WO2007012404A1

WO2007012404A1 - Stirring device for melt polycondensation having a double rotor and product-lubricated reactor-internal rotor bearing

Info

Publication number: WO2007012404A1
Application number: PCT/EP2006/006837
Authority: WO
Inventors: Fritz Wilhelm; Ludwig Hölting
Original assignee: Lurgi Zimmer Gmbh
Priority date: 2005-07-23
Filing date: 2006-07-13
Publication date: 2007-02-01
Also published as: DE102005034456B3

Abstract

The invention relates to a device for melt polycondensation of condensation polymers with removal of gaseous cracking products in a horizontal cylindrical reactor having a stirred chamber and two rotors coaxially arranged in the stirred chamber. A disadvantage of the known double cage reactors proves to be that the permissible edge passability in the case of relatively large cages is disadvantageously affected by the bending of the cages with externally arranged bearings. This disadvantage is overcome by the device according to the invention by the outer rotor (1) having a rotationally symmetrical running surface (5) on its side opposite the driveshaft (3), which running surface (5) together with a complementary rotationally symmetrical counter element (8) on the housing wall of the reactor or with the driveshaft (4) of the inner rotor (2) forms a plane bearing. Advantageously, the inner rotor (2) on its side opposite to the driveshaft (4) also has a rotationally symmetrical running surface (6) which, together with a shaft extension (7) of the driveshaft (3) of the outer rotor (1), forms a further plane bearing.

Description

STIRRING PREPARATION FOR MELTING POLYCO-CONDENSATION WITH DOUBLE ROTOR AND PRODUCT LUBRICATED REACTOR ROTOR STORAGE

The invention relates to a device for the melt polycondensation of condensation polymers with removal of gaseous cleavage products in a horizontal cylindrical reactor with a stirring chamber, comprising a product inlet, a product outlet and at least one gas line in the upper region of the stirring chamber, and with an outer and an inner rotor coaxial in arranged the stirring chamber and are each connected on one side with a central drive shaft.

In many processes for the production of plastics, horizontal or vertical reactors are used. Horizontal reactors usually have at least one shaftless, self-supporting rotor with outer shaft journals or a continuous shaft with extensions. Attachments can be designed as disks with and without spokes, with and without holes, as lattice disks, etc. These reactors are placed under vacuum for proper process control and completely heated with an organic heat exchanger. The rotors are usually operated at low speeds. The bearings of these rotors are located outside of the reaction vessel behind a seal and are part of the removable or firmly welded lid. The rotor bearing for a shaftless, self-supporting rotor includes bilateral shaft passages from the reaction vessel and does not allow stripping of products.

Reactor with reactor cage are generally considered as a category of polymer reactors. In polyester reactors with a reactor cage, a rotor rotates within the reactor housing, which along longitudinal supports arranged perpendicular to either sheets with many openings, other installations or wire mesh has, and is also called a cage because of lack of accessibility in the radial direction. The cage reactor represents an alternative to a stirring disk reactor. In principle, this serves the same purpose. follows, namely the creation of a large surface of the products contained therein to remove low molecular weight reaction products as quickly as possible. Depending on the model, differences in the various cages may be the residence time behavior, self-cleaning capability, dead space avoidance, adaptation to increasing product viscosity, steam load, etc. Since the required throughputs of such reactors have grown steadily in recent years, the dimensions will also increase the cages increasingly larger, for example, with a length of up to 12 m and a diameter up to 4 m. With the length of such a cage also its deflection increases, with the result that the shaft journals mounted at the ends no longer lie horizontally and in alignment with each other, but experience an inclination with increasing bending moment.

DE 40 13 912 C2 discloses a double cage reactor for melt polycondensation. Characterized in that coaxially to the first rotor mounted on hollow shafts on the front sides of the housing via inner shafts mounted second rotor is provided which is drivable with relative movement to the first rotor and stripping elements for removing the adhering to the first rotor medium, wherein the one Rotor rotates in the other, a good mixing with uniform flow and narrow Verweilsspektrum the flowable medium is ensured, while at the same time all surfaces of at least one rotor and the reactor housing are scraped and cleaned.

