PEP Review 2009-10
Ammonia from Natural Gas by the Lurgi-Casale Megammonia Process
Published: June 2009
Lurgi and Ammonia Casale have disclosed their jointly developed ammonia process tech-nology that is designed to produce 4,000 metric tons per day of ammonia. The main features of the Lurgi-Casale MEGAMMONIA process are: (1) replacing air used in the steam methane reforming steps of a conventional ammonia plant with oxygen, (2) use of Casale axial-radial internals in shift and ammonia synthesis reactors, (3) use of a liquid nitrogen wash instead of methanation, and (4) a high capacity single train ammonia plant with higher operating pressures.
In view of the benefits of oxygen-blown autothermal reforming employed in recently constructed gas-to-liquids (GTL) units and possible economies of scale for a single train 4,000 metric ton-per-day ammonia plant, this review evaluates a speculative SRIC design based roughly on the large-scale ammonia production technology jointly developed by Lurgi and Ammonia Casale which employs an air separation unit (ASU) to supply gaseous oxygen being used as the oxidant for synthesis gas generation and nitrogen for ammonia synthesis that is added in a nitrogen wash unit just upstream of the synthesis gas compressor.
Our work suggests that for a single train ammonia unit with a capacity of 4,000 metric tons per day, the cost increase associated with the oxygen supply is more than offset by the resultant size reduction in the reforming, CO shift, CO2 removal and final purification process units due to the smaller, nitrogen-free streams passing through these units made possible by the use of oxygen rather than air in the synthesis generation section of the plant. The absence of inert components in ammonia synthesis gas stream also improves ammonia synthesis loop design and operation. There are also environmental benefits such as reduced carbon dioxide and NOx emissions resulting from synthesis gas generation via advanced oxygen-blown autothermal reforming. Overall capital and operating costs are reduced enough to result in a seven percent reduction in ammonia production costs.