Low-pressure water supply system for waste heat boiler of back-pressure gas turbine

Abstract

The invention relates to a low-pressure water supply system of a waste heat boiler of a backpressure gas turbine, and belongs to the technical field of boiler equipment. The system comprises a low-pressure steam pocket, a low-pressure economizer and a vacuum deoxidizing device, an inlet of the vacuum deoxidizing device is connected with a demineralized water source through a deoxidizing inlet pipeline, an outlet of the vacuum deoxidizing device is connected with an inlet of the low-pressure economizer through a deoxidizing outlet pipeline, and an outlet pipeline of the economizer is connected with the low-pressure steam pocket through a deoxidizing head. A booster pump is arranged on the deoxygenization outlet pipeline, an inlet of the booster pump is communicated with an outlet of the vacuum deoxygenization device, an outlet of the booster pump is communicated with an inlet of the low-pressure economizer, and an outlet of the booster pump is further connected with the deoxygenization inlet pipeline through a valve adjusting bypass provided with an adjusting valve. According to the low-pressure water supply system, redundant flow of low-pressure water supply is sent back to the vacuum deoxidizing device through the valve adjusting bypass, the redundant flow circulates between the booster pump and the vacuum deoxidizing device, and therefore the technical problem that when the waste heat boiler is in a low load state, pressure building is generated by the low-pressure water supply system is solved.

Description

Technical Field

[0001] The invention relates to a low-pressure water supply system for a back-pressure combustion engine waste heat boiler, belonging to the technical field of boiler equipment. Background Art

[0002] After the steam and hot water from the waste heat boiler of the back pressure gas turbine are input to users outside the plant, they are usually not recycled. At this time, the waste heat boiler needs to be supplemented with desalted water. Since the oxygen content of desalted water is as high as 7~8mg / L, it cannot meet the regulatory requirements and also causes great oxygen corrosion damage to the boiler low-pressure water supply system. Therefore, the low-pressure water supply system needs to be equipped with a vacuum deaerator to perform preliminary deoxygenation on the desalted water. The existing low-pressure water supply system is as follows Figure 1 As shown, after the desalted water is mixed with the hot water pumped from the low-pressure economizer 2 in the deaerator inlet pipeline 4, it enters the vacuum deaerator 3 for deaeration. The desalted water after deaeration is sent to the low-pressure economizer 2 by the booster pump 13 for heating and then enters the low-pressure drum 1 through the economizer outlet pipeline 6 and the deaerator head 7. In the above-mentioned low-pressure water supply system, the booster pump 13 is conventionally a fixed-speed pump. When the waste heat boiler is partially or low-loaded, the opening of the economizer outlet regulating valve 8 is reduced, while the water supply flow rate sent by the booster pump 13 remains unchanged, which leads to pressure build-up in the low-pressure water supply system. After the low-pressure water supply system is pressurized, since the design pressure of the heating system 11 is relatively lower than that of the waste heat boiler side, the pressure buildup will inevitably bring safety hazards to the operation of the heating system 11; at the same time, the relief valve at the outlet of the low-pressure economizer 2 also needs to increase the set value, which will have an adverse effect on the low-pressure water supply system; if the desalted water heating regulating valve 17 is fully opened, and the second heating pipeline 12 is used to send the excess flow back to the vacuum deaerator 3, the water temperature in the vacuum deaerator 3 will cause an increase, affecting the deoxygenation effect. Summary of the invention

[0003] The present invention mainly solves the technical problem in the prior art that the low-pressure water supply system generates pressure build-up when the waste heat boiler is running at low load, and provides a back-pressure gas turbine waste heat boiler low-pressure water supply system which does not generate pressure build-up when the waste heat boiler is running at low load.

[0004] The present invention solves the above technical problems mainly through the following technical solutions: the present invention comprises a low-pressure steam drum, a low-pressure economizer, a vacuum deaerator, an inlet of the vacuum deaerator is connected to a desalted water source through a deaerator inlet pipeline, an outlet of the vacuum deaerator is connected to an inlet of the low-pressure economizer through a deaerator outlet pipeline, an economizer outlet pipeline is provided at the outlet of the low-pressure economizer, an outlet of the economizer outlet pipeline is connected to the low-pressure steam drum through a deaerator head, a low-pressure economizer is provided with a hot water pumping outlet, and the hot water pumping outlet is connected to a heating system through a first heating pipeline and connected to a heating system through a first heating pipeline. The second heating pipeline is connected to the deaerator inlet pipeline, the heating system is connected to the low-pressure economizer inlet through the heat network circulation pump, and a booster pump is arranged on the deaerator outlet pipeline. The booster pump inlet is connected to the vacuum deaerator outlet and the outlet is connected to the low-pressure economizer inlet. It is characterized in that the booster pump outlet is also connected to the deaerator inlet pipeline through a regulating valve bypass provided with a regulating valve, the flow of the regulating valve bypass is controlled by the regulating valve according to the flow and pressure of the economizer outlet pipeline, and the low-pressure feed water entering the regulating valve bypass forms a circulation between the vacuum deaerator and the booster pump.

