A steam supplier for a large town in central Pennsylvania had a problem with low pH steam condensate and subsequent corrosion of steel metallurgies. One option to remedy the situation was by chemical addition. There were a few chemical options to consider but all involved chemical purchase, addition, monitoring and some can cause problems with direct contact contamination. A dealkalizer was also considered to remove boiler feedwater alkalinity prior to site softeners. Removing alkalinity reduces production of carbonic acid in the condensing steam and subsequently raise the pH. A dealkalizer represents a capital cost and operation does require additional labor and water usage for the regeneration of the unit(s).
The next alternative considered was a decarbonator. A decarbonator mechanically removes alkalinity by breaking it down and venting CO2 out of the top of the unit; thus inhibiting production of carbonic acid in the condensing steam. A decarbonator does require initial investment but the ongoing operation is not labor intensive. Electricity used is intermittent for forwarding pumps and a small fan used for induced draft. Regeneration is not necessary and no wastewater is generated.
Considering the alternatives, the site chose a decarbonator installation to solve their low pH condensate. The site was able decrease their incoming alkalinity by 90% and therefore neutralize condensate pH.
In this case, a decarbonator was successful providing alkalinity removal and condensate pH increase, these units can also provide many other operational benefits.
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