A pressurized Internally Circulating Reactor (ICR) for streamlining development of chemical looping technology

-    Goal of the Project:
The primary objective of the project will be to demonstrate the technical and economic feasibility of the pressurized ICR for accelerated development of chemical looping technology relative to the conventional approach. This objective is divided into two subsections:
•    Experimental demonstration of the technical feasibility of achieving autothermal operation in the pressurized ICR applied to several chemical looping technologies
•    Techno-economic evaluation of the ICR concept and comparison against competing processes
A number of secondary objectives will also be met en route to the primary project goals:
•    Upgrading Norwegian laboratory facilities for the purpose of pressurized reactor concept demonstration and model validation
•    Upgrading Norwegian expertise in filtered flow modelling and solids-specific techno-economic evaluation
•    Strengthening the international research collaboration between Norway, Germany, Austria and the United States

-    Technical content:
This project will demonstrate the technical and economic feasibility of a pressurized Internally Circulating Reactor (ICR) for energy conversion with integrated CO₂ capture. The ICR concept is based on the principle of chemical looping and aims to significantly reduce the complexities surrounding solids circulation under pressurized conditions currently hampering the development of chemical looping systems. An Internally Circulating Reactor operates by circulating an oxygen carrier material between two reactor sections joined by two specially designed ports. Both reactor sections are operated as dense fluidized beds (bubbling or turbulent) and solids circulation is achieved by fluidizing the sections at different velocities. A small amount of gas leakage will occur through the ports, but simulation and experimental studies have confirmed that high CO₂ separation efficiencies can still be achieved.
The ICR concept has numerous advantages over conventional chemical looping. No external solids circulation is necessary, large solids recirculation rates can be achieved, instantaneous pressure differences between reactor sections can be better controlled, solids entrainment problems are reduced, and lower reactivities associated with cheap natural ore can be accommodated. These advantages will be experimentally demonstrated during the project for four different chemical looping technologies. In addition, the project will incorporate advanced modelling methodologies from partners in the United States and Germany. Princeton University will assist in the application of filtered multiphase flow models developed within the DOE-sponsored Carbon Capture Simulation Initiative for reactor sizing in the economic evaluation. Hamburg University of Technology will contribute to the techno-economic evaluation of the ICR concept based on established
-    Technical advantages:
The main advantage of the ICR concept is the significant simplification in comparison to conventional chemical looping systems. Replacement of the cyclones and loop seals typically used in the solids transport lines connecting the air and fuel reactors by two/three simple ports will reduce capital costs, reduce heat and pressure losses, simplify process control and accelerate process scale-up, especially for pressurized systems. The integrated design based on bubbling/turbulent beds will also reduce undesired particle attrition and elutriation while keeping a relatively small overall system footprint (the fast section freeboard can expand over the slow section).
More importantly, however, the simplicity of the design and operation of an ICR has the potential to significantly reduce the time and monetary costs of developing chemical looping technology to the stage of commercial readiness. The pressurized ICR will not only simplify standard process scale-up, but pressurized bubbling fluidized beds also give the opportunity for modular scale-up of a demonstrated prototype. Given the CO₂ abatement guidelines provided by climate science and the limited government support for CCS demonstration projects under current adverse economic conditions, this is a very important advantage.
Finally, the ICR concept is ideally suited for design and optimization using reactive multiphase flow modelling. When modelling fluidized bed reactors, bubbling and turbulent fluidization is typically much easier to model accurately than riser flows. It is also easy to include both the air and fuel reactor sections of the ICR in a single simulation whereas this is much more challenging for a standard CLC configuration because of the challenges involved in modelling the widely differing flow regimes in the two reactors, the loop seals and the cyclones. Reliable reactive multiphase flow modelling of large scale units can lead to larger and cheaper scale-up steps, thereby further accelerating the commercialization process.
-    R&D challenges:
•    Unexpectedly large gas leakages occur under high pressure operation due to unbalanced pressure between the two reactor sections. This can be caused for example due to the slow response or unstable operation of the back pressure valves.
•    The troubleshooting period before getting the hot reactor into normal and productive operation is longer than expected.
•    Challenges with maintaining autothermal operation due to heat losses or incomplete reaction.

-    Results to date:
During the first nine months of the project, the detailed design of the pressurized ICR has been completed and parts have been ordered for construction. The reactor was designed for a maximum operating temperature and pressure of 1000 °C and 10 bar respectively. Existing computational fluid dynamic (CFD) models were used to aid in the reactor design by simulating the circulation of the oxygen carrier material between the two reactor sections.
Reactor construction will start towards the end of 2016 and cold testing will be carried out during the first quarter of 2017. Reactive CLC experiments at atmospheric pressure will be carried out during the middle of 2017, followed by the first pressurized reactive tests towards the end of 2017.
The PhD position for carrying out the reactor experiments has been advertised and a large number of applications has been received. Potential candidates are currently being interviewed and the selected candidate will start his/her work at the NTNU during January 2017.