Behavior of Dolomites under Fluidized Bed Sorption-Enhanced Gasification Conditions

This work investigates the behavior of dolomites during sorption-enhanced gasification in dual interconnected fluidized bed systems for the production of H₂-rich syngas. Two sorbents, one of Italian origin, the other of Polish origin, with CaO content ranging from 60 to 63 wt %, and MgO content around 32-33 wt %, were subjected to calcination/carbonation cycles (10 cycles for each test) in a lab-scale apparatus. In particular, the temperature of the fluidized bed carbonation stage was varied between 600 and 700 °C, both in the absence and in the presence of water vapor. With an eye to the role of the operating conditions, for each material, the following aspects were investigated: CO₂ capture capacity, fragmentation tendency, and elutriation phenomena upon surface wear. The discussion was then extended by recalling previous results obtained on a set of 6 limestones (rich in Ca) under the same operating conditions through a comparison analysis between the behavior of dolomites versus limestones. In particular, it was observed that steam is capable of positively influencing the dolomite behavior in terms of CO₂ capture; the elutriation rate is markedly more relevant upon calcination than carbonation, negatively affected by the presence of steam, and less extensive for sorbents showing higher CO₂ capture. Normalizing the CO₂ capture on the CaO content, the performance of dolomites is comparable to that of limestones, although dolomites have a more fragile structure that increases their tendency to undergo fluidized bed fragmentation.