Solid-Fueled Pressurized Chemical Looping with Flue-Gas Turbine Combined Cycle for Improved Plant Efficiency and CO2 Capture
University of Kentucky Center for Applied Energy Research
Project Number: DE-FE0009469
The University of Kentucky Center for Applied Energy Research is developing a heat-integrated coal-based combined cycle system for highly efficient power generation. This system will use a pressurized chemical looping combustor (PCLC) to produce high-temperature flue gas for electricity generation through a gas-turbine and a heat recovery unit for supercritical steam production to drive a conventional steam cycle. The PCLC consists of two reactors: (1) an Oxidizer in which oxygen from air is selectively fixed into an oxygen-carrier structure, and (2) a Reducer (Redox) in which coal is burned by the oxygen carrier. The PCLC will generate two gas streams: (1) a high-temperature, high-pressure, alkali-free, clean gas from the oxidizer used to drive an aero-turbine (Brayton Cycle) followed by a heat-recovery steam generator for a Rankine Cycle, and (2) a small volume CO2-enriched stream from the Redox for storage or beneficial use. In addition, the system will use a cost-effective, abundant, iron-based oxygen carrier. With the presence of water vapor in the CLC system, iron-based oxygen carriers show moderate reactivity and capacity, and high resistance to water vapor, ash and attrition.
| The PCLC Process Under Development (click to enlarge)
Additionally, the system will address known technical obstacles that impede the application of CLC to solid fuels by including: (1) use of pulverized coal to increase reaction kinetics and facilitate separation of the spent oxygen carrier from the solid coal residues (ash/carbon); (2) use of a moderate-temperature pyrolyzer to suppress carrier agglomeration and reduce pollutants (~96% of the Hg and portions of the sulfur and alkali); and (3) division of the Redox into two chambers, a down-flow moving bed acting as a gasifier and a partial-reduction reactor for the oxygen carrier, and a low-velocity bubbling bed serving as a deep-reduction reactor and a device for separating the reduced oxygen carrier from the solid coal residues on the basis of density and particle size. Flue gas from the Redox - primarily CO2 and H2O with a limited quantity of CO and H2 - will be compressed to the CO2 critical point at which the H2O, CO, and H2 are removed leaving a concentrated CO2 stream (>90%). Heat transfer units are not needed in the Oxidizer or Redox, thereby avoiding the corrosion and erosion associated with heat-transfer surfaces.
Related Papers and Publications:
- For further information on this project, contact the NETL Project Manager, Bruce Lani.