The presentation lead by Patrice Font, leader of work package 2 and 5 of the CHEERS project and researcher at IFPEN, as well as Professor Zhenshan Li, work package 6 person in charge from Tsinghua University, covered the design considerations under both the European and Chinese partners. Work on chemical looping combustion was investigated by both Chinese and European partners resulting in two different and innovative configurations to evaluate the technology. Testing both these configurations would allow for two different approaches to achieving CLC to be tested.
The common alignment across the different configurations is the use of solid feedstock. The European configuration focuses on petcoke while the Chinese configuration looks at lignite. The difference between the two rather being in terms of the application of CLC technology. The European configuration looks to be applied in a refinery; the Chinese configuration on the other hand, looks at emissions reduction in power generation. The functioning of the plant is still based on solid circulation and hence both configurations are evaluated within the same demo unit despite having the circulation flow slightly altered.
The presentation went through the different valves that govern the core functioning, which allow for solid circulation through the different parts of the unit. Such solid circulation requires pneumatic valves as compared to conventional mechanical valves. There are three main L-valves which control: the oxygen carrier flowrate to the fuel reactor, oxygen carrier recycling around the air reactor and the movement of oxygen carrier from carbon stripper to the air reactor. The European design considers an integrated carbon stripper alongside the fuel reactor whereas the Chinese design realises the two as separate units. The fuel reactor uses a fluidised bed design allowing for longer conversion time for the solid feed to convert to gaseous products.
On the road to a 4 MWth demo unit, a continuous pilot model on the kW scale and a MW scale mockup was developed by IFPEN. Through such process developments, many patents were filed along the way such as the methodology of separation of oxygen carrier and unburnt feedstock. A 1.5 MW cold flow model was developed at DBC which aimed to study crucial parameters such as fuel reactors hydrodynamics, solid circulation between air and fuel reactor, transport of oxygen carrier in air reactor and carbon stripper efficiency. This was crucial in demonstrating the stability of the design in a wide range of operating conditions for both configurations.
The designs proposed by the partners were tested and validated to be realized in the demo unit. The path to the two innovative approaches resulted in a variety of outputs, patents being one such example. For more information on the design of the CLC units and the configurations, do not hesitate to reach out.