The demineralizer process uses resin regeneration with sulfuric acid in the first vessel and caustic soda in the second vessel to produce a product that removes minerals from water. Which term describes this equipment?

• A. Condenser
• B. Water Softener
• C. Boiler
• D. Demineralizer

Answer: (D)

This question tests how an ion-exchange system removes minerals from water to produce very pure feedwater. In a demineralizer, water is treated by resin beds that exchange mineral ions for hydrogen and hydroxide ions. The cation resin is regenerated with a strong acid (sulfuric acid) to restore its H+ form, while the anion resin is regenerated with a strong base (caustic soda) to restore its OH− form. When the two resins work together, the exchanged ions leave as minerals removed from the water, and the H+ and OH− released by regeneration combine to form fresh pure water. This capability to remove virtually all dissolved minerals distinguishes a demineralizer from a simple water softener or other equipment, and aligns with its role in producing mineral-free boiler feedwater.