A method for rapid load response based on small bypass regulation of high-pressure heater feedwater under deep peak regulation

Abstract

The present invention discloses a method for rapid load response based on a small bypass regulation of high-pressure heater feedwater under deep peak regulation. The feedwater bypass regulation function is realized by adding a small flow regulation bypass on the basis of the original high-pressure heater bypass. When the unit needs to increase the load, the feedwater flow through the high-pressure heater is reduced, thereby reducing the extraction steam flow of the high-pressure heater. The reduced part of the extraction steam returns to the steam turbine to do work, thereby increasing the load. Conversely, when the unit needs to reduce the load, the high-pressure heater bypass feedwater flow is actively reduced, the heat recovery extraction steam flow of the high-pressure heater is increased, and the steam flow doing work in the steam turbine is reduced to reduce the load. By adopting this method, the stability of the unit when the unit increases or decreases the load can be greatly improved, the rapid response rate of the unit load can be improved, and the safety of the unit operation under deep peak regulation can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep peak regulation of thermal power generating sets, and in particular relates to a method for rapid load response based on small bypass regulation of feed water of a high-pressure heater under deep peak regulation. Background Art

[0002] In recent years, the installed capacity of renewable energy such as wind power and photovoltaic power generation in my country has grown rapidly. However, the current regulation capacity of my country's power system is difficult to meet the needs of large-scale development and complete absorption of these clean energy sources, which has led to serious wind and solar abandonment in some areas. To this end, the state has issued a series of relevant documents and policies, requiring further exploration of the peak-shaving potential of coal-fired units, improving the flexibility of thermal power operation in my country, and comprehensively improving the peak-shaving and new energy absorption capabilities of the system. The pure condensing unit increases the peak-shaving capacity of 15% to 20% of the rated capacity, and the minimum technical output reaches 30% to 35% of the rated capacity. While the unit has the ability to deeply regulate the peak, it should be able to ensure the technical requirements of the variable load rate ≥1.5 to 2% Pe / min during the low load period.

[0003] However, at present, the design, commissioning and optimization of the control system of conventional thermal power units are usually only for the load range above 50% of the rated load, and rarely involve low-load operating conditions. When the unit is operating at ultra-low load, the control object characteristics of the unit have changed significantly, the main operating parameters and equipment are close to the lower limit of the normal adjustment range, the adjustment and safety margins are small, and there are generally problems such as poor adjustment quality of the coordinated control system, slow AGC response speed, poor primary frequency regulation performance, and unstable combustion.

[0004] Due to the limitations of the characteristics of the boiler and steam turbine itself, it is difficult to further improve the load response rate and load change rate of the unit. The existing unit load change mainly relies on short-term boiler heat storage to support the rapid increase of steam turbine flow and power, and the effect of increasing boiler fuel generally takes about a few minutes to fully manifest. The nature of this process determines that rapid load increase and decrease must conflict with boiler heat storage, throttling losses and the stability of steam temperature and pressure. In order to meet the requirements of new energy consumption for rapid load change capability, there are often large valve throttling losses during the actual operation of the unit, which leads to poor stability of the unit's steam temperature and pressure control parameters, and long-term operation brings greater safety risks and economic losses. Especially under deep peak-shaving operation conditions, the unit's operating condition point is close to the stability boundary, and the load increase and decrease has a greater impact on the stability of the unit. It is of great significance to use advanced auxiliary means to improve the unit's load increase and decrease capacity.

[0005] Due to the influence of factors such as the large delay of the unit load response rate, there is a delay of about several minutes from the issuance of the boiler load increase command to the actual increase of the boiler heat load to the given value, which makes it difficult to further improve the unit load response rate. Therefore, it is necessary to take necessary auxiliary measures to improve the unit's variable load capacity. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a load rapid response method based on small bypass regulation of high-pressure heater feed water under deep peak regulation.

