Shaft-seal steam supply system for secondary reheat unit and control method of shaft-seal steam supply system

Abstract

The invention provides a shaft-seal steam supply system for a secondary reheat unit. The shaft-seal steam supply system comprises a shaft-seal main pipe, an auxiliary steam supply station, an overflowcontrol station, a temperature reduction control station and an electric heating control station; the shaft-seal main pipe is provided with a plurality of first branch pipes which are respectively connected with an ultrahigh pressure cylinder rear shaft seal, an ultrahigh pressure cylinder front shaft seal, a high pressure cylinder front shaft seal, a high pressure cylinder rear shaft seal, a middle pressure cylinder front shaft seal and a middle pressure cylinder rear shaft seal, and the pipeline between the shaft-seal main pipe and the ultrahigh pressure cylinder front shaft seal is provided with the electric heating control station; the shaft-seal main pipe is also provided with a plurality of second branch pipes which are respectively connected with the auxiliary steam supply station,the overflow control station and the temperature reduction control station; and the tail end of the shaft-seal main pipe is also connected with a steam supply port of the low pressure cylinder shaftseal by virtue of the temperature reduction control station. The invention also provides a control method of the shaft-seal steam supply system for the secondary reheat unit. By adopting the shaft-seal steam supply system, the steam supply temperature of each shaft-end shaft seal can be accurately controlled, the power and size of an electric heater can be reduced, and the operation economical performance of the unit can be improved.

Description

technical field [0001] The invention relates to the field of thermal power plants, in particular to a shaft seal steam supply system for a double reheat unit and a control method thereof. Background technique [0002] The main function of the steam turbine shaft seal system is to provide a suitable steam source for the end shaft seal seal under various working conditions of steam turbine startup, operation and shutdown; Leakage of steam and steam-gas mixture from the valve stem of the steam valve to prevent steam from leaking into the plant; or air in the atmosphere leaks into the low-pressure cylinder, affecting the vacuum of the unit. [0003] The shaft seal system includes a shaft seal steam supply system and a shaft seal leakage system. At present, the conventional 600MW-1000MW capacity primary reheating unit generally adopts a self-sealing shaft seal system: during the start-up, shutdown and low-load operation stages of the unit, the steam supply for the shaft seal is ...

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Problems solved by technology

[0006] In general, the above-mentioned improvement methods currently have the following disadvantages: (1) The steam supply temperature of the high and medium pressure cylinder shaft seals is too high, and the gap between the shaft seals increases, which affects the economical efficiency of the unit; (2) The amount of auxiliary steam supplied for heating is too high Large, large selection of electric heaters, difficult layout, and high power consumption; (3) The steam source supplied to the low-pressure shaft seal is first heated by the electric heater, and then sprayed with water at the cooling station to reduce the temperature, resulting in a huge waste

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