WO2001005914A2

WO2001005914A2 - Separating facility for separating a polyglycol and ethylene mixture

Info

Publication number: WO2001005914A2
Application number: PCT/EP2000/006756
Authority: WO
Inventors: Heribert Schmid; Andria Weber
Original assignee: Heribert Schmid; Andria Weber
Priority date: 1999-07-16
Filing date: 2000-07-14
Publication date: 2001-01-25
Also published as: AU6693900A; DE29912501U1; WO2001005914A3

Abstract

The invention relates to a separating facility for separating a leakage current having a polyglycol and ethylene mixture. Said leakage current can be guided from a lubricating system via a leakage collecting line (30). With the aid of said system, a compressor facility (1) for compressing ethylene is lubricated using polyglycol, whereby the separating facility can be adaptively coupled to the leakage line (30) and the purified polyglycol drawn from the leakage current is fed back to the lubricating system via the separating facility.

Description

SEPARATOR FOR SEPARATING A MIXTURE OF POLYGLYCOL AND ETHYLENE

description

The present invention relates to a plant for separating a mixture of polyglycol and ethylene according to claim 1.

The above-mentioned mixture is contained in a leakage stream which is led via leakage lines from a lubrication system, with the aid of which a compressor system for the compression of ethylene is lubricated using polyglycol as a lubricant.

The ethylene compressed in the compressor system is fed to a polymerization zone in a polymerization apparatus to produce polyethylene. In order for the ethylene to polymerize in the polymerization zone, the ethylene must be compressed in the compressor system to a polymerization pressure of up to 3000 bar.

At such high polymerization pressures, multi-stage compressors are normally used so that the ethylene is pre-compressed and then compressed to the polymerization pressure in a two-stage compressor. The ethylene for the polymerization reaction is then introduced into the polymerization zone (reactor), which is used to produce polyethylene at polymerization temperatures of up to 350 ° C. and in the presence of catalysts.

Piston compressors in particular have proven to be suitable for generating such high pressures. Of course, it is also necessary to find a suitable lubricant for the lubrication of the moving parts in piston compressors that maintains its lubricating effectiveness under high pressures and in a wide temperature range. The use of polyglycol and other lubricants has proven useful for such extreme conditions. The leakage losses of the lubricant, which are inevitable in piston compressors, are considerable, especially with high-pressure compression of ethylene. Such leakage occurs, for example, on the piston seal, such as a labyrinth seal, of the compressor. In the case of polyglycol as a lubricant, the resulting leakage current contains polyglycol with a large unknown proportion of ethylene bound in the polyglycol.

A return of the leakage current in the lubrication system of the

The compressor system is therefore out of the question, since this large unknown proportion of ethylene in the leakage stream would influence the reaction equilibrium in the polymerization zone (reactor) following the compressor system. Rather, such a leakage current can no longer be used for the lubrication of a compressor system in the context of a polyethylene manufacturing process.

Disadvantageously, new lubricant has to be constantly added to the lubrication system of the compressor system, which makes the operation of the lubrication system and thus the entire polyethylene production process expensive (often more than 100,000 l / year).

One way to control the cost of

Lowering the polyethylene manufacturing process is therefore to make the operation of the lubrication system of the compressor system more economical.

For example, the operation of the lubrication system can be made more cost effective by using a lubricant that is cheaper than polyglycol. However, such cheap lubricants often give the lubrication system only a limited lubricating effect under extreme pressure and temperature conditions and therefore contribute to premature wear of the moving parts in compressors Another alternative to make the operation of the lubrication system less expensive is to improve the sealing system of the compressors so that leakage currents emerging from the sealing system are reduced, which also reduces the amount of lubricant newly supplied to the lubrication system. However, there are disadvantages in this that conversion to more effective sealing systems in existing compressor systems can only be carried out with considerable expenditure of time and money.

The object of the present invention is to provide the operation of an existing lubrication system that works with polyglycol as a lubricant

To make the compressor system for compressing ethylene more cost-effective.

