JP2005155340A - Steam turbine plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steam turbine plant improving steam turbine plant thermal efficiency by using types of turbine extraction steam appropriately, when supplying turbine extraction steam from a steam turbine to a feedwater heater. <P>SOLUTION: This steam turbine plant is constituted, such that a turbine extraction steam pipe supplying turbine extraction steam from the steam turbine 12 to the feedwater heater 16 is divided into a high-pressure extraction steam pipe 19 positioned in an upstream side of the steam turbine 12 and a low-pressure extraction steam pipe 21 positioned in the downstream side of the steam turbine 12, and that the high-pressure extraction steam pipe 19 and the low-pressure extraction steam pipe 21 are used appropriately in accordance with operation types or the like. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a steam turbine plant, and more particularly, to a steam turbine plant that effectively supplies turbine bleed air extracted from an intermediate stage of the steam turbine to a feed water heater in accordance with an operating state.

  Conventionally, many steam turbine plants for business use incorporate a reheat cycle and a regeneration cycle that are developed from the Rankine cycle in order to increase the output and heat efficiency of the plant.

  Among these cycles, the regeneration cycle is a process in which steam that is being expanded by a steam turbine is extracted from an intermediate stage of the turbine, and the extracted turbine extracted air is supplied to a feed water heater, and the feed water heater is used to generate a steam generator such as a boiler. When the condensate / feed water to be refluxed is heated and steam is generated by a steam generator, fuel is reduced to improve plant thermal efficiency. As an example, there is a structure shown in FIG.

  The steam turbine plant includes a steam generator 1 such as a boiler, a steam turbine 2, a generator 3, a condenser 4, a feed water pump 6 incorporated in a condensate / feed water system 5, and a feed water heater 7. The steam generated from the steam is supplied to the steam turbine 2 where expansion work is performed, and the generator 3 is rotationally driven by power (rotational torque) generated at that time.

  Further, the steam turbine plant condenses the turbine exhaust that has finished the expansion work in the steam turbine 2 into the condensate, condenses the condensate, pressurizes and demineralizes the condensate into the condensate / feed water, Each of the high-pressure feed water heaters 7 is sequentially supplied. Here, the turbine bleed supplied from the middle stage of the steam turbine 2 through the turbine bleed pipe 9 to the feed water heater 7 is used as a heating source to restore the condensate / feed water system 5. The water / feed water is heated (regenerated), and the heated condensate / feed water is returned to the steam generator 1.

  The turbine bleed air heated by the high pressure feed water heater 7 from the condensate / feed water system 5 is supplied to the condenser 4 or the condensate / feed water system 5 through the drain pipe 8 as a drain. Reused as condensate / water supply.

  FIG. 6 shows the steam turbine 2 as one casing type for convenience of explanation, but actually, three casing types of a high pressure turbine casing, a medium pressure turbine casing, and a low pressure turbine casing are often used. In this case, the turbine exhaust that has finished the expansion work in the high-pressure turbine is returned to the steam generator 1 and reheated by the reheater incorporated therein. The reheat steam reheated by the reheater incorporates a so-called reheat cycle in which the reheat steam is supplied to the low pressure turbine via the intermediate pressure turbine.

  By the way, in the heat cycle in which the regeneration cycle and the reheat cycle are added to the Rankine cycle based on the above-described configuration, the heat transfer of the state quantity of the working steam is shown in a TH diagram (temperature / entropy diagram) as shown in FIG. It can be expressed as The TH line shown in FIG. 7 corresponds to the reference numeral in FIG.

  In the TH diagram shown in FIG. 7, the condensate / feed water supplied to the steam generator 1 at the point A is heated and evaporated here, and becomes superheated steam at the point B beyond the saturated steam line. The superheated steam performs expansion work in the steam turbine 2 and heat-drops (drops in temperature) through the saturated steam line at point C to the wet steam region at point D. The enthalpy at that time is p (kJ / kg ° K).

  The heat exhausted turbine exhaust is condensed to point E under isothermal change in the condenser 4 to become condensate / water supply. The enthalpy at that time is p (kJ / kg ° K).

