System for deep peak regulation operation of coal power unit

Abstract

The invention discloses a deep peak regulation operation system for a coal power unit, which is characterized in that for a subcritical unit, a high-pressure cylinder adopts a partial steam admission mode and is provided with a regulating stage, and a pressurization module is additionally arranged on the basis of an existing boiler feed water heating system; the steam lower than the target steam extraction pressure grade enters the existing final-stage high-pressure heater after being pressurized by the pressurization module, and the water supplied to the outlet of the economizer is kept at a certain supercooling degree by increasing the pressure of the steam entering the existing final-stage high-pressure heater and maintaining a certain water supply pressure at the same time. The method is used for increasing the in-furnace feed water temperature of a unit under the deep peak regulation working condition, further increasing the water temperature of an economizer inlet, the water temperature of an economizer outlet, the smoke temperature of the economizer outlet and the steam temperature of a steam pocket outlet, finally achieving continuous and stable operation of a denitration system of the unit under the deep peak regulation working condition, and avoiding great increase of energy consumption of the unit. And the unit operation economy is effectively improved.

Description

Technical Field

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

[0002] At present, high-parameter, large-capacity, high-efficiency and low-carbon ultra-supercritical units have become the mainstream of new thermal power plant unit selection. However, among the existing units, there are about 1,000 subcritical units with a capacity of 300,000 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 a full-cycle steam inlet method and is 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 deep peak-shaving mode, 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, their high-pressure cylinders adopt partial steam inlet mode and are equipped with regulating stages. The load variation range is 20%-100% THA. Among them, the deep peak load range is 20%-30% THA, or even lower, which will face the following problems:

[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. The denitrification system will not be able to operate normally, and 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 ).

[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 under deep peak-shaving conditions, the denitrification system of a subcritical unit cannot operate normally, the energy consumption of the unit increases significantly, and the operating economy decreases significantly. A system for deep peak-shaving operation of a coal-fired power unit is provided.

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

[0011] The present invention provides a system for deep peak-shaving operation of a coal-fired power unit, comprising a boiler, a deaeration system, a high-pressure cylinder and an existing final-stage high-pressure heater, wherein the 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 at the bottom of the steam drum is fed 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 partial steam intake mode and is 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, and the steam of the boiler 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 of the boiler is connected to the feed water outlet of the deaeration system; the feed water outlet of the deaeration system ... The steam outlet 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 regulating-stage steam inlet valve group is provided on the main steam pipeline, and a steam extraction isolation valve is arranged on the steam inlet pipeline; it also includes an additional boosting module, the inlet of the boosting module is connected to steam with a pressure level lower than the target steam extraction pressure level, the outlet of the boosting module is connected to the steam inlet pipeline and is located downstream of the steam extraction isolation valve, and the steam entering the boosting module enters the existing final-stage high-pressure heater after being pressurized by the boosting module, so as to increase the feed water temperature of the unit under deep peak-shaving conditions.

[0012] In this scheme, for the subcritical unit, its high-pressure cylinder adopts a partial steam intake method and is equipped with a regulating stage. On the basis of the existing boiler feed water heating system, a boosting module is added. The inlet of the boosting module is connected to steam lower than the target extraction pressure level, and the outlet of the boosting module is connected to the steam inlet pipeline and is located downstream of the extraction isolation valve. When the steam lower than the target extraction pressure level is pressurized by the boosting module and enters the existing final high-pressure heater to heat the feed water, the extraction isolation valve is in a closed state upstream, cutting off the original high-pressure cylinder final stage extraction steam and directly entering the existing final high-pressure heater to heat the feed water; the steam entering the boosting module enters the existing final high-pressure heater after being pressurized by the boosting module. By increasing the pressure of the steam entering the existing final high-pressure heater, the unit's feed water temperature under deep peak regulation conditions is increased. As the unit's feed water temperature increases, the economizer inlet water temperature is increased, and then the economizer outlet water temperature is increased, and the economizer outlet flue gas temperature is increased and meets the denitrification inlet flue gas temperature requirement. By introducing steam with a pressure lower than the target extraction pressure level, pressurizing it through the boosting module and then entering the existing final-stage high-pressure heater to heat the feed water, compared with the solution of replacing the final-stage high-pressure heater with the main steam after cooling and reducing the pressure, the use of high-temperature and high-pressure pipelines can be saved, and the negative safety impact caused by the instantaneous change of the main and re-steam heat absorption ratio due to the use of the main steam can be avoided. In addition, the extraction steam with a pressure lower than the target extraction pressure level adopted in the present invention has better thermal economy than the main steam that does not do work in the turbine. Therefore, this solution has the advantages of relative safety, low cost, high flexibility in operation and regulation, and good economy.

