Flexible operation system of coal power unit

Abstract

The invention discloses a flexible operation system of a coal power unit, which is characterized in that for an ultra (ultra) critical unit, a high-pressure cylinder adopts a partial steam admission mode and is provided with a regulating stage, and a pressurization module is additionally arranged on the basis of an existing boiler feed water heating system; the steam lower than the target steam extraction pressure grade enters the existing final-stage high-pressure heater after being pressurized through the pressurization module, the in-furnace feed water temperature of the unit under the deep peak regulation working condition is increased by increasing the pressure of the steam entering the existing final-stage high-pressure heater, meanwhile, a certain feed water pressure is maintained, and the energy consumption of the unit is reduced. Boiler dry-state operation of the unit under the working condition of deep peak regulation is achieved, hydrodynamic stability is kept, a denitration system is continuously and stably put into operation, large-scale transformation of a boiler and a steam turbine thermodynamic system is avoided, wide-load-range operation of the unit in response to deep peak regulation of a power grid is well adapted, and meanwhile the operation economical efficiency and flexibility of the unit are improved.

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. 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, maintain the hydrodynamic stability, and ensure the continuous and stable operation of the denitrification system, so as to provide a flexible operation system for coal-fired power units.

[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, comprising a boiler, a deaeration system, a high-pressure cylinder and an existing final-stage high-pressure heater, wherein the high-pressure cylinder adopts a partial steam intake mode and is equipped with a regulating stage; the feed water outlet of the deaeration system enters the existing final-stage high-pressure heater, and the feed water heated by the existing final-stage high-pressure heater enters the boiler, and is heated by the economizer, the water-cooled wall and the superheater heating surface in sequence, and finally the main steam is obtained to enter the high-pressure cylinder to perform work, and the final-stage extraction steam of the high-pressure cylinder enters the existing final-stage high-pressure heater through an extraction steam pipeline; a regulating-stage steam intake valve group is arranged on the steam intake pipeline of the high-pressure cylinder; an extraction steam isolation valve is arranged on the extraction steam pipeline connecting the high-pressure cylinder and the existing final-stage high-pressure heater, and is characterized in that a boosting module is added, and the inlet of the boosting module is connected to steam lower than the target extraction steam pressure level, and the outlet of the boosting module is connected to the extraction steam pipeline and is located downstream of the extraction steam isolation valve, and the steam entering the boosting module enters the existing final-stage high-pressure heater after being pressurized by the boosting module, so as to improve the unit's inlet feed water temperature under deep peak regulation conditions.

[0008] In this scheme, for the ultra-supercritical unit, its high-pressure cylinder adopts a partial steam intake method and is equipped with a regulating stage. On the basis of the existing boiler feed water heating system, a boosting module is added. The inlet of the boosting module is connected to steam lower than the target extraction pressure level. The outlet of the boosting module is connected to the extraction pipeline and is located downstream of the extraction isolation valve. When the steam lower than the target extraction pressure level is pressurized by the boosting module and enters the existing final high-pressure heater to heat the feed water, the extraction isolation valve is in a closed state upstream, cutting off the original high-pressure cylinder final extraction steam and directly entering the existing final high-pressure heater to heat the feed water; the steam entering the boosting module enters the existing final high-pressure heater after being pressurized by the boosting module. By increasing the pressure of the steam entering the existing final high-pressure heater, the unit's feed water temperature under deep peak regulation conditions is increased. As the unit's feed water temperature increases, the economizer inlet water temperature is increased, and then the economizer outlet water temperature is increased, and the economizer outlet flue gas temperature is increased and meets the denitrification inlet flue gas temperature requirement. By introducing steam with a pressure lower than the target extraction pressure level, pressurizing it through the boosting module and then entering the existing final-stage high-pressure heater to heat the feed water, compared with the solution of replacing the final-stage high-pressure heater with the main steam after cooling and reducing the pressure, the use of high-temperature and high-pressure pipelines can be saved, and 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 can be avoided. In addition, the extraction steam with a pressure lower than 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 solution has the advantages of relative safety, low cost, high flexibility in operation and regulation, and good economy.

[0009] Preferably, a steam compressor is provided in the pipeline of the boosting module, and the steam compressor is used to boost the pressure of the steam entering the boosting module and having a pressure level lower than the target steam extraction pressure level.

