Effect of K2CO3·1.5H2O on the regeneration energy consumption of potassium-based sorbents for CO2 capture

•The formation condition of K2CO3·1.5H2O was obtained through thermodynamic equilibrium calculation.•High-pressure fixed bed experiment was carried out to verify the thermodynamic calculation.•The system energy consumption for K2CO3 as CO2 sorbent was analyzed.•One novel process was put forward to reduce the energy consumption.

A high-pressure fixed bed reactor was used to study the formation condition of K2CO3·1.5H2O and the significance of K2CO3·1.5H2O in reducing the regeneration energy required for potassium-based sorbents. The reaction heat of K2CO3 converted into KHCO3 in the following reaction: K2CO3(s) + CO2(g) + H2O(g) ↔ 2KHCO3(s), is approximately 143 kJ mol−1-CO2. This value is much larger than that of amine with CO2 (∼60 kJ mol−1-CO2). K2CO3·1.5H2O can absorb CO2 with the reaction heat of 42 kJ mol−1-CO2 in the following reaction: K2CO3·1.5H2O(s) + CO2(g) ↔ 2KHCO3(s) + 0.5H2O(g). This result indicates that a large amount of heat (99 kJ mol−1-CO2) is released during the formation of K2CO3·1.5H2O in the following reaction: K2CO3(s) + 1.5H2O (g) ↔ K2CO3·1.5H2O(s). The energy required for potassium-based sorbents can be potentially reduced when KHCO3 is converted into K2CO3·1.5H2O in the regeneration process or when the heat released during the formation of K2CO3·1.5H2O can be reused. Consequently, this work is focused on the investigation of the formation condition of K2CO3·1.5H2O and the potential effect of K2CO3·1.5H2O on the reduction of the energy required for potassium-based sorbents.