(465c) Carbon Dioxide Capture Using Flue Gas Waste Heat

Coal fired power plants currently generating approximately 50% of electricity in the United States are projected to emit 6.4 billion metric tons of CO2 in 2030. These carbon dioxide emissions could have serious consequences on the Earth's ecosytem. The current state of the art technology, monoethanolamine (MEA), requires heating to approximately 100-120 °C using power plant steam to regenerate the solvent. This gives a parasitic power demand of 22-30% of the power plant output. Our multiphase CFD calculations for the circulating fluidized bed concept and our sorption rate date for potassium carbonate sheets and that of RTI of sodium carbonate powders show that carbon dioxide an be easily captured from cooled coal fired power plant stack gases. For 90% CO2 removal we project the sorber heights to be 3 to 6 meters high, with parasitic energy consumption of about 6 kJ/g-mol CO2 vs. 393 kJ/g-mol CO2 for carbon combustion. Sorbent regeneration can be achieved by reducing the pressure in the regenerator to one third of an atmosphere or smaller at about 80 °C. Regeneration of the sorbent takes place in a reduced pressure regenerator, with the regeneration kinetics given by mass transfer coefficient times the difference between the equilibrium and operating pressures. We are modeling a complete loop consisting of the sorber which removes CO2 and H2O from cooled flue gases, a regenerator with reduced pressure that produces CO2 and H2O removed by a vacuum fan, and fluidized standpipes. The temperature of the circulating fluidized bed system is nearly constant, since the heat liberated in the sorber is carried into the regenerator by the sorber particles. This new idea accounts for the high efficiency of system.