[0010] In this scheme, a steam compressor is arranged in the boosting module, and the steam compressor is used to pressurize the steam below the target extraction pressure level and then enter the existing final high-pressure heater to heat the feed water, so as to increase the inlet feed water temperature of the unit under the deep peak-shaving condition; the steam compressor pressurizes the steam below the target extraction pressure level to a pressure higher than the pressure of the final-stage extraction of the high-pressure cylinder, thereby ensuring that the feed water is heated to a higher temperature, that is, the feed water temperature entering the furnace is increased to increase the inlet feed water temperature of the unit under the deep peak-shaving condition.

[0011] 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 passes through the heat exchanger to exchange heat with the working medium inside the heat exchanger before entering the existing final high-pressure heater;

[0012] 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 to exchange heat with the working fluid inside the heat exchanger before entering the steam compressor.

[0013] 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;

[0014] 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.

[0015] Preferably, the pressure of the steam below the target extraction pressure level after being pressurized by the steam compressor is higher than the pressure of the extraction steam at the last stage of the high-pressure cylinder.

[0016] In this scheme, after the steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor, its pressure is higher than the pressure of the last-stage extraction steam of the high-pressure cylinder, ensuring that the steam pressure after being compressed by the steam compressor and then entering the existing last-stage high-pressure heater is higher than the pressure of the last-stage extraction steam originally entering the existing last-stage high-pressure heater, thereby ensuring that the feed water is heated to a higher temperature, that is, the water temperature of the feed water entering the boiler is increased.

[0017] Preferably, 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, and the inlet of the boosting module is connected to the extraction steam pipeline and is located upstream of the extraction steam isolation valve.

[0018] 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 existing final high-pressure heating steam extraction pipeline 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.

[0019] Preferably, a new steam extraction isolation valve is provided in the steam extraction pipeline, and the new steam extraction isolation valve is located at the front end of the heat exchanger upstream of the steam compressor.

[0020] In the present scheme, a new steam extraction isolation valve is provided in the steam extraction pipeline, 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 last 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. When the heat exchanger and other equipment fail, the last stage steam extraction 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.

[0021] Preferably, the source of the steam with a pressure level lower than 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.

[0022] 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.

[0023] Preferably, the number of valves of the regulating stage steam inlet valve group is four or six.

[0024] In this scheme, the number of valves in the regulating stage steam inlet valve group is four or six, and the main steam flow is adjusted by multiple valves. Not only is the flow control accuracy high, but the flow of a single valve is relatively small, and the pressure control of the main steam will be more accurate and convenient.

[0025] Preferably, the flexible operation system is configured to throttle the main steam using the regulating stage steam inlet valve group to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

[0026] In this scheme, when the steam entering the existing last-stage high-pressure heater is pressurized by the booster module to increase the feed water temperature of the unit under deep peak-shaving conditions, the regulating-stage 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.

[0027] 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.

[0028] In this scheme, when the steam entering the existing final-stage high-pressure heater is pressurized by the booster module to increase the feed water temperature of the unit under deep peak-shaving conditions, a throttling component, such as a regulating valve, can also be 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.

[0029] The positive progressive effect of the present invention is that for supercritical (ultracritical) units, their high-pressure cylinders adopt a partial steam intake method and are equipped with a regulating stage. On the basis of the existing boiler feed water heating system, a boosting module is added. Steam below the target extraction pressure level is pressurized by the boosting module and then enters the existing final-stage high-pressure heater. By increasing the pressure of the steam entering the existing final-stage high-pressure heater, the unit's feed water temperature under deep peak-shaving conditions is increased, while maintaining a certain feed water pressure, thereby achieving dry operation of the boiler under deep peak-shaving conditions, maintaining hydrodynamic stability, and continuously and stably putting the denitrification system into operation, and avoiding large-scale transformation of the boiler and steam turbine thermal systems, better adapting to the wide load range operation of the unit in response to deep peak-shaving of the power grid, while improving the unit's operating economy and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of a system for heating boiler feed water in the prior art.

[0031] Figure 2 The present invention is a schematic diagram of a flexible operation system of a coal-fired power unit according to a preferred embodiment of the present invention (I).

[0032] Figure 3 The present invention is a schematic diagram of a flexible operation system of a coal-fired power unit according to a preferred embodiment of the present invention (II).

[0033] Figure 4 The present invention is a schematic diagram of a flexible operation system of a coal-fired power unit according to a preferred embodiment of the present invention (III).

[0034] Figure 5 The present invention is a schematic diagram of a flexible operation system of a coal-fired power unit according to a preferred embodiment of the present invention (IV).

