1. The utility model provides a steam that realization denitration was raised temperature mixes system of disposition, its characterized in that: the system comprises a driving steam isolation unit, a steam mixing device (101), a high-pressure heater (102) and an economizer (103) which are sequentially connected through a steam pipeline, wherein the steam pipeline is provided with a pressure and temperature detection device, an inlet of the steam pipeline is connected with a low-temperature low-pressure steam pipeline, the high-pressure heater (102) is connected with a high-temperature high-pressure steam pipeline, an injection port of the steam mixing device (101) is connected with the high-temperature high-pressure steam pipeline through the steam pipeline, the steam mixing device (101) is connected with a driving steam adjusting unit in parallel, feed water passes through the high-pressure heater (102) and then is heated by the economizer (103) to flow out, and boiler flue gas enters a denitration System (SCR) denitration system after passing through the economizer (103); the driving steam isolation unit comprises a driving steam electric isolation valve (201) and a driving steam constant-heating pipe bypass valve (202), and the driving steam electric isolation valve (201) and the driving steam constant-heating pipe bypass valve (202) are connected in parallel; the driving steam adjusting unit comprises a driving steam bypass electric adjusting valve (206) and a driving steam bypass temperature and pressure reducing device (207), and the driving steam bypass electric adjusting valve (206) and the driving steam bypass temperature and pressure reducing device (207) are connected in series.

2. The steam mixing system for realizing denitration and temperature increase of the denitration and temperature increase device of claim 1, wherein: and a second high-pressure heater steam inlet electric isolating valve (205) is arranged between the injection port of the steam mixing device (101) and the high-pressure heater (102).

3. The steam mixing system for realizing denitration and temperature increase of the denitration and temperature increase device of claim 1, wherein: and a driving steam electric regulating valve (203) is arranged at the inlet of the steam mixing device (101).

4. The steam mixing system for realizing denitration and temperature increase of the denitration and temperature increase device of claim 1, wherein: an injection port of the steam mixing device (101) is provided with an injected steam electric isolation valve (204).

5. The steam mixing system for realizing denitration and temperature increase of the denitration and temperature increase device of claim 1, wherein: the high-temperature high-pressure steam pipeline is provided with a high-pressure heater steam inlet pneumatic check valve (208) and a high-pressure heater steam inlet electric isolating valve (209).

6. A steam adjusting method for realizing denitration and temperature raising comprises the following steps: a steam compounding system comprising the steam compounding system of any one of claims 1 to 5, adjusted as follows: the controller automatically selects different operation modes according to different working conditions of the unit of the power generation system during load operation by combining the required temperature of the inlet of the denitration System (SCR) and the actual temperature of the inlet of the denitration System (SCR) so as to adjust the temperature of the output feed water when the feed water passes through the economizer, thereby absorbing the heat of low-temperature flue gas, reducing the temperature of the flue gas, reducing the loss of the flue gas, saving fuel, adapting to the load change,

(1) after the unit is connected to the grid, a temperature and pressure reduction mode is put into operation at a load rate of 25%;

(2) when the unit is put into operation in a steam mixing mode within the range of 25% to 40% of load rate;

(3) and when the load rate of the unit is more than 40%, the original steam inlet mode is put into operation.

7. A steam conditioning method according to claim 6, characterized in that: the main configuration of the temperature and pressure reduction mode comprises the following steps: a high-pressure heater (102), a drive steam electric isolation valve (201), a drive steam constant-heating pipe bypass valve (202), a drive steam electric regulating valve (203), a second high-pressure heater steam inlet electric isolation valve (205), a drive steam bypass electric regulating valve (206) and a drive steam bypass temperature and pressure reduction device (207) which are connected through a steam pipeline, when the mode is operated, the steam inlet electric isolating valve (205) of the second high-pressure heater is closed and the steam electric regulating valve (203) is driven, the controller controls the opening of the steam-driven electric isolating valve (201) and the steam-driven normal heating pipe bypass valve (202), the opening degree of the steam bypass electric adjusting valve (206) is adjusted and driven, and the steam bypass temperature and pressure reducing device (207) is driven to reduce the temperature and the pressure of the steam and then the steam passes through the high-pressure heater (102) to increase the temperature of the water supply to the economizer (103).

