Long term and performance testing of NaMg double salts for H2/CO2 separation

Abstract

This work investigates the synthesis and performance of double salts for H2/CO2 separation. A series of NaMg double salts were prepared based on xMg(NO3)2: yNa2CO3: zH2O and characterised. The best sorbents reached CO2 uptake of 17.9 wt% at 0.62 MPa and 375 °C. The NaMg double salts preferentially sorbed CO2 as determined by breakthrough tests. The NaMg double salts were packed in a sorbent bed and tested for H2/CO2 separation at the back end of a water gas shift reactor. The space velocity had the largest impact on the performance of the sorbent bed, as increasing the space velocity from 2.16 × 10−3 to 9.51 × 10−3 s−1 sped up the breakthrough time by 84%. Increasing the feed gas pressure from 0.3 to 0.6 MPa reduced the breakthrough time by ∼45%. The NaMg double salt sorbents were exposed for over 1000 h of continuous temperature including 28 cycles of sorption and desorption, and proved to be stable during changes of operating conditions such as flow rates and pressures.