A method for recovering waste heat from steam sootblower drain in coal-fired power station boiler

Abstract

The application discloses a method for recovering steam blowing water waste heat of a coal-fired power plant boiler, and the method comprises the following steps: taking part of low-temperature condensate water from a condensate pump outlet; exchanging heat between the low-temperature condensate water and high-temperature blowing water through a blowing water heat exchanger; sending the low-temperature blowing water to an atmospheric expander after being cooled; mixing the high-temperature condensate water with the low-temperature condensate water from a seventh low-pressure heater outlet, and sending the mixed condensate water to a low-temperature economizer under the action of a booster pump; transferring heat of flue gas to the mixed condensate water through the low-temperature economizer, so as to increase the temperature of the mixed condensate water; returning the high-temperature condensate water from the low-temperature economizer outlet to the outlet of a sixth low-pressure heater; arranging a low-temperature condensate water regulating valve on a low-temperature condensate water pipeline of the blowing water heat exchanger inlet, so as to regulate the flow of the low-temperature condensate water entering the blowing water heat exchanger; and arranging a medium-temperature condensate water regulating valve on a condensate water pipeline of the seventh low-pressure heater outlet, so as to regulate the total condensate water flow entering the low-temperature economizer. The method can recover the steam blowing water waste heat, can be combined with a conventional low-temperature economizer system, can avoid the impact of steam blowing water discontinuity on the system, and can improve the efficiency of the whole unit and reduce the coal consumption.

Description

Technical Field

[0001] The invention relates to a method for recovering waste heat from sootblower drains, in particular to a method for recovering waste heat from steam sootblower drains in a coal-fired power station boiler, and belongs to the technical field of coal-fired boilers. Background Art

[0002] Thermal power plants consume 50% of my country's total coal production. Exhaust heat loss is the largest heat loss component of power plant boilers, typically ranging from 5% to 8% and accounting for 80% or more of the boiler's total heat loss. Factors influencing exhaust heat loss include exhaust temperature, excess air coefficient, cold air temperature, raw coal calorific value, and fly ash carbon content, with boiler exhaust temperature being the most important. Generally speaking, every 20°C increase in exhaust temperature increases exhaust heat loss by approximately 1.0%. Boiler exhaust temperatures in my country's currently operating thermal power units generally range from around 125°C to 150°C, making high exhaust temperatures a common phenomenon. Therefore, reducing exhaust temperature through appropriate means not only recovers waste heat from flue gas but also facilitates environmentally friendly retrofits. Rational utilization of boiler exhaust heat plays a crucial role in improving unit efficiency.

[0003] During normal operation of coal-fired power plants, in addition to the exhaust heat, the water drain generated by steam sootblowers during boiler operation also offers significant energy-saving potential. Currently, steam sootblower drains in all coal-fired power plants in my country are directed to the atmospheric expansion tank, wasting energy. For example, a 350MW supercritical unit performs sootblowing three times daily, wasting 83 tons of condensate and 73MW of heat.

[0004] A method for recovering waste heat from the drain of a steam sootblower in a coal-fired power plant boiler was invented. Firstly, the waste heat from the drain of the sootblower in the coal-fired unit boiler can be recovered and reused. Secondly, the exhaust gas at the outlet of the expansion pipe can be eliminated. Thirdly, the method can be combined with conventional low-temperature economizer technology to greatly reduce project investment. Thirdly, the method can save condensate, which has a good promoting effect on alleviating water shortage in severely water-scarce areas. Summary of the Invention

[0005] A method for recovering waste heat from steam sootblower drains in coal-fired power station boilers, the equipment used in the method including a sootblower drain heat exchanger, a low-temperature economizer, an atmospheric expansion tank, a steam sootblower, a high-temperature sootblower drain, a low-temperature condensate regulating valve, a medium-temperature condensate regulating valve, a condensate booster pump, etc.

[0006] The function of the sootblowing drain heat exchanger is as follows: the high-temperature sootblowing drain at the outlet of the steam sootblower heats the low-temperature condensate, and the sootblowing drain after cooling becomes low-temperature sootblowing drain and is sent to the atmospheric expansion tank; the condensate after heating becomes medium-temperature condensate;

[0007] The inlet and outlet of the sootblowing drain heat exchanger are provided with a sootblowing drain heat exchanger inlet electric valve and a sootblowing drain heat exchanger bypass valve;

[0008] A low-temperature condensate regulating valve is provided on the low-temperature condensate pipeline to regulate the flow of low-temperature condensate entering the sootblowing drain heat exchanger;

[0009] The condensate at the outlet of the No. 7 low-pressure heater is mixed with the medium-temperature condensate to form mixed condensate. The mixed condensate is pressurized by the condensate booster pump and then enters the low-temperature economizer.

