System for increasing boiler feed water temperature by using main steam pipe in coal-fired power generation unit

Abstract

The utility model discloses a system for increasing boiler feed water temperature by using a main steam pipe in a coal-fired power generation unit, which comprises a boiler, the main steam pipe is arranged on the boiler, and the main steam pipe is arranged on the boiler and is connected with a first bypass superheated steam pipe and a second bypass superheated steam pipe; the end part of the first bypass superheated steam pipe is connected with a steam turbine high-pressure cylinder, a section of steam extraction pipe is arranged on the steam turbine high-pressure cylinder, and a section of steam extraction pipe isolation valve is arranged on the section of steam extraction pipe; the end part of the first-section steam extraction pipe is connected with a first high-pressure heater, a low-temperature water supply pipe is arranged on the first high-pressure heater, and a high-temperature water supply pipe connected with a boiler is arranged on the first high-pressure heater; the second bypass superheated steam is provided with a pressure reduction adjusting valve and a desuperheater, an outlet of the desuperheater is provided with a temperature and pressure reduction superheated steam pipe, the desuperheater is further connected with a temperature reduction water pipe, the temperature reduction water pipe is provided with a temperature reduction water pipe adjusting valve, and an outlet of the temperature and pressure reduction superheated steam pipe is connected to the steam extraction pipe.

Description

Technical Field

[0001] The utility model relates to a system for increasing the boiler feed water temperature by using a main steam pipe in a coal-fired generator set, belonging to the technical field of energy-saving of coal-fired boilers. Background Art

[0002] More than 90% of my country's large coal-fired units use the selective catalytic reduction (SCR) method. In order to meet the temperature window of the SCR catalyst, the inlet flue gas temperature is required to be above 300°C during the operation of the unit. Figure 1 As shown in the figure, the low boiler feed water temperature causes the low SCR inlet flue gas temperature. When the SCR inlet flue gas temperature is lower than 300°C, the SCR cannot operate normally, resulting in ultra-low NOx emission concentration, catalyst deactivation, increased ammonia slip, etc. Therefore, wide-load denitrification technology must be used to meet NOx emission requirements and achieve full load and full-time stable emission requirements above the minimum technical output.

[0003] The current wide-load denitrification technologies mainly include: economizer water side bypass, economizer flue gas bypass, economizer feed water recirculation, staged economizer, zero-level high-pressure heater, boiler water recirculation, etc. At present, wide-load denitrification systems generally have problems such as limited layout space, limited temperature increase effect, and complex system. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a system for increasing the boiler feed water temperature by using the main steam pipe in a coal-fired generator set with a simple structure.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is: a system for increasing the boiler feed water temperature by using a main steam pipe in a coal-fired power generation unit, comprising a boiler, a main steam pipe is provided on the boiler, and the main steam pipe is provided on the boiler to connect with a first bypass superheated steam pipe and a second bypass superheated steam;

[0006] The end of the first bypass superheated steam pipe is connected to the high-pressure cylinder of the steam turbine, a steam extraction pipe is provided on the high-pressure cylinder of the steam turbine, and a steam extraction pipe isolation valve is provided on the steam extraction pipe; the end of the steam extraction pipe is connected to the No. 1 high-pressure heater, a low-temperature feed water pipe is provided on the No. 1 high-pressure heater, and a high-temperature feed water pipe connected to the boiler is provided on the No. 1 high-pressure heater;

[0007] The second bypass superheated steam is provided with a pressure reducing regulating valve and a desuperheater. The outlet of the desuperheater is provided with a temperature reducing and pressure reducing superheated steam pipe. The desuperheater is also connected to a temperature reducing water pipe. The temperature reducing water pipe is provided with a temperature reducing water pipe regulating valve. The outlet of the temperature reducing and pressure reducing superheated steam pipe is connected to the part between a steam extraction pipe isolation valve and the No. 1 high-pressure heater on a steam extraction pipe.

[0008] As a preferred solution, a bypass superheated steam isolation valve is provided on the second bypass superheated steam.

[0009] As a preferred solution, a cooling water pipe isolation valve is provided on the cooling water pipe.

[0010] As a preferred solution, the high-temperature water supply pipe is provided with a high-temperature water pipe regulating valve and a high-temperature water pipe isolating valve.

