A report by Dr. Karin Thelen and Dipl.-Chem. Wolfgang Schoentag

Up until the early 1990s, Munich’s district heating networks were chemically conditioned with hydrazine and trisodium phosphate. When, in December 1988, DIN 1988 Part 4 banned the use of hydrazine for the direct heating of drinking water, the water in the Munich district heating network was colored with pyranine as a precaution in order to be able to detect any leakage from the heat exchanger to the drinking water. In search of an alternative, Stadtwerke München came across polyamines, a mixture of film-forming amines with alkalizing amines. These have now been used successfully in the Munich district heating network for 20 years and lead to more stable network conditions.