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Fire in bag house serving Galvanizing line

April 3, 2014

Q. I read a post where Dr. Thomas Cook had indicated that the blowing (zinc) dust reacts violently when it comes in contact with water (letter 45817). I am working on an investigation that currently involves a fire at a bag house serving a pipe galvanizing line. Specifically, the bags ignited, nothing else appears to have combusted. The bag house is part of a system that collects fumes from the kettle and the pipe blowing station. Superheated steam is used in the blowing station with with heated air injected into the ductwork downstream of the blowing station to keep the fume temperature above the dew point. A centrifugal separator is located further downstream of the hot air injection point to remove any large zinc particles.

Have you seen situations of bag house fires due to moisture carry-over (i.e., temperature drops below the dew point) from the blowing station? Although the steam is superheated when it enters the pipes, it mixes with cold air at the fume collection hood and can be expected to cool to below the dew point along the duct work. The dust collected in the bag house is expected to be a combination of zinc oxide, ammonium chloride, zinc chloride, and zinc particles that pass beyond the separator. The bags are cleaned by air pulses - refrigerated driers on the air supply.
Thanks
Tom

Tom Traubert
- Windsor, Connecticut, USA