8. A steam conditioning method according to claim 6, characterized in that: the steam mixing mode mainly comprises the following configurations: the steam mixing device comprises a steam mixing device (101), a high-pressure heater (102), a driving steam electric isolation valve (201), a driving steam normally-heated pipe bypass valve (202), a driving steam electric adjusting valve (203), an injected steam electric isolation valve (204), a second high-pressure heater steam inlet electric isolation valve (205) and a driving steam bypass electric adjusting valve (206) which are connected through a steam pipeline, wherein when the steam mixing device operates in the mode, the second high-pressure heater steam inlet electric isolation valve (205) and the driving steam bypass electric adjusting valve (206) are closed, the driving steam electric isolation valve (201), the driving steam normally-heated pipe bypass valve (202) and the injected steam electric isolation valve (204) are opened, the temperature and the pressure of an inlet of the mixing steam device (101) meet the mixing requirement by adjusting the opening degree of the driving steam electric adjusting valve (203), and mixed steam discharged from an outlet of the mixing steam device (101) passes through the high-pressure heater (102), to increase the temperature of the feedwater to the economizer (103).

9. A steam conditioning method according to claim 6, characterized in that: the main configuration of the original steam inlet mode comprises the following steps: the high-pressure steam economizer comprises a high-pressure heater (102), a driving steam electric isolation valve (201), a driving steam normal-heating pipe bypass valve (202), an injected steam electric isolation valve (204), a second high-pressure heater steam inlet electric isolation valve (205), a high-pressure heater steam inlet pneumatic check valve (208) and a high-pressure heater steam inlet electric isolation valve (209) which are connected through a steam pipeline, when the high-pressure steam economizer operates in the mode, the driving steam electric isolation valve (201), the driving steam normal-heating pipe bypass valve (202) and the injected steam electric isolation valve (204) are closed, the second high-pressure heater steam inlet electric isolation valve (205), the high-pressure heater steam inlet pneumatic check valve (208) and the high-pressure heater steam inlet electric isolation valve (209) are opened, and raw steam directly passes through the high-pressure heater (102) through a high-temperature steam pipeline so as to improve the water supply temperature of the coal economizer (103).

Background

Under the current form, renewable energy is rapidly developed, and the demand of the adjustable capacity of the power system is increased sharply based on the characteristic of intermittent power generation of clean energy. The conventional thermal power generating unit is required to bear the peak shaving obligation of the whole power system besides providing the stable power supply function. In recent years, when renewable energy is rapidly developed, serious phenomena of wind abandoning and light abandoning occur, and consumption of new energy becomes a key factor for restricting the development of the renewable energy; based on the energy consumption rule of China, the proportion of clean energy is increasing day by day, and the absorption forms of wind power and photovoltaic are becoming more severe; in addition, under the adjustment of national industrial structure, the peak-valley difference of the electrical load is increased, the cogeneration is continuously increased, the peak regulation difficulty is aggravated in the heating period, the peak regulation power supply construction conditions of most provinces are limited, the flexibility of the sending channel is poor, and the flexible power supply is still in shortage. The method realizes deep peak regulation and improves the operation flexibility of the unit, and becomes a necessary condition for determining the survival of thermal power enterprises.

For the boiler side (including environmental protection), the peak regulation capability of the unit is influenced by the configuration of equipment and a system, wherein the problem of unit wide-load denitration is more prominent. For most units, the load can be guaranteed to be above 40%, the flue gas temperature is higher than 300 ℃, but for part of special furnace types or special coal types, the problems that the flue gas temperature of denitration low load is too low and normal operation cannot be realized exist, and further load reduction operation of the units cannot be realized.

The reason for the problem of low-load denitration is analyzed, and the biggest problem of full-working-condition denitration lies in that the temperature required by a catalyst of a low-load deep peak shaving (below 40% rated load) of a unit cannot be met when the unit operates, so that a denitration System (SCR) cannot be normally put into operation, and the standard emission of NOx in a boiler is influenced. The existing technology for solving the problem of low-load smoke temperature mainly comprises an economizer water supply bypass, an economizer recirculation and a smoke bypass, and has the following main technical characteristics and defects:

firstly, a water supply bypass technology of an economizer. According to the technology, water flow entering the economizer is reduced by supplying water through the bypass part, so that the heat exchange quantity of the economizer is reduced, the temperature of flue gas at the outlet of the economizer is increased, and the temperature of flue gas at the inlet of a denitration device is increased. The smoke temperature rise is generally not greater than 15 ℃. The economizer water supply bypass technology has the advantages of limited temperature raising range, high possibility of vaporization overtemperature due to the temperature of a suspension pipe at the outlet of the economizer and large required modification site.