[0013] Preferably, a steam compressor is provided in the pipeline of the boosting module, and the steam compressor is used to boost the pressure of the steam entering the boosting module and having a pressure level lower than the target steam extraction pressure level.

[0014] In this scheme, a steam compressor is set in the boosting module. The steam below the target extraction pressure level is pressurized by the steam compressor and then enters the existing final-stage high-pressure heater to heat the feed water, so as to increase the feed water temperature of the unit under deep peak-shaving conditions.

[0015] 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 existing final-stage high-pressure heater;

[0016] And / or, the boosting module further includes a heat exchanger, which is disposed upstream of the steam compressor, and the steam with a pressure level lower than the target extraction pressure level is first heat-exchanged in the heat exchanger before entering the existing final-stage high-pressure heater.

[0017] Preferably, steam with a pressure lower than the target extraction pressure level is pressurized by a steam compressor, enters a heat exchanger to heat other working fluids such as wind, water, coal, etc., and then enters the existing final stage high pressure heater to heat the feed water, thereby reducing the temperature of the steam entering the existing final stage high pressure heater and relatively increasing the steam inlet flow rate of the existing final stage high pressure heater;

[0018] A heat exchanger is added upstream of the steam compressor. Steam with a pressure lower than the target extraction pressure level enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then increases the pressure through the steam compressor before entering the existing final-stage high-pressure heater to heat the feed water. This can reduce the temperature of the steam entering the steam compressor and relatively increase the steam inlet flow rate of the existing final-stage high-pressure heater.

[0019] Preferably, the pressure of the steam below the target extraction pressure level after being pressurized by the steam compressor is higher than the pressure of the extraction steam at the last stage of the high-pressure cylinder.

[0020] In this scheme, after the steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor, its pressure is higher than the pressure of the last-stage extraction steam of the high-pressure cylinder, ensuring that the steam pressure after being compressed by the steam compressor and then entering the existing last-stage high-pressure heater is higher than the pressure of the last-stage extraction steam originally entering the existing last-stage high-pressure heater, thereby ensuring that the feed water is heated to a higher temperature, that is, the water temperature of the feed water entering the boiler is increased.

[0021] 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 steam inlet pipeline and is located upstream of the extraction isolation valve.

[0022] In the present scheme, the steam connected to the inlet of the boosting module at a pressure level lower than the target extraction pressure level is the final extraction steam of the high-pressure cylinder of the unit, that is, for the existing final high-pressure heater and extraction steam of the unit, the final extraction steam is pressurized by a steam compressor, and then enters the existing final high-pressure heater to heat the feed water. The inlet of the boosting module is connected to the steam inlet pipeline of the existing final high-pressure heater and is located upstream of the extraction steam isolation valve. Upstream of the extraction steam isolation valve, it is connected to the inlet of the boosting module, and the extraction steam isolation valve is closed. The final extraction steam of the high-pressure cylinder can enter the boosting module, and after being pressurized, it enters the existing final high-pressure heater to heat the feed water.

[0023] Preferably, a new steam extraction isolation valve is provided in the steam inlet pipeline, and the new steam extraction isolation valve is located at the front end of the heat exchanger upstream of the steam compressor.

[0024] In this solution, a new steam extraction isolation valve is provided in the steam inlet pipeline, and the new steam extraction isolation valve is located upstream of the heat exchanger upstream of the steam compressor. That is, when the steam with a pressure level lower than the target steam extraction pressure level connected to the inlet of the boosting module is the last-stage steam extraction of the high-pressure cylinder of the unit, a new steam extraction isolation valve is provided at the front end of the heat exchanger upstream of the steam compressor. When the heat exchanger and other equipment fail, the last-stage steam extraction of the high-pressure cylinder can be disconnected by closing the new steam extraction isolation valve, thereby ensuring the safety of system operation and improving the flexibility of system operation.

[0025] Preferably, the source of steam with a pressure level lower than the target extraction pressure level is heat recovery extraction steam in this unit or other units, steam in a reheat system, or steam in a superheater system.

