Research is active on the technology, titled Apparatus and Method for Solid Fuel Chemical Looping Combustion. This technology is available for licensing and/or further collaborative research from the U.S. Department of Energy’s National Energy Technology Laboratory.
The removal of CO2 from power plants is challenging because existing methods to separate CO2 from the gas mixture requires a significant fraction of the power plant output. Chemical-looping combustion (CLC) is a novel technology that utilizes a metal oxide oxygen carrier to transport oxygen to the fuel thereby avoiding direct contact between fuel and air. The use of CLC has the advantages of reducing the energy penalty while producing sequestration-ready CO2.
In order to obtain fast reaction rates, current CLC reactor designs mix solid fuels, such as coal, with metal oxides, ensuring that the oxygen from metal oxide is quickly consumed by either the solid fuel or the synthesis gas. However, this process requires separation of residual solid fuel ash from the oxygen carrier after each reduction-oxidation cycle. Interaction of ash with metals also contributes to the deactivation of the metal oxides.
The current invention addresses these issues by using a novel reactor design concept. In the new design, the oxygen carrier and solid fuel are kept apart solving the ash separation issue; however they are kept close enough in order to improve reaction rates. The oxygen carrier is placed in a perforated reactor inside the main reactor containing the solid fuel. The oxygen released from the oxygen carrier can quickly diffuse through the perforated reactor walls and react with the fuel. In addition, volatiles from coal and products formed from coal gasification can also diffuse through the perforated reactor wall to react directly with the metal oxide. Since the solid fuel is placed very close to the oxygen carrier, the fast consumption of oxygen will increase the rate of decomposition of the oxygen carrier to produce oxygen. Fast consumption of gasification products from coal may also enhance the gasification reaction rates. The operation of the process is simpler and more cost effective since the solid separation of oxygen carrier and ash is not required.
U.S. Patent No: 9,004,911
Title: Apparatus and Method for Solid Fuel Chemical Looping Combustion
Inventors: Ranjani Siriwardane, Justin Weber
NETL Reference No: 12N-15