Boiler water recirculation system and method for preventing overtemperature of hearth water wall under low load

Abstract

The invention discloses a boiler water recirculation system and method for preventing overtemperature of a hearth water wall under low load. The system comprises a boiler water circulating pump, a steam-water separator, a main water storage tank, a water wall middle mixing header, a water wall lower header and a coal economizer. The coal economizer, the water wall lower header, the water wall middle mixing header and the steam-water separator are sequentially connected through pipelines. A coal economizer inlet pipeline of the coal economizer is connected with a water supply pipe. A gas outletof the steam-water separator is connected to a superheater. A liquid outlet of the steam-water separator, the main water storage tank and the boiler water circulating pump are sequentially connectedand connected to the coal economizer inlet pipeline. The water wall middle mixing header is connected with a bypass water storage tank through a bypass water delivery branch pipe. A water outlet of the bypass water storage tank is connected with an inlet of the boiler water circulating pump. By means of the system, the problems that due to low flow of low-load working media, the water wall is overheated, and the wall temperature fluctuates substantially can be avoided, and transverse cracks are relieved.

Description

technical field [0001] The invention belongs to the technical field of equipment safety in coal-fired thermal power plants, and in particular relates to a boiler water recirculation system and method for preventing overheating of a furnace water wall under low load. Background technique [0002] With the continuous increase of the proportion of new energy sources, coal-fired units participate in deep peak regulation, frequently increase and decrease the load, the fluctuation frequency and amplitude of working medium parameters in the water-cooled wall change greatly, and the wall temperature deviation of the water-cooled wall on the same screen is large, resulting in large thermal stress. During the operation of Taiwan's super (super) critical once-through boiler, the fatigue stress caused transverse cracks on the fire side of the water-cooled wall, and even leaked and shut down the boiler, which seriously threatened the safety and stability of the unit. [0003] Under the l...

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Problems solved by technology

[0005] Aiming at the problems of overheating and large fluctuations in wall temperature in the prior art, the purpose of the present invention is to provide a furnace water recirculation system and method for preventing overheating of the furnace water wall under low load. Overheating of the water-cooled wall and large fluctuations in wall temperature can alleviate problems such as transverse cracks in the water-cooled wall

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