And II, a coal economizer recycling technology. The technology is that a recirculation pipeline is led out from a proper height position of a boiler downcomer and is pressurized by a newly-added recirculation pump and led into a water supply pipeline so as to improve the water temperature at the inlet of the economizer and reduce the heat transfer temperature difference between the water side and the flue gas side of the economizer, thereby achieving the purposes of reducing the heat absorption capacity of the economizer and improving the temperature of the flue gas at the outlet of the economizer. The inlet smoke temperature of a denitration System (SCR) can be increased to be more than 15 ℃. The coal economizer recycling technology has large subsequent maintenance amount of equipment and high investment cost.

And thirdly, flue gas bypass technology. According to the technology, a hole is formed in a flue at the inlet (or a low inlet) of an economizer, a part of flue gas is pumped to a denitration System (SCR) interface, a flue gas baffle is arranged, and a part of steel structures are added. And at low load, the flue gas from the outlet of the economizer or the (lower + economizer) is heated by extracting the flue gas, so that the temperature of the flue gas at the inlet of the denitration System (SCR) at low load is higher than the lower limit value of the temperature of the denitration reaction window. The inlet smoke temperature of a denitration System (SCR) can be increased to be more than 15 ℃. The flue gas bypass technology has the advantages of easy blocking of the baffle door, poor load adaptability and high investment cost.

Based on the reasons, in order to meet the actual production requirements, a steam mixing system for realizing denitration and temperature raising is provided.

Disclosure of Invention

The invention provides a steam mixing system for realizing denitration and temperature raising, which is used for improving the peak regulation capacity and the unit operation flexibility of a thermal power enterprise unit, realizing denitration full-load regulation and having strong capacity of adapting to load change.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the utility model provides a realize denitration and carry steam of temperature and join in marriage system of joining in marriage, includes that drive steam that connects gradually through steam piping keeps apart unit, steam blending device, high pressure heater and economizer, steam piping is equipped with pressure and temperature-detecting device, and steam piping entry links to each other with low temperature low pressure steam pipeline, and high pressure heater is connected with high temperature high pressure steam pipeline, and steam blending device's draw mouthful to pass through steam piping and links to each other with high temperature high pressure steam pipeline, and steam blending device has parallelly connected drive steam regulation unit, and the steam passes through high pressure heater after the economizer heating outflow, and the boiler flue gas gets into deNOx Systems (SCR) deNOx systems behind the economizer.

Furthermore, the drive steam isolation unit comprises a drive steam electric isolation valve and a drive steam normally-heated pipe bypass valve, and the drive steam electric isolation valve and the drive steam normally-heated pipe bypass valve are connected in parallel.

Furthermore, drive steam governing unit is including drive steam bypass electric control valve and drive steam bypass temperature and pressure reducer, drive steam bypass electric control valve and drive steam bypass temperature and pressure reducer concatenate.

Furthermore, a second high-pressure heater steam inlet electric isolating valve is arranged between an injection port of the steam mixing device and the high-pressure heater.

Furthermore, a driving steam electric regulating valve is arranged at the inlet of the steam mixing device.

Furthermore, an injection port of the steam mixing device is provided with an injected steam electric isolating valve.

Furthermore, the high-temperature high-pressure steam pipeline is provided with a high-pressure heater steam inlet pneumatic check valve and a high-pressure heater steam inlet electric isolating valve.

