In naptha hytotreater operating temp and pressure are 285 degc & 45 kg/cm2.in case feed loss emergency when again feed introduce & wht temp & pressure ?
Answers
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23/09/2018
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Ganesh Maturu, Self, maturu.ganesh@gmail.com
If feed pump establishes within 30 min, we may not need to reduce reactor temperature and pressure and directly start feed pump. If it takes more time to start feed pump, we need to reduce reactor temperature to 150 degC to avoid catalyst reduction in the absence of H2S in recycle gas loop.
Typically Naphta hydrotreater is vapor phase reactor and hence we need to ensure vapor phase at reactor inlet during feed cut-in. Calculate dew point temperature at reactor inlet pressure with 50% feed and maximum recycle gas flow using any simulator like Aspen Plus, KBC or HYSYS. If the dew point temperature is more than 150-160 deg C, reduce reactor system pressure and again check at what pressure we get dew point temperature near to 160 degC. So now, in Naphtha unit, reduce system pressure to calculated value in simulator and maintain reactor temperature to 170-180 deg C. After establishing this conditions with max gas flow based on compressor limit, start feed pump and maintain at turndown flow. This will ensure vapor phase at reactor inlet. If we increase feed flow directly to 100%, it may see 2 phase at reactor inlet. Typically maintain 50% pressure during feed introduction which gives dew point some margin. Then increase system temperature and pressure to normal conditions and then only increase feed to 100% throughput. This will ensure vapor phase at reactor inlet. If there is 2 phase in reactor inlet any time during startup may cause reactor maldistribution and significant increase in pressure drop during the course of its cycle.
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23/09/2018
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A:
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Assuming hydrogen circulation never stopped, establish normal pressure. Restart feed, establishing normal temperature. Ramp up feed to normal rate while maintaining normal temperature. The product should be on-spec throughout reintroduction of feed.
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