A steam-water linkage type flexible peak-shaving steam-driven feedwater pump system and operation method

Abstract

A steam-driven feedwater pump system and operation method for flexible peak regulation of steam-water linkage type, including a feedwater pump turbine, a ring-shaped mixed steam supplement stage is arranged on the feedwater pump turbine; a steam inlet speed closing valve and a steam inlet regulating valve are arranged on the high-pressure steam inlet side of the feedwater pump turbine, and a supplement steam speed closing valve and a supplement steam regulating valve are arranged on the low-pressure steam inlet side of the feedwater pump turbine; the feedwater side of the feedwater pump turbine is connected to the feedwater pump, and the feedwater side of the feedwater pump is connected in parallel to the feedwater pump minimum flow valve pipeline and the feedwater recirculation bypass for deep peak regulation; the feedwater recirculation bypass for deep peak regulation includes an electric valve before the recirculation bypass pressure reducing regulating valve, a feedwater recirculation bypass pressure reducing regulating valve and a manual valve after the recirculation bypass pressure reducing regulating valve, which are sequentially connected in series through a pipeline; and finally connected to a deaerator. The present invention can reduce the influence of the auxiliary system on the flexible peak regulation depth of the main engine.

Description

Technical Field

[0001] The patent of this invention relates to a steam-water linkage type steam-driven feed water pump system with flexible peak regulation, which can be widely used in the optimization design and selection of steam-driven feed water pump systems in coal-fired power generation projects. The invention is also applicable to systems that use steam-driven feed water pumps in gas-fired power plants, waste power plants, biomass power plants, blast furnace gas waste heat power plants and other units, and is used to improve the high efficiency and wide load characteristics of the units. Background Art

[0002] In order to improve and deepen the sharing mechanism of power peak load auxiliary services, increase the space for absorbing clean energy such as wind power and photovoltaic power, and improve the peak load capacity of the power grid, the main peak load load task is currently undertaken by coal-fired power units, which puts forward higher requirements for deep peak load load of coal-fired power. However, for the main auxiliary system, the feedwater pump turbine is designed and selected according to full load. When the deep peak load is adjusted to low load, the feedwater pump turbine runs near the critical speed, and due to the minimum steam inlet requirement of the feedwater pump turbine, the feedwater pump turbine output cannot be further adjusted, causing the feedwater pump turbine to be mismatched with the boiler feedwater pump, causing the auxiliary system to affect the main engine to further reduce the deep peak load. Summary of the invention

[0003] The technical problem to be solved by the present invention is: in order to improve the flexibility of deep peak regulation of the steam-driven feed water pump system, enhance the adaptability of the feed water system to full load, and improve the reliability of the operation of thermal power generating units, a steam-water linkage type flexible peak regulation steam-driven feed water pump system is proposed.

[0004] The technical solution of the present invention is specifically as follows:

[0005] A steam-driven feedwater pump system with flexible peak regulation of steam-water linkage type comprises a feedwater pump turbine, on which an annular mixing steam supply stage is arranged; a steam inlet speed shut-off valve and a steam inlet regulating valve are arranged on the high-pressure steam inlet side of the feedwater pump turbine, and a steam supply speed shut-off valve and a steam supply regulating valve are arranged on the low-pressure steam inlet side of the feedwater pump turbine; the feedwater side of the feedwater pump turbine is connected to the feedwater pump, and the feedwater side of the feedwater pump is connected in parallel to the feedwater pump minimum flow valve pipeline and a feedwater recirculation bypass for deep peak regulation; the feedwater recirculation bypass for deep peak regulation comprises an electric valve in front of the recirculation bypass pressure reducing regulating valve, a feedwater recirculation bypass pressure reducing regulating valve and a manual valve behind the recirculation bypass pressure reducing regulating valve, which are connected in series in sequence through pipelines; the feedwater pump minimum flow valve pipeline and the feedwater recirculation bypass output end for deep peak regulation are both connected to a deaerator.

[0006] The feedwater pump turbine adopts a double-pressure steam-supplementing type turbine.

