Coal energy conversion with carbon sequestration via combustion in supercritical saline aquifer water

摘要

The standard idea for deep saline aquifer sequestration is to separate carbon dioxide from a process stream, compress it, and inject it underground. However, since carbon dioxide is less dense than water, even at the high pressures found in aquifers,it is buoyant and will move towards the surface unless trapped by an impermeable seal. Also, significant energy expenditure is required to separate and compress carbon dioxide, even though neat carbon dioxide is not a desired product. These issues may beaddressed by combining the idea of fast dissolution at the surface with supercritical water oxidation (SCWO). By burning coal at high pressure in supercritical water drawn from an aquifer, and then sequestering the entire pre-equilibrated effluent, allcarbon from the fuel is captured, as well as all non-mineral coal combustion products including sulfur and metals. A possible block diagram of an SCWO-based electric power plant is proposed, including processes to handle salts from the aquifer brine andminerals from coal. The plant is thermodynamically modeled, using an indirectly fired combined cycle to convert energy from hot combustion products to work. This model estimates the overall thermal efficiency that can be achieved, and reveals unanticipated interactions within the plant that have significant effects on efficiency. The assumptions and results of the model highlight design challenges for an actual system.