[0007] In order to achieve the above purpose, the present invention adopts the following technical scheme:

[0008] In order to realize the water supply bypass regulation function, it is considered to add a small flow regulation bypass on the basis of the original high-pressure bypass.

[0009] Frequent operation of the high-pressure bypass valve can easily cause leakage of the high-pressure bypass valve. In order to avoid leakage of the high-pressure bypass valve and affect the economy of the unit during normal operation, a new flow regulation small bypass is added on the basis of the original high-pressure bypass, that is, a flow control small bypass is added in front of the original high-pressure bypass valve, and a pneumatic regulating valve, an electric isolation valve, a manual isolation valve and a flow nozzle are respectively set in the newly added flow control bypass, and a pneumatic regulating valve is added in the pipeline of the water supply main circuit. The pneumatic regulating valve is used for precise control and regulation of the water supply bypass flow, the electric isolation valve plays a role of isolation when the water supply bypass is closed, the manual isolation valve is set to prevent leakage caused by the electric valve not closing tightly after long-term operation, and the flow nozzle is set for online monitoring of the bypass water supply flow in the water supply bypass. The material of all valves can be selected as 20G, the valve size must match the size of the pipe, and the connection method is flange or welding.

[0010] During normal operation, the regulating valve on the main feedwater line is fully open, and the isolation valve and regulating valve on the feedwater regulation bypass are fully closed. When the high-pressure bypass is required to participate in load regulation, first open the isolation valve and regulating valve on the flow regulation bypass, and adjust the bypass feedwater flow by adjusting the opening of the regulating valve on the bypass. If the bypass feedwater flow needs to be further increased after the flow adjustment bypass regulating valve is fully opened, the bypass feedwater flow can be increased by closing the newly added regulating valve on the main feedwater line. When the unit needs to increase the load, the feedwater flow through the high-pressure heater is reduced, thereby reducing the extraction steam flow of the high-pressure heater. The reduced part of the extraction steam returns to the turbine to do work, thereby achieving load increase. Conversely, when the unit needs to reduce the load, the high-pressure bypass feedwater flow is actively reduced, the heat recovery extraction steam flow of the high-pressure heater is increased, and the steam flow doing work in the turbine is reduced to achieve load reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1It is a schematic diagram of the system structure of the present invention.

[0012] Among them, 1. High-pressure heater No. 1, 2. High-pressure heater No. 2, 3. High-pressure heater No. 3, 4. Water feed pump, 5. Electric isolation valve, 6. High-pressure bypass valve, 7. Pneumatic regulating valve, 8. Pneumatic regulating valve, 9. Electric isolation valve, 10. Manual isolation valve, 11. Flow nozzle. DETAILED DESCRIPTION

[0013] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Note that the following embodiments are merely illustrative in nature, and the present invention is not intended to limit its applicable objects or uses, and the present invention is not limited to the following embodiments.

[0014] Example

[0015] The 660MW supercritical boiler of a power plant is taken as the object. A small flow control bypass is added in front of the original high-pressure bypass valve 6, and a pneumatic regulating valve 8, an electric isolation valve 9, a manual isolation valve 10 and a flow nozzle 11 are respectively set in the newly added flow control bypass, and a pneumatic regulating valve 7 is added to the pipeline of the water supply main circuit. The pneumatic regulating valve 8 is used for precise control and regulation of the water supply bypass flow, the electric isolation valve 9 plays a role of isolation when the water supply bypass is closed, the manual isolation valve 10 is set to prevent leakage caused by the electric valve not closing tightly after long-term operation, and the flow nozzle 11 is set for online monitoring of the bypass water supply flow in the water supply bypass. The material of all valves can be selected as 20G, the valve size must match the size of the pipe, and the connection method is flange or welding.

