System for coal power unit to adapt to flexible operation

Abstract

The invention discloses a system for a coal power unit to adapt to flexible operation, which is characterized in that for a subcritical unit, namely a high-pressure cylinder adopts a full-cycle steam admission mode and is not provided with a regulating stage, on the basis that an existing final-stage high-pressure heater is normally put into use to heat feed water, the whole-cycle steam admission mode is adopted; a newly-added final-stage high-pressure heater is arranged between a water supply inlet of a boiler and a water supply outlet of an existing final-stage high-pressure heater, a steam inlet of the newly-added final-stage high-pressure heater is connected with a pressurization module, and steam lower than a target steam extraction pressure grade is introduced into an inlet of the pressurization module; steam entering the pressurizing module is pressurized in the pressurizing module and then enters the newly-added last-stage high-pressure heater to conduct supplementary heating on feed water, so that the in-furnace feed water temperature of the unit under the deep peak regulation working condition is increased, the water temperature of an inlet of a coal economizer is increased along with increasing of the in-furnace feed water temperature of the unit, and the water temperature of an outlet of the coal economizer is increased. The water temperature of the outlet of the economizer is increased, the smoke temperature of the outlet of the economizer is increased, and the requirement for the smoke temperature of a denitration inlet is met.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation, and in particular to a system for coal-fired power generation units to adapt to flexible operation. 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. However, among the existing units, there are about 1,000 subcritical units with a capacity of about 350 million kilowatts and a rating of 300,000 kilowatts to 600,000 kilowatts, with an installed capacity of about 350 million kilowatts.

[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 300MW subcritical unit (the high-pressure cylinder adopts the full-cycle steam inlet method and is not equipped with a regulating stage) as an example, the load range of the regional power grid dispatching is 40%-100% THA. However, with the rapid development of new energy, the regional power grid has notified the unit that it needs to operate in a deep peak-shaving cloud, and the lower limit of load dispatching needs to be as low as 20%.

[0005] For subcritical units that need to participate in deep peak load regulation, such as those with a load variation range of 20%-100% THA, where the deep peak load range is 20%-30% THA or even lower (the high-pressure cylinder adopts a full-cycle steam inlet method and is not equipped with a regulating stage), the following problems will be faced:

[0006] (1) Under deep peak load conditions, the flue gas temperature at the economizer outlet will be lower than the lower limit of the normal operation temperature of the denitrification catalyst (such as 300°C), and the denitrification system will not be able to operate normally. It is expected that NOx emissions will increase sharply and far exceed the standard requirements (such as the emission index will increase from 25mg / Nm3 to more than 200mg / Nm3, far exceeding the standard value of 50mg / Nm3).

[0007] (2) The boiler drum outlet temperature will drop significantly, the main and reheat steam temperatures will drop significantly, the unit energy consumption will increase significantly, and the operating economy will drop significantly.

[0008] Therefore, how to maintain the continuous and stable operation of the denitrification system of the subcritical unit under deep peak-shaving conditions to avoid a sharp increase in unit energy consumption and a sharp decrease in operating economy has become an urgent problem that needs to be solved. Summary of the invention

[0009] The technical problem to be solved by the present invention is that the denitrification system of a subcritical unit cannot be put into operation stably under deep peak regulation conditions, the energy consumption of the unit increases significantly, and the operating economy decreases significantly. A system is provided to adapt to the flexible operation of a coal-fired power unit.