[0035] Figure 6 The present invention is a schematic diagram of a flexible operation system of a coal-fired power unit according to a preferred embodiment of the present invention (V).

[0036] Figure 7 A schematic diagram of a flexible operation system of a coal-fired power unit according to a preferred embodiment of the invention is shown in FIG6.

[0037] Figure 8 A schematic diagram of a flexible operation system of a coal-fired power unit according to a preferred embodiment of the invention is shown in FIG. 7 .

[0038] Fig. 9 A schematic diagram of a flexible operation system of a coal-fired power unit according to a preferred embodiment of the invention is shown in FIG8. DETAILED DESCRIPTION

[0039] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0040] Figure 1 It is a schematic diagram of a system for heating boiler feed water in the prior art, the system comprising a boiler, a deaerator system, a high-pressure cylinder and an existing final-stage high-pressure heater, the feed water outlet of the deaerator system enters the existing final-stage high-pressure heater, specifically, the deaerator system comprises a deaerator, a pre-pump and a feed water pump connected by pipelines, the boiler comprises an economizer, a water-cooled wall and a superheater; the high-pressure cylinder adopts a partial steam intake method and is equipped with a regulating stage, a regulating stage steam intake valve group is arranged on the high-pressure cylinder steam intake pipeline, an extraction steam isolation valve is provided on the extraction steam pipeline connecting the high-pressure cylinder and the existing final-stage high-pressure heater; the steam intake source of the existing final-stage high-pressure heater is the final-stage extraction steam of the high-pressure cylinder.

[0041] When the system is in operation: the low-pressure condensate passes through the deaerator, the pre-pump, and the feed water pump for pressurization, 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 regulating-stage steam inlet valve group arranged on the high-pressure cylinder steam inlet pipe controls the main steam entering the high-pressure cylinder; the last-stage extraction steam of the high-pressure cylinder enters the existing last-stage high-pressure heater to heat the feed water.

[0042] 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 extraction pipe between the high-pressure cylinder and the existing final-stage high-pressure heater, the outlet of the boosting module is connected to the existing final-stage high-pressure heating extraction pipe and is located downstream of the extraction isolation valve, by introducing steam lower than the target extraction pressure level into the boosting module, the extraction isolation valve is in a closed state upstream, the original high-pressure cylinder final-stage extraction steam is cut off and directly enters the existing final-stage high-pressure heater to heat the feed water, the steam lower than the target extraction pressure level is pressurized by the boosting module and enters the existing final-stage high-pressure heater to heat the feed water, so as to increase the unit's feed water temperature under deep peak regulation conditions, while maintaining a certain feed water pressure, and keeping the economizer outlet feed water at a certain degree of subcooling. Among them, the steam of the target extraction pressure level can be understood as the 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, without setting the boosting module; the extraction steam source below 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 the aforementioned steam and other relatively low-pressure steam, such as a mixture of unit heat recovery extraction steam, reheat steam, etc.

[0043] 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.

[0044] Example 1

[0045] Figure 2 Shown is a schematic diagram of the flexible operation system of the coal-fired power unit of this embodiment. Based on the existing boiler feed water heating system, the present invention connects a boosting module in the steam extraction pipeline between the high-pressure cylinder and the existing final-stage high-pressure heater, and arranges a steam compressor in the boosting module. The outlet of the boosting module is connected to the steam extraction pipeline and is located downstream of the steam extraction isolation valve. Steam with a pressure lower than the target steam extraction pressure level is introduced into the boosting module, and after being pressurized by the steam compressor, it enters the existing final-stage high-pressure heater to heat the feed water. After the steam with a pressure lower than the target steam extraction pressure level is pressurized by the steam compressor, the pressure is higher than the pressure of the final-stage steam extraction of the high-pressure cylinder.

[0046] In this embodiment, the source of steam introduced at a pressure level lower than the target extraction pressure level is the final extraction steam of the high-pressure cylinder of the unit. The inlet of the boosting module is connected to the extraction steam pipeline and is located upstream of the extraction steam isolation valve, that is, a steam compressor is arranged in parallel between the inlet and outlet of the extraction steam isolation valve of the extraction steam pipeline. The final extraction steam of the high-pressure cylinder enters the boosting module, is pressurized by the steam compressor, and then enters the existing final high-pressure heater to heat the feed water, so as to increase the unit's inlet feed water temperature under deep peak regulation conditions.

