Shaft seal steam supply system used for ultra supercritical unit and provided with electric heater

Abstract

The invention discloses a shaft seal steam supply system used for an ultra supercritical unit and provided with an electric heater. The shaft seal steam supply system comprises a shaft seal mother tube, a high-pressure cylinder rear shaft seal, an intermediate-pressure cylinder rear shaft seal, a high-pressure cylinder front shaft seal, an intermediate-pressure cylinder front shaft seal, low-pressure cylinder shaft seals, a water spraying desuperheater, an electrical heating device module and connecting pipelines. An inlet of the shaft seal mother tube is connected with an auxiliary steam station through an auxiliary steam adjusting valve. An outlet of the shaft seal mother tube is directly connected with the high-pressure cylinder rear shaft seal and the intermediate-pressure cylinder rear shaft seal. The high-pressure cylinder front shaft seal and the intermediate-pressure cylinder front shaft seal are connected with the shaft seal mother tube through the electrical heating device module. The shaft seal mother tube is connected with the low-pressure cylinder shaft seals through the water spraying desuperheater. The electrical heating device module comprises an electric heating and steam supply check valve branch, a steam leakage check valve branch and a bypass pneumatic valve branch which are connected in parallel. Differential pressure transmitters which are linked to the electrical heater and a bypass pneumatic valve correspondingly are connected to the two ends of the electrical heating device module. The electric heater is linked to cold and hot states of a steam engine. By the adoption of the shaft seal steam supply system, the situations that the thermal stress of the shaft diameter is too high, and a main shaft is locked can be avoided.

Description

technical field [0001] The invention relates to a shaft seal steam supply system for a steam turbine in a thermal power plant, in particular to a shaft seal steam supply system with an electric heater for an ultra-supercritical unit. Background technique [0002] Ultra-supercritical units usually adopt high and medium pressure split cylinder structure, especially for units with medium pressure single split flow design, the rotor temperature difference at the front and rear shaft seals of high pressure cylinder and medium pressure cylinder is very different; during operation, the front shaft seal of high pressure cylinder and the medium pressure cylinder The temperature of the rotor at the front shaft seal is relatively high, while the temperature of the rotor at the rear shaft seal of the high-pressure cylinder and the rear shaft seal of the medium-pressure cylinder is relatively low; The sealing steam source should ensure that the temperature difference between the shaft se...

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Problems solved by technology

[0003] Power plant shaft seal steam supply usually adopts auxiliary steam as the steam supply source of shaft seal, which can meet the steam supply temperature requirements of shaft seal after high-pressure cylinder and rear shaft seal of medium-pressure cylinder in hot state and extremely hot state, but cannot meet the requirements of steam supply before high-pressure cylinder. High-temperature steam supply requirements for the shaft seal and the front shaft seal of the medium-pressure cylinder; when the conventional unit is started in a hot state or an extremely hot state, it mainly relies on the steam supply from the main steam station or adds an electric heater to the auxiliary steam station to provide high-temperature steam source. Although the system is simple, it can only provide one steam supply temperature for each steam seal of the high and medium pressure cylinders, and cannot perform independent temperature matching for the front shaft seals of the high and medium pressure cylinders and the rear shaft seals of the high and medium pressure cylinders. Conventional steam supply from the main steam station or adding an electric heater to the auxiliary steam station, the mismatch between the temperature of the steam supplied by the shaft seal and the temperature of the rotor is still prominent, and the problem of matching the temperature of the steam supplied by the rotor and the steam supplied by the shaft seal is not fundamentally solved

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