[0010] The medium-temperature condensate regulating valve is used to adjust the condensate flow rate at the outlet of the No. 7 low-pressure heater, thereby regulating the flow rate of mixed condensate entering the low-temperature economizer;

[0011] The function of the low-temperature economizer is to use the high-temperature flue gas at the outlet of the air preheater to heat the mixed condensate. The high-temperature condensate at the outlet of the low-temperature economizer returns to the outlet of the No. 6 low-pressure heater, and the flue gas is cooled and becomes low-temperature flue gas.

[0012] The steps of the method are as follows:

[0013] After passing through the condensate pump, the condensate is divided into two paths. One path enters the No. 7 low-pressure heater, and the other path enters the sootblowing water heat exchanger as low-pressure condensate. A low-temperature condensate regulating valve is installed on the low-temperature condensate pipeline to adjust the flow of low-temperature condensate entering the sootblowing water heat exchanger.

[0014] The high-temperature sootblowing drain at the steam sootblower outlet is sent to the sootblowing drain heat exchanger to heat the low-temperature condensate. The sootblowing drain after heat release becomes low-temperature sootblowing drain and is then sent to the atmospheric expansion tank.

[0015] The sootblowing drain heat exchanger inlet and outlet condensate pipes are equipped with a sootblowing drain heat exchanger inlet electric valve, a sootblowing drain heat exchanger outlet electric valve and a sootblowing drain heat exchanger bypass valve to ensure the normal and stable operation of the system when the sootblowing drain heat exchanger leaks.

[0016] The outlet condensate of the No. 7 low-pressure heater is mixed with the medium-temperature condensate of the sootblower drain heat exchanger outlet to form mixed condensate. A medium-temperature condensate regulating valve is provided on the outlet condensate pipeline of the No. 7 low-pressure heater to adjust the flow rate of the final mixed condensate.

[0017] The mixed condensate is pressurized by the condensate booster pump and sent to the low-temperature economizer. Through the action of the low-temperature economizer, the high-temperature flue gas is used to heat the mixed condensate. The condensate after absorbing heat and heating becomes high-temperature condensate. The high-temperature condensate is sent to the outlet of the No. 6 low-pressure heater, mixed with the main condensate at the outlet of the No. 6 low-pressure heater, and then enters the No. 5 low-pressure heater.

[0018] The present invention effectively couples the steam sootblower drain waste heat recovery with the low-temperature economizer technology. On the one hand, the waste heat from the sootblower drain of the coal-fired unit boiler is recovered and reused. On the other hand, the "little white dragon" at the outlet of the expansion pipe can be eliminated, thereby eliminating visual pollution. Thirdly, by combining it with conventional low-temperature economizer technology, project investment can be greatly reduced. Fourthly, condensate can be saved, which has a good promoting effect on alleviating water shortages in severely water-scarce areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a flowchart of the process and system composition of the present invention.

[0020] In the picture:

[0021] 1. Condensate pump; 2. No. 7 low-pressure heater; 3. No. 6 low-pressure heater; 4. No. 5 low-pressure heater; 5. Sootblower drain heat exchanger; 6. Low-temperature economizer; 7. Condensate booster pump; 8. Sootblower drain heat exchanger inlet electric valve; 9. Sootblower drain heat exchanger outlet electric valve; 10. Sootblower drain heat exchanger bypass valve; 11. Medium-temperature condensate regulating valve; 12. High-temperature condensate electric valve; 13. Low-temperature condensate regulating valve Throttle valve; 14. Atmospheric expansion tank; 15. High-temperature flue gas; 16. Low-temperature flue gas; 17. Condensate from outlet of No. 7 low-pressure heater; 18. Medium-temperature condensate; 19. Mixed condensate; 20. High-temperature condensate; 21. Low-temperature condensate; 22. Condensate; 23. High-temperature sootblowing drain; 24. Low-temperature sootblowing drain; 25. Steam sootblower; 26. Deaerator; 27. Air preheater; 28. Flue gas subsequent treatment equipment DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, the present invention includes a sootblowing drain heat exchanger 5, a low-temperature economizer 6, an atmospheric expansion tank 14, a steam sootblower 25, a high-temperature sootblowing drain 23, a low-temperature condensate regulating valve 13, a medium-temperature condensate regulating valve 11, a condensate booster pump 7, etc.;

[0024] The sootblower drain heat exchanger 5 functions as follows: the high-temperature sootblower drain 23 with a temperature of 130°C from the steam sootblower 25 heats the low-temperature condensate 21 at 41°C. The cooled high-temperature sootblower drain 23 becomes the low-temperature sootblower drain 24 at 51.6°C and is sent to the atmospheric expansion tank 14; the heated low-temperature condensate 21 becomes the medium-temperature condensate 18 at 68°C.

