CCS and Power Systems

Advanced Energy Systems - Coal and Coal/Biomass to Liquids

Advanced Energy Systems - Fuels

Performer: NETL On-Site Research

Project No: FWP-2012.03.05


A new alloying concept for preparing novel separation materials, referred to as "high entropy alloys", has been explored. High-entropy alloys are formed by synthesizing multiple principal elements in equimolar or near equimolar concentrations, which may lead to greater stability. The high-entropy alloys that were investigated contained six principal elements (cobalt, chromium, copper, iron, nickel, and aluminum) plus boron added at various proportions. Their stability in a post water-gas shift reactor environment was tested gravimetrically for corrosion resistance in simulated syngas containing 0, 0.01, 0.1, and 1 percent hydrogen sulfide (H2S) at 500 degrees Celsius (°C). No significant corrosion of these alloys was detected under syngas conditions of 0 and 0.01 percent H2S whereas significant corrosion was observed under syngas conditions of 0.1 and 1 percent H2S. Evidence suggests that greater stability can be obtained by minimizing the amount of copper in the alloy.

One of the outcomes of previous tests exposing alloys to "real" syngas performed in collaboration with the National Carbon Capture Center (NCCC) in Wilsonville, Alabama, was that minor gas stream components such as arsenic (As) and selenium (Se) may play a more significant role in membrane activity and stability than previously thought. Uptake of these contaminants by alloys was significant during exposure to a slipstream of real syngas. For this reason, an existing test apparatus is being modified to accommodate simultaneous exposure testing of up to 48 coupons to simulated syngas containing As and/or Se.

Materials Development

  • Developed and tested a multi-component metal alloy stable for 120 hours in syngas containing sulfur and other trace impurities at ~500°C.
  • Completed NCCC tests on coupons exposed to slipstream syngas; the impact of As and Se on membrane activity and stability needs to be addressed. 
  • Designed and modified a test apparatus to conduct an in-house study on the effect of As and Se exposure on membrane materials.
  • Completed "Proof of principle" scale tests for the conversion of coal gas components (e.g., methane).
  • Synthesized and evaluated several molybdenum-based catalysts to address methane (C1) hydrocarbon conversion efficiency.

Process Development

  • Evaluated lab-scale performance of a multi-tube pilot-scale membrane module; computational studies suggest that 80 percent separation efficiency can be attained while achieving program targets of 95 percent H2 recovery and > 40 percent product purity.

Performance Validation

  • Evaluated performance of an Eltron membrane tube in simulated syngas.

Project Details