[0010] The present invention solves the above technical problems through the following technical solutions:

[0011] The present invention provides a system for coal-fired power generation units to adapt to flexible operation, comprising a boiler, a deaeration system, a high-pressure cylinder and an existing final-stage high-pressure heater, wherein the boiler comprises an economizer, a steam drum, a superheater, a header, a downcomer and a water-cooled wall; the economizer, the steam drum and the superheater are connected in sequence through pipelines, and water in the lower part of the steam drum is transported to the header through the downcomer, and then returned to the steam drum after being heated by the water-cooled wall; the high-pressure cylinder adopts a full-circle steam intake method and is not equipped with a regulating stage; the feed water inlet of the existing final-stage high-pressure heater is connected to the feed water outlet of the deaeration system, the feed water outlet of the existing final-stage high-pressure heater is connected to the feed water inlet of the boiler, the steam outlet of the boiler is connected to the high-pressure cylinder through the main steam pipeline, and the existing final-stage high-pressure heater is connected to the high-pressure cylinder. The steam inlet of the device is connected with the steam extraction port of the high-pressure cylinder through a steam inlet pipe; a main steam throttling assembly is provided on the main steam pipe; an extraction steam isolation valve is arranged on the steam inlet pipe; the system also includes a newly added final-stage high-pressure heater and a boosting module, the newly added 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, the inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level, the outlet of the boosting module is connected to the steam inlet of the newly added final-stage high-pressure heater, the steam entering the boosting module enters the newly added final-stage high-pressure heater after being pressurized in the boosting module, so as to improve the inlet feed water temperature of the unit under deep peak regulation conditions.

[0012] In this scheme, for subcritical units, that is, the high-pressure cylinder adopts a full-circle steam inlet method and is not 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 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. 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 furnace feed water temperature under deep peak regulation conditions. As the unit's furnace 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.

[0013] 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.

[0014] 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 at a pressure lower than the target extraction pressure level; after the steam at a pressure lower than the target extraction pressure level is boosted by the steam compressor, the pressure is higher than the pressure of the final extraction of the high-pressure cylinder.

[0015] 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 and has 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 existing 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.

[0016] 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.

[0017] 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. When the steam compressor, the new final-stage high-pressure heater and other equipment fail, part of the final-stage steam extraction of 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.

[0018] 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;

[0019] 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.

[0020] 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.

[0021] 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.

[0022] Preferably, 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 steam inlet pipeline to introduce part of the final extraction steam of the high-pressure cylinder.

[0023] 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 heating steam inlet 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.

[0024] Preferably, the inlet of the boosting module is located upstream of the steam extraction isolation valve.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] Preferably, the main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.

[0029] In this scheme, the main steam throttling component adopts a high-pressure cylinder steam inlet regulating valve group or a regulating valve to facilitate the adjustment of the pressure and flow of the main steam.

[0030] Preferably, the system is configured to: throttle the main steam using a main steam throttling assembly to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

[0031] 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.

[0032] 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.

[0033] In this scheme, a throttling component, such as a regulating valve, may also be provided in the feed water or steam piping system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

[0034] The positive and progressive effect of the present invention is that for a subcritical unit, that is, the high-pressure cylinder adopts a full-circle steam inlet method and is not 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 lower than the target extraction pressure level. The new final-stage high-pressure heater introduces steam lower than 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. 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. 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 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 at a pressure level 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 scheme has the advantages of relative safety, low cost, high flexibility in operation and regulation, and good economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of a system for heating boiler feed water in the prior art.

[0036] Figure 2 This is a schematic diagram of a system for adapting flexible operation of a coal-fired power unit according to a preferred embodiment of the present invention (I).

[0037] Figure 3 This is a schematic diagram of a system for adapting flexible operation of a coal-fired power unit in a preferred embodiment of the present invention (II).

[0038] Figure 4 This is a schematic diagram of a system for adapting flexible operation of a coal-fired power unit in a preferred embodiment of the present invention (III).

[0039] Figure 5 This is a schematic diagram of a system for adapting flexible operation of a coal-fired power unit according to a preferred embodiment of the present invention (IV).

[0040] Figure 6 This is a schematic diagram of a system for adapting flexible operation of a coal-fired power unit according to a preferred embodiment of the present invention (V).

[0041] Figure 7 This is a schematic diagram of a system for adapting flexible operation of a coal-fired power unit in accordance with a preferred embodiment of the present invention (VI).

[0042] Figure 8This is a schematic diagram of a system for adapting flexible operation of a coal-fired power unit according to a preferred embodiment of the present invention (VII).

