System and method for recycling once-through boiler start-up drained water through pressure flash vessel

Abstract

The invention discloses a system and method for recycling once-through boiler start-up drained water through a pressure flash vessel. The system comprises a separator water storage tank, the pressure flash vessel, a deaerator, a high-pressure heater, a unit water drainage channel and the like. The method includes the following steps that the once-through boiler start-up drained water is gathered at the separator water storage tank, the water in the separator water storage tank is drained into the pressure flash vessel through a water level control valve of the separator water storage tank for expansion and pressure reduction, and saturated water and steam matched with steam side pressure of the high-pressure heater are generated; the saturated water enters the steam side of the high-pressure heater through a water level adjustment main valve of the pressure flash vessel, is subjected to heat absorption of the high-pressure heater, passes through the high-pressure heater and a drained water adjustment valve of the deaerator and finally returns to the deaerator; the steam enters the deaerator through a pressure adjustment main valve of the pressure flash vessel; unqualified water in the start-up process passes through the pressure flash vessel and is drained into the unit water drainage channel through an adjustment valve of the unit water drainage channel, and water which is generated by the pressure flash vessel and can not be completely recycled by the high-pressure heater is directly drained to the deaerator through the water level adjustment valve of the pressure flash vessel.

Description

Technical field: [0001] The invention belongs to the field of electric power, and in particular relates to a system and method for recovering water from a once-through boiler by using a pressure expansion vessel to drain water. Background technique: [0002] Before the once-through boiler of the power station turns dry, the start-up separator will separate a part of saturated water, which is stored in the water storage tank of the separator. The separated water is called once-through boiler start-up drainage. At present, there are mainly the following ways to start the drainage of hydrophobicity. [0003] The first is to use the boiler water circulation pump to recycle the start-up drain to the inlet of the boiler economizer. This method mainly has the following shortcomings: [0004] (1) During the working process of the start-up system, the working medium of the boiler water circulation pump has relatively high temperature and pressure, which requires high quality of the...

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Problems solved by technology

The cost of imported boiler water circulation pumps is high and the order cycle is long. At present, thermal power generation is developing rapidly, and the supply of boiler water circulation pumps often cannot meet the needs of power plant construction.

[0005] (2) The cooling water quality of the motor chamber of the boiler water circulation pump is very high. In many power plants, the filter screen in the motor chamber has been clogged, resulting in high temperature of the boiler water pump motor and the furnace has to be shut down for maintenance.

[0006] (3) The boiler water circulation pump has high requirements on the reliability of the cooling water. In some power plants, due to the leakage of the cooling water in the motor chamber, the high-temperature water in the furnace entered the furnace water circulation pump motor chamber, causing the boiler water circulation pump motor coil to burn out. , had to shut down for maintenance

[0007] (4) The maintenance of the boiler water circulation pump is troublesome

[0009] (1) The start-up drainage of the once-through boiler is saturated high-pressure water. After the expansion of the atmospheric expansion vessel, part of the exhaust steam through the atmospheric expansion vessel is discharged into the air, and part of the water that can be recovered can only be saturated water under normal pressure, resulting in Reduced waste of water and heat

[0010] (2) The water vapor discharged into the air condenses and falls into the surrounding environment, causing pollution to the surrounding environment

[0011] (3) If the water quality of the saturated water in the atmospheric expansion vessel is qualified, it needs to be discharged into the condenser. However, due to the high temperature of the recycled water, after entering the condenser, the temperature of the condensed water will increase, which will reduce the efficiency of the unit. Affect the safe operation of condensate polishing

[0012] (4) The water in the atmospheric expansion vessel must be pumped into the condenser through the drain pump, which increases the investment

[0013] (5) The condenser is connected to the atmospheric expansion vessel. Due to internal leakage of the valve and other reasons, the vacuum of the condenser is affected, the efficiency of the unit operation is reduced, and the safe operation of the unit is even affected.

[0014] (6) The atmosphere expander is not closed, and the dust in the air will inevitably enter the atmosphere expander, which increases the secondary pollution of the start-up drainage

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