A feed water pump drive system for a secondary reheat unit

Abstract

The present invention relates to a feed water pump drive system for a secondary reheat unit. One end of a regenerative steam turbine of this system is connected to a balance generator, and the other end is connected to a feed water pump speed regulating device, serving as the main driving force for the feed water pump; an auxiliary driving steam turbine for the feed water pump serves as a superimposed driving force. One end is connected to the feed water pump speed regulating device, and the other end is connected to the fore pump of the feed water pump; one end of the auxiliary driving steam turbine for the feed water pump is connected to the feed water pump speed regulating device through a 3S clutch, and the other end is connected to the fore pump of the feed water pump, and is automatically engaged with the feed water pump speed regulating device through the 3S clutch, and is used to provide a superimposed driving force for the feed water pump when the unit is at high load and drive the fore pump to operate when the unit is at low load. The present invention can improve the operating efficiency of the feed water pump group under the wide load operating conditions of the unit and improve the operating economy of the secondary reheat dual-machine regenerative system.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam turbine power generation equipment, and particularly relates to a feed water pump drive system for a secondary reheat unit. Background Art

[0002] With the continuous improvement of the main steam parameters and reheat steam parameters of steam turbine units, the problem of energy level mismatch caused by excessive superheat of the extraction steam parameters in the regenerative system has become increasingly serious, which to a certain extent reduces the benefits brought by improving the steam turbine parameters. To alleviate this problem, a conventional improvement method is to add a pre - type steam cooler before the inlet of the heater to reduce the superheat of the regenerative extraction steam. However, with the further increase of the main steam parameters, the investment in materials and equipment of the external steam cooler increases, and the technical and economic indicators of this method decline. Another improvement method is to add a heat - regenerative extraction steam - driven feed water pump steam turbine, which is an extraction - backpressure steam turbine. While driving the feed water pump, it can significantly reduce the superheat of the steam supply of the high - pressure heater system. At the same time, a balance generator can be added to consume the excess driving force and meet part of the plant electricity or other electricity demands.

[0003] As a steam - driven feed water pump for operation function, the selection of the number and capacity of its equipment depends on various factors such as unit capacity, equipment reliability, the role of the unit in the power grid, and equipment investment. For units with a capacity of 1000MW and above, European power plants mainly adopt the configuration mode of 1×100% capacity steam - driven feed water pumps. In Japan and in the early stage of our country, the configuration mode of 2×50% capacity steam - driven feed water pumps was mainly adopted. However, after 2012, with the improvement of equipment manufacturing level, the equipment reliability has reached or even exceeded the level of the main unit, and more and more power plants have begun to adopt the 1×100% capacity steam - driven feed water pump scheme.

[0004] With the large - scale commissioning of thermal power units in recent years, and the growth rate of power demand being much lower than expected, the power supply - demand balance has gradually shifted from surplus to excess. Units with a capacity of 1000MW level are also gradually facing the pressure of participating in peak shaving. In the future for some time, the units may face the situation of not being able to operate at full load for a long time. This poses new requirements for the determination of the 1×100% capacity steam - driven feed water pump configuration scheme. The existing 1×100% capacity steam - driven feed water pump and the supporting small steam turbine can be adjusted within the load range of 30% - 100%, but the economy becomes poor during partial load and low - load operation. Summary of the Invention

[0005] Aiming at the unit configured with a 1×100% capacity steam - driven feed water pump, the object of the present invention is to propose a double - machine regenerative system for a secondary reheat unit that can not only operate efficiently at partial loads but also meet the full - load operation of the unit. It improves the operation efficiency of the feed water pump group under wide - load operation conditions of the unit and improves the operation economy of the double - machine regenerative system.

[0006] The present invention provides a feed water pump drive system for a secondary reheat unit, which includes a steam turbine, a boiler, a balance generator, a regenerative steam turbine, a feed water pump speed regulating device, a 3S clutch, a feed water pump, an auxiliary drive steam turbine for the feed water pump, a booster pump, a deaerator, a high-pressure heater, and a low-pressure heater;

[0007] One end of the regenerative steam turbine is connected to the balance generator, and the other end is connected to the feed water pump speed regulating device, serving as the main driving force for the feed water pump; the auxiliary drive steam turbine for the feed water pump serves as a superimposed driving force, with one end connected to the feed water pump speed regulating device and the other end connected to the booster pump of the feed water pump;

[0008] One end of the auxiliary drive steam turbine for the feed water pump is connected to the feed water pump speed regulating device through the 3S clutch, and the other end is connected to the booster pump of the feed water pump. It automatically engages with the feed water pump speed regulating device through the 3S clutch, and is used to provide a superimposed driving force for the feed water pump when the unit is at high load and drive the booster pump to operate when the unit is at low load.

