Many greenhouse companies in the Netherlands are using a flue gas condenser to increase the efficiency of a CHP (Combined Heat and Power) installation. Combustion gases acidify the condensate. The acids can damage the steel in the exhaust system causing a release of heavy metals, especially nickel and chromium. This leads to problems when the water is discharged and raises questions on the re-use of the condensate as irrigation water.
The laboratory Groen Agro Control has set limits for the fruit vegetable crops. The limits for nickel, chromium and aluminium are respectively 3,000, 250 and 25 µg / L.
Measurements on a flue system
Wageningen UR Greenhouse Horticulture is looking for solutions. Several measurements were performed on companies using the CHP-condensate in the irrigation water. Measurements on a flue system with steel AISI 304 and with AISI 316 will be compared. The latter is more acid resistant. Additionaly, in a laboratory test will be performed whether an epoxy coating to steel can give sufficient protection. When the solutions mentioned are not conclusive, then the research will be focused on suitable purification techniques for the removal of heavy metals.