Flexible operation system of coal power unit based on water supply supplementary heating

Abstract

The invention discloses a flexible operation system based on feed water supplementary heating for a coal power unit, which is characterized in that on the basis that an existing final-stage high-pressure heater is normally put into use to heat feed water, a newly added final-stage high-pressure heater is arranged between a feed water inlet of a boiler and a feed water outlet of the existing final-stage high-pressure heater; a pressurizing module is connected to a steam inlet of the newly-added final-stage high-pressure heater, steam lower than the target steam extraction pressure grade is introduced into an inlet of the pressurizing module, the newly-added final-stage high-pressure heater introduces the steam lower than the target steam extraction pressure grade through the connected pressurizing module, and the steam is pressurized and then conducts secondary heating or supplementary heating on feed water again; according to the method, the in-boiler feed water temperature of a unit under the deep peak regulation working condition is increased, meanwhile, certain feed water pressure is maintained, boiler dry-state operation of the unit under the deep peak regulation working condition is achieved, hydrodynamic stability is kept, a denitration system is continuously and stably put into operation, large-scale transformation of the system is avoided, and the method well adapts to operation of the unit responding to deep peak regulation of a power grid.

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 based on feedwater supplementary heating. 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-shaving conditions, and maintain the hydrodynamic stability and continuous and stable operation of the denitrification system, and provide a flexible operation system for coal-fired power units based on feed water supplementary heating.

[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 based on feed water supplementary heating, comprising a boiler, a deaerator 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 deaerator 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 and enters 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 the extraction steam pipeline; a regulating stage is arranged on the steam inlet pipeline of the high-pressure cylinder. A staged steam inlet valve group; an extraction steam isolation valve is provided on the steam extraction pipeline connecting the high-pressure cylinder and the existing final-stage high-pressure heater, and a new final-stage high-pressure heater is provided between the feed water inlet of the boiler and the feed water outlet of the existing final-stage high-pressure heater, and the steam inlet of the new final-stage high-pressure heater is connected to a boosting module, and the inlet of the boosting module is connected to steam with a pressure level lower than the target extraction steam pressure level. The steam entering the boosting module is pressurized in the boosting module and then enters the new final-stage high-pressure heater to supplement the feed water for heating, so as to increase the feed water temperature of the unit 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 unit's high-pressure cylinder final stage steam extraction entering the existing final stage high-pressure heater to heat the feed water, a new final stage high-pressure heater is arranged between the boiler's feed water inlet and the existing final stage high-pressure heater's feed water outlet, and the steam inlet of the new final stage high-pressure heater is connected to a boosting module, and the inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level. The steam entering the boosting module is pressurized in the boosting module and then enters the new final stage high-pressure heater to supplement the feed water heating, so as to increase the unit's inlet feed water temperature under deep peak regulation conditions; as the unit's inlet 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. That is, on the basis of the normal use of the existing final-stage high-pressure heater to heat the feed water, the newly added final-stage high-pressure heater introduces steam below the target extraction pressure level through the connected booster module, and after pressurization, performs secondary or supplementary heating of the feed water.

[0009] By introducing steam with a pressure lower than the target extraction pressure level, pressurizing it through the boosting module and then entering the newly added final-stage high-pressure heater to heat the feed water, compared with the solution of using main steam to replace the final-stage high-pressure heater 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 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.

[0010] Preferably, a steam compressor is provided in the pipeline of the boosting module, and the steam compressor is used to boost the steam entering the boosting module and having a pressure level lower than the target extraction pressure level; the pressure of the steam below the target extraction pressure level after being boosted by the steam compressor is higher than the pressure of the last stage extraction of the high-pressure cylinder.

[0011] In this scheme, a steam compressor is arranged in the boosting module, and the steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor and then enters the newly added final-stage high-pressure heater to supplement the heating of the feed water. The steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor to have a pressure higher than the pressure of the final-stage extraction steam of the high-pressure cylinder, thereby ensuring that the steam pressure after being compressed by the steam compressor and then entering the newly added final-stage high-pressure heater is higher than the pressure of the final-stage extraction steam originally entering the existing final-stage high-pressure heater, 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 feed water temperature entering the furnace of the unit under deep peak regulation conditions.

[0012] Preferably, a newly added steam extraction isolation valve is provided in the pipeline of the boosting module, and the newly added steam extraction isolation valve is located at the front end or the rear end of the steam compressor.

[0013] In this solution, a new steam extraction isolation valve is provided in the boosting module, and the new steam extraction isolation valve is provided at the front end or rear end of the steam compressor. The new steam extraction isolation valve is used to adjust the fluid flow entering the boosting module. In addition, when equipment such as the steam compressor or the new final-stage high-pressure heater fails, part of the final-stage steam extraction from the high-pressure cylinder entering the boosting module 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.

