EP1999376A1

EP1999376A1 - Method for operating a compressor unit and associated compressor unit

Info

Publication number: EP1999376A1
Application number: EP07727230A
Authority: EP
Inventors: Gaston Mathijssen; Mark Van Aarsen
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2006-03-24
Filing date: 2007-03-22
Publication date: 2008-12-10
Also published as: NO20084446L; WO2007110368A1; RU2008142114A; CN101410625A; US20090311108A1; US8262365B2; RU2396465C2; BRPI0709145A2

Abstract

The invention relates to a method for operating a compressor unit (1), in particular for underwater operation. The aim of the invention is to minimise the risk of gas hydrate formation during the compression process. To reduce said risk, according to the method components of the compressor unit (1) are supplied with anti-freeze (73) and/or anti-freeze (73) is injected into the flow path of the conveyed medium to be compressed (natural gas (NG)). The invention also discloses a compressor unit, which operates according to said method.

Description

description

Method for operating a compressor unit, compressor unit

The invention relates to a method for operating a compressor unit, in particular for underwater operation. In addition, the invention relates to a compressor unit, in particular for underwater operation, comprising a compressor and an electric motor, which

Compressor unit comprising a housing having an inlet and an outlet for the conveying medium with a rotational axis about which a rotor of the compressor unit is rotatable.

Recent developments in the field of compressor construction are also focused on subse- quent large

Compressor, which should serve the promotion of natural gas. Due to the special operating conditions, in particular because of the very limited accessibility both for maintenance purposes and by means of supply lines, the professional world faces great challenges. Relevant environmental regulations prohibit any material exchange between the units to be installed and the surrounding seawater. In addition, the seawater is an aggressive medium and extreme pressure and temperature conditions can be found in the different sea depths. Another requirement is that the aggregates on the one hand have an extremely long service life and on the other hand have to be designed virtually maintenance-free. To make matters worse, a significant contamination of the partially chemically aggressive medium to be promoted.

A compressor unit of the aforementioned type is already known from international patent application WO 02/099286 A1. With the objective of uncompromising simplification to reduce maintenance and at the same time high life is proposed there, the compressor rotor with the To make motor rotor in one piece and to store each end by means of only two radial bearings.

In addition, it is known from the European patent application EP 1 074 746 B1 to equip a turbocompressor with three radial bearings, wherein the motor rotor is connected by means of a coupling with the compressor rotor.

The compression of fluids can be problematic near the freezing point. In the production of natural gas, the development of gas hydrates is facing considerable problems. Gas hydrates are ice-like inclusion compounds in which small guest molecules, such as noble gases and various natural gas constituents, are enclosed in a cage by water molecules. Even with small amounts of liquid water and temperatures of beispielsweiselO ⁰ C must be expected with a hydrate formation. Presumably, the severe gas catastrophe in 1988 on the Norwegian North Sea drill rig Piper Alpha was due to such hydrate formation. Significant additional operating costs for natural gas production are also caused by gas hydrate deposits as they build up clogging in pipelines.

The invention has the object to provide a method for operating a compressor and a compressor unit, which minimizes the risk of gas hydrate formation, for example in the undersea production of natural gas, as far as possible.

To achieve the object, a method for operating a compressor unit according to claim 1 and a compressor unit according to claim 11 is proposed according to the invention. The respective dependent claims contain advantageous developments of the invention.

A particular advantage of the invention lies in the reliable protection against hydrate formation due to the injection of antifreeze. In this way Both vulnerable components of the compressor unit can be protected as well as the entire conveying path starting from the point of injection of the fluid to the later deposition thereof. The method is therefore also particularly expedient because, in the context of the chemical treatment of natural gases in a subsequent to the compressor unit after a pipeline base station, a separation of undesirable additives anyway. The reliability gained manifests itself both in a higher availability of the compressor and in a high degree of safety against clogging hydrate formation in the pipeline which adjoins the compressor unit.

