Inspection. Remediation. and Modification Of Two Large-Scale KAAP Ammonia Converters
Publication Date: 2012-May-08
The IP.com Prior Art Database
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LARGE-SCALE KAAP AMMONIA CONVERTERS
Kellogg Brown & Root (KBR) designed and constructed two 1850 MTPD ammonia plants utilizing the proprietary KBR Advanced Ammonia Process (KAAP)technology for Farmland MissChem Ltd. (FMCL) and PCS Nitrogen (PCS). Both facilities are located in Point Lisas, Trinidad and were commissioned in 1998.
After startup the Ammonia Converters in both facilities experienced an increase in pressure drop across the KAAP beds. The trend began at different times and developed at different rates in each facility, while kinetic performance remained stable for both plants. When the pressure drop reached levels that impacted plant capacity, each plant was shut down to inspect the converter internals, remediate the cause of the pressure drop, and make modifications asrequired to prevent recurrence.
The converters were shutdown and inspected individually. All activities including inspection, catalyst handling, internals cleaning, and catalyst reloading were conducted under an inert environment. Inspection findings were consistent with expectations from KI3R analyses and modifications were implemented to address key issues associated with the excessive pressure drop.
operating at design capacity pressure drogacross the Ammonia
2.0 Description of KAAP Ammonia Converter
The grassroots KAAP Ammonia Converter is a 4-bed, intercooled, radial-flow design as illustrated in Figure 1. Bed #I is a conventional magnetite catalyst bed and beds #2, 3, and 4 utilize KBR's proprietary K A A P catalyst. The gas flow path through the converter is generally downward, with feed entering the top head and the converter effluent exiting the bottom head.
Bed #1 utilizes a standard radial flow design. The gas flows through the magnetite bed from outside to inside with the catalyst contained in an annular space formed by two concentric profile wire screen baskets. The gas exiting bed #1 is cooled against the converter effluent in a shell and tube heat exchanger centered in bed #1 prior to entering bed #2, the first of the three KAAPbeds.
During the KAAF' development work, it was recognized that the unique properties of KAAP catalyst required specific design considerations for a commercial-scale reactor. The small particle size, the low bulk density, and the relatively small bed volumes associated with the high catalyst activity required consideration from both kinetic and hydraulic perspectives. In addition to the packaging issues, the carbon base material of the catalyst coupled with the
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During the initial stages of analyzing the high pressure drop, the possibility of catalyst fluidization in the freeboard bed was investigated by CFD modeling.
FLUENT (reg. Trademark),@ommercial CFD software, was used to model the freeboard bed sections of the converter. The approach taken was to model the catalyst bed as a porous media with the dimensions and levels of the freeboard catalyst bed. Resist...