  The condensate / water supply from the condenser 4 is boosted by the feed water pump 6 to a point F, further heated by the feed water heater 7 to a point b, and then returned to the steam generator 1. Become A.

  The theoretical steam turbine plant thermal efficiency (turbine cycle efficiency) at this time is represented by the ratio of the area BCDEFbA and the area BCCDpqEFbA.

  However, in the regeneration cycle, when the condensate / feed water flows through the feed water heater 7, it is heated using turbine bleed air from the steam turbine 2 as a heat source, so the area of the heat cycle becomes BCDabA. The enthalpy of condensate / water supply at point a is r (kJ / kg ° K).

  On the other hand, the thermal efficiency of the theoretical steam turbine plant incorporating the regeneration cycle is the ratio of the area BCDprabA and the area BCDabA. Can be improved.

Considering such a heat balance of the entire plant, for example, a technique for controlling extraction steam from a turbine while paying attention to water supply enthalpy is used for operation control of a nuclear reactor (see, for example, Patent Document 1).
JP 56-43598 A

  The TH diagram shown in FIG. 7 shows the heat transfer of the state quantity of the working fluid at the rated load (100% load) operation. In the partial load operation, the TH diagram is as shown in FIG. In addition, the heat transfer of the state quantity of the working fluid also changes. In FIG. 8, the solid line and the suffix “none” are those during rated load operation, and the broken line and the suffix “zero” are those during partial load operation.

  In general, a steam turbine plant adjusts a load by maintaining a constant steam temperature at the inlet of a steam turbine and controlling a steam flow rate during rated operation.

However, when the partial load operation is started, the flow rate of the turbine bleed supplied to the feed water heater from the middle stage of the steam turbine decreases. For this reason, the temperature of the condensate / feed water supplied to the steam generator becomes lower at the position of point A ₀ than at point A during rated operation, and the steam state quantity changes from point B ₀ to point C _0. Heat drop (temperature drop) to the wet steam region at point D ₀ through the saturated vapor line. The enthalpy at that time is p ₀ (kJ / kg ° K).

  The turbine exhaust, which has been subjected to heat drop and finished the expansion work, is condensed in the condenser to become condensate / water supply. Then, the condensate / feed water is boosted by the feed water pump, heated by the feed water heater, and returned to the steam generator.

The heat-dropped turbine exhaust heat-transfers to the point A ₀ when returning to the steam generator through the positions of the points a ₀ and b ₀ . The enthalpy at the point a ₀ is r ₀ (kJ / kg ° K).

The partial load thermal efficiency at this time is a ratio of the area B ₀ C ₀ D ₀ p ₀ r ₀ a ₀ b ₀ A ₀ to the area B ₀ C ₀ D ₀ a ₀ b ₀ A ₀ , and is a steam turbine compared to the rated operation. Plant thermal efficiency becomes poor.

  Thus, in a steam turbine plant, it is known that the thermal efficiency of the steam turbine plant deteriorates during partial load operation, but improving the steam turbine plant thermal efficiency even during partial load operation is also from the viewpoint of saving fuel. It is important.

  If only the steam turbine plant thermal efficiency at the time of partial load operation is to be improved, the steam turbine plant can further increase the steam temperature by setting the turbine bleed port closer to the steam turbine inlet side. It is considered that the temperature of the condensate / feed water passing through the feed water heater can also be increased.

  However, the appropriate position of the turbine bleed port varies depending on the increase or decrease of the turbine load (output). When the turbine load is changed from the partial load operation to the rated load operation, the turbine bleed air supplied to the feed water heater is used. There is a problem that expansion work cannot be performed by an amount, and the thermal efficiency of the steam turbine plant is lowered.

  In addition, if the turbine bleed port is set near the inlet side of the steam turbine, the turbine bleed temperature will be too high and the condensate / feed water supplied to the steam generator will be at the design temperature when the partial load operation is switched to the rated operation. It becomes a factor of accident occurrence of steam generators.

  The present invention is intended to improve the thermal efficiency of the steam turbine plant at the time of partial load in view of such circumstances, and a plurality of turbine bleed ports are set in the steam turbine, and the turbine bleed ports are selectively used according to the operation state and the like. An object of the present invention is to provide a steam turbine plant that further improves the thermal efficiency of the steam turbine plant during partial load operation while allowing the steam turbine plant to stably operate during rated operation.