The object of the present invention is achieved by the features of claim 1. According to the invention, a separation system for separating an ethylene portion of polyglycol from a mixture of polyglycol and ethylene is structured in such a way that the separation system can be adaptively coupled to a leakage collection line of the lubrication system. After the ethylene component has been extracted from the polyglycol in the separation system, the polyglycol cleaned via the separation system can then be returned to the lubrication system. It is thus possible according to the invention to feed the polyglycol used as the lubricant back into the lubrication system in a closed circuit after it has leaked from the compressor system, as a result of which the

Operation of the lubrication system in a simple manner, ie without retrofitting measures in the lubrication system and in the sealing system of the compressor system, can be made more cost-effective. This is because the separation system according to the invention can advantageously be easily coupled to existing lubrication systems of compressor systems. The leakage manifold of the lubrication system is preferably coupled directly to a separation container of the separation system, in which the ethylene can be evaporated from the mixture of polyglycol and ethylene.

Due to the leakage taking place under high pressure, the leakage current in the leakage manifold has a high internal energy. This energy can advantageously be released by relieving the leakage current flowing into the separating container, as a result of which a considerable proportion of bound ethylene evaporates from the leakage current.

In order to force evaporation of the bound ethylene from the leakage stream, a baffle plate can be provided according to a further development of the invention compared to the junction of the leakage collection line in the separation container. The leakage current impinging on the baffle plate is thus dusted, as a result of which the surface area of the leakage current is greatly increased and the evaporation of ethylene from the polyglycol is accordingly improved.

The ethylene evaporated from the polyglycol in the separation container is fed from the separation container via a head pipe into a storage container in order to be stored there. In contrast, the enriched polyglycol remaining at the bottom of the separation container can be fed into a sedimentation container for further cleaning. In such a sedimentation tank, the ethylene still bound in the polyglycol can evaporate under atmospheric pressure in order to then be returned to the compression process via a fan. The one remaining on the bottom of the still tank

Polyglycol is of such purity that it can be renewed

Lubrication can be used in the lubrication system.

Therefore, the purified polyglycol in one

Soil reservoir downstream reservoir saved from which it can be introduced into the lubricant channels of the compressors via lubricant lines and filters with the aid of lubricant pumps from the lubrication system.

The invention is based on a

Exemplary embodiment with reference to the Fig 1 naner explained. In Fig. 1 is a two-stage compressor system for the compression of ethylene in one

Polyethylene manufacturing process shown with a lubrication system to which the separation system according to the invention is coupled.

1, a two-stage compressor system 1 used in a polyethylene manufacturing process is driven by an electric motor 2. In this case, ethylene is pressurized to 215 bar via feed line 3 in four piston compressors 4 to 7 of a first stage. In the piston compressors 4 to 7 of the first stage, the ethylene is pre-compressed to 1250 bar and introduced via connecting lines 12 into four piston compressors 8 to 11 of a second stage. In the piston compressors of the second stage, the ethylene pressure is brought to a polymerization pressure between 1800 and 3000 bar elevated. The ethylene having the polymerization pressure is then introduced from the compressors 8 to 11 of the second stage via lines 14 into a polymerization reactor (not shown).

The lubrication system provided for the lubrication of the piston compressors has, separately for each stage, a lubricant pump 15, 15a in each case, the lubricants, in the present case polyglycol, via supply lines 16, 16a, 17, 17a, 18 (shown in phantom in FIG. 1). 18a, 19, 19a to the moving parts of the piston compressors 4-11. More specifically, polyglycol is fed from a reservoir, not shown, by means of the lubricant pumps 15, 15a via a feed line 16 to the compressor 10 and via a feed branch line 16a to the compressor 8, while polyglycol is fed via a feed line 17 to the compressor 11 and is further fed to the compressor 9 via a second feed branch line 17a. Similarly, the feed lines 18 and 19 lead to the respective compressors 7 and 6 and further via the feed branch lines 18a and 19a to the compressors 5 and 4.

The polyglycol supplied to each of the compressors via the feed lines 16-19 is applied to the components to be lubricated in the compressors via lubricant channels (not shown). Then the

Compressor leakage stream of polyglycol and ethylene led to the leakage lines 20 to 27 shown in Fig. 1, which in turn mouth in a leakage manifold 30, which leads the leakage current from the compressor system 1.

