Recirculating differential pressure power generation system and method suitable for ultralow-load operation of thermal power generating unit

Abstract

The invention belongs to the technical field of boiler water supply, and discloses a recirculation differential pressure power generation system and method suitable for ultralow-load operation of a thermal power generating unit. The system comprises a water supply differential pressure power generation stop valve, a high-pressure water supply power generation turbine, a small generator and a pressure sensor which are arranged in sequence; an inlet of the water supply pressure difference power generation stop valve is connected with an outlet of the water supply pump, an inlet of the high-pressure water supply power generation turbine is connected with an outlet of the water supply pressure difference power generation stop valve, and an outlet of the high-pressure water supply power generation turbine is connected with a recirculation bypass inlet of the deaerator. The signal is used for controlling the opening degree of the water supply pressure difference power generation stop valve 4. The pressure difference energy potential of the feed water recirculation pipeline during ultra-low load operation of the unit is used for generating power, and the safety problem and the energy loss problem of overlarge feed water recirculation pressure difference caused by feed water recirculation under the ultra-low load working condition are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of boiler feed water, and in particular relates to a recirculating pressure difference power generation system and method suitable for ultra-low load operation of thermal power units. Background Art

[0002] Under the ultra-low load operating conditions of thermal power plant units, the stable and efficient operation of the feedwater system becomes particularly important. As a key device to ensure stable water supply to the boiler, the safety of the feedwater pump's operation is directly related to the reliability of the entire unit. Typically, the minimum flow recirculation regulating valve of the feedwater pump is installed at the feedwater pump outlet and connected to the deaerator. Its purpose is to automatically open when the feedwater pump flow falls below the set minimum value, returning some deoxygenated water to the deaerator to prevent overheating and cavitation caused by insufficient flow in the feedwater pump. Although this traditional configuration can meet the safe operation requirements of the feedwater pump under low flow conditions, its energy utilization efficiency is low, especially under ultra-low load conditions. The large amount of high-pressure water only serves to reduce pressure and cool the water during the return process through the recirculation valve. The original pressure energy is not effectively recovered and utilized, resulting in energy waste.

[0003] With the increasing demand for flexible peak-shaving and deep regulation of thermal power units, it has become common for feedwater pumps to operate at low load for long periods of time. At this time, the recirculation flow is frequently activated and maintained at a high ratio, further amplifying the problem of energy waste. At the same time, the overall energy consumption level of the unit is limited by the energy consumption of auxiliary equipment, which puts pressure on the economic benefits of the unit. Most existing technologies focus on improving the thermal efficiency of the main engine or optimizing boiler operating parameters. The utilization of the recirculation pressure differential energy of the feedwater system is relatively weak, and there is a lack of effective energy recovery and comprehensive utilization methods, resulting in limited room for improvement in the overall efficiency of the system.

[0004] To address the above issues, one solution is to organically combine the minimum flow recirculation system of the high-pressure feedwater pump with a pressure differential power generation device, and to add a pressure differential power generation bypass in the feedwater pump recirculation pipeline. Specifically, by taking advantage of the significant pressure difference between the high-pressure feedwater pump outlet and the deaerator, a portion of the return water is introduced into the pressure differential power generation device, where energy is first recovered and generated, and then the pressure is reduced and returned to the deaerator. This not only fully utilizes the high-pressure potential energy at the feedwater pump outlet to achieve auxiliary power generation or supply energy for the unit's own load, but also reduces the energy consumption pressure of the feedwater pump when operating at low flow rates, ensures equipment safety, and improves operational economy.

[0005] However, this solution still faces many technical difficulties in practical application. First, the pressure difference power generation device needs to work in conjunction with the recirculation control valve. How to dynamically adjust the opening and closing and diversion ratio of the two according to the operating conditions to ensure the minimum flow requirement of the feed water pump while maximizing the pressure difference power generation is the key to system control. Secondly, the pressure and flow of high-pressure water after passing through the power generation device must accurately match the deaerator return requirements to prevent impact on the normal operation of the deaerator. Thirdly, the system must have sufficient response speed and adjustment capabilities under transient operating conditions such as start-up and shutdown, load fluctuations, etc., to avoid safety risks to the feed water pump or low energy recovery efficiency due to untimely system switching.

