Stanislaw Pietrzyk

Abstract:

Carbon capture and storage (CCS) by method Ca-looping is based on carbonation of CaO (CO₂ absorption), and calcination of the formed CaCO₃ (CO₂ desorption) [1].
A great challenge for this method is the decreasing sorbent reactivity after many absorption–desorption cycles [2].
Avoidance of sorbent degradation and reduction of its efficiency is possible thanks to a process known as carbon capture in molten salts (CCMS) [3]. The most promising salt mixture is eutectic CaCl₂-CaF₂ [4]. The CaO -CaCl₂-CaF₂ solutions are expected to form a suspension due to supersaturation in CaO. This can lead to an increase in viscosity, which can be a challenge in an enlarged CCMS installations where a possible approach is to transport molten salts between the absorption and desorption chambers [5]. Unfortunately, data on the viscosity of such solutions are lacking.
In order to check these possible limitations, an experimental evaluation of the viscosity of the CaCl₂-CaF₂-CaO systems was performed. Viscosity measurements were carried out with a high-temperature rotary rheometer. The results showed that increasing the CaO content and lowering the melt temperature increases the viscosity. Comparing the salt viscosity with the 30% addition of CaO and without its addition, the relative increase in viscosity at the temperatures of 750 and 950 ⁰C was over six and five times more , respectively.
The obtained viscosity results in the temperature range of 750-950⁰C and for the additive up to 30 wt.% CaO did not exceed the value of 30 cP, which proves that the cyclic transport of salt between the reactor chambers will not be hindered.