1 also shows that the leakage current is fed via the leakage collecting line 30 directly into a separating container 31, into which the leakage current guided in the leakage collecting line 30 is expanded. Because the polyglycol leaks from the compressors under high pressure and into the

Leakage manifold 30 flows in, the leakage current flowing in the leakage manifold 30 has a high internal energy. This internal energy of the leakage current is converted in the leakage manifold 30 into kinetic energy, which ensures that the leakage current strikes a baffle plate 32 at high speed and is atomized in the interior of the separating container 31. The baffle can e.g. are made from pressed grain bronze.

The atomization of the leakage current due to the impact on the baffle plate 32 leads to a considerable increase in the surface of the polyglycol-ethylene mixture, which promotes the evaporation of ethylene bound in the polyglycol. The ethylene now contained in gaseous form in the separating container 31 is passed via a head line 33 from the separating container 31 into a storage container 34, while the enriched polyglycol present at the bottom of the separating container 31 via a Bottom line 35 is passed to a calming tank 36, in which there is an atmospheric pressure. The polyglycol rests in this calming container 36 for the evaporation of ethylene residues remaining in the polyglycol. From the vault of the still tank 36, another head line 37 leads the ethylene evaporated from the polyglycol in the still tank back into the process circuit with the aid of a fan 38 provided in line 37, while the polyglycol collected in the still tank 36 is of such purity that it is used for lubrication again in the

Lubrication system can be used. For this purpose, the polyglycol is supplied from the sedimentation tank 36 through a bottom line 39 with the aid of a pump 40 and a filter 41 for cleaning solid and suspended matter to the reservoir already mentioned, from which the lubricant pumps 15, 15a of the lubrication system renew the polyglycol Feed use into the compressor system.

Claims

claims

1.Separation system for separating a leakage stream comprising a mixture of polyglycol and ethylene, which can be conducted from a lubrication system via a leakage manifold (30), with the aid of which a compressor system (1) for compressing ethylene is lubricated by means of polyglycol, the separation system being adaptive the leakage line (30) can be coupled, and the cleaned polyglycol drawn from the leakage current can be returned to the lubrication system via the separation system.

2. Separation system according to claim 1, wherein the leakage manifold

(30) of the lubrication system can be coupled to a separation container (31) of the separation system, in which the ethylene can be evaporated from the leakage flow led into the separation container (31).

3. Separation system according to claim 2, wherein the high internal energy caused by the high pressures in the compressor system (1) of the leakage current flowing into the separation container (31) can be released with the entry of the leakage current into the separation container (31).

4. Separation system according to claim 3, wherein in the separation container (31) for atomizing the high internal energy in the separation container

(31) entering leakage current, a baffle plate (32) is provided is opposite the mouth of the leakage manifold (30).

5. Separation system according to claim 4, wherein the baffle plate (32) is made of pressed grain bronze.

6. Separation plant according to an αer claims 3 to 5, wherein the ethylene evaporated in the separation container (31) via a head line

(33) from the separation container (31) into a storage container (34) can be guided.

7. Separation system according to one of claims 2 to 6, wherein the enriched polyglycol remaining at the bottom of the separation container (31) can be guided via a bottom line (35) into a settling container (36) in which the ethylene still bound in the polyglycol can be evaporated out under atmospheric pressure is.

8. Separation system according to claim 7, wherein the evaporated in the sedimentation tank (36) ethylene can be returned to the compression process via a head line (37) by means of a fan (38).

9. Separation system according to one of claims 7 or 8, wherein the polyglycol remaining on the bottom of the calming container (36) can be guided to a reservoir via a bottom line (39) by means of a pump (40) and via a filter (41).

10. Separation system according to claim 9, wherein the filter (41) is a sieve filter, a centrifugal filter or a similar mechanical filter.

11. Separation system according to claim 9 or 10, wherein starting from the reservoir, the polyglycol with the aid of lubricant pumps (15, 15a) of the lubrication system via lubricant lines (16, 16a, 17, 17a, 18, 18a, 19, 19a) in lubricant channels of compressors (4-11) of the compressor system (1) can be introduced.