WO2013178256A1

WO2013178256A1 - Compressor station

Info

Publication number: WO2013178256A1
Application number: PCT/EP2012/060128
Authority: WO
Inventors: Suhel Ahmad; Harald Benthin; Vladimir Danov; Andreas SCHRÖTER
Original assignee: Siemens Aktiengesellschaft
Priority date: 2012-05-30
Filing date: 2012-05-30
Publication date: 2013-12-05

Abstract

The invention describes a compressor station (100) for transferring a medium in a pipeline system. The compressor station (100) comprises a compressor (10) for transferring the medium within a pipeline (110) wherein the compressor (10) is disposed on a first shaft (11). A turbine (12) for driving the compressor (10) is disposed on a second shaft (13). Furthermore, the compressor station (100) comprises a power grid (200) and a power distribution means (15) for transferring mechanical power between the independently rotating first and second shaft (11, 13). The power distribution means (15) is adapted to supply electrical power to the power grid (200) or to draw electrical power from the power grid (200) according to a mechanical power difference between the rotating first and second shaft (11, 13).

Description

Compressor Station The invention relates to a compressor station for transferring a medium in a pipeline system. The compressor station comprises a compressor for transferring the medium within a pipeline and a turbine for driving the compressor. Compressor stations mainly are used for transferring gas or oil in a pipeline system. Typically high power compressors are used in combination with a gas turbine. Often the turbine and the compressor are disposed on a common shaft which al^¬ lows an easy construction. Due to a variable workload of the compressor the turbine must run also with variable workload. As a result, the efficiency of the compressor station de^¬ creases. Furthermore, shorter maintenance intervals are a re^¬ sult . To avoid efficiency decrease and to prolong maintenance in^¬ tervals it would be desireable to allow the gas turbine to run constantly whereby the workload of the compressor is still variable. A possible solution to this problem is to provide a gearbox between the compressor and the turbine. In this case, the turbine may be designed to meet 100 % of the gas compressor load. Another solution is to provide an additional generator for producing electrical energy. If the compressor has to be run with a smaller load than 100 %, the turbine remains still working at 100 % of load. The power difference between the turbine and the compressor will be transferred to the genera^¬ tor for producing electrical energy. This energy may be supplied to a power grid. A disadvantage of this solution is that the turbine has to be provided with two shafts for col^¬ lecting the compressor itself. It is an object of the present invention to provide a com^¬ pressor station which is functional and/or constructional improved to allow a turbine to run constantly while allowing a workload of a compressor to be variable.

This object is solved by a compressor station according to claim 1. Preferred embodiments are set out in the dependent claims . The invention provides a compressor station for transferring a medium in a pipeline system. Especially, the medium to be transferred in the pipeline is gas or oil. The compressor station comprises a compressor for transferring the medium within a pipeline wherein the compressor is disposed on a first shaft. A turbine for driving the compressor is disposed on a second shaft. Furthermore, the compressor station com^¬ prises a power grid. Last, a power distribution means for transferring mechanical power between the independently ro^¬ tating first and second shaft is provided. The means is adapted to supply electrical power to the power grid or to draw electrical power from the power grid according to a mechanical power difference between the rotating first and sec^¬ ond shaft. As a result, a compressor station is provided where the work^¬ load of the compressor can be varied while the efficiency of the compressor station is still high due to a constantly run^¬ ning turbine. An advantage of the compressor station accord^¬ ing to the invention is that a standard turbine can be used which has only one shaft connected to it. Furthermore, no gearboxes are needed.

In particular, the turbine used in the compressor station is a gas turbine. A turbine used in a compressor station accord- ing to the invention is in a power class of around 25 MW. If gas is transferred in the pipeline system the gas for power^¬ ing the turbine may be taken from the pipeline. In contrast, the power class of a compressor used in the compressor sta- tion according to the invention is around 13 MW. However, it is to be understood that the principle of the compressor sta^¬ tion according to the invention can be used with different power classes than the above mentioned.

According to a preferred embodiment, the power distribution means is represented by an electromagnetically variable transmission for transferring the power between the independently rotating first and second shaft. Having an electromag- netic variable transmission (EVT) the turbine's shaft power may be transferred either electrically or mechanically or in both ways simultaneously to the compressor of the power grid.

According to a preferred embodiment the electromagnetically variable transmission comprises a stator; a hollow cylindrical outer rotor and a cylindrical inner rotor, the inner rotor being disposed within a center aperture of the outer ro^¬ tor and independently rotatable within the outer rotor, and the outer rotor independently rotatable circumferentially about the inner rotor; the stator and the inner rotor have windings being energized by current conductors connected to the power grid and the outer rotor has a plurality of perma^¬ nent magnets or a squirrel cage facing an air gap between the outer rotor and the inner rotor. The electromagnetically var- iable transmission comprises two rotors which enable to transfer selectively mechanical and/or electrical power to the compressor and the power grid, respectively.

The outer rotor and the inner rotor may be simultaneously ro- tatable in one direction. Hence, the power of the second shaft connected to the turbine can be transferred to the first shaft connected to the compressor.

