WO2021238322A1

WO2021238322A1 - Efficient, clean and flexible cooperative coal-fired power generation system and operation method

Info

Publication number: WO2021238322A1
Application number: PCT/CN2021/078894
Authority: WO
Inventors: 刘明; 严俊杰; 刘继平; 种道彤; 邢秦安
Original assignee: 西安交通大学
Priority date: 2020-05-24
Filing date: 2021-03-03
Publication date: 2021-12-02
Also published as: CN111603928B; CN111603928A

Abstract

An efficient, clean and flexible cooperative coal-fired power generation system and an operation method. The system comprises a coal economizer (2), an SCR denitration device (3) and a front coal economizer (4) which are sequentially arranged in a tail flue of a boiler (1) along the flue gas flow direction. A rear flue of the front coal economizer (4) is divided into two parallel separation flues, a first flue gas baffle (51) and an air preheater (53) are sequentially arranged on the separation flue on one side along the flue gas flow direction, and a second flue gas baffle (52), a first flow division coal economizer (54) and a second flow division coal economizer (55) are sequentially arranged on the separation flue on the other side along the flue gas flow direction; a water outlet of the coal economizer (2) is connected to a water supply inlet of a water-cooling wall, and a water inlet of the coal economizer (2) is connected to a water outlet of the front coal economizer (4) and to a water inlet of the front coal economizer (4) by means of a first water supply regulating valve (61); the water inlet of the front coal economizer (4) is connected to a water outlet of the first flow division coal economizer (54) and to a water outlet of a high-pressure heater group (7) by means of a second water supply regulating valve (62); a water inlet of the first flow division coal economizer (54) is connected to a water outlet of the second flow division coal economizer (55), and to the water outlet of the high-pressure heater group (7) by means of a third water supply regulating valve (63); a water inlet of the second flow division coal economizer (55) is connected to a water outlet of a water feeding pump (8) by means of a fourth water supply regulating valve (64); and a water inlet of the high-pressure heater group (7) is connected to a water outlet of the water feeding pump (8).

Description

High-efficiency, clean and flexible coal-fired power generation system and operation method

Technical field

The invention belongs to the field of coal-fired power generation, and specifically relates to an efficient, clean and flexible coal-fired power generation system and an operation method.

Background technique

Realizing high-efficiency denitrification under all working conditions, increasing the rate of variable load, and improving operation efficiency are the basic national policy of "energy saving and emission reduction" and the technical requirements for coal-fired power generation. However, the efficiency, cleanliness, and flexibility of coal-fired generating units restrict each other. Because the SCR denitration catalyst has its working temperature zone requirements, and the inlet temperature of the SCR denitration catalyst drops when the load of the conventional coal-fired generator set is reduced, it is difficult for the coal-fired generator set to achieve high-efficiency denitrification at a wide load. At the same time, the operating efficiency of coal-fired generator sets during rapid climbing is significantly reduced.

In recent years, my country has made great achievements in the development of new energy, and the installed capacity of new energy power generation has grown rapidly. However, wind energy and solar energy are unstable, causing strong fluctuations in the output power of solar photovoltaic and wind power generation, causing huge power-side load disturbances to the power grid. In order to balance power supply and demand, coal-fired generating sets need frequent and deep variable load operation. At the same time, in order to improve the operational safety of the power grid, coal-fired generator sets need to have the ability to quickly climb the variable load.

The SCR denitrification device is the mainstream denitrification device, but the SCR denitrification catalyst has a suitable operating temperature range. When the inlet flue gas temperature of the SCR denitrification device deviates from the operating temperature range of the SCR denitrification catalyst, the denitrification efficiency will be significantly reduced. It is for this reason that the NOx emissions of coal-fired power plants are greatly increased during low-load operation. Existing technologies such as flue gas bypass and water supply bypass generally have the prominent contradiction between high efficiency and cleanliness. In addition, when the unit is operating at rapid variable load, the instantaneous denitrification efficiency of the prior art SCR and the efficiency of coal-fired power plants are significantly reduced.