[0007] The minimum flow valve pipeline of the water supply pump includes an electric valve before the minimum flow valve, a minimum flow valve of the water supply pump and a manual valve after the minimum flow valve, which are sequentially connected in series through the pipeline.

[0008] An operation method using the above system, 1) unit startup and shutdown conditions: in a unit using a steam-driven feedwater pump as the main engine startup pump, steam side: startup steam is high-pressure steam, the steam inlet speed shutoff valve 4 and the steam inlet regulating valve 5 are open and participate in regulation, and the supplementary steam speed shutoff valve 6 and the supplementary steam regulating valve 7 are both in a closed state; feedwater side: the feedwater pump minimum flow valve pipeline 16 is in a working state, the electric valve 11 before the minimum flow valve and the manual valve 13 after the minimum flow valve are in a fully open state, the feedwater pump minimum flow valve 12 participates in regulation, and the feedwater minimum flow valve pipeline ensures that the feedwater pump is running at or above its allowed minimum flow rate, and the corresponding feedwater recirculation bypass pressure reducing regulating valve 9 is in a closed state; shutdown condition, the state of the relevant valves is the same as the startup condition;

[0009] 2) High-load operation condition of the unit: low-pressure supplementary steam is turned on, and the insufficient part of high-pressure inlet steam output is provided by low-pressure supplementary steam. The low-pressure supplementary steam is supplemented to the annular mixed supplementary steam stage 14 of the feedwater pump turbine. At this time, the high-pressure inlet steam speed closing valve 4 and the high-pressure inlet steam regulating valve 5 are in a fully open state, and the corresponding low-pressure supplementary steam speed closing valve 6 and the supplementary steam regulating valve 7 are opened to participate in the regulation. The turbine output is adjusted to match the feedwater pump through the high-pressure inlet steam regulating valve 5 and the supplementary steam regulating valve 7. At this time, the feedwater pump minimum flow valve pipeline 16 on the feedwater side and the feedwater recirculation bypass 15 for deep peak regulation are in a closed state;

[0010] 3) Unit deep peak load operation condition: First, the low-pressure steam supply speed closing valve 6 and the steam supply regulating valve 7 on the steam side are in a closed state, and the steam supply flow is only adjusted by the high-pressure steam inlet speed closing valve 4 and the high-pressure steam inlet regulating valve 5. Under the premise of ensuring the minimum steam supply requirement or the minimum allowable speed requirement of the feedwater pump turbine, the general turbine output is greater than or equal to the demand of the feedwater pump. Since the high-pressure steam inlet speed closing valve 4, the high-pressure steam inlet regulating valve 5 and the high-pressure side of the turbine are designed to flow at partial load, its low-load regulation characteristics are better; secondly, During deep peak regulation, the feed water recirculation bypass is used to consume the feed water flow that does not match the feed water pump turbine output and the feed water pump demand, to ensure that the feed water flow supplied to the high-pressure heater system meets the host demand. At this time, the electric valve 8 in front of the recirculation bypass pressure reducing regulating valve and the manual valve 10 behind the recirculation bypass pressure reducing regulating valve are both in the fully open state. The feed water recirculation bypass pressure reducing regulating valve 9 adjusts the valve opening according to the difference between the feed water pump output flow and the boiler demand to ensure the balance of the feed water volume. The corresponding feed water pump minimum flow valve 12 is in the closed state.

[0011] The beneficial effects of the present invention are as follows: the steam-water linkage type flexible peak-shaving steam-driven feedwater pump system proposed in the present invention adopts a steam-supplementing steam turbine on the steam side to increase the matching of the low-load steam turbine and the feedwater pump, and utilizes a feedwater recirculation bypass on the feedwater side to improve the safety and reliability of low-load operation, thereby reducing the influence of the auxiliary system on the flexible peak-shaving depth of the main engine, improving the high-efficiency wide-load characteristics and safety and reliability of the auxiliary system, and having broad prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a process flow chart of the steam-driven water supply pump system with flexible peak regulation of steam-water linkage in the present invention.

