A flushing system and method for salt accumulation in a power station boiler system

Abstract

The invention discloses a flushing system and method for salt accumulation in a power station boiler system. The flushing system comprises a temporary water inlet pipe connected with a condensate pipe and a low-pressure bypass pipe of the power station boiler system, a temporary water inlet valve arranged on the temporary water inlet pipe, a temporary short pipe connected with a reheater system and a superheater system of the power station boiler system, a unit drainage trough connected with a lower water bag of the power station boiler system through a temporary discharge pipe, and a sampling valve, a pressure gauge and a temporary discharge valve arranged on the unit drainage trough. The invention also discloses a flushing method for the system, so as to control the sodium ion content of drainage to be less than 20 μg / L. The system of the invention is simple in design, reliable and easy to implement, and solves the problem of salt accumulation in the boiler heating area and inability of the unit to operate normally due to condenser leakage in coastal power plants.

Description

Technical Field

[0001] The invention relates to salt accumulation in a boiler water vapor system caused by seawater entering the boiler water vapor system due to leakage of a condenser heat exchange tube, and in particular to a flushing system and a flushing method for salt accumulation in a power station boiler system. Background Art

[0002] Once seawater leaks from the condenser, the quality of water vapor will deteriorate, eventually causing salt accumulation in the boiler water vapor system, making the unit unable to operate normally. In particular, when the salt accumulation in the lower elbows of the "U" or "W" type heat exchange tubes of the superheater and reheater tubes is serious, water flushing is required. During the water flushing process, the "W" type heat exchange tubes of the final superheater and the high-temperature reheater may have gas plugs, resulting in no circulation in the heat exchange tubes. In this way, during the startup process, as the accumulated water in the heat exchange tubes continues to evaporate, the salt dissolved in the heat exchange tubes will eventually precipitate in the lower elbows, and there is a risk of blockage in the lower elbows of the heat exchange tubes, which may cause tube bursts. Therefore, in this case, relying on existing conditions to flush the boiler with a small flow rate has a greater risk. It is necessary to use a condensate pump and design a certain auxiliary system to achieve a large flow rate flushing of the boiler to completely eliminate the salt that may remain in the boiler superheater and reheater system due to gas plugs. At present, the use of this flushing system and method can completely solve the salt accumulation problem caused by seawater leakage in the boiler superheater and reheater system. Summary of the invention

[0003] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a flushing system and flushing method for salt accumulation in a power station boiler system. The system is simple in design, reliable and easy to implement, and solves the problem that salt accumulation in the boiler superheater and reheater system caused by seawater leakage in the condenser heat exchange tube leads to the unit being unable to operate normally.

[0004] In order to achieve the above object, the present invention adopts the following technical scheme:

[0005] A flushing system for salt accumulation in a power station boiler system comprises a temporary water inlet pipe 8 connecting a condensate pipe 5 and a low-pressure bypass pipe 6 of the power station boiler system, a temporary water inlet valve 9 arranged on the temporary water inlet pipe 8; a temporary short pipe 13 connecting a reheater system 10 and a superheater system 14 of the power station boiler system; a unit drain trough 22 connected to a lower water drum 17 of the power station boiler system through a temporary discharge pipe 18, a sampling valve 19, a pressure gauge 20 and a temporary discharge valve 21 arranged on the unit drain trough 22; a condenser 1→condensate pump 2→condensate pipe 5→temporary water inlet pipe 8→temporary water inlet valve 9→reheater system 10→high-pressure bypass pipe 11, high-pressure bypass valve 12 and temporary short pipe 13→superheater system 14→steam drum 15→water-cooled wall 16→lower water drum 17→temporary discharge pipe 18→temporary discharge valve 21→unit drain trough 22 to form a reverse flushing loop.

[0006] A temporary plugging plate 7 is provided at the connection point between the temporary water inlet pipe 8 and the low-pressure bypass pipe 6 for plugging.

[0007] The pH value of the system flushing water is adjusted by using the condensate ammonia addition point in the power station boiler system, and the flushing water is heated by using the four-stage steam extraction in the power station boiler system to increase the temperature of the flushing water without connecting to a temporary dosing system and a temporary heating system.

