coal selection criteria for industrial pfbc firing project 3.2 - CCSD
coal selection criteria for industrial pfbc firing project 3.2 - CCSD
coal selection criteria for industrial pfbc firing project 3.2 - CCSD
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“Coal Selection Criteria <strong>for</strong> Industrial PFBC Firing”<br />
Furthermore, the major reason causing several operational shutdowns of the Escatrón<br />
plant in Spain was cyclone ash extraction system blockage (Scott and Carpenter 1996).<br />
Sintered material (agglomerates) deposited on the cyclone walls and in the ash extraction<br />
system. Increasing the <strong>coal</strong> feed rate to increase the production of steam increased the<br />
bed height and the flow of particulates to the cyclone. This led to more agglomeration<br />
which blocked the cyclone. Moreover, the complex design of cyclones with many ducts<br />
and flow direction changes further intensified the plugging. Modifications to the cyclone<br />
ash removal system have reduced the problem (Martinez and Menendez 1995), (Martinez<br />
and Menendez 1994).<br />
3.5 Filter Blockage<br />
This problem is only faced by PFBC plants which depend on the ceramic filter <strong>for</strong><br />
secondary hot gas clean-up prior to the gas turbine inlet, an example of such plants is<br />
Tomatoh-Atsuma in Japan. This problem involved filter blockage, filter breakage, gas<br />
leakage and fires, attributed to temperature effects, hydrodynamic effects, mechanical<br />
effects, filter material effects, sorbent properties/reactions, ash composition effects and<br />
volatilisation / condensation of alkalis (Stubington 1997). Most of them have been solved<br />
but the problem is being investigated further to improve the understanding of ash<br />
chemistry.<br />
Finer ash particles penetrate into the filter, causing filter blockage. This ash was<br />
described as sticky due to its tendency to stick on the filter surface and it could not be<br />
removed by cleaning. It led to unstable pressure drop across the filter cake (Stubington,<br />
Wang et al. 1998). Excessive deposits could lead to filter breakage. Larger ash particles<br />
in the exhaust gas flow to the filter reduced the blockage, thus easing the cleaning of<br />
filter cake. This solution was demonstrated at Wakamatsu.<br />
Elutriated material from the attrition of limestone bed particles contained calcium<br />
compounds that could <strong>for</strong>m low melting point eutectics which decreased the ash fusion<br />
temperature of material accumulated in the filter cake. A higher Ca:S ratio was necessary<br />
to maintain the bed height <strong>for</strong> low-sulfur Australian <strong>coal</strong>s. This neutralized the high ash<br />
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