Controlling fumes from hot dip sheet galvanizing kettle

We are in the galvanizing industry for the last forty years and our bath for galvanizing sheet constitute the following.

1. Kettle; made out of AG steel of thickness 32 mm and measuring 2400 L x 1600 W x 1100 H.

2. Molten lead; 32 MT

3. Flux box; Containing molten ammonium chloride floating on lead.

4. Zinc box; containing molten zinc 4 MT floating on lead.

5. Guider; made out of mild steel mounted on the kettle to guide the sheets.

6. Pair of flux rollers; to drive the sheets in to the bath for galvanizing.

7. Pair of finish rollers; to drive the zinc coated sheets out.

8. Magnetic rollers; to deliver the sheets.

9. Sprayer; to spray ammonium chloride powder by an air blower on zinc coating to provide an inert atmosphere preventing oxidation.


Galvanizing bath is enclosed in a furnace heated by heavy duty oil burners to a maximum of 950 °C.


Emission from galvanizing consists of white ammonium chloride fumes which is extracted by a 20 HP motored fan and sent out to air through a 45 feet tall stack.


Our main problem is to control the emission to a minimum level and to avoid air pollution which is mainly due to the ammonium chloride powder. The bath temperature is maintained at 450 - 460 °C.


How can we minimize the air pollution? Is there any alternative to the existing method?


The zinc we use is 99.995% pure.


Your early reply will be very much appreciated.


Best Regards.

adv.
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