[0014] Preferably, the boosting module further comprises a heat exchanger, which is arranged downstream of the steam compressor. After the steam with a pressure lower than the target extraction pressure level is boosted by the steam compressor, it is first heat-exchanged by the heat exchanger before entering the newly added final-stage high-pressure heater;

[0015] And / or, the boosting module further includes a heat exchanger, which is disposed upstream of the steam compressor, and steam with a pressure level lower than the target extraction pressure level is first heat exchanged in the heat exchanger before entering the newly added final-stage high-pressure heater.

[0016] In this scheme, the heat exchanger is arranged 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 newly added final high-pressure heater to heat the feed water. In this way, the steam temperature entering the newly added final high-pressure heater can be reduced and the steam inlet flow rate of the newly added final high-pressure heater can be relatively increased.

[0017] The heat exchanger 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 increases the pressure through the steam compressor before entering the newly added final-stage high-pressure heater to heat the feed water. This can reduce the steam temperature entering the steam compressor and relatively increase the steam inlet flow rate of the newly added final-stage high-pressure heater.

[0018] Preferably, the steam below the target extraction pressure level comes from part of the final stage extraction steam of the high pressure cylinder, and the inlet of the boosting module is connected to the existing final stage high pressure heated extraction steam pipeline to introduce part of the final stage extraction steam of the high pressure cylinder.

[0019] In this scheme, the steam with a pressure level lower than the target extraction pressure level connected to the inlet of the boosting module is part of 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 heated extraction steam pipeline. A part of the final stage extraction steam of the high-pressure cylinder enters the existing final stage high-pressure heater to heat the feed water, and the other part of the final stage extraction steam of the high-pressure cylinder is pressurized by the boosting module and then introduced into the newly added high-pressure heater to supplement or reheat the feed water heated by the existing final stage high-pressure heater, so as to increase the unit's inlet feed water temperature under deep peak regulation conditions.

[0020] Preferably, the inlet of the boosting module is located upstream of the steam extraction isolation valve.

[0021] In this solution, the inlet of the boosting module is located upstream of the steam extraction isolation valve, and part of the final stage extraction steam is led out at the front end of the steam extraction isolation valve inlet, so that the steam extraction isolation valve can independently control a part of the final stage extraction steam of the high-pressure cylinder to enter the existing final stage high-pressure heater to heat the feed water. Even when the existing final stage high-pressure heater fails to work, closing the steam extraction isolation valve will not affect the normal operation of the boosting module and the newly added final stage high-pressure heater, thereby improving the flexibility of the unit operation.

[0022] 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.

[0023] 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.

[0024] Preferably, the number of valves of the regulating stage steam inlet valve group is four or six.

[0025] 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.

[0026] Preferably, the system is configured to: throttle the main steam by 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.

[0027] In this scheme, when the steam entering the newly added final-stage high-pressure heater is pressurized by the booster module to increase the unit's boiler feed water temperature 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.

[0028] 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.

[0029] In this scheme, when the steam entering the pressurized 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.

[0030] The positive and progressive effect of the present invention is that for an 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 normal use of the existing final-stage high-pressure heater to heat the feed water, a new final-stage high-pressure heater is arranged between the feed water inlet of the boiler and the feed water outlet of the existing final-stage high-pressure heater, and a boosting module is connected to the steam inlet of the new final-stage high-pressure heater, and the inlet of the boosting module is connected to steam below the target extraction pressure level. The new final-stage high-pressure heater introduces steam below the target extraction pressure level through the connected boosting module, and after pressurization, the feed water is reheated or supplemented to increase the unit's inlet feed water temperature under deep peak regulation conditions, while maintaining a certain feed water pressure, so as to achieve the unit's boiler dry operation under deep peak regulation conditions, maintain hydrodynamic stability, and continuously and stably put the denitrification system into operation, and avoid large-scale transformation of the boiler and steam turbine thermal system, so as to better adapt to the unit's operation in a wide load range in response to deep peak regulation of the power grid, and at the same time improve the unit's operation economy and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of a system for heating boiler feed water in the prior art.

[0032] Figure 2 This is a schematic diagram of a flexible operation system of a coal-fired power unit based on feed water supplementary heating according to an embodiment of the present invention (I).

[0033] Figure 3 This is a schematic diagram (II) of a flexible operation system of a coal-fired power unit based on supplementary feed water heating according to an embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of a flexible operation system of a coal-fired power unit based on feed water supplementary heating according to an embodiment of the present invention (III).

