Reducing hardness in boiler water

ssnowder

Question: Will increasing bottom blowdown frequency reduce the hardness of boiler water? Our Nalco rep recommended reducing blowdowns from once per shift to once per week. Recently our boiler tests up to 50 ppm hard. Our feedwater is tested every shift and thus we never feed hard water to our boiler. Our chemical levels are spot on, even a little high.

ssnowder

Dan Holohan?

Jamie Hall

Is this a process -- once though -- appllication? At least in part? Or is it a closed loop? Little or no routine feedwater?

In either case reducing the frequency of blowdowns will increase the level of chemicals -- including hardness -- in the boiler water. The reason being that any chemicals in the fee water become concentrated in the boiler water, unless they precipitate out (hardness will, depending on pH and level, for instance) as steam is produced -- steam being pure water. Blowing down the boiler reduces the chemical level back towards what the feedwater concentrations are.

ssnowder

I operate a steam plant at a prison in CA. Our condensate return system has excessive leakage, in the amount of 4,000 gallons per day. I know that increasing surface blowdowns will somewhat decrease the hardness. I am trying to get a consensus of opinion on bottom blowdowns effect on hardness reduction. Thanks.

Jamie Hall

And we think residences have excess condensate losses! Bottom blowdowns will have the advantage of removing some of the settled crud in the boilers -- if any -- as well as reducing overall hardness. Any blowdown will have the beneficial advantage of reducing the total dissolved solids, which is the other thing you want to keep an eye on, since excess TDS can cause real problems with foaming and water carryover -- which hurts your efficiency.