[0005] Preferably, the regulating valve is controlled by a DCS control system, and the regulating valve opens when the flow rate of the economizer outlet pipeline decreases, causing the low-pressure feed water pressure to be greater than the set working pressure.

[0006] Preferably, the opening of the regulating valve is interlocked and controlled by a DCS control system according to the opening of the economizer outlet regulating valve.

[0007] Preferably, the booster pumps are arranged in two groups connected in parallel.

[0008] The present invention has a simple structure and has the following advantages: In the present invention, a regulating valve bypass is provided at the outlet of the booster pump. When the waste heat boiler is running at low load, the flow rate of the economizer outlet pipeline decreases, resulting in an increase in the low-pressure feed water pressure and pressure build-up, the regulating valve can be opened, and the excess flow of the low-pressure feed water is sent back to the vacuum deaerator by the regulating valve bypass. This excess flow circulates between the booster pump and the vacuum deaerator, thereby avoiding pressure build-up in the low-pressure feed water system and ensuring the safe operation of the heating system.

[0009] In the present invention, the circulating water returned to the vacuum deaerator through the regulating valve bypass is not heated by the low-pressure economizer, thereby avoiding the technical problem in the prior art that the excess flow is sent back to the vacuum deaerator through the second heating pipeline, causing the water temperature in the vacuum deaerator to increase and affecting the deoxygenation effect.

[0010] Furthermore, the regulating valve is automatically controlled through a DCS control system, with a high degree of automation.

[0011] Furthermore, the opening and closing of the regulating valve is interlocked and controlled by the DCS control system in response to the opening of the economizer outlet regulating valve. The flow of the regulating valve bypass can respond to the flow changes of the economizer outlet pipeline in a timely manner, thereby maintaining the stability of the working pressure of the low-pressure feed water system and making the system run safely and reliably.

[0012] Furthermore, there are two groups of booster pumps, one of which operates normally and the other is on standby. When the operating group of booster pumps fails and needs to be repaired or replaced, the standby group of booster pumps is put into operation, thereby not affecting the normal operation of the low-pressure water supply system.

[0013] Therefore, the present invention solves the technical problem in the prior art that the low-pressure water supply system generates pressure build-up when the waste heat boiler is under low load, and has the advantages of simple system, stable operation, and strong applicability to unit load. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Attached Figure 1 It is a schematic diagram of the prior art; Attached Figure 2 It is a schematic diagram of a preferred embodiment of the present invention.

[0015] Explanation of the reference numerals: 1. low-pressure steam drum; 2. low-pressure economizer; 3. vacuum deaerator; 4. deaerator inlet pipeline; 5. deaerator outlet pipeline; 6. economizer outlet pipeline; 7. deaerator header; 8. economizer outlet regulating valve; 9. hot water outlet; 10. first heating pipeline; 11. heating system; 12. second heating pipeline; 13. booster pump; 14. regulating valve; 15. regulating valve bypass; 16. DCS control system; 17. desalted water heating regulating valve; 18. heating network circulation pump. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0017] Embodiment 1: As attached Figure 2 As shown, the present invention comprises a low-pressure steam drum 1, a low-pressure economizer 2, and a vacuum deaerator 3; The inlet of the vacuum deaerator 3 is connected to the desalted water source through the deaerator inlet pipeline 4, and the outlet of the vacuum deaerator 3 is connected to the inlet of the low-pressure economizer 2 through the deaerator outlet pipeline 5; The outlet of the low-pressure economizer 2 is provided with an economizer outlet pipeline 6, and the outlet of the economizer outlet pipeline 6 is connected to the low-pressure steam drum 1 through a deaerator header 7; The low-pressure economizer 2 is provided with a hot water extraction outlet 9, which is connected to a heating system 11 through a first heating pipeline 10, and an outlet of the heating system 11 is connected to an inlet of the low-pressure economizer 2 through a heat network circulation pump 18; The hot water outlet 9 is also connected to the deoxygenation inlet pipeline 4 through the second heating pipeline 12, and the second heating pipeline 12 is provided with a desalted water heating regulating valve 17; A booster pump 13 is provided on the deaerator outlet pipeline 5, the inlet of the booster pump 13 is connected to the outlet of the regulating valve bypass 15, and the outlet is connected to the inlet of the low-pressure economizer 2. The outlet of the booster pump 13 is also connected to the deaerator inlet pipeline 4 through the regulating valve bypass 15 provided with a regulating valve 14. The feed water entering the regulating valve bypass 15 from the outlet of the booster pump 13 returns to the vacuum deaerator 3 and forms a circulation between the vacuum deaerator 3 and the booster pump 13. The flow rate of the regulating valve bypass 15 is controlled by the regulating valve 14 according to the flow rate and pressure of the economizer outlet pipeline 6; The regulating valve 14 is connected to the DCS control system 16 with the economizer outlet regulating valve 8. The opening and closing of the regulating valve 14 is interlocked and controlled by the DCS control system 16 according to the opening of the economizer outlet regulating valve 8. The parameters of the opening of the economizer outlet regulating valve 8 are converted into standard signals and input into the logic controller. After the logic operation, a control signal is generated to control the opening and closing of the regulating valve 14. The booster pumps 13 are arranged in two groups connected in parallel, one for use and one for standby.

