System for improving steam supply safety of low-pressure shaft seal of thermal power plant and design method

Abstract

The invention discloses a system for improving steam supply safety of a low-pressure shaft seal of a thermal power plant and a design method. An auxiliary steam pipeline and a reheating cold section steam pipeline communicate with a shaft seal mother pipe, a condensed water pipeline communicates with an atomizing spray head through a desuperheating water regulating valve, a shaft seal mother pipe bushing is arranged at the atomizing spray head, shaft seal mother pipe drainage devices are arranged at the front end and the rear end of the shaft seal mother pipe bushing, a steam leading-out opening is formed in a shaft seal mother pipe, the steam leading-out opening communicates with one end of a first low-pressure shaft seal steam inlet branch pipe and one end of a second low-pressure shaft seal steam inlet branch pipe through a low-pressure cylinder shaft seal steam inlet mother pipe, and the other end of the first low-pressure shaft seal steam inlet branch pipe and the other end of the second low-pressure shaft seal steam inlet branch pipe communicate with a low-pressure shaft seal in a low-pressure cylinder of a steam turbine; a first low-pressure shaft seal steam inlet branch pipe temperature monitoring device is arranged on the first low-pressure shaft seal steam inlet branch pipe, and a second low-pressure shaft seal steam inlet branch pipe temperature monitoring device is arranged on the second low-pressure shaft seal steam inlet branch pipe. The system can achieve automatic and stable control over the low-pressure shaft seal steam inlet temperature, and the safety of low-pressure shaft seal steam supply is improved.

Description

technical field [0001] The invention belongs to the technical field of steam turbine safe operation, and relates to a system and a design method for improving the steam supply safety of a low-pressure shaft seal in a thermal power plant. Background technique [0002] At present, the shaft seals of large steam turbines are all self-sealing structures. The low-pressure cylinder shaft seals supply steam through the high- and medium-pressure cylinder shaft seals, and the leaked steam enters the low-pressure cylinder shaft seals after being cooled by water spray. In order to ensure the safety of the low-pressure shaft seal and the shaft seal, the temperature of the shaft seal entering the low-pressure cylinder usually needs to be controlled at 121-177°C, and the pressure is around 0.13MPa. [0003] However, the steam intake of the shaft seal of the low-pressure cylinder is relatively small. Taking a 350MW supercritical unit as an example, the rated steam intake is 1.6t / h, and the...

AI Technical Summary

Problems solved by technology

If the inlet steam temperature of the low-pressure shaft seal is controlled too high, it will cause severe overheating of the front and rear end steam seals of the low-pressure cylinder, resulting in a larger gap between the shaft seals, increased steam leakage from the shaft seal, and condensed water in the steam supply of the lubricating oil system. Condensed water escapes into the lubricating oil return system, resulting in unqualified lubricating oil quality

If the inlet steam temperature of the low-pressure shaft seal is controlled too low, it will cause the shaft seal to enter the steam with water, and the phase change will pose a serious threat to the safety of the shaft seal and the safe operation of the unit

Images