Steam turbine and method for operating same

Abstract

A steam turbine having a low-pressure inner housing NDIG and a high-pressure inner housing HDIG within a steam turbine outer housing, a reheater downstream of the HDIG and upstream of the NDIG wherein the first steam inlet section of the HDIG faces the second steam inlet section of the NDIG, a process steam deflection section for deflecting process steam out of the first steam outlet section into a gap between an inner wall of the steam turbine outer housing and an outer wall of the HDIG and of the NDIG, a high-pressure sealing shell for sealing the upstream end-section of the HDIG, a low-pressure sealing shell for sealing the upstream end-section of the NDIG, the high-pressure sealing shell located adjacent to the low-pressure sealing shell, wherein process steam can be drawn from the HDIG and conveyed to a region between the high- and low-pressure sealing shells.

Claims

1. A steam turbine, comprising: a steam turbine outer housing, a high-pressure inner housing with a first process steam inlet section and with a first process steam outlet section for conducting process steam through the high-pressure inner housing from the first process steam inlet section to the first process steam outlet section in a first process steam expansion direction, a low-pressure inner housing with a second process steam inlet section and with a second process steam outlet section for conducting process steam through the low-pressure inner housing from the second process steam inlet section to the second process steam outlet section in a second process steam expansion direction, and an intermediate superheater for intermediate superheating of process steam which can be extracted downstream of the high-pressure inner housing and upstream of the low-pressure inner housing, wherein the high-pressure inner housing and the low-pressure inner housing are arranged within the steam turbine outer housing, wherein the high-pressure inner housing and the low-pressure inner housing are arranged such that the first process steam inlet section of the high-pressure inner housing faces toward the second process steam inlet section of the low-pressure inner housing, wherein downstream of the high-pressure inner housing, there is formed a process steam diverting section for diverting process steam from the first process steam outlet section in a direction counter to the first process steam expansion direction into a gap which extends between an inner wall of the steam turbine outer housing and an outer wall of the high-pressure inner housing and at least in certain sections between the inner wall of the steam turbine outer housing and an outer wall of the low-pressure inner housing, wherein the intermediate superheater is configured to extract the process steam from a location disposed downstream of the process steam diverting section, wherein at an upstream end section of the high-pressure inner housing, at which the first process steam inlet section is formed, there is arranged a high-pressure sealing shell for at least partially sealing off the upstream end section of the high-pressure inner housing, and, at an upstream end section of the low-pressure inner housing, at which the second process steam inlet section is formed, there is arranged a low-pressure sealing shell for at least partially sealing off the upstream end section of the low-pressure inner housing, and wherein the high-pressure sealing shell and the low-pressure sealing shell are arranged adjacent to one another, wherein the high-pressure inner housing is designed such that process steam can be extracted from the high-pressure inner housing and conducted into a region between the high-pressure sealing shell and the low-pressure sealing shell.

2. The steam turbine as claimed in claim 1, wherein the high-pressure sealing shell is designed such that a predefinable leakage mass flow can be conducted via the high-pressure sealing shell into ainto the region between the high-pressure sealing shell and the low-pressure sealing shell.

3. The steam turbine as claimed in claim 2, wherein the high-pressure sealing shell and the low-pressure sealing shell are designed and coordinated with one another such that the leakage mass flow via the high-pressure sealing shell is greater than a leakage mass flow via the low-pressure sealing shell.

4. The steam turbine as claimed in claim 3, wherein the leakage mass flow via the high-pressure sealing shell is at least 30% greater than the leakage mass flow via the low-pressure sealing shell.

5. The steam turbine as claimed in claim 1, wherein, at a downstream end section of the low-pressure inner housing, there is formed a sealing web for sealing off a steam turbine region between the downstream end section of the low-pressure inner housing and the steam turbine outer housing.

6. The steam turbine as claimed in claim 1, wherein the intermediate superheater is arranged outside the steam turbine outer housing.

7. A method for operating a steam turbine as claimed in claim 1, the method comprising: conducting process steam from a process steam source through the first process steam inlet section into the high-pressure inner housing, conducting the process steam from the first process steam inlet section to the first process steam outlet section, conducting the process steam through the first process steam outlet section from the high-pressure inner housing via the process steam diverting section and the gap to the intermediate superheater, extracting a proportion of the process steam from the high-pressure inner housing, expanding said proportion of the process steam to intermediate superheating parameters, and introducing the extracted process steam into the region between the high-pressure sealing shell and the low-pressure sealing shell.

8. The method for operating a steam turbine as claimed in claim 7, wherein the extracted process steam is leakage steam which is conducted via the high-pressure sealing shell into the region between the high-pressure sealing shell and the low-pressure sealing shell.

