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In our RFCC we have a purge treatment unit to remove the catalyst fines from the flue gas before leaving through the stack. The PTU utilizes about 25 m3/hr water for scrubbing and this water after clarification and oxidation leaves the unit as discharge. I would like to know about the possible destinations for the treated PTU water and availability of alternate methods which does not require water for scrubbing.
 
Answers
30/03/2015 A: Eric Hennings, Technip Stone & Webster, EHennings@technip.com
Purge rate will be a function of solids loading in the scrubbing liquor. To reduce fines loading in the flue gas, eliminate any high velocity interfaces between gas and catalyst. We recommend a detailed survey of all gas injection points. One FCC was able to reduce the flue gas scrubber solids by over 50% after remediation of many gas injection points.
There are scrubber designs which use once-through seawater.
Fresh water make-up can consist of alternate streams already destined for water treatment, as long as contaminants are low in certain contaminants.
If solids are the only issue, ESP can be used.