[0026] 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.

[0027] Preferably, the number of valves of the regulating stage steam inlet valve group is four or six.

[0028] 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.

[0029] 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.

[0030] In this scheme, when the steam entering the existing last-stage high-pressure heater is pressurized by the booster module to increase the feed water temperature of the unit under deep peak-shaving conditions, the regulating-stage steam inlet valve group is used to throttle the main steam to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

[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] In this scheme, when the steam entering the existing final-stage high-pressure heater is pressurized by the booster module to increase the feed water temperature of the unit under deep peak-shaving conditions, a throttling component, such as a regulating valve, can also be set in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure.

[0033] The positive progressive effect of the present invention is that for a subcritical unit, its high-pressure cylinder adopts a partial steam intake method and is equipped with a regulating stage. On the basis of the existing boiler feed water heating system, a boosting module is added. Steam below the target extraction pressure level is pressurized by the boosting module and then enters the existing final-stage high-pressure heater. By increasing the pressure of the steam entering the existing final-stage high-pressure heater and maintaining a certain feed water pressure, the economizer outlet feed water maintains a certain degree of subcooling, which is used to increase the unit's feed water temperature under deep peak-shaving conditions, thereby increasing the economizer inlet water temperature, the economizer outlet water temperature, the economizer outlet flue gas temperature, and the drum outlet steam temperature, ultimately achieving continuous and stable operation of the unit's denitrification system under deep peak-shaving conditions, avoiding a substantial increase in the unit's energy consumption, and effectively improving the unit's operating economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of a system for heating boiler feed water in the prior art.

[0035] Figure 2 The present invention is a system schematic diagram of deep peak-shaving operation of a coal-fired power unit according to a preferred embodiment of the present invention (I).

[0036] Figure 3 The present invention is a system schematic diagram (II) of deep peak-shaving operation of a coal-fired power unit according to a preferred embodiment of the present invention.

[0037] Figure 4 This is a system schematic diagram (III) of deep peak-shaving operation of a coal-fired power unit according to a preferred embodiment of the invention.

[0038] Figure 5 This is a system schematic diagram (IV) of deep peak-shaving operation of a coal-fired power unit according to a preferred embodiment of the invention.

[0039] Figure 6 This is a system schematic diagram (V) of deep peak-shaving operation of a coal-fired power unit according to a preferred embodiment of the invention.

[0040] Figure 7 A system schematic diagram (VI) of deep peak-shaving operation of a coal-fired power unit is provided for the invention of a preferred embodiment.

[0041] Figure 8 The present invention is a system schematic diagram (VII) of deep peak-shaving operation of a coal-fired power unit according to a preferred embodiment of the present invention.

[0042] Fig. 9 A system schematic diagram (eight) of deep peak-shaving operation of a coal-fired power unit is provided for the invention of a preferred embodiment. DETAILED DESCRIPTION

[0043] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0044] Figure 1 The present invention is a schematic diagram of a system for heating boiler feed water in the prior art, wherein the system comprises a boiler, a deaerator 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 reaches the header through the downcomer and then returns to the steam drum after being heated by the water-cooled wall; the deaerator system comprises a deaerator, a pre-pump and a feed-water pump; 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 main steam pipeline, and an extraction steam isolating valve is provided on the steam intake 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.

[0045] 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.

[0046] In order to solve the above technical problems, the present invention adds a boosting module on the basis of the existing boiler feed water heating system, the inlet of the boosting module is connected to the steam lower than the target extraction pressure level, the outlet of the boosting module is connected to the steam inlet pipeline and is located downstream of the extraction isolation valve, when the steam lower than the target extraction pressure level is pressurized by the boosting module and enters the existing final high-pressure heater to heat the feed water, the extraction isolation valve is in a closed state upstream, cutting off the original high-pressure cylinder final extraction steam and directly entering the existing final high-pressure heater to heat the feed water; the steam entering the boosting module enters the existing final high-pressure heater after being pressurized by the boosting module, and the steam lower than the target extraction pressure level is pressurized by the steam compressor, and the pressure is higher than the pressure of the final extraction steam of the high-pressure cylinder. By increasing the pressure of the steam entering the existing final high-pressure heater, the unit's feed water temperature under deep peak regulation conditions is increased, and at the same time, a certain feed water pressure is maintained to keep a certain degree of subcooling of the economizer outlet feed water. 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.

