Deep peak regulation operation system of coal power unit based on water supply supplementary heating

Abstract

The invention discloses a deep peak regulation operation system of a coal power unit based on supplementary heating of feed water, which is characterized in that on the basis that an existing final-stage high-pressure heater is normally put into use to heat the feed water, a newly added final-stage high-pressure heater is arranged between a feed water inlet of a boiler and a feed water outlet of the existing final-stage high-pressure heater; a pressurizing module is connected to a steam inlet of the newly-added final-stage high-pressure heater, and steam lower than the target steam extraction pressure level enters the newly-added final-stage high-pressure heater after being pressurized; meanwhile, certain feed water pressure is maintained, so that feed water at an outlet of the economizer is kept at a certain supercooling degree, the in-furnace feed water temperature of a unit under the deep peak regulation working condition is increased, and then the water temperature of an inlet of the economizer, the water temperature of an outlet of the economizer, the smoke temperature of the outlet of the economizer and the steam temperature of an outlet of a steam pocket are increased; finally, the denitration system of the unit is continuously and stably put into operation under the working condition of deep peak regulation, the energy consumption of the unit is prevented from being greatly increased, and the operation economy of the unit is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation, and in particular to a deep peak-shaving operation system of a coal-fired power unit based on feedwater supplementary heating. Background Art

[0002] At present, high-parameter, large-capacity, high-efficiency and low-carbon ultra-supercritical units have become the mainstream of new 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 deep peak-shaving operation system for a coal-fired power unit based on supplementary feed water heating is provided.

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

[0011] The present invention provides a deep peak-shaving operation system of a coal-fired power unit based on feedwater supplementary heating, 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 sequentially connected through pipelines, and water at the bottom 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 mode and is equipped with a regulating stage; the feedwater inlet of the existing final-stage high-pressure heater is connected to the feedwater outlet of the deaeration system, the feedwater outlet of the existing final-stage high-pressure heater is connected to the feedwater inlet of the boiler, and the steam outlet of the boiler is connected to the high-pressure steam through the main steam pipeline Cylinder, the steam inlet of the existing final-stage high-pressure heater is connected with the steam extraction port of the high-pressure cylinder through a steam inlet pipe; a regulating-stage steam inlet valve group is provided on the main steam pipe, and a steam extraction isolation valve is arranged on the steam inlet pipe; and a 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, and the steam inlet of the newly added final-stage high-pressure heater is connected to a boosting module, and the inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level. The steam entering the boosting module is pressurized in the boosting module and then enters the newly added final-stage high-pressure heater to supplement the feed water for heating, so as to increase the feed water temperature of the unit under deep peak-shaving conditions.

[0012] In this scheme, for the subcritical unit, its high-pressure cylinder adopts a partial steam intake mode and is equipped with a regulating stage. On the basis of the unit's high-pressure cylinder final stage extraction steam entering the existing final stage high-pressure heater to heat the feed water, a new final stage high-pressure heater is set between the boiler's feed water inlet and the existing final stage high-pressure heater's feed water outlet, and a booster module is connected to the steam inlet of the new final stage high-pressure heater, and the inlet of the booster module is connected to steam with a pressure lower than the target extraction pressure level. The steam entering the booster module is pressurized in the booster module and then enters the new final stage high-pressure heater to supplement the feed water, so as to improve the unit's boiler feed water temperature under deep peak regulation conditions. 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. That is, on the basis of the existing final stage high-pressure heater being put into normal use to heat the feed water, the new final stage high-pressure heater introduces steam with a pressure lower than the target extraction pressure level through the connected booster module and pressurizes it to perform secondary heating or supplementary heating on the feed water again. 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.

[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 at a pressure level lower than the target steam extraction pressure level.

[0014] In this scheme, a steam compressor is arranged in the boosting module, and the steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor and then enters the newly added final-stage high-pressure heater to supplement the heating of the feed water. The steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor to have a pressure higher than the pressure of the final-stage extraction steam of the high-pressure cylinder, thereby ensuring that the steam pressure after being compressed by the steam compressor and then entering the newly added final-stage high-pressure heater is higher than the pressure of the final-stage extraction steam originally entering the existing final-stage high-pressure heater, thereby ensuring that the feed water is heated to a higher temperature, that is, the feed water temperature entering the furnace is increased to increase the feed water temperature entering the furnace of the unit under deep peak regulation conditions.

[0015] 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.

