The main outcome of the ICR project is the lab-scale demonstration of a new internally circulating reactor (ICR) concept which aims to simplify the design and scale-up of chemical looping technologies. Chemical looping has great potential for clean and highly efficient energy conversion, but is facing significant scale-up challenges under pressurized conditions. Large quantities of metal oxide powder, called an oxygen carrier, needs to circulate between two reactors running different reactions. This is difficult to accomplish at large scales under pressurized conditions.
The ICR keeps the oxygen carrier inside a single reactor where it is exchanged between two reactor sections through specially designed ports. Four different chemical looping technologies are being investigated in the ICR concept under pressurized conditions: chemical looping combustion (CLC), chemical looping reforming (CLR), chemical looping air separation (CLAS) and chemical looping water splitting (CLWS).
One PhD student and one postdoc from the NTNU are working in the ICR project. The PhD student is responsible for carrying out the demonstration experiments using the reactor designed and constructed by SINTEF scientists and NTNU technicians. In parallel, the postdoc is incorporating reactor modelling inputs from SINTEF scientists to carry out the techno-economic assessment. The project is led by NTNU with Associate Professor Shahriar Amini as project manager.
The ICR reactor was designed and constructed 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.
The reactor was tested initially under cold conditions to ensure steady circulation of the oxygen carrier between the two reactor sections. Subsequently, detailed experimental studies were conducted to determine operating and control strategies for the ICR during reactive experiments.
The reactor was commissioned under reactive conditions in 2017 to successfully demonstrate both CLC and CLR operation under atmospheric pressure. Reliable oxygen carrier circulation and good fuel conversion were observed. These campaigns also generated valuable experience with respect to controlling the oxygen carrier circulation rate, maximizing the CO2 capture efficiency and purity, and avoiding excessive oxygen carrier elutriation out of the reactor.
Dedicated experimental campaigns were completed during 2019 under pressurized conditions up to 3.7 bar. The preliminary tests have revealed promising results with no unexpected problems. Operation at higher pressure required the use of an additional air compressor. The needed infrastructure was recently implemented in the lab and additional experiments are being completed to evaluate the ICR performance at higher pressures.
The postdoc researcher has been working to deploy the modelling tools to assess the commercial feasibility of the pressurized ICR concept applied to a CLC-based natural gas-fired power plant. The use of an additional combustor after the CLC reactor has been investigated to raise the stream temperature beyond the maximum reactor operating temperature to maximize power cycle efficiency. This strategy has shown promising results to reduce the energy penalty of CO2 capture to as little as 1 %-point, whereas the best post-combustion CO2 capture systems impose a penalty of 8 %-points.
Reactor simulation with multiphase flow modelling was used to design a large-scale ICR for conducting the economic assessment of the natural gas CLC plant with added firing. The flow and reactions within the large-scale ICR were simulated in detail using the filtered Two Fluid Model to reveal reliable solids circulation and high CO2 capture. To maximize accuracy, newly developed models were implemented for the most important physical phenomena: drag, solids stresses and reaction rates.
The economic assessment has shown that added firing with natural gas after the CLC unit can almost halve CO2 avoidance costs relative to conventional systems. However, combustion of natural gas after the CLC unit reduces the CO2 capture efficiency of the plant. This firing must be done with hydrogen to achieve high CO2 avoidance. Subsequent work on integrating CLC with membrane-assisted CLR for efficiently supplying this clean hydrogen showed that the energy penalty could be reduced to as little as 3.6 %-points for power production and 1.9 %-points for combined power and hydrogen production with near-complete CO2 capture.
Overall, the successful experimental demonstration and promising techno-economic assessment results create a sound basis for further scale-up and demonstration of the ICR concept.
The completed work in this project is in line with the strategies of Research Council of Norway and Norwegian industry for development of next generation cost effective capture technologies. This has been achieved through development of a novel concept and its feasibility demonstration for reducing technical and financial uncertainties. The ICR concept promises to significantly accelerate the commercial rollout of vitally important CO2 capture processes which will play a crucial role in ensuring the long term future of our modern society.
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 tools for the dynamic process simulation of solids processes. An industrial partner, ANDTRITZ AG, will ensure industrial relevance.