Qualification testing of three advanced amines for secondary-system pH control in once-through steam generator plants

This report discusses three different advanced amines which were used for secondary system pH control at Davis Besse. The amines tested were Ethanolamine (ETA), 2-Amino,2-methyl propanol (AMP) and 3-Methoxypropylamine (MPA). All of the amines behaved as expected and predicted by industry chemistry models. The observations made during this test also compared well with laboratory testing and another field application in the case of ETA. Although the different amines affected the high temperature pH in various parts of the secondary system, the test periods were not long enough for a new equilibrium surface condition to be established. Thus, the impact of the various amines on overall iron transport in the secondary system could not be assessed. Based on a comparison between the three amines and prior operation with morpholine, ETA appeared to afford the most benefit. It was determined, however, that better results should be achievable by employing a mixture of amines. The addition of MPA, for instance, to ETA will allow for higher pH levels in the condensate system than ETA alone, while minimizing the amine concentrations. Determining the optimum chemistry control will be plant-specific and based upon the materials of construction and operation of any demineralizers