[0009] Further, the operating mode of the regenerative steam turbine is constant speed operation at 3000 r / min, and the operating mode of the auxiliary drive steam turbine for the feed water pump is variable speed operation; the rated output of the regenerative steam turbine can approximately meet 80% of the total power of the feed water pump. When the unit is at high load, the remaining driving force requirement of the feed water pump is met by the auxiliary drive steam turbine for the feed water pump.

[0010] Further, the feed water pump speed regulating device includes an input shaft, a superimposed gear, and an output shaft. The regenerative steam turbine is connected to the input shaft, the auxiliary drive steam turbine for the feed water pump is connected to the superimposed gear through the 3S clutch, and the output shaft is connected to the feed water pump, and is used to deliver the superimposed output of the regenerative steam turbine and the auxiliary drive steam turbine for the feed water pump to the feed water pump.

[0011] Further, the set value of the meshing speed of the 3S clutch is set according to specific unit parameters. When the output of the feed water pump is below 80%, the auxiliary drive steam turbine for the feed water pump is not connected to the superimposed gear and is only used to drive the booster pump to operate; when the output requirement of the feed water pump is greater than 80%, the auxiliary drive steam turbine for the feed water pump is connected to the superimposed gear to increase the output of the feed water pump.

[0012] Furthermore, the steam inlet of the regenerative extraction steam turbine is provided by the cold section steam exhausted from the ultra-high pressure cylinder of the steam turbine; the regenerative extraction steam turbine is provided with a number of extraction holes for supplying steam to the high-pressure heaters at corresponding energy levels respectively; after the exhaust steam of the regenerative extraction steam turbine is combined with another extraction steam of the main unit of the unit, it is respectively supplied to the auxiliary drive steam turbine of the feed water pump and the deaerator for use; after the exhaust steam of the auxiliary drive steam turbine of the feed water pump is combined with the extraction steam of the main unit of the unit, it enters the low-pressure heater at the corresponding energy level.

[0013] Furthermore, the regenerative extraction steam turbine and the auxiliary drive steam turbine of the feed water pump are not provided with a condenser, and their exhaust steam is used to continue to supply the heaters.

[0014] By means of the above solution, the feed water pump drive system of the secondary reheat unit has the following technical effects:

[0015] (1) This system can reduce the design output of the steam turbine supporting the feed water pump by 1×100%, and improve the operating efficiency of the feed water pump steam turbine unit under partial load. At the same time, the equipment investment cost of the feed water pump steam turbine can be reduced.

[0016] (2) The output speed regulating device of the feed water pump adopts the planetary gear speed regulating method, and compared with the hydraulic coupling speed regulating method, the speed regulating efficiency under the whole operating condition is improved.

[0017] (3) The method of using the auxiliary steam turbine to drive the booster pump can make more full use of the energy of the exhaust steam from the intermediate pressure cylinder and the exhaust steam of the regenerative feed water pump steam turbine, and deepen the cascade utilization of energy. Another function of the auxiliary steam turbine is to drive the feed water pump together with the regenerative extraction steam turbine under high load to ensure the safe and stable operation of the unit under high load conditions.

[0018] (4) The use of the 3S clutch in the present invention can make the adjustment of the operating output of the feed water pump smoother, and automatically realize the drive superposition of the auxiliary steam turbine according to the speed setting of the 3S clutch.

[0019] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following takes the preferred embodiment of the present invention and combines with the attached drawings to describe in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of a feed water pump drive system of a secondary reheat unit of the present invention.

