CN111637442A - A configuration adaptive, efficient, flexible and clean coal-fired power generation system and operation method - Google Patents

Abstract

The invention discloses a configuration self-adaptive high-efficiency flexible clean coal-fired power generation system and an operation method thereof. Meanwhile, the cascade utilization of energy is realized by adjusting the flow ratio of the air preheater and the pre-economizer, and the energy utilization efficiency in a flexible operation mode is improved. The invention can be used for the flexibility modification, energy-saving emission-reduction modification and new unit design of the coal-fired power plant.

Description

A configuration adaptive, efficient, flexible and clean coal-fired power generation system and operation method

technical field

The invention belongs to the field of coal-fired power generation, and in particular relates to a configuration adaptive, efficient, flexible and clean coal-fired power generation system and an operation method.

Background technique

The main characteristics of my country's energy resources are rich coal, poor oil, and little gas. In order to ensure energy security, coal will be the main body of my country's primary energy consumption for a long time in the future. Among them, more than 50% of coal (this proportion will increase year by year) is used for power generation. The long-term goal of my country's energy development is to "promote the revolution in energy production and consumption, and build a clean, low-carbon, safe and efficient energy system". Therefore, the installed capacity of renewable energy power generation in my country has grown rapidly. However, the time-varying characteristics of wind and solar power generation are strong, and the peak-shaving capacity of my country's power grid is insufficient, resulting in serious problems of abandoning wind and light.

For this reason, the operating characteristics of the thermal system of coal-fired generating units have changed from steady-state operating conditions to frequent peak regulation, and the thermal system has been in the process of peak regulation for a long time. Selective catalytic reduction (SCR) is the most widely used denitrification technology for coal-fired power plants. However, when the load is low, the flue gas temperature at the inlet of the SCR denitrification device drops, which causes the SCR denitration device to deviate from the temperature operating range, and the flue gas denitration efficiency of the coal-fired power station drops significantly. Therefore, it is urgent to develop a wide-load denitrification coal-fired power generation system that adapts to the flexible operation mode of coal-fired power plants.

However, the existing system structure that can realize wide-load denitrification of coal-fired power generation systems has problems such as affecting the efficiency of coal-fired power plants.

SUMMARY OF THE INVENTION

In order to overcome the above-mentioned problems in the prior art, the purpose of the present invention is to propose a self-adaptive, efficient, flexible and clean coal-fired power generation system and operation method. It is also equipped with a flue gas regulating baffle and regulating valve. The economizer is equipped with a water supply regulating valve group. Through the water supply regulating valve group, the heat exchange process between the flue gas and the working medium can be adjusted, so as to realize the control of the inlet temperature of the SCR denitration device. Precise control. At the same time, by adjusting the flow ratio of the air preheater and the pre-economizer, the cascade utilization of energy is realized, and the energy utilization efficiency in the flexible operation mode is improved.

In order to achieve the above object, the present invention adopts the following technical solutions:

An adaptive, efficient, flexible and clean coal-fired power generation system includes an economizer 2 and an SCR denitration device 4 that are sequentially arranged in a flue of a boiler 1 along a flue gas flow direction, and the rear flue of the SCR denitration device 4 is divided into two parallel partitions For the flue, one side separates the flue and arranges the No. 1 flue gas baffle 51 and the air preheater 53 in sequence along the flue gas flow direction, and the other side separates the flue and arranges the No. 2 flue gas damper 52 and the No. Pre-economizer 54 and Shunt No. 2 pre-economizer 55;

The lower port of the economizer 2 is connected to the water outlet of the diversion No. 1 pre-economizer 54 through the pipeline through the No. 2 water supply regulating valve 302 and the No. 1 water supply regulating valve 301; the No. 2 water supply regulating valve 302 is adjusted to the No. The pipeline between the valves 301 is connected with the water-cooling wall feed water inlet through the No. 5 feed water regulating valve 305; the upper port of the economizer (2) is connected with the water-cooling wall feed water inlet through the No. 3 feed water regulating valve 303; the upper part of the economizer (2) The port is connected to the water outlet of the No. 1 pre-economizer 54 through the No. 4 water supply regulating valve 304 and the No. 6 water supply regulating valve 306; The water outlet is connected; the water outlet of the No. 1 pre-economizer 54 is connected to the water outlet of the high-pressure heater group 6 through the No. 9 feedwater regulating valve 309, and then the No. 8 feedwater regulating valve 308 is connected to the No. 1 split pre-economizer. The water inlet of No. 54 is connected; the water inlet of No. 1 split pre-economizer 54 is connected to the water outlet of No. 2 split pre-economizer 55; The water outlet of the water pump 7 is connected; the water inlet of the high-pressure heater group 6 is connected to the water outlet of the feed pump 7.

