Which processes are used to control secondary system chemistry?

• A. Ion Exchange; Filtration; Steam Generator Blowdown
• B. Electrolysis; Distillation; Filtration
• C. Ion Removal; Filtration; Boiler Blowdown
• D. Adsorption; Crystallization; Recirculation

Answer: (A)

In the steam/condensate (secondary) loop, the aim is to keep dissolved solids and particulates at levels that prevent corrosion, scaling, and fouling of turbines and heat exchangers. Ion exchange is used to remove ionic impurities from the water, swapping undesirable ions with benign ones on resin beds to produce cleaner water with lower conductivity. Filtration physically removes suspended solids and particulates that could foul surfaces or cause erosion, helping protect components and improve heat transfer efficiency. Steam generator blowdown periodically removes concentrated water from the boiler or generator, controlling the concentration of dissolved solids and keeping the cycle chemistry within safe limits to prevent scaling and corrosion.

These three together address the main avenues of secondary-chemistry control: removing ions, removing solids, and diluting/replacing concentrated impurities. Other processes listed don’t align with standard secondary-system chemistry control in this context; they aren’t routinely used to manage the same combination of dissolved ions, particulates, and concentration that this system requires.