[0021] Reference numerals in the figure:

[0022] 1 - Steam turbine; 2 - Boiler; 3 - Balancing generator; 4 - Regenerative small steam turbine; 5 - Feed pump speed control device; 6 - 3S clutch; 7 - Feed pump; 8 - Feed pump auxiliary drive steam turbine; 9 - Booster pump; 10 - Deaerator; 11 - High-pressure heater; 12 - Low-pressure heater; 13 - First regulating valve; 14 - Second regulating valve; 15 - Third regulating valve; 16 - Fourth regulating valve. Specific embodiments

[0023] The following combines the accompanying drawings and embodiments to further describe in detail the specific embodiments of the present invention. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0024] Refer Figure 1 As shown, this embodiment provides a feed pump drive system for a secondary reheat unit, including a steam turbine 1, a boiler 2, a balancing generator 3, a regenerative small steam turbine 4, a feed pump speed control device 5, a 3S clutch 6, a feed pump 7, a feed pump auxiliary drive steam turbine 8, a booster pump 9, a deaerator 10, a high-pressure heater 11, a low-pressure heater 12, and equipment such as pipelines and valves. One end of the regenerative small steam turbine 4 is connected to the balancing generator 3, and the other end is connected to the feed pump speed control device 5, serving as the main driving force (about 80%) of the feed pump 7. One end of the feed pump auxiliary drive steam turbine 8, as the superimposed driving force (about 20%), is connected to the feed pump speed control device 5, and the other end is connected to the booster pump 9 of the feed pump 7. This system can reduce the designed rated power of the regenerative small steam turbine 4, which is beneficial to improving the operating efficiency of the regenerative small steam turbine 4 under partial load of the unit. The feed pump auxiliary drive steam turbine 8 can be automatically engaged with the feed pump speed control device 5 through the 3S clutch 6 to provide a superimposed driving force for the feed pump 7 when the unit is at high load and drive the booster pump 9 at low load.

[0025] Specifically, the steam turbine unit is a secondary reheat unit, including 1 ultra-high pressure cylinder, 1 high pressure cylinder, 1 double-flow medium pressure cylinder, and 2 double-flow low pressure cylinders. The exhaust steam from the ultra-high pressure cylinder enters the boiler 2 for primary reheat, the steam at the outlet of the primary reheater enters the high pressure cylinder, the exhaust steam from the high pressure cylinder enters the boiler 2 for secondary reheat, and the secondary reheat steam enters the medium pressure cylinder of the steam turbine to continue doing work. The exhaust steam from the medium pressure cylinder enters the double-flow low pressure cylinders.

[0026] The regenerative small steam turbine 4 operates at a constant speed of 3000 r / min, and the auxiliary drive steam turbine operates at a variable speed. The rated output of the regenerative small steam turbine 4 can approximately meet 80% of the total power of the feed pump 7. When the unit is at high load, the remaining driving force requirement of the feed pump 7 is provided by the feed pump auxiliary drive steam turbine 8.

[0027] One end of the auxiliary drive steam turbine 8 of the feed water pump is connected to the speed regulating device 5 of the feed water pump through the 3S clutch 6, and the other end is connected to the fore pump 9 of the feed water pump 7. When the unit operates at partial load (about below 80% of the rated load), the rotational speed of the auxiliary drive steam turbine 8 of the feed water pump is not sufficient to engage the 3S clutch 6, and the auxiliary drive steam turbine 8 of the feed water pump only drives the fore pump 9 to operate. When at high load (about greater than 80% of the rated load), the power of the auxiliary drive steam turbine 8 of the feed water pump increases, the rotational speed rises, the 3S clutch 6 engages, and the auxiliary drive steam turbine 8 of the feed water pump and the regenerative steam turbine 4 jointly drive the feed water pump 7.

[0028] The speed regulating device 5 of the feed water pump mainly consists of an input shaft, a superimposed gear, and an output shaft, etc. The regenerative steam turbine 4 is connected to the input shaft, the auxiliary drive steam turbine 8 of the feed water pump is connected to the superimposed gear through the 3S clutch 6, and the output shaft is connected to the feed water pump 7, and the combined output of the regenerative steam turbine 4 and the auxiliary drive steam turbine 8 of the feed water pump is transmitted to the feed water pump 7.

