Problem 5.9: The chapter describes two strategies for

From Chapter 5 Problem Set. Level 3: System Integration.

Question

The chapter describes two strategies for managing carbonate in boilers: neutralize alkalinity upstream or neutralize acidity downstream. In 2–3 sentences, explain what each approach targets and why alkalinity must be controlled either way.

Answer

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Upstream treatment, such as reverse osmosis or dealkalization, removes bicarbonate before it enters the boiler. This greatly reduces alkalinity-derived CO₂ formation and helps control the condensate corrosion pathway. Downstream treatment uses neutralizing amines that volatilize with steam and condense with water, raising condensate pH and neutralizing acidity before carbonic acid can attack metal. Either way, alkalinity must be controlled because bicarbonate can thermally decompose into CO₂ inside the boiler, and that CO₂ can travel with steam, re-dissolve in condensate, lower pH, and create a corrosive environment.