[0016] In this solution, a new steam extraction isolation valve is provided in the boosting module, and the new steam extraction isolation valve is provided at the front end or rear end of the steam compressor. The new steam extraction isolation valve is used to adjust the fluid flow entering the boosting module. In addition, when equipment such as the steam compressor or the new final-stage high-pressure heater fails, part of the final-stage steam extraction from the high-pressure cylinder entering the boosting module can be disconnected by closing the new steam extraction isolation valve, thereby ensuring the safety of system operation and improving the flexibility of system operation.

[0017] 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;

[0018] 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 newly added final-stage high-pressure heater.

[0019] 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.

[0020] 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.

[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 to introduce part of the final stage extraction steam of the high pressure cylinder.

[0022] 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.

[0023] Preferably, the inlet of the boosting module is located upstream of the steam extraction isolation valve.

[0024] 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.

[0025] 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.

[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 newly added final-stage high-pressure heater is pressurized by the booster module to increase the unit's boiler feed water temperature under deep peak-shaving conditions, the regulating-stage steam inlet valve group is used to throttle the main steam to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

[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 newly added 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 and 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 normal use of the existing final-stage high-pressure heater to heat the feed water, a new final-stage high-pressure heater is arranged between the feed water inlet of the boiler and the feed water outlet of the existing final-stage high-pressure heater, and a boosting module is connected to the steam inlet of the new final-stage high-pressure heater, and the inlet of the boosting module is connected to steam below the target extraction pressure level. The steam below the target extraction pressure level enters the new final-stage high-pressure heater after pressurization, and at the same time, a certain feed water pressure is maintained so that the economizer outlet feed water maintains a certain degree of subcooling, so as to increase the unit's furnace feed water temperature under deep peak regulation conditions, thereby increasing the economizer inlet water temperature, the economizer outlet water temperature, the economizer outlet flue gas temperature, and the drum outlet steam temperature, and finally achieving the unit's denitrification system under deep peak regulation conditions. Continuous and stable operation, avoid a substantial increase in unit energy consumption, and effectively improve 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 schematic diagram of a deep peak-shaving operation system of a coal-fired power unit based on supplementary heating of feed water in accordance with a preferred embodiment of the present invention (I).

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

[0037] Figure 4 The present invention is a schematic diagram of a deep peak-shaving operation system of a coal-fired power unit based on supplementary heating of feed water in a preferred embodiment (III).

[0038] Figure 5 The present invention is a schematic diagram of a deep peak-shaving operation system of a coal-fired power unit based on supplementary heating of feed water in accordance with a preferred embodiment of the present invention (IV).

[0039] Figure 6 The present invention is a schematic diagram of a deep peak-shaving operation system of a coal-fired power unit based on supplementary heating of feed water in accordance with a preferred embodiment of the present invention (V).

[0040] Figure 7 The present invention is a schematic diagram of a deep peak-shaving operation system of a coal-fired power unit based on supplementary heating of feed water in accordance with a preferred embodiment of the present invention (VI).

[0041] Figure 8 The present invention is a schematic diagram of a deep peak-shaving operation system of a coal-fired power unit based on supplementary heating of feed water in accordance with a preferred embodiment of the present invention (VII).

[0042] Fig. 9The present invention is a schematic diagram of a deep peak-shaving operation system of a coal-fired power unit based on supplementary heating of feed water in accordance with a preferred embodiment of the present invention (VIII). 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, on the basis of the normal use of the existing final-stage high-pressure heater to heat the feed water, a new final-stage high-pressure heater is arranged between the feed water inlet of the boiler and the feed water outlet of the existing final-stage high-pressure heater, and the boosting module is connected to the steam inlet of the new final-stage high-pressure heater, and the inlet of the boosting module is connected to steam lower than the target extraction pressure level. The steam entering the boosting module is pressurized in the boosting module and then enters the new final-stage high-pressure heater for additional heating of the feed water, so as to increase the feed water temperature entering the furnace of the unit under deep peak regulation conditions, while maintaining a certain feed water pressure, and keeping the feed water at the economizer outlet at a certain degree of subcooling. Among them, the steam of the target extraction pressure level can be understood as the steam that directly enters the existing final-stage high-pressure heater to heat the feed water to the required temperature if the boiler feed water heating system in the prior art is adopted, that is, without setting the boosting module; the extraction steam source below the target extraction pressure level can be the final-stage extraction steam of the high-pressure cylinder of this unit, or other heat recovery extraction steam or superheater system steam or reheat system steam of this unit, or heat recovery extraction steam or superheat system steam or reheat system steam of other units, or the aforementioned steam and other relatively low-pressure steam, such as a mixture of unit heat recovery extraction steam, reheat steam, etc.

