Liquid-vapor distribution of amines and acid ionization constants of their ammonium salts in aqueous systems at high temperature

Ammonia and volatile organic amines are used to treat the water in steam generating systems to afford protection of the steam- and feedwater circuits from corrosion by acidic condensate. The base strength and the volatility of the reagent used are two important parameters that have bearing on its ability to inhibit corrosion; they determine the pH of the solution produced from condensing steam. The distribution of thirteen amines between water and steam in the temperature range 150 to 325°C was studied. The amines were chosen on the basis of their known room-temperature base strength. The acid ionization constant of the ammonium salts of seven of these amines was determined by conductivity measurement in the temperature range 25 to 275°C. Amines with high room-temperature base strength and distribution coefficient in the optimum range were chosen for the high-temperature base strength determination. The results of these studies were used to estimate the effectiveness of these amines in raising the pH of the condensate from steam containing carbon dioxide and acetic acid, to provide the basis for further studies on the corrosion inhibition properties of the amines.