Patent Application
20130156540
Steam turbine systems are often an integral portion of a power plant. In some instances, the steam turbines can also be a part of a combined cycle power plant which also includes one or more gas turbines. Thermal energy is used to produce steam which drives the steam turbines. The steam turbines drive a generator which produces electricity.
The steam turbine system can include a high pressure steam turbine, an intermediate pressure steam turbine and a low pressure steam turbine, all of which are connected to a common rotating shaft that drives a generator. In some instances, the different steam turbines could be coupled to different shafts which drive different generators. Regardless, seals are used to seal the steam turbines to the rotating shaft.
The seals which seal the steam turbines onto a rotating shaft require a certain amount of steam pressure in order to provide an effective seal. The seals used on high pressure steam turbines and intermediate pressure steam turbines typically receive enough pressure from the associated turbines so that they provide an effective seal. However, in some instances, and under some operating conditions, the low pressure steam turbine may not be capable of providing enough pressure to its seals to ensure an effective seal. As a result, many steam turbine systems are configured so that steam can be routed from the seals used on the high pressure and intermediate pressure steam turbines to the seals used on the low pressure steam turbine so that the low pressure steam turbine seals can provide an effective seal.
Inlet steam is provided to the high pressure steam turbine and is used to generate a motive force. Steam exiting the high pressure steam turbine 110 is routed to a reheater. Steam from the reheater is then routed to the intermediate pressure steam turbine 120. The steam passes through the intermediate pressure turbine 120 and then through the low pressure steam turbine 130, and ultimately exits to a condenser.
As explained above, during some operational conditions, the low pressure steam turbine 130 may not be capable of providing sufficient pressure to the low pressure seals 132 to ensure the seals 132 are effective. For this reason, the system also includes a steam seal header 150 which collects steam from the high pressure seals 112, 114 and the intermediate pressures seals 122. The steam routed to the steam seal header 150 is then delivered to the low pressure seals 132 so that the low pressure seals 132 can effectively seal the low pressure steam turbine 130.
Any excess steam collected in the steam seal header 150 which is not required by the low pressure seals 132 is routed to the condenser. Unfortunately, routing this excess steam to the condenser essentially wastes the energy present in this high temperature, high pressure steam. The steam collected in the steam seal header 150 still has sufficient thermal energy that it could have been used to produce work. As a result, configuring the steam turbine system as illustrated in
The steam collected from the high pressure seals 112, 114 and the intermediate pressure seals 122 is at a relatively high temperature and pressure. Often, the temperature and pressure of this collected steam is too high to be directly used in the low pressure steam turbine 130. For this reason, an attemperator 260 is provided between the steam seal header 250 and the low pressure steam turbine 130. The attemperator 260 lowers the temperature and pressure of the steam collected from the high pressure seals 112, 114 and the intermediate pressure seals 122 to a temperature and pressure that is suitable for introduction into the low pressure steam turbine 130.
Although the configuration illustrated in
In a first aspect, the invention is embodied in a method of utilizing steam provided by a seal of a high pressure steam turbine or a seal of an intermediate pressure steam turbine includes receiving a first flow of steam from at least one of a seal of a high pressure steam turbine and a seal of an intermediate pressure steam turbine in a steam seal header. A second flow of steam is received from a first location in a low pressure steam turbine in the steam seal header. A third flow of steam is provided from the steam seal header to a second location in the low pressure steam turbine, wherein the third flow of steam comprises a mixture of the first and second flows of steam.
In a second aspect, the invention is embodied in a steam seal header that includes a main body configured to hold a volume of steam, a first inlet into the main body that is configured to receive a first flow of steam from at least one of a seal of an intermediate pressure steam turbine and a seal of a high pressure steam turbine, and a second inlet into the main body that is configured to receive a second flow of steam from a first location in a low pressure steam turbine. The steam seal header also includes a first outlet from the main body that is configured to output a third flow of steam from the main body to a second location in the low pressure steam turbine, and a second outlet from the main body that is configured to output a fourth flow of steam to a seal of the low pressure steam turbine.
In a third aspect, the invention is embodied in a steam turbine system. The system includes a high pressure steam turbine, at least one high pressure seal for the high pressure steam turbine, a low pressure steam turbine, and a steam seal header that receives a first flow of steam from the high pressure seal and a second flow of steam from the low pressure steam turbine. The steam seal header outputs a third flow of steam to the low pressure steam turbine, wherein the third flow of steam comprises a mixture of the first and second flows of steam.