9. The steam turbine as claimed in claim 4, wherein the leakage mass flow via the high-pressure sealing shell is at least 50% greater than the leakage mass flow via the low-pressure sealing shell.

10. A steam turbine, comprising: a steam turbine outer housing; a high-pressure inner housing comprising a high-pressure sealing shell at an upstream end section thereof, and a low-pressure inner housing comprising a low-pressure sealing shell at an upstream end section thereof, both disposed within the steam turbine outer housing and arranged such that a first steam inlet section of the high-pressure inner housing faces toward a second steam inlet section of the low-pressure inner housing; a process steam diverting section configured to divert process steam exiting the high-pressure inner housing into a gap which extends between an inner wall of the steam turbine outer housing and an outer wall of the high-pressure inner housing and at least in certain sections between the inner wall of the steam turbine outer housing and an outer wall of the low-pressure inner housing; and an intermediate superheater configured to extract process steam from a location downstream of the process steam diverting section with respect to a direction of flow of the process steam that flows through the process steam diverting section, and to superheat the process steam; wherein the high-pressure inner housing is designed such that process steam can be extracted from the high-pressure inner housing and conducted into a region between the high-pressure sealing shell and the low-pressure sealing shell.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further measures that improve the invention will emerge from the following descriptions of various exemplary embodiments of the invention, which are schematically illustrated in the figures. All features and/or advantages that emerge from the claims, from the description or from the drawing, including design details and spatial arrangements, may be essential to the invention both individually and in various combinations. In the drawing:

(2) FIG. 1 shows the basic construction of a steam turbine according to the invention;

(3) FIG. 2 shows the detail view Z, in which the method according to the invention is discussed in more detail.

DETAILED DESCRIPTION OF INVENTION

(4) FIG. 1 shows the basic construction of a steam turbine 1 according to the invention. The steam turbine 1 has a steam turbine outer housing 20, in which a high-pressure inner housing 30, a low-pressure inner housing 40 in the form of a medium-pressure inner housing, and a further low-pressure inner housing 90 are situated. Arranged upstream of the high-pressure inner housing 30 is a fresh steam or process steam source 10 for the supply of process steam to the high-pressure inner housing 30. The high-pressure inner housing 30 has a first process steam inlet section 31 and a first process steam outlet section 32 for conducting process steam through the high-pressure inner housing 30 from the first process steam inlet section 31 to the first process steam outlet section 32 in a first process steam expansion device 33. The low-pressure inner housing 40 has a second process steam inlet section 41 and a second process steam outlet section 42 for conducting process steam through the low-pressure inner housing 40 from the second process steam inlet section 41 to the second process steam outlet section 42 in a second process steam expansion device 43. The steam turbine 1 furthermore has an intermediate superheater 50 which is arranged downstream of the high-pressure inner housing 30 and upstream of the low-pressure inner housing 40. The arrangement relates here not to a spatial arrangement but to an arrangement in relation to a flow.

(5) As illustrated in FIG. 1, the high-pressure inner housing 30 and the low-pressure inner housing 40 are arranged such that the first steam inlet section 31 of the high-pressure inner housing 30 faces toward the second steam inlet section 41 of the low-pressure inner housing 40.

(6) Downstream of the high-pressure inner housing 30, the steam turbine 1 has a process steam diverting section 60 for diverting process steam from the first steam outlet section 32 in a direction counter to the first steam expansion device 33 into a gap 70 of the steam turbine 1. The gap 70 extends between the steam turbine outer housing 20 and the high-pressure inner housing 30 and at least in certain sections between the steam turbine housing 20 and the low-pressure inner housing 40. At a downstream end section of the low-pressure inner housing 40, there is formed a sealing web 80 for sealing off a steam turbine region between the downstream end section of the low-pressure inner housing 40 and the steam turbine outer housing 20. The intermediate superheater 50 is arranged outside the steam turbine outer housing 20. The high-pressure inner housing 30 and the low-pressure inner housing 40 are provided as separate components in a common steam turbine outer housing 20.

(7) At the upstream end section of the high-pressure inner housing 30, at which the first process steam inlet section 31 is formed, there is arranged a high-pressure sealing shell 34 for partially sealing off the downstream end section of the high-pressure inner housing 30. Furthermore, at the upstream end section of the low-pressure inner housing 40, at which the second process steam inlet section 41 is formed, there is arranged a low-pressure sealing shell 44 for partially sealing off the upstream end section of the low-pressure inner housing 40. The high-pressure sealing shell 34 and the low-pressure sealing shell 44 are arranged adjacent to one another. At a downstream end section of the high-pressure inner housing 30, at which the first process steam outlet section 32 is formed, there is arranged a further high-pressure sealing shell 35 for at least partially sealing off the downstream end section of the high-pressure inner housing 30. The high-pressure sealing shell 34 is configured and designed such that, via it, a predefinable leakage mass flow can emerge and be conducted into the region 110 between the high-pressure sealing shell 34 and the low-pressure sealing shell 44. In the case of a predefined steam pressure and steam temperature, the sealing shell and/or the sealing gap can be configured such that a predefinable leakage mass flow passes through the sealing shell. The high-pressure sealing shell 34 and the low-pressure sealing shell 44 are coordinated with one another such that the leakage mass flow via the high-pressure sealing shell 34 is greater than the leakage mass flow via the low-pressure sealing shell 44. Preferably, the leakage mass flow via the high-pressure sealing shell 34 is at least 30%, advantageously at least 50%, greater than the leakage mass flow via the low-pressure sealing shell 44.