The area of the No. 1 split-flow pre-economizer 54 is 0.1 to 0.3 times the area of the economizer 2 .

The area of the No. 1 split pre-economizer 54 is 0.5 to 0.8 times the area of the No. 2 split pre-economizer 55 .

The No. 1 water supply regulating valve 301, the No. 2 water supply regulating valve 303, the No. 3 water supply regulating valve 303 and the No. 4 water supply regulating valve 304 are electric automatic regulating valves.

In the described operation method of the adaptive, flexible, clean and collaborative coal-fired power generation system, part of the feed water of the high-pressure heater group 6 is heated by the No. Enter the economizer 2, and adjust the control valve group of the No. 1 feedwater control valve 301 to the No. 7 feedwater control valve 307, thereby changing the downstream and countercurrent relationship between the flue gas and the feedwater in the economizer (2), thereby adjusting the SCR denitrification The inlet flue gas temperature of the device 4 meets the requirements of the working temperature range of the SCR denitration device 4. The specific adjustment method is to measure the inlet flue gas temperature of the SCR denitration device 4:

1) If the measured flue gas temperature at the inlet of the SCR denitration device 4 is higher than its maximum working temperature, first close the No. 7 feedwater regulating valve 307; if the inlet flue gas temperature of the SCR denitration device 4 is still higher than its maximum working temperature, close the No. 4 feedwater regulator Valve 304, No. 5 water supply regulating valve 305 and No. 6 water supply regulating valve 306, open No. 1 water supply regulating valve 301, No. 2 water supply regulating valve 302 and No. 3 water supply regulating valve 303, so that the water supply from the lower part of the economizer (2) The port enters the economizer (2) and then flows out from the upper port of the economizer (2) into the water wall. At this time, the flue gas in the economizer (2) is in a countercurrent relationship with the feed water; at the same time, increase the No. 1 flue gas block The opening degree of the plate 51 is reduced and the opening degree of the No. 2 flue gas baffle 52 is reduced, thereby reducing the outlet water temperature of the No. 1 split pre-economizer 54;

2) If the measured inlet temperature of the SCR denitration device 4 is lower than its maximum working temperature, gradually open the No. 4 water supply regulating valve 304, the No. 5 water supply regulating valve 305 and the No. 6 water supply regulating valve 306, and gradually close the No. 1 water supply regulating valve 301 and 306. No. 3 feedwater regulating valve 303, so that feedwater enters the economizer (2) from the upper port of the economizer (2), and then flows out from the lower port of the economizer (2) into the water cooling wall. The flue gas and the feed water are in a downstream relationship; if the temperature of the flue gas at the inlet of the SCR denitration device 4 is still lower than its minimum working temperature, gradually open the No. 7 feed water regulating valve 307, so that part of the feed water directly enters the water wall through the bypass; at the same time, Decrease the opening degree of the No. 1 flue gas baffle 51 and increase the opening degree of the No. 2 flue gas baffle 52, thereby increasing the outlet water temperature of the No. 1 split pre-economizer 54;

When the coal-fired power generation system needs to increase the load rapidly, increase the opening degree of the No. 10 feedwater regulating valve 310, decrease the opening degree of the No. 8 feedwater regulating valve 308, increase the opening degree of the No. The outlet water part is sent to the No. 2 split-flow pre-economizer 55 through the bypass for heating, and then sent to the No. 1 split-flow pre-economizer 54 for heating, thereby reducing the steam extraction volume of the steam turbine of the high-pressure heater group 6 and increasing the output of the steam turbine. power.

The working temperature range of the SCR denitration device 4 is 300°C to 400°C;

Adjust the opening of the No. 1 flue gas damper 51 and the No. 2 flue gas damper 52, and the operating target is that the flue gas temperature at the flue gas outlet is the lowest.

The flue gas flow of the No. 2 flue gas baffle 52 accounts for 20% to 40% of the total flue gas flow.

The system of the invention can flexibly adjust the heat absorption distribution in the economizer, simultaneously realize precise control of the inlet temperature of the SCR denitration device, and at the same time obtain the highest coal-fired power generation efficiency limited by the denitration operation efficiency. The invention can be used for the flexibility transformation of coal-fired power stations, the transformation of energy saving and emission reduction, and the design and application of new generating units.