[0035] Figure 5 This is a schematic diagram (IV) of a flexible operation system of a coal-fired power unit based on supplementary feed water heating according to an embodiment of the present invention.

[0036] Figure 6 This is a schematic diagram of a flexible operation system of a coal-fired power unit based on supplementary feed water heating according to an embodiment of the present invention (V).

[0037] Figure 7 This is a schematic diagram of a flexible operation system of a coal-fired power unit based on feed water supplementary heating according to an embodiment of the present invention (VI).

[0038] Figure 8 This is a schematic diagram of a flexible operation system of a coal-fired power unit based on feed water supplementary heating according to an embodiment of the present invention (VII).

[0039] Fig. 9This is a schematic diagram of a flexible operation system of a coal-fired power unit based on feed water supplementary heating according to an embodiment of the present invention (VIII). 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] 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.

[0042] 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.

[0043] In order to solve the above technical problems, on the basis of the normal use of the existing final-stage high-pressure heater to heat the feed water, a new final-stage high-pressure heater is arranged between the feed water inlet of the boiler and the feed water outlet of the existing final-stage high-pressure heater, and the boosting module is connected to the steam inlet of the new final-stage high-pressure heater, and the inlet of the boosting module is connected to steam lower than the target extraction pressure level. The steam entering the boosting module is pressurized in the boosting module and then enters the new final-stage high-pressure heater for additional heating of the feed water, so as to increase the feed water temperature entering the furnace of the unit under deep peak regulation conditions, while maintaining a certain feed water pressure, and keeping the feed water at the economizer outlet 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.

[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 This is a schematic diagram of the flexible operation system of the coal-fired power unit based on supplementary feed water heating in this embodiment. On the basis of the normal operation of the existing final-stage high-pressure heat heater to heat the feed water, a new final-stage high-pressure heater is arranged between the feed water inlet of the boiler and the feed water outlet of the existing final-stage high-pressure heater, and a boosting module is connected to the steam inlet of the new final-stage high-pressure heater, and the inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level. In this embodiment, the steam with a pressure level lower than the target extraction pressure level comes from part of the final-stage extraction steam of the high-pressure cylinder, and the inlet of the boosting module is connected to the extraction pipe of the existing final-stage high-pressure heating. A part of the final-stage extraction steam of the high-pressure cylinder enters the existing final-stage high-pressure heater to heat the feed water, and another part of the final-stage extraction steam of the high-pressure cylinder is pressurized by the boosting module and then introduced into the new high-pressure heater to supplement or reheat the feed water heated by the existing final-stage high-pressure heater, so as to improve the unit's inlet feed water temperature under deep peak regulation conditions.

[0047] A steam compressor is provided in the boosting module, and the steam compressor is used to boost the steam entering the boosting module which is lower than the target extraction pressure level. The steam which is lower than the target extraction pressure level is pressurized by the steam compressor and then introduced into the newly added final-stage high-pressure heater for supplementary heating of the feed water. The steam which is lower than the target extraction pressure level has a pressure higher than the pressure of the final-stage extraction steam of the high-pressure cylinder after being boosted by the steam compressor, thereby ensuring that the steam pressure entering the newly added final-stage high-pressure heater after being compressed by the steam compressor is higher than the pressure of the final-stage extraction steam originally entering the existing final-stage high-pressure heater, 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 feed water temperature entering the furnace of the unit under deep peak regulation conditions.

[0048] A newly added steam extraction isolation valve is provided in the pipeline of the boosting module. The newly added steam extraction isolation valve is located at the front end of the steam compressor. Of course, the newly added steam extraction isolation valve can also be set at the rear end of the steam compressor. The steam flow entering the boosting module is regulated by the newly added steam extraction isolation valve. When the steam compressor, the newly added final-stage high-pressure heater and other equipment fail, the newly added steam extraction isolation valve can be closed to disconnect part of the final-stage steam extraction of the high-pressure cylinder entering the boosting module, thereby ensuring the safety of system operation and improving the flexibility of system operation.

[0049] When the unit is operating at partial load, the final-stage extraction steam of the existing final-stage high-pressure heater is put into normal use to heat the feed water. In the booster module, the steam compressor increases the pressure of part of the final-stage extraction steam and sends it to the newly added final-stage high-pressure heater for additional heating of the feed water. At the same time, the main steam is throttled to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

[0050] Figure 2 The 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 newly added final stage high-pressure heater to supplement the heating of the feed water to increase the unit's furnace feed water temperature under deep peak regulation conditions, the regulating stage steam inlet valve group is operated to throttle the main steam using the original regulating stage steam inlet valve group. No other regulating equipment needs to be added to maintain a certain feed water pressure, so that the economizer outlet feed water maintains a certain degree of subcooling, which is used 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, water wall inlet enthalpy deficiency, 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. The main steam is throttled by the regulating stage steam inlet valve group to maintain a certain feed water pressure. Compared with the isenthalpic throttling method of simply using 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 for 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 economizer outlet feed water at a certain degree of subcooling.

