Copper in Boiler Feedwater

[GBurns]

I have long believed that elevated copper levels in feedwater is bad. What I am ignorant on is the damages that may result in boilers from 600 psig to 1500 psig. Any information on this subject would be appreciated.

 

[Metalguy]

The Cu can cause greatly increased corrosion of steel in such conditions, especially in creviced areas.

In the nuke industry the secondary side of PWRs (~1100 psi) are separated into two general groups--Cu free and Cu-containing. Only newer plants and reworked older ones are Cu free, and as a result (along with other things) generally do not have the same type of problems in the steam generators (corrosion of Alloy 600 tubing where it passes thru the tube supports).

 

[kclim]

I'm assuming it's a power plant related querry. At high pressures, contaminant copper can carry over in the steam and deposit itself of turbine blades, leading to a decrease in cycle efficiency.

And as Metal guy said, it can increase the corrosion rate of steel (boiler tubes), usually via an underdeposit corrosion or galvanic mechanism.

Heavy deposition is usually a result of feed water heater corrosion, that is if the feed waters are made from a copper alloy. Feed water heaters on the power plants I've seen are either of the carbons steel or stainless variety.

Good feed water chemistry control can mitigate the problem somewhat. pH in particular is important to control - the optimum feed water pH depends whether your system contains FW heaters or not.

Can't tell you about how things work in the nuclear power industry... don't have any nuclear power stations in Australia!