PEP Review 2004-11
Recent developments in oxygen assisted reforming, often referred to as "Mega
Reforming" or "Auto Thermal Reforming" has resulted in a significant
increase in the size of new methanol plant designs that offer substantially
improved economics over smaller conventional reforming based methanol plants.
In this review we examine the benefits of the use of similar modifications
to the reforming sections of ammonia plants. Although the potential benefits
of mega reforming are somewhat reduced for ammonia production because most
modern ammonia processes already employ air in the reforming stage in order
to supply the needed nitrogen, some economies of scale are still possible
for the mega ammonia production using oxygen assisted reforming technology
for ammonia production. This review evaluates a speculative SRIC design based
roughly on technology offered by Lurgi which employs an air separation unit
to produce oxygen for use in the reforming section and subsequently adds back
the just prior to entering the ammonia synthesis reactor. The increased cost
of the air separation unit is more than offset by the resultant reduction
in the size of the reforming, shift, CO2 removal and methanation sections
of the process due to the smaller nitrogen free-streams for these units made
possible by the use of oxygen rather than air in the reforming/partial oxidation
section of the plant. The nitrogen from the air separation unit is added back
into the feed stream just prior to entering the synthesis loop, after all
the hydrogen production and purification is completed. The cost of the ASU
plant is also offset by eliminating the air compressors used in the conventional
process, since we have chosen to use a packaged air plant that produces both
oxygen and nitrogen at the required pressures. Overall capital and operating
costs are reduced enough to result in nearly a twenty percent reduction in
fully loaded manufacturing costs for ammonia.
By George Intille
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