Compared with the prior art, the present invention has the following advantages:

(1) The present invention can expand the denitration operation range of the SCR system, and can realize high-efficiency denitration under all working conditions;

(2) Compared with the flue gas bypass technology, the present invention can improve the boiler efficiency by 0.3% to 0.8%;

(3) The present invention can realize the variable load operation of the coal-fired generator set above 3% of the rated load/min, and at the same time improve the power generation efficiency and denitration efficiency of the coal-fired generator set during rapid variable load operation.

Description of drawings

FIG. 1 is a schematic diagram of the system structure of the present invention.

FIG. 2 is a comparison diagram of the flue gas temperature at the inlet of the coal-fired generator set using the SCR of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1 , an adaptive, efficient, flexible and clean coal-fired power generation system of the present invention includes an economizer 2 and an SCR denitration device 4 that are sequentially arranged in the flue of a boiler 1 along the flue gas flow direction. After the SCR denitration device 4 The flue is divided into two parallel divided flues, one side of the divided flue is arranged along the flue gas flow direction, and the No. Gas baffle 52, split-flow No. 1 pre-economizer 54 and split-flow No. 2 pre-economizer 55; the lower port of the economizer 2 passes through the pipeline through the No. 2 water supply regulating valve 302 and the No. 1 water supply regulating valve 301 It is connected with the water outlet of No. 1 pre-economizer 54; the pipeline between No. 2 water supply regulating valve 302 and No. 1 water supply regulating valve 301 is connected with the water wall feed water inlet through No. 5 water supply regulating valve 305; the economizer ( 2) The upper port is connected to the water wall feed water inlet through No. 3 water supply regulating valve 303; the upper port of the economizer (2) is connected to the No. 1 pre-economizer 54 through the No. 4 water supply regulating valve 304 and No. 6 water supply regulating valve 306 The water outlet is connected to the water outlet; the feed water inlet of the water wall passes through the No. 7 feed water regulating valve 307 and is connected to the water outlet of the No. 1 pre-economizer 54; The water outlet of the unit 6 is connected and merged, and then connected to the water inlet of the No. 1 split pre-economizer 54 through the No. 8 water supply regulating valve 308; the water inlet of the No. 1 split pre-economizer 54 is connected to the No. The water outlet of No. 55 is connected; the water inlet of the No. 2 split pre-economizer 55 is connected to the water outlet of the feed pump 7 through the No. 10 feed water regulating valve 310; the water inlet of the high pressure heater group 6 is connected to the water outlet of the feed pump 7.

As a preferred embodiment of the present invention, the area of the No. 1 split-flow pre-economizer 54 is 0.1 to 0.3 times that of the economizer 2, so that the system has the best technical economy and highest system efficiency.

As a preferred embodiment of the present invention, the area of the No. 1 split-flow pre-economizer 54 is 0.5 to 0.8 times the area of the No. 2 split-flow pre-economizer 55, so that the technical economy of the system is the best, and the system efficiency is at the same time. Highest.

As a preferred embodiment of the present invention, the No. 1 water supply regulating valve 301, No. 2 water supply regulating valve 303, No. 3 water supply regulating valve 303 and No. 4 water supply regulating valve 304 are electric automatic regulating valves, which can improve the regulation performance of the system .

According to an operation method of an adaptive, flexible and clean collaborative coal-fired power generation system according to the present invention, part of the feed water of the high-pressure heater group 6 is heated by the No. It is directly sent to the economizer 2, and by adjusting the control valve group of the No. 1 feedwater control valve 301 to the No. 7 feedwater control valve 307, the downstream and countercurrent relationship between the flue gas and the feedwater in the economizer (2) is changed, thereby adjusting The inlet flue gas temperature of the SCR denitration device 4 meets the requirements of the working temperature range of the SCR denitration device 4. The specific adjustment method is to measure the inlet flue gas temperature of the SCR denitration device 4:

1) If the measured flue gas temperature at the inlet of the SCR denitration device 4 is higher than its maximum working temperature, first close the No. 7 feedwater regulating valve 307; if the inlet flue gas temperature of the SCR denitration device 4 is still higher than its maximum working temperature, close the No. 4 feedwater regulator Valve 304, No. 5 water supply regulating valve 305 and No. 6 water supply regulating valve 306, open No. 1 water supply regulating valve 301, No. 2 water supply regulating valve 302 and No. 3 water supply regulating valve 303, so that the water supply from the lower part of the economizer (2) The port enters the economizer (2) and then flows out from the upper port of the economizer (2) into the water wall. At this time, the flue gas in the economizer (2) is in a countercurrent relationship with the feed water; at the same time, increase the No. 1 flue gas block The opening degree of the plate 51 is reduced and the opening degree of the No. 2 flue gas baffle 52 is reduced, thereby reducing the outlet water temperature of the No. 1 split pre-economizer 54;

