Metallurgical and Catalyst Effects from Airflow Condition into HTS

摘要

The initial startup and reduction of the High Temperature Shift (HTS) catalyst is a procedure whichrnis performed relatively infrequently in ammonia plants. This procedure allows for a safe, controlledrnreduction of the HTS catalyst primarily by operating at a high S/G ratio at the Primary Reformer. Arnproper initial startup is important to ensure that the catalyst is able to achieve maximum CO conversionrncombined with a long on-stream life. While many ammonia plants (including the CF IndustriesrnVerdigris site) have performed HTS startups with no problems, events can occur that can lead to poorrncatalyst performance, reduced HTS reactor efficiency, and more serious issues including loss of vesselrnintegrity.rnIn 2010 - the CF Industries No. 1 Ammonia Plant in Verdigris, OK installed a reload of ShiftMax®rn120 HTS catalyst. The reduction was deemed a success and the plant came up to normal operatingrnrates. Upon the first detailed analysis of catalyst performance after startup, the HTS catalyst CO conversionrnwas less than expected. This trend continued for 1 year until the plant decided that they couldrnnot continue to operate at this HTS performance level. Upon shutdown in 2011 and subsequent analysisrnof initial startup process conditions after the HTS catalyst reduction, it was found that air hadrnbeen inadvertently introduced into the HTS reactor with reduced catalyst. This caused a previouslyrnundetected exotherm through the catalyst bed which damaged catalyst and raised several vessel integrityrnquestions.rnThis paper explains the effects of the air introduction into the HTS reactor, including metallurgicalrnconcerns and steps taken to ensure proper vessel integrity and safety, the effect this event had on thernHTS catalyst, and overall lessons learned.