Q & A > Question Details
We are facing problem with debutanizer reboiler operation due to fouling and we didn't get enough reboiling and bottom temperature. It forces us to reduce the plantload and reduce debutanizer feed. Can increase in debutanizer feed temperature help us to process more feed? And if we increase the stripper bottom temperature, what are other precautions to be considered? Like increase in stripper pressure with respect to temperature for fuel gas specification.
11/10/2014 A: Celso Pajaro, Sulzer Chemtech, celso.pajaro@sulzer.com
Increasing feed temperature should reduce the reboiler duty, you need to check the hydraulics of the trays above the feed since vapor and liquid load will increase.
Increasing stripper bottom temperature by increasing the pressure it will not provide too much heat to the debutanizer feed.
Why is the debutanizer reboiler fouled? do you know the cause of fouling?
09/10/2014 A: Marcello Ferrara, ITW SrL, mferrara@itw.it
We have cleaned Debutanizer reboilers in as low as 24 hours "oil-to-oil"
Please contact me privately to discuss about the problem and our solution.
09/10/2014 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
First, let’s assume a configuration:
The lean oil is recycled debut bottoms, and main frac OH liquid is fed several trays below the top of the primary absorber.
- Increasing stripper bottoms temperature will unload the debut reboiler but add load to debut overhead condensing system and tray loadings above the debut feed tray.
- Temperatures throughout the absorber will increase. To offset that and maintain target propane in fuel gas product will require increasing lean oil circulation, which will add load to the debut reboiler, which you are trying to unload.
- Instead of increasing the lean oil rate, the sponge oil rate can be increased, if capacity to do so exists. It is not uncommon in debottlenecking projects to make the sponge oil column an extension of the lean oil operation and reduce the “sponge” effect, allowing trace naphtha in the fuel gas, to be recycled from the fuel gas K.O. drum. Propane spec in the fuel gas can still be met.
- Arbitrarily increasing the stripper pressure will not help because higher absorption pressure requires even higher lean oil rate.