CO_2 capture performance and mechanical properties of Ca(OH)_2-based sorbent modified with MgO and (NH_4)_2HPO_4 for Calcium Looping cycle

摘要

The present work deals with an efficient synthesis of calcium hydroxide-based materials modified with magnesium oxide and ammonium phosphate for Calcium Looping technology in Post-combustion CO2 capture. This modification produced 3 %wt of struvite, MgNH4PO4 center dot 6H(2)O, and hydroxyapatite Ca-10(PO4)(6)(OH)(2), in the material. These minerals are very hard, which contributes to increase the mechanical strength of the materials. The modified materials are four times more resistant to impact and abrasion than materials containing pure calcium hydroxide freshly prepared, and therefore, can generate less fractures and dusts. In addition, struvite and hydroxyapatite can create open pores and channels into the sorbent structure when they release water or ammonia by thermal decomposition above 200 degrees C identified by X-ray microtomography. Due to this porous structure the materials are more resistant to sintering during absorption/regeneration cycles. The new developed absorbent are harder, less brittle, generate less frictional dust, and are more resistant to high temperature sintering (400-700 degrees C) compared to pure Ca(OH)(2) based materials. The results showed that calcium hydroxide modified materials can be considered highly efficiency to CO2 absorption, with particular achievement of greater than 50%wt.