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Proceedings of Symposium on Energy Engineering in the 21<sup>st</sup> Century (SEE2000) Volume I-IV

ISSN:
1-56700-132-7 (Print)

STUDY ON ASH DEPOSITION CHARACTERISTICS OF DIFFERENT TYPES OF COALS

Miki Shimogori
Thermal Power Research Department Babcock-Hitachi K.K.Kure Research Laboratory

Noriyuki Ooyatsu
Thermal Power Research Department Babcock-Hitachi K.K.Kure Research Laboratory

Noboru Takarayama
Thermal Power Research Department Babcock-Hitachi K.K.Kure Research Laboratory

Akira Baba
Thermal Power Research Department Babcock-Hitachi K.K.Kure Research Laboratory

Abstract

Understanding ash-deposition mechanism and factors decreasing heat flux through a heat-transfer surface is useful for operating pulverized coal-fired boilers efficiently and reliably. We studied ash-deposition process through a monitoring test using a portable device, and confirmed that it generally consists of three main stages: formation of a powdery ash layer, particle impact and sticking, and deposit growth. We also studied an effect of ash deposition on heat-flux decrease for three types of coals through up to about 100-hour combustion tests in a large-scale test furnace. Powdery ash layers, formed during the tests for two of the coals, decreased the heat-flux dramatically. Our analysis of the ash samples showed that for one of the coals, a large amount of Na and K vapor condensed on the surface of the layers, and for the other coal, the layers contained a high percentage of fine ash particles under 10μm.