Flexible operation system for coal power unit to adapt to deep peak regulation

Abstract

The invention discloses a flexible operation system for a coal power unit to adapt to deep peak regulation, which is characterized in that a supercharging module is connected in a steam inlet pipeline between a high-pressure cylinder and an existing final-stage high-pressure heater, the supercharging module is provided with supercharging equipment, and steam lower than a target steam extraction pressure grade is introduced into an inlet of the supercharging module; an outlet of the pressurization module is connected into an existing final-stage high-pressure heating steam inlet pipeline, the outlet of the pressurization module is located on the downstream portion of a steam extraction isolation valve, and steam lower than the target steam extraction pressure grade enters an existing final-stage high-pressure heater to heat feed water after being pressurized through pressurization equipment, so that the in-furnace feed water temperature of a unit under the deep peak regulation working condition is increased; the water temperature of an inlet and an outlet of the economizer and the smoke temperature of the outlet of the economizer are increased, the enthalpy of an inlet of a water cooling wall is reduced, a hot water section in the water cooling wall is shortened, the superheat degree of steam at the outlet of the water cooling wall is kept, and boiler dry-state operation, hydrodynamic stability and continuous and stable operation of a denitration system of a unit under the deep peak regulation working condition are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation, and in particular to a flexible operation system of a coal-fired power unit adapted to deep peak regulation. Background Art

[0002] At present, high-parameter, large-capacity, high-efficiency and low-carbon ultra-supercritical units have become the mainstream of new unit selection in thermal power plants. For ultra-supercritical units, their capacities are mainly 350MW, 660MW, and 1000MW, and there are also a small number of 1200MW and 1350MW.

[0003] New energy installed capacity and power generation have reached new highs. Due to the uncertainty of power generation due to new energy power generation methods, traditional thermal power units, especially coal-fired power units, must assume the role of basic power supply and flexible peak-shaving power supply to cooperate with new energy power generation.

[0004] Taking a 1000MW supercritical unit as an example, the load range of the regional power grid dispatching is 40%-100% THA. The feed water flow of the boiler equipment corresponding to the load of the unit is higher than the minimum flow for the boiler to maintain dry operation. Therefore, within the current normal load dispatching range, the boiler always maintains dry operation without dry-wet state conversion process. However, with the rapid development of new energy, the unit needs to operate in deep peak load regulation, and the lower limit of load dispatching needs to be as low as 20%. The feed water flow of the boiler equipment corresponding to the 20% load of the unit is already lower than the minimum flow for the boiler to maintain dry operation, and the boiler will have to switch to wet operation. Therefore, the unit operation faces many problems. For example, under deep peak-shaving conditions, the boiler frequently switches between dry and wet states, and the control of coal, water and air is very difficult, which increases the risk of boiler shutdown sharply. Under deep peak-shaving conditions, due to the increase in the water-wall inlet feed water enthalpy, the hydrodynamic stability of the boiler water-cooled wall is poor, and the risk of water-cooled wall overheating and tube burst increases sharply. Under deep peak-shaving conditions, the flue gas temperature at the economizer outlet will be lower than the lower limit of the normal operation temperature of the conventional denitrification catalyst (such as 300°C), and the denitrification system will not be able to operate normally. It is foreseeable that NO X Emissions will increase dramatically and far exceed the standard requirements (such as emission indicators from 25mg / Nm 3 Exploded to 200mg / Nm 3 Above, far exceeding the standard value of 50mg / Nm 3 ); Under the boiler wet operation condition, if the water separated from the steam-water separator at the boiler water wall outlet is directly discharged to the atmospheric expansion tank, a large amount of working fluid and its energy will be lost, the unit energy consumption will increase significantly, and the operation economy will decrease significantly. Therefore, how to maintain the boiler dry operation under deep peak load conditions, maintain the hydrodynamic stability, and the continuous and stable operation of the denitrification system has become an urgent problem to be solved. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to maintain the dry operation of the boiler under deep peak regulation conditions, and maintain the hydrodynamic stability and continuous and stable operation of the denitrification system, so as to provide a flexible operation system for coal-fired power units that can adapt to deep peak regulation.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] The present invention provides a flexible operation system of a coal-fired power unit that is adaptable to deep peak regulation. The system comprises a deaerator, a pre-pump, a feed water pump, an existing final-stage high-pressure heater, a boiler, a main steam throttling assembly, a high-pressure cylinder, and a steam extraction isolation valve. The low-pressure condensate at the outlet of the deaerator is pressurized by the pre-pump and the feed water pump in turn and then enters the existing final-stage high-pressure heater for heating. The heated feed water enters the boiler and is heated by the economizer, the water-cooled wall, and the heating surface of the superheater in turn, and finally the main steam is obtained and enters the high-pressure cylinder to perform work. The final-stage extraction steam of the high-pressure cylinder enters the existing final-stage high-pressure heater through a steam inlet pipe; a high-pressure cylinder steam inlet valve group is arranged on the high-pressure cylinder steam inlet pipe; the steam extraction isolation valve is arranged on the steam inlet pipe of the existing final-stage high-pressure heater;

