Improved mass transfer in CLC with the aid of inert elements

Research Project, 2017 – 2019

The purpose of this project is to investigate whether the mass transfer between the gas and particle phases in a chemical-looping combustion (CLC) system can be improved by using inert elements in the bottom bed.

Chemical-looping combustion is a technology for capturing carbon dioxide during the combustion of solid, liquid, or gaseous fuels. It is currently the only carbon capture technology that does not require gas-separation equipment, giving it a significant potential cost advantage. CLC employs fluidized beds, a technology that has been successfully used in conventional combustion systems since the 1980s. In conventional fluidized-bed combustion, gas bubbles have been observed to grow very large, and for the particle size range relevant to both CLC and conventional combustion, no known upper limit exists for bubble size. Consequently, bubbles are expected to grow to diameters of several meters, considering the substantial bed heights used in CLC. Large bubbles reduce the opportunity for combustible gases to come into contact with oxygen-carrying particles, resulting in lower fuel conversion.

By introducing ceramic elements in the form of spheres (or other packing materials) into the bed, bubble size can be restricted while still allowing oxygen carriers, fuel particles, and gas to move through the void spaces formed between the spheres. The spheres are large enough not to fluidize and instead form a structure supported by the reactor bottom. This project will investigate how the concept works in practice through both cold and hot conditions.