JP 200-392874 A, Abstract refers only to a device for the melt polycondensation of condensation polymers with two provided in a stirring chamber rotors, which are aligned coaxially with each other.

WO 00/73033 A2 shows only one stirring housing or two reactor housings arranged next to one another. Therefore, this document does not show any features consistent with the subject of the application. EP 0 858 829 A2 shows various embodiments of cooperating stirring elements which are connected next to one another or behind one another. Again, this document has no features consistent with the subject of the application.

The APOLLIT Abstract 1999: 1805 shows only in Fig. 1 an outer and inner cylinder with a bearing book support. Rotors are not shown in this document, at least it is not disclosed how the rotors or cylinders should be additionally supported.

The US 5,589,239 relates to a device for the treatment of polymeric products, which is equipped with a drive device which is mounted outside of the housing.

DE 32 08 973 A1 relates to a device for processing viscous substances that are viscous during processing. For this purpose, juxtaposed disk rotors are provided whose bearings are provided outside the reactor housing.

A similar bearing arrangement is also the FR 925 111 B, are shown in the bearings outside the rotor housing.

The SU 1606170 A1, Abstract shows a schematic arrangement of a stirring device, wherein the bearings must also be placed outside of the stirring.

A further schematic representation of a reactor housing with two coaxially arranged cylinders can be taken from JP 06-287005 A, abstract. Again, this document does not show any bearings that are lapped by a product. The same applies to CS 228 399 B, Abstract, which discloses a device intended for processing sugar beet. The US 3,989,610 A relates to a gas centrifuge and is therefore not to be compared with this subject of the application.

DE 2932542 A1 relates to a centrifugal casting apparatus for dental technology and therefore does not prevent the subject-matter of the patent from being patented, since this relates to a different subject area.

Furthermore, a device of the type described is known from DE 0 445 282 A1, which relates to the treatment of highly viscous media with a horizontally oriented reactor housing having an inlet and an outlet, wherein in the reactor, an outer and an inner rotor is arranged , which are mounted coaxially in the stirring chamber and are each connected on one side with a central drive shaft. The outer rotor also has, on its side opposite the drive shaft side, a rotationally symmetrical bearing having a running surface. Both bearings are, as is apparent in particular from FIG. 1 of the document D1, arranged outside the stirring chamber, so that they have to be lubricated after certain time intervals, which is associated with a large maintenance.

The disadvantage of the known double-cage reactor is that the permissible edge tolerance and thus the operating behavior of larger cages are detrimentally influenced by the deflection of the cages with externally arranged bearings. The mutual scraping of housing and rotor surfaces can be achieved only with correspondingly reinforced cage elements and brackets, which then have functional disadvantages.

The terminal connections of the outer cage to hollow shafts and the inner rotor to a drive shaft mounted within the hollow shafts and a stub shaft also require two double bearings and four sealing units at each reactor end. This results in an increased risk of leaks and a considerable effort for the tightness control. In the scale-up of such a reactor, moreover, an earlier achievement of critical seal dimensions in comparison to single-shaft reactors is to be expected.

Bulky bearing housings on both sides, the complicated double-shaft constellation on the face side and the double-cage structure make assembly, dismantling, maintenance and commissioning of the reactor for inspection purposes sustainable.

The invention has the object of providing a device of the type mentioned in such a way and to arrange that the disadvantages described there are overcome and in addition to an advantageous, space-saving arrangement of the rotors, the time of maintenance of the system is substantially reduced.

The object is achieved in that the bearing surface bearing having a complementary, rotationally symmetrical counter-element on a housing wall of the reactor or with the drive shaft of the inner rotor forms a product-lubricated, internal reactor bearing. With the inner bearing of the rotors pressed in the level of the cage holder, the bending moment at the respective cage decreases decisively, so that the dimensional stability of the rotors is substantially improved. The advantageous arrangement of the bearings provided in the reactor is obtained in a simple manner by lubricating the bearings with the aid of the product, which flows around the bearings. As a result, maintenance times can be significantly reduced.

