The purpose of this work is to quantitatively compare the energy cost of design alternatives for a process to produce ammonia (NH 3 ) from air, water, and renewable electricity. It is assumed that a Haber–Bosch (H–B) synthesis loop is available to produce 1000 metric tons (tonnes) of renewable NH 3 per day. The overall energy costs per tonne of NH 3 will then be estimated at U.S.$195, 197, 158, and 179 per tonne of NH 3 when H 2 is supplied by (i) natural gas reforming (reference), (ii) liquid phase electrolysis, (iii) solid oxide electrolysis (SOE) of water only, and (iv) simultaneous SOE of water and air. A renewable electricity price of U.S.$0.02 per kWh electric , and U.S.$6 per 10 6 BTU for natural gas is assumed. SOE provides some energy cost advantage but incurs the inherent risk of an emerging process. The last consideration is replacement of the H–B loop with atmospheric pressure chemical looping for ammonia synthesis (CLAS) combined with SOE for water electrolysis, and separately oxygen removal from air to provide N 2 , with energy costs of U.S.$153 per tonne of NH 3 . Overall, the most significant findings are (i) the energy costs are not substantially different for the alternatives investigated here and (ii) the direct SOE of a mixture of steam and air, followed by a H.–B. synthesis loop, or SOE to provide H 2 and N 2 separately, followed by CLAS may be attractive for small scale production, modular systems, remote locations, or stranded electricity resources with the primary motivation being process simplification rather than significantly lower energy cost.
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Chemical Looping of Manganese to Synthesize Ammonia at Atmospheric Pressure: Sodium as Promoter
Affordable synthetic ammonia (NH3) enables the production of nearly half of the food we eat and is emerging as a renewable energy carrier. Sodium‐promoted chemical looping NH3synthesis at atmospheric pressure using manganese (Mn) is here demonstrated. The looping process may be advantageous when inexpensive renewable hydrogen from electrolysis is available. Avoiding the high pressure of the Haber‐Bosch process by chemical looping using earth‐abundant materials may reduce capital cost, facilitate intermittent operation, and allow operation in geographic areas where infrastructure is less sophisticated. At this early stage, the data suggest that 0.28 m3of a 50 % porosity solid Mn bed may suffice to produce 100 kg NH3per day by chemical looping, with abundant opportunities for improvement.
more » « less- Award ID(s):
- 1856084
- NSF-PAR ID:
- 10255134
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemical Engineering & Technology
- Volume:
- 43
- Issue:
- 10
- ISSN:
- 0930-7516
- Page Range / eLocation ID:
- p. 2126-2133
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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