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 an efficient, clean and flexible coal-fired power generation system and operation method. Flue gas regulating baffle and regulating valve. The system can accurately adjust the temperature of the flue gas at the inlet of the SCR to achieve high-efficiency denitrification at a wide load of coal-fired generator sets, and at the same time improve the efficiency of wide-load operation. In addition, the system can increase the variable load rate of coal-fired generating sets, and in the process of increasing the variable load rate, improve system efficiency and SCR denitrification efficiency.

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

A high-efficiency, clean and flexible coal-fired power generation system, including economizer 2, SCR denitrification device 3 and front economizer 4 arranged in the tail flue of boiler 1 in sequence along the flue gas flow direction, front economizer 4 and rear flue gas The duct is divided into two parallel separated flues. One side of the separated flue is arranged in sequence along the flue gas flow direction with the No. 1 flue gas baffle 51 and the air preheater 53, and the other side is arranged in sequence along the flue gas flow direction with No. 2 flue gas baffle 52. No. 1 shunt economizer 54 and No. 2 shunt economizer 55; the water outlet of economizer 2 is connected to the water wall feedwater inlet, and the water inlet of economizer 2 is connected to the water outlet of pre-economizer 4, and it passes The No. 1 feedwater regulating valve 61 is connected to the water inlet of the front economizer 4; the water inlet of the front economizer 4 is connected to the water outlet of the No. 1 split economizer 54, and it is also connected to the high-pressure heater group through the No. 2 feedwater regulating valve 62 7 water outlet is connected; No. 1 split economizer 54 water inlet is connected to No. 2 split economizer 55 water outlet, and also connected to the 7 water outlet of the high pressure heater group through No. 3 feed water regulating valve 63; No. 2 split economizer The water inlet of 55 is connected to the water outlet of the feedwater pump 8 through the No. 4 feedwater regulating valve 64; the water inlet of the high-pressure heater group 7 is connected to the water outlet of the feedwater pump 8.

The area of the front economizer 4 is 0.2 to 0.4 times the area of the economizer 2.

The area of the first split economizer 54 is 0.5 to 0.8 times the area of the second split economizer 55.

The No. 1 water supply regulating valve 61, the No. 2 water supply regulating valve 62, the No. 3 water supply regulating valve 63 and the No. 4 water supply regulating valve 64 are electric automatic regulating valves.

According to the operating method of an efficient, clean and flexible coal-fired power generation system, the inlet flue gas temperature of the SCR denitrification device 3 is adjusted to meet the working temperature range of the SCR denitrification device 3 by adjusting the No. 1 feedwater regulating valve 61. The specific adjustment method is, measuring The inlet flue gas temperature of the SCR denitrification device 3, if the flue gas temperature at the inlet of the SCR denitrification device 3 is measured higher than the maximum working temperature of the SCR denitrification device 3, increase the opening degree of the No. 1 feedwater regulating valve 61; measure the SCR denitrification device 3 If the inlet flue gas temperature of SCR is lower than the working temperature of SCR denitrification device 3, reduce the opening degree of No. 1 feedwater regulating valve 61;

When the coal-fired power generation system needs to increase the load quickly, increase the opening of the No. 4 feedwater regulating valve 64, reduce the opening of the No. 3 feedwater regulating valve 63, increase the opening of the No. 2 feedwater regulating valve 62, and decrease it by one. The opening degree of No. 61 feedwater regulating valve;

By adjusting the opening degrees of the No. 1 flue gas baffle 51 and the No. 2 flue gas baffle 52, the temperature of the flue gas at the tail flue gas outlet of the boiler 1 is the lowest.

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

The operating temperature range of the SCR denitrification device 3 is 300°C to 400°C.

The system of the present invention adopts the arrangement mode of separating parallel flues and grading economizers, and is equipped with flue gas regulating baffles and regulating valves. The system can accurately adjust the temperature of the flue gas at the inlet of the SCR to achieve high-efficiency denitrification in a wide load of coal-fired generator sets, and at the same time improve the efficiency of wide-load operation. In addition, the system of the present invention can increase the variable load rate of the coal-fired generator set, and in the process of increasing the variable load rate, improve the system efficiency and the SCR denitrification efficiency.