The injection of antifreeze can be done in the intake or directly in the compressor. A

Loading of components of the compressor unit with the antifreeze is particularly useful for the bearings, the electric motor and other moving components. If there is a particular risk of hydrate formation in the overflow region of individual compressor stages, injection of antifreeze may also be expediently carried out here. The primary field of application of the invention is the extraction of natural gas, since the risk of the formation of gas hydrates is relatively high here.

In particular, various alcohols are able to ensure safety against freezing of the gases. Both for economic and technical reasons, the injection of methyl ethylene glycol is useful.

A slightly more economical option to gain a security against the formation of hydrate lies in it before each start of the

Compressor unit to inject an antifreeze at the critical points of the compressor unit, in particular at the previously mentioned points. An advantageous development of the invention provides that before each scheduled machine stop a quantity of antifreeze is injected at the sensitive points of the compressor unit. Particularly useful is the use of antifreeze both before each start and before each machine stop. In the case of emergency stop of the compressor unit, the fastest possible stop of the machine is in the foreground of interest, so that a previous injection of the

Antifreeze is not likely to be possible. Another possibility is to initiate the injection of the antifreeze at the same time as the initiation of the machine stop.

In the following, the invention is based on a special

Embodiment with reference to drawings described in more detail. The embodiment shown is merely illustrative of an example of the invention. It shows :

Figure 1 is a schematic representation of a

Longitudinal section through a compressor unit according to the invention and the essential adjacent modules, which is operated by the method according to the invention.

Figure 1 shows schematically a section along a compressor unit 1 according to the invention, which has as essential components a motor 2 and a compressor 3 in a gas-tight housing 4. The housing 4 houses the engine 2 and the compressor 3. In the region of the transition from the engine 2 to the compressor 3 is the

Housing 4 is provided with an inlet 6 and an outlet 7, wherein through the inlet 6 by means of a suction nozzle 8, the fluid to be compressed is sucked and flows through the outlet 7, the compressed fluid.

The compressor unit 1 is arranged vertically in operation, wherein a motor rotor 15 of the motor 2 are united via a compressor rotor 9 of the compressor 3 to a common shaft 19 which rotates about a common vertical axis of rotation 60. The motor rotor 15 is mounted in a first radial bearing 21 at the upper end of the motor rotor 15.

The compressor rotor 9 is mounted by means of a second radial bearing 22 in the lower position.

At the upper end of the common shaft 19 - ie at the upper end of the motor rotor 15 - a thrust bearing 25 is provided. The radial bearings and the thrust bearing work electromagnetically and are each encapsulated. The radial bearings extend in the circumferential direction about the respective bearing point of the shaft 19 and are in this case 360 ° circumferentially and undivided.

The compressor 3 designed as a centrifugal compressor has three compressor stages 11 which are in each case connected by means of an overflow 33. The resulting at the compressor stages 11 pressure differences provide for a thrust on the compressor rotor 9, which transmits to the motor rotor 15 and against the weight of the resulting entire rotor of the compressor rotor 9 and motor rotor 15, directed, so that in nominal operation as far as possible thrust balance he follows. In this way, the thrust bearing 25 can be dimensioned comparatively smaller than in a horizontal arrangement of the rotation axis 60th

The electromagnetic bearings 21, 22, 25 are cooled by means of a cooling system not shown in detail to the operating temperature, wherein the cooling system provides a tap in an overflow 33 of the compressor 3. From the tap a part of the pumped medium, which is preferably natural gas, passed through a filter by means of pipes and then through two separate pipes to the respective outer

Bearings (first radial bearing 21 and second radial bearing 22 and thrust bearing 25) out. This cooling by means of the cold pumped medium (80) saves additional supply lines. The motor rotor 15 is surrounded by a stator 16, which has an encapsulation, so that the aggressive conveying medium 80 does not damage windings of the stator 16. In this case, the encapsulation is preferably designed so that it can bear the full operating pressure. This is also because a separate cooling is provided for the stator, in which a separate cooling medium circulates.

The compressor rotor 9 expediently has a compressor shaft 10 on which the individual compressor stages 11 are mounted. This can preferably be done by means of a thermal shrinkage fit. Likewise, a positive connection, for example by means of polygons possible. Another embodiment provides for a fusion of different compressor stages 11 to each other, from which a one-piece compressor rotor 9 results.