[0008] A boosting module is connected to the steam inlet pipeline between the high-pressure cylinder and the existing final-stage high-pressure heater. A boosting device is arranged in the pipeline of the boosting module. The inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level. The outlet of the boosting module is connected to the steam inlet pipeline of the existing final-stage high-pressure heater and is located downstream of the extraction isolation valve. The steam entering the boosting module is pressurized by the boosting device and then enters the existing final-stage high-pressure heater to increase the feed water temperature of the unit under deep peak-shaving conditions.

[0009] In this scheme, a boosting module is connected to the steam inlet pipeline between the high-pressure cylinder and the existing final-stage high-pressure heater, and a boosting device is arranged in the pipeline of the boosting module, the inlet of the boosting module is connected to the steam with a pressure lower than the target extraction pressure level, and the outlet of the boosting module is connected to the steam inlet pipeline of the existing final-stage high-pressure heater, and the outlet of the boosting module is located downstream of the extraction isolation valve. When the boosting device pressurizes the steam entering the existing final-stage high-pressure heater, the extraction isolation valve is in a closed state upstream; the steam entering the boosting module with a pressure lower than the target extraction pressure level is pressurized by the boosting device and then enters the existing final-stage high-pressure heater to heat the feed water, so as to increase the feed water temperature entering the furnace of the unit under deep peak regulation conditions, thereby increasing the economizer inlet water temperature, the economizer outlet water temperature, the economizer outlet flue gas temperature, and the water-cooled wall inlet under-enthalpy. , shorten the hot water section in the water-cooled wall and maintain a certain degree of superheat of the steam at the outlet of the water-cooled wall, and finally realize the dry operation of the boiler under the deep peak-shaving condition of the unit, maintain the hydrodynamic stability, and continuously and stably put the denitrification system into operation; by introducing steam below the target extraction pressure level and pressurizing it through the booster equipment, it enters the existing final-stage high-pressure heater to heat the feed water. Compared with the scheme of replacing the steam inlet of the final-stage high-pressure heater with the main steam after cooling and reducing the pressure, it can save the use of high-temperature and high-pressure pipelines, and avoid the negative safety effects caused by the instantaneous change of the heat absorption ratio of the main and re-steam due to the use of the main steam. In addition, the extraction steam below the target extraction pressure level adopted in the present invention has better thermal economy than the main steam that does not do work in the turbine. Therefore, this scheme has the advantages of relative safety, low cost, high flexibility in operation adjustment, and good economy.

[0010] Preferably, the boosting device is a steam compressor.

[0011] In this scheme, steam below the target extraction pressure level is pressurized and heated by a steam compressor and then enters the existing final-stage high-pressure heater to heat the feed water, thereby increasing the unit's furnace feed water temperature under deep peak regulation conditions.

[0012] Preferably, a heat exchanger is added downstream of the steam compressor, and the steam below the target extraction pressure level is pressurized by the steam compressor, and then heat-exchanged by the heat exchanger before entering the existing final high pressure level;

[0013] And / or, a heat exchanger is added upstream of the steam compressor, and steam with a pressure level lower than the target extraction pressure first enters the heat exchanger for heat exchange and then enters the steam compressor.

[0014] In this scheme, a heat exchanger is added downstream of the steam compressor; steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor, enters the heat exchanger to heat other working fluids such as wind, water, coal, etc., and then enters the existing final stage high pressure heater to heat the feed water, thereby reducing the steam temperature entering the existing final stage high pressure heater and relatively increasing the steam inlet flow rate of the existing final stage high pressure heater;

[0015] A heat exchanger is added upstream of the steam compressor. Steam with a pressure lower than the target extraction pressure level enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then increases the pressure through the steam compressor before entering the existing final-stage high-pressure heater to heat the feed water. This can reduce the temperature of the steam entering the steam compressor and relatively increase the steam inlet flow rate of the existing final-stage high-pressure heater.

