Calcium Looping Process for Clean Coal Conversion: Design and Operation of the Subpilot-Scale Carbonator

The calcium looping process (CLP), which is being developed at The Ohio State University (OSU), is a clean coal technology for the production of hydrogen (H2) and electricity from coal-derived syngas. It integrates the water–gas shift (WGS) reaction with in situ removal of carbon dioxide (CO2) and other contaminants like sulfides and halides, thus resulting in the production of high-purity H2. The in situ removal of CO2 drives the equilibrium-limited WGS reaction forward. The CLP has the potential to reduce the overall footprint of a coal-to-H2 process because of the integration of several unit operations in a single-stage reactor. The high-temperature operation and the different exothermic reactions involved provide various sources of heat, which, when integrated appropriately, result in a process with low energy penalty. Prior work conducted in a fixed-bed reactor has shown that high carbon monoxide (CO) conversions and high H2 purities can be obtained, depending on the operating pressures. On the basis of the encouraging results obtained from the fixed-bed reactor, a subpilot-scale fluidized-bed reactor (carbonator) has been designed and constructed at OSU. In this work, the design of this reactor has been detailed and some operational results have been provided.