METHOD FOR SHORTENING THE START-UP PROCESS OF A STEAM TURBINE

Abstract

A method for shortening the start-up process of a steam turbine is provided which has a turbine housing and turbine components which are provided inside the turbine housing. The turbine components during operation come into contact with hot steam which flows through the turbine housing and include a turbine shaft which passes axially through the turbine housing. Sealing regions, which during operation of the steam turbine are acted upon by seal steam, are formed between the turbine shaft and the turbine housing. Thermal energy is fed to the steam turbine during a shutdown of said steam turbine, wherein seal steam is fed to the interior of the turbine housing during the shutdown of the steam turbine in order to heat and/or to keep warm the turbine components which are provided in the interior of the turbine housing.

Claims

1-8. (canceled)

9. A method for shortening the start-up process of a steam turbine which has a turbine housing and turbine components which are provided inside the turbine housing, which turbine components during operation come into contact with hot steam which flows through the turbine housing and include a turbine shaft which passes axially through the turbine housing, wherein sealing regions, which during operation of the steam turbine are acted upon by seal steam, are formed between the turbine shaft and the turbine housing, and wherein thermal energy is fed to the steam turbine during a shutdown of said steam turbine, wherein seal steam is fed to the interior of the turbine housing during the shutdown of the steam turbine in order to heat and/or to keep warm the turbine components which are provided in the interior of the turbine housing, wherein the steam turbine has two turbine stages which are provided in series in the turbine housing, and a drainage line, which can be shut off, is connected to the turbine housing between the turbine stages, wherein during the shutdown of the steam turbine the steam which is contained in the turbine housing is sucked out via the drainage line and at the same time seal steam, which is fed to the sealing regions, is sucked from both axial end regions of the turbine housing into the turbine housing toward the drainage line.

10. The method as claimed in claim 9, wherein the seal steam is fed to the interior of the turbine housing at a temperature of at least 200° C.

11. The method as claimed in claim 9, wherein during the sucking out of steam from the interior of the turbine housing via the drainage line the steam lines which are connected on the inflow side and outflow side to the turbine housing and serve for the conducting of hot steam during operation, are closed.

12. The method as claimed in claim 9, wherein during the introduction of seal steam with the steam turbine shut down, the turbine shaft is slowly rotated in order to uniformly distribute the seal steam in the interior of the turbine housing.

13. The method as claimed in claim 9, wherein the turbine housing is provided on its outer side with a thermal insulation during the shutdown and/or is heated from the outside.

14. The method as claimed in claim 9, wherein an internal temperature of the steam turbine and/or the surface temperature of a turbine component which is provided inside the turbine housing is detected and heating by feeding seal steam during the shutdown of the steam turbine is initiated if the detected temperature lies below a predetermined limit value.

15. The method as claimed in claim 14, wherein heating by feeding seal steam during the shutdown of the turbine is interrupted if the detected temperature lies above a corresponding upper limit value.

16. The method as claimed in claim 9, wherein the seal steam is fed to the interior of the turbine housing at a temperature of at least 250° C.

17. The method as claimed in claim 9, wherein the seal steam is fed to the interior of the turbine housing at a temperature of at least 300° C.

Description

BRIEF DESCRIPTION

[0014] Some of the embodiments will be described in detail, with reference to the following FIGURES, wherein like designations denote like members, wherein:

[0015] The drawing shows a schematic view of a steam turbine plant according to embodiments of the present invention.

DETAILED DESCRIPTION

[0016] An exemplary embodiment of the invention is explained below with reference to the attached drawing. In the drawing, the single FIGURE shows a schematic view of a steam turbine plant 1 according to embodiments of the present invention. This comprises two steam turbines 2, 3 or steam turbine units which are connected in series, specifically an HP/IP-steam turbine 2 and an LP-steam turbine 3. In this case, the HP/IP-steam turbine 2 forms a high-pressure (HP-) turbine stage 2a and an intermediate-pressure (IP-) turbine stage 2b of the steam turbine plant 1, whereas a LP-steam turbine 3 constitutes the low-pressure (LP-) turbine stage of the steam turbine plant 1. To this end, the LP-turbine 3 is connected on the inlet side to the outflow side of the intermediate-pressure stage 2b of the HP/IP-steam turbine 2 via a crossover pipe 4. In this crossover pipe 4, provision is made for a shut-off valve 5 via which the crossover pipe 4 can be closed off.