The steam turbine system includes a high pressure steam turbine 110 connected to a rotating shaft 100. In addition, an intermediate pressure steam turbine 120 and a low pressure steam turbine 130 are also coupled to the rotating shaft 100. The rotating shaft 100 drives a generator 140.
High pressure seals 112, 114 are provided to seal the high pressure steam turbine 110. Intermediate pressure seals 122 are provided to seal the intermediate pressure steam turbine 120. Low pressure seals 132 are provided to seal the low pressure steam turbine 130.
As explained above, under some operating conditions the low pressure steam turbine 130 cannot provide steam at a sufficiently high pressure to the low pressure seals 132 to ensure the seals 132 are effective. For this reason, steam is collected from the high pressure seals 112, 114 and the intermediate pressure seals 112 in a steam seal header 350. The steam seal header 350 provides this collected steam to the low pressure seals 132 so that the low pressure seals 132 provide an effective seal for the low pressure steam turbine 130.
Excess steam which has been collected from the high pressure seals 112, 114 and the intermediate pressure seals 122 which is not required by the low pressure seals 132 is used to drive the low pressure steam turbine 130. However, in this embodiment steam is withdrawn from a first location within the low pressure steam turbine 130 itself, and this withdrawn steam is mixed with the steam in the steam seal header 350 collected from the high pressure seals 112, 114 and the intermediate pressure seals 122. This creates steam which is at a sufficiently low temperature and pressure that it can be effectively introduced into a second location within the low pressure steam turbine 130 to drive the low pressure steam turbine 130.
In some embodiments, the steam delivered from the steam seal header 350 into the low pressure steam turbine 130 would be delivered into the low pressure steam turbine 130 at a position downstream from the location where steam was withdrawn from the low pressure steam turbine 130. In alternate embodiments, however, steam delivered from the steam seal header 350 into the low pressure steam turbine 130 is delivered into the low pressure steam turbine 130 at a position upstream from the location where steam was withdrawn from the low pressure steam turbine 130.
An embodiment as illustrated in
As illustrated in
High pressure seals 412, 414 are provided to seal the high pressure steam turbine 410 to the rotating shaft 400. Likewise, intermediate pressure seals 422, 424 are provided to seal the intermediate pressure steam turbine 420 to the rotating shaft 400. Further, low pressure seals 432, 434 are provided to seal the low pressure steam turbine 430 to the rotating shaft 400.
As in the previously-described embodiments, in some operating conditions the dual-flow, low pressure steam turbine 430 cannot provide steam at a sufficiently high pressure to the low pressure seals 432, 434 to provide an effective seal. As a result, steam is collected from the high pressure seals 412, 414 and the intermediate pressure seals 422, 424 in a steam seal header 450. This steam is then provided to the low pressure seals 432, 434 as needed to provide an effective seal for the dual-flow, low pressure steam turbine 430.
In this embodiment, excess steam collected from the high pressure seals 412, 414 and the intermediate pressure seals 422, 424 is used to drive the dual-flow, low pressure steam turbine 430. As in the previously-described embodiment, a portion of the steam flowing through the low pressure steam turbine 430 is routed to the steam seal header 450. The steam drawn from first location(s) within the low pressure steam turbine 430 is mixed with the steam collected from the high pressure seals 412, 414 and the intermediate pressure seals 422, 424 to provide a flow of steam at an appropriate temperature and pressure that is routed back to second location(s) within the low pressure steam turbine 430.
The steam seal headers used in the steam turbine systems illustrated in
A steam seal header 550 as illustrated in
A second embodiment of a steam seal header 650 is illustrated in
The steam seal header 650 in
An aperture 662 is provided in the partition 660 so that at least a portion of the flow of steam received through the first inlet 652 can be communicated into the second chamber 680. A second inlet 656 opens into the second chamber 680. The second inlet 656 would be operatively connected to a low pressure steam turbine so that steam can be received from the low pressure steam turbine into the second chamber 680. A first outlet 658 also opens into the second chamber 680. The first outlet 658 is operatively connected to the low pressure steam turbine so that steam from within the second chamber 680 can be communicated to the low pressure steam turbine.
The second chamber 680 is used to create a mixture of the first flow of steam received through the first inlet 652 and the second flow of steam received through the second inlet 656. This mixture is then provided to the low pressure steam turbine through the first outlet 658.
The embodiment illustrated in
In some embodiments, the steam seal header 650 could also include a valve 664 connected to the aperture 662 to control the amount of steam that is routed into the second chamber 680. In some embodiments this valve 664 could be an expansion valve, which would cause the steam moving from the first chamber 670 into the second chamber 680 to enter the second chamber 680 at a lower pressure than exists within the first chamber 670.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
