PEP Review 2004-11
Published: December 2004
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.