[0006] In summary, the deep integration of the feedwater pump minimum flow recirculation control valve with the differential pressure power generation system not only solves the technical challenges of ensuring safe feedwater pump operation and preventing cavitation during ultra-low load operation, but also achieves efficient recovery and utilization of high-pressure return energy. This represents a key technological innovation for enhancing the flexibility, energy conservation, and economical operation of thermal power units. Further in-depth research on system adaptive control and improving energy recovery efficiency will provide strong support for the high-quality transformation and sustainable development of the thermal power industry. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problem of large feed water recirculation bypass pressure difference and serious energy loss when the above-mentioned thermal power unit operates under ultra-low load conditions, and to provide a recirculating pressure difference power generation system and method that are suitable for ultra-low load operation of thermal power units.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a recirculating pressure difference power generation system that is suitable for ultra-low load operation of thermal power units, including a deaerator, the liquid outlet of the deaerator is connected to the water supply main pipe, the water supply main pipe is connected to the deaerator and the high-pressure water supply power generation turbine through two bypasses, the high-pressure water supply power generation turbine outlet is connected to the recirculating bypass inlet of the deaerator, and a water supply pressure difference power generation stop valve is provided on the bypass connecting the water supply main pipe to the high-pressure water supply power generation turbine. The pressure sensor is used to measure the pressure of the deaerator water tank, and its signal is used to control the opening of the water supply pressure difference power generation stop valve.

[0009] A further improvement of the present invention is that a water supply pump is provided upstream of the water supply main pipe.

[0010] A further improvement of the present invention is that a recirculation valve is provided on the bypass connecting the water supply main pipe to the deaerator.

[0011] A further improvement of the present invention is that the inlet of the water supply pressure difference power generation stop valve is connected to the outlet of the water supply pump.

[0012] A further improvement of the present invention is that the inlet of the high-pressure feedwater power generation turbine is connected to the outlet of the feedwater pressure difference power generation stop valve.

[0013] A further improvement of the present invention is that the feed water recirculation pressure difference power generation bypass is connected in parallel with the original feed water recirculation valve of the unit.

[0014] A further improvement of the present invention is that the flow rate of the water supply pump is the sum of the flow rate of the recirculation valve, the flow rate of the water supply pressure difference power generation stop valve and the flow rate of the water supply main pipe stop valve.

[0015] A further improvement of the present invention is that the design pressure difference of the high-pressure feedwater power generation turbine is the feedwater recirculation pressure difference when the unit is operating at 30% load.

[0016] A further improvement of the present invention is that the pressure sensor comprises a plurality of pressure measuring points arranged in the deaerator water tank, and the signal value of the pressure sensor is an average value of the detection values ​​of all the measuring points.

[0017] In a second aspect, the present invention provides a method for operating a recirculating pressure difference power generation system adapted to ultra-low load operation of a thermal power unit, comprising the following steps: The feed water pump presses the deoxygenated feed water into the main feed water pipe, which is connected to the boiler and the recirculation bypass; When the unit is running at low load or even ultra-low load, the water demand of the boiler decreases, and the feedwater pressure difference power generation stop valve controls the recirculation flow to be introduced into the high-pressure feedwater power generation turbine, and the pressure difference between high and low pressure is used to drive the turbine to generate electricity; The pressure sensor detects the deaerator water tank pressure in real time, feeds the pressure signal back to the control system, and adjusts the opening of the feedwater pressure difference power generation stop valve; The control system can automatically allocate two paths of recirculation flow according to the unit's operating load and economic targets, thereby improving the unit's energy efficiency.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention comprises a feedwater pressure differential power generation stop valve, a high-pressure feedwater power generation turbine, a small generator, and a pressure sensor, which are arranged in sequence. The inlet of the feedwater pressure differential power generation stop valve is connected to the outlet of the feedwater pump, the inlet of the high-pressure feedwater power generation turbine is connected to the outlet of the feedwater pressure differential power generation stop valve, and the outlet of the high-pressure feedwater power generation turbine is connected to the recirculation bypass inlet of the deaerator. The pressure sensor measures the pressure in the deaerator tank, and its signal is used to control the opening of the feedwater pressure differential power generation stop valve 4. By utilizing the pressure differential energy potential of the feedwater recirculation pipeline to generate electricity when the unit is operating at ultra-low load, the safety issues and energy loss caused by excessive feedwater recirculation pressure differential under ultra-low load conditions are resolved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural diagram of the present invention; Among them, 1. Deaerator; 2. Feed water pump; 3. Recirculation valve; 4. Feed water pressure difference power generation stop valve; 5. Feed water main pipe stop valve; 6. High-pressure feed water power generation turbine; 7. Generator; 8. Pressure sensor. DETAILED DESCRIPTION

[0020] In order to further understand the content of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the embodiments are only for explaining the present invention and are not intended to limit it.