[0011] The beneficial effects of the utility model are:

[0012] The utility model adopts the bypass superheated steam after temperature reduction and pressure reduction as the steam source of the No. 1 high-pressure heater. The temperature and pressure of the superheated steam after temperature reduction and pressure reduction entering the No. 1 high-pressure heater can be adjusted by the temperature reduction water pipe regulating valve and the pressure reducing regulating valve.

[0013] Since the pressure of the main steam is much higher than the pressure of the first stage of extraction steam, the utility model can achieve that the pressure of the superheated steam entering the No. 1 high-pressure heater under low-load conditions is higher than the pressure of the first stage of extraction steam under this condition, thereby greatly increasing the temperature of the high-temperature feed water at the outlet of the No. 1 high-pressure heater. After calculation, the temperature of the high-temperature feed water can be increased. As the temperature of the high-temperature feed water increases, the flue gas temperature at the SCR inlet can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the original system flow chart. Figure 2 This is a process system diagram of the utility model.

[0015] 1. Boiler; 2. High-pressure cylinder of steam turbine; 3. No. 1 high-pressure heater; 4. Isolation valve of first-stage steam extraction pipe; 5. Low-temperature feed water pipe; 6. High-temperature feed water pipe; 7. Main steam pipe; 8. First-stage steam extraction pipe; 9. First bypass superheated steam pipe; 10. Bypass superheated steam pipe; 11. Bypass superheated steam isolation valve; 12. Pressure reducing regulating valve; 13. Isolation valve of cooling water pipe; 14. Control valve of cooling water pipe; 15. Desuperheater; 16. Cooling and pressure reducing superheated steam pipe; 17. Cooling water pipe; 18. Control valve of high-temperature water pipe; 19. Control valve of high-temperature water pipe. DETAILED DESCRIPTION

[0016] The specific implementation scheme of the utility model is described in detail below in conjunction with the accompanying drawings.

[0017] like Figure 2 As shown, a system for increasing the boiler feed water temperature by using a main steam pipe in a coal-fired power generation unit comprises a boiler 1, on which a main steam pipe 7 is provided, and the main steam pipe 7 is connected to a first bypass superheated steam pipe 9 and a second bypass superheated steam pipe 10;

[0018] The end of the first bypass superheated steam pipe 9 is connected to the high-pressure cylinder 2 of the steam turbine, and a steam extraction pipe 8 is provided on the high-pressure cylinder 2 of the steam turbine, and a steam extraction pipe isolation valve 4 is provided on the steam extraction pipe 8; the end of the steam extraction pipe 8 is connected to the No. 1 high-pressure heater 3, and a low-temperature feed water pipe 5 is provided on the No. 1 high-pressure heater 3, and a high-temperature feed water pipe 6 connected to the boiler 1 is provided on the No. 1 high-pressure heater 3; the high-temperature feed water pipe 6 is provided with a high-temperature water pipe regulating valve 18 and a high-temperature water pipe isolation valve 19.

[0019] The second bypass superheated steam 10 is provided with a bypass superheated steam isolation valve 11, a pressure reducing regulating valve 12, and a desuperheater 15. The outlet of the desuperheater 15 is provided with a desuperheating and pressure reducing superheated steam pipe 16. The desuperheater 15 is also connected to a desuperheating water pipe 17. The desuperheating water pipe 17 is provided with a desuperheating water pipe isolation valve 13 and a desuperheating water pipe regulating valve 14. The outlet of the desuperheating and pressure reducing superheated steam pipe 16 is connected to the part between the first extraction pipe isolation valve 4 and the No. 1 high-pressure heater 3 on a first extraction pipe 8.

[0020] During operation, the main steam at the outlet of boiler 1 is divided into two parts: first bypass superheated steam and bypass superheated steam. The first bypass superheated steam enters the high-pressure cylinder 2 of the steam turbine to perform work. The isolation valve 4 of the original first stage extraction pipe is closed, and the first stage extraction steam is in an isolated state.

[0021] The bypass superheated steam passes through the bypass superheated steam isolation valve 11 and is decompressed through the pressure reducing regulating valve 12;

[0022] After the desuperheating water passes through the desuperheating water pipe isolation valve 13, the desuperheating water pipe regulating valve 14 is used to adjust the flow rate. The bypass superheated steam after decompression passes through the desuperheater 15 and uses the desuperheating water to reduce the temperature, and finally the bypass superheated steam becomes desuperheated and decompressed superheated steam.

