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Integration of ITM Oxygen with a Decarbonized Fuel Plant for Co-production of Hydrogen and Clean Electric Power

IP.com Disclosure Number: IPCOM000019424D
Publication Date: 2003-Sep-12
Document File: 4 page(s) / 190K

Publishing Venue

The IP.com Prior Art Database

Abstract

The Ion Transport Membrane (ITM) Oxygen process uses nonporous, mixed-conducting, ceramic membranes that have both electronic and oxygen ionic conductivity when operated at high temperature, typically 800 to 900 ºC. The mixed conductors are inorganic mixed-metal oxides that are stoichiometrically deficient of oxygen, which creates oxygen vacancies in their lattice structure. Oxygen from the air feed adsorbs onto the surface of the membrane, where it dissociates and ionizes by electron transfer from the membrane. The oxygen anions fill vacancies in the lattice structure and diffuse through the membrane under an oxygen chemical-potential gradient, applied by maintaining a difference in oxygen partial pressure on opposite sides of the membrane. At the permeate surface of the membrane, the oxygen ions release their electrons, recombine, and desorb from the surface as oxygen molecules. Since no mechanism exists for transport of other species, the separation is 100% selective for oxygen, in the absence of leaks, cracks, or flaws in the membrane.

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Integration of ITM Oxygen with a Decarbonized Fuel Plant

for Co-production of Hydrogen and Clean Electric Power

The Ion Transport Membrane (ITM) Oxygen process uses nonporous, mixed-conducting, ceramic membranes that have both electronic and oxygen ionic conductivity when operated at high temperature, typically 800 to 900 ºC. The mixed conductors are inorganic mixed-metal oxides that are stoichiometrically deficient of oxygen, which creates oxygen vacancies in their lattice structure. Oxygen from the air feed adsorbs onto the surface of the membrane, where it dissociates and ionizes by electron transfer from the membrane. The oxygen anions fill vacancies in the lattice structure and diffuse through the membrane under an oxygen chemical-potential gradient, applied by maintaining a difference in oxygen partial pressure on opposite sides of the membrane. At the permeate surface of the membrane, the oxygen ions release their electrons, recombine, and desorb from the surface as oxygen molecules. Since no mechanism exists for transport of other species, the separation is 100% selective for oxygen, in the absence of leaks, cracks, or flaws in the membrane.

To balance the mechanical load on the membrane with the desired oxygen partial pressure driving force, the process operates with a medium-pressure air feed stream, typically 7 to 20 atmospheres, and a low-pressure oxygen permeate stream, typically at less than one atmosphere, although higher air feed pressures or oxygen product pressures may be used. Since oxygen ion transport is thermally activated, the basic process cycle must also include the means to heat the pressurized air feed to the membrane operating temperature, either by indirect heat exchange, direct firing with fuel, or a combination of both. To achieve a suitable cycle efficiency, the energy associated with the hot, pressurized, non-permeate stream can be recovered by integrating the ITM Oxygen membrane with a gas turbine power generation system.[1],[2] This is accomplished by extracting air from the compressor discharge, withdrawing a portion of the oxygen by permeation through the membrane, and returning the vitiated, non-permeate stream to the turbine inlet. A direct- or indirect-fired heater upstream of the ITM Oxygen vessel raises the air stream temperature to the membrane operating value by burning a portion of the gas turbine’s usual fuel input. Downstream of the ITM Oxygen vessel, the gas turbine combustor achieves the required turbine inlet temperature by burning the remainder of the fuel in the vitiated non-permeate stream, which still contains excess oxygen.

A “Decarbonized Fuel Plant” produces hydrogen from fossil fuels while recovering carbon dioxide for offsite processing or sequestration. In a June 1999 report to the DOE, the Parsons Corporation outlined several conceptual plant designs utilizing developing technologies to assess the economic feasibility of this type of facility. Figure 1 shows a simplified bloc...