[0018] When the waste heat boiler of the present invention is partially or low-loaded, the DCS control system 16 monitors the flow and pressure of the economizer outlet pipeline 6, collects the opening parameters of the economizer outlet regulating valve 8, converts the parameters into standard signals and inputs them into the logic controller, generates a control signal through logic operation and controls the regulating valve 14 to open through the actuator. After the regulating valve 14 is opened, the excess low-pressure feed water at the outlet of the booster pump 13 returns to the vacuum deaerator 3 through the regulating valve bypass 15 and circulates between the vacuum deaerator 3 and the booster pump 13, and the low-pressure feed water system maintains normal working pressure and operates stably.

[0019] Of course, the above drawings and embodiments are only used to explain and illustrate the present invention, and cannot be used as improper limitations of the present invention. Any technical solutions obtained by those skilled in the art making equivalent adjustments and changes based on the present invention fall within the protection scope of the present invention.

Claims

1. A low-pressure water supply system for a back-pressure combustion engine waste heat boiler, comprising a low-pressure steam drum (1), a low-pressure economizer (2), and a vacuum deaerator (3), wherein the inlet of the vacuum deaerator (3) is connected to a desalted water source via a deaerator inlet pipeline (4), the outlet of the vacuum deaerator (3) is connected to the inlet of the low-pressure economizer (2) via a deaerator outlet pipeline (5), the outlet of the low-pressure economizer (2) is provided with an economizer outlet pipeline (6), the outlet of the economizer outlet pipeline (6) is connected to the low-pressure steam drum (1) via a deaerator header (7), and the outlet of the low-pressure economizer (2) is connected to the low-pressure steam drum (1) via a deaerator header (7). The coal burner (2) is provided with a hot water extraction outlet (9), the hot water extraction outlet (9) is connected to a heating system (11) through a first heating pipeline (10) and is connected to the deaeration inlet pipeline (4) through a second heating pipeline (12), the heating system (11) is connected to the inlet of a low-pressure economizer (2) through a heating network circulation pump (18), a booster pump (13) is provided on the deaeration outlet pipeline (5), the inlet of the booster pump (13) is connected to the outlet of the vacuum deaeration device (3) and the outlet is connected to the inlet of the low-pressure economizer (2), characterized in that: The outlet of the booster pump (13) is also connected to the deaerator inlet pipeline (4) via a regulating valve bypass (15) provided with a regulating valve (14); the flow rate of the regulating valve bypass (15) is controlled by the regulating valve (14) according to the flow rate and pressure of the economizer outlet pipeline (6); the low-pressure feed water entering the regulating valve bypass (15) forms a circulation between the vacuum deaerator device (3) and the booster pump (13).

2. A back-pressure gas turbine waste heat boiler low-pressure water supply system according to claim 1, characterized in that: The regulating valve (14) is controlled by a DCS control system (16), and the regulating valve (14) opens when the flow rate of the economizer outlet pipeline (6) decreases, causing the low-pressure feed water pressure to be greater than a set working pressure.

3. A back-pressure gas turbine waste heat boiler low-pressure water supply system according to claim 2, characterized in that: The opening degree of the regulating valve (14) is interlocked and controlled by the DCS control system (16) according to the opening degree of the economizer outlet regulating valve (8).

4. A low-pressure water supply system for a back-pressure waste heat boiler according to claim 1, 2 or 3, characterized in that: The booster pumps (13) are arranged in two groups connected in parallel.

Images