[0043] Fig. 9 This is a schematic diagram of a system for adapting flexible operation of a coal-fired power unit in accordance with a preferred embodiment of the present invention (VIII). DETAILED DESCRIPTION

[0044] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0045] Figure 1 Schematic diagram of a boiler feed water heating system in the prior art, the system includes a boiler, a deaerator system, a high-pressure cylinder and an existing final-stage high-pressure heater, the boiler includes an economizer, a steam drum, a superheater, a header, a downcomer and a water-cooled wall; the economizer, the steam drum and the superheater are connected in sequence through pipelines, the water in the lower part of the steam drum is transported to the header through the downcomer, and then returned to the steam drum after being heated by the water-cooled wall; the deaerator system includes a deaerator, a pre-pump and a feed water pump; the high-pressure cylinder adopts a full-circle steam inlet method and is not equipped with a regulating stage; the feed water inlet of the existing final-stage high-pressure heater is connected to the feed water outlet of the deaerator system, the feed water outlet of the existing final-stage high-pressure heater is connected to the feed water inlet of the boiler, the steam outlet of the boiler is connected to the high-pressure cylinder through the main steam pipeline, and the steam inlet of the existing final-stage high-pressure heater is connected to the steam extraction port of the high-pressure cylinder through the steam inlet pipeline; a main steam throttling assembly is provided on the main steam pipeline; an extraction isolation valve is arranged on the steam inlet pipeline;

[0046] When the system is in operation: the low-pressure condensate at the outlet of the deaerator is pressurized by the pre-pump and the feed water pump in turn, and then enters the high-pressure heater for heating. The heated feed water enters the boiler, and enters the steam drum after further heating by the economizer. The steam-water mixture is separated in the steam drum, wherein: the water in the lower part of the steam drum is sent to the header through the downcomer, and then returned to the steam drum after being heated by the water-cooled wall; the wet saturated steam in the upper part of the steam drum enters the superheater and other heating surfaces for heating, and finally the main steam is obtained and enters the high-pressure cylinder to do work. The high-pressure cylinder adopts a full-circle steam inlet method, and is not equipped with a regulating stage. The main steam throttling assembly set on the main steam pipeline adjusts the pressure and flow of the main steam.

[0047] In order to solve the above technical problems, the present invention, on the basis of the normal use of the existing final-stage high-pressure heater to heat the feed water, arranges a new final-stage high-pressure heater between the feed water inlet of the boiler and the feed water outlet of the existing final-stage high-pressure heater, and connects the boosting module to the steam inlet of the new final-stage high-pressure heater, 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 supplementary heating of the feed water, so as to increase the inlet feed water temperature of the unit under deep peak regulation conditions, thereby increasing the inlet and outlet water temperature of the economizer, increasing the outlet flue gas temperature of the economizer, reducing the inlet enthalpy of the water-cooled wall, shortening the hot water section in the water-cooled wall, and at the same time, using the main steam throttling component to throttle the main steam or using a throttling component to be set in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet, so as to maintain a certain feed water pressure and keep the outlet feed water of the economizer 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.

[0048] Compared with the scheme of replacing the steam inlet of the final-stage high-pressure heater with the main steam after cooling and reducing the pressure, 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.

[0049] Example 1

[0050] Figure 2The figure shows a schematic diagram of the system for the coal-fired power unit in this embodiment to adapt to flexible operation. The low-pressure condensate at the outlet of the deaerator is pressurized by the pre-pump and the feed water pump in turn and then enters the high-pressure heater for heating. The heated feed water enters the boiler and enters the steam drum after further heating by the economizer. The steam-water mixture is separated in the steam drum, wherein: the water in the lower part of the steam drum is sent to the manifold through the downcomer, and then returned to the steam drum after being heated by the water-cooled wall; the wet saturated steam in the upper part of the steam drum enters the superheater and other heating surfaces for heating, and finally the main steam is obtained and enters the high-pressure cylinder to perform work. The high-pressure cylinder adopts a full-circle steam inlet method, and is not equipped with a regulating stage. The main steam throttling assembly arranged on the main steam pipeline regulates the pressure and flow of the main steam. In addition, 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 lower than the target extraction pressure level; in this embodiment, the steam with a pressure 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 steam inlet pipeline of the existing final-stage high-pressure heating, and the inlet of the boosting module is located upstream of the steam extraction isolation valve. 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 increase the inlet feed water temperature of the unit under deep peak regulation conditions.