The object is achieved by a device according to claim 1.

The device according to the invention for the melt polycondensation of condensation polymers with removal of gaseous cleavage products in a horizontal cylindrical reactor with a stirring chamber, comprising a product inlet, a product outlet and at least one gas outlet in the upper region of the stirring chamber, and with an outer and an inner rotor, the arranged coaxially in the agitating chamber and are each connected on one side with a central drive shaft, characterized in that the outer rotor on its opposite side of the drive shaft has a rotationally symmetric running surface, with a complementary rotation onsymmetrischen counterelement on the housing wall of the reactor or forms with the drive shaft of the inner rotor a product-lubricated, internal reactor bearing, in particular a plain bearing forms.

The number of shaft passages per rotor is hereby limited to one each. Accordingly, the number of bearings and seals is halved compared to prior art reactor systems. The risk of leaks is alleviated, in particular, by using conventional simple drive shafts on proven bearing and sealing systems.

Advantageous embodiments of the device according to the invention are the subject of the dependent claims.

With the inner bearing of the rotors in the plane of the cage suspensions, the bending moment at the respective cage end largely disappears, consequently the dimensional stability of the cage ends is achieved with smaller material thicknesses, and the marginality of the rotors can be improved. The inner bearings are all or partly due to a suitable geometry of the cage brackets, the bearing assembly and the product level in operation preferably lapped by product and self-lubricating. Forced delivery of the product by means of pumps to the bearing is generally not required.

In a preferred embodiment, the inner rotor on its side opposite the drive shaft side has a rotationally symmetrical running surface, which is provided with a shaft extension of the drive shaft of the outer rotor or a shaft journal of the outer rotor, for example, following a only simply stirred entrance zone, another camp, especially a plain bearing forms.

In an additional advantageous embodiment, at least one of the bearings is designed, for example, by a corresponding arrangement of the product inlet as a product forced through by product, which is particularly important when the product viscosity drops.

Preferably, one or more of the rotationally symmetrical bearing contact surfaces are wholly or partly made of a bearing metal. This makes it possible to avoid seizure of the plain bearings during start-up or transition phases. The production of the bearing contact surfaces may also relate only to parts of a rotationally symmetrical bearing contact surface, for example, in the case that the complementary rotationally symmetrical counter-element is formed as part of the cylindrical outer wall. Here, the use of a bearing metal for the complementary rotationally symmetric counter element is required only in the lower support area of a rotor.

Instead of a plain bearing, a rolling bearing, for example a ball bearing, a tapered roller bearing, a spherical roller bearing or another rolling bearing type made of suitable materials, for example ceramic, can be used in particular.

By special rotor design and the provision of scrapers is generally a mutual stripping of product surfaces possible.

The invention is explained below by way of example with reference to the accompanying figures.

It show here

1 shows a reactor according to the invention with a stirring chamber, comprising a product inlet 15, a product outlet 16 and a not shown gas discharge in the upper region of the stirring chamber, and with an outer rotor 1 and an inner rotor 2, which are arranged coaxially in the stirring chamber and each connected on one side with a drive shaft 3, 4, wherein the outer rotor 1 on its the drive shaft 3 opposite

Side has a rotationally symmetric tread 5, which forms a sliding bearing with a complementary rotationally symmetrical counter element 8 on the housing wall of the reactor, and wherein the inner rotor 2 on its the drive shaft 4 opposite side has a rotationally symmetric running surface 6, which with a shaft extension 7 at the drive shaft 3 of the outer rotor 1 forms a plain bearing.

Fig. 2 shows a reactor according to the invention, which is constructed in principle as the reactor in Figure 1, wherein the rotationally symmetric tread 5 of the outer rotor 1 forms a sliding bearing with a part of the outer reactor housing as a complementary rotationally symmetrical counter element 8.

