DD150932A1 - DEVICE FOR CRYSTALLIZING ARMORPHIC POLYESTER GRANULES - Google Patents

Abstract

Apparatus for the crystallization of amorphous polyester granules, which is used in the production of man-made fibers, aims at a significant reduction of the specific energy expenditure in the drying process in connection with the exhaust air utilization of a shaft dryer and the task, with more than 50 kg / h in less than 10 min to supply free-flowing polyester granules final drying. The object has been achieved according to the invention by means of a partially heated crystallization tube with a slowly rotating stirrer shaft and stirrer arms to which stirrer blades are attached in parallel to the wall in such a way that a continuous sequence of heat absorption by granules close to the wall and heat emission to the loosened center takes place.

Description

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Title of the invention

Device for the crystallization of amorphous polyester granules

Field of application of the invention

The invention is preferably applied in the chemical fiber industry for drying polymer granules which tend to stick in the heating phase.

Characteristic of the known technical solutions

PUr the production of chemical fibers certain high polymers nuts before the S _c hmelzextrusion to prevent d.es hydrolytic degradation undergo a drying process · While. In particular, polyester granules from 360 ° C. by adhering the surfaces show a strong tendency to agglomerate formation, which only returns after a partial crystallization of these surfaces. In an effort to achieve this state of crystallization as quickly as possible and

To provide a necessary longer period of time required final drying, two-stage devices with a crystallizer (for partial crystallization) and subsequent final dryer, usually in the design of a shaft dryer, have proven

It was proposed in DE 23 17 651 to form the first heat treatment unit as a fixed, in v / public horizontal, cylindrical tube with heated wall surface in which coaxially a fast rotating shaft is arranged with several reaching to the pipe wall paddles, the drifting amorphous polyester granules in a thin layer along the entire heated wall for partial crystallization * In 5 minutes, for example, a partial degree of crystallization should be achieved here, which ensures the subsequent final drying in a downstream shaft dryer without any agglomeration tendency.

The advantageous Hutzung the heat transfer from the heated wall to the granules here are the resulting from the arrangement disadvantages of excessive energy expenditure to spin the granules and the d.araus inevitably resulting dust-like abrasion counteracts «The proposal therefore also indicates that appropriate A dedusting line should also be conducted directly from the crystallization space to the dedusting cyclone. US Pat. No. 3,547,890 proposes a drying apparatus for polyester granules, the drywell of which is fitted with a granule feed and a crystallization zone or which is inserted into the top of the shaft. a helical or with horizontal blades occupied agitator shaft moves so that the granular particles in the stirrer area are slightly loosened during the downward movement, to counteract agglomeration and the hot gas to allow a uniform rinsing of the granules. Purely the pail, that agglomerates are formed in the crystallization zone, is provided at its output a cammed crusher ·

In the case of the input moisture of the granules of 0.5% by weight and BO kg / h throughput, 0.8 hours for crystallization and 8 hours for the final

μ 3 -.

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ρ- 3 -

drying to 0.01% by weight (determined by the Fischer method).

The proposed apparatus has over the device described in DE 23 17 by the insufficient use of the cheaper heat transition from the wall of the crystallization vessel to the granules much longer residence times to partial crystallization on «The specific energy consumption, per kg of granules is higher, especially also in addition Crushing plant still has to be driven, which is also known to increase the dust content »

Object of the invention

The object of the invention is a device which, in conjunction with a known shaft dryer, partially crystallizes polyester granules in a crystallization zone preceding it at throughputs greater than 50 kg / h with the most favorable use of energy (energy consumption 0.103 kWh / kg) and less than 0.005 % moisture content endtrocknet. ·

Statement of the Essence of the Invention

The invention has for its object to arrange appropriate device parts on and in the crystallization so that amorphous polyester granules are partially crystallized at usual throughputs using favorable heat transfer in less than 10 minutes residence time and agglomerate is fed directly to the downstream shaft dryer.

