Activated Carbon & Biomethane: Filtering Biogas with CarbonClean®
What is activated carbon?
Activated carbon, also known as activated charcoal, is made from carbon and is known for its intense black color. You might have seen black tooth paste, and even black ice cream made with activated charcoal. The main characteristic of carbon is the strong attraction to particles from air and water. This special property is also called adsorption: the molecules attach themselves to the carbon. Not to be confused with absorption, at which the molecules penetrate into the material. To increase the surface area, the carbon must be reduced in size. This is also called activating. Hence the name: activated carbon. A microscopic image gives a better picture of the structure of active carbon, that compares the best with the structure of a sponge. The small spaces and holes contribute to the relatively large surface area of activated carbon.
Characteristic activated carbon
Due to its high adsorbing characteristic, activated carbon is extremely suitable for removing contaminants from biogas.
Bright Renewables uses a specially impregnated activated carbon type in the form of pellets for the removal of toxic H2S.
For the removal of volatile organic compounds, Bright Renewables uses carbon in the form of so-called granules.
How does Bright Renewables use activated carbon?
During the upgrading process from biogas to biomethane, filtering is one of the first steps. Due to the high adsorbing characteristic of activated charcoal, this step is also applied in Bright’s PurePac biogas upgrading installations. This is done in the three Bright Renewables CarbonClean® filters. Two of these vessels contain active carbon especially for the removal of toxic hydrogen sulfide (H2S). The other vessel contains activated carbon for removing other contaminants such as volatile organic compounds (VOC).
How do the different Bright Renewables' Carbon Clean® filters work?
Bright Renewables uses a specially impregnated activated carbon type in the form of pellets for the removal of toxic H2S. This special carbon has the strong property that it takes longer for the carbon to be saturated with H2S. The carbon has an adsorption capacity of 60% of its own weight. For regular carbon this is around 40%. As a result, it takes longer for the special carbon to be refilled so it is more economical to use. Since the H2S in biogas can be present in relatively large quantities (up to 1,000 ppm), the activated carbon must be replaced from time to time when it is saturated. The PurePacs systems from Bright contain two activated H2S carbon filters that work independently of each other. At the time of changing the saturated carbon, the installation can still work and produce biomethane.
For the removal of volatile organic compounds, Bright Renewables uses carbon in the form of so-called granules. This type of carbon is very suitable for removing VOC from the biogas. Since there is less VOC in the biogas than H2S, only one filter is needed for this.
Bright Renewables PurePac systems
PurePac Compact
PurePac Medium
PurePac Grand