[0021] See also Figure 1 A recirculating pressure difference power generation system suitable for ultra-low load operation of thermal power units includes a deaerator 1, the liquid outlet of the deaerator 1 is connected to the water supply main pipe, the water supply main pipe is connected to the deaerator 1 and the high-pressure water supply power generation turbine 6 through two bypasses, the outlet of the high-pressure water supply power generation turbine 6 is connected to the recirculation bypass inlet of the deaerator 1, and a water supply pressure difference power generation stop valve 4 is provided on the bypass connecting the water supply main pipe to the high-pressure water supply power generation turbine 6. A pressure sensor 8 is used to measure the water tank pressure of the deaerator 1, and its signal is used to control the opening of the water supply pressure difference power generation stop valve 4.

[0022] A feed water pump 2 is provided upstream of the main water pipe. A recirculation valve 3 is provided on the bypass connecting the main water pipe to the deaerator 1. The inlet of the feed water differential pressure power generation stop valve 4 is connected to the outlet of the feed water pump 2. The inlet of the high-pressure feed water power generation turbine 6 is connected to the outlet of the feed water differential pressure power generation stop valve 4. The feed water recirculation differential pressure power generation bypass is connected in parallel with the original feed water recirculation valve 3 of the unit. The flow rate of the feed water pump 2 is the sum of the flow rate of the recirculation valve 3, the flow rate of the feed water differential pressure power generation stop valve 4 and the flow rate of the main water pipe stop valve 5. The design pressure difference of the high-pressure feed water power generation turbine 6 is the feed water recirculation pressure difference when the unit is operating at 30% load. The pressure sensor 8 includes several pressure measurement points arranged in the water tank of the deaerator 1, and the signal value of the pressure sensor 8 is the average value of the detection values ​​of all measurement points.

[0023] See also Figure 1 A method for operating a recirculating pressure difference power generation system adapted to ultra-low load operation of a thermal power unit comprises the following steps: Step 1: The water supply pump 2 presses the deoxygenated water into the water supply main pipe, which is connected to the supply boiler and the recirculation bypass.

[0024] Step 2: When the unit is running at low load or even ultra-low load, the boiler water demand decreases, and the feed water pressure difference power generation stop valve 4 controls the recirculation flow to be introduced into the high-pressure feed water power generation turbine 6, and the pressure difference between high and low pressure is used to drive the turbine to generate electricity.

[0025] Step 3: The pressure sensor 8 detects the deaerator water tank pressure in real time, feeds the pressure signal back to the control system, and adjusts the opening of the feed water pressure difference power generation stop valve 4.

[0026] Step 4: The control system can automatically allocate the two paths of recirculation flow according to the unit's operating load and economic targets to improve the unit's energy efficiency.

[0027] Example 1: The present invention provides a recirculating pressure difference power generation system suitable for ultra-low load operation of thermal power generation units, comprising a feed water pressure difference power generation stop valve 4, a high-pressure feed water power generation turbine 6, a small generator 7 and a pressure sensor 8 arranged in sequence. The inlet of the feed water pressure difference power generation stop valve 4 is connected to the outlet of the feed water pump 2, the inlet of the high-pressure feed water power generation turbine 6 is connected to the outlet of the feed water pressure difference power generation stop valve 4, and the outlet of the high-pressure feed water power generation turbine 6 is connected to the recirculation bypass inlet of the deaerator 1. The pressure sensor 8 measures the water tank pressure of the deaerator 1, and its signal is used to control the opening of the feed water pressure difference power generation stop valve 4.

[0028] The purpose of connecting the feed water recirculation pressure difference power generation bypass in parallel with the original feed water recirculation valve 3 of the unit is to adjust the flow rate of the two bypasses according to different peak-shaving depth conditions, so as to achieve the optimal solution for ensuring the dynamic safety of the recirculating water and energy recovery and utilization.

[0029] The flow rate of feedwater pump 2 is the sum of the flow rate of recirculation valve 3, the flow rate of feedwater differential pressure power generation stop valve 4, and the flow rate of feedwater main pipe stop valve 5. By adjusting recirculation valve 3 and feedwater differential pressure power generation stop valve 4, the flow rate of feedwater pump 2 is ensured to meet the minimum flow requirement to prevent overheating and cavitation.

[0030] The high-pressure feedwater turbine 6 is designed to utilize the feedwater pressure differential to drive a small generator 7 to generate electricity. Its design pressure differential is the feedwater recirculation pressure differential when the unit is operating at 30% load. This design allows it to meet the unit's deep peak load conditions (30%-20% load), achieving better economic benefits.

[0031] The small generator 7 generates electricity to supply power to auxiliary equipment of the unit.