[0047] Compared with the scheme of replacing the steam inlet of the final-stage high-pressure heater with the main steam after cooling and reducing the pressure, 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.

[0048] Example 1

[0049] Figure 2 This is a system schematic diagram of the deep peak-shaving operation of the coal-fired power unit in this embodiment. On the basis of the existing boiler feed water heating system, the present invention adds a boosting module, and a steam compressor is arranged in the pipeline of the boosting module. The inlet of the boosting module is connected to steam lower than the target extraction pressure level, and the outlet of the boosting module is connected to the steam inlet pipeline and is located downstream of the extraction isolation valve. By introducing steam lower than the target extraction pressure level into the boosting module, the steam is pressurized by the steam compressor and then enters the existing final-stage high-pressure heating heater to heat the feed water. After the steam lower than the target extraction pressure level is pressurized by the steam compressor, the pressure of the steam is higher than the pressure of the final-stage extraction of the high-pressure cylinder.

[0050] In this embodiment, the source of steam introduced at a pressure level lower than the target extraction pressure level is the final stage extraction steam of the high-pressure cylinder of the unit. The inlet of the boosting module is connected to the existing final stage high-pressure heated steam inlet pipeline and is located upstream of the extraction steam isolation valve, that is, a steam compressor is arranged in parallel between the inlet and outlet of the extraction steam isolation valve of the steam inlet pipeline. The final stage extraction steam of the high-pressure cylinder enters the boosting module, is pressurized by the steam compressor, and then enters the existing final stage high-pressure heater to heat the feed water, so as to increase the unit's inlet feed water temperature under deep peak regulation conditions.

[0051] Compared with the scheme of replacing the steam inlet of the final stage high-pressure heater with the main steam after cooling and reducing the pressure, this scheme can save the use of high-temperature and high-pressure pipelines, avoid the negative safety impact caused by the instantaneous change of the heat absorption ratio of the main steam and re-steam due to the use of the main steam, and the final stage extraction steam of this scheme has already done work in the steam turbine, and its thermal economy is better than that of the main steam that has not done work in the steam turbine. Therefore, this scheme has the advantages of relative safety, low cost, high flexibility in operation and regulation, and good economy.

[0052] When the unit is operated at partial load, when the pressure of the final stage extraction steam is increased by using the steam compressor, the extraction steam isolation valve on the steam inlet pipeline connected to the existing final stage high-pressure heater is in a closed state.

[0053] at the same time, Figure 2A regulating-stage steam inlet valve group is arranged on the middle main steam pipeline. The number of valves is 4. 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. What needs to be emphasized here is that after the boosting module is introduced to pressurize the final stage extraction steam and then enter the existing final stage high-pressure heater to heat the feed water to increase the unit's furnace feed water temperature under deep peak-shaving conditions, by operating the regulating stage steam inlet valve group, that is, using the original regulating stage steam inlet valve group to throttle the main steam, there is no need to add other regulating equipment to maintain a certain feed water pressure, so that the economizer outlet feed water maintains a certain degree of subcooling, which is used to increase the unit's furnace feed water temperature under deep peak-shaving conditions, thereby increasing the economizer inlet water temperature, economizer outlet water temperature, economizer outlet flue gas temperature, and drum outlet steam temperature, ultimately achieving continuous and stable operation of the unit's denitrification system under deep peak-shaving conditions, avoiding a substantial increase in the unit's energy consumption, and effectively improving the unit's operating economy. The main steam is throttled by the regulating stage steam inlet valve group to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain degree of subcooling; compared with the isenthalpic throttling method that simply uses valves without configuring the regulating stage, the regulating stage steam inlet valve group can achieve a certain steam enthalpy drop under the same pressure control effect on the main steam, and the unit economy is relatively improved. Moreover, since the flow rate of a single valve in the regulating stage steam inlet valve group is relatively small, the pressure control of the main steam will be more accurate and convenient. Of course, in other embodiments, a throttling component, such as a regulating valve, can be set in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain degree of subcooling.

[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 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 feed water pressure increases, the steam-water mixture pressure in the drum is also increased, the wet saturated steam temperature at the top of the drum is also increased, and the main steam temperature can be further increased; as the main steam temperature, the main steam volume and the ratio of the reheat steam volume increase, the cold re-steam and hot re-steam temperatures are both increased, which can avoid a significant increase in the unit's energy consumption and effectively improve the unit's operating economy.

