Chemical-Looping Combustion: An Emerging Carbon-Capture Technology
Authors: Carpenter Chris 
Published: January 2017

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 177561, “Chemical-Looping Combustion: An Emerging Carbon-Capture Technology,” by Frans Snijkers, Flemish Institute for Technological Research; Dazheng Jing, Chalmers University of Technology; Marijke Jacobs and Lidia Protasova, Flemish Institute for Technological Research; and Tobias Mattisson and Anders Lyngfelt, Chalmers University of Technology, prepared for the 2015 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 9–12 November. The paper has not been peer reviewed.
In chemical-looping combustion (CLC), oxygen is transferred from an air reactor to a fuel reactor by means of a solid oxygen carrier. Direct contact between air and fuel is avoided, resulting in an undiluted carbon dioxide (CO2) exhaust stream. As such, CLC has been identified recently as a high-potential carbon-capture- and-storage technology. While initial focus has been on storage projects, CO2 is increasingly considered as a valuable chemical substance for enhanced-oil-and-gas-recovery projects as well as for the production of chemicals, polymers, or building materials.
Introduction
Carbon capture, transport, use, and storage (CCTUS) form an important aspect of many national and global strategies to combat climate change. A main challenge regarding capture of CO2, especially for high volumes, is its separation from other gases.
Three primary approaches are considered technologically feasible for CO2 capture at large point sources: postcombustion capture, precombustion capture, and oxy-fuel combustion. For each approach, various technological solutions have been developed, and small- and medium-scale evaluations have proved their feasibility. However, integrated operation on a commercial scale remains to be demonstrated.
CLC
CLC is a relatively new combustion technology that can be applied as a power-production technique with inherent separation of CO2, and it is among the least costly technological options for the capture of CO2. The technological concept was first developed in the 1980s to produce CO2 and was identified only recently as a high-potential capture technology. The term chemical looping (CL) is commonly used to describe cycling processes in which oxygen is transported by a solid material, referred to as an oxygen carrier. For combustion processes, the oxygen-depleted carrier can be regenerated by reaction with air or water. Such processes are known under the general term CLC. Several variations of CL processing are possible for combustion of gaseous or solid fuels. Two specific process modifications are SR-CLC, in which steam reforming is integrated into the CLC process, and CL reforming (CLR), of which the primary products are H2 and CO.
The CLC process can be configured as two coupled fluidized-bed boilers, but packed-bed configurations, with the possibility of pressurizing, are also being considered. To transfer oxygen from the combustion air to the fuel, oxygen carriers are used. This avoids direct contact between air and fuel, and, after condensation of water, relatively pure CO2 is obtained in a separate exhaust stream from the fuel reactor. Thus, energy-consuming flue-gas separation is avoided.