System and method for heating feed water of evaporator of nuclear power unit

Abstract

The invention provides a system and method for heating feed water of an evaporator of a nuclear power unit. The system comprises a high-pressure cylinder, a low-pressure cylinder, a first valve set, a second valve set, a third valve set, a fourth valve set, a fifth valve set, a sixth valve set, a seventh valve set, an eighth valve set, a bypass adjusting valve, the evaporator, a high-pressure heater, a condenser, a water feeding pump, a deaerator, a low-pressure heater and a condensation water pump. The method includes the following steps that (1) a bypass pipeline in front of the steam turbine bypass regulating valve is connected to a steam extraction pipeline behind a high-pressure heater steam extraction pipeline check valve through pipelines and the corresponding valve sets; (2) a bypass pipeline in front of the steam turbine bypass regulating valve is connected to a steam extraction pipeline behind a deaerator steam extraction pipeline check valve through pipelines and the corresponding valve sets; (3) a bypass pipeline in front of the steam turbine bypass regulating valve is connected to a steam extraction pipeline behind a low-pressure heater steam extraction pipeline check valve through pipelines and the corresponding valve sets; and (4) in the starting process of the unit, in the state that a steam turbine is stopped while reactors are not stopped, and under the working condition that the steam turbine load is greatly lowered, bypass steam is introduced into the high-pressure heater, the deaerator and the low-pressure heater to heat feed water of the evaporator, so that the fluctuation of the feed water temperature of an inlet of the evaporator is reduced, and the operation safety of the evaporator is protected.

Description

[0001] Technical field: [0002] The invention belongs to the technical field of nuclear power, and in particular relates to a system and method for heating feed water for an evaporator of a nuclear power unit. [0003] Background technique: [0004] The high-temperature gas-cooled reactor nuclear power plant is currently configured according to two reactors and one machine. The feed water at the inlet of the evaporator is heated by the low-pressure heater, deaerator and high-pressure heater to meet the water temperature requirements of the evaporator inlet. The normal steam source of the low-pressure heater, deaerator and high-pressure heater is the extraction steam of the steam turbine. [0005] The current system mainly has the following deficiencies: [0006] 1) Before the steam turbine is under load, steam extraction cannot be obtained, and the feed water of the evaporator can only be heated by supplying steam to the deaerator through the start-up boiler. The start-up boi...

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Problems solved by technology

[0006] 1) Before the steam turbine is under load, steam extraction cannot be obtained, and the feed water of the evaporator can only be heated by supplying steam to the deaerator through the start-up boiler. The start-up boiler needs to run for a long time, the cost is high, and the heating effect is poor and unstable;

[0007] 2) At the initial stage of unit start-up, a large amount of steam is discharged to the condenser through the bypass, and the heat of the steam discharged into the condenser cannot be used, which is a waste of energy;

[0008] 3) The steam is discharged into the condenser, which increases the temperature of the condensed water and reduces the efficiency of the steam turbine;

[0009] 4) If the temperature of condensed water is too high, it will affect the operation of fine treatment;

[0010] 5) After the steam enters the condenser and turns into condensed water, the condensed water pump must be used to pump it into the deaerator, which increases the power consumption of the condensed water pump;

[0011] 6) In the non-stop stacking operation condition, after the steam turbine is shut down, all the extraction steam is lost, the high-pressure heater, low-pressure heater, and deaerator steam source are all lost, and the temperature of the feed water at the evaporator inlet drops sharply, which affects the evaporator safety;

[0012] 7) When the single reactor is shut down, the load of the steam turbine is reduced by 50%, the extraction pressure and flow are reduced, and the inlet temperature of the operating reactor suddenly drops, which affects the safety of the evaporator

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