The state of the technology of treatment of the aqueous working medium at Russian thermal power stations

Thermal stability of film forming amines‐based corrosion inhibitors in high temperature power plant water solutions

“…The compounds produced as a result of ODA thermolysis are ammonia, 15,28,33,35,78–81 hydrogen (H 2 ), 15,28,33,35,79,81 carbon monoxide (CO), 33,79,81 methane (CH 4 ), 15,28,33,81 and carbon dioxide 15,28 . Dioctadecylamine and trioctadecylamine are formed by releasing ammonia from ODA molecules and the reactions between them 26,35,79,86 . Harmful low molecular organic acids were neither reported in the mentioned papers nor in the work later published by Cao et al 80 who analyzed samples obtained between 350°C and 560°C.…”

“…The chosen concentrations at the temperature of 160°C were within the range of 7.5–43 mg/kg to ensure that a substantial or complete amount of ODA could be dissolved. The authors obviously took into account the temperature dependence of ODA solubility, which exhibits an increasing trend 26 . The concentration of 20 mg/kg represents the value at which the authors observed abrupt alterations in the character of the coefficient of ODA decomposition.…”

“…Regarding the quantities of breakdown products, it was calculated that 5 mg of completely decomposed ODA produced roughly 0.3 mg of ammonia 26,87 . Furthermore, at 343°C and 15.2 MPa, the total amount of hydrogen, carbon monoxide, and methane equaled 1% of the initial ODA amount 33,81 .…”

“…As mentioned in Section 5.5, the decomposition of primary amines at high temperatures is known to result in the formation of secondary and tertiary amines, while releasing ammonia. On the basis of the literature data, 28,78,79,86,88 the decomposition of ODA in steam generators in the presence of metal catalysts 26 leads to the formation of dioctadecylamine and ammonia, as follows: …”

“…Like all compounds belonging to amines, FFA represent the products of the replacement of one, two, or three hydrogen atoms of ammonia (NH 3 ) with hydrocarbon substituent, R (such as alkyl, alkenyl, or the aryl group), and contain a basic nitrogen atom with a lone pair. Depending on the number of hydrogen atoms that are replaced by substituents, they can contain the primary, secondary, and tertiary functional amino group, which is a fast‐reacting, active, and polar part determining the characteristics of the compound, while the substituent, R, is a slow‐reacting, inactive, and non‐polar part 26 of the molecule.…”