火电站直接空冷凝汽器积灰监测

火电站直接空冷凝汽器积灰是影响传热性能的重要因素,研究直接空冷凝汽器积灰对传热性能的影响规律并提出监测措施具有重要意义。通过分析汽轮机背压与汽轮机排汽量、冷却空气流量、凝汽器传热系数、凝汽器总传热面积以及环境温度之间的关系,得到了空冷凝汽器在维持汽轮机排汽量和冷却空气量不变时,汽轮机背压和传热系数之间的关系以及凝汽器积灰对汽轮机背压的影响。研究表明:凝汽器积灰会导致凝汽器传热系数降低,汽轮机背压升高,机组运行经济性下降。设计工况下,当蛇形翅片扁平管结构凝汽器积灰厚度达到1.2 mm时,汽轮机背压将增加50%左右。通过监测空冷机组运行过程中汽轮机背压的变化,可预报积灰的程度,为直接空冷凝汽器清洗提供一定的理论依据。

Monitoring of Dust Accumulation on Direct Air-cooled Steam Condensers in Thermal Power Plants

The dust accumulation on direct air-cooled condensers is a major factor affecting their heat transfer performance.It is of great significance to study the law governing the impact of dust accumulation on direct air-cooled condensers in respect of heat transfer performance and come up with adequate monitoring measures. Through an analysis of the relationship of steam turbine back pressure with turbine exhaust-steam flow rate,cooling air flow rate,condenser heat transfer coefficient,condenser total heat transfer area and ambient temperature,the relationship of steam turbine back pressure and heat transfer coefficient was identified along with the effect of dust accumulation of the condenser on steam turbine back pressure when steam turbine exhaust-steam flow rate and cooling air flow rate for the air-cooled condenser are kept constant.The study indicates that the dust accumulation on a condenser can lead to a decrease in heat transfer coefficient of condensers,an increase in steam turbine back pressure and a decrease in turbine unit operating efficiency.Under design operating conditions when dust accumulation on finned spiral flat tube-structured condensers has a thickness of 1.2 mm,the steam turbine back pressure will increase by about 50%.Through a monitoring of the change in steam turbine back pressure during the operation of an air cooled turbine unit,the degree of dust accumulation can be forecasted,thus providing a theoretical basis for cleaning air cooled condensers.