Regeneration of Activated Carbon Using Electric Potential for Upgrading Bio-Gas to Bio-Methane

The anaerobic digestion (AD) industry in the UK has experienced rapid growth in recent years over 130 operational AD plants in the UK outside the sewage treatment sector and more than 340 further projects are under development. Thus, there is an increasing demand for upgraded biogas to be used as vehicle fuel or injected to the natural gas grid. Since a typical biogas contains 1000 - 10,000 ppm hydrogen sulphide, its removal below 5ppm is required for uses beyond combined heat and power (CHP). Although a number of established methods exist for removal of hydrogen sulphide they tend to be costly. A common industry practice is to adsorb hydrogen sulphide using a granular activated carbon (GAC) bed which is subsequently disposed as hazard waste. Accordingly, this research is focused on regeneration of activated carbon using an electric potential.  Fine diameter MI construction thermocouples are used for this purpose. Thermocouples are terminated with a miniature plug. The driving force is a high capacity system that is regenerative, inexpensive and leaves no waste. Initially, 1% hydrogen sulphide / 99% nitrogen gas mixture is used as a benchmarked against an industrial activated carbon specifically used for hydrogen sulphide removal. Several Electric Conductive Activated Carbons (ECAC) will then be reported for their adsorption/ desorption potential. It is envisioned that this method can transform the production of bio-methane where early estimates have calculated that a regenerative system could save up to 50% of running costs.

Key Words:  Biogas, Electric conductive activated carbons, Thermocouples.