[0023] The superheated steam with reduced temperature and pressure is sent to the No. 1 high-pressure heater 3, thereby replacing the original section of the steam extraction pipe 8 to heat the low-temperature feed water. The low-temperature feed water is heated by the No. 1 high-pressure heater 3 and becomes high-temperature feed water, which is finally sent to the boiler 1.

[0024] When the system is operating normally, the pressure of the first extraction steam changes with the change of the unit load. Taking a 350MW supercritical unit as an example, the pressure of the first extraction steam is about 11MPa at 100% THA load, and the pressure of the first extraction steam is about 3MPa at 30% THA load. Since the No. 1 high-pressure heater 3 is a condensing heat exchanger, the high-temperature feed water temperature at its outlet depends on the feed water end difference of the No. 1 high-pressure heater 3, and the feed water end difference refers to the difference between the saturated temperature at the inlet steam pressure of the No. 1 high-pressure heater 3 and the outlet high-temperature feed water temperature. Therefore, the high-temperature feed water temperature at the outlet of the No. 1 high-pressure heater 3 continues to decrease as the unit load decreases.

[0025] The utility model adopts the bypass superheated steam after cooling and pressure reduction as the steam source of the No. 1 high-pressure heater 3. The temperature and pressure of the superheated steam after cooling and pressure reduction entering the No. 1 high-pressure heater 3 can be adjusted by the cooling water pipe regulating valve 14 and the pressure reducing regulating valve 12.

[0026] Since the pressure of the main steam is much higher than the pressure of the first stage of extraction steam, the pressure of the main steam can still reach about 11MPa even at 30% THA load. Therefore, the utility model can achieve that the pressure of the superheated steam entering the No. 1 high-pressure heater 3 under low-load conditions is higher than the pressure of the first stage of extraction steam under this condition, thereby greatly increasing the temperature of the high-temperature feed water at the outlet of the No. 1 high-pressure heater 3. After calculation, the temperature of the high-temperature feed water can be increased to 40°C. As the temperature of the high-temperature feed water rises, the flue gas temperature at the SCR inlet can be increased by about 40 to 60°C.

[0027] The above-mentioned embodiments are only illustrative of the principles and effects of the invention, as well as some embodiments of its application, and are not intended to limit the invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the invention, and all of these belong to the protection scope of the invention.

Claims

1. A system for increasing boiler feed water temperature by using a main steam pipe in a coal-fired power generation unit, characterized in that: The boiler comprises a boiler (1), the boiler is provided with a main steam pipe (7), the main steam pipe (7) is connected to a first bypass superheated steam pipe (9) and a second bypass superheated steam pipe (10); The end of the first bypass superheated steam pipe (9) is connected to the high-pressure cylinder (2) of the steam turbine, a steam extraction pipe (8) is provided on the high-pressure cylinder (2) of the steam turbine, and a steam extraction pipe isolation valve (4) is provided on the steam extraction pipe (8); the end of the steam extraction pipe (8) is connected to the No. 1 high-pressure heater (3), a low-temperature feed water pipe (5) is provided on the No. 1 high-pressure heater (3), and a high-temperature feed water pipe (6) connected to the boiler (1) is provided on the No. 1 high-pressure heater (3); The second bypass superheated steam (10) is provided with a pressure reducing regulating valve (12) and a desuperheater (15). The outlet of the desuperheater (15) is provided with a desuperheating and pressure reducing superheated steam pipe (16). The desuperheater (15) is also connected with a desuperheating water pipe (17). The desuperheating water pipe (17) is provided with a desuperheating water pipe regulating valve (14). The outlet of the desuperheating and pressure reducing superheated steam pipe (16) is connected to the portion between a first extraction pipe isolation valve (4) and the No. 1 high-pressure heater (3) on a first extraction pipe (8).

2. The system for increasing boiler feed water temperature by using a main steam pipe in a coal-fired power generation unit according to claim 1, characterized in that: The second bypass superheated steam (10) is provided with a bypass superheated steam isolation valve (11).

3. The system for increasing boiler feed water temperature by using a main steam pipe in a coal-fired power generation unit according to claim 1, characterized in that: The desuperheating water pipe (17) is provided with a desuperheating water pipe isolation valve (13).

4. A system for increasing boiler feed water temperature by using a main steam pipe in a coal-fired power generation unit according to any one of claims 1 to 3, characterized in that: The high-temperature water supply pipe (6) is provided with a high-temperature water pipe regulating valve (18) and a high-temperature water pipe isolation valve (19).

Images