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When we had turn around in amine treating unit, sulfur recovery plant, we found almost outer tube side covered completely by hard scale. We suspected that it came from degraded solvent (amine compound) during regeneration. We had already been cleaning with chemical agent, but it showed unsatisfied result. Does anyone have similar experience? What recommended cleaning technique should be done?
 
Answers
10/08/2010 A: Morgan Rodwell, Fluor Canada Limited, morgan.rodwell@fluor.com
It is possible that this is a hardness scale, if the makeup water to the amine system is not clean (steam condensate). I have seen this is a gas plant amine system in the 1990s where an untreated water was used as makeup. The scale may be removable with an acid wash, but may require mechanical cleaning. Can you get a sample of the scale for analysis? This may also help figure out where it is coming from.
04/08/2010 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
If the exchanger has a square pitch then a very new patented technology called FlatJett (tm) or PlateJett will clean "between the tubes" even if the gap is 5mm.
See: http://www.tubetech.com/case-studies/refineries-case-studies/world-first-mechanical-between-tubes-shell-side-cleaning-of-vcfe-texas-tower
http://www.tubetech.com/case-studies/petrochemical-case-studies/impossible-polymer-shell-side-fouling-of-exchanger-cleaned-to-bare-metal
PlateJett an FlatJett technology has successfully removed cured polymer, hydrocarbon cokes, iron oxides that has completely bridged, scaled and choked the shell side. The system can be used either with low water volume or a zero waste medium.
Chemicals often have the following disadvantages:
1. Approx 2m per second flow to ensure sufficient shear force and activity is achieved. If the inlet and drain are the wrong size then the cleaning will be limited
2. A flow path and will take the least path of resistance
3. Blockages, inert scale, metallurgy differentials will also impact on chemical cleaning success, not least environment.