Steam turbine plant and method for improving same

A steam turbine plant, comprising:

• a steam turbine configured to be driven by steam supplied from a steam generation source;
• a condenser configured to condense steam discharged from the steam turbine and convert the steam into water;
• and
• a gas extraction system including a gas extractor configured to extract noncondensable gas in the condenser and connected to the condenser, wherein
• the steam turbine includes
• a turbine rotor that includes a first shaft portion and a second shaft portion on one side in an axial direction and the other side in the axial direction, respectively and is rotationally driven by the steam supplied from the steam generation source,
• a casing that accommodates the turbine rotor with the first shaft portion and the second shaft portion penetrating, and
• a first gland seal provided in a first gap between the first shaft portion and the casing and a second gland seal provided in a second gap between the second shaft portion and the casing,
• only a first discharge system for discharging a gas flowing into the first gland seal is connected to the first gland seal,
• only a second discharge system for discharging a gas flowing into the second gland seal is connected to the second gland seal,
• the first discharge system is connected to the gas extraction system so as to guide the gas flowing into the first gland seal to the gas extractor without passing through the condenser,
• the second discharge system is connected to the gas extraction system so as to guide the gas flowing into the second gland seal to the gas extractor without passing through the condenser,
• the steam turbine is made up of a single-flow exhaust turbine in which steam supplied from the steam generation source flows from one side in the axial direction to the other side in the axial direction of the turbine rotor without being divided and is discharged from one direction,
• the first gland seal includes a first seal portion, a second seal portion, and a third seal portion disposed in this order at intervals from an outer side toward an inner side of the steam turbine,
• the first gland seal includes a first chamber that is sectioned by the first seal portion and the second seal portion and is pressure-regulatable and a second chamber that is sectioned by the second seal portion and the third seal portion and is pressure-regulatable,
• the first discharge system is made up of a first line having one side in the axial direction connected to the first chamber and the other side in the axial direction connected to the gas extraction system and a second line having one side in the axial direction connected to the second chamber and the other side in the axial direction connected to the gas extraction system,
• the second line includes a main line connected to the second chamber and the gas extraction system and a diverging line diverging from the main line and connected to a halfway position between the one side in the axial direction and the other side in the axial direction of the steam turbine,
• a first on-off valve is provided on the main line of the second line and between a diverging point with the diverging line and a connection point with the gas extraction system, and
• a second on-off valve is provided on the diverging line of the second line.

A method for improving a steam turbine plant,

• the steam turbine plant including
• a steam turbine including a turbine rotor rotationally driven by steam supplied from a steam generation source, a casing that accommodates the turbine rotor with a first shaft portion on one side in an axial direction and a second shaft portion on the other side in the axial direction of the turbine rotor penetrating, a first gland seal provided in a first gap between the first shaft portion and the casing, and a second gland seal provided in a second gap between the second shaft portion and the casing,
• a condenser configured to condense steam discharged from the steam turbine and convert the steam into water,
• a gas extraction system including a gas extractor configured to extract noncondensable gas in the condenser and connected to the condenser,
• a gland steam supply system connected to the first gland seal and the second gland seal and configured to supply gland steam to the first gland seal and the second gland seal, and
• a discharge system having one side in the axial direction connected to the first gland seal and the second gland seal and configured to guide and discharge a gas flowing into the first gland seal and the second gland seal to an outside,
• the method comprising:
• abolishing the gland steam supply system;
• and
• making a modification of connecting the other side in the axial direction of the discharge system to the gas extraction system such that a gas flowing into the first gland seal and the second gland seal is guided to the gas extractor without passing through the condenser, wherein
• the steam turbine is made up of a single-flow exhaust turbine in which steam supplied from the steam generation source flows from one side in the axial direction to the other side in the axial direction of the turbine rotor without being divided and is discharged from one direction,
• the first gland seal and the second gland seal each include a first seal portion, a second seal portion, and a third seal portion disposed in this order at intervals from an outer side toward an inner side of the steam turbine and include a first chamber sectioned by the first seal portion and the second seal portion and a second chamber sectioned by the second seal portion and the third seal portion, and
• for a configuration in which the discharge system includes a first discharge system made up of only a discharge line connected to the first chamber of the first gland seal and a second discharge system made up of only a discharge line connected to the first chamber of the second gland seal,
• the first discharge system is modified to be made up of a first line having one side in the axial direction connected to the first chamber of the first gland seal and the other side in the axial direction connected to the gas extraction system and a second line having one side in the axial direction connected to the second chamber of the first gland seal and the other side in the axial direction connected to the gas extraction system,
• the second line is configured to include a main line connecting the second chamber of the first gland seal and the gas extraction system and a diverging line diverging from the main line and connected to a halfway position between the one side in the axial direction and the other side in the axial direction of the steam turbine,
• a first on-off valve is provided on the main line of the second line between a diverging point with the diverging line and a connection point with the gas extraction system, and
• a second on-off valve is provided on the diverging line of the second line.