Neutralizing Amines

Neutralizing amines control corrosion in distillation overhead systems. They vaporize with the tower overheads, condense with the first water droplets, and neutralize acids such as hydrogen chloride (HCl), keeping condensate pH in a safe range and protecting condensers, exchangers, and accumulators.

Neutralizing amines chemically neutralize condensing acids and buffer the condensate pH, tackling the cause of low-pH attack. Filming amines instead lay down an adsorbed barrier film on the metal surface. Many overhead programs use both together; the right combination depends on chloride loading, water volumes, and system layout.

Calcium and magnesium chloride salts remaining in desalted crude hydrolyze at furnace temperatures to hydrogen chloride. HCl travels with the overhead vapor and dissolves into the first condensing water, forming locally concentrated hydrochloric acid that rapidly attacks carbon steel at the initial condensation point.

Dosing is trimmed against routine overhead water analysis — pH, chloride, and iron counts — with continuous injection adjusted to hold the target pH window. Rising iron or falling pH signals under-dosing or a chloride excursion; persistent salt problems point to reviewing wash-water practice and injection-point design.