Calcium Looping: Sorbent and Process Characterization in a 20 kWth Dual Fluidized Bed

Abstract

This paper presents an experimental investigation at a 20 kWth calcium looping (CaL) facility with a twofold focus. The first objective is on assessing the multicyclic behavior of limestone under continuous dual fluidized bed (DFB) operation. Different carbonation conditions were employed to derive a mathematical expression that is valid to compare the results from DFB and thermogravimetric analysis (TGA) with adequate accuracy. A preliminary screening of three morphologically distinct limestones was conducted by TGA including exposure to SO2 and H2O during carbonation. The second objective is to analyze the influence of multiple process variables (i.e., temperature, CO2 loading, and H2O concentration) on the performance of the 20 kWth CaL facility’s bubbling fluidized bed carbonator. Within the investigated range of operating conditions, the chosen carbonator design allowed for CO2 capture efficiencies as high as 0.99 mol/mol, yielding an apparent carbonation rate (kSφ) of 0.09 s–1. Paving the way to a more flexible usage of CaL systems, the proposed carbonator design could be integrated into the existing load-following power plants, in preference to a conventional circulating fluidized bed carbonator that is heavily penalized when forced to operate under low capacity factors.