[0051] In this way, under the deep peak load regulation condition, taking the 20% THA condition as an example:

[0052] 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.

[0053] Example 2

[0054] Figure 3 This is a schematic diagram of a flexible operation system of a coal-fired power unit based on feedwater supplementary heating in this embodiment. On the basis of Embodiment 1, a heat exchanger is added downstream of the steam compressor. Steam below the target extraction pressure level is pressurized by the steam compressor, and then enters the newly added final high-pressure heater after heat exchange with the working medium inside the heat exchanger. The other working medium in the heat exchanger can be wind, water, coal, etc.; Figure 3 The intermediate heat exchanger is located on the pipeline of the boosting module. The steam pressurized by the steam compressor is first heat-exchanged in the heat exchanger and then enters the newly added final-stage high-pressure heater to heat the feed water. This can reduce the steam temperature entering the newly added final-stage high-pressure heater and relatively increase the steam inlet flow rate of the newly added final-stage high-pressure heater.

[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 scheme: main generator load is 200MW, 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℃, 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: 1.03MPa, 341℃, the newly added final stage high pressure steam inlet pressure and temperature parameters after being pressurized by the steam compressor and cooled by the heat exchanger are: 6.4MPa, 392℃ and the outlet feed water pressure and temperature parameters are: 12MPa, 280℃, the economizer outlet water temperature is 305℃, the subcooling degree is 20℃, the under enthalpy is 122kJ / kg, the economizer outlet flue gas temperature is 310℃, the water wall outlet superheat is 9℃, the unit is in dry operation, the under enthalpy of the water at the water wall inlet is relatively reduced by 54kJ / kg, the water wall outlet steam temperature deviation is controlled, and the water dynamic The power stability is enhanced, and the denitrification system is stably and continuously put into use; at the same time, the inlet and outlet flow, pressure and temperature parameters of the regulating stage are 604t / h, 13.2MPa, 591℃ and 604t / h, 6.1MPa, 544℃ respectively, the effective enthalpy drop per unit working fluid is 49.7kJ / kg, and the corresponding power is 8.3MW. 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. In addition, because the flow of a single valve in the regulating stage steam inlet valve group is relatively small, its pressure control of the main steam will be more accurate and convenient.

[0058] Example 3

[0059] Figure 4 Schematic diagram of the flexible operation system of the coal-fired power unit based on feedwater supplementary heating in this embodiment. On the basis of Embodiment 1, the booster module further includes a heat exchanger, which is arranged upstream of the steam compressor. Figure 4 The intermediate heat exchanger is located between the newly added steam extraction isolation valve and the steam compressor. Of course, the heat exchanger can also be set at the front end of the newly added steam extraction isolation valve; part of the final stage extraction steam of the high-pressure cylinder 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, and then enters the newly added final stage high-pressure heater to supplement the heating of the feed water. This can reduce the steam temperature entering the steam compressor and relatively increase the steam inlet flow rate of the newly added final stage high-pressure heater.

[0060] Example 4

[0061] Figure 5This is a schematic diagram of the flexible operation system of the coal-fired power unit based on supplementary heating of feed water in this embodiment. On the basis of Example 1, in the boosting module, heat exchangers are arranged upstream and downstream of the steam compressor. Part of the final extraction steam of the high-pressure cylinder first enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then is pressurized by the steam compressor. Then, it enters the heat exchanger located downstream of the steam compressor to heat other working fluids, such as wind, water, coal, etc., and then enters the newly added final high-pressure heater to heat the feed water. In this way, the steam temperature entering the steam compressor and the steam temperature entering the newly added final high-pressure heater can be reduced, and the steam inlet flow rate of the newly added final high-pressure heater can be relatively increased. By performing two heat exchanges before and after the steam compressor, the step-by-step utilization efficiency of energy is improved.

[0062] Example 5

[0063] Figure 6 This is a schematic diagram of the flexible operation system of the coal-fired power unit based on feed water supplementary heating in this embodiment. On the basis of Example 1, the source of steam below the target extraction pressure level is optimized from the final stage extraction 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, the operation flexibility of the unit is improved.

