Chemical Looping Combustion

This technology involves the use of a metal oxide as an oxygen carrier which transfers oxygen from the combustion air to the fuel under atmospheric or pressurized conditions. In this case, the basic competitive advantage is the omission of an air separation process and the direct separation of CO₂.

Chalmer’s 10kWth CLC prototype (courtesy by Chalmers University)

The CLC principle is based on two separate reactions :

• reduction of metal oxide by the use of fuel :

  (2n+m)Me_xO_y + C_nH_2m → (2n+m) Me_xO_y-1 + mH₂O + CO₂

• air oxidation of the resulting metal by the use of the

  Me_xO_y-1 + ½ O₂ → Me_xO_y

Two important design criteria are related to the properties of the oxygen carrier:

• The amount of oxygen carrier necessary in the two reactors
• The rate of circulation (flux) of the oxygen carrier between the air and fuel reactor which is inversely proportional to the mass of oxygen that is released/captured by the oxygen carrier during a cycle

Within the ENCAP SP4 subproject the research efforts are focused on stable reactive materials and novel reactor concepts. The goal is to develop oxygen carrier materials with high reduction and oxidation rate, durability in chemical, structural and mechanical properties for high number of cycles, at acceptable cost. For example, Mn, Cu, Ni, Fe based oxygen carriers alone and with support materials e.g.TiO₂, Al₂O₂, SiO₂, are tested in experimental facilities. Research on CLC reactor is directed towards the following concepts:

• A CFB reactor with powder as oxygen carrier
• A Rotating Reactor with coated monoliths as bed material and Membrane-Assisted Reactor with extruded pellets