[0056] Example 2

[0057] Figure 3 This is a system schematic diagram of deep peak-shaving operation of coal-fired power units 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 existing 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 middle heat exchanger is located on the steam inlet pipe connected to the existing final-stage high-pressure heater. Of course, the heat exchanger can also be set on the pipe of the boosting module, as long as the steam pressurized by the steam compressor is heat exchanged before entering the existing final-stage high-pressure heater. The steam pressurized by the steam compressor is first heat exchanged in the heat exchanger and then enters the existing final-stage high-pressure heater to heat the feed water. This can reduce the steam temperature entering the existing final-stage high-pressure heater and relatively increase the steam inlet flow rate of the existing final-stage high-pressure heater.

[0058] Take the data of a 300MW subcritical unit, whose high-pressure cylinder adopts partial steam admission, is equipped with a regulating stage, and is under 20% THA conditions as an example.

[0059] Existing plan: main generator load is 60MW, the existing final stage high pressure steam inlet parameters are 1.29MPa, 370℃ and outlet feed water parameters are 8.5MPa, 192℃, economizer outlet water temperature is 211℃, subcooling is 107.3℃, under-enthalpy is 521kJ / kg, economizer outlet flue gas temperature is 272℃, and the denitrification system cannot be put into use.

[0060] This implementation plan: the main generator load is 60MW, the existing final stage extraction parameters are 0.93MPa, 343℃, the existing final stage high-pressure steam inlet parameters after steam compressor supercharging and heat exchanger cooling are 3.8MPa, 395℃ and outlet feed water parameters are 10.3MPa, 248℃, economizer outlet water temperature is 269℃, subcooling is 44.2℃, under enthalpy is 242kJ / kg, economizer outlet flue gas temperature is 335℃, 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; at the same time, the regulating stage The inlet and outlet parameters are 206t / h, 9.8MPa, 529℃ and 206t / h, 2.46MPa, 439℃ respectively. The effective enthalpy drop per unit working fluid is 123.8kJ / kg, and the corresponding power is 7.1MW. Compared with the isenthalpic throttling method that simply uses valves without configuring a regulating stage, the regulating stage steam inlet valve group can achieve the same pressure control effect on the main steam, and the unit economy is relatively improved. Moreover, 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.

[0061] Example 3

[0062] Figure 4This is a system schematic diagram of deep peak load regulation operation of coal-fired power units in this embodiment. On the basis of Embodiment 1, a heat exchanger is added upstream of the steam compressor, and steam below the target extraction pressure level first enters the heat exchanger for heat exchange before entering the steam compressor; Figure 4 The heat exchanger is located on the steam inlet pipeline connected to the existing final high-pressure heater. Of course, the heat exchanger can also be set on the pipeline of the boosting module, as long as the heat exchanger is set upstream of the steam compressor. The final extraction steam enters the heat exchanger to heat the internal working medium of the heat exchanger, such as wind, water, coal, etc., and then enters the existing final high-pressure heater to heat the feed water after the steam is boosted by the steam compressor. In this way, the steam temperature entering the steam compressor can be reduced and the steam inlet flow rate of the existing final high-pressure heater can be relatively increased. At the same time, a new extraction steam isolation valve is set in the steam inlet pipeline connected to the existing final high-pressure heater, and the new extraction steam isolation valve is located at the front end of the heat exchanger upstream of the steam compressor. That is, when the steam lower than the target extraction pressure level connected to the inlet of the boosting module is the final extraction steam of the high-pressure cylinder of the unit, a new extraction steam isolation valve is set at the front end of the heat exchanger upstream of the steam compressor, so that when the heat exchanger and other equipment fail, the final extraction steam of the high-pressure cylinder is disconnected by closing the new extraction steam isolation valve, ensuring the safety of system operation and improving the flexibility of system operation.

[0063] Example 4

[0064] Figure 5 This is a system schematic diagram of the deep peak-shaving operation of the coal-fired power unit in this embodiment. On the basis of Example 1, heat exchangers are additionally provided upstream of the steam compressor and downstream of the steam compressor, and a new steam extraction isolation valve is provided in the steam inlet pipeline connected to the existing final-stage high-pressure heater. The new steam extraction isolation valve is located at the front end of the heat exchanger upstream of the steam compressor.