[0013] In the figure: 1. feedwater pump turbine, 2. boiler feedwater pump, 3. deaerator, 4. steam inlet speed shut-off valve, 5. steam inlet regulating valve, 6. steam supply speed shut-off valve, 7. steam supply regulating valve, 8. electric valve before recirculation bypass pressure reducing regulating valve, 9. feedwater recirculation bypass pressure reducing regulating valve, 10. manual valve after recirculation bypass pressure reducing regulating valve, 11. electric valve before minimum flow valve, 12. feedwater pump minimum flow valve, 13. manual valve after minimum flow valve, 14. annular mixing steam supply stage, 15. feedwater recirculation bypass for deep peak regulation, 16. feedwater pump minimum flow valve pipeline. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0016] like Figure 1 As shown, a steam-water linkage type flexible peak-shaving steam-driven feedwater pump system includes a feedwater pump steam turbine 1. In order to improve the wide load characteristics of the feedwater pump steam turbine, the feedwater pump steam turbine 1 adopts a double-pressure steam supplementation steam turbine, and an annular mixed steam supplementation stage 14 is configured on the feedwater pump steam turbine 1. The high-pressure steam inlet side of the feedwater pump steam turbine 1 is configured with a steam inlet speed shut-off valve 4 and a steam inlet regulating valve 5, and the low-pressure steam inlet side of the feedwater pump steam turbine 1 is provided with a steam supplementation speed shut-off valve 6 and a steam supplementation regulating valve 7.

[0017] The design principle of the feedwater pump turbine 1 is as follows: 1) The steam inlet speed shut-off valve 4 and the steam inlet regulating valve 5 are arranged on the high-pressure steam inlet side. Generally, the earlier the turbine stage is, the greater the pressure is and the smaller the flow area of ​​the turbine is. Therefore, the steam inlet speed shut-off valve 4, the steam inlet regulating valve 5 and the flow capacity of the front stage of the turbine on the high-pressure steam inlet side are tilted towards partial load as much as possible, that is, the high-pressure steam inlet volume is reduced as much as possible, and the design margin of the turbine is reduced. At this time, the regulating valve of the high-pressure steam inlet can be fully opened at the design flow rate, and the part exceeding the design flow rate is provided by the supplementary steam valve. The high-pressure steam inlet regulating valve has no throttling loss, thereby improving the efficiency of all working conditions under the design load and below, and the wide load adaptability of the auxiliary machine is better. 2) The low-pressure steam inlet side is equipped with a supplementary steam quick-closing valve 6 and a supplementary steam regulating valve 7. Generally, the flow area of ​​the steam turbine is proportional to the blade height. The higher the blade height, the larger the flow area. After configuring the annular mixed supplementary steam stage, the blade height is appropriately increased, and the flow capacity of the corresponding low-pressure side is increased. The low-pressure supplementary steam is supplemented to the low-pressure annular mixed supplementary steam stage of the steam turbine through the supplementary steam valve. The low-pressure supplementary steam fully utilizes the flow area of ​​the low-pressure side of the steam turbine, and the low-pressure supplementary steam makes up for the insufficient part of the high-pressure inlet steam output. The total steam volume of the high-pressure inlet steam and the low-pressure supplementary steam can meet the output demand of the feedwater pump under full load conditions and reserve a certain margin. Since it is achievable, the flow capacity of the steam turbine on the high-pressure steam inlet side is designed according to partial load, the throttling loss of the steam inlet regulating valve 5 is reduced, and the economy under partial load is improved; an annular mixing and supplementary steam stage 14 is arranged on the turbine body on the low-pressure side, and the low-pressure supplementary steam is supplemented to the front of the low-pressure annular mixing and supplementary steam stage of the steam turbine through the supplementary steam valve, and the low-pressure supplementary steam makes full use of the flow area on the low-pressure side of the steam turbine; the total steam intake of the high-pressure inlet steam and the low-pressure supplementary steam can meet the output demand of the feedwater pump under full load conditions and reserve a certain margin.

