Plantwide control of chemical looping combustion

Passive systems theory is used to develop a general procedure to design the control structure of chemical process networks. A natural storage function, derived from the second law of thermodynamics, is the basis for passivity-based control design. The inventory control laws are implemented locally and individual units become passive. With all units in a chemical processing plant designed to be locally passive, the entire network will be passive and retain desirable properties such as L₂ input-output stability and Lyapunov stability. The procedure presented allows for the decomposition of large flowsheets and the design of passivity-based control laws with little process information. The minimum number of controlled inventories to assure passivity of the entire network is identified. Additional degrees of freedom are available for constraint handling, flow control and determining the process load. The chemical looping combustion process is used as an illustrative example for the procedure.