Silica and Iron

1. None

2. Just a little.

3. Just a little more.

4. Perform boiler blowdown, start over.

So why aren't you on the phone to the boiler manufacturer, then?

Lots of Iron, lesser (much lesser) of Silica.

The way this should go is you make yourself familiar with material specifications for steel. Iron is a crucial component for your material and would be in the range 90 to 99%.

Then there is certain standards that cater for boiler materials. I would not know more because its not my line of business. But I can tell you that there will be more to look at not only iron and silica.

Oh bugger wait. Its the water.

Me thinks the more iron in water the less in the pipe and boiler material. Where is silica coming from? Would the water not have to be clean by any standards?

Please note there was a coffee in between both answers.

It does speak for the coffee. Organic home brew! No iron in the water.

Let alone Irony! Cup is Ceramic. Main ingredient is Silica. Where is all this going?

I might summarize: Dont use coffee as boiler feeder water nor water that looks like same.

Boilers have to have limits on silica and iron (in the generating tubes, yes and in the final superheated steam even more so) because of (1) protection of steam turbine from silica/iron deposits, that will spall off unevenly and produce excessive vibration, and (2) for protection of heat transfer critical rate on the tube surfaces in the boiler, in order to prevent fouling or scaling of tubes that will cause rupture by overheating.

The limit on silica in superheated steam to any boiler anywhere at any pressure, temperature, and capacity is very simply put : 20 ppb (parts per billion), 20 micrograms/L. The limit on iron is similarly put but may be slightly higher at 25-30 ppb, due to the slightly less adherent nature of some iron oxides. Caution needs to be made that heavy iron oxide loading due to excessive corrosion in the boiler, and/or insufficient blow-down will result in long-term steam turbine blade erosion, and this will shorten the life of the project by tens of years. If water chemistry in the boiler is well maintained, the boiler is not cycled on a daily basis from offline to back online, then there is a good chance you can keep the iron down to about 10-15 ppb.

I keep watch on steam plants not unlike yours, and we try to maintain condensate feeding the boilers at below 10 ppb, and in the instances where we inject water to a gas turbine, there are even more strict limits of just 10 ppb in the water that contacts the very hot blading of these turbines.