▁the ▁efficiency ▁penalty ▁refers ▁to ▁the ▁power ▁losses ▁for ▁CO 2 ▁compression , ▁air ▁separation ▁and ▁steam ▁generation . ▁It ▁is ▁estimated ▁at ▁ 6 - 8 ▁% ▁points , ▁compared ▁to ▁ 9 . 5 - 1 2 . 5 ▁% ▁from ▁post ▁comb ust ion ▁am ine ▁capture . ▁ ▁The ▁main ▁short coming ▁of ▁Ca - loop ing ▁technology ▁is ▁the ▁decre ased ▁react ivity ▁of ▁Ca O ▁through ▁multiple ▁calc ination - car bon ation ▁cycles . ▁This ▁can ▁be ▁attributed ▁to ▁s inter ing ▁and ▁the ▁permanent ▁closure ▁of ▁small ▁por es ▁during ▁carbon ation . ▁ ▁Cl os ure ▁of ▁small ▁por es ▁The ▁carbon ation ▁step ▁is ▁character ized ▁by ▁a ▁fast ▁initial ▁reaction ▁rate ▁ab rupt ly ▁followed ▁by ▁a ▁slow ▁reaction ▁rate ▁( Fig ure ▁ 2 ). ▁ ▁The ▁carrying ▁capacity ▁of ▁the ▁sor b ent ▁is ▁defined ▁as ▁the ▁number ▁of ▁mol es ▁of ▁CO 2 ▁react ed ▁in ▁the ▁period ▁of ▁fast ▁reaction ▁rate ▁with ▁respect ▁to ▁that ▁of ▁the ▁reaction ▁sto ichi ometry ▁for ▁complete ▁conversion ▁of ▁Ca O ▁to ▁Ca CO 3 . ▁As ▁seen ▁in ▁Figure ▁ 2 , ▁while ▁mass ▁after ▁calc ination ▁remains ▁constant , ▁the ▁mass ▁change ▁upon ▁carbon ation - ▁the ▁carrying ▁capacity - ▁reduces ▁with ▁a ▁large ▁number ▁of ▁cycles . ▁In ▁calc ination , ▁por ous ▁Ca O ▁( m olar ▁volume ▁= ▁) ▁is ▁formed ▁in ▁place ▁of ▁Ca CO 3 ▁( .). ▁On ▁the ▁other ▁hand , ▁in ▁carbon ation