[0016] Preferably, a heat exchanger is added downstream of the steam compressor and is located on the steam inlet pipeline of the existing final stage high pressure heating or on the pipeline of the boosting module;

[0017] And / or, a heat exchanger is added upstream of the steam compressor and is located on the steam inlet pipeline of the existing final stage high-pressure heating or on the pipeline of the boosting module.

[0018] In this solution, the heat exchanger located downstream of the steam compressor and / or the heat exchanger located upstream of the steam compressor can be arranged on the existing final stage high-pressure heating steam inlet pipeline or on the pipeline of the boosting module.

[0019] Preferably, the steam at a pressure level lower than the target extraction pressure level connected to the inlet of the boosting module is the final extraction steam of the high-pressure cylinder of the unit, and the inlet of the boosting module is connected to the existing final high-pressure heated steam inlet pipeline and is located upstream of the extraction isolation valve.

[0020] In the present scheme, the steam connected to the inlet of the boosting module at a pressure level lower than the target extraction pressure level is the final extraction steam of the high-pressure cylinder of the unit, that is, for the existing final high-pressure heater and extraction steam of the unit, the final extraction steam is pressurized by a steam compressor, and then enters the existing final high-pressure heater to heat the feed water. The inlet of the boosting module is connected to the steam inlet pipeline of the existing final high-pressure heater and is located upstream of the extraction steam isolation valve. Upstream of the extraction steam isolation valve, it is connected to the inlet of the boosting module, and the extraction steam isolation valve is closed. The final extraction steam of the high-pressure cylinder can enter the boosting module, and after being pressurized, it enters the existing final high-pressure heater to heat the feed water.

[0021] Preferably, a new steam extraction isolation valve is provided in the existing final-stage high-pressure heater steam inlet pipeline, and the new steam extraction isolation valve is located upstream of the heat exchanger upstream of the steam compressor.

[0022] In the present scheme, a new steam extraction isolation valve is provided in the existing final-stage high-pressure heater steam inlet pipe, and the new steam extraction isolation valve is located upstream of the heat exchanger upstream of the steam compressor. That is, when the steam with a pressure level lower than the target steam extraction pressure level connected to the inlet of the boosting module is the final-stage steam extraction of the high-pressure cylinder of the unit, a new steam extraction isolation valve is provided at the front end of the heat exchanger upstream of the steam compressor, so that when the heat exchanger and other equipment fails, the final-stage exhaust steam of the high-pressure cylinder can be disconnected by closing the new steam extraction isolation valve, thereby ensuring the safety of system operation and improving the flexibility of system operation.

[0023] Preferably, the steam having a pressure level lower than the target extraction pressure level is heat recovery extraction steam in the unit or other units, or steam in a reheat system or steam in a superheater system.

[0024] In this scheme, steam below the target extraction pressure level is optimized to heat recovery extraction steam in this unit or other units, steam in the reheat system, or steam in the superheater system. On the premise that the steam pressure at the outlet of the steam compressor is higher than the existing last-stage extraction steam, the operating flexibility of the unit is improved.

[0025] Preferably, the main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.

[0026] In this scheme, the main steam throttling component adopts a high-pressure cylinder steam inlet regulating valve group or a regulating valve to facilitate the adjustment of the pressure and flow of the main steam.

[0027] Preferably, the flexible operation system is configured to throttle the main steam using a main steam throttling assembly to maintain a certain feed water pressure and to keep the economizer outlet feed water at a certain degree of subcooling.

[0028] In this scheme, when the steam entering the existing final-stage high-pressure heater is pressurized by the booster module to increase the furnace feed water temperature of the unit under deep peak-shaving conditions, the high-pressure cylinder steam inlet valve group is operated and the original high-pressure cylinder steam inlet valve group is used to throttle the main steam. The purpose is to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling, prevent vaporization from occurring while increasing the furnace feed water temperature, and ensure the normal operation of the unit.