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

[0050] A steam compressor is provided in the boosting module, and the steam compressor is used to boost the steam entering the boosting module which is lower than the target extraction pressure level. The steam lower than the target extraction pressure level is pressurized by the steam compressor and then introduced into the newly added final-stage high-pressure heater for supplementary heating of the feed water. The pressure of the steam lower than the target extraction pressure level after being boosted by the steam compressor is higher than the pressure of the final-stage extraction steam of the high-pressure cylinder, thereby ensuring that the steam pressure entering the newly added final-stage high-pressure heater after being compressed by the steam compressor is higher than the pressure of the final-stage extraction steam originally entering the existing final-stage high-pressure heater, thereby ensuring that the feed water is heated to a higher temperature, that is, the water temperature of the feed water entering the furnace is increased to increase the feed water temperature entering the furnace of the unit under deep peak-shaving conditions.

[0051] 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.

[0052] When the unit is operating at partial load, the final-stage extraction steam of the existing final-stage high-pressure heater is put into normal use to heat the feed water. In the booster module, the steam compressor increases the pressure of part of the final-stage extraction steam and sends it to the newly added final-stage high-pressure heater for additional heating of the feed water. At the same time, the main steam is throttled to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

[0053] 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 booster module is introduced to pressurize the final stage extraction steam and then enter the newly added final stage high-pressure heater to supplement the heating of the feed water to increase the unit's furnace feed water temperature under deep peak-shaving conditions, the regulating stage steam inlet valve group is operated and the original regulating stage steam inlet valve group is used 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. Compared with the isenthalpic throttling method of simply using valves without configuring the regulating stage, the regulating stage steam inlet valve group can achieve a certain steam enthalpy drop under the same pressure control effect for the main steam, and the unit economy is relatively improved. Moreover, since the flow rate of a single valve in the regulating stage steam inlet valve group is relatively small, the pressure control of the main steam will be more accurate and convenient. Of course, in other embodiments, a throttling component, such as a regulating valve, can be set in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

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

[0055] The feed water temperature of the unit can be increased to 75% THA or even 100% THA.

[0056] As the temperature of the unit's inlet water 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 further the main steam temperature can also be increased; as the main steam temperature, the main steam volume and the ratio of the reheat steam volume increase, the cold reheat steam and hot reheat steam temperatures both increase, which can avoid a substantial increase in the unit's energy consumption and effectively improve the unit's operating economy. Example 2

[0057] Figure 3This is a schematic diagram of the deep peak-shaving operation system of the coal-fired power unit based on supplementary heating of feed water in this embodiment. On the basis of Example 1, a heat exchanger is added downstream of the steam compressor. The steam below the target extraction pressure level is pressurized by the steam compressor, and then enters the newly added final-stage high-pressure heater after heat exchange with the working fluid inside the heat exchanger. The other working fluid in the heat exchanger can be wind, water, coal, etc. The heat exchanger is located on the pipeline of the boosting module, and the steam pressurized by the steam compressor is first heat exchanged in the heat exchanger before entering the newly added final-stage high-pressure heater to heat 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 existing final-stage high-pressure heater can be relatively increased.

[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 solution: 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 107.3℃, under-enthalpy 521kJ / kg), economizer outlet flue gas temperature is 272℃, and the denitrification system cannot be put into use.

[0060] The scheme of this embodiment: the load of the main generator is 60MW, the existing final stage extraction parameters are 0.96MPa, 346℃, the new final stage high-pressure steam inlet parameters after steam compressor supercharging and heat exchanger cooling are 3.9MPa, 398℃ and the outlet feed water parameters are 10.6MPa, 249℃, the economizer outlet water temperature is 271℃, the subcooling degree is 44.3℃, the under enthalpy is 245kJ / kg, the economizer outlet flue gas temperature is 337℃, 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 203t / h, 10.1MPa, 531℃ and 203t / h, 2.47MPa, 442℃ respectively. The effective enthalpy drop per unit working fluid is 119.1kJ / kg, and the corresponding power is 6.7MW. 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 4 This is a schematic diagram of a deep peak-shaving operation system of a coal-fired power unit based on feedwater supplementary heating in this embodiment. On the basis of Embodiment 1, the boosting module further includes a heat exchanger, which is arranged upstream of the steam compressor. Figure 4The 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.

[0063] Example 4

[0064] Figure 5 This is a schematic diagram of the deep peak-shaving operation system of the coal-fired power unit based on supplementary heating of feed water in this embodiment. On the basis of Example 1, in the boosting module, heat exchangers are arranged upstream and downstream of the steam compressor, and part of the final extraction steam of the high-pressure cylinder first enters the heat exchanger, where it can heat other working fluids such as wind, water, coal, etc., and then it is boosted by the steam compressor. Then it enters the heat exchanger located downstream of the steam compressor to heat other working fluids such as wind, water, coal, etc., and then enters the newly added final high-pressure heater to heat the feed water. In this way, the steam temperature entering the steam compressor 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. By performing two heat exchanges before and after the steam compressor, the step-by-step utilization efficiency of energy is improved.

