Benefits of biogas upgrading to biomethane by high-pressure reactive solvent scrubbing

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Abstract

Benefits of using high-pressure reactive solvent scrubbing (HPRSS) for biogas upgrading to biomethane are discussed. Main technological advantage arises from the fact that biogas must pressurized for natural gas injection or compressed fuel applications and thus high-pressure processes are particularly suitable for biogas upgrading. Ecological benefits associated with the HPRSS relate to: (i) the permanent lock-up of carbon in its highest possible oxidation state (as CO2) in soil; (ii) soil fertilization by N, K, and P elements which are enriched in digestate; and (iii) soil fertilization by N or K elements contained in the CO2 saturated solvents from the biogas scrubbing units. The effect of pressure on the HPRSS process is studied in the falling film reactor geometry by means of 2D modeling and simulation. It is emphasized that elevated pressure has significant beneficial effects on CO2 separation rates because it increases CO2 removal efficiency and decreases dimensions of scrubbing reactors. Further, two promising reactive solvents are analyzed: NH3 and KOH – both demonstrated promising CO2 separation efficiencies. Moreover, both the reactive solvents allow production of valuable fertilizer additives, i.e. ammonium bicarbonate and potassium carbonate, respectively. The bench-scale experiments of the HPRSS process realized in the counter-current packed bed reactor reveal that NH3 vaporization from the scrubber can be minimized under the conditions of low temperature, pH, and flow rate of the gas and under the conditions of high-pressure and flow rate of aqueous ammonia. © 2011 Society of Chemical Industry and John Wiley & Sons, Ltd

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