Activation of ilmenite as an oxygen carrier for solid-fueled chemical looping combustion

Abstract

Ilmenite ore is one of the promising oxygen carriers (OCs) used for coal-fueled Chemical-Looping Combustion (CLC) for electricity generation and CO 2 capture. However, the low reactivity and natural activation of ilmenite OC are two major constrains impeding its application. This effort is to improve ilmenite OC's performance by introducing a small amount of foreign elements, including alkali or alkaline earth metals (K and Ca) and transition metals (Cu, Mn, and Ni). Coating and re-granulation methods were used to prepare OCs where ilmenite ore was the primary constituent. The reactivity, transport capacity, and selectivity of these ilmenite-based OCs with wet syngas, as well as their performances in coal char-fueled CLC were investigated using a TGA, fixed-and fluidized-bed reactors. The addition of K-element significantly improved the OC's reactivity with wet syngas and coal char. The strong catalytic function for WGSR from K-added OCs was found to play a vital role. Cu-coating hindered effectively Fe-element segregation on the surface of ilmenite OC during cyclic reaction, and the OC structural integrity was well maintained. Ca-, Ni-and Mn-added ilmenite OCs did not show promising prospects. The gasification rate and combustion efficiency could be respectively correlated to the reactivity and selectivity of different OCs except for the K-added samples.

Activation Mechanism of Fe2O3-Al2O3 Oxygen Carrier in Chemical Looping Combustion

“…Similar activation phenomena also existed for natural ilmenite during the CLC process, − and the redox activity of ilmenite was increased during the initial cycles. The results indicated that the activation phenomenon was caused by the improvement of the microstructure for ilmenite in redox reactions.…”

Investigation of the Oxygen Supply and Distribution in a Bubbling Fluidized Bed by Using Natural Ilmenite for Oxygen Carrier Aided Combustion

“…Moreover, Fe accumulated at the surface accompanied by increased porosity. This process is comprehensively discussed in the literature, especially in the context of ilmenite application in CLC processes. ,, However, as during CLC processes the conversion of the OC normally is higher, the activation during OCAC processes can take longer . Because of this, the outer shell observed is comparably thin.…”

Use of a Low-Cost Colombian Manganese Mineral as a Solid Oxygen Carrier in Chemical Looping Combustion Technology

“…To prevent the accumulation of ash in the system, it is necessary to evacuate them, but this implies significant losses of the OC . Therefore, the use of low-cost materials, especially solid wastes and natural materials, has been a subject of study by different authors seeking more feasible alternatives in the combustion of solid fuels. − …”