[0032] Pressure sensor 8 includes multiple pressure measurement points located within the deaerator 1 water tank. The signal value is the average of the values ​​detected at all these measurement points. The pressure sensor 8 measurement points are arranged in a circular array along the axis of the connection point to the deaerator 1 water tank. This design prevents fluctuations in measurement point data caused by water flow fluctuations within the deaerator 1 water tank, contributing to stable control of the feedwater pressure differential power generation shutoff valve 4.

[0033] The outlet of the water supply main pipe stop valve 5 is connected to the water supply main pipe to enter the unit circulation.

[0034] The present invention enables a thermal power unit to generate electricity by utilizing the pressure difference energy potential of a water supply recirculation pipeline when operating under ultra-low load conditions, thereby solving the safety problems and energy loss problems caused by excessive water supply recirculation pressure difference due to water supply recirculation under ultra-low load conditions.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A recirculating pressure difference power generation system adapted to ultra-low load operation of thermal power units, characterized in that: The invention comprises a deaerator (1), wherein the liquid outlet of the deaerator (1) is connected to a water supply main pipe, the water supply main pipe is connected to the deaerator (1) and a high-pressure water supply power generation turbine (6) through two bypasses, the outlet of the high-pressure water supply power generation turbine (6) is connected to the recirculation bypass inlet of the deaerator (1), a water supply pressure difference power generation stop valve (4) is provided on the bypass of the water supply main pipe connected to the high-pressure water supply power generation turbine (6), and a pressure sensor (8) is used to measure the pressure of the water tank of the deaerator (1), and the signal thereof is used to control the opening of the water supply pressure difference power generation stop valve (4).

2. A recirculating pressure difference power generation system adapted to ultra-low load operation of thermal power units according to claim 1, characterized in that: A water supply pump (2) is provided upstream of the water supply main pipe.

3. The recirculating pressure difference power generation system adapted to ultra-low load operation of thermal power units according to claim 1, characterized in that: A recirculation valve (3) is provided on a bypass connecting the water supply main pipe to the deaerator (1).

4. The recirculating pressure difference power generation system adapted to ultra-low load operation of thermal power units according to claim 1, characterized in that: The inlet of the water supply pressure difference power generation stop valve (4) is connected to the outlet of the water supply pump (2).

5. The recirculating pressure difference power generation system adapted to ultra-low load operation of thermal power units according to claim 1, characterized in that: The inlet of the high-pressure water-feeding power generation turbine (6) is connected to the outlet of the water-feeding pressure difference power generation stop valve (4).

6. The recirculating pressure difference power generation system adapted to ultra-low load operation of thermal power units according to claim 1, characterized in that: The feed water recirculation pressure difference power generation bypass is connected in parallel with the original feed water recirculation valve (3) of the unit.

7. The recirculating pressure difference power generation system adapted to ultra-low load operation of thermal power units according to claim 2, characterized in that: The flow rate of the water supply pump (2) is the sum of the flow rate of the recirculation valve (3), the flow rate of the water supply pressure difference power generation stop valve (4) and the flow rate of the water supply main pipe stop valve (5).

8. The recirculating pressure difference power generation system adapted to ultra-low load operation of thermal power units according to claim 1, characterized in that: The design pressure difference of the high-pressure feedwater power generation turbine (6) is the feedwater recirculation pressure difference when the unit is operating at 30% load.

9. The recirculating pressure difference power generation system adapted to ultra-low load operation of thermal power units according to claim 1, characterized in that: The pressure sensor (8) includes a plurality of pressure measuring points arranged in the water tank of the deaerator (1), and the signal value of the pressure sensor (8) is the average value of the detection values ​​of all the measuring points.

10. A method for operating a recirculating pressure difference power generation system adapted to ultra-low load operation of a thermal power unit according to any one of claims 1 to 9, characterized in that: The following steps are involved: The feed water pump (2) presses the deoxygenated feed water into the feed water main pipe, which is connected to the boiler and the recirculation bypass; When the unit is running at low load or even ultra-low load, the boiler water demand decreases, and the feed water pressure difference power generation stop valve (4) controls the recirculation flow to be introduced into the high-pressure feed water power generation turbine (6), and the pressure difference between high and low pressure is used to drive the turbine to generate electricity; The pressure sensor (8) detects the deaerator water tank pressure in real time, feeds the pressure signal back to the control system, and adjusts the opening of the feed water pressure difference power generation stop valve (4); The control system can automatically allocate two paths of recirculation flow according to the unit's operating load and economic targets, thereby improving the unit's energy efficiency.

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