Refining Community Logo

HCGO quality

Home Forums Coking HCGO quality

This topic contains 3 replies, has 3 voices, and was last updated by  Jeff Pollard 6 years, 4 months ago.

  • Author
    Posts
  • #1619

    Freddy Martinez
    Participant

    We are facing problems of detoriorating HCGO quality at higher unit throughput (108% of design). This is a coker having typical low recycle 8%. The HCGO CCR (typical 1.5 wt%)/ asphaltenes (typical 1500 ppm) are high and backwash frequency of Peter Ronnintgen filter (every 1 hour) in the downstream hydrocracker unit is also not ideal. We have conventional bubble cap/shed trays in wash zone of the fractionator.
    We also find that backwash frequency of the filter increases tremendously by increasing above a particular threshold rate of HCGO in downstream hydrocracker unit.
    Does any body has similar experience and if yes, what was done to mitigate the issue in the shortterm.

  • #4436

    Jeff Pollard
    Participant

    Questions for you: 1) How many tubes and what is the micron rating of the elements in your Ronningen Petter filter? 2) What is the temperature and flow rate of liquid to this system?
    It would seem to me off the cuff that the current filter would backwash more frequently. You may want to shorten the time between backwashes to get a more consistent feed rate to the hydrocracker. But since your current filter normally needs 3-5 vessel volumes each to properly clean, you will have more backwash liquid to deal with.
    We are replacing such systems with gas-assisted backwash filters that use sintered powder media nominally rated in low single digits. Suggested operating temperature is between 450-550F. This should prevent the asphatenes from binding to the media.
    If there is consideration of replacing the current filter, we can provide lab analysis and a feasibility study. The initial capital costs are high by operating costs are minimal.

  • #4435

    Jeff Pollard
    Participant

    Questions for you: 1) How many tubes and what is the micron rating of the elements in your Ronningen Petter filter? 2) What is the temperature and flow rate of liquid to this system?
    It would seem to me off the cuff that the current filter would backwash more frequently. You may want to shorten the time between backwashes to get a more consistent feed rate to the hydrocracker. But since your current filter normally needs 3-5 vessel volumes each to properly clean, you will have more backwash liquid to deal with.
    We are replacing such systems with gas-assisted backwash filters that use sintered powder media nominally rated in low single digits. Suggested operating temperature is between 450-550F. This should prevent the asphatenes from binding to the media.
    If there is consideration of replacing the current filter, we can provide lab analysis and a feasibility study. The initial capital costs are high by operating costs are minimal.

  • #4434

    Mike Kimbrell
    Participant

    The wash zone you describe is not suitable for very low recycle rates. If you mean valve trays and not bubble cap trays, those trays have been successfully used at recycle ratios of 15% and higher. If the wash oil rate is too low, the trays will dry out and coke. 
    The very high concarbon and asphaltene content of the HCGO indicates that there is poor contact between the wash oil and the coke drum overhead vapors in the wash zone. If these trays are coked, about the only way to restore the performance is to shut the unit down and enter the tower and clean the trays. You could try to increase wash oil rate and then monitor the HCGO quality. If it improves, you may need to operate the unit at the higher wash oil rate until the next outage. 
    Once the backflush filters have been coated with asphaltenes, simple backflushing does not reduce the pressure drop across the filter elements. Removing each element individually and soaking it in hot water to melt the asphaltenes off the filter may be required. 
    Good luck. Let us know how you resolved this problem. 

You must be logged in to reply to this topic.

Refining Community