be done in another solution, such as the oversizes in a prolonged space 7 fall down and collected here in an enlarged volume and removed after a long period of time.

• – Art des Polymers (Dichte),
• – Granulatgröße,
• – Granulatform,
• – Polymerdurchsatz.

The separator consists of the inlet nozzle 1 for the polymer flush with the distributor plate 2 is arranged ( 2 and 4 , Section CC), the screen plate 3 , which directly adjoin the distributor plate 2 connects, under the screen plate 3 and from the end plate 5 formed collecting space 4 for the granules, the outlet nozzle 6 for the granules, divided into a conical section 6a to the transition from the cross section of the separator in the subsequent pipe cross-section 6b ( 2 and 4 , Section BB), a funnel 8th for introducing the oversize into the catchment area 7 holding a sieve basket 9 contains, handles 14 on the strainer basket 9 for removal from the separator, drainage nozzle 10 to drain the liquid from the separator, opening 11 and lid 12 , connected via a hinge, and storage 15 for stepless adjustment of the inclination angle α of the separator in the required values as a function of the following parameters:

• - type of polymer (density),
• - granule size,
• - Granule form,
• - Polymer throughput.

The ratio L: D of the sieve plate 3 , the dimensions a and b for the selected slots and their arrangement x and y on the screen plate 3 are also dependent on the parameters of the polymer granules and the throughput. The staggered arrangement of the holes has over, for example, a perforation in the form of transversely to the flow direction arranged rods (eg slot grating) the advantage that the webs (y), which are each arranged in front of the subsequent slots, a bridge for the oversizes when flowing over the Form sieve plate and thus prevent falling through into the collecting space. The point angle of the conical part 6a of the granule nozzle 6 ( 4 , Section BB) should have a value of <60 °, allowing a free flow of granules from the plenum 4 is guaranteed. It is just like the angle β between the axis of the outlet nozzle 6 and the vertical depending on the parameters of the defined polymer granules.

Claims (5)

A process for the separation of oversizes and malformations arising in the granulation of polymer by means of underwater granulation, underwater strand granulation or strand granulation, characterized in that the granules directly from an underwater granulation with the liquid via a circuit in a Liquid-filled separators for oversizes over its upper inlet connection ( 1 ) is introduced or is transferred with the operating fluid of an underwater strand granulation in a container or without operating fluid in the container filled with liquid and then in the separator, in the separator, the oversize by means of a directionally inclined sieve plate ( 3 ) are deposited, the granules through the perforation of the screen plate ( 3 ) into a collection room ( 4 ) falls and from there via an outlet nozzle ( 6 ) is discharged with a liquid flow, the oversize at the end of the sieve plate in a collecting space ( 7 ), the nozzles ( 1 ) and ( 6 ), the liquid from the collecting space ( 7 ) via a drainage nozzle ( 10 ) is removed, and the oversizes are removed. Apparatus for carrying out the method according to claim 1 with a separator arranged in a liquid circuit, characterized in that a) the separator at the top has an inlet connection ( 1 b) to which a convex distribution plate ( 2 ) and c) a screen plate ( 3 ), which is arranged at an angle α of 15-80 ° to the vertical, whose dimension in the direction of flow of the granules and perpendicular thereto comprises a ratio L: D of 0.3 to 50: 1, having elongated holes transverse to the flow direction and are arranged offset in the flow direction and overlap in the flow direction, d) that under the screen plate ( 3 ) a collection room ( 4 ) is arranged for the granules, with an outlet nozzle ( 6 ), which has an angle β of 100-220 ° to the vertical, e) and that after the screen plate ( 3 ) a catchment room ( 7 ) for the oversizes, with a closable opening ( 11 ) for the removal of the oversizes and a drainage nozzle ( 10 ) for the liquid. Apparatus according to claim 2, characterized in that the distributor plate 2 for the polymer has a radius r of 0.5 · D to 5 · D. Apparatus according to claim 2, characterized in that the collecting space 7 an inner screen basket 9 contains. Device according to claim 2, characterized in that that the separator is installed on a storage, which is a stepless adjustment of the angle α allows.