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

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

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

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

Description of the drawings

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

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

Fig. 3 is a graph showing the change trend of output power of a case coal-fired generator set using the present invention.

Detailed ways

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

As shown in Figure 1, an efficient, clean and flexible coal-fired power generation system of the present invention includes an economizer 2, an SCR denitrification device 3, and a pre-economizer 4 sequentially arranged in the tail flue of the boiler 1 along the flue gas flow direction. The flue after the pre-economizer 4 is divided into two parallel separated flues. One side of the separated flue is arranged in sequence along the flue gas flow direction with the No. 1 flue gas baffle 51 and the air preheater 53, and the other side is along the flue gas flow direction. Arrange the No. 2 flue gas baffle 52, No. 1 split economizer 54 and No. 2 split economizer 55 in sequence; the economizer 2 water outlet is connected to the water wall feedwater inlet, and the economizer 2 water inlet is connected to the front economizer The water outlet of the device 4 is connected, and the water inlet of the pre-economizer 4 is connected through the No. 1 water supply regulating valve 61; the water inlet of the pre-economizer 4 is connected to the water outlet of the No. 1 split economizer, and the water outlet is also connected through the No. 2 water supply The regulating valve 62 is connected to the 7 water outlet of the high pressure heater group; the water inlet of the No. 1 split economizer 54 is connected to the water outlet of the No. 2 split economizer 55, and the water outlet of the high pressure heater group 7 is also connected through the No. 3 feed water regulating valve 63. Connected; the water inlet of the second split economizer 55 is connected to the water outlet of the feedwater pump 8 through the fourth feedwater regulating valve 64; the water inlet of the high-pressure heater group 7 is connected to the water outlet of the feedwater pump 8.

As a preferred embodiment of the present invention, the area of the pre-economizer 4 is 0.2 to 0.4 times the area of the economizer 2, so that the inlet flue gas temperature of the SCR denitrification device 3 can be maintained at an appropriate level within the full range of operating conditions. Working temperature zone.

As a preferred embodiment of the present invention, the area of the first split economizer 54 is 0.5 to 0.8 times the area of the second split economizer 55, which can improve the matching relationship between the flue gas heat release and the working fluid system, and improve System energy utilization efficiency, and reduce system investment.

As a preferred embodiment of the present invention, the first feedwater regulating valve 61, the second feedwater regulating valve 62, the third feedwater regulating valve 63, and the fourth feedwater regulating valve 64 are electric automatic regulating valves, which can enhance the control performance of the system .

According to the operating method of an efficient, clean and flexible coal-fired power generation system of the present invention, the inlet flue gas temperature of the SCR denitrification device 3 is adjusted to meet the working temperature range of the SCR denitrification device 3 by adjusting the No. 1 feedwater regulating valve 61, and the specific adjustment method is as follows: , Measure the inlet flue gas temperature of the SCR denitrification device 3, if the flue gas temperature at the inlet of the SCR denitrification device 3 is higher than the maximum operating temperature of the SCR denitrification device 3, increase the opening of the No. 1 feedwater regulating valve 61; measure the SCR denitrification If the inlet flue gas temperature of the device 3 is lower than the working temperature of the SCR denitrification device 3, reduce the opening degree of the No. 1 feedwater regulating valve 61;

As a preferred embodiment of the present invention, the flue gas flow of the second flue gas baffle 52 accounts for 20%-40% of the total flue gas flow, so that the boiler can have the highest operating efficiency.

The system of the present invention can switch the system configuration when the unit is operating in different intervals, so as to maintain the temperature of the flue gas at the inlet of the SCR in the operation interval where the activity of the SCR denitration catalyst is most suitable. As shown in Figure 2, a coal-fired generating set adopts the system and operation method of the present invention. After calculation, the temperature of the flue gas at the inlet of the SCR can be controlled above 320°C within 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 generator set, maintain the boiler efficiency above 92% at various load rates, and improve the boiler efficiency by 0.3% to 0.8% compared with the flue gas bypass technology.

