In-depth impact evaluation of binders on the mechanical properties and CO2 capture performance of CaO-based particles

Abstract

The industrial applications of CaO-based adsorbents for CO2 capture are limited by the challenges of serious sintering in a realistic regeneration condition and elutriation in the fluidized-bed reactors. Although the granulation of CaO-based adsorbents has been extensively investigated, the key indexes such as mechanical strength, adsorption performance, and cyclic stability were investigated independently rather than united for practical applications. Here, we systematically investigated the impacts of binders on the mechanical properties and CO2 capture performance of CaO-based particles granulated using the extrusion method. Among different commercial binders (cement, kaolin, and bentonite), only cement yielded calcined CaO-based particles with the required mechanical strength. At the optimal cement proportion (10%) and particle diameter (3 mm), the “CaO+Cement” particle achieved a compressive strength of ≥20 N and an attrition rate of ≤5%. After granulating, the “CaO+Cement” particle retained a favorable CO2 uptake of 458 mg/g within 10 min, and also exhibited excellent cyclic performance in a realistic regeneration condition (calcination at 920 °C in a CO2 atmosphere), with a decay rate of 0.9% per cycle during long-term cycles. After 50 cycles, the cumulative CO2 uptake for “CaO+Cement” particle was 9.44 g/g, representing a marked increase of 42.9% compared with that of the pure CaO particle. Owing to those multiple advantages of excellent mechanical strength, CO2 adsorption performance, cyclic stability and economic cost, the “CaO+Cement” particle (with a cement proportion of 10% and a diameter of 3 mm) appears to be a promising material for CO2 capture from industrial flue gas at large-scale.