[0029] Preferably, a throttling component is provided in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

[0030] In this scheme, a throttling component, such as a regulating valve, may also be provided in the feed water or steam piping system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

[0031] The positive and progressive effect of the present invention is that a boosting module is connected to the steam inlet pipeline between the high-pressure cylinder and the existing final-stage high-pressure heater, and a boosting device is arranged in the pipeline of the boosting module, the inlet of the boosting module is connected to the steam with a pressure lower than the target extraction pressure level, and the outlet of the boosting module is connected to the steam inlet pipeline of the existing final-stage high-pressure heater, and the outlet of the boosting module is located downstream of the extraction isolation valve, so that the steam with a pressure lower than the target extraction pressure level entering the boosting module is pressurized by the boosting device and then enters the existing final-stage high-pressure heater to heat the feed water, so as to increase the furnace feed water temperature of the unit under deep peak regulation conditions, thereby increasing the economizer inlet water temperature, the economizer outlet water temperature, the economizer outlet flue gas temperature, and the water-cooled wall The inlet enthalpy is insufficient, the hot water section in the water-cooled wall is shortened, and the steam at the water-cooled wall outlet is kept at a certain superheat, ultimately achieving dry operation of the boiler under deep peak-shaving conditions, maintaining hydrodynamic stability, and continuously and stably putting the denitrification system into operation; compared with the scheme of replacing the steam inlet of the final-stage high-pressure heater with the main steam after cooling and reducing the pressure, it can save the use of high-temperature and high-pressure pipelines, and avoid the negative safety impact caused by the instantaneous change of the main and re-steam heat absorption ratio due to the use of the main steam. In addition, the extraction steam used in the present invention is lower than the target extraction pressure level, and its thermal economy is better than the main steam that does not do work in the turbine. Therefore, this scheme has the advantages of relative safety, low cost, high flexibility in operation adjustment, and good economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a schematic diagram of a system for heating boiler feed water in the prior art.

[0033] Figure 2 This is a schematic diagram of a flexible operation system for coal-fired power units adapted to deep peak regulation in a preferred embodiment of the present invention (I).

[0034] Figure 3 This is a schematic diagram of a flexible operation system for coal-fired power units adapted to deep peak regulation in a preferred embodiment of the present invention (II).

[0035] Figure 4 This is a schematic diagram of a flexible operation system for coal-fired power units adapted to deep peak regulation in a preferred embodiment of the present invention (III).

[0036] Figure 5 This is a schematic diagram of a flexible operation system for coal-fired power units adapted to deep peak regulation in a preferred embodiment of the present invention (IV).

[0037] Figure 6 This is a schematic diagram of a flexible operation system for coal-fired power units adapted to deep peak regulation in a preferred embodiment of the present invention (V).

[0038] Figure 7 This is a schematic diagram of a flexible operation system for coal-fired power units adapted to deep peak regulation in a preferred embodiment of the present invention (VI).

[0039] Figure 8 This is a schematic diagram of a flexible operation system for coal-fired power units adapted to deep peak regulation in a preferred embodiment of the present invention (VII). DETAILED DESCRIPTION

[0040] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0041] like Figure 1 This is a schematic diagram of the existing boiler feed water heating system. The system includes a deaerator, a pre-pump, a feed water pump, an existing final high-pressure heater, a boiler, a high-pressure cylinder steam inlet valve group, a high-pressure cylinder, and a steam extraction isolation valve, which are arranged in sequence. The boiler includes an economizer, a water-cooled wall, a superheater, etc. The above parts are connected by pipelines. The high-pressure cylinder steam inlet valve group is arranged on the high-pressure cylinder steam inlet pipeline, and the high-pressure cylinder steam inlet valve group can adjust the pressure and flow of the main steam. The steam extraction isolation valve is arranged on the high-pressure cylinder steam inlet pipeline. The steam inlet source of the existing final high-pressure heater is the final stage steam extraction of the high-pressure cylinder.

[0042] When the system is in operation: the low-pressure condensate passes through the deaerator, pre-pump, and feed water pump in turn, and then enters the existing high-pressure heater for heating. The heated feed water enters the boiler and is heated by the economizer, water-cooled wall, superheater and other heating surfaces in turn, and finally the main steam is obtained and enters the high-pressure cylinder to do work.

