as a maritime fuel and may also be used for industrial transportation applications in rail and trucking operations. CO 2 capture is integral to ammonia production In many large-scale ammonia plants, hydrogen is produced using a two-stage reforming process. The primary reformer is generally an SMR. The secondary reformer is an autothermal reformer (ATR), which requires oxygen for partial oxidation reactions. In this configuration, oxygen has traditionally been supplied by introducing air, as shown in Figure 2 . The nitrogen that enters with the air remains in the process to be reacted with hydrogen in the ammonia synthesis loop. Following the reformers, high-temperature shift and low-temperature shift reactors convert carbon monoxide (CO) and steam to hydrogen and CO 2 . Subsequently, the CO 2 is removed using absorption and desorption in a solvent. The CO 2 must be removed from the gas stream prior to ammonia synthesis since any oxygen-containing molecules such as CO 2 , CO, and water (H 2 O) would poison the ammonia synthesis catalyst. Hot potassium carbonate (HPC) is commonly used for this pre-combustion CO 2 capture application. After removing most of the CO 2 from the gas stream, there are drying and methanation stages. Methanation converts any residual CO and CO 2 to methane (CH 4 ) through a reaction with hydrogen, which is present in the gas mixture.
Leaving the methanation reactor, the gas is a mixture of nitrogen and hydrogen, with small amounts of methane and argon. Methane and argon are removed using a cryogenic nitrogen wash, such as the technology used in the KBP Purifier ammonia process. This purge gas can be burned in the SMR to yield heat for the reforming reactions. The Burrup Fertilizers Ammonia Plant in Australia, now owned by Yara, was commissioned in April 2006. At that time, it was the largest implementation of the KBR Purifier process. The maximum ammonia production capacity is 2,600 tonnes per day (t/d). In 2019, EuroChem Group AG started up a new 2,890 t/d ammonia plant based on KBR’s Purifier ammonia technology. The facility is the largest ammonia plant in Europe. The CO 2 emissions from either the Burrup or EuroChem ammonia plant would be more than 2,000,000 tonnes per year (t/a). Since this CO 2 must be removed from the process to enable ammonia synthesis, there is no additional capital or operating cost associated with the CO capture aspect of CCS. With a small incremental investment in CO 2 drying and compression, CO 2 from ammonia facilities can be transported by pipeline to a suitable sequestration location. Nitrogen and oxygen production for ammonia synthesis An alternative pathway for ammonia synthesis is to react pure nitrogen and pure hydrogen
Burner ue gas
Air
CO
Purge gas
Natural gas feed
Haber-Bosch ammonia synthesis reactor
CO desor- ption
Steam
Super- heated steam
Feed compressor
Steam generation
Hydrogen
ATR
Purge gas
High temp. shift
Hydrogen- ation
SMR
Condenser
Catalyst bed
Phase separator
Steam generation
Raw syngas
Low temp. shift
Sulphur removal
Cryogenic heat exchanger
NH
Boiler feed water
Recycle compressor
Liquid ammonia
Fuel Air
Distillation column
Condensate
Feed preparation
Reforming
CO removal
Methanation and cryogenic nitrogen wash
Ammonia synthesis
Ammonia liquefaction and storage
Water gas shift reactors
Figure 2 Air-fed ammonia production process
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