The delivery medium 80 or natural gas NG first passes from the natural reservoir into a

Condensate 81, which condensates 82, among other water, separated from the gaseous phase. The condensates 82 pass into a condensate line 84, into which also a subsequent dewatering line 95 opens, which introduces condensates separated in the compressor unit into the condensate line 84. The condensates 82 are conveyed by a condensate pump 85 into a mixing unit 86, in which mixing with the compressed natural gas NG or

Delivery medium 80 takes place. The resulting mixture is conveyed into a pipeline 87 towards a base station 89.

The compressor unit 1 has a system for distributing antifreeze 73 comprising distribution lines 94 and injection modules 72. The antifreeze 73 is conveyed from a collection tank 92 by means of a metering pump 93 to the various injection modules 72 on the compressor unit 1. By means of the injection modules 72 locally the first radial bearing 21, the thrust bearing 25, the second radial bearing 22, the overflows 33 are acted upon. To the

Intake manifold 8 is another injection module 72, by means of which the antifreeze 73 is injected directly into the sucked in conveying medium 80.

The injected antifreeze 73 is partially, namely as far as deposited in the compressor unit 1, by a drainage 96 (at the "single-drain point") of

Compressor unit 1 discharged into the drainage line 95. The remainder is conveyed together with the compressed natural gas NG through the outlet 7 into the mixing unit 86. Through the pipeline 87, the antifreeze 73, the natural gas NG and the condensate 82 are conveyed to the base station 89 to the earth's surface. Hydrate formation in the pipeline 87 is excluded due to the antifreeze 73 carried along. Before reaching the base station 89, a further condensate separator 88 provides for a drying of the natural gas NG, the condensate including the antifreeze 73 entering a conditioner 90, in which the antifreeze 73 is separated from the remaining condensate 82. The treated antifreeze 73 passes through a return line 91 along the pipeline 87 back into the collection tank 92. The closed circuit of the

Antifreeze 73 ensures safety against hydrate formation on the one hand and compliance with relevant environmental standards on the other hand.

Claims

claims

1. A method for operating a compressor unit (1), in particular for underwater operation, characterized in that components of the compressor unit (1) with

Antifreeze (73) are acted upon and / or in the flow path of the pumped medium to be compressed (natural gas NG) an antifreeze (73) is injected.

2. The method according to claim 1, characterized in that the antifreeze (73) directly into the compressor (3) of the compressor unit (1) is injected.

3. The method according to claim 1, characterized in that the antifreeze (73) is injected directly into an intake (8) for the pumped medium (natural gas NG).

4. The method according to any one of the preceding claims, characterized in that

Bearings (radial bearings 21, 22, thrust bearing 25) or a motor (2) with the antifreeze (73) are acted upon.

5. The method according to any one of the preceding claims, characterized in that

Antifreeze (73) in an overflow (33) between two compressor stages (11) of the compressor (3) of the compressor unit (1) is injected.

6. The method according to any one of the preceding claims, characterized in that the medium is natural gas (NG).

7. The method according to any one of the preceding claims, characterized in that the antifreeze (73) is methyl ethylene glycol (MEG).

8. The method according to any one of the preceding claims, characterized in that the antifreeze (73) is injected before the start of the compressor unit (1).

9. The method according to any one of the preceding claims, characterized in that the antifreeze (73) is added only before the start of the compressor unit (1).

10. The method according to any one of the preceding claims, characterized in that the antifreeze (73) is added before a machine stop of the compressor unit (1).

11. The method according to any one of the preceding claims, characterized in that the antifreeze (73) is added only before the start and before the machine stop the compressor unit (1).

12. compressor unit for operation according to the method according to any one of the preceding claims, characterized in that on the intake manifold (8) and / or at least one

Bearing (radial bearings 21, 22, thrust bearing 25) and / or on the motor (2) and / or at least one overflow (33) between two compressor stages (11) at least one injection module (72) is arranged, by means of which Antifreeze (73) can be injected into the flow path of the pumped medium to be compressed or the corresponding component with antifreeze (73) can be acted upon.