[0065] The final stage extraction steam enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then increases the pressure through the steam compressor. Then, it enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then enters the existing final stage high-pressure heater to heat the feed water. This can reduce the steam temperature entering the steam compressor, reduce the steam temperature entering the existing final stage high-pressure heater, and relatively increase the steam inlet flow rate of the existing final stage high-pressure heater. By performing two heat exchanges before and after the steam compressor, the cascade utilization efficiency of energy is improved.

[0066] Example 5

[0067] Figure 6This is a system schematic diagram of the deep peak-shaving operation of the coal-fired power unit in this embodiment. On the basis of Embodiment 1, the source of steam below the target extraction pressure level is optimized from the final stage extraction 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, which improves the operating flexibility of the unit while ensuring that the steam pressure at the outlet of the steam compressor is higher than the existing final stage extraction.

[0068] Example 6

[0069] Figure 7 This is a system schematic diagram of the deep peak-shaving operation of the coal-fired power unit in this embodiment. On the basis of Embodiment 5, the boosting module also includes a heat exchanger, and the heat exchanger is arranged downstream of the steam compressor. The steam at the steam compressor outlet enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then enters the existing final stage high-pressure heater to heat the feed water. In this way, the steam temperature entering the existing final stage high-pressure heater can be reduced and the steam inlet flow rate of the existing final stage high-pressure heater can be relatively increased.

[0070] Example 7

[0071] Figure 8 This is a system schematic diagram of the deep peak-shaving operation of the coal-fired power unit in this embodiment. On the basis of Example 5, the boosting module also includes a heat exchanger, which is arranged upstream of the steam compressor. Steam below the target extraction pressure level enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then is pressurized by the steam compressor before entering the existing final-stage high-pressure heater to heat the feed water. In this way, the steam temperature entering the steam compressor can be reduced and the steam inlet flow rate of the existing final-stage high-pressure heater can be relatively increased.

[0072] Example 8

[0073] Fig. 9 This is a system schematic diagram of the deep peak-shaving operation of the coal-fired power unit in this embodiment. On the basis of Example 5, heat exchangers are additionally provided upstream of the steam compressor and downstream of the steam compressor; before entering the steam compressor, the steam first enters the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then is pressurized by the steam compressor; after being pressurized by the steam compressor, the steam can also enter the heat exchanger to heat other working fluids, such as wind, water, coal, etc., and then enter the existing final-stage high-pressure heater to heat the feed water, thereby reducing the steam temperature entering the steam compressor, reducing the steam temperature entering the existing final-stage high-pressure heater, relatively increasing the steam inlet flow rate of the existing final-stage high-pressure heater, and improving the cascade utilization efficiency of energy.

[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 deep peak-shaving operation of a coal-fired power unit, comprising a boiler, a deaeration system, a high-pressure cylinder and an existing final-stage high-pressure heater, wherein the 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 via the downcomer, and then returned to the steam drum after being heated by the water-cooled wall; the high-pressure cylinder adopts a partial steam intake method and is 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 regulating-stage steam inlet valve group is provided on the main steam pipeline, and a steam extraction isolation valve is arranged on the steam inlet pipeline; characterized in that A boosting module is added, and the inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level. The outlet of the boosting module is connected to the steam inlet pipeline and is located downstream of the extraction isolation valve. The steam entering the boosting module enters the existing final-stage high-pressure heater after being pressurized in the boosting module, so as to increase the feed water temperature of the unit under deep peak-shaving conditions.

2. The system according to claim 1, characterized in that A steam compressor is arranged in the pipeline of the boosting module, and the steam compressor is used to boost the pressure of the steam entering the boosting module and having a pressure level lower than the target steam extraction pressure level.

3. The flexible operation system according to claim 2, characterized in that: 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 existing final-stage high-pressure heater; And / or, the boosting module further includes a heat exchanger, which is disposed upstream of the steam compressor, and the steam with a pressure level lower than the target extraction pressure level is first heat-exchanged in the heat exchanger before entering the existing final-stage high-pressure heater.

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

5. The flexible operation system according to claim 4, characterized in that: The 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. The inlet of the boosting module is connected to the existing final stage high pressure heated steam inlet pipeline and is located upstream of the extraction isolation valve.

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

7. The flexible operation system according to claim 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 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 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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