[0025] The inlet and outlet of the sootblowing drain heat exchanger 5 are provided with a sootblowing drain heat exchanger inlet electric valve 8 and a sootblowing drain heat exchanger inlet electric valve 9, and a sootblowing drain heat exchanger bypass valve 10;

[0026] A low-temperature condensate regulating valve 13 is provided on the low-temperature condensate 21 pipeline for regulating the flow of the low-temperature condensate 21 entering the sootblowing drain heat exchanger 5;

[0027] The 75°C condensate 17 at the outlet of the No. 7 low-pressure heater is mixed with the 68°C medium-temperature condensate 18, so that the temperature of the mixed condensate 19 reaches 70°C. The mixed condensate 19 is pressurized by the condensate booster pump 7 and enters the low-temperature economizer 6. The medium-temperature condensate regulating valve 11 is used to adjust the water flow of the condensate 17 at the outlet of the No. 7 low-pressure heater, thereby adjusting the flow of the mixed condensate 19 entering the low-temperature economizer 6.

[0028] The function of the low-temperature economizer 6 is to use the high-temperature flue gas 15 with an outlet temperature of 150°C from the air preheater 27 to heat the mixed condensate 19. After cooling, the high-temperature flue gas 15 becomes a low-temperature flue gas 16 with a temperature of 100°C and then enters the flue gas subsequent treatment equipment 28; the low-temperature economizer 6 heats the mixed condensate at 70°C to become a high-temperature condensate 20 with a temperature of 115.5°C, and the high-temperature condensate 20 returns to the outlet of the No. 6 low-pressure heater 3. The condensate at the outlet of the No. 6 low-pressure heater 3 and the high-temperature condensate 20 are mixed and then enter the No. 5 low-pressure heater 4 for heating, and then continue to enter the deaerator 26. The temperature of the high-temperature condensate 20 is the same as the temperature of the condensate at the outlet of the No. 6 low-pressure heater 3.

[0029] The benefits of the steam sootblower drain waste heat recovery method include two parts: one is the coal saving benefit, and the other is the water saving benefit.

[0030] Coal saving benefits:

[0031] Taking a 350MW supercritical unit as an example, the effective utilization hours throughout the year are 5,200 hours, and the total drain time throughout the year is 2,250 hours. The steam sootblower drain waste heat recovery method saves 4,943.75 tons of standard coal annually. Calculated at a standard coal unit price of 582 yuan / ton (tax included), the annual fuel cost can be saved by 2.8773 million yuan.

[0032] Water saving benefits:

[0033] The steam sootblower drains 11.04 t / h of water per cycle, 82.81 t / h of water per day, and a total of 24,842.7 t of water per year. This method allows for the recycling of drain water, with the condensate price calculated at 5 yuan per ton. The total annual water-saving benefit is 124,200 yuan.

[0034] The total annual revenue was 3.0015 million yuan.

[0035] The steps of the heating method are as follows:

[0036] After passing through the condensate pump 1, the condensate 22 is divided into two paths. One path enters the No. 7 low-pressure heater 2, and the other path enters the sootblowing water heat exchanger 5 as low-temperature condensate 21. A low-temperature condensate regulating valve 13 is provided on the low-temperature condensate 21 pipeline to regulate the flow of the low-temperature condensate 21 entering the sootblowing water heat exchanger 5.

[0037] The high-temperature sootblowing drain 23 at the outlet of the steam sootblower 25 is sent to the sootblowing drain heat exchanger 5 to heat the low-temperature condensate 21. After releasing heat, the high-temperature sootblowing drain 23 becomes low-temperature sootblowing drain 24 and is then sent to the atmospheric expansion tank 14.

[0038] The inlet and outlet condensate pipes of the sootblowing drain heat exchanger 5 are provided with a sootblowing drain heat exchanger inlet electric valve 8, a sootblowing drain heat exchanger outlet electric valve 9 and a sootblowing drain heat exchanger bypass valve 10, which are used to ensure the normal and stable operation of the system when the sootblowing drain heat exchanger 5 leaks.

[0039] The outlet condensate 17 of the No. 7 low-pressure heater 2 is mixed with the medium-temperature condensate 18 of the sootblowing drain heat exchanger 5 to form mixed condensate 19. The outlet condensate 17 of the No. 7 low-pressure heater is provided with a medium-temperature condensate regulating valve 11 to regulate the flow of the final mixed condensate 19.

[0040] The mixed condensate 19 is pressurized by the condensate booster pump 7 and sent to the low-temperature economizer 6. Through the action of the low-temperature economizer 6, the high-temperature flue gas 15 from the air preheater 27 is used to heat the mixed condensate 19. The condensate after absorbing heat and heating is converted into high-temperature condensate 20. The high-temperature condensate 20 is sent to the outlet of the No. 6 low-pressure heater 3, mixed with the main condensate at the outlet of the No. 6 low-pressure heater 3, and then enters the No. 5 low-pressure heater 4, and then continues to enter the deaerator 26.