The invention also provides a steam adjusting method for realizing denitration and temperature raising, which comprises the following steps: according to the unit input load operation condition of the power generation system, different operation modes are automatically selected by the controller to adjust the temperature of the output feed water when the feed water passes through the economizer, so that the heat of low-temperature flue gas is absorbed, the temperature of the flue gas is reduced, the flue gas loss is reduced, the fuel is saved, the power generation system adapts to the load change,

(1) after the unit is connected to the grid, a temperature and pressure reduction mode is put into operation at a load rate of 25%;

(2) when the unit is put into operation in a steam mixing mode within the range of 25% to 40% of load rate;

(3) when the load rate of the unit is more than 40%, the original steam inlet mode is put into operation;

further, the main configuration of the temperature and pressure reduction mode comprises: the high-pressure heater is connected through a steam pipeline, the steam electric isolation valve is driven, the steam normal heating pipe bypass valve is driven, the steam electric adjusting valve is driven, the steam inlet electric isolation valve of the second high-pressure heater, the steam bypass electric adjusting valve is driven and the steam bypass temperature and pressure reducer is driven.

Further, the steam compounding mode main configuration comprises: the steam mixing device comprises a steam mixing device, a high-pressure heater, a driving steam electric isolation valve, a driving steam normally-heated pipe bypass valve, a driving steam electric regulating valve, an injected steam electric isolation valve, a second high-pressure heater steam inlet electric isolation valve and a driving steam bypass electric regulating valve which are connected through a steam pipeline.

Further, the main configuration of the original steam inlet mode comprises: the high-pressure steam heater, the driving steam electric isolating valve, the driving steam normal-heating pipe bypass valve, the injected steam electric isolating valve, the second high-pressure heater steam inlet electric isolating valve, the high-pressure heater steam inlet pneumatic check valve and the second high-pressure heater steam inlet electric isolating valve are connected through a steam pipeline.

Due to the adoption of the structure, compared with the prior art, the invention has the technical progress that: according to different working conditions of the unit of the power generation system during load operation, the steam mixing system provided by the invention can select three different modes, namely a temperature reduction and pressure reduction mode, a steam mixing mode and an original steam inlet mode, according to different working conditions of the unit of the power generation system during load operation, and the required temperature of the inlet of the denitration System (SCR) and the actual temperature of the inlet of the denitration System (SCR), so that the steam mixing system can be matched with the low, medium and high load rates of the power generation set to operate, free switching and continuous adjustment can be realized, and during low load rate, driving steam enters a high-pressure heater to heat feed water after passing through a driving steam isolation unit and a driving steam adjustment unit; when the load factor is medium, the driving steam enters the high-pressure heater to heat the feed water after passing through the driving steam isolation unit and the steam mixing device, and when the load factor is high, the high-temperature high-pressure steam can be introduced to be mixed and then enters the high-pressure heater as a new heat source to heat the feed water, so that the heating efficiency is further improved; when the load factor is high, steam can directly enter the high-pressure heater through the high-temperature high-pressure steam pipeline to heat the feed water; through the three different modes, free switching and continuous adjustment are realized, denitration full-load section adjustment can be realized, operation adjustment is flexible, the capacity of adapting to load change is strong, a denitration System (SCR) meets full-load section operation of a unit under high, medium and low loads, the feed water temperature when the unit finally passes through the economizer is adjusted, and then the purposes of reducing the heat absorption capacity of the economizer, improving the temperature of flue gas at the outlet of the economizer and adjusting the inlet temperature of the SCR are achieved.

1. Through the steam mixing system, the controller selects and adopts three different modes, namely a temperature reduction and pressure reduction mode, a steam mixing mode and an original steam inlet mode according to different working conditions of the unit of the power generation system during load operation and the actual temperature of the inlet of the denitration System (SCR), realizes free switching and continuous adjustment, can realize adjustment of a denitration full load section, is flexible in operation adjustment and strong in load change adapting capability, so that the denitration System (SCR) can meet the full load section operation of the unit under high, medium and low loads, and can immediately adjust the inlet temperature of the (SCR) after the unit is connected to the grid;

2. the driving steam is taken from the steam of a low-temperature low-pressure pipeline, the pressure is ensured, the temperature is lower, the safety and the reliability are realized, a small amount of steam mixing device is utilized to inject low-parameter steam as the driving steam, high-temperature high-pressure steam is introduced through an injection port to be mixed, the pressure of the driving steam is improved, the mixed steam is used as a new heat source to enter a corresponding high-pressure heater to carry out water supply heating, the steam inlet parameter of the high-pressure heater is improved, the steam inlet quantity can be further improved, the water supply temperature when the driving steam finally passes through the economizer is adjusted, the purposes of reducing the heat absorption quantity of the economizer and improving the smoke temperature of the outlet of the economizer are further achieved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

In the drawings:

FIG. 1 is a schematic structural diagram of an embodiment of the present invention;

FIG. 2 is a control flow diagram of the present invention;

FIG. 3 is a diagram of the full-scale denitration commissioning mode of the present invention.