According to the invention, the task dad.urch solved that on a shaft dryer a vertical, to 1/2 to 2/3 of its length surrounded by a heating jacket crystallization tube

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is arranged with a central stirrer shaft, which is formed at the level of the granule inlet with a displacement similar thickening and has agitator arms carrying end-wall aligned blades, which in the direction of movement a defined positive angle and. have a distance from the inner tube wall, which is two to five times the smallest Granulatabmaßes, wherein advantageously the crystallization tube is provided inside in the region of the heated surface with 3 to 6 longitudinal ribs «The vertical height H of the crystallization tube in relation to the inner diameter D. selected with 4 to 7 and set in a particular case so that the gas flowing from the shaft dryer through the crystallization tube gas reaches a speed equal to or less than the Wirbelpunktgeschwind.igkeit. The stirrer arms are. arranged in one or two helically extending around the agitator shaft planes, flat-shaped and attached to the agitator shaft with one of the imaginary helical conformen inclined, so that during the rotation of the agitator shaft, the granular dry matter is partially raised when passing through the individual arm. "The blades at the ends of the stirrer arms are fixed parallel to the wall at a distance h from the stirrer wall. In this case, h refers to the front, outer blade edge, while, seen in the direction of rotation, the rear blade edge due to a pitch angle of the blade of 15 ° to 30 ° must have a greater distance than h. The distance h is chosen as a function of the largest average size of the granule and should be 2 to 5 times, preferably 3 times, the granule diameter. The blade length b was 0.2 to 0.3 », preferably 0.26 of the slope s of the above mentioned imaginary helix around the stirrer shaft found. The number of stirrer arms and the speed of the stirrer shaft are determined by the dimensions of the granule

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and. its heat absorption rate at the position in the layer on the heat-releasing wall · Once the heat saturation of the granule is reached, it must be separated from the wall by a blade called dex and conveyed towards the center of the crystalliser «Different spheres (spheres, rectangular platelets, rolls) cause corresponding detachment rhythms. For the course of the partial crystallization, it has been found necessary to make the feed of the amorphous granules very uniform and. Preventing the Teilkristallisstionsvorganges often by irregular and with varying intensity occurring abrasion or dust «is generally carried out the Granulatzulauf an oblique granules inlet nozzle at the top of the crystallization tube using gravity and. on the opposite side of the inlet of the exhaust pipe, I arranged a little higher, further arranged in the upper part of the Rilhrerwelle a displacer which narrows the Strömtingsquerschnitt above the granulate, so the dust load at the crystallizer inlet drops to a normal hatred. A possibility for exchanging differently shaped displacers for the corresponding granule form and diameter should be advantageously provided. "

In order to maintain a constant air velocity, the inner wall of the crystallizer can be conically formed ·

In each pass, the crystallization tube is surrounded by a heating mantle, the height of which is only 0.6 to 0.8, preferably 0.7, of the crystallization tube height H, measured from the center of the feed opening to the point of the crystallizer.

In continuous operation, amorphous high polymer, which tends to stick when heated, passes through the granulate inlet into the crystallization tube

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Dust is in the upper Kristallrohrrohrbereioh having, by the displacer constricted channels and. causes higher flow velocities, blown out with the exhaust air. The registered granules, is heated, on the one hand by the counter-flowing hot exhaust air, on the other hand by the intense heat exchange at the v / poor crystallization tube wall and. While the granules move downward by gravity, the total bed is slightly loosened by the hot countercurrent and is also temporarily raised by the undercut set stirrer arms, so that there is no agglomeration. On the wall of the crystallization tube and. in their immediate vicinity fitting granules is heated rapidly at Wa ndtemperaturen from 443 K to 493 K under favorable heat transfer, stripped after a few seconds from the wall and promoted towards the center with simultaneous action of the gravity component, while, a new assignment of the wall areas for renewed Heating up takes place. Accordingly, individual granules move in a zigzag shape in the granulated bed which has been loosened overall. in addition steep spiral shape from top to bottom, go through the crystallization tube in about 4 to 6 minutes and. leave it with a degree of partial crystallization of 40 % to 48%, which ensures final drying in the downstream shaft dryer without any agglomeration * The hot exhaust air removed from the shaft dryer for this partial crystallization is largely utilized in the device for preheating the granules Temperature below 310 K, from which derives the main advantage of this invention. Solution, which lies in the favorable energy yield. The direct heat transfer from the partially heated Kristallisatwand.ung in conjunction with the continuous granule separation on the one hand and, the low driving forces due to the agitator shaft, the movement of the stirring arms and.