[0051] A steam compressor is arranged in the boosting module, and 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. After the steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor, the pressure is higher than the pressure of the final-stage extraction steam of the high-pressure cylinder, thereby ensuring that the pressure of the steam 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.

[0052] 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.

[0053] When the unit is running 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 to supplement the feed water heating. At the same time, the high pressure cylinder steam inlet valve group is used to throttle the main steam to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling. It should be emphasized here that by using the original high pressure cylinder steam inlet valve group to throttle the main steam and maintain a certain feed water pressure, the economizer outlet feed water can maintain a certain degree of subcooling.

[0054] In this way, under the deep peak load regulation condition, taking the 20% THA condition as an example:

[0055] The unit's boiler feed water temperature can be increased to 75% THA or even 100% THA; as the unit's boiler feed water temperature increases, the economizer inlet water temperature increases, and then the economizer outlet water temperature increases, and the economizer outlet flue gas temperature increases and meets the denitrification inlet flue gas temperature requirement; while the economizer outlet water temperature increases, a certain feed water pressure is maintained so that the economizer outlet feed water maintains a certain degree of subcooling; as the feed water pressure increases, the steam-water mixture pressure in the drum also increases, the wet saturated steam temperature at the top of the drum also increases, and the main steam temperature can also be increased. As the main steam temperature, main steam volume and reheat steam volume ratio increase, the cold reheat steam and hot reheat steam temperatures are increased, which can avoid a significant increase in unit energy consumption and effectively improve the unit's operating economy.

[0056] Example 2

[0057] Figure 3 Shown is a schematic diagram of a system for adapting coal-fired power units to flexible operation.

[0058] On the basis of Example 1, 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 high-pressure heater; Figure 3 In the process, part of the final-stage extraction steam of the high-pressure cylinder enters the boosting module, is boosted 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 heating of 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.

[0059] Take the data of 20% THA condition of a 300MW subcritical unit (the high-pressure cylinder adopts full-cycle steam inlet method and is not equipped with a regulating stage) as an example.

[0060] Existing plan: main generator load is 60MW, the existing parameters of the final stage high-pressure steam inlet pressure and temperature are 1.29MPa, 370℃, and the parameters of the outlet feed water pressure and temperature are 8.5MPa, 192℃, the economizer outlet water temperature is 211℃, the subcooling degree is 107.3℃, the under-enthalpy is 521kJ / kg, the economizer outlet flue gas temperature is 272℃, and the denitrification system cannot be put into use.

[0061] In this embodiment: the main generator load is 60MW, the existing final stage extraction steam pressure and temperature parameters are 0.97MPa and 348℃, the new final stage high-pressure steam inlet parameters after being pressurized by the steam compressor and cooled by the heat exchanger are 3.9MPa and 402℃, and the pressure and temperature parameters of the outlet feed water are 10.5MPa and 252℃, the economizer outlet water temperature is 273℃, the subcooling degree is 41.6℃, the under enthalpy is 230kJ / kg, the economizer outlet flue gas temperature is 339℃, the denitrification system is stably and continuously put into use, and the unit's operating economy is improved due to the relative increase in feed water temperature.

[0062] Example 3

[0063] Figure 4 The figure shows a schematic diagram of a system for adapting the flexible operation of a coal-fired power unit. Based on Example 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.

