Investigation of thermal effects and transient reactor profiles in a plasma-sorbent system for simultaneous CO2 capture and conversion

CO 2 capture and utilisation (CCU) is a promising solution to mitigate greenhouse gas emissions and has received much attention recently. Usually, CO 2 is captured and utilised in two separate processes. In this work, we focus on integrating both processes in one single unit using a non-thermal plasma reactor packed with zeolite 5 A as the CO 2 sorbent. CO 2 adsorbed by the sorbent can be desorbed and simultaneously activated by applying a plasma over the sorbent bed. In such case, the plasma-sorbent system demonstrated a transient behaviour including the variation of CO 2 concentration, plasma power and reactor temperature. This work aims to understand such behaviour better and to optimise the process by selecting a suitable desorption duration. To study the time-resolved radial temperature profiles and to highlight the effect of in situ CO 2 conversion on CO 2 desorption rate, a 2D phenomenological reactor model was developed. This model predicts heating and desorption behaviour in two different cases: 1) heating from a central heating rod, and 2) heating from the bulk of the sorbent bed with a fixed conversion that is provided as a modelling input. The first case represents temperature swing adsorption (TSA), while the latter represents the heating effect in the case of plasma-assisted desorption. Experiments were also conducted to verify the model and investigate the desorption and conversion of CO 2 . The results showed that in situ CO 2 conversion during plasma-assisted desorption increases the desorption rate compared to TSA. Thermal desorption plays an important role in the plasma-induced desorption of CO 2 , and a more uniform radial temperature profile can be achieved compared to using a central heating rod. In addition, it was observed that CO 2 conversion stagnates after 4 minutes of plasma exposure. Longer exposure times did not lead to higher CO 2 conversions because the reverse reaction of O 2 and CO to CO 2 competed with the forward reaction. Although plasma-induced desorption has a much higher energy consumption compared to TSA, 14.5 % CO 2 conversion can be achieved during the desorption process, and shorter cycle times can be achieved because of the faster desorption rate. • In-situ CO 2 conversion increases the CO 2 desorption rate. • In plasma-assisted desorption zeolite 5 A desorbs CO 2 via a thermal pathway. • Plasma-assisted desorption can have lower temperature gradients compared to TSA. • The CO 2 conversion is limited at high CO 2 concentrations. • The ratio of sorbent over reactor mass must increase for an efficient operation.