The windings of the inner rotor and the stator may be hollow and be passed through a cooling medium. The electromagnetic variable transmission can be provided with decreased size. Furthermore, the efficiency of the electromagnetic variable transmission can be increased. According to a further preferred embodiment the power trans^¬ mission from the turbine to the compressor may be achieved by electromagnetic forces between the outer rotor and the inner rotor. Accordingly, the supply of electrical power to the power grid or draw of electrical power from the power grid is achieved by electromagnetic forces between the inner rotor and the stator by operating them as a generator or a machine. Likewise, according to a further preferred embodiment the supply of electrical power to the power grid or the draw of electrical power from the power grid while simultaneously driving the compressor is achieved by controlling electromagnetic forces such that they are divided between the outer ro^¬ tor and the inner rotor as well as between the inner rotor and the stator. The distribution between the electrical and the mechanical power within the electromagnetic variable transmission is achieved by appropriate controlling of the current conductors connected to the stator and the inner ro^¬ tor .

According to an alternative solution the power distribution means comprises a generator being driven by the turbine and a motor being supplied by the generator and driving the compressor. The electricity produced by the generator can be used by the machine to drive the compressor. In this way it is much easier to transfer the electricity either to the power grid or to the compressor drive instead of using gearboxes or a coupler. According to a further preferred embodiment the first shaft may be connected to the compressor directly. Likewise, the second shaft may be connected to the turbine directly. This means that there is no gearbox between the first shaft in the compressor as well as the second shaft and the turbine. This ensures a simple construction of the compressor station.

The invention will be explained in more detail by reference to the accompanying figures. Fig. 1 shows a schematic view of a compressor station ac^¬ cording to a first embodiment.

Fig. 2 shows in a cross section a schematic view of an

electromagnetically variable transmission used in the compressor station according to the first embodiment .

Fig. 3 shows a schematic view of a compressor station ac^¬ cording to a second embodiment.

The compressor station 100 for transferring gas or oil in a pipeline system 110 comprises a compressor 10, a turbine 12, a power grid 200 and a power distribution means 15. The compressor 10 is used for transferring oil or gas within the pipeline 110 it is connected to. The compressor 10 is driven by a first shaft 11 which is connected to the power distribu^¬ tion means 15. The first shaft 11 and therefore the compres- sor 10 are driven by the turbine which is disposed on a sec^¬ ond shaft 13 connected to the power distribution means 15. The power grid 200 is connected via a lead 14 to the power distribution means 15. Generally, the power distribution means 15 is adapted for transferring mechanical power between the independently ro^¬ tating first and second shaft 11, 13. It is adapted to supply electrical power to the power grid 200 or to draw electrical power from the power grid 200 according to a mechanical power difference between the rotating first and second shafts 11, 13. Such a mechanical power difference between the rotating first and second shaft may result from the fact that the tur^¬ bine, in particular a gas turbine 12, is run constantly, i.e. with 100 % speed, while the workload of the compressor 10 is variable due to the amount of medium to be transported within the pipeline 110. The power distribution means 15 which either may be realized as an electromagnetically variable transmission 20 (EVT) or a combined generator 40/machine 41 combination is able to dis^¬ tribute the power generated by the compressor according to the workload of the compressor 10 between the compressor 10 and the power grid 200. Both solutions provide the advantage that no gearboxes are needed to let the workload of the com^¬ pressor 10 be variable while maintaining the efficiency of the compressor station 100.

Referring to Fig. 1 which illustrates a compressor station 100 using an electromagnetic variable transmission 20 as pow^¬ er distribution means 15, the shaft power of the turbine 12 can be transferred either electrically or mechanically or in both ways simultaneously to the compressor 10 and the power grid 200. A cross section through an electromagnetic variable transmission 20 illustrating the principle function of an electromagnetic variable transmission is shown in Fig. 2. The electromagnetic variable transmission 20 consists of a stator 21 connected to a housing 35, an outer rotor 25 and an inner rotor 30. The outer rotor 25 has a hollow cylindrical shape. The cylindrical inner rotor is disposed within a cen^¬ ter aperture 26 of the outer rotor 25 and is independently rotatable within the outer rotor 25. Likewise, the outer ro^¬ tor 25 is independently rotatable circumferentially about the inner rotor 30. While the inner rotor is connected to the se^¬ cond shaft 13 connected to the turbine 12, the outer rotor 25 is connected to the inner shaft 11 which drives the compres- sor 10. The stator 21 and the inner rotor 30 have windings which can be energized by current conductors 14a, 14b. They are connected to the power grid 200. The outer rotor has a plurality of permanent magnets facing an air gap between the outer rotor 25 and the inner rotor 30.

The power transmission from the turbine 12 to the compressor 10 is made by electromagnetic forces between the inner rotor 30 and the outer rotor 25. If, for example, the compressor 10 needs only 50 % of power provided by the turbine 12, than 50 % of the turbine's power will be transferred to the compres^¬ sor 10 while the rest (50 %) will be transferred to electri^¬ cal power in the stator 21 of the electromagnetic variable transmission. Controlling of power distribution is effected by the control circuit not shown in Fig. 2.