[0043] In order to solve the above technical problems, the present invention, based on the existing boiler feed water heating system, connects a boosting module in the steam inlet pipeline between the high-pressure cylinder and the existing final-stage high-pressure heater, and arranges a boosting device in the pipeline of the boosting module. The outlet of the boosting module is connected to the existing final-stage high-pressure heating steam inlet pipeline and is located downstream of the extraction isolation valve. Steam with a pressure level lower than the target extraction pressure level is introduced into the boosting module, and the steam is pressurized by the boosting device and then enters the existing final-stage high-pressure heater to heat the feed water, so as to increase the feed water temperature of the unit under deep peak regulation conditions, thereby increasing the economizer inlet water temperature, the economizer outlet water temperature, the economizer outlet flue gas temperature, the water wall inlet under-enthalpy, and the shortening of the hot water section in the water-cooled wall. At the same time, the high-pressure cylinder steam inlet valve group is used to throttle the main steam to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling. Among them, steam of the target extraction pressure level can be understood as steam that directly enters the existing final-stage high-pressure heater to heat the feed water to the required temperature if the boiler feed water heating system in the prior art is adopted, that is, the boosting module is not set to heat the steam; the extraction pressure level lower than the target extraction pressure level can be the final-stage extraction steam of the high-pressure cylinder of this unit, or other heat recovery extraction steam or superheater system steam or reheat system steam of this unit, or heat recovery extraction steam or superheat system steam or reheat system steam of other units, or a mixture of the aforementioned steam and other relatively low-pressure steam (such as unit heat recovery extraction steam, reheat steam, etc.).

[0044] Compared with the scheme of replacing the steam inlet of the final-stage high-pressure heater with the main steam after cooling and reducing the pressure, the present invention can save the use of high-temperature and high-pressure pipelines, avoid the negative safety impact caused by the instantaneous change of the heat absorption ratio of the main steam and the re-steam due to the use of the main steam, and the extraction steam used by the present invention is lower than the target extraction pressure level, and its thermal economy is better than the main steam that does not do work in the turbine. Therefore, this scheme has the advantages of relative safety, low cost, high flexibility in operation and regulation, and good economy.

[0045] Example 1

[0046] Figure 2 Shown is a schematic diagram of the flexible operation system of the coal-fired power unit of the present invention that adapts to deep peak regulation.

[0047] The present invention is based on the existing boiler feed water heating system, connects a boosting module in the steam inlet pipeline between the high-pressure cylinder and the existing final-stage high-pressure heater, and arranges a boosting device in the pipeline of the boosting module, the outlet of the boosting module is connected to the existing final-stage high-pressure heating steam inlet pipeline and is located downstream of the extraction isolation valve, by introducing steam with a pressure lower than the target extraction pressure level into the boosting module, the steam is pressurized by the boosting device and then enters the existing final-stage high-pressure heater to heat the feed water. In this embodiment, the source of the steam introduced with a pressure lower than the target extraction pressure level is the final-stage extraction steam of the high-pressure cylinder of the unit, the inlet of the boosting module is connected to the existing final-stage high-pressure heating steam inlet pipeline and is located upstream of the extraction isolation valve, that is, a boosting device is arranged in parallel between the inlet and outlet of the extraction isolation valve of the steam inlet pipeline of the existing final-stage high-pressure heater, and the boosting device uses a steam compressor, the final-stage extraction steam of the high-pressure cylinder is pressurized and then enters the existing final-stage high-pressure heater to heat the feed water, so as to improve the unit's feed water temperature under deep peak regulation conditions.

[0048] Compared with the scheme of replacing the steam inlet of the final stage high-pressure heater with the main steam after cooling and reducing the pressure, this scheme can save the use of high-temperature and high-pressure pipelines, avoid the negative safety impact caused by the instantaneous change of the heat absorption ratio of the main steam and re-steam due to the use of the main steam, and the final stage extraction steam of this scheme has already done work in the steam turbine, and its thermal economy is better than that of the main steam that has not done work in the steam turbine. Therefore, this scheme has the advantages of relative safety, low cost, high flexibility in operation and regulation, and good economy.

[0049] For this system, when the unit is operating at partial load, the low-pressure condensate at the outlet of the deaerator is pressurized by the pre-pump and the feed water pump in turn and then enters the existing high-pressure heater for heating. The heated feed water enters the boiler and is heated by the economizer, water-cooled wall, superheater and other heating surfaces in turn, and finally the main steam is obtained and enters the high-pressure cylinder to do work. The extraction steam isolation valve on the existing final-stage high-pressure heater steam inlet pipe is in a closed state, and the final-stage extraction steam of the high-pressure cylinder enters the boosting module. After the steam compressor pressurizes the final-stage extraction steam, it enters the existing final-stage high-pressure heater to heat the feed water, so as to increase the unit's inlet water temperature under deep peak regulation conditions.

