Pressurized oxy-coal combustion: Ideally flexible to uncertainties

• Proposed formulation to assess the flexibility of power generation processes facing uncertainties.
• Obtained ideal flexibility of pressurized oxy-coal combustion with respect to coal type.
• Performance of processes under uncertainty match performance of optimal processes for specific set of inputs.
• Stochastic programming is not required and instead hierarchic optimization is utilized.

Simultaneous multi-variable gradient-based optimization with multi-start is performed on a 300 MWe wet-recycling pressurized oxy-coal combustion process with carbon capture and sequestration, subject to uncertainty in fuel, ambient conditions, and other input specifications. Two forms of flue gas thermal recovery are studied, a surface heat exchanger and a direct contact separation column. Optimization enables ideal flexibility in the processes: when changing the coal utilized, the performance is not compromised compared to the optimum performance of a process specifically designed for that coal. Similarly, the processes are immune to other uncertainties like ambient conditions, air flow, slurry water flow, atomizer stream flow and the oxidizer stream oxygen purity. Consequently, stochastic programming is shown to be unnecessary. Close to optimum design, the processes are also shown to be insensitive towards design variables such as the areas of the feedwater heaters. Recently proposed thermodynamic criteria are used as embedded design specifications in the optimization process, rendering it faster and more robust.