[0047] 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.

[0048] When the unit is operated at partial load, when the pressure of the final stage extraction steam is increased by using the steam compressor, the extraction steam isolation valve on the extraction steam pipeline connected to the existing final stage high-pressure heater is in a closed state.

[0049] at the same time, Figure 2The steam inlet pipe of the medium and high pressure cylinder is arranged with a regulating stage steam inlet valve group, which has 4 valves. The number of valves can be adjusted as needed, and can also be set to 6. The regulating stage 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. 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, by operating the regulating stage steam inlet valve group, that is, using the original regulating stage steam inlet valve group to throttle the main steam, there is no need to add other regulating equipment 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 and other phenomena, 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. The main steam is throttled by the regulating stage steam inlet valve group to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain degree of subcooling; compared with the isenthalpic throttling method that simply uses valves without configuring the regulating stage, the regulating stage steam inlet valve group can achieve a certain steam enthalpy drop under the same pressure control effect on the main steam, and the unit economy is relatively improved. Moreover, since the flow rate of a single valve in the regulating stage steam inlet valve group is relatively small, the pressure control of the main steam will be more accurate and convenient. Of course, in other embodiments, a throttling component, such as a regulating valve, can be 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 and keep the feed water at the economizer outlet at a certain degree of subcooling.

[0050] In this way, under the deep peak load regulation condition, taking the 20% THA condition as an example:

[0051] The unit's boiler feed water temperature can be increased to a feed water temperature level of 75% THA or even 100% THA; as the unit's boiler feed water temperature increases, the economizer inlet water temperature is increased, and then the economizer outlet water temperature is increased, and the economizer outlet flue gas temperature is increased and meets the denitrification inlet flue gas temperature requirement; while the economizer outlet water temperature is increased, 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 is increased, thereby reducing the water wall inlet under-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, achieving dry operation of the boiler.

[0052] Example 2

[0053] Figure 3 The figure shows a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment.

[0054] On the basis of Example 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 enters the existing final high-pressure heater after heat exchange with the working medium inside the heat exchanger. The working medium in the heat exchanger can be wind, water, coal, etc.; Figure 3 The middle heat exchanger is located on the steam extraction pipeline connected to the existing final-stage high-pressure heater. Of course, the heat exchanger can also be set on the pipeline of the boosting module, as long as the steam pressurized by the steam compressor is heat exchanged before entering the existing final-stage high-pressure heater. The steam pressurized by the steam compressor is first heat exchanged in the heat exchanger and then enters 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.

[0055] Take a 1000MW ultra-supercritical unit, whose high-pressure cylinder adopts partial steam admission, is equipped with a regulating stage, and has a 20% THA operating condition as an example.

[0056] Existing plan: main generator load is 200MW, the existing last stage high pressure heater inlet steam pressure and temperature parameters are 1.75MPa, 436℃ and outlet feed water pressure and temperature parameters are 6MPa, 192℃ respectively, economizer outlet water temperature is 240℃, subcooling degree is 36℃, under-enthalpy is 176kJ / kg, economizer outlet flue gas temperature is 245℃, water wall outlet is wet saturated steam, the unit is in wet operation state, and the denitrification system cannot be put into use.

[0057] The scheme of this embodiment: the load of the main generator is 200MW, the existing final stage extraction steam pressure and temperature parameters are 1.04MPa and 342℃ respectively, the existing final stage high pressure steam inlet pressure and temperature parameters after being pressurized by the steam compressor and cooled by the heat exchanger are 6.5MPa and 390℃ respectively, and the outlet feed water pressure and temperature parameters are 12.1MPa and 281℃ respectively, the economizer outlet water temperature is 306℃, the subcooling degree is 19℃, the under enthalpy is 120kJ / kg, the economizer outlet flue gas temperature is 312℃, the water wall outlet superheat is 11℃, the unit is in dry operation, the under enthalpy of the water wall inlet water is relatively reduced by 56kJ / kg, and the water wall outlet steam The temperature deviation is controlled, the hydrodynamic stability is enhanced, and the denitrification system is stably and continuously put into use; at the same time, the inlet and outlet parameters of the regulating stage are 603t / h, 13.1MPa, 589℃ and 603t / h, 6.2MPa, 545℃ respectively, the effective enthalpy drop per unit working fluid is 44.1kJ / kg, and the corresponding power is 7.4MW. Compared with the isenthalpic throttling method that simply uses valves without configuring a regulating stage, the regulating stage steam inlet valve group can achieve the same pressure control effect on the main steam, and the unit economy is relatively improved. Moreover, because the flow rate of a single valve in the regulating stage steam inlet valve group is relatively small, the pressure control of the main steam will be more precise and convenient.

