Measures against foam layers
Forming of foam and swimming layers can be a sign of process imbalance and their
formation is often caused by the types of feedstock supplied. The presence of foam and
swimming layers on the surface of biomass, inside the digest, can cause clogging of gas
lines. To prevent this, gas lines should be installed as high as possible inside the digester.
Foam traps can prevent penetration of foam in the feedstock pipes and to the post digester or
storage basins. A foam sensor can be installed in the gas area of the digester, to start
automatically spraying foam retardant inside the digester, if there is too much foam on the
surface of the substrate. The foam retardants must be used only in emergency situations, as
they usually consist of silicate binders which can damage the CHP plant.