[0065] Example 5

[0066] Figure 6 This is a schematic diagram of the deep peak-shaving operation system of the coal-fired power unit based on feed water supplementary heating in this embodiment. On the basis of Example 1, the source of steam below the target extraction pressure level is optimized from the final stage extraction steam to other heat recovery extraction steam or superheater system steam or reheater system steam of this unit or heat recovery extraction steam or superheater system steam or reheater system steam of other units, which improves the operating flexibility of the unit while satisfying the premise that the steam pressure at the outlet of the steam compressor is higher than the existing final stage extraction steam.

[0067] Example 6

[0068] Figure 7This is a schematic diagram of the deep peak-shaving operation system of the coal-fired power unit based on supplementary heating of feed water in this embodiment. On the basis of Example 5, the boosting module also includes a heat exchanger, which is arranged downstream of the steam compressor. In the pipeline of the boosting module, the steam compressor, the newly added steam extraction isolation valve, and the heat exchanger are arranged in sequence. The steam below the target steam extraction pressure level is pressurized by the steam compressor, and then heat exchanged in the heat exchanger before entering the newly added final-stage high-pressure heater; the steam below the target steam extraction pressure level enters the boosting module, is pressurized by the steam compressor, and then enters the heat exchanger to heat other working media, 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.

[0069] Example 7

[0070] Figure 8 This is a schematic diagram of the deep peak-shaving operation system of the coal-fired power unit based on supplementary heating of feed water in this embodiment. On the basis of Example 5, the boosting module also includes a heat exchanger, and the heat exchanger is arranged upstream of the steam compressor. In the pipeline of the boosting module, the heat exchanger, the steam compressor, and the newly added steam extraction isolation valve are connected and arranged in sequence. The steam below the target steam extraction pressure level first enters the heat exchanger to heat other working media, such as wind, water, coal, etc., and then is pressurized by the steam compressor. Finally, it enters the newly added last-stage high-pressure heater to supplement the feed water for heating. In this way, the steam temperature entering the steam compressor can be reduced and the steam inlet flow rate of the newly added last-stage high-pressure heater can be relatively increased.

[0071] Example 8

[0072] Fig. 9 This is a schematic diagram of the deep peak-shaving operation system of the coal-fired power unit based on supplementary heating of feed water in this embodiment. The boosting module also includes a heat exchanger, and heat exchangers are added upstream of the steam compressor and downstream of the steam compressor. Before entering the steam compressor, the steam below the target extraction pressure level first enters the heat exchanger located upstream of the steam compressor to heat other working fluids, such as wind, water, coal, etc., and then is pressurized by the steam compressor; after being pressurized by the steam compressor, it enters the heat exchanger located downstream of the steam compressor to heat other working fluids, such as wind, water, coal, etc., and then enters the newly added final-stage high-pressure heater to heat the feed water. In this way, the steam temperature entering the steam compressor, the steam temperature entering the newly added final-stage high-pressure heater, the steam inlet flow rate of the newly added final-stage high-pressure heater can be relatively increased, and the step-by-step utilization efficiency of energy can be improved.

[0073] 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 deep peak-shaving operation system of a coal-fired power unit based on feedwater supplementary heating, 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 partial steam intake method and is equipped with a regulating stage; the feedwater inlet of the existing final-stage high-pressure heater is connected to the feedwater outlet of the deaeration system, the feedwater outlet of the existing final-stage high-pressure heater is connected to the feedwater 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 new final-stage high-pressure heater is arranged between the feed water inlet of the boiler and the feed water outlet of the existing final-stage high-pressure heater, and the steam inlet of the new final-stage high-pressure heater is connected to a boosting module. The inlet of the boosting module is connected to steam with a pressure level lower than the target extraction pressure level. The steam entering the boosting module is pressurized in the boosting module and then enters the new final-stage high-pressure heater to supplement the feed water for heating, so as to increase the feed water temperature of the unit under deep peak-shaving conditions.

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

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

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

7. The deep peak load regulation 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 deep peak load regulation 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 deep peak-shaving operation system according to any one of claims 1 to 8, characterized in that: The deep peak load regulation operation system is configured to throttle the main steam by utilizing the regulating stage steam inlet valve group to maintain a certain feed water pressure and keep the economizer outlet feed water at a certain degree of subcooling.

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

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