2) If the measured inlet temperature of the SCR denitration device 4 is lower than its maximum working temperature, gradually open the No. 4 water supply regulating valve 304, the No. 5 water supply regulating valve 305 and the No. 6 water supply regulating valve 306, and gradually close the No. 1 water supply regulating valve 301 and 306. No. 3 feedwater regulating valve 303, so that feedwater enters the economizer (2) from the upper port of the economizer (2), and then flows out from the lower port of the economizer (2) into the water cooling wall. The flue gas and the feed water are in a downstream relationship; if the temperature of the flue gas at the inlet of the SCR denitration device 4 is still lower than its minimum working temperature, gradually open the No. 7 feed water regulating valve 307, so that part of the feed water directly enters the water wall through the bypass; at the same time, Decrease the opening degree of the No. 1 flue gas baffle 51 and increase the opening degree of the No. 2 flue gas baffle 52, thereby increasing the outlet water temperature of the No. 1 split pre-economizer 54;

When the coal-fired power generation system needs to increase the load rapidly, increase the opening degree of the No. 10 feedwater regulating valve 310, decrease the opening degree of the No. 8 feedwater regulating valve 308, increase the opening degree of the No. The outlet water part is sent to the No. 2 split-flow pre-economizer 55 through the bypass for heating, and then sent to the No. 1 split-flow pre-economizer 54 for heating, thereby reducing the steam extraction volume of the steam turbine of the high-pressure heater group 6 and increasing the output of the steam turbine. power.

The working temperature range of the SCR denitration device 4 is 300°C to 400°C;

Adjust the opening of the No. 1 flue gas damper 51 and the No. 2 flue gas damper 52, and the operating target is that the flue gas temperature at the flue gas outlet is the lowest.

The flue gas flow of the No. 2 flue gas baffle 52 accounts for 20% to 40% of the total flue gas flow, so that the boiler has the highest operating efficiency.

The system of the present invention can switch the system configuration when the unit operates in different intervals, so as to maintain the SCR inlet flue gas temperature in the most suitable operating interval for the activity of the SCR denitration catalyst. As shown in Fig. 2, a coal-fired generator set adopts the system and operation method of the present invention. After calculation, the SCR inlet flue gas temperature can be controlled above 310°C in the entire load rate range of 0.3 to 1.0.

At the same time, the invention can improve the efficiency of the coal-fired generating set, maintain the regular efficiency at above 92% under each load rate, and improve the boiler efficiency by 0.3% to 0.8% compared with the flue gas bypass technology.

In addition, the present invention can improve the ramp rate of the unit. A coal-fired generating unit adopts the system and operation method of the present invention, and after calculation, the variable load rate can be increased to more than 3% of the rated load/min. Ensure the denitration efficiency of the SCR device.

Claims (8)

1. A configuration self-adaptive high-efficiency flexible clean coal-fired power generation system is characterized in that: the boiler comprises an economizer (2) and an SCR denitration device (4) which are sequentially arranged in a flue of a boiler (1) along a flue gas flow direction, wherein a rear flue of the SCR denitration device (4) is divided into two parallel separated flues, a first flue gas baffle (51) and an air preheater (53) are sequentially arranged on one side of the separated flue along the flue gas flow direction, and a second flue gas baffle (52), a first shunting pre-economizer (54) and a second shunting pre-economizer (55) are arranged on the other side of the separated flue along the flue gas flow direction;

the lower port of the economizer (2) is connected with a water outlet of a shunting first pre-economizer (54) through a second water supply regulating valve (302) and a first water supply regulating valve (301) by pipelines; a pipeline between the second water supply regulating valve (302) and the first water supply regulating valve (301) is connected with a water supply inlet of the water wall through a fifth water supply regulating valve (305); the upper port of the economizer (2) is connected with a water-cooled wall water supply inlet through a third water supply regulating valve (303); the upper port of the economizer (2) is connected with the water outlet of the shunting first pre-economizer (54) through a fourth water supply regulating valve (304) and a sixth water supply regulating valve (306); a water-cooled wall water supply inlet is connected with a water outlet of a shunting first pre-economizer (54) through a seventh water supply regulating valve (307); the water outlet of the first shunting pre-economizer (54) is connected with the water outlet of the high-pressure heater group (6) through a ninth feed water regulating valve (309), is converged and then is connected with the water inlet of the first shunting pre-economizer (54) through an eighth feed water regulating valve (308); the water inlet of the first shunting pre-economizer (54) is connected with the water outlet of the second shunting pre-economizer (55); the water inlet of the second shunting pre-economizer (55) is connected with the water outlet of the water feeding pump (7) through a tenth water feeding regulating valve (310); the water inlet of the high-pressure heater group (6) is connected with the water outlet of the feed pump (7).