Labeling components: the system comprises a steam mixing device-101, a high-pressure heater-102, an economizer-103, a driving steam electric isolation valve-201, a driving steam normally-heated pipe bypass valve-202, a driving steam electric regulating valve-203, an injected steam electric isolation valve-204, a second high-pressure heater steam inlet electric isolation valve-205, a driving steam bypass electric regulating valve-206, a driving steam bypass temperature-reducing pressure reducer-207, a high-pressure heater steam inlet pneumatic check valve-208 and a high-pressure heater steam inlet electric isolation valve-209.

Detailed Description

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for purposes of illustration and explanation only and are not intended to limit the present invention.

The invention discloses a steam mixing system for realizing denitration and temperature increase, which comprises a driving steam isolation unit, a steam mixing device (101), a high-pressure heater (102) and an economizer (103) which are sequentially connected through a steam pipeline, wherein the steam pipeline is provided with a pressure and temperature detection device, the inlet of the steam pipeline is connected with a low-temperature low-pressure steam pipeline, the high-pressure heater (102) is connected with a high-temperature high-pressure steam pipeline, the injection port of the steam mixing device (101) is connected with the high-temperature high-pressure steam pipeline through the steam pipeline, the steam mixing device (101) is connected with a driving steam adjusting unit in parallel, feed water passes through the high-pressure heater (102) and then is heated by the economizer (103) to flow out, and boiler flue gas passes through the economizer (103) and then enters a denitration System (SCR) denitration system. The driving steam isolation unit comprises a driving steam electric isolation valve (201) and a driving steam normally-heated pipe bypass valve (202), and the driving steam electric isolation valve (201) and the driving steam normally-heated pipe bypass valve (202) are connected in parallel. The driving steam adjusting unit comprises a driving steam bypass electric adjusting valve (206) and a driving steam bypass temperature and pressure reducing device (207), and the driving steam bypass electric adjusting valve (206) and the driving steam bypass temperature and pressure reducing device (207) are connected in series.

The invention has the beneficial effects that: according to the steam mixing system provided by the invention, according to different working conditions of the unit of the power generation system during load operation, the required temperature of the inlet of the denitration System (SCR) and the actual temperature of the inlet of the denitration System (SCR) are combined, three different modes, namely a temperature and pressure reduction mode, a steam mixing mode and an original steam inlet mode, are selected to be adopted, the steam mixing system is matched with the low load rate, the medium load rate and the high load rate of a generator set to operate, free switching and continuous adjustment are realized, and during the low load rate, driving steam enters the high-pressure heater (102) to heat feed water after passing through the driving steam isolation unit and the driving steam adjustment unit; when the load factor is medium, the driving steam enters the high-pressure heater (102) to heat the feed water after passing through the driving steam isolation unit and the steam mixing device (101), and simultaneously, the high-temperature high-pressure steam can be introduced to be mixed and then enters the high-pressure heater to heat the feed water as a new heat source, so that the heating efficiency is further improved; when the load factor is high, steam can directly enter the high-pressure heater (102) through a high-temperature high-pressure steam pipeline to heat feed water; through the three different modes, free switching and continuous adjustment are realized, denitration full-load section adjustment can be realized, operation adjustment is flexible, the capacity of adapting to load change is strong, a denitration System (SCR) can meet the full-load section operation of a unit under high, medium and low loads, the feed water temperature when the denitration system finally passes through the economizer (103) is adjusted, and then the purposes of reducing the heat absorption capacity of the economizer (103), improving the temperature of flue gas at the outlet of the economizer (103) and adjusting the inlet temperature of the denitration System (SCR) are achieved.