  In order to achieve the above-mentioned object, a steam turbine plant according to the present invention has a turbine bleed pipe for supplying turbine bleed gas from a steam turbine to a feed water heater on the upstream side of the steam turbine. The high-pressure bleed pipe is divided into a low-pressure bleed pipe located downstream of the high-pressure bleed pipe and the high-pressure bleed pipe and the low-pressure bleed pipe according to either the type of operation or the state quantity of the working fluid. It is configured to use properly.

  In order to achieve the above object, the steam turbine plant according to the present invention includes a high pressure bleed pipe having a high pressure bleed valve, and a partial load operation. And a bleed valve opening / closing control device for giving a valve opening command.

  In order to achieve the above-mentioned object, the steam turbine plant according to the present invention includes a low-pressure bleed pipe having a low-pressure bleed valve as described in claim 3, and the low-pressure bleed valve is connected to the low-pressure bleed valve during rated operation. A bleed valve opening / closing control device for giving a valve opening command is provided.

  In order to achieve the above-mentioned object, the steam turbine plant according to the present invention includes a high-pressure bleed pipe having a high-pressure bleed valve and a main steam generated from the steam generator. When the pressure is lower than a predetermined pressure, a bleed valve opening / closing control device is provided that gives a valve opening command to the high pressure bleed valve based on the main steam pressure signal.

  In order to achieve the above object, the steam turbine plant according to the present invention includes a low pressure bleed pipe having a low pressure bleed valve and a main steam generated from the steam generator. When the pressure is higher than a predetermined pressure, a bleed valve opening / closing control device is provided that gives a valve opening command to the low pressure bleed valve based on the main steam pressure signal.

  In order to achieve the above-mentioned object, the steam turbine plant according to the present invention includes a high-pressure bleed pipe having a high-pressure bleed valve and a predetermined electrical output from the generator. When the electric output is lower than the output, a bleed valve opening / closing control device is provided that gives a valve opening command to the high pressure bleed valve based on the electric output signal.

  In order to achieve the above object, the steam turbine plant according to the present invention includes a low pressure bleed pipe having a low pressure bleed valve and a predetermined electrical output from the generator. When the output is higher than the output, the extraction valve opening / closing control device is provided that gives a valve opening command to the low pressure extraction valve based on the electric output signal.

  In order to achieve the above object, the steam turbine plant according to the present invention includes a high-pressure extraction pipe having a high-pressure extraction valve and a condensate on the inlet side of the steam generator. A bleed valve opening / closing control device that gives a valve opening command to the high pressure bleed valve based on the condensate / feed water temperature signal when the feed water is lower than a predetermined temperature.

  In order to achieve the above-mentioned object, the steam turbine plant according to the present invention includes a low-pressure bleed pipe and a condensate on the inlet side of the steam generator. A bleed valve opening / closing control device that provides a valve opening command to the low pressure bleed valve based on the condensate / feed water temperature signal when the feed water is higher than a predetermined temperature.

  The steam turbine plant according to the present invention divides an extraction port for supplying turbine extraction from an intermediate stage of a steam turbine to a feed water heater into a high-pressure side and a low-pressure side, and the divided high-pressure system and low-pressure system Each with a bleed valve that opens the low pressure side bleed valve during rated operation and also opens the high pressure side bleed valve during partial load operation. Therefore, it is possible to supply high-temperature turbine bleed gas from the steam turbine to the feed water heater even during partial load operation, which reduces the fuel consumption of the steam generator. The turbine plant thermal efficiency can be improved.

  Hereinafter, an embodiment of a steam turbine plant according to the present invention will be described with reference to the drawings and reference numerals attached to the drawings.

  FIG. 1 is a conceptual diagram showing a first embodiment of a steam turbine plant according to the present invention.