[0008] The flushing method of the flushing system of the salt accumulation in the power station boiler system is as follows: the condenser 1 of the power station boiler system is replenished with water to a high liquid level, the first condensate pump 2-1 is started to replenish water to the deaerator 4, the replenishing water flow rate is adjusted by the condensate self-circulation valve 3, the internal circulation of the deaerator 4 and the condenser 1 is established, the pH value of the water is adjusted to be greater than 10.0 by adding ammonia, the deaerator 4 is heated, and the heating is stopped when the water temperature reaches 50-70°C, and the exhaust air valves of the reheater system 10, the superheater system 14, the drum 15 and the water-cooled wall 16 are opened in turn, and the temporary water inlet valve 9 is gradually opened to slowly add water to the power station boiler system, and when the exhaust air valves of the reheater system 10, the superheater system 14, the drum 15 and the water-cooled wall 16 have continuous water flow, the exhaust air valves are closed in turn, and when the reading of the pressure gauge 20 reaches 0.5-0.7MPa, the sampling valve 19 is gradually opened. and temporary water inlet valve 9, close the condensate self-circulation valve 3, and start the second condensate pump 2-2 (frequency conversion regulation) at the same time, and flush the reheater system 10, superheater system 14 and water-cooled wall 16 of the power station boiler system with a large flow of water; when the condenser 1 reaches a low liquid level, switch the first condensate pump 2-1 and the second condensate pump 2-2 to self-circulation operation, measure the temperature of the tube screens of the reheater system 10 and the superheater system 14 or perform auxiliary inspection through DCS to confirm that there is no air blockage in the tube screens of the reheater system 10 and the superheater system 14, that is, the tube screens of the reheater system 10 and the superheater system 14 are in a circulation state; during the flushing process, take samples at the sampling valve 19 to determine the sodium ion content of the drainage; if the sodium ion content is greater than 20μg / L, repeat the above steps for repeated flushing until the sodium ion content of the drainage is less than 20μg / L.

[0009] There is no need to connect a temporary flushing pump, and the first condensate pump 2-1 and the second condensate pump 2-2 of the power plant boiler system are used as flushing power.

[0010] Flushing discharge water does not need deep treatment, and only needs to adjust the pH value to meet GB 8978 "Comprehensive Wastewater Discharge Standard".

[0011] When the sodium ion content of the drainage is less than 20μg / L, the cold and hot flushing water quality of the power station boiler system can meet the requirements of GB / T 12145 in a short period of time.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] 1) Use condensate pump to provide flushing power and use deaerator to heat flushing water;

[0014] 2) A temporary water inlet pipe is designed from condensate to the low bypass as the boiler flushing water inlet pipe, and the low bypass pipe is temporarily blocked on the condenser side. The reheater, superheater and water wall system are reversely flushed in turn through the high bypass pipe and steam drum;

[0015] 3) Since the cross-sectional area of ​​the reheater tube screen is much larger than that of the superheater, especially the "W" type tube of the high-temperature reheater may have some tubes with air blockage due to the low flow rate, resulting in no circulation, that is, the salt accumulation cannot be effectively flushed. According to the calculation of the cross-sectional area of ​​the reheater system, some tube screens of the high-temperature reheater are short-circuited to the tube screen of the last-stage superheater through temporary pipes to increase the overall flushing flow of the reheater. By measuring the wall temperature of the tube screen, it is determined to eliminate the air blockage of the reheater system and ensure the flushing effect of all tube screens;

[0016] 4) Connect a temporary pipe from the sewer as the flushing discharge pipe. Install an on-site pressure gauge and sampling point on the temporary discharge pipe to control the flushing flow and flushing end point. The flushing end point is to sample and test the sodium ion content of the discharged water to less than 20μg / L.

[0017] 5) The system design is simple, the performance is reliable, and it is easy to implement;

[0018] 6) It effectively solved the problem of salt accumulation in the boiler superheater and reheater system, resulting in the unit being unable to operate normally, due to seawater leakage from the condenser heat exchange tubes entering the water steam system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a schematic flow chart of a flushing system and method for flushing salt accumulated in a power station boiler system.

