Hi everyone, I'm looking for a method to obtain max carbonation yield (95 wt.% and more) after gas-solid reaction between CO2 and dense bulk CaO. I can run the reaction up to T=800°C and PCO2=50-60 bar (inside pressurized reactor). But the reaction at 800°C, 60 bar CO2, for 24 hours is not complete (max yield is 80-85 wt.%).
Any suggestion? Add water to CaO (what concentration?), light acidic treatment of CaO (or other chemical treatments), etc...
Thanks
You can never reach to 100% conversion since at the end of the day, there would be some unaccessible reaction sites. But if you increase the surface area combined with higher pressure I think you would get pretty high conversion. You can make high porosity CaO by bubbling CO2 in dispersed Ca(OH)2 in water while P123 is added and then drying and calcining the powder. This does not provide have high mechanical resistance but provides high porosity. You need to be careful not to destroy CaO structure by applying high pressures. as you know CaO is pretty soft. You may want to try impregnate CaO in alpha-alumina. Alternative method I can think of is incremental carbonation. Carbonate some CaO and then take it out, stir or agitate and then carbonate again. Another method you can try is sheer carbonation, put in a high rpm stirrer (~10,000 rpm) and stir as you carbonate. Using steam can improve penetration of CO2 to pores as well, something around 6-7% H2O in gas phase should do the job at 1 bar. At high pressure I'm not sure since steam at some situations can increase sintering and loss of surface area.
Dear Morin, thank you very much for your suggestions. I'll try to work with low quantities of steam, because the pieces of CaO are cylindrical block and stirring or agitation could bring about the breaking. In dry condition (up to 800°C and 50bar CO2) the best conversion yield was 75% molar. If I modify the superficial porosity (about 25%) by addition of stoichiometric amount of water (by exposition in environment air, or nebulizer, etc.), do you think it could be an effective method?
In case you are dealing with CaO powder; you may consider to pelletize the powder: https://www.researchgate.net/post/which_binder_can_be_used_for_making_pellets_of_snail_shell_based_CaO_powder_and_what_will_b_ethe_method_of_it