  The steam turbine plant according to the present embodiment includes a steam generator 10, a steam turbine 12 having a generator 11 directly connected to a shaft, a condenser 13, a condensate / feed water system 14, a feed water pump 15, a feed water heater 16, and a drain pipe. 17, the steam generated from the steam generator 10 is expanded by the steam turbine 12, and the generator 11 is driven by the power generated at that time, while the turbine exhaust that has finished the expansion work by the steam turbine 12 is recovered. The water is condensed in the water device 13 to be condensed water / feed water, and the condensate / water supply is boosted by the feed water pump 15 of the condensate / water feed system 14 and further heated (regenerated) by the feed water heater 16 to the steam generator 10. A closed loop is constructed. In addition, the drain produced | generated with the feed water heater 16 is returned to the condenser 13 via the drain pipe 17, and is utilized again as condensate and water supply.

  Further, the steam turbine plant according to the present embodiment includes a high pressure bleed pipe 19 connected to a high pressure bleed port 18 provided at a position close to the inlet side of the steam turbine 12 and a low pressure bleed port provided on the downstream side of the high pressure bleed port 18. A low pressure bleed pipe 21 connected to 20 is provided, and a valve opening / closing signal is given to each of the high pressure bleed valve 22 and the low pressure bleed valve 23 interposed in an intermediate portion connecting each of the bleed pipes 19, 20 and the feed water heater 16. A bleed valve opening / closing control device 24 is provided.

  Next, the operation will be described.

  During rated operation, the feed water heater 16 does not require high temperature and high pressure by turbine extraction as a heating source, so the steam turbine plant closes the high pressure extraction valve 22 of the high pressure extraction pipe 19 and the low pressure extraction pipe 21. The low-pressure bleed valve 23 is opened, and the turbine bleed air is supplied from the low-pressure bleed port 20 of the steam turbine 12 to the feed water heater 16 through the low-pressure bleed pipe 21.

  The state quantity of the working fluid at this time is thermally transferred along the thermal cycle of point B → point C → point D → point a → point b → point A as shown by the solid line in FIG.

When there is a partial load operation command from the rated operation in this state, the state quantity of the conventional working fluid is, as shown by the broken line, point B ₁ → point C ₁ → point D ₁ → point a ₁ → point b ₁ → to heat transfer along the heat cycle at point a _1. For this reason, in the partial load operation, the thermal efficiency of the steam turbine plant was significantly reduced.

  However, in the present embodiment, as shown in FIG. 1, a high pressure bleed valve 22 is provided in a high pressure bleed pipe 19 connected to the high pressure bleed port 18 of the steam turbine 12, and a low pressure connected to the low pressure bleed port 20 of the steam turbine 12. A low pressure bleed valve 23 is provided in the bleed pipe 21, and when a partial load operation command is input to the bleed valve opening / closing control device 24, a valve closing signal is given from the bleed valve opening / closing control device 24 to the low pressure bleed valve 23 to open the high pressure bleed valve 22. Since the valve signal is given, high-temperature and high-pressure turbine bleed air can be supplied from the steam turbine 12 by the feed water heater 16 as a heating source.

As a result, in the steam turbine plant, the state quantity of the working fluid is represented by the heat of point B ₂ → point C ₂ → point D ₂ → point a ₂ → point b ₂ → point A ₂ , as indicated by the one-dot chain line in FIG. Since heat is transferred along the cycle, the heat efficiency of the steam turbine plant can be improved by the amount of heat transferred.

  FIG. 2 is a conceptual diagram showing a second embodiment of the steam turbine plant according to the present invention.

  The steam turbine plant according to the present embodiment is provided with a pressure transmitter 25 on the outlet side of the steam generator 10, and supplies the main steam pressure detected by the pressure transmitter 25 to the extraction valve opening / closing control device 24. When the generated main steam pressure signal is higher than a predetermined pressure signal (at rated operation), an open signal is given to the low pressure bleed valve 23 of the low pressure bleed pipe 21 and the high pressure bleed valve 22 of the high pressure bleed pipe 19 is closed. When a main steam pressure signal is lower than a predetermined pressure signal (partial load operation), a valve closing signal is given to the low pressure bleed valve 23 of the low pressure bleed pipe 21, and a high pressure of the high pressure bleed pipe 19 is given. The valve opening signal is given to the bleed valve 22.