[0041] The above embodiments are not limitations of the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by technicians in this technical field within the scope of the technical solution of the present invention also fall within the scope of protection of the present invention.

Claims

1. A method for recovering waste heat from steam sootblowers in coal-fired power station boilers, characterized by: The steam sootblower drain waste heat recovery method comprises: a sootblower drain heat exchanger (5), a low-temperature economizer (6), an atmospheric expansion tank (14), a steam sootblower (25), a high-temperature sootblower drain (23), a low-temperature condensate regulating valve (13), a medium-temperature condensate regulating valve (11), and a condensate booster pump (7); The sootblowing drain heat exchanger (5) functions as follows: the high-temperature sootblowing drain (23) from the steam sootblower (25) heats the low-temperature condensate (21); the high-temperature sootblowing drain (23) after cooling is converted into low-temperature sootblowing drain (24) and sent to the atmospheric expansion tank (14); the low-temperature condensate (21) after heating is converted into medium-temperature condensate (18); The inlet and outlet of the sootblowing drain heat exchanger (5) are provided with a sootblowing drain heat exchanger inlet electric valve (8), a sootblowing drain heat exchanger outlet electric valve (9), and a sootblowing drain heat exchanger bypass valve (10); the low-temperature condensate (21) pipeline is provided with a low-temperature condensate regulating valve (13) for regulating the flow of the low-temperature condensate (21) entering the sootblowing drain heat exchanger (5); The medium-temperature condensate regulating valve (11) is used to regulate the flow rate of the condensate (17) at the outlet of the No. 7 low-pressure heater, thereby regulating the flow rate of the mixed condensate (19) entering the low-temperature economizer (6); The condensate (17) at the outlet of the No. 7 low-pressure heater is mixed with the medium-temperature condensate (18) to form mixed condensate (19), and the mixed condensate (19) is pressurized by the condensate booster pump (7) and then enters the low-temperature economizer (6); The function of the low-temperature economizer (6) is to heat the mixed condensate (19) by using the high-temperature flue gas (15) from the outlet of the air preheater (27); the high-temperature condensate (20) at the outlet of the low-temperature economizer (6) returns to the outlet of the No. 6 low-pressure heater (3); the flue gas is cooled and becomes low-temperature flue gas (16) and then enters the flue gas subsequent treatment equipment (28); the condensate at the outlet of the No. 6 low-pressure heater (3) and the high-temperature condensate (20) are mixed and then enter the No. 5 low-pressure heater (4) for heating, and then continue to enter the deaerator (26); The steps of the steam sootblower drain waste heat recovery method are as follows: After passing through the condensate pump (1), the condensate (22) is divided into two paths, one of which enters the No. 7 low-pressure heater (2), and the other enters the sootblowing drain heat exchanger (5) as low-temperature condensate (21); a low-temperature condensate regulating valve (13) is provided on the low-temperature condensate (21) pipeline for regulating the flow of the low-temperature condensate (21) entering the sootblowing drain heat exchanger (5); The high-temperature sootblowing drain (23) at the outlet of the steam sootblower (25) is sent to the sootblowing drain heat exchanger (5) to heat the low-temperature condensate (21). The high-temperature sootblowing drain (23) after releasing heat is converted into low-temperature sootblowing drain (24) and then sent to the atmospheric expansion tank (14); A sootblowing drain heat exchanger inlet electric valve (8), a sootblowing drain heat exchanger outlet electric valve (9) and a sootblowing drain heat exchanger bypass valve (10) are provided on the sootblowing drain heat exchanger (5) inlet and outlet condensate pipes to ensure normal and stable operation of the system when the sootblowing drain heat exchanger (5) leaks; The outlet condensate (17) of the No. 7 low-pressure heater (2) is mixed with the medium-temperature condensate (18) of the sootblowing drain heat exchanger (5) to form mixed condensate (19). A medium-temperature condensate regulating valve (11) is provided on the outlet condensate (17) pipeline of the No. 7 low-pressure heater for regulating the flow of the final mixed condensate (19). The mixed condensate (19) is pressurized by the condensate booster pump (7) and then sent to the low-temperature economizer (6). Through the action of the low-temperature economizer (6), the mixed condensate (19) is heated by the high-temperature flue gas (15) from the air preheater (27). The condensate after absorbing heat and heating is converted into high-temperature condensate (20). The high-temperature condensate (20) is sent to the outlet of the No. 6 low-pressure heater (3), mixed with the main condensate at the outlet of the No. 6 low-pressure heater (3), and then enters the No. 5 low-pressure heater (4), and then continues to enter the deaerator (26).

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