Biofilm in heat exchanger

GS not at home.com
Sat May 8 11:01:01 EST 2004


"Johan Guldbj?rnsen" <johanag at online.no> wrote in message
news:a2b656d2.0404290354.6aa63e44 at posting.google.com...
 > > approx 0,2 g/l Ca(OH)2 is added and  approx 200L 75% H3PO4 i added.
 >
 > In the heat exchangers the process water is cooled from 40-48 C to
 > 30-34 C, the cooling water has a temperature approx 4C in the winter
 > increasing to approx 20 C in the summer.

 > Move the dosing location of Ca(OH)2 and H3PO4 to after the heat
 > exchangers

You don't mention the pH of the process water. At neutral pH at least, you
will probably get precipitation of relatively insoluble calcium phosphate.
Another possible factor is if there is any alginate present in the water or
produced by the organisms growing on the heat exchanger - add calcium to
alginate and you will produce a relatively rigid gel. Either way, if you can
move the calcium addition downstream of the heat exchanger it may help.

Graham Shepherd


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