[0050] The main steam throttling assembly is arranged on the high-pressure cylinder steam inlet pipe. Figure 2 The main steam throttling component is a high-pressure cylinder steam inlet valve group. Of course, a regulating valve can also be selected. The high-pressure cylinder steam inlet valve group adjusts the pressure and flow of the main steam.

[0051] It should be emphasized here that after the booster module is introduced to pressurize the final stage extraction steam and then enter the existing final stage high-pressure heater to heat the feed water to increase the unit's furnace feed water temperature under deep peak regulation conditions, the original high-pressure cylinder steam inlet valve group is used to throttle the main steam by operating the high-pressure cylinder steam inlet valve group to maintain a certain feed water pressure, so that the economizer outlet feed water maintains a certain degree of subcooling, so as to increase the unit's furnace feed water temperature under deep peak regulation conditions, thereby increasing the economizer inlet water temperature, economizer outlet water temperature, economizer outlet flue gas temperature, reduce the water wall inlet enthalpy, shorten the hot water section in the water wall and maintain a certain degree of superheat of the water wall outlet steam, while increasing the furnace feed water temperature. Prevent the feed water from vaporizing, etc., and ultimately achieve dry operation of the boiler under deep peak regulation conditions, maintain hydrodynamic stability, and continuously and stably put the denitrification system into operation. It should be noted that a throttling component, such as a regulating valve, may be provided in the feed water or steam piping system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

[0052] In this way, under the deep peak load regulation condition, taking the 20% THA condition as an example:

[0053] The unit's feed water temperature can be increased to 75% THA or even 100% THA.

[0054] As the feed water temperature of the unit increases, the economizer inlet water temperature increases, and then the economizer outlet water temperature increases, and the economizer outlet flue gas temperature increases and meets the denitrification inlet flue gas temperature requirement. While the economizer outlet water temperature increases, a certain feed water pressure is maintained so that the economizer outlet feed water maintains a certain degree of subcooling. As the economizer outlet water temperature increases, the water wall inlet water temperature increases, thereby reducing the water wall inlet enthalpy and enhancing the hydrodynamic stability. As the water wall inlet water temperature increases, the water wall outlet steam can maintain a certain degree of superheat, that is, the boiler dry operation is achieved.

[0055] Example 2

[0056] like Figure 3 The figure shows a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment to adapt to deep peak regulation. On the basis of embodiment 1, a heat exchanger is added downstream of the steam compressor, and the steam below the target extraction pressure level is pressurized by the steam compressor, and then heat-exchanged by the heat exchanger before entering the existing final high pressure; Figure 3 The middle heat exchanger is located on the steam inlet pipeline of the existing final stage high-pressure heating. Of course, the heat exchanger can also be set on the pipeline of the boosting module, as long as it meets the requirement of heat exchange for the steam pressurized by the steam compressor before entering the existing final stage high-pressure heater. After the final stage extraction steam is pressurized by the steam compressor, it can enter the heat exchanger to heat other working media, such as wind, water, coal, etc., and then enter the existing final stage high-pressure heater to heat the feed water. In this way, the steam temperature entering the existing final stage high-pressure heater can be reduced and the steam inlet flow rate of the existing final stage high-pressure heater can be relatively increased.

[0057] Take the data of 20% THA condition of a 1000MW unit as an example.

[0058] Existing solution: main generator load is 200MW, the existing final stage high-pressure heater inlet steam parameters are 1.75MPa, 436℃ and outlet feed water parameters are 6MPa, 192℃, economizer outlet water temperature is 240℃ (subcooling 36℃, under-enthalpy 176kJ / kg), economizer outlet flue gas temperature is 245℃, the water-cooled wall outlet is wet saturated steam, the unit is in wet operation state, and the denitrification system cannot be put into use.