[0017] The HP/IP-steam turbine 2 and the LP-steam turbine 3 have in each case a turbine shaft 6, 7 which are mounted in turbine housings—not shown in more detail—and are customarily sealed in relation to the turbine housings via corresponding sealing regions 8.

[0018] The HP/IP steam turbine 2 of the steam turbine plant 1 is connected on the inflow side to a live steam feed line 9. Arranged in this is a valve 10 via which said live steam feed line 9 can be shut off.

[0019] The HP-section 2a of the HP/IP-steam turbine is connected on the outflow side to a steam discharge line 17 which during nominal operation feeds the cooled HP-exhaust steam of the reheater to the boiler. Arranged in this so-called cold reheat line is a valve, in this case a check valve 18, via which the steam discharge line 17 can be shut off.

[0020] Furthermore, a drainage line 11 is connected to the turbine housing of the HP/IP-steam turbine 2 between the HP-stage 2a and the IP-stage 2b. Provision is made in this for a shut-off valve 12 via which the drainage line 11 can be opened or closed. The drainage line 11 serves for connecting the turbine housing to a condenser—not shown. In this case, a delivery device—not shown either—is provided in the drainage line 11 or is assigned to the condenser, via which steam can be sucked from the interior of the turbine housing and delivered to the condenser.

[0021] The steam turbine plant 1 also comprises a seal steam source 13 which feeds seal steam to the sealing regions 8 via corresponding seal steam lines 14.

[0022] Also provided inside the turbine housing of the HP/IP-turbine stage 2 are temperature sensors 15 which are data-technologically connected to a control device 16 via which all the functions of the steam turbine plant 1 are controlled. The temperature sensors 6 serve for detecting the temperature in the turbine housing.

[0023] During the starting up and warming up of the steam turbine plant 1, thermal expansions and thermal stresses associated therewith could occur in the turbine housings of the two steam turbines 2, 3 themselves and in the turbine components which are provided inside the turbine housing. These occur particularly in the turbine shafts 6, 7 since these have the largest mass. The problem is particularly severe in the HP-turbine stage 2a and in the IP-turbine stage 2b of the first steam turbine 2. In order to avoid such thermal stresses, during the shutdown of the first steam turbine 2 hot seal steam is fed to the interior of the turbine housing of this steam turbine 2 so that the turbine shaft 6 and also the additional turbine components which are provided in the turbine housing are kept at a temperature which ensures that excessively severe thermal stresses are avoided if the steam turbine plant 1 is put into operation again and therefore the first steam turbine 2 is exposed to the admission of live steam again. In this case, the turbine shaft 6 is slowly rotated so that the seal steam can be uniformly distributed in the interior of the turbine housing.

[0024] The feed of seal steam is carried out automatically if the temperature which is detected by the temperature sensors 15 falls below a predetermined limit value, and it is interrupted again if the determined temperature lies above an upper limit value. Alternatively, it is possible to introduce seal steam continuously into the turbine interior.

[0025] The feed of seal steam is carried out in this case in a way that via the drainage line 11 the seal steam, which is fed continuously to the sealing regions 8 even during the shutdown of the steam turbine 2, is sucked by means of the delivery device from the two end regions of the steam turbine 2 into the turbine housing. In the process, the live steam valve 10 shuts off the live steam feed line 9, and the crossover pipe 4 is closed off by means of the shut-off valve 5.

[0026] Consequently, the turbine housing is exposed to a throughflow of seal steam from the axial end regions of the turbine housing toward the middle, which seal steam is then sucked out via the drainage line 11 between the HP-turbine stage 2a and the IP-turbine stage 2b to the condenser.

[0027] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0028] For the sake of clarity, it is to be understood that the use of ‘a’ or ‘an’ throughout this application does not exclude a plurality, and ‘comprising’ does not exclude other steps or elements.