1. Through the steam mixing system, the controller selects and adopts three different modes, namely a temperature reduction and pressure reduction mode, a steam mixing mode and an original steam inlet mode according to different working conditions of the unit of the power generation system during load operation and the actual temperature of the inlet of the denitration System (SCR), realizes free switching and continuous adjustment, can realize adjustment of a denitration full load section, is flexible in operation adjustment and strong in load change adapting capability, so that the denitration System (SCR) can meet the full load section operation of the unit under high, medium and low loads, and can immediately adjust the inlet temperature of the denitration System (SCR) after the unit is connected to the grid;

2. the driving steam is taken from the steam of a low-temperature low-pressure pipeline, the pressure is ensured, the temperature is lower, safety and reliability are realized, a small amount of steam mixing device (101) is utilized to inject low-parameter steam as the driving steam, high-temperature high-pressure steam is introduced through an injection port to be mixed, the pressure of the driving steam is improved, the mixed steam is used as a new heat source to enter a corresponding high-pressure heater (102) to carry out water supply heating, the steam inlet parameter of the high-pressure heater (102) is improved, the steam inlet quantity can be further improved, the water supply temperature when the driving steam finally passes through the economizer (103) is adjusted, and the purposes of reducing the heat absorption quantity of the economizer (103) and improving the smoke temperature at the outlet of the economizer (103) are further.

Furthermore, the high-temperature high-pressure steam pipeline is provided with a high-pressure heater steam inlet pneumatic check valve (208) and a high-pressure heater steam inlet electric isolating valve (209). And a second high-pressure heater steam inlet electric isolating valve (205) is arranged between the injection port of the steam mixing device (101) and the high-pressure heater (102). By arranging a high-pressure heater steam inlet pneumatic check valve (208), a high-pressure heater steam inlet electric isolating valve (209) and a second high-pressure heater steam inlet electric isolating valve (205), a steam gas source added into the high-pressure heater can be selected, and the second high-pressure heater steam inlet electric isolating valve (205) is closed, so that a mixed gas source or a temperature and pressure reducing gas source is selected to heat the water supply of the high-pressure heater (102); and (3) starting the steam inlet electric isolating valve (205) of the second high-pressure heater, and selecting a high-temperature high-pressure gas source to heat the feed water of the high-pressure heater (102).

Further, a driving steam electric regulating valve (203) is arranged at the inlet of the steam mixing device (101). The driving steam electric regulating valve (203) is arranged, so that the supplement of the steam entering the steam mixing device (101) can be controlled. An injection port of the steam mixing device (101) is provided with an injected steam electric isolation valve (204). The steam output in the high-temperature high-pressure steam pipeline can be controlled by arranging the electric isolation valve (204) for injecting the steam.

The invention also provides a steam adjusting method for realizing denitration and temperature raising, which comprises the following steps: as shown in the figure, according to the unit input load operation condition of the power generation system, different operation modes are automatically selected by the controller to adjust the temperature of the output feed water when the feed water passes through the economizer, so that the heat of low-temperature flue gas is absorbed, the exhaust gas temperature is reduced, the exhaust gas loss is reduced, the fuel is saved, the power generation system adapts to the load change, particularly,

(1) after the unit is connected to the grid, a temperature and pressure reducing mode is put into operation under the low load rate of 25 percent, and the main configuration of the temperature and pressure reducing mode comprises the following steps: a high-pressure heater (102), a drive steam electric isolation valve (201), a drive steam constant-heating pipe bypass valve (202), a drive steam electric regulating valve (203), a second high-pressure heater steam inlet electric isolation valve (205), a drive steam bypass electric regulating valve (206) and a drive steam bypass temperature and pressure reduction device (207) which are connected through a steam pipeline, when the mode is operated, the steam inlet electric isolating valve (205) of the second high-pressure heater is closed and the steam electric regulating valve (203) is driven, the controller controls the opening of the steam-driven electric isolating valve (201) and the steam-driven normal heating pipe bypass valve (202), the opening degree of the steam bypass electric adjusting valve (206) is adjusted and driven, and the steam bypass temperature and pressure reducing device (207) is driven to reduce the temperature and the pressure of the steam and then the steam passes through the high-pressure heater (102) to increase the temperature of the water supply to the economizer (103).

