大型回转式空气预热器低负荷运行采用冷端间隙调节装置降低漏风分析

Analysis for Low Load Operating Air Preheater with Cold End Leakage Control System

空气预热器冷端密封间隙为按照锅炉最大运行工况设定,在锅炉高负荷运行时,能维持在较小的间隙和较小的冷端漏风率,但长期在低负荷下运行时,由于转子的热变形变小,会导致空气预热器冷端间隙增大。空气预热器直径越大,这种现象就越明显。为控制大直径空气预热器低负荷运行时的冷端漏风,提出了通过在冷端加装密封板自动调节装置的思路。计算表明:采用该装置能有效降低总漏风率和一次风漏风率,并大幅度降低冷端漏风占直接漏风的比率。通过冷端和热端漏风控制系统的控制模式做了分析,计算了1台660 MW机组分别采用单列和双列空气预热器布置时,采用冷端漏风控制系统的经济收益和投入回报期。

The cold end radial seal gaps were set according to the rotor deformation range when the boilers operate in maximum load, and can maintain the small leakage gap and small cold end radial leakage can be given only at high load. If the boiler load is kept in longtime at low level, operation will cause the bigger leakage gap and bigger air leakage in air preheater＇ s cold end. This phenomenon will be more obvious for a bigger diameter size air preheater. Using cold end leakage control system can improve it. This paper gives the way by adding cold end seal plate adjusting device to change the seal plate level, and keep it follows the rotor cold end position, so it can give small leakage gap at any boiler loads. By calculation, this system can effectively lower the total air leakage ratio and primary air leakage, and cut the ratio of cold end leakage in total direct leakage to a great extent. Also, this paper also analyzes the appropriate controlling manner for hot end and cold end leakage control systems, and make the economic analysis and the payback periods for one 660 MW boiler with two kinds of air preheater arrangement, two or one air preheater（s） respectively in boiler system.