[0020] In the figure: 1—condenser; 2-1—the first condensate pump; 2-2—the second condensate pump; 3—condensate self-circulation valve; 4—deaerator; 5—condensate pipeline; 6—low-pressure bypass pipeline; 7—temporary plugging plate; 8—temporary water inlet pipeline; 9—temporary water inlet valve; 10—reheater system; 11—high bypass pipeline; 12—high bypass valve; 13—temporary short pipe; 14—superheater system; 15—steam drum; 16—water-cooled wall; 17—lower drum; 18—temporary discharge pipe; 19—sampling valve; 20—pressure gauge; 21—temporary discharge valve; 22—unit drain tank. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0022] like Figure 1As shown, a flushing system for salt accumulation in a power station boiler system of the present invention comprises a temporary water inlet pipe 8 connecting a condensate pipe 5 and a low-pressure bypass pipe 6 of the power station boiler system, a temporary water inlet valve 9 arranged on the temporary water inlet pipe 8; a temporary short pipe 13 connecting a reheater system 10 and a superheater system 14 of the power station boiler system; a unit drain trough 22 connected to a lower water drum 17 of the power station boiler system through a temporary discharge pipe 18, a sampling valve 19, a pressure gauge 20 and a temporary discharge valve 21 arranged on the unit drain trough 22; a condenser 1→condensate pump 2→condensate pipe 5→temporary water inlet pipe 8→temporary water inlet valve 9→reheater system 10→high-pressure bypass pipe 11, high-pressure bypass valve 12 and temporary short pipe 13→superheater system 14→steam drum 15→water-cooled wall 16→lower water drum 17→temporary discharge pipe 18→temporary discharge valve 21→unit drain trough 22 to form a reverse flushing loop.

[0023] As a preferred embodiment of the present invention, a temporary plugging plate 7 is provided at the connection point between the temporary water inlet pipe 8 and the low-pressure bypass pipe 6 to reversely flush the reheater, superheater and water-cooled wall system in turn through the high bypass pipe and the steam drum.

[0024] The present invention uses the condensate ammonia adding point in the power station boiler system to adjust the pH value of the system flushing water, and uses the four-stage steam extraction in the power station boiler system to heat the flushing water to increase the temperature of the flushing water, without connecting to a temporary dosing system and a temporary heating system.

[0025] like Figure 1As shown, the flushing method of the flushing system of the salt accumulation in the power station boiler system described in the present invention is to replenish water to the high liquid level of the condenser 1 of the power station boiler system, start the first condensate pump 2-1 to replenish water to the deaerator 4, adjust the replenishing water flow rate through the condensate self-circulation valve 3, establish the internal circulation of the deaerator 4 and the condenser 1, adjust the pH value of the water to be greater than 10.0 by adding ammonia, heat the deaerator 4, stop heating when the water temperature reaches 50-70°C, open the exhaust air valves of the reheater system 10, the superheater system 14, the drum 15 and the water-cooled wall 16 in turn, gradually open the temporary water inlet valve 9, slowly add water to the power station boiler system, and when the exhaust air valves of the reheater system 10, the superheater system 14, the drum 15 and the water-cooled wall 16 have continuous water flow, close the exhaust air valves in turn, and when the reading of the pressure gauge 20 reaches 0.5-0.7MPa, gradually open the sampling valve Valve 19 and temporary water inlet valve 9, close the condensate self-circulation valve 3, and start the second condensate pump 2-2 (frequency conversion regulation) at the same time to flush the reheater system 10, superheater system 14 and water-cooled wall 16 of the power station boiler system with large flow water; when the condenser 1 reaches a low liquid level, the first condensate pump 2-1 and the second condensate pump 2-2 are switched to self-circulation operation, and the tube screens of the reheater system 10 and the superheater system 14 are measured for temperature or checked by DCS assistance to confirm that there is no air blockage in the tube screens of the reheater system 10 and the superheater system 14, that is, the tube screens of the reheater system 10 and the superheater system 14 are in a circulation state; during the flushing process, samples are taken at the sampling valve 19 to determine the sodium ion content of the drainage; if the sodium ion content is greater than 20μg / L, repeat the above steps for repeated flushing until the sodium ion content of the drainage is less than 20μg / L.

[0026] The flushing method of the present invention does not need to connect a temporary flushing pump, and uses the first condensate pump 2-1 and the second condensate pump 2-2 of the power station boiler system as flushing power.

[0027] Flushing discharge water does not need deep treatment, and only needs to adjust the pH value to meet GB 8978 "Comprehensive Wastewater Discharge Standard".

[0028] When the sodium ion content of the drainage is less than 20μg / L, the cold and hot flushing water quality of the power station boiler system can meet the requirements of GB / T 12145 in a short period of time.

