In boiler-feed-water conditioning, which unit process is used specifically to remove dissolved (soluble) silica from the water?

Introduction / Context:
Silica control is a critical objective in boiler-feed-water treatment because silica volatilizes and deposits on turbine blades and heat-transfer surfaces, reducing efficiency and causing maintenance issues. Unlike suspended solids, dissolved silica requires a selective removal step.

Given Data / Assumptions:

• Target constituent: dissolved (reactive) silica, not particulate silica only.
• Boiler duty may require very low silica (ppb levels) for high-pressure systems.
• Common pretreatment steps (coagulation, filtration) chiefly remove turbidity and colloids.

Concept / Approach:
Dissolved silica (as monomeric silicic acid species) is effectively removed by strong-base anion (SBA) exchange resins, often in conjunction with demineralization trains (cation exchanger → degasser → anion exchanger → mixed bed). Coagulation/filtration are insufficient for dissolved silica; thermal conditioning may shift equilibria but does not reliably meet low-silica specifications.

Step-by-Step Solution:

Verification / Alternative check:
Boiler water handbooks specify SBA or weak-base + strong-base sequences for silica control, with mixed-bed polishing where required.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing particulate turbidity control with dissolved silica removal; overlooking need for resin regeneration and silica leakage monitoring.

Final Answer:
Strong-base anion exchange