Upgrading Biogas
The upgrading process for biogas involves the removal of CO2. The most widely commercialized and used upgrading technologies are those that have for a long time been employed by the natural gas industry, pressure swing adsorption (PSA), chemical solvent scrubbing (using amines), and pressurized water scrubbing.^2
Biogas Water Scrubber System Design, Greenlane Biogas ^3
(Image Credit: Hudde (2010), taken from ^3)
Amine water scrubbing is one traditional chemical solvent scrubbing method of upgrading that is applied due to its low methane slippage and its capability to provide a high purity renewable methane product.
There are many amine chemicals that dissolve into water as a solvent for biogas scrubbing such as mono-ethanol-amine (MEA), di-ethyl ethanol amine (DMEA), diethanolamine (DEA). MEA (HOC2H4NH2) was chosen for this study as previous literature has indicated it has a rapid reaction rate,low cost and low molecular weight.
The reaction between MEA and CO2 is an exothermic reaction; for each mole of CO2 absorbed in MEA solution, 72kJ of thermal energy is released.
Data
Economic and technical datas is taken from Vo & al ^1. Currently around 3.5 Mtoe of biomethane are produced worldwide and 92.3% are from upgrading biogas^4. The initial age distribution has been computed with biomethane plant lists from ^5 since most of biogas is converted into biomethane.
^1: Vo, T. T.; Wall, D. M.; Ring, D.; Rajendran, K.; Murphy, J. D. (2018). Techno-economic analysis of biogas upgrading via amine scrubber, carbon capture and ex-situ methanation. Applied Energy, 212, pp. 1191-1202.
^4:Abanades, S., Abbaspour, H., Ahmadi, A., Das, B., Ehyaei, M.A., Esmaeilion, F., Assad, M.E.H., Hajilounezhad, T., Jamali, D.H., Hmida, A. and Ozgoli, H.A., 2021. A critical review of biogas production and usage with legislations framework across the globe. International Journal of Environmental Science and Technology, pp.1-24.