[0064] Example 4

[0065] Figure 5 The figure shows a schematic diagram of a system for coal-fired power units to adapt to flexible operation. Based on Example 1, in the boosting module, heat exchangers are arranged upstream and downstream of the steam compressor, and 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 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, so that the steam temperature entering the steam compressor can be reduced, 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; the energy cascade utilization efficiency is improved by performing two heat exchanges before and after the steam compressor.

[0066] Example 5

[0067] Figure 6 The figure shows a schematic diagram of a system for coal-fired power units to adapt to flexible operation. Based on Example 1, the inlet steam source of the steam compressor is optimized from part of the final stage extraction steam of the high-pressure cylinder 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, and the operating flexibility of this unit is improved under the premise that the outlet steam pressure of the steam compressor is higher than the existing final stage extraction steam.

[0068] Example 6

[0069] Figure 7 The figure shows a schematic diagram of a system for coal-fired power units to adapt to flexible operation. Based on 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 boosted by the steam compressor, and then heat-exchanged by the heat exchanger before entering the newly added final high-pressure heater; the steam below the target steam extraction pressure level enters the boosting module, is boosted 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 high-pressure heater to supplement the heating of the feed water, so that 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.

[0070] Example 7

[0071] Figure 8 The figure shows a schematic diagram of a system for coal-fired power units to adapt to flexible operation. Based on Example 5, the boosting module also includes a heat exchanger, which 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. 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, and then enters the newly added final stage high pressure heater to supplement the heating of 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.

[0072] Example 8

[0073] Fig. 9The figure shows a schematic diagram of a system for coal-fired power units to adapt to flexible operation. Based on 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 boosted by the steam compressor; after being boosted 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 high-pressure heater to heat the feed water, so that the steam temperature entering the steam compressor, the steam temperature entering the newly added final high-pressure heater, and the steam inlet flow rate of the newly added final high-pressure heater can be relatively increased, and the step-by-step utilization efficiency of energy can also be improved.

[0074] 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 system for coal-fired power units to adapt to flexible operation, comprising a boiler, a deaeration system, a high-pressure cylinder and an existing final-stage high-pressure heater, wherein the boiler comprises an economizer, a steam drum, a superheater, a header, a downcomer and a water-cooled wall; the economizer, the steam drum and the superheater are connected in sequence through pipelines, and the water in the lower part of the steam drum is transported to the header through the downcomer, and then returned to the steam drum after being heated by the water-cooled wall; the high-pressure cylinder adopts a full-circle steam inlet method and is not equipped with a regulating stage; the feed water inlet of the existing final-stage high-pressure heater is connected to the feed water outlet of the deaeration system, the feed water outlet of the existing final-stage high-pressure heater is connected to the feed water inlet of the boiler, the steam outlet of the boiler is connected to the high-pressure cylinder through the main steam pipeline, and the steam inlet of the existing final-stage high-pressure heater is connected to the steam extraction port of the high-pressure cylinder through the steam inlet pipeline; a main steam throttling assembly is provided on the main steam pipeline; a steam extraction isolation valve is arranged on the steam inlet pipeline; it is characterized in that It also includes a newly added final-stage high-pressure heater and a boosting module, wherein the newly added 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, the inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level, and the outlet of the boosting module is connected to the steam inlet of the newly added final-stage high-pressure heater, and the steam entering the boosting module is pressurized in the boosting module and then enters the newly added final-stage high-pressure heater, so as to increase the feed water temperature of the unit entering the furnace under deep peak-shaving conditions.

2. The 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 which is lower than the target extraction pressure level; after the steam lower than the target extraction pressure level is boosted by the steam compressor, the pressure is higher than the pressure of the final extraction of the high-pressure cylinder.

3. The 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 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 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 stage extraction steam of the high pressure cylinder, and the inlet of the boosting module is connected to the steam inlet pipeline to introduce part of the final stage extraction steam of the high pressure cylinder.

6. The system according to claim 5, characterized in that The inlet of the boost module is located upstream of the steam extraction isolation valve.

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

8. The system of claim 1, wherein: The main steam throttling component is a high-pressure cylinder steam inlet regulating valve group or a regulating valve.

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

10. The 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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