Water and Steam Purity Target Values for Polyamine (Helamin) Water Chemistry at Combined Cycle Power Plants

Abstract

Complex chemicals that include filming amines have been widely used for water chemistry control at combined cycle power plants during the last 10-20 years. Use of these complex chemicals has resulted in: lower rates of material corrosion and deposition on heat transfer surfaces, removal of deposits from heat exchange surfaces and turbine blades, and simplification of layup procedure of heat recovery steam generators. The chemicals under trademark Helamin are the first polyamine-based complex chemicals that have been in use at Russian combined cycle power plants since 2004. Water chemistry with the use of these chemicals is called Helamin treatment. If other types of polyamines (e.g., Epuramin, Vtiamin etc.) are used for chemistry control, then the water chemistry is called polyamine treatment. In spite of the wide experience with polyamine treatment at combined cycle power plants, guidelines on water and steam purity that available for this treatment need significant revision. Domestic guidelines are mostly associated with certain types of complex chemicals and sometimes are out-of-date, requiring amendment and revision. The first international technical guidance on the use of complex chemicals with filming amines for water chemistry control at drum-type and combined cycle power plants (Application of Film Forming Substances in Fossil, Combined Cycle, and Biomass Power Plants) was issued in 2016 (re-issued in 2019) by International Association for the Properties of Water and Steam (IAPWS). However, water/steam purity target values used in this guidance are based on reducing and oxidizing all- volatile treatments (AVT(R) and AVT(O) respectively), which do not account for all features associated with filming amine treatment.

In this work, development of water/steam target values for treatment with complex chemicals accounts for norms used in previously issued complex chemical treatment guidelines as well as in existing AVT(R) and AVT(O) guidelines. These target values take into account process flow diagrams of power-generating units and presence/absence of copper-based alloys in condensate/feed water train. Comparison of chemical monitoring results and target values from plant operational guidelines with those presented in this work has been performed for three different combined cycle power-generating units. The results of the work indicate that the suggested water/steam purity target values, on the whole, are either in line with, or stricter than, the respective values from plant operational guidelines of the surveyed units. Average water/steam chemistry values measured during more than one year of base-load operation of three combined cycle power plants with different process flow diagrams and materials, are within suggested target values.