(116a) Induction Heating for the Ammonia Cracking Process

The electrification of industrial processes for compatibility with renewable energy has become a major area of interest, both commercially and within the Department of Energy. Process heating comprises more than half of the direct energy consumed by industrial processes and represents a massive opportunity for industrial electrification. Electric induction is a promising method for utilizing renewable energy to heat industrial processes. Due to the increased interest in hydrogen as an energy-dense, low-carbon power and fuel supply, ammonia has received strong consideration as a liquid hydrogen carrier due to its low storage and transportation costs. Ammonia cracking presents a unique opportunity to create on-demand green hydrogen. Hydrogen generated from ammonia cracking can be utilized by commercially available generators, fuel cells, and turbines or consumed in distributed markets including in hydrogen fueling stations, and for chemicals and transportation. For practical and commercial feasibility, these systems must demonstrate the ability to start-up from cold conditions and shut down with minimal latency. The endothermic ammonia cracking reaction can be initiated and sustained by direct induction heating of the catalyst bed; bypassing the heating of the reactor walls reduces the heating time and energy losses, thereby providing an efficient means to intermittently produce hydrogen gas in direct response to demand. The improved efficiency and rapid start-up and shut down from induction heating will enable the use of liquid ammonia as a hydrogen carrier, even at the small-scale.

This study seeks to demonstrate a reduction in energy consumption, faster heating times, and precise temperature control using induction heating. A ruthenium catalyst was used for the ammonia cracking reaction and iron powder used as the susceptor for the induction heating. A series of nine experiments was conducted which test three different temperatures (450 °C, 475 °C, and 500 °C) at three different gas hourly space velocities (GHSVs) (35,000 h-¹, 50,000 h^-1, and 65,000 h^-1). The induction experiments were conducted at ambient pressure with a 1:1 susceptor-to-catalyst volume ratio. The time required to reach steady state under each condition, the power input (W), and the hydrogen production were measured to determine the turnover frequency and the efficiency (kWh/mol H₂) for each run. Since iron is an active material for ammonia cracking, a test was run at each experimental condition with the iron susceptor alone to isolate the effect of the catalyst on the calculated parameters. Initial benchmarking of the reaction under the same battery of temperature and GHSV conditions was performed in a conventionally heated microreactor to determine the baseline turnover frequency, start-up times, and power input per mole hydrogen produced for comparison.