(8) FIG. 2 shows a detail view Z from FIG. 1. A method according to the invention for operating a steam turbine according to the invention will be discussed below on the basis of FIG. 2 and with reference to FIG. 1 and the descriptions given in relation thereto.

(9) In order to seal off the gap between the shaft 100 and the upstream end section of the high-pressure inner housing 30, a high-pressure sealing shell 34 is arranged at the end section of the high-pressure inner housing 30. A low-pressure sealing shell 44 is arranged for sealing off the gap between the upstream end section of the low-pressure inner housing 40 and the shaft 100. The high-pressure sealing shell 34 and the low-pressure sealing shell 44 are arranged adjacent to one another. During the operation of the steam turbine, it is initially the case that process steam from the process steam source 10 is conducted through the first process steam inlet section 31 into the high-pressure inner housing 30. The process steam is subsequently conducted from the first process steam inlet section 31 to the first process steam outlet section 32, and is thereafter conducted through the first process steam outlet section 32 from the high-pressure inner housing 30 via the process steam diverting section 60 into the gap 70 to the intermediate superheater 50. Here, the process steam is conducted through the gap 70 in order to cool the steam turbine outer housing 20 or the steam turbine 1 along the high-pressure inner housing 30 and along the low-pressure inner housing 40. After the process steam has been heated in the intermediate superheater 50 at constant pressure to a predefined temperature, the heated or superheated process steam is conducted from the intermediate superheater 50 through the second process steam inlet section 41 into the low-pressure or medium-pressure inner housing. From there, the process steam is conducted, in an unchanged expansion direction, into the further low-pressure inner housing 90. There, the process steam can expand further and ultimately condense. In order to prevent the cooled steam that is supplied to the intermediate superheating 50 from being drawn into the gap between the high-pressure sealing shell 34 and the low-pressure sealing shell 44 and into the low-pressure inner housing 40 owing to the pressure loss in the intermediate superheating process, steam is extracted from the first high-pressure inner housing 30 and is directly throttled to intermediate superheating parameters without performing work, and said steam is conducted directly into the gap between the high-pressure sealing shell 34 and the low-pressure sealing shell 44.

(10) In this way, the low-pressure inner housing 40 and that region 110 of the shaft 100 which is situated between the high-pressure sealing shell 34 and the low-pressure sealing shell 44 can be locally warmed. In order to extract the hot steam from the high-pressure inner housing 30, an opening in the high-pressure inner housing 30 and a corresponding pipeline, can be provided. The steam can however be extracted from the inner housing particularly easily, and without additional outlay in terms of construction, via the high-pressure sealing shell 34. For this purpose, the gap of the high-pressure sealing shell 34 must be configured correspondingly. The hot steam can then pass from the high-pressure inner housing 30 directly into the intermediate space between the first high-pressure sealing shell 34 and the second low-pressure sealing shell 44. Since the steam that flows out via the high-pressure sealing shell 34 has almost fresh steam parameters, it can be utilized for warming the region 110 between the high-pressure sealing shell 34 and the low-pressure sealing shell 44. This yields a temperature distribution which is positive in terms of rotor dynamics and in terms of rotor mechanics. The pressure is higher on the outer side of the low-pressure inner housing 40 than on the inner side, the reason for this being the pressure loss in the gap that leads to the intermediate superheating 50. The process steam that is extracted from the high-pressure inner housing 30 and conducted in the region 110 between the high-pressure sealing shell 34 and the low-pressure sealing shell 44 is thus drawn into the low-pressure inner housing 40, and serves there for warming the low-pressure inner housing 40. The high-pressure sealing shell 34 and the low-pressure sealing shell 44 are coordinated with one another such that the process steam that flows out via the high-pressure sealing shell 34 is at least 30%, advantageously at least 50%, greater than the leakage mass flow via the low-pressure sealing shell 44. The difference in the mass flows gives rise to a sealing mass flow which prevents the ingress of cold steam, which is flowing to the intermediate superheater 50, into the high-pressure sealing shell 34.