In today's water treatment using the heat recovery steam generator (HRSG) of combined
cycle plants, ammonia and hydrazine are used in the feedwater system and sodium phosphate is
used in the boiler system. In recent years, however, corrosion due to phosphate has occurred at
some plants, and efforts to realize hydrazine-free water treatment will be needed in the future. To
cope with these issues, conversion to high-AVT water treatment is effective, and its actual
performance has been well-received and was adopted as the JIS standards revision proposal.
Mitsubishi Hitachi Power Systems, Ltd. (MHPS) developed the new technologies for conversion to
high-AVT water treatment, specifically neutral room-temperature chemical cleaning and an
electrolytic denitrification system for high-pH waste water, which will be introduced below.