Claims

1. A flushing method for a flushing system for salt accumulation in a power station boiler system, the system comprising a temporary water inlet pipe (8) connecting a condensate pipe (5) and a low-pressure bypass pipe (6) of the power station boiler system, a temporary water inlet valve (9) arranged on the temporary water inlet pipe (8); a temporary short pipe (13) connecting a reheater system (10) and a superheater system (14) of the power station boiler system; a unit drain trough (22) connected to a lower water drum (17) of the power station boiler system through a temporary discharge pipe (18), and a temporary water inlet valve (9) arranged on the temporary water inlet pipe (8); The sampling valve (19), pressure gauge (20) and temporary discharge valve (21) on the steam condenser (1) → condensate pump (2) → condensate pipe (5) → temporary water inlet pipe (8) → temporary water inlet valve (9) → reheater system (10) → high bypass pipe (11), high bypass valve (12) and temporary short pipe (13) → superheater system (14) → steam drum (15) → water wall (16) → lower water drum (17) → temporary discharge pipe (18) → temporary discharge valve (21) → unit drainage tank (22) form a reverse flushing loop; Features: The flushing method is as follows: The condenser (1) of the power station boiler system is replenished with water to a high liquid level, and the first condensate pump (2-1) is started to replenish water to the deaerator (4). The replenishment flow rate is adjusted by the condensate self-circulation valve (3), and an internal circulation between the deaerator (4) and the condenser (1) is established. The pH value of the water is adjusted to be greater than 10.0 by adding ammonia. The deaerator (4) is heated. When the water temperature reaches 50-70°C, the heating is stopped, and the reheater system (10), the superheater system (11) and the reheater system (12) are opened in sequence. 14), the air exhaust valves of the drum (15) and the water wall (16), gradually open the temporary water inlet valve (9), slowly add water to the power station boiler system, and when there is continuous water flow in the air exhaust valves of the reheater system (10), the superheater system (14), the drum (15) and the water wall (16), close the air exhaust valves in sequence. When the reading of the pressure gauge (20) reaches 0.5-0.7MPa, gradually open the sampling valve (19) and the temporary water inlet valve (9). ), close the condensate self-circulation valve (3), and at the same time start the second condensate pump (2-2) by frequency conversion regulation to flush the reheater system (10), superheater system (14) and water-cooled wall (16) of the power station boiler system with a large flow of water; when the condenser (1) reaches a low liquid level, switch the first condensate pump (2-1) and the second condensate pump (2-2) to self-circulation operation, measure the temperature of the tube screens of the reheater system (10) and the superheater system (14) or perform a DCS auxiliary inspection to confirm that there is no air blockage in the tube screens of the reheater system (10) and the superheater system (14), that is, the tube screens of the reheater system (10) and the superheater system (14) are in a flow state; during the flushing process, take a sample at the sampling valve (19) to determine the sodium ion content of the drainage; if the sodium ion content is greater than 20 μg / L, repeat the above steps to flush repeatedly until the sodium ion content of the drainage is less than 20 μg / L.

2. The flushing method according to claim 1, characterized in that: A temporary blocking plate (7) is provided at the connection point between the temporary water inlet pipe (8) and the low-pressure bypass pipe (6) for blocking.

3. The flushing method according to claim 1, characterized in that: The pH value of the system flushing water is adjusted by using the condensate ammonia addition point in the power station boiler system, and the flushing water is heated by using the four-stage steam extraction in the power station boiler system to increase the temperature of the flushing water without connecting to a temporary dosing system and a temporary heating system.

4. The flushing method according to claim 1, characterized in that: There is no need to connect a temporary flushing pump, and the first condensate pump (2-1) and the second condensate pump (2-2) of the power station boiler system are used as flushing power.

5. The flushing method according to claim 1, characterized in that: The pH value of the system flushing water is adjusted by using the condensate ammonia addition point in the power station boiler system, and the flushing water is heated by using the four-stage steam extraction in the power station boiler system to increase the temperature of the flushing water without connecting to a temporary dosing system and a temporary heating system.

6. The flushing method according to claim 1, characterized in that: Flushing discharge water does not need deep treatment, and only needs to adjust the pH value to meet GB 8978 "Comprehensive Wastewater Discharge Standard".

7. The flushing method according to claim 1, characterized in that: When the sodium ion content of the drainage is less than 20μg / L, the cold and hot flushing water quality of the power station boiler system can meet the requirements of GB / T 12145 in a short period of time.

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