3 shows a reactor according to the invention in which the inlet area of the outer rotor 1 in the left half of the reactor is simply stirred and the area behind it is constructed in the right half of the reactor with an inner rotor 2 in principle as in the reactor in FIG. The outer rotor 1 has on its side opposite the drive shaft 3 side a rotationally symmetrical running surface 5, which forms a sliding bearing with the drive shaft 4 of the inner rotor 2. The inner rotor 2 has, on its side opposite the drive shaft 4, a rotationally symmetrical running surface 6, which forms a product-lubricated sliding bearing with a shaft journal 7 as a counter element in an intermediate wall between the input area and the area behind. In this way, a better accessibility of the reactor is ensured. Fig. 4 shows a reactor according to the invention according to the principle of the reactor in Figure 1, wherein the product inlet 15 is provided so that the sliding bearing formed by the rotationally symmetric tread 5 and the rotationally symmetrical counter-element 8 is inevitably flushed by incoming product.

Fig. 5 shows a reactor according to the invention according to the principle of the reactor in Figure 1, in which instead of the conventional storage and sealing of the drive shaft 4 of the inner rotor 2, a sliding bearing between the drive shaft 4, the bearing housing 9 and an outer seal occurs. The plain bearing thus formed is forcibly flushed by precondensate from the product inlet 15. In the interest of low bending moments on the rotor 2, the plain bearing is moved close to the rotor start. Also, the drive shaft 3 of the outer rotor 1 could be stored in this way.

Fig. 6a to

6c each show a detail from FIGS. 1, 2 and 3 of three different possibilities of the bearing having a running surface, the outer rotor 1 having on its side opposite the drive shaft 3 a rotationally symmetrical bearing 8.1 having a running surface 5 and that the bearing surface bearing bearing 8.1 with a complementary, rotationally symmetrical counter element 8 on a housing wall 17 of the reactor or with the drive shaft 4 of the inner rotor 2 forms a product-lubricated, internal reactor bearing. LIST OF REFERENCE NUMBERS

1 outer rotor

2 inner rotor

3 Drive shaft of the outer rotor

4 drive shaft of the inner rotor 5, 6 rotationally symmetric running surfaces 7 shaft extension, shaft journal

8 complementary rotationally symmetric counter element

9 bearing housing

15 Product introduction 16 Product discontinuation

Claims

claims:

A device for melt polycondensation of condensation polymers with removal of gaseous cleavage products in a horizontal cylindrical reactor with a stirring chamber, comprising a product inlet (15), a product outlet (16) and at least one gas outlet in the upper region of the stirring chamber, and with an outer and an inner rotor (1, 2), which are arranged coaxially in the agitating chamber and in each case on one side with a central drive shaft (3, 4) are connected, wherein the outer rotor (1) on its the drive shaft (3) opposite side of a rotationally symmetrical, a tread (5) bearing (8.1), characterized in that the bearing surface (5) bearing (8.1) with a complementary, rotationally symmetrical counter element (8) on a housing wall (17) of the reactor or with the drive shaft (4) of the inner rotor (2) forms a product-lubricated, internal reactor bearing.

2. Device according to claim 1, characterized in that the inner rotor (2) on its the drive shaft (4) opposite side has a rotationally symmetric running surface (6) with a shaft extension (7) on the drive shaft (3) of the outer rotor (1) forms a bearing, in particular a sliding bearing.

3. Apparatus according to claim 1 or 2, characterized in that at least one reactor-internal bearing is designed so that it is umspülbar of product.

4. Device according to one of claims 1 to 3, characterized marked, that at least one reactor internal bearing is forcibly flushed by product.

5. Device according to one of the preceding claims, characterized in that one or more of the rotationally symmetrical bearing contact surfaces are wholly or partly made of a bearing metal.

6. Device according to one of the preceding claims, characterized in that the rotors (1, 2) have stripping elements.