Utilization of Magnesium Hydroxy-Carbonate Hydrate (MHCH) Materials Formed By Precipitation of CO2 in Alkaline Aqueous Solutions | AIChE

Utilization of Magnesium Hydroxy-Carbonate Hydrate (MHCH) Materials Formed By Precipitation of CO2 in Alkaline Aqueous Solutions

Authors 

Glasser, F. P. - Presenter, University of Aberdeen
Jauffret, G., University of Aberdeen
Morrison, J., University of Aberdeen
Galvez-Martos, J. L., University of Aberdeen
Yoon, S., University of Aberdeen
Imbabi, M. S., University of Aberdeen

Carbon dioxide is a relatively stable molecule and so its recovery from mixed gaseous emissions and subsequent utilisation has proven to be quite difficult, leading to proposals that recovered CO2 should be stored rather than utilised. This paper describes a relatively simple route for the recovery of CO2 and its conversion to useful solids that can be used to make low carbon and carbon neutral construction products. The carbon dioxide from a combustion gas waste stream (e.g. from a cement plant) containing nitrogen and water vapour is selectively sorbed into an alkaline aqueous solution at ~ 25 °C and 1 atm. The carbonate and bicarbonate ions thus formed react with Mg ions (e.g. from a seawater desalination brine) under conditions such that Magnesium Hydroxy-Carbonate Hydrate (MHCH) phases precipitate; NaCl (which is quite abundant in brines from seawater) is not found to interfere significantly with the precipitation process. Nesquehonite, MgCO3·3H2O, is the preferred product obtained at ~ 25 °C and 1 atm; it typically occurs as micrometric well crystallized prismatic needles. When the powder obtained from the thermal activation of nesquehonite is mixed with water, the resulting self-cementing product can be used to form panels or blocks. The hardened materials contain ~ 30 wt% CO2 and their properties depend on the applied parameters; they are non-toxic, non-combustible and can be recycled at end of life.

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