2. A configuration adaptive high efficiency flexible clean coal fired power generation system as defined in claim 1 wherein: the area of the first flow-dividing pre-coal economizer (54) is 0.1 to 0.3 times of the area of the coal economizer (2).

3. A configuration adaptive high efficiency flexible clean coal fired power generation system as defined in claim 1 wherein: the area of the first shunting pre-economizer (54) is 0.5 to 0.8 times that of the second shunting pre-economizer (55).

4. A configuration adaptive high efficiency flexible clean coal fired power generation system as defined in claim 1 wherein: the first water supply regulating valve (301), the second water supply regulating valve (303), the third water supply regulating valve (303) and the fourth water supply regulating valve (304) are electric automatic regulating valves.

5. A method of operating a configured adaptive flexible clean cooperative coal fired power generation system as defined in any one of claims 1 to 4, wherein: the method is characterized in that part of feed water of a high-pressure heater group (6) is heated by a shunting pre-economizer (54) and then is sent into the economizer (2), part of feed water is directly sent into the economizer (2), and the downstream and upstream relations between flue gas and feed water in the economizer (2) are changed by adjusting regulating valve groups from a feed water regulating valve (301) to a feed water regulating valve (307), so that the inlet flue gas temperature of an SCR denitration device (4) is regulated to meet the working temperature interval requirement of the SCR denitration device (4), and the specific regulating method comprises the following steps of measuring the inlet flue gas temperature of the SCR denitration device (4):

1) if the measured temperature of the flue gas at the inlet of the SCR denitration device (4) is higher than the highest working temperature of the SCR denitration device, firstly closing a seventh water supply regulating valve (307), if the temperature of the flue gas at the inlet of the SCR denitration device (4) is still higher than the highest working temperature of the SCR denitration device, closing a fourth water supply regulating valve (304), a fifth water supply regulating valve (305) and a sixth water supply regulating valve (306), and opening a first water supply regulating valve (301), a second water supply regulating valve (302) and a third water supply regulating valve (303), so that the feed water enters the economizer (2) from the lower port of the economizer (2) and then flows out from the upper port of the economizer (2) to enter a water-cooled wall, and at the moment, the flue gas in the economizer (2) and the; meanwhile, the opening degree of the first flue gas baffle (51) is increased, and the opening degree of the second flue gas baffle (52) is reduced, so that the water temperature at the outlet of the first shunting pre-economizer (54) is reduced;

2) if the inlet temperature of the SCR denitration device (4) is measured to be lower than the highest working temperature, gradually opening a fourth water supply regulating valve (304), a fifth water supply regulating valve (305) and a sixth water supply regulating valve (306), and gradually closing a first water supply regulating valve (301) and a third water supply regulating valve (303), so that the water supply enters the economizer (2) from the upper port of the economizer (2) and then flows out from the lower port of the economizer (2) to enter a water-cooled wall, and at the moment, the flue gas in the economizer (2) is in a forward flow relation with the water supply; if the flue gas temperature at the inlet of the SCR denitration device (4) is still lower than the lowest working temperature, gradually opening a No. seven water supply regulating valve (307) to ensure that part of the water supply directly enters a water-cooled wall through a bypass; meanwhile, the opening degree of the first flue gas baffle (51) is reduced, and the opening degree of the second flue gas baffle (52) is increased, so that the outlet water temperature of the first shunting pre-economizer (54) is increased;

when the coal-fired power generation system needs to rapidly increase the load, the opening of a ten water supply regulating valve (310) is increased, the opening of an eight water supply regulating valve (308) is reduced, the opening of a nine water supply regulating valve (309) is increased, the outlet water part of a water supply pump (7) is sent to a second shunting pre-economizer (55) through a bypass to be heated and then sent to a first shunting pre-economizer (54) to be heated, and therefore the steam extraction quantity of a steam turbine of a high-pressure heater group (6) is reduced, and the output power of the steam turbine is increased.

6. The method of claim 5, wherein the method comprises the steps of: the working temperature range of the SCR denitration device (4) is 300-400 ℃.

7. The method of claim 5, wherein the method comprises the steps of: the opening degrees of the first smoke baffle (51) and the second smoke baffle (52) are adjusted, and the operation target is that the smoke temperature at the smoke outlet is the lowest.

8. The method of claim 7, wherein the method comprises the steps of: the smoke flow of the second smoke baffle (52) accounts for 20-40% of the total smoke flow.

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