Coal fired power plant water chemistry issues: Amine selection at supercritical conditions and sodium leaching from ion exchange mixed beds

Abstract

Scope and Method of Study: This study evaluated thermal degradation kinetics of neutralizing amines in steam cycle coal fired power plants operating supercritical conditions as functions of temperature and pressure. The loading amounts of amines into the reaction tube were evaluated by vapor liquid equilibrium (VLE) data from NIST database and the temperature ramp up and down inside tube was applied for evaluation of Arrhenius constants.

Findings and Conclusions: Thermal degradation of neutralizing amines over a range of supercritical temperature (300-600ºC) and pressure (1000-5000 psia) in laboratory scale and found no clear preference based on degradation rates since all neutralizing amines are not stable at high temperature. Ammonia, acetic acid and formic acid were the main thermal degradation byproducts of all selected neutralizing amines and unknown nitrogen complexes beside ammonia were expected from the nitrogen balance. Thermal degradation was dominated by temperature significantly; however pressure effect has an even weak influence on the degradation at the higher temperature. 5AP shows the slowest thermal degradation rate however it is still highly reactive. Hence, no neutralizing amine tested is acceptable for use at supercritical operating conditions.