[0058] Example 3

[0059] Figure 4 The figure shows a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment. 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 and then enters the steam compressor; Figure 4 The heat exchanger is located on the extraction steam pipeline connected to the existing final high-pressure heater. 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 the internal working medium of the heat exchanger, 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 extraction steam pipeline connected to the existing final high-pressure heater, 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 extraction 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.

[0060] Example 4

[0061] Figure 5 The figure shows a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment. On the basis of Embodiment 1, heat exchangers are added upstream of the steam compressor and downstream of the steam compressor, and a new steam extraction isolation valve is provided in the steam extraction pipeline connected to the existing final stage high-pressure heater. The new steam extraction isolation valve is located at the front end of the heat exchanger upstream of the steam compressor.

[0062] 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.

[0063] Example 5

[0064] Figure 6 Shown is a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment. On the basis of Embodiment 1, the source of steam below the target extraction pressure level is optimized from the final stage extraction steam to other heat recovery extraction steam or superheater system steam or reheater system steam of this unit or heat recovery extraction steam or superheater system steam or reheater system steam of other units. Under the premise that the steam pressure at the outlet of the steam compressor is higher than the existing final stage extraction steam, the operating flexibility of the unit is improved.

[0065] Example 6

[0066] Figure 7 The figure shows a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment. On the basis of Embodiment 5, the boosting module also includes a heat exchanger, which is arranged downstream of the steam compressor. 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 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.

[0067] Example 7

[0068] Figure 8As shown is a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment. On the basis of Example 5, the boosting module also includes a heat exchanger, which is arranged upstream of the steam compressor. Steam with a pressure level lower than the target extraction pressure level enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then is pressurized by the steam compressor before entering the existing final-stage 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-stage high-pressure heater can be relatively increased.

[0069] Example 8

[0070] Fig. 9 As shown is a schematic diagram of the flexible operation system of the coal-fired power unit in this embodiment. On the basis of Example 5, heat exchangers are added upstream of the steam compressor and downstream of the steam compressor; before entering the steam compressor, the steam first enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then is pressurized by the steam compressor; after being pressurized by the steam compressor, it can also enter the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then enter the existing final-stage 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-stage high-pressure heater can be reduced, the steam inlet flow rate of the existing final-stage high-pressure heater can be relatively increased, and the step-by-step 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 of a coal-fired power unit includes a boiler, a deaerator system, a high-pressure cylinder and an existing final-stage high-pressure heater. The high-pressure cylinder adopts a partial steam intake method and is equipped with a regulating stage. The feed water outlet of the deaerator system enters the existing final-stage high-pressure heater. The feed water heated by the existing final-stage high-pressure heater enters the boiler and is heated by the economizer, water-cooled wall and superheater heating surface in turn. 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 the extraction steam pipeline. A regulating-stage steam intake valve group is arranged on the steam intake pipeline of the high-pressure cylinder. An extraction steam isolation valve is arranged on the extraction steam pipeline connecting the high-pressure cylinder and the existing final-stage high-pressure heater. It is characterized in that A boosting module is added, and 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 extraction pipe and is located downstream of the extraction isolation valve. The steam entering the boosting module enters the existing final-stage high-pressure heater after being pressurized in the boosting module, so as 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: A steam compressor is arranged in the pipeline of the boosting module, and the steam compressor is used to boost the pressure of the steam entering the boosting module and having a pressure level lower than the target steam extraction pressure level.

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 passes through the heat exchanger to exchange heat with the working medium inside 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 to exchange heat with the working fluid inside the heat exchanger before entering the steam compressor.

4. The flexible operation system according to claim 3, characterized in that: The steam pressure which is lower than the target extraction pressure level is higher than the pressure of the final extraction steam of the high pressure cylinder after being pressurized by the steam compressor.

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 extraction steam pipeline and is located upstream of the extraction steam isolation valve.

6. The flexible operation system according to claim 5, characterized in that: A new steam extraction isolation valve is provided in the steam extraction 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 4, 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 number of valves of the regulating stage steam inlet valve group is four or six.

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 by utilizing the regulating stage steam inlet valve group to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain subcooling degree.

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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