Process design and analysis of a novel carbon-capture-ready process for flexible-load power generation: Modular pressurized air combustion

Abstract

The rapid retirement of dispatchable, fossil-based electricity sources and the influx of intermittent energy sources, both driven by the impetus towards a low-carbon future, have led to concerns about the reliability of the grid. The future need for on-demand, rotating, inertial-based assets that can be low carbon and flexibly meet changing demand to balance against intermittency will be essential. Hence, future fossil-based power generation will need to be highly efficient and flexible, and have the ability to add carbon capture when required. This study describes the process design of a modular pressurized air combustion power plant, which involves burning coal in air under pressure in parallel, modular boilers. After treatment, the high-pressure flue gas is passed through a series of turbines and inter-heaters to recover most of the compression work. The high-pressure operation allows for thermal recovery of the latent heat of moisture of the flue gas by integration into the steam cycle, which results in a plant efficiency that is 1.7% higher than that of the conventional atmospheric air-fired power plant. Moreover, the modularity enhances the flexibility of the power plant, with an improved ability for load following. This work also discusses the path to convert the modular, pressurized-air combustion process to a staged, pressurized oxy-combustion process, which is one of the most promising carbon capture processes. This can be accomplished by adding a frontend air separation unit and a backend CO2 compression and purification unit.