Crude glycerine is readily available, inexpensive, and non-toxic (WHO Geneva 1976). It has been found to remove most of the contaminants in raw biogas in other applications. Glycerine is an extremely polar compound and it has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. Research has shown that glycerine scrubbing solutions have a high absorbability of CO2. Limitations have been identified in selecting CO2 over N2 in tests (Chen H., Majurmdar S., Sirkar K.K. 2001); however, when cleaning raw biogas this selectivity is not a concern because both these contaminants need to be removed to produce renewable natural gas (RNG) that meets advanced transportation fuel standards and specifications. Other research has shown glycerine to dissolve H2S (CAS No. 7783-06-4), as well hold siloxances, trace contaminants in raw biogas, in suspension making them available for removal (Santamaria, F.G. 2003).
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