(2) When the unit is put into operation in a steam mixing mode within the range of 25% to 40% medium load factor, the main configuration of the steam mixing mode comprises the following steps: the steam mixing device comprises a steam mixing device (101), a high-pressure heater (102), a driving steam electric isolation valve (201), a driving steam normally-heated pipe bypass valve (202), a driving steam electric adjusting valve (203), an injected steam electric isolation valve (204), a second high-pressure heater steam inlet electric isolation valve (205) and a driving steam bypass electric adjusting valve (206) which are connected through a steam pipeline, wherein when the steam mixing device operates in the mode, the second high-pressure heater steam inlet electric isolation valve (205) and the driving steam bypass electric adjusting valve (206) are closed, the driving steam electric isolation valve (201), the driving steam normally-heated pipe bypass valve (202) and the injected steam electric isolation valve (204) are opened, the temperature and the pressure of an inlet of the mixing steam device (101) meet the mixing requirement by adjusting the opening degree of the driving steam electric adjusting valve (203), and mixed steam discharged from an outlet of the mixing steam device (101) passes through the high-pressure heater (102), to increase the temperature of the feedwater to the economizer (103).

(3) When the unit is greater than 40% of high load rate, the original steam inlet mode is put into operation, and the main configuration of the original steam inlet mode comprises the following steps: the high-pressure steam economizer comprises a high-pressure heater (102), a driving steam electric isolation valve (201), a driving steam normal-heating pipe bypass valve (202), an injected steam electric isolation valve (204), a second high-pressure heater steam inlet electric isolation valve (205), a high-pressure heater steam inlet pneumatic check valve (208) and a high-pressure heater steam inlet electric isolation valve (209) which are connected through a steam pipeline, when the high-pressure steam economizer operates in the mode, the driving steam electric isolation valve (201), the driving steam normal-heating pipe bypass valve (202) and the injected steam electric isolation valve (204) are closed, the second high-pressure heater steam inlet electric isolation valve (205), the high-pressure heater steam inlet pneumatic check valve (208) and the high-pressure heater steam inlet electric isolation valve (209) are opened, and raw steam directly passes through the high-pressure heater (102) through a high-temperature steam pipeline so as to improve the water supply temperature of the coal economizer.

As shown in fig. 3, compared with the conventional production, after the system is put into operation in a grid-connected mode, when the load factor of the low-stage power generation and the middle-stage power generation is low, the inlet temperature of a denitration System (SCR) is obviously increased and is far higher than the temperature before the operation, and the inlet temperature of the denitration System (SCR) is higher along with the increase of the load factor and reaches the stage of high load factor, so that the advantages of the system are more obvious, and the inlet temperature of the denitration System (SCR) is higher, and the advantages of energy conservation and consumption reduction of the system can be better embodied.

The controller automatically controls each execution element according to the measurement result through each pressure and temperature parameter measured by the pressure and temperature detection device, the installation position of each pressure and temperature detection device refers to the reference calibration position in figure 1, and each pressure and temperature parameter is marked as follows:

driving steam pressure/temperature (P1/T1), steam compounder inlet driving steam pressure/temperature (P2/T2),

the steam mixing device is injected with steam inlet pressure/temperature (P3/T3), steam pressure/temperature (P4/T4) after a steam bypass electric regulating valve is driven, steam pressure/temperature (P5/T5) at an outlet of the steam mixing device, water temperature (T6) at an outlet of a high-pressure heater and flue gas temperature (T7) at an inlet of a denitration System (SCR).

In summary, the system disclosed by the invention has the advantages that three different modes, namely a temperature and pressure reduction mode, a steam mixing mode and an original steam inlet mode, are adopted, the system is free to switch and continuously adjust, the denitration full-load adjustment can be realized, and the capacity of adapting to load change is strong;

2. the system can effectively improve the inlet smoke temperature of a denitration System (SCR) to be more than 15 ℃ under the load rate of 40 percent, and the temperature-improving range is large;

3. the system has the advantages of high equipment reliability, low maintenance amount, small required field of equipment and low investment cost;

4. the adjusting method is effective supplement of full load section adjustment, the selection mode can be switched at any time, and the operation and adjustment are flexible;

5. the adjusting target is the feed water temperature, the steam-water heat exchange process is fast, and the temperature adjusting performance is good.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.