[0029] The steam inlet of the regenerative steam turbine 4 is provided by the cold section steam discharged from the ultra-high pressure cylinder of the steam turbine. The regenerative steam turbine 4 is provided with several steam extraction holes, which respectively supply steam to the high-pressure heaters 11 at the corresponding energy levels. After the exhaust steam of the regenerative steam turbine 4 converges with another extraction steam of the main unit, it is respectively supplied to the auxiliary drive steam turbine 8 of the feed water pump and the deaerator 10 for use. The exhaust steam of the auxiliary drive steam turbine 8 of the feed water pump converges with the extraction steam of the main unit and then enters the low-pressure heater 12 at the corresponding energy level.

[0030] A first regulating valve 13 is provided between the exhaust steam of the regenerative steam turbine 4 and the inlet of the auxiliary drive steam turbine 8 of the feed water pump. A second regulating valve 14 is provided on the main unit extraction steam pipeline supplying the auxiliary drive steam turbine 8 of the feed water pump. A third regulating valve 15 is provided on the inlet pipeline of the deaerator 10. During actual operation, the first regulating valve 13, the second regulating valve 14, and the third regulating valve 15 are adjusted according to the main unit load and the demand of the deaerator 10 to ensure the steam consumption of the deaerator 10 and the output demand of the feed water pump 7. A fourth regulating valve 16 is provided on the exhaust pipeline of the auxiliary drive steam turbine 8 of the feed water pump.

[0031] The set value of the engagement rotational speed of the 3S clutch 6 should be set according to the specific unit parameters. In principle, when the output of the feed water pump 7 is below 80%, the auxiliary drive steam turbine 8 of the feed water pump is not connected to the superimposed gear and only drives the fore pump 9 to operate. When the output demand of the feed water pump 7 is greater than 80%, the steam inlet volume of the auxiliary drive steam turbine 8 of the feed water pump increases, the rotational speed rises to reach the engagement rotational speed of the 3S clutch 6, its steam inlet end is connected to the speed regulating device 5 of the feed water pump, drives the superimposed gear, and thus increases the output of the feed water pump 7.

[0032] Specifically, five regenerative heaters are provided in the high-pressure section, and the pressure parameters are, from high to low, No. 1 high-pressure heater, No. 2 high-pressure heater, No. 3 high-pressure heater, No. 4 high-pressure heater, and No. 5 high-pressure heater. Four regenerative heaters are provided in the low-pressure section, and the pressure parameters are, from high to low, No. 1 low-pressure heater, No. 2 low-pressure heater, No. 3 low-pressure heater, and No. 4 low-pressure heater. The extraction steam of No. 1 high-pressure heater comes from the exhaust steam of the ultra-high-pressure cylinder. No regenerative extraction steam pipeline is provided on the high-pressure cylinder of the steam turbine. The steam required for heating No. 2 high-pressure heater, No. 3 high-pressure heater, No. 4 high-pressure heater, and No. 5 high-pressure heater is provided by the regenerative feed water pump steam turbine. The steam source of the auxiliary drive steam turbine 8 of the feed water pump is provided by the regenerative small steam turbine 4 in one way and by the exhaust steam of the medium-pressure cylinder of the main engine in the other way. The exhaust steam of the auxiliary drive steam turbine 8 of the feed water pump converges with the main engine extraction steam pipeline of No. 1 low-pressure heater to jointly heat No. 1 low-pressure heater. The heating steam of No. 2 low-pressure heater, No. 3 low-pressure heater, and No. 4 low-pressure heater is provided by the low-pressure cylinder of the main engine.

[0033] Specifically, the drain water of No. 1 high-pressure heater, No. 2 high-pressure heater, No. 3 high-pressure heater, and No. 4 high-pressure heater enters the next-level heater by means of step-by-step gravity flow, and the drain water of No. 5 high-pressure heater enters the deaerator 10. The drain water of No. 1 low-pressure heater, No. 2 low-pressure heater, and No. 3 low-pressure heater enters the next level by means of step-by-step gravity flow, and the drain water of No. 4 low-pressure heater enters the condenser.

[0034] The regenerative small steam turbine 4 and the auxiliary drive steam turbine 8 of the feed water pump configured in this embodiment do not have a condenser, and their exhaust steam still has a certain pressure and temperature and can continue to be used as the extraction steam of the heater. On the one hand, the waste heat utilization effect of the unit is improved, and on the other hand, the equipment investment is reduced.

