(391e) Modeling and Control of Chemical Looping Combustion Process

Chemical looping combustion (CLC) is a promising clean technology for power generation. In this technology, metal oxides are looped between the oxidation and the reduction chambers thereby carrying oxygen from air to fuel. Thus, the combustion of fuel is accomplished without any direct contact between the fuel and the air. This prevents the formation of harmful gases and allows for the formation of pure CO2, making CLC a good candidate for CO2 sequestration. Much of the previous research in CLC has focused on the process chemistry of various metal oxide and fuel combinations. With the breadth of experimental data available, a mathematical model was previously developed to simulate the effects of process variables (metal oxides, fuel).1 The model uses a shrinking core mechanism and discretized population balances to simulate the solid-gas reactions. The mathematical model is useful for both design and control of the CLC process. Scaling up the CLC process from lab and bench scale experiments to a commercialized process requires a transition from simple control algorithms to a complex network of interacting controllers.

In the current study, we focus on proposing a suitable control strategy for the CLC process based on the proposed process model.1 The process relies on the use of two interconnected fluidized bed reactors with seals to maintain independent operation. However, the reactors must simultaneously operate with competing control objectives: 1) match power demand specifications; and 2) achieve complete oxidation of products. These objectives coupled with the fast natural system dynamics lead to a challenging control problem. Due to the interconnectivity of the two reactor systems and the steam cycle, decentralized control may lead to instabilities and poor system response. In such cases, the principles of inventory control for extensive variables: energy, entropy, and volume; and decomposition of the control system into a dynamic network can provide a stable design. In this work, based on the concept of inventories, we propose a robust control for the CLC process along with advanced control schemes for improved system response.

1. Balaji, S., Ilic, J., Ydstie, B. E., Krogh, B. H. Control based modeling and simulation of the chemical looping combustion process, Industrial Engineering & Chemistry Research, In press. DOI: 10.1021/ie901540m.