Here below is proposed a detailed analysis of a siloxanes removal package. The application in question, made in USA, is designed to remove siloxanes from landfill biogas. Here below main data of system:
- Biogas capacity: about 2200 Nm3/h
- Siloxanes concentration > 90ppm
- Outlet siloxanes concentration: 2-5 ppm
The system consists of two towers (each having a bed of activated carbon) in series configuration and interchangeable: once the first is saturated the first bed shall be replaced, when the coal is replacing only change it on the first one bed, which is the most stressed, and the two bed swapped in term of gas stream so that always keep the newly introduced coal as second. In this way the one that was second will became the first receiving the stream and vice versa. This configuration permits to maintain the desired specification, and use the total amount of activated carbon at the maximum capacity.
In this case, VOC has been removed upstream, the expected lifetime of the single bed is almost 1600h. In case of presence of VOC the activated carbon bed, it will be adsorbed leading to a very high impact in the lifetime of the activated carbon. In this case in fact the bed will be saturated in only 80h.