[0059] This patent solution: the main generator load is 200MW, the existing final stage extraction parameters are 1.01MPa, 339℃, the existing final stage high-pressure heater inlet steam parameters after being pressurized by the steam compressor and cooled by the heat exchanger are 6.2MPa, 390℃ and the outlet feed water parameters are 11.9MPa, 279℃, the economizer outlet water temperature is 306℃ (subcooling 18℃, under-enthalpy 112kJ / kg), the economizer outlet flue gas temperature is 311℃, the water wall outlet superheat is 12℃, the unit is in dry operation, the under-enthalpy of the water at the water wall inlet is relatively reduced by 64kJ / kg, the water wall outlet steam temperature deviation is controlled, the hydrodynamic stability is enhanced, and the denitrification system is stably and continuously put into use.

[0060] Example 3

[0061] like Figure 4 The figure shows a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment to adapt to deep peak regulation. On the basis of embodiment 1, a heat exchanger is added upstream of the steam compressor, and the steam below the target extraction pressure level first enters the heat exchanger for heat exchange before entering the steam compressor; Figure 4 The heat exchanger is located on the steam inlet pipeline of the existing final high-pressure heating. Of course, the heat exchanger can also be set on the pipeline of the boosting module, as long as the heat exchanger is set upstream of the steam compressor. The final extraction steam enters the heat exchanger to heat other working media, such as wind, water, coal, etc., and then enters the existing final high-pressure heater to heat the feed water after the steam is boosted by the steam compressor. In this way, the steam temperature entering the steam compressor can be reduced and the steam inlet flow rate of the existing final high-pressure heater can be relatively increased. At the same time, a new extraction steam isolation valve is set in the existing final high-pressure heater steam inlet pipeline, and the new extraction steam isolation valve is located at the front end of the heat exchanger upstream of the steam compressor. That is, when the steam lower than the target extraction pressure level connected to the inlet of the boosting module is the final extraction steam of the high-pressure cylinder of the unit, a new extraction steam isolation valve is set at the front end of the heat exchanger upstream of the steam compressor, so that when the heat exchanger and other equipment fail, the final exhaust steam of the high-pressure cylinder is disconnected by closing the new extraction steam isolation valve, ensuring the safety of system operation and improving the flexibility of system operation.

[0062] Example 4

[0063] like Figure 5 The figure shows a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment to adapt to deep peak regulation. Based on the embodiment 1, a heat exchanger is added upstream of the steam compressor and downstream of the steam compressor, and a new steam extraction isolation valve is set in the existing final high-pressure heater steam inlet pipeline, and the new steam extraction isolation valve is located at the front end of the heat exchanger upstream of the steam compressor.

[0064] The final stage extraction steam enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then increases the pressure through the steam compressor. Then, it enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then enters the existing final stage high-pressure heater to heat the feed water. This can reduce the steam temperature entering the steam compressor, reduce the steam temperature entering the existing final stage high-pressure heater, and relatively increase the steam inlet flow rate of the existing final stage high-pressure heater. By performing two heat exchanges before and after the steam compressor, the cascade utilization efficiency of energy is improved.

[0065] Example 5

[0066] like Figure 6 The figure shows a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment to adapt to deep peak regulation. On the basis of Example 1, the inlet steam source of the steam compressor is optimized from the final extraction steam to other heat recovery extraction steam or superheater system steam or reheater system steam of this unit or other units. Under the premise that the steam pressure at the outlet of the steam compressor is higher than the existing final extraction steam, the operation flexibility of this unit is improved; at the same time, a heat exchanger is added downstream of the steam compressor, and the steam at the outlet of the steam compressor enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then enters the existing final high-pressure heater to heat the feed water, so that the steam temperature entering the existing final high-pressure heater can be reduced and the steam inlet flow rate of the existing final high-pressure heater can be relatively increased.

[0067] Example 6

[0068] like Figure 7 The figure shows a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment to adapt to deep peak regulation. On the basis of Example 1, the inlet steam of the steam compressor is optimized from the final extraction steam to other heat recovery extraction steam or superheater system steam or reheater system steam of this unit or other units. Under the premise that the steam pressure at the outlet of the steam compressor is higher than the existing final extraction steam, the operation flexibility of this unit is improved; at the same time, a heat exchanger is added upstream of the steam compressor. After the steam enters the heat exchanger, it can heat other working media, such as wind, water, coal, etc., and then after the steam is pressurized by the steam compressor, it enters the existing final high-pressure heater to heat the feed water. In this way, the steam temperature entering the steam compressor can be reduced and the steam inlet flow rate of the existing final high-pressure heater can be relatively increased.