More detailed, the supply of electrical power to the power grid is achieved by electromagnetic forces between the inner rotor and the stator by operating them as a generator. Likewise, the supply of electrical power to the power grid while simultaneously driving the compressor is achieved by control^¬ ling electromagnetic forces such that they are divided be^¬ tween the outer rotor 25 and the inner rotor 30.

Even if in some cases the compressor 10 needs more power than the turbine 12 can deliver, the electromagnetic variable transmission can draw electrical energy from the power grid 200 to drive the shaft 11 in addition to the turbine 12. The draw of electrical power from the power grid is achieved by electromagnetic forces between the inner rotor and the stator by operating them as a machine. The draw of electrical power from the power grid while simultaneously driving the compres^¬ sor is achieved by controlling the electromagnetic forces such that they are divided between the inner rotor and the stator 21.

The efficiency of the compressor station may be further increased if hollow wirings are used through which the cooling medium will flow. The electromagnetic variable transmission can be realized with decreased size.

Referring to Fig. 3 the power distribution means 15 comprises a generator 40 which is driven by the shaft 13 connected to the turbine 12. The generator 40 produces electrical power which can be divided between a machine 41 connected to the shaft 11 to drive the compressor 10 or via the lead 14 to the power grid 200. Hence, electricity produced from the genera- tor 40 will be used by the electrical machine 41 to run the compressor 10. This embodiment allows an easy transfer of electrical power either to the power grid 200 or to the com^¬ pressor 10 instead of using the gearboxes or coupler.

As already mentioned, the compressor station according to the invention allows to run the turbine 12 constantly while the compressor can have variable loads. In this case less mainte^¬ nance is needed and the turbine runs in constant mode. As a further improvement a constant running turbine can build up a gas and steam process to increase the efficiency of the com^¬ pressor station additionally.

Claims

Patent Claims

1. A compressor station (100) for transferring a medium in a pipeline system, comprising

a compressor (10) for transferring the medium within a pipeline (110) wherein the compressor (10) is disposed on a first shaft (11);

a turbine (12) for driving the compressor (10) wherein the turbine is disposed on a second shaft (13);

a power grid (200);

a power distribution means (15) for transferring mechanical power between the independently rotating first and second shaft (11, 13), wherein the power distribu^¬ tion means (15) is adapted to supply electrical power to the power grid (200) or to draw electrical power from the power grid (200) according to a mechanical power difference between the rotating first and second shaft (11, 13) .

2. The compressor station according to claim 1, wherein the power distribution means (15) is represented by an electro- magnetically variable transmission (20) for transferring the power between the independently rotating first and second shaft (11, 13) .

3. The compressor station according to claim 2, wherein the electromagnetically variable transmission (20) comprises: a stator (21) ;

a hollow cylindrical outer rotor (25) and a cylindrical inner rotor (30), the inner rotor (30) being disposed within a center aperture (26) of the outer rotor (25) and independently rotatable within the outer rotor (25) , and the outer rotor (25) independently rotatable circum- ferentially about the inner rotor (30);

- the stator (21) and the inner rotor (30) having windings being energized by current conductors (14a, 14b) con^¬ nected to the power grid (200) and the outer rotor (25) having a plurality of permanent magnets or a squirrel cage facing an air gap between the outer rotor (25) and the inner rotor (30) .

4. The compressor station according to claim 3, wherein the outer rotor (25) and the inner rotor (30) are simultaneously rotatable in one direction.

5. The compressor station according to claim 3 or 4, wherein the windings are hollow which are passed through a cooling medium.

6. The compressor station according to one of the preceding claims 2 to 5, wherein the power transmission from the turbine (12) to the compressor (10) is achieved by electromag- netic forces between the outer rotor (25) and the inner rotor (30) .

7. The compressor station according to one of the preceding claims 2 to 6, wherein the supply of electrical power to the power grid (200) or the draw of electrical power from the power grid (200) is achieved by electromagnetic forces be^¬ tween the inner rotor (30) and the stator (21) by operating them as a generator or a machine.

8. The compressor station according to one of the preceding claims 2 to 7, wherein the supply of electrical power to the power grid (200) or the draw of electrical power from the power grid (200) while simultaneously driving the compressor (10) is achieved by controlling electromagnetic forces such that they are divided between the outer rotor (25) and the inner rotor (30) as well as between the inner rotor (30) and the stator (21) .

9. The compressor station according claim 1, wherein the pow- er distribution means (15) comprises a generator (40) being driven by the turbine (12) and a motor (41) being supplied by the generator (40) and driving the compressor (10) .

10. The compressor station according to one of the preceding claims, wherein the first shaft (11) is directly connected to the compressor (10) .

11. The compressor station according to one of the preceding claims, wherein the second shaft (13) is directly connected to the turbine (12) .

12. The compressor station according to one of the preceding claims, wherein the medium to be transferred is gas or oil.