Theses & Dissertations

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https://hdl.handle.net/20.500.14170/194

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Browsing Theses & Dissertations by Subject "Absorption"
  • Publication
    Carbon Dioxide absorption from Biogas using Piperazine-Promoted 2-Amino-2-Methyl-1-Propanol blended solution in packed column
    ( 2021)
    Viga Rajiman
    Biogas is a renewable energy source that is mainly composed of methane (CH4) (40%–75%) and carbon dioxide (CO₂) (20%–60%). Monoethanolamine (MEA) is an established absorbent in CO₂ absorption, yet its removal performances are challenged by its limitations. In order to overcome the limitations of individual amine absorbents, a potential blended amine solution; piperazine-promoted 2-amino-2-methyl-1-propanol (PZ/AMP) has a remarkable performance in capturing CO₂ at low CO₂ partial pressure conditions (< 20 kPa), and suited for the conditions in flue gas treatment. However, for biogas upgrading applications, higher CO₂ partial pressure (> 20 kPa) should be considered due to the presence of high CO₂ concentration in the feed gas. Since the mass transfer behaviour at higher CO₂ compositions in the feed gas can affect the process performance in a packed column, it is crucial to explore the effectiveness of the potential absorbent in removing CO₂ at higher than 20 kPa of CO₂ partial pressure. Therefore, in this research, CO₂ absorption from simulated biogas was investigated using different blends of PZ/AMP solution in an absorption system at 200 kPa. CO₂ absorption performance was evaluated at different ratios of PZ to AMP solution (0/30, 3/27, 5/25, 7/23, and 9/21 wt.%/wt.%) and was benchmarked with 30 wt.% of MEA solution. The effects of process parameters CO₂ absorption into PZ/AMP blended solution were also examined and thoroughly discussed, in terms of process performance, including CO₂ partial pressure (20–110 kPa), gas flow rate (22.10–35.36 kmol/m2∙h), liquid flow rate (3.25–5.42 m3/m2∙h), chemical concentration (10–40 wt.%), and inlet liquid temperature (30 ± 2 to 45 ± 2 °C). The data were presented as CO₂ removal profiles along the column and evaluated in terms of CO₂ removal efficiency (%) and average overall volumetric mass transfer coefficient in the gas phase (KGav !!!!!!). Increased PZ concentration in AMP solution was found to have significantly increased CO₂ absorption and mass transfer performance, while the 7 wt.% of PZ/23 wt.% of AMP blend has a similar removal performance as 30 wt.% of MEA solution. Increased CO₂ partial pressure and gas flow rate in the process have been shown to decrease CO₂ removal performance from 100% to 58% and 72%, respectively. Meanwhile, the KGav !!!!!! values were decreased from 0.63 to 0.039 kmol/m3∙h∙kPa (CO₂ partial pressure) and 0.317 to 0.092 kmol/m3∙h∙kPa (gas flow rate). In contrast, increased liquid flow rate and chemical concentration exhibited positive impacts on CO₂ removal performance. The results showed that increasing liquid flow rate and chemical concentration have increased the CO₂ removal efficiency from 70% and 33%, respectively, to a complete removal. Similarly, the KGav !!!!!! values were increased from 0.066 to 0.389 kmol/m3∙h∙kPa (liquid flow rate) and 0.024 to 0.276 kmol/m3∙h∙kPa (chemical concentration). Meanwhile, the optimum inlet liquid temperature was observed at 35 ± 2 °C in this study, with a 100% CO₂ removal efficiency and 0.36 kmol/m3∙h∙kPa of KGav !!!!!! value. Overall, the PZ/AMP blended solution showed great potential to be commercialised in industrial biogas production.