Amine Injection Services for Hydrocrackers

Starting up a hydrocracker after a catalyst change out can be a complex and potentially perilous task, especially when high-activity cracking catalysts have been loaded in the unit. Some hydrocracking catalysts may become too active following the sulfiding step, preventing the introduction of reactive feed without experiencing serious temperature excursions. To moderate the activity of the cracking bed, nitrogen is often injected into the reactor in the form of aqueous or anhydrous ammonia. This step, called nitrogen passivation, effectively tempers the catalyst activity by bonding nitrogen atoms from the ammonia to the acidic sites on the zeolitic cracking catalyst. Once the cracking bed is saturated with nitrogen, feed can be introduced to the unit without the risk of excessive exotherms.

Handling ammonia is hazardous, however, and leaks or spills can lead to serious health and safety issues. This is particularly true with anhydrous ammonia, which forms a toxic vapor cloud if allowed to escape from a tank or piping. To exacerbate the problem, ammonia is typically injected at pressures of 1,000-2,000 psi. In addition, the pumps used to inject ammonia are notoriously difficult to prime and start up at these conditions.

To minimize the hazards of high-pressure ammonia injection, Reactor Resources recently introduced methyldiethanolamine (MDEA) injection for the nitrogen passivation of hydrocracking catalysts. When injected into the cracking bed at temperatures above 360°F in the presence of hydrogen, MDEA readily decomposes to form the ammonia needed to passivate the catalyst. The other decomposition by-products of MDEA are methane, ethane, and water.

MDEA has many advantages over ammonia and other amine compounds:

  • With a health hazard rating (HHR) of "1", MDEA is much safer to handle than ammonia, which has an HHR of "3" (severe poison).
  • MDEA is less odorous and is easier to pump at high pressures than ammonia.
  • The cost of MDEA is quite low compared to other amine compounds, and many refiners already use MDEA in their sulfur plant as a hydrogen sulfide absorbent.
  • Any excess MDEA remaining after the passivation step can be off loaded into the refiner’s on-site amine tank, eliminating restocking fees.
  • MDEA won't cavitate the charge pump like ammonia can. 

MDEA or similar amine compounds have now successfully been used on the start up of ten (10) hydrocracking units without any catalyst performance or safety issues. UOP has evaluated MDEA in pilot studies and found that it is no difference in performance as compared to ammonia passivation. MDEA eliminates the handling of toxic ammonia and allows for the quick and safe start-up of a hydrocracker after a catalyst change.

MDEA injection is the latest innovation Reactor Resources has introduced, complementing its other sulfiding technologies, which includes the SmartSkid Injection System, Online H2S Analyzer System, Hydrogen Purity Analyzer. and Total Sulfur Analyzer System.


Contact Us to discuss how our system can minimize your sulfiding costs and startup time while improving operator safety.


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