While composed primarily of methane and carbon dioxide, biogas also contains a host of contaminants including moisture, hydrogen sulfide, and Non Methane Organic Compounds (NMOCs). The most problematic NMOCs are called “siloxanes” which are a family of man-made organic compounds used in the manufacture of cosmetics, hygiene products, foods, and industrial coatings. The use of these compounds is increasing rapidly - and so is their presence in landfills and waste water.
As the material in a landfill or digester decomposes and generates biogas, the siloxane molecules enter the biogas stream as a vapor. During combustion these siloxanes undergo a phase change from a vapor to a solid silicon dioxide powder. This abrasive powder adheres to all surfaces downstream of the point of combustion, reducing heat transfer, blocking flow and increasing wear. Frequent overhaul is often required to prevent total equipment failure. The increased equipment maintenance and parts failures can significantly increases project costs while the downtime and reduced efficiency significantly decreases revenue.
The reduction of siloxane vapors prior to combustion to eliminate siloxane powder build up may be critical to the profitability of your biogas to energy project. In projects requiring the use of post combustion catalysts, siloxane vapor reduction is an absolute necessity.
Siloxane and VOC reduction is also often necessary to protect biogas upgrading processes including membranes, or water / amine washes, and to meet the necessary gas quality specifications for pipeline injection or vehicle fueling.
The High Cost of Carbon
Activated carbon may adsorb siloxanes, but it also adsorbs VOCs, moisture, hydrocarbons, hydrogen sulfide, and many of the other contaminants found in landfill and digester gas. When used for bulk siloxane or VOC reduction carbon media rarely lasts more than a few weeks, and the downtime, labor, vacuum truck, replacement media and disposal costs can cost hundreds of thousands of dollars per year!
Regeneration is the answer. Our systems use a non-carbon based media that is regenerated automatically on site, lasting 18 - 24 months or more. Our engineers invented this technology and we have the longest and most successful history of any regenerative siloxane reduction provider. Contact us today and let us show you how our technology can improve the profitability of your biogas project.