  Thus, this embodiment provides the pressure transmitter 25 on the outlet side of the steam generator 10, and when the main steam pressure detected by the pressure transmitter 25 is higher than the predetermined pressure, the extraction valve opening / closing control device When the main steam pressure detected by the pressure transmitter 25 is lower than a predetermined pressure while an open signal is supplied from the valve 24 to the low pressure bleed valve 23 and a close signal is supplied to the high pressure bleed valve 22, the bleed valve opening / closing control is performed. Since the device 24 is configured to provide a valve closing signal to the low pressure bleed valve 23 and a valve open signal to the high pressure bleed valve 22, the temperature of the condensate / feed water is increased by raising the temperature of the turbine bleed during partial load operation. The steam turbine plant thermal efficiency can be improved.

  FIG. 3 is a conceptual diagram showing a third embodiment of the steam turbine plant according to the present invention.

  The steam turbine plant according to the present embodiment is provided with an electrical output meter 26 on the outlet side of the generator 11, and provides an electrical output (load) detected by the electrical output meter 26 to the extraction valve opening / closing control device 24. When the generated electrical output signal is higher than the predetermined electrical output signal (during rated operation), a valve opening signal is given to the low pressure bleed valve 23 of the low pressure bleed pipe 21 and the high pressure bleed valve 22 of the high pressure bleed pipe 19 is closed. When a valve signal is given and the electrical output signal is lower than a predetermined electrical output (partial load operation), a valve closing signal is given to the low-pressure bleed valve 23 of the low-pressure bleed pipe 21 and high-pressure bleed of the high-pressure bleed pipe 19 The valve 22 is configured to give a valve opening signal.

  Thus, in the present embodiment, the electrical output meter 26 is provided on the outlet side of the generator 11, and when the electrical output detected by the electrical output meter 26 is higher than the predetermined pressure, the extraction valve opening / closing control device 24 When an open signal is given to the low pressure bleed valve 23 and a close signal is given to the high pressure bleed valve 22, while the electrical output detected by the electrical output meter 26 is lower than a predetermined electrical output, the bleed valve opening / closing control device 24 Since the valve closing signal is given to the low pressure bleed valve 23 and the valve open signal is given to the high pressure bleed valve 22, the temperature of the turbine bleed is raised and the temperature of the condensate / feed water is raised during partial load operation. Thus, the thermal efficiency of the steam turbine plant can be improved.

  FIG. 4 is a conceptual diagram showing a fourth embodiment of the steam turbine plant according to the present invention.

  The steam turbine plant according to the present embodiment is provided with a temperature detector 27 on the inlet side of the steam generator 10, and gives the temperature of the main steam detected by the temperature detector 27 to the extraction valve opening / closing control device 24. When the generated main steam pressure signal is higher than a predetermined pressure signal (at rated operation), an open signal is given to the low pressure bleed valve 23 of the low pressure bleed pipe 21 and the high pressure bleed valve 22 of the high pressure bleed pipe 19 is closed. When a main steam temperature signal is lower than a predetermined temperature signal (partial load operation), a valve closing signal is given to the low pressure bleed valve 23 of the low pressure bleed pipe 21 and a high pressure of the high pressure bleed pipe 19 is provided. The valve opening signal is given to the bleed valve 22.

  As described above, in this embodiment, the temperature detector 27 is provided on the inlet side of the steam generator 10, and when the main steam temperature detected by the temperature detector 27 is higher than the predetermined temperature, the extraction valve opening / closing control device. When the main steam temperature detected by the temperature detector 27 is lower than a predetermined temperature while a valve opening signal is supplied from 24 to the low pressure bleed valve 23 and a close signal is supplied to the high pressure bleed valve 22, the bleed valve opening / closing control is performed. Since the device 24 is configured to provide a valve closing signal to the low pressure bleed valve 23 and a valve open signal to the high pressure bleed valve 22, the temperature of the condensate / feed water is increased by raising the temperature of the turbine bleed during partial load operation. The steam turbine plant thermal efficiency can be improved.