On the other hand, shovels in a loosened granulate fill allow the hot gas stream to be used completely out of the shaft dryer so that a quantity of heat which is hardly technically usable is given off to the environment at the exhaust air outlet «

embodiment

The invention will be explained in more detail below using an exemplary embodiment.

It shows

Fig. 1 shows a longitudinal section through the crystallization tube placed on the shaft dryer with the stirrer

Pig «, 2 - a cross section through the crystallization tube in the section plane A-A.

On a shaft dryer 1, a crystallization tube 2 with a ratio of diameter D to height H equal to 5 was placed. A heating jacket 3 surrounds the crystallization tube 2 up to 0.6 H _e

At its center, a stirrer shaft 6 driven by the geared motor 5 from the cover 4 of the crystallization tube 2 was arranged with four stirrer arms 7 made of flat steel set at an angle OC = 35 ° in the direction of rotation, forming the faces of the stirrer arms 7 Sections of an imaginary, helically placed around the agitator shaft 6 spiral with the slope s = 0.8 D * at right angles to the stirrer arms 7 blades 8 at an angle β = 15 ° were set so that the leading edge, accordingly, the granule size 4 x 4 x 1.5 mm, a distance, h of 10 Elin of d.er inner wall of the crystallization tube 2 possessed «. The length b of the blade 8 was 0.25 s,

1 19!

-B-

At the head of the device, the granules tzulauf support η 9 was attached, diametrically assigned to him the exhaust port, 10, which led to dedusting cyclone (not shown) · releasably connected to the agitator shaft was a potffb ' oerdrängerkörper 11 whose bottom edge was located at the level of the center of the granule inlet nozzle 9, whose diameter d. The heated crystallizer wall was equipped with three longitudinal ribs 12, whose thickness was 3 mm, uniformly distributed on the circumference and running parallel to the circumference. In continuous operation at 50 kg / h throughput after feeding amorphous polyester granules of the stated dimensions with an initial moisture content of 0.12% Total agglomerate freedom and a partial crystallinity of the granulate at the shaft dryer inlet of 43 % were determined. The dust load was -0.2 % at the dryer outlet with an input value of 0.6 % in front of the dryer inlet. With a supply air temperature to the shaft dryer of 473 K, a granulate moisture content at the shaft dryer output of 0.003 % could be achieved · The exhaust air temperature was set to 318 K.

Claims (1)

221 191 Erfind.ungsanspru.cn 1. A device for crystallization of amorphous polyester granules, which is surrounded by a heating mantle a shaft dryer is placed directly and the hot exhaust gas takes, dad.urch characterized, d.aß in a preferably cylindrical crystallization tube (2) with a D / H ratio of 4 to 7, in the head of a granule filler η (9) and. diametrically opposite, an exhaust air outlet (10) einmünd.et, centric at its upper end with a cup-shaped displacement body (11) provided, driven agitator shaft (6) with circumferentially in an imaginary helix evenly distributed flat, negative direction in the direction of rotation stirrer arms (7 ), at the ends of which blades (8) are arranged .parallel with a positive angle of attack. such that the leading edge (8a) of the blade (8) is spaced from the wall of the crystallization tube by two to five granular grain thicknesses. 2 "device according to item 1, characterized in that the negative Einatellwinkel (#) of the stirrer arms (7), measured at the arm root, - 15 to - 45, preferably 30 °, the positive setting angle (/ 3) of the blades (8) 8 ° to 45 °, preferably 15 °. Device according to point 1, characterized in that the cross-section of the crystallization tube (2) is reduced by 40 % to 60%, preferably 50 %, in the region of the head part above the granule inlet through the pot-like displacement body (11), 4. Apparatus according to item 1, characterized in that on the heated inner wall of the Kpistallisators (2), the agitator shaft (6) axially parallel extending, three to six am - 10 - 221 191 Circumference evenly distributed longitudinal ribs (12) are arranged, whose surfaces have a distance of one to two granules thickness of the front blade edge (8a).