[0018] The feed water side of the feed water pump turbine 1 is connected to the feed water pump 2, and the feed water side of the feed water pump 2 is connected in parallel to the feed water pump minimum flow valve pipeline 16 and the feed water recirculation bypass 15 for deep peak regulation. Among them, the feed water pump minimum flow valve pipeline 16 includes an electric valve 11 before the minimum flow valve, a feed water pump minimum flow valve 12 and a manual valve 13 after the minimum flow valve, which are connected in series in sequence through the pipeline. The feed water recirculation bypass 15 for deep peak regulation includes an electric valve 8 before the recirculation bypass pressure reducing regulating valve, a feed water recirculation bypass pressure reducing regulating valve 9 and a manual valve 10 after the recirculation bypass pressure reducing regulating valve, which are connected in series in sequence through the pipeline. Finally, the output ends of the feed water pump minimum flow valve pipeline 16 and the feed water recirculation bypass 15 for deep peak regulation are both connected to the deaerator 3.

[0019] The design principle of the feedwater pump 2 is as follows: according to the peak-shaving requirements of the power grid, the frequency of deep peak-shaving is relatively high. If a minimum flow valve is used to balance the matching of the feedwater pump output and the boiler feedwater demand, the minimum flow valve is frequently opened, and the pressure difference before and after is relatively large. If it is adjusted for a long time, the minimum flow valve will leak and the reliability of the minimum flow valve will deteriorate. Therefore, in order to ensure the safety and reliability of the feedwater pump system, a feedwater recirculation bypass 15 for deep peak-shaving is arranged in parallel on the feedwater pump minimum flow valve pipeline 16 of the original boiler on the feedwater side. A set of recirculating bypass 15 for deep peak-shaving is configured. The frequently opened pressure reducing regulating device is used to match the imbalance between the feedwater pump output and the boiler feedwater demand under the deep peak load of the unit. The capacity of the pressure reducing regulating device is designed according to the maximum value of the difference between the feedwater pump output and the boiler feedwater demand that may occur during the deep peak load regulation, and a certain margin is reserved; the feedwater pump minimum flow valve 12 is only used to protect the minimum flow requirement of the feedwater pump during the startup and shutdown stages of the feedwater pump 2. The two routes are logically interlocked and controlled through the main engine load parameters to ensure the realization of their respective functions and to ensure the safe and reliable operation of the water supply system within the full load range.

[0020] It should be noted that, in order to ensure controllability, the above-mentioned steam inlet speed closing valve 4, steam inlet regulating valve 5, steam supplement speed closing valve 6, steam supplement regulating valve 7, electric valve before recirculation bypass pressure reducing regulating valve 8, feed water recirculation bypass pressure reducing regulating valve 9, electric valve before minimum flow valve 11 and feed water pump minimum flow valve 12 are all connected to the control system.

[0021] The working principle and working process of the present invention are:

[0022] The steam-water linkage type flexible peak-shaving steam-driven feed water pump system provided by the present invention mainly explains the working principle and working process from the following three aspects:

[0023] 1) Unit startup and shutdown conditions

[0024] In the unit using steam-driven feedwater pump as the main engine starting pump, on the steam side: the starting steam is high-pressure steam, and no supplementary steam is required, so the steam inlet speed closing valve 4 and the steam inlet regulating valve 5 are opened and participate in the regulation to ensure the output of the feedwater pump during the startup phase, and the corresponding supplementary steam speed closing valve 6 and the supplementary steam regulating valve 7 are in a closed state; on the feedwater side: the feedwater pump minimum flow valve pipeline 16 is in a working state, the electric valve 11 before the minimum flow valve and the manual valve 13 after the minimum flow valve are in a fully open state, and the feedwater pump minimum flow valve 12 participates in the regulation, and the feedwater pump is ensured to operate at or above its allowed minimum flow through the feedwater minimum flow valve pipeline to protect the safe and reliable operation of the feedwater pump, and the corresponding feedwater recirculation bypass pressure reducing regulating valve 9 is in a closed state. In the shutdown condition, the status of the relevant valves is the same as the startup condition.

