(274g) Optimal Design of Gas-Fired Moving-Bed Chemical Looping Combustion Systems
The Institute for the Design of Advance Energy Systems (IDAES) is developing a comprehensive, next generation computational framework  to facilitate the design and optimization of innovative energy systems and related chemical engineering systems. The IDAES framework is developed in Pyomo , an open-source Python-based AML, and not only supports a wide range of optimization solvers, but also provides a library of open (editable) standard and complex unit operation models . In this study, we demonstrate the capabilities of the IDAES framework by presenting the development of a complex unit model and its use in a multi-objective flowsheet optimization problem. The application area of interest is the optimization of methane-based chemical looping combustion (CLC) systems using different oxygen carrier materials.
CLC is a novel, promising advanced energy technology for the conversion of fossil fuels with inherent carbon capture. It consists of the cyclic reduction-oxidation of an oxygen carrier, generally a metal oxide, circulating between two reactors: a fuel (reducer) reactor and an air (oxidizer) reactor. The oxygen necessary for fuel conversion in the reducer reactor is provided by the oxygen carrier, thus ensuring combustion in pure oxygen rather than air. The exhaust gas leaving the fuel reactor is mainly a mixture of carbon dioxide (CO2) and water (H2O) from which H2O can be condensed resulting a CO2-rich stream ready for utilization or storage. Under carbon-constrained scenarios, CLC is an attractive alternative to conventional technologies due to its high efficiency and lower cost compared with post-combustion CO2 capture.
The goal of this work is the optimal design of the chemical looping reactors for methane combustion carried out in two interconnected moving-bed (MB) reactors. Detailed models of MB reactors for CLC are currently lacking in the literature. In our previous work, a 1-D steady-state, nonisothermal, first-principles model of a MB reactor with hydrodynamics under reduction conditions was developed. The model is flexible and modular, and it can be readily adapted for the simulation of different gas-solid processes . In this study, first an oxidizer reactor model is developed by modifying the reducer reactor model. Then, the development of a flowsheet for the CLC of methane using three promising oxygen carriers, Fe-, Cu-, and Ni-based carriers, is presented. Detailed property packages along with the kinetic models  governing the reduction and oxidation reactions of the different oxygen carriers are developed and used in the MB models. Finally, the equation-oriented process flowsheet is used to optimize the efficiency of the fuel reactor, while minimizing the capital and operational costs. The large-scale multi-objective optimization problem is solved using IPOPT. The feasibility of the interconnected MB reactor system for the combustion of methane with each oxygen carrier is investigated and the optimal design of the reactors is determined.
- Miller D.C., Siirola J.D., Agarwal D.A., Burgard A.P., Lee A., Eslick J.C., Nicholson B.L., Laird C.D., Biegler L.T., Bhattacharyya D., Sahinidis N.V., Grossmann I.E., Gounaris C.E., and Gunter D., 2018, âNext Generation Multi-Scale Process Systems Engineering Frameworkâ, Proceedings of the 13th International Symposium on Process Systems Engineering, San Diego, California, USA.
- Hart W.E., Laird C.D., Watson J.-P., Woodruff D.L., Hackebeil G.A., Nicholson B.L., and Siirola J.D., 2017, âPyomo â Optimization Modeling in Pythonâ, Second Edition. Vol. 67. Springer.
- Lee A., Ghouse J.H., Chen Q., Eslick J.C., Siirola J.D., Grossmann I.E., Miller D.C., 2018, âA Flexible Framework and Model Library for Process Simulation, Optimization and Controlâ, Proceedings of the 13th International Symposium on Process Systems Engineering, San Diego, California, USA.
- Ostace A., Lee A., Okoli C.O., Burgard A.P., Miller D.C., and Bhattacharyya D., 2018, âMathematical Modeling of a Moving-Bed Reactor for Chemical Looping Combustion of Methaneâ, Proceedings of the 13th International Symposium on Process Systems Engineering, San Diego, California, USA.
- Abad A., Adanez J., Garcia-Labiano F., de Diego L.F., Gayan P., and Celaya J., 2007, âMapping of the range of operational conditions for Cu-, Fe-, and Ni-based oxygen carriers in chemical-looping combustionâ, Chemical Engineering Science, 62, pp. 533-549