Biogas upgrading plants   [Download this application case as PDF file]

Bacterial growth on surfaces in contact with water and other liquids (a phenomenon usually known as "biofilm") represents a major problem in most industrial applications. Indeed, this microbiological layer causes a number of issues, including corrosion, equipment failure, decreased performance and many more.

Biogas upgrading is the process that removes impurities (H₂S, siloxanes, trace compounds, etc.) and CO₂ from biogas, to obtain biomethane. Based on the significantly higher solubility of CO₂ in water compared to methane, particularly at lower temperatures, water scrubbing may be used for CH₄-CO₂ separation of biogas. The CO₂-rich water leaving the absorber is regenerated by flashing followed by recycling.

In this biogas upgrading plant (see figure below), no biocide treatment was applied to the water flowing through absorber and desorber, and some problems were observed in the packed beds. The technical staff of the plant supposed that these problems were caused by microorganisms, so an ALVIM Biofilm Sensor was installed in the desorber.

After about a month, the ALVIM Signal showed a gradual increase, indicating biofilm growth (see figure below). The technical staff of the plant decided to apply a strong cleaning and biocide treatment. As it can be seen from the graph, the treatment completely removed biofilm - indeed, ALVIM Signal dropped down to the initial level.

Then, to limit a possible re-growth, a "routine" biocide treatment was applied, on a weekly basis. As it can be seen in the figure below, the treatment strongly limited microbiological proliferation.

Thanks to ALVIM Biofilm Monitoring Technology, it was thus possible both to detect the early upset of biofilm, and to check the effectiveness of chemical treatments, greatly improving the overall efficiency of the process.