The effect of alternative amines on the rate of boiler tube fouling. Final report

Deposition rates were measured for magnetite and hematite particles depositing onto Alloy 600 surfaces, and for magnetite particles depositing onto surfaces prefouled with sintered porous magnetite deposits. The measurements were made in a high-temperature loop, under typical nuclear steam generator operating conditions, with pH controlled using morpholine, ethanolamine, ammonia, dimethylamine, or potassium hydroxide. The deposition rate was compared as a function of the particle type, tube surface morphology, and the reagent used for pH control. The deposition rates were measured for steam qualities ranging up to 50%. The conclusions drawn from this program are: the particle deposition rate of hematite is about an order of magnitude greater than the rate for magnetite on bare Inconel 600 surfaces; the identify of the amine used for pH control affects the deposition rate, the lowest deposition rate is obtained when dimethylamine is used for pH control; the deposition rate of magnetite increases with the increasing concentration of amine (at constant pH); under reducing conditions with no detectable oxygen and with free hydrazine, the deposition rate of hematite decreases towards the value for magnetite; the particle deposition rate can be affected by the surface morphology; the deposition rate is significantly higher on surfaces covered with porous deposits; the heat transfer mechanism and steam quality strongly affect the deposition rate, the deposition rate increases abruptly at higher steam qualities; and there is no evidence that the volatility of the amine affects the deposition behavior