[0025] 2) High load operation of the unit

[0026] When the unit is operating at high load, the designed flow of the high-pressure steam inlet of the feedwater pump turbine cannot meet the output requirement of the feedwater pump. At this time, the low-pressure supplementary steam is turned on to provide the insufficient output of the high-pressure steam inlet. The low-pressure supplementary steam is supplemented into the annular mixing supplementary steam stage 14 of the feedwater pump turbine. At this time, the high-pressure steam inlet speed closing valve 4 and the high-pressure steam inlet regulating valve 5 are in a fully open state without throttling loss. The corresponding low-pressure steam supplementary speed closing valve 6 and the supplementary steam regulating valve 7 are opened to participate in the regulation. The turbine output is adjusted to match the feedwater pump through the high-pressure steam inlet regulating valve 5 and the supplementary steam regulating valve 7 to ensure the boiler feedwater demand. At this time, the minimum flow valve pipeline 16 of the feedwater pump on the feedwater side and the feedwater recirculation bypass 15 for deep peak regulation are in a closed state.

[0027] 3) Unit deep peak load operation conditions

[0028] When the unit participates in deep peak regulation, the load reduction range of the main auxiliary equipment does not match that of the main engine, so it is necessary to balance this mismatch through the steam-water linkage type flexible peak regulation steam-driven feedwater pump system proposed in the present invention. First, the low-pressure steam supplement speed closing valve 6 and the steam supplement regulating valve 7 on the steam side are in a closed state, and the steam inlet flow rate is only adjusted by the high-pressure steam inlet speed closing valve 4 and the high-pressure steam inlet regulating valve 5. Under the premise of ensuring the minimum steam inlet requirement or the minimum allowable speed requirement of the feedwater pump turbine, the general turbine output is greater than or equal to the demand of the feedwater pump. Since the high-pressure steam inlet speed closing valve 4, the high-pressure steam inlet regulating valve 5 and the high-pressure side of the turbine are designed to flow at partial load, its low-load regulation characteristics are better, that is, the turbine output is better matched with the demand of the feedwater pump. Secondly, the feed water recirculation bypass can be used for deep peak regulation to consume the feed water flow that does not match the feed water pump turbine output and the feed water pump demand, to ensure that the feed water flow supplied to the high-pressure heater system meets the main engine demand. At this time, the electric valve 8 in front of the recirculation bypass pressure reducing regulating valve and the manual valve 10 behind the recirculation bypass pressure reducing regulating valve are both in the fully open state, and the feed water recirculation bypass pressure reducing regulating valve 9 adjusts the valve opening according to the difference between the feed water pump output flow and the boiler demand to ensure the balance of the feed water volume, and the corresponding feed water pump minimum flow valve 12 is in the closed state.

[0029] The present invention is applicable to the optimization design and selection of steam-driven feedwater pump systems for power generation projects, improves the flexibility of steam-driven feedwater pump systems in participating in deep peak regulation, improves the adaptability of the feedwater system at full load, and improves the reliability of generator set operation. The steam side uses a supplementary steam turbine with an annular mixed supplementary steam stage 14 to increase the matching of the feedwater pump turbine 1 and the boiler feedwater pump 2 at low load, and the feedwater side uses a feedwater recirculation bypass 15 for deep peak regulation to improve the safety and reliability of low-load operation.

[0030] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several changes and improvements can be made without departing from the overall concept of the present invention, which should also be regarded as the scope of protection of the present invention.

