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Novel Tri-Metallic Ferrite Oxygen Carriers Enhance Chemical Looping Combustion

Date Posted
USPN 9,797,594

Opportunity

A patented technology invented at the U.S. Department of Energy’s National Energy Technology Laboratory enhances chemical looping combustion by providing tri-metallic ferrite oxygen carriers that offer greater durability and better reactivity than traditional oxygen carriers. Tri-metallic ferrite oxygen carriers also eliminate agglomeration issues, improve reduction rates, and offer similar costs when compared to traditional oxygen carriers, with convenient preparation using readily available materials. This technology is available for licensing and/or further collaborative research from NETL.

Challenge

Chemical looping combustion (CLC) is a promising technology for coal-derived energy production that involves combusting fuel in nearly pure oxygen to simplify carbon capture. In CLC systems, oxygen is introduced to the system via oxidation-reduction cycling of an oxygen carrier. Traditional oxygen carriers such as CuO, Fe2O3, NiO, and CoO have disadvantages including low reactivity (Fe2O3), low melting point and high agglomeration (CuO), and health and environmental concerns (NiO). The development of new oxygen carriers with enhanced performance characteristics is required for successful deployment of coal CLC processes.

Overview

Oxy-combustion power generation provides oxygen to the combustion process by separating oxygen from air. Chemical looping systems take advantage of oxygen internal to the process, cutting the large capital, operating, and energy costs associated with oxygen generation. However, the development of robust oxygen carriers is critical for the efficient operation and adoption of CLC technology.

 

NETL researchers have developed novel tri-metallic ferrite oxygen carriers that comprise CuxFeyMnzO4-8 – where CuxFeyMnzO4-8 is a chemical composition with generally 0.5≤x≤2.0, 0.2≤y≤2.5, and 0.2≤z≤2.5 – for CLC of solid fuels such as coal, pet coke, and biomass. The tri-metallic ferrite oxygen carrier is used by delivering it to a fuel reactor and mixing it with a carbon-based fuel at a reducing temperature, which reduces a portion of the carrier and oxidizes a portion of the fuel. Within the fuel reactor, the tri-metallic ferrite carrier interacts with the fuel and generates a reduced carrier. The reduced carrier subsequently enters an oxidation reactor, where it is infused with oxidizing gas to produce a re-oxidized carrier through an oxidizing reaction. The re-oxidized carrier, which comprises comprise CuxFeyMnzO4-8, may then be returned to the fuel reactor for a cyclic operation.

 

CLC offers a major advantage over conventional coal combustion by directly producing a concentrated stream of CO2 without expending the significant energy required for CO2 separation. This NETL technology offers numerous advantages over traditional oxygen carriers for coal CLC. Tri-metallic ferrites perform better when compared to Fe2O3, demonstrating high and stable reactivity over multiple reduction/oxidation cycles and high attrition resistance. Ferrite-based oxygen carriers also display a low tendency to agglomerate at high temperatures, as with CuO. These metal ferrites can be produced using readily available materials at a cost comparable to Fe2O3 and CuO oxygen carriers.

Advantages

  • Improved reduction/oxidation rates, durability and reactivity compared to Fe2O3
  • Eliminates agglomeration issues associated with CuO
  • Stable at high temperatures and over multiple oxidation-reduction cycles
  • Can be produced using readily available materials at comparable cost to standard oxygen carriers
  • Carriers are environmentally benign
Applications
  • Chemical looping combustion of coal
  • Chemical looping gasification of coal to produce synthesis gas
  • Combustion/gasification processes using biomass, pet coke, and other solid fuels

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