[0035] This system can reduce the designed output of the steam turbine supporting the feed water pump by 1×100% and improve the operating efficiency of the feed water pump steam turbine unit under partial load. At the same time, the equipment investment cost of the feed water pump steam turbine can be reduced. The speed regulation device adopts the planetary gear speed regulation method, and compared with the hydraulic coupling speed regulation method, the speed regulation efficiency under the entire operating condition is improved.

[0036] Adopting the method of using an auxiliary steam turbine to drive the fore pump can make more full use of the energy of the exhaust steam of the medium-pressure cylinder and the exhaust steam of the regenerative feed water pump steam turbine, and deepen the cascade utilization of energy. Another function of the auxiliary steam turbine is to drive the feed water pump together with the regenerative small steam turbine under high load to ensure the safe and stable operation of the unit under high load conditions. The use of the 3S clutch in the present invention can make the adjustment of the operating output of the feed water pump smoother, and automatically realize the drive object of the auxiliary steam turbine according to the speed setting of the 3S clutch.

[0037] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A feed water pump drive system for a secondary reheat unit, characterized in that, it includes a steam turbine, a boiler, a balance generator, a regenerative steam turbine, a feed water pump speed regulating device, a 3S clutch, a feed water pump, an auxiliary drive steam turbine for the feed water pump, a booster pump, a deaerator, a high-pressure heater, and a low-pressure heater; one end of the regenerative steam turbine is connected to the balance generator, and the other end is connected to the feed water pump speed regulating device, serving as the main driving force for the feed water pump; the auxiliary drive steam turbine for the feed water pump serves as a superimposed driving force, with one end connected to the feed water pump speed regulating device and the other end connected to the booster pump of the feed water pump; one end of the auxiliary drive steam turbine for the feed water pump is connected to the feed water pump speed regulating device through the 3S clutch, and the other end is connected to the booster pump of the feed water pump, and automatically meshes with the feed water pump speed regulating device through the 3S clutch, and is used to provide a superimposed driving force for the feed water pump when the unit is at high load and drive the booster pump to operate when the unit is at low load; the feed water pump speed regulating device includes an input shaft, a superimposed gear, and an output shaft. The regenerative steam turbine is connected to the input shaft. The auxiliary drive steam turbine for the feed water pump is connected to the superimposed gear through the 3S clutch. The output shaft is connected to the feed water pump and is used to transmit the superimposed output of the regenerative steam turbine and the auxiliary drive steam turbine for the feed water pump to the feed water pump; the steam inlet of the regenerative steam turbine is provided by the cold section steam discharged from the ultra-high pressure cylinder of the steam turbine; several steam extraction holes are arranged on the regenerative steam turbine for respectively providing steam to the high-pressure heaters at corresponding energy levels; after the exhaust steam of the regenerative steam turbine converges with another extraction steam of the unit main engine, it is respectively supplied to the auxiliary drive steam turbine for the feed water pump and the deaerator for use; the exhaust steam of the auxiliary drive steam turbine for the feed water pump converges with the extraction steam of the unit main engine and then enters the low-pressure heater at the corresponding energy level.

2. The feed water pump drive system for a secondary reheat unit according to claim 1, characterized in that, the operating mode of the regenerative steam turbine is constant speed operation at 3000 r / min, and the operating mode of the auxiliary drive steam turbine for the feed water pump is variable speed operation; the rated output of the regenerative steam turbine can approximately meet 80% of the total power of the feed water pump. When the unit is at high load, the remaining driving force requirement of the feed water pump is met by the auxiliary drive steam turbine for the feed water pump.

3. The feed water pump drive system for a secondary reheat unit according to claim 1, characterized in that, the set value of the meshing speed of the 3S clutch is set according to the specific unit parameters. When the output of the feed water pump is below 80%, the auxiliary drive steam turbine for the feed water pump is not connected to the superimposed gear and is only used to drive the booster pump to operate; when the output requirement of the feed water pump is greater than 80%, the auxiliary drive steam turbine for the feed water pump is connected to the superimposed gear to increase the output of the feed water pump.

4. The feed water pump drive system for a secondary reheat unit according to claim 1, characterized in that, the regenerative steam turbine and the auxiliary drive steam turbine for the feed water pump are not provided with a condenser, and their exhaust steam is continued to be used for the heaters.

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