Attrition characteristics of limestone in gas-solid fluidized beds

Abstract

Calcium looping is a potential energy-efficient post-combustion CO2 capture process that is competitive with existing commercially available technology like oxy-combustion. The attrition of CaO-based sorbents during alternating calcination/carbonation cycling in calcium looping (CaL) has the potential to escalate operation cost and contribute to environmental emisssions. Here, we measure jet mill attrition rates of four commercial limestones from Ghana and Canada and compare them with fluid catalytic cracking catalyst (FCC) and commercial vanadyl pyrophosphate (VPP) in a jet mill. We assessed the effect of orifice velocity, attrition time and calcination on particle attrition resistance. The attrition rates of the limestones increased exponentially from as low as 2.4 mg h−1, which is an acceptable rate for industrial applications, up to 38 mg h−1, which is prohibitively high as the orifice velocity increased from 180 m s−1 to 230 m s−1. The attrition rates of the FCC and VPP catalyst were somewhat higher at the low orifice velocity (5 5 mg h−1 and 8 mg h−1, respectively) but lower at the high orifice velocity (21 mg h−1−1 and 26 mg h−1, respectively). Within 3 h, Bui and Nauli limestones reached a steady attrition rate of 19 mg h−1 and 21 mg h−1, respectively whereas Oterpklu limestone reached a steady rate of 17 mg h−1 after 4 h. The calcined limestones attrition rate was twice as high as their carbonated counterpart. The limestones attrited predominantly throgh fragmentation.