[0069] Example 7

[0070] like Figure 8The schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment to adapt to deep peak regulation is shown. On the basis of Example 1, the inlet steam of the steam compressor is optimized from the final extraction steam to other heat recovery extraction steam or superheater system steam or reheater system steam of this unit or other units. Under the premise that the outlet steam pressure of the steam compressor is higher than the existing final extraction steam, the operation flexibility of this unit is improved; at the same time, heat exchangers are added upstream of the steam compressor and downstream of the steam compressor; before entering the steam compressor, it first enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then increases the pressure through the steam compressor; after the steam compressor increases the pressure, it can also enter the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then enter the existing final high-pressure heater to heat the feed water, so that the steam temperature entering the steam compressor can be reduced, the steam temperature entering the existing final high-pressure heater can be reduced, the steam inlet flow rate of the existing final high-pressure heater can be relatively increased, and the cascade utilization efficiency of energy can be improved.

[0071] Although the specific embodiments of the present invention are described above, it should be understood by those skilled in the art that this is only for illustration and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A flexible operation system for coal-fired power units adapted to deep peak load regulation, characterized in that: It includes a deaerator, a pre-pump, a feed water pump, an existing final high-pressure heater, a boiler, a main steam throttling assembly, a high-pressure cylinder, and a steam extraction isolation valve. The low-pressure condensate at the outlet of the deaerator is pressurized by the pre-pump and the feed water pump in turn and then enters the existing final high-pressure heater for heating. The heated feed water enters the boiler and is heated by the economizer, the water-cooled wall, and the superheater heating surface in turn, and finally the main steam is obtained and enters the high-pressure cylinder to do work. The final extraction steam of the high-pressure cylinder enters the existing final high-pressure heater through the steam inlet pipe; the main steam throttling assembly is arranged on the high-pressure cylinder steam inlet pipe; the steam extraction isolation valve is arranged on the steam inlet pipe of the existing final high-pressure heater; A boosting module is connected to the steam inlet pipeline between the high-pressure cylinder and the existing final-stage high-pressure heater, and a boosting device is arranged in the pipeline of the boosting module. The inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level, and the outlet of the boosting module is connected to the steam inlet pipeline of the existing final-stage high-pressure heating and is located downstream of the extraction isolation valve. The steam entering the boosting module is pressurized by the boosting device and then enters the existing final-stage high-pressure heater to increase the feed water temperature of the unit under deep peak-shaving conditions.

2. The flexible operation system according to claim 1, characterized in that: The boosting device is a steam compressor.

3. The flexible operation system according to claim 2, characterized in that: A heat exchanger is added downstream of the steam compressor, and the steam below the target extraction pressure level is pressurized by the steam compressor, and then heat-exchanged by the heat exchanger before entering the existing final high-pressure heater; And / or, a heat exchanger is added upstream of the steam compressor, and steam with a pressure level lower than the target extraction pressure first enters the heat exchanger for heat exchange and then enters the steam compressor.

4. The flexible operation system according to claim 3, characterized in that: A heat exchanger is added downstream of the steam compressor and is located on the steam inlet pipeline of the existing final stage high pressure heating or on the pipeline of the boosting module; And / or, a heat exchanger is added upstream of the steam compressor and is located on the steam inlet pipeline of the existing final stage high-pressure heating or on the pipeline of the boosting module.

5. The flexible operation system according to claim 4, characterized in that: The source of steam with a pressure level lower than the target extraction pressure connected to the inlet of the boosting module is the final extraction steam of the high-pressure cylinder of the unit. The inlet of the boosting module is connected to the existing final high-pressure heated steam inlet pipeline and is located upstream of the extraction isolation valve.

6. The flexible operation system according to claim 5, characterized in that: A new steam extraction isolation valve is arranged in the existing final-stage high-pressure heater steam inlet pipeline, and the new steam extraction isolation valve is located at the front end of the heat exchanger upstream of the steam compressor.

7. The flexible operation system according to claim 3, characterized in that: The source of steam below the target extraction pressure level is the heat recovery extraction steam in this unit or other units, or the steam in the reheat system or the steam in the superheater system.

8. The flexible operation system according to claim 1, characterized in that: The main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.

9. The flexible operation system according to any one of claims 1 to 8, characterized in that: The flexible operation system is configured to throttle the main steam using a main steam throttling assembly to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

10. The flexible operation system according to any one of claims 1 to 8, characterized in that: A throttling component is set in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

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