The conceptual diagram which shows 1st Embodiment of the steam turbine plant which concerns on this invention. The conceptual diagram which shows 2nd Embodiment of the steam turbine plant which concerns on this invention. The conceptual diagram which shows 3rd Embodiment of the steam turbine plant which concerns on this invention. The conceptual diagram which shows 4th Embodiment of the steam turbine plant which concerns on this invention. The TH diagram which compared the state quantity thermal cycle of the working fluid in the steam turbine plant which concerns on this invention, and the thermal cycle of the conventional working fluid. The conceptual diagram which shows the conventional steam turbine plant. The TH diagram which shows the thermal cycle of the working fluid in the conventional steam turbine plant. The TH diagram which compared the heat cycle of the working fluid at the time of rated operation in the steam turbine plant concerning the present invention, and the heat cycle of the working fluid at the time of partial load operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steam generator 2 Steam turbine 3 Generator 4 Condenser 5 Condensate and feed water system 6 Feed water pump 7 Feed water heater 8 Drain pipe 9 Turbine extraction pipe 10 Steam generator 11 Generator 12 Steam turbine 13 Condenser 14 Recovery Water / water supply system 15 Water supply pump 16 Water supply heater 17 Drain pipe 18 High pressure extraction port 19 High pressure extraction pipe 20 Low pressure extraction port 21 Low pressure extraction pipe 22 High pressure extraction valve 23 Low pressure extraction valve 24 Extraction valve opening / closing control device 25 Pressure transmitter 26 Electricity Output meter 27 Temperature detector

Claims (9)

The turbine bleed pipe for supplying turbine bleed from the steam turbine to the feed water heater is divided into a high pressure bleed pipe located upstream of the steam turbine and a low pressure bleed pipe located downstream thereof, and the high pressure bleed pipe and the A steam turbine plant characterized in that the low-pressure extraction pipe is configured to be used in accordance with either the type of operation or the state quantity of the working fluid. 2. The steam turbine plant according to claim 1, wherein the high pressure bleed pipe includes a high pressure bleed valve and a bleed valve opening / closing control device for giving a valve opening command to the high pressure bleed valve during partial load operation. The steam turbine plant according to claim 1, wherein the low-pressure bleed pipe includes a low-pressure bleed valve and a bleed valve opening / closing control device for giving a valve opening command during rated operation to the low-pressure bleed valve. The high pressure bleed pipe is provided with a high pressure bleed valve, and when the main steam generated from the steam generator is lower than a predetermined pressure, the bleed air giving a valve opening command to the high pressure bleed valve based on the main steam pressure signal The steam turbine plant according to claim 1, further comprising a valve opening / closing control device. The low pressure bleed pipe is provided with a low pressure bleed valve, and when the main steam generated from the steam generator is higher than a predetermined pressure, the bleed air for giving a valve opening command to the low pressure bleed valve based on the main steam pressure signal The steam turbine plant according to claim 1, further comprising a valve opening / closing control device. The high pressure bleed pipe is provided with a high pressure bleed valve, and when the electrical output from the generator is lower than a predetermined electrical output, the bleed valve opening / closing which gives a valve opening command to the high pressure bleed valve based on the electrical output signal The steam turbine plant according to claim 1, further comprising a control device. The low pressure bleed pipe has a low pressure bleed valve, and when the electrical output from the generator is higher than a predetermined electrical output, opens and closes the bleed valve that gives a valve opening command to the low pressure bleed valve based on the electrical output signal The steam turbine plant according to claim 1, further comprising a control device. The high pressure bleed pipe is provided with a high pressure bleed valve, and opens to the high pressure bleed valve based on the condensate / feed water temperature signal when the condensate / feed water on the inlet side of the steam generator is lower than a predetermined temperature. The steam turbine plant according to claim 1, further comprising a bleed valve opening / closing control device for giving a valve command. The low pressure bleed pipe has a low pressure bleed valve, and when the condensate / feed water on the inlet side of the steam generator is higher than a predetermined temperature, the low pressure bleed pipe opens to the low pressure bleed valve based on the condensate / feed water temperature signal. The steam turbine plant according to claim 1, further comprising a bleed valve opening / closing control device for giving a valve command.

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