[0064] Example 6

[0065] Figure 7 This is a schematic diagram of the flexible operation system of the coal-fired power unit based on feed water supplementary heating in this embodiment. On the basis of Example 5, the boosting module also includes a heat exchanger, which is arranged downstream of the steam compressor. In the pipeline of the boosting module, the steam compressor, the newly added steam extraction isolation valve, and the heat exchanger are arranged in sequence. The steam below the target steam extraction pressure level is pressurized by the steam compressor, and then heat exchanged in the heat exchanger before entering the newly added final-stage high-pressure heater; the steam below the target steam extraction pressure level enters the boosting module, is pressurized by the steam compressor, and then enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then enters the newly added final-stage high-pressure heater to supplement the feed water. In this way, the steam temperature entering the newly added final-stage high-pressure heater can be reduced and the steam inlet flow rate of the newly added final-stage high-pressure heater can be relatively increased.

[0066] Example 7

[0067] Figure 8This is a schematic diagram of the flexible operation system of the coal-fired power unit based on the supplementary heating of feed water in this embodiment. On the basis of Example 5, the boosting module also includes a heat exchanger. The heat exchanger is arranged upstream of the steam compressor. In the pipeline of the boosting module, the heat exchanger, the steam compressor, and the newly added steam extraction isolation valve are connected and arranged in sequence. The steam below the target steam extraction pressure level first enters the heat exchanger to heat other working media, such as wind, water, coal, etc., and then is pressurized by the steam compressor. Finally, it enters the newly added final stage high pressure heater to supplement the feed water. In this way, the steam temperature entering the steam compressor can be reduced and the steam inlet flow rate of the newly added final stage high pressure heater can be relatively increased.

[0068] Example 8

[0069] Fig. 9 This is a schematic diagram of the flexible operation system of the coal-fired power unit based on feed water supplementary heating in this embodiment. On the basis of Example 5, the boosting module also includes a heat exchanger, and heat exchangers are added upstream of the steam compressor and downstream of the steam compressor; before entering the steam compressor, the steam below the target extraction pressure level first enters the heat exchanger located upstream of the steam compressor 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 enters the heat exchanger located downstream of the steam compressor to heat other working fluids, such as wind, water, coal, etc., and then enters the newly added final-stage high-pressure heater to heat the feed water. In this way, the steam temperature entering the steam compressor, the steam temperature entering the newly added final-stage high-pressure heater, the steam inlet flow rate of the newly added final-stage high-pressure heater is relatively increased, and the step-by-step utilization efficiency of energy can be improved.

[0070] 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 based on feed water supplementary heating, comprising a boiler, a deaerator system, a high-pressure cylinder and an existing final high-pressure heater, wherein 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 high-pressure heater, and the feed water heated by the existing final high-pressure heater enters the boiler, and is heated by the economizer, water-cooled wall and superheater heating surface in turn, 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 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 high-pressure heater, characterized in that A new final-stage high-pressure heater is arranged between the feed water inlet of the boiler and the feed water outlet of the existing final-stage high-pressure heater, and the steam inlet of the new final-stage high-pressure heater is connected to a boosting module. The inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level. The steam entering the boosting module is pressurized in the boosting module and then enters the new final-stage high-pressure heater to supplement the feed water for heating, 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 steam entering the boosting module and having a pressure lower than the target extraction pressure level; the pressure of the steam lower than the target extraction pressure level after being boosted by the steam compressor is higher than the pressure of the final extraction of the high-pressure cylinder.

3. The flexible operation system according to claim 2, characterized in that: A newly added steam extraction isolation valve is arranged in the pipeline of the boosting module, and the newly added steam extraction isolation valve is located at the front end or the rear end of the steam compressor.

4. The flexible operation system according to claim 3, characterized in that: The boosting module further includes a heat exchanger, which is arranged downstream of the steam compressor. After the steam with a pressure lower than the target extraction pressure level is boosted by the steam compressor, it is first heat-exchanged by the heat exchanger before entering the newly added final-stage high-pressure heater; And / or, the boosting module further includes a heat exchanger, which is disposed upstream of the steam compressor, and steam with a pressure level lower than the target extraction pressure level is first heat exchanged in the heat exchanger before entering the newly added final-stage high-pressure heater.

5. The flexible operation system according to claim 4, characterized in that: The steam with a pressure level lower than the target extraction pressure level comes from part of the final extraction steam of the high-pressure cylinder, and the inlet of the boosting module is connected to the extraction steam pipeline to introduce part of the final extraction steam of the high-pressure cylinder.

6. The flexible operation system according to claim 4, characterized in that: The inlet of the boost module is located upstream of the steam extraction isolation valve.

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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