Power station air cooling system adopting combined refrigeration with shaft seal steam leakage of steam turbine and continuous blow-down waste heat of boiler as well as method for predicting heat-transfer coefficient of air-cooling condenser

Abstract

The invention discloses a power station air cooling system adopting combined refrigeration with shaft seal steam leakage of a steam turbine and continuous blow-down waste heat of a boiler. The system is characterized in that the steam turbine is communicated with a steam source, the steam turbine is connected with an electric generator, and the steam turbine is sequentially communicated with an air-cooling condenser, a condensate pump and boiler feedwater; the steam turbine is sequentially communicated with a steam leakage condenser, a steam leakage condensate pump and the boiler feedwater; boiler blow-down water is sequentially communicated with a flash tank, a deaerator, a working medium superheater and a drainage ditch; the steam leakage condenser is sequentially communicated with the working medium superheater, and a generator is communicated with the steam leakage condenser through a working medium circulating pump; the generator is sequentially communicated with a condenser, a first throttling valve and an evaporator, the evaporator is communicated with an absorber, and the generator is sequentially communicated with a second throttling valve, the absorber, a solution pump and a generator; and air is sequentially communicated with the evaporator, an induced draft fan and the air-cooling condenser. A method for predicting a heat-transfer coefficient of the air-cooling condenser is further provided.

Description

technical field [0001] The invention relates to the technical field of steam turbine exhaust air cooling in a thermal power station, and relates to an air cooling system of a steam turbine shaft seal combined with waste heat from boiler continuous sewage discharge and a heat transfer coefficient prediction method of an air-cooled condenser. Background technique [0002] The thermal power unit whose exhaust steam of the steam turbine is air-cooled is called an air-cooled unit. According to the direct or indirect air cooling method, it is divided into a direct cooling unit and an indirect cooling unit. The cooling system is called a direct cooling system and an indirect cooling system. Among them, my country It is mainly based on direct cooling units. Due to its good water-saving performance, direct cooling units have been widely used in coal-fired power stations in my country's coal-rich and water-short Northeast, North China, and Northwest ("Three Norths") regions, although i...

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Problems solved by technology

One of the reasons is that the air-side heat transfer coefficient of the air-cooled condenser is low, and its heat transfer area is dozens of times that of the water-cooled condenser, resulting in a design initial temperature difference as high as 38°C to 40°C. The operating back pressure is as high as 30kPa or more, even reaching 50kPa and approaching the back pressure of its low vacuum protection action

[0003] In addition, there is a large pressure difference on both sides of the balance piston seal of the high-parameter and large-capacity steam turbine in a large-scale power station. During operation, some steam will leak through the balance piston in the high, medium and low pressure cylinders of the steam turbine, which is called steam turbine shaft seal leakage. The air leakage rate of the balanced piston seal of the medium pressure cylinder alone can reach 3% to 6%, and the air leakage rate of the medium pressure cylinder of the 600MW unit can reach 50t / h to 60t / h. In actual operation, the steam turbine is only cooled by cooling water The shaft seal leakage is condensed into condensed water and sent to the boiler to make up water, and the cooling water outlet temperature is about 70°C. Because of its low temperature, there is no relevant utilization technical plan in large power plants

At the same time, during the operation of drum boilers in large-scale power stations, the quality of boiler water is often regulated by means of continuous sewage discharge. On the one hand, the drain temperature after capacity expansion is relatively high, which can be as high as 100°C to 180°C. However, the current large-scale power plants have no relevant technical solutions to utilize this part of the heat. Basically, it is directly sent to the drainage ditch during field operation, resulting in Larger heat loss

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