In addition, the present invention can increase the climbing rate of the unit. As shown in Figure 3, a coal-fired generating set adopts the system and operation method of the present invention. After calculation, the variable load rate can be increased to more than 3% of the rated load/min. Adjusting the opening of the relevant valve can ensure the denitration efficiency of the SCR device.

Claims

An efficient, clean and flexible coal-fired power generation system, which is characterized in that it includes an economizer (2), an SCR denitrification device (3) and a pre-economizer arranged in the tail flue of the boiler (1) along the flue gas flow direction. (4), the flue after the front economizer (4) is divided into two parallel separated flues, one side of the separated flue is arranged in sequence along the flue gas flow direction No. 1 flue gas baffle (51) and air preheater ( 53). On the other side, the No. 2 flue gas baffle (52), No. 1 split economizer (54) and No. 2 split economizer (55) are arranged in sequence along the flue gas flow direction;

The water outlet of the economizer (2) is connected with the water supply inlet of the water wall, and the water inlet of the economizer (2) is connected with the water outlet of the pre-economizer (4). The water inlet of the coal device (4) is connected; the water inlet of the front economizer (4) is connected to the water outlet of the No. 1 split economizer (54), and it is also connected to the high-pressure heater group (7) through the No. 2 feedwater regulating valve (62). ) The water outlet is connected; the water inlet of the No. 1 split economizer (54) is connected to the No. 2 split economizer (55) water outlet, and the water outlet of the high pressure heater group (7) is also connected through the No. 3 feedwater regulating valve (63) Connected; the water inlet of the No. 2 split economizer (55) is connected to the water outlet of the feed water pump (8) through the No. 4 feed water regulating valve (64); the water inlet of the high pressure heater group (7) is connected to the water outlet of the feed water pump (8) .
The high-efficiency, clean and flexible coal-fired power generation system according to claim 1, wherein the area of the front economizer (4) is 0.2 to 0.4 times the area of the economizer (2).
The high-efficiency, clean and flexible coal-fired power generation system according to claim 1, wherein the area of the No. 1 split economizer (54) is 0.5 to 0.8 of the area of the No. 2 split economizer (55). Times.
The high-efficiency, clean and flexible coal-fired power generation system according to claim 1, characterized in that: the No. 1 water supply regulating valve (61), the No. 2 water supply regulating valve (62), and the No. 3 water supply regulating valve (63) And the No. 4 water supply regulating valve (64) is an electric automatic regulating valve.
The operation method of an efficient, clean and flexible coal-fired power generation system according to any one of claims 1 to 4, characterized in that: the inlet flue gas of the SCR denitrification device (3) is adjusted by adjusting the No. 1 feedwater regulating valve (61) The temperature meets the working temperature range of the SCR denitrification device (3). The specific adjustment method is to measure the inlet flue gas temperature of the SCR denitrification device (3). If the inlet flue gas temperature of the SCR denitrification device (3) is measured higher than the SCR denitrification device (3) When the maximum working temperature is reached, increase the opening of the No. 1 feedwater regulating valve (61); measure the inlet flue gas temperature of the SCR denitrification device (3), if it is lower than the working temperature of the SCR denitrification device (3), reduce it The opening degree of the small one-size feedwater regulating valve (61);

When the coal-fired power generation system needs to increase the load quickly, increase the opening of the No. 4 feedwater regulating valve (64), reduce the opening of the No. 3 feedwater regulating valve (63), and increase the opening of the No. 2 feedwater regulating valve (62). Opening degree, reduce the opening degree of No. 1 feedwater regulating valve (61);

By adjusting the opening degrees of the No. 1 flue gas baffle (51) and the No. 2 flue gas baffle (52), the flue gas temperature at the tail flue gas outlet of the boiler (1) is the lowest.
The operation method according to claim 5, characterized in that: the flue gas flow of the No. 2 flue gas baffle (52) accounts for 20%-40% of the total flue gas flow.
The operating method according to claim 5, characterized in that the operating temperature range of the SCR denitrification device (3) is 300°C to 400°C.