Advanced Combustion

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.