[0016] During normal operation, the regulating valve on the main water supply line is fully open, and the isolation valve and regulating valve on the water supply regulation bypass are fully closed. When the high-pressure bypass is needed to participate in load regulation, first open the isolation valve and regulating valve on the flow regulation bypass, and adjust the bypass water supply flow by adjusting the opening of the regulating valve on the bypass. If the bypass water supply flow needs to be further increased after the flow adjustment bypass regulating valve is fully opened, the newly added regulating valve 7 on the main water supply line can be closed to increase the bypass water supply flow.

[0017] When the unit needs to increase its load, the feed water flow through the high-pressure heater is reduced, thereby reducing the extraction steam flow of the high-pressure heater. The reduced extraction steam returns to the steam turbine to perform work, thereby increasing the load.

[0018] When the unit needs to reduce load, the bypass feed water flow of the high-pressure heater is actively reduced, the heat recovery steam flow of the high-pressure heater is increased, and the steam flow doing work in the turbine is reduced to achieve load reduction.

[0019] Under 25% THA conditions, the influence of bypass feed water flow on the variable load capacity of the unit was calculated. According to the calculation results, for every 100t / h increase in bypass feed water flow, the unit's power generation capacity can be increased by about 4.67MW and the feed water temperature can be reduced by about 23.59℃; when the bypass feed water flow reaches 100% capacity, i.e. 630t / h, the power generation capacity can be increased by 29.42MW and the feed water temperature can be reduced by 79℃.

[0020] In summary, under 25% THA conditions, when the bypass water flow reaches 100% capacity, the power generation capacity can be increased by 29.42MW, which is equivalent to advancing the load response time by about 2.7 minutes.

[0021] The above embodiments are merely examples and do not limit the scope of the present invention. These embodiments can also be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the technical concept of the present invention.

Claims

1. A method for rapid load response based on small bypass regulation of high-pressure heater feedwater under deep peak regulation, characterized in that: The water supply bypass regulation function is achieved by adding a flow regulating small bypass on the basis of the original high-pressure bypass.

2. The method for rapid load response based on small bypass regulation of high-pressure heater feedwater under deep peak regulation according to claim 1 is characterized in that: A small flow control bypass is added in front of the original high-pressure bypass valve, and a pneumatic regulating valve, an electric isolation valve, a manual isolation valve and a flow nozzle are respectively arranged in the newly added flow control bypass, and a pneumatic regulating valve is added in the pipeline of the water supply main circuit.

3. The method for rapid load response based on small bypass regulation of high-pressure heater feedwater under deep peak regulation according to claim 2 is characterized in that: The material of all valves can be 20G, the valve size must match the pipe size, and the connection method is flange or welding.

4. The method for rapid load response based on small bypass regulation of high-pressure heater feedwater under deep peak regulation according to claim 2 is characterized in that: During normal operation, the regulating valve on the main water supply line is fully open, and the isolation valve and regulating valve on the water supply regulation bypass line are fully closed.

5. The method for rapid load response based on small bypass regulation of high-pressure heater feedwater under deep peak regulation according to claim 2, characterized in that: When the high-pressure bypass is needed to participate in load regulation, first open the isolation valve and regulating valve on the flow regulation bypass, and adjust the bypass water supply flow by adjusting the opening of the regulating valve on the flow regulation bypass. If the bypass water supply flow needs to be further increased after the flow regulation bypass regulating valve is fully opened, the bypass water supply flow can be increased by closing the newly added regulating valve on the main water supply line.

6. The method for rapid load response based on small bypass regulation of high-pressure heater feedwater under deep peak regulation according to claim 2, characterized in that: When the unit needs to increase the load, the feed water flow through the high-pressure heater is reduced, thereby reducing the extraction steam flow of the high-pressure heater. The reduced extraction steam returns to the turbine to do work, thereby increasing the load. Conversely, when the unit needs to reduce the load, the bypass feed water flow of the high-pressure heater is actively reduced, the heat recovery extraction steam flow of the high-pressure heater is increased, and the steam flow doing work in the turbine is reduced, thereby reducing the load.

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