Claims

1. A steam-water linkage type flexible peak-shaving steam-driven water supply pump system, characterized in that: The invention comprises a feedwater pump steam turbine (1), wherein an annular mixing steam supply stage (14) is arranged on the feedwater pump steam turbine (1); a steam supply speed closing valve (4) and a steam supply regulating valve (5) are arranged on the high-pressure steam inlet side of the feedwater pump steam turbine (1), and a steam supply speed closing valve (6) and a steam supply regulating valve (7) are arranged on the low-pressure steam inlet side of the feedwater pump steam turbine (1); the feedwater side of the feedwater pump steam turbine (1) is connected to a feedwater pump (2), and the feedwater side of the feedwater pump (2) is connected in parallel to a feedwater pump minimum flow valve pipeline. (16) and a water supply recirculation bypass for deep peak regulation (15); the water supply recirculation bypass for deep peak regulation (15) comprises an electric valve (8) before the recirculation bypass pressure reducing regulating valve, a water supply recirculation bypass pressure reducing regulating valve (9) and a manual valve (10) after the recirculation bypass pressure reducing regulating valve, which are sequentially connected in series through a pipeline; the water supply pump minimum flow valve pipeline (16) and the output end of the water supply recirculation bypass for deep peak regulation (15) are both connected to the deaerator (3); The water supply pump minimum flow valve pipeline (16) comprises a minimum flow valve front electric valve (11), a water supply pump minimum flow valve (12) and a minimum flow valve rear manual valve (13) which are sequentially connected in series through the pipeline; The running method is: 1) Unit startup and shutdown conditions: In a unit using a steam-driven feedwater pump as the main engine startup pump, on the steam side: the startup steam is high-pressure steam, the steam inlet speed shut-off valve (4) and the steam inlet regulating valve (5) are open and participate in the regulation, and the supplementary steam speed shut-off valve (6) and the supplementary steam regulating valve (7) are both in the closed state; on the feedwater side: the feedwater pump minimum flow valve pipeline (16) is in the working state, the electric valve (11) before the minimum flow valve and the manual valve (13) after the minimum flow valve are in the fully open state, the feedwater pump minimum flow valve (12) participates in the regulation, and the feedwater pump is ensured to operate at or above its allowed minimum flow rate through the feedwater minimum flow valve pipeline, and the corresponding feedwater recirculation bypass pressure reducing regulating valve (9) is in the closed state; in the shutdown condition, the status of the relevant valves is the same as the startup condition; 2) High-load operation condition of the unit: the low-pressure supplementary steam is turned on, and the insufficient part of the high-pressure inlet steam output is provided by the low-pressure supplementary steam. The low-pressure supplementary steam is supplemented to the annular mixed supplementary steam stage (14) of the feedwater pump turbine. At this time, the high-pressure inlet steam speed closing valve (4) and the high-pressure inlet steam regulating valve (5) are in a fully open state, and the corresponding low-pressure supplementary steam speed closing valve (6) and the supplementary steam regulating valve (7) are opened to participate in the regulation. The turbine output is adjusted to match the feedwater pump through the high-pressure inlet steam regulating valve (5) and the supplementary steam regulating valve (7). At this time, the feedwater pump minimum flow valve pipeline (16) on the feedwater side and the feedwater recirculation bypass (15) for deep peak regulation are in a closed state; 3) Deep peak load regulation operation of the unit: First, the low-pressure steam supply speed closing valve (6) and the steam supply regulating valve (7) on the steam side are in a closed state, and the steam supply flow is only regulated by the high-pressure steam supply speed closing valve (4) and the high-pressure steam supply regulating valve (5); secondly, the feed water recirculation bypass is used for deep peak load regulation to consume the feed water flow that does not match the feed water pump turbine output and the feed water pump demand, so as to ensure that the feed water flow supplied to the high-pressure heater system meets the main engine demand. At this time, the electric valve (8) before the recirculation bypass pressure reducing regulating valve and the manual valve (10) after the recirculation bypass pressure reducing regulating valve are both in a fully open state. The feed water recirculation bypass pressure reducing regulating valve (9) adjusts the valve opening according to the difference between the feed water pump output flow and the boiler demand to ensure the balance of the feed water flow, and the corresponding feed water pump minimum flow valve (12) is in a closed state.

2. The steam-water linkage type flexible peak-shaving steam-driven water supply pump system according to claim 1 is characterized in that: The feedwater pump steam turbine (1) adopts a double-pressure steam supplement type steam turbine.

Images