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CPOTE2020 logo
6th International Conference on
Contemporary Problems of Thermal Engineering
Online | 21-24 September 2020

Abstract CPOTE2020-1203-A

Book of abstracts draft
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Experimental studies on vibration of superheater pipes caused by a sonic soot blower system working in the 670MWth circulating fluidized bed boiler

Paweł MIREK, Czestochowa University of Technology, Poland

In Circulating Fluidized Bed (CFB) boilers fired with fossil fuels, the use of an effective system for cleaning heated surfaces from ash fouling is essential to maintain maximum thermal efficiency. Among the ash blowers currently used, steam blowers are the most popular. They owe their popularity primarily to their high efficiency, resulting from the parameters of the working medium. Unfortunately, according to the operating experience, these devices, apart from high operating costs, are also the source of many problems related mainly to the erosive impact of ash carried away with the steam stream. An alternative method of ash fouling removal is the use of an acoustic wave of high sound intensity and low frequency emitted by sonic soot blowers. With these devices, there is a risk of damage resulting from the movement of vibrating heat exchanger pipes. The article presents the results of measurements of vibrations of the pipes of the convection steam superheater installed in the convection pass of a CFB boiler of the 670 MWth induced using sonic soot blowers of the Nirafon NI-100 type. The measurements were made using two ICP Triaxial 356A16 accelerometers allowing the analysis of accelerations in the maximum range of ±490 m/s2 and the G.R.A.S. 40BH microphone recording acoustic pressure up to 194dB. The measurements and spectral analysis of the recorded signals showed that the level of acoustic pressure generated by the acoustic cleaners for the frequency of 100 Hz was too low for the efficient cleaning of the heated surfaces of the reheater RH2 and superheater SH3. Besides, it has been shown that the acoustic wave of 148 dB is safe for the steam superheater pipes causing vibrations of maximum amplitude not exceeding 1 mm. Thus, it seems that the dominant mechanism for cleaning the surfaces of the superheater's heating pipes are not pipe vibrations but the breakage of cohesion forces between dust particles.

Keywords: Circulating fluidized bed boiler, Acoustic cleaners, Sonic soot blower, Vibration analysis, Superheater