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In order to achieve higher gas oil recovery, we are working on a conceptual project of installing a vacuum flasher on the D/S of VDU. VR from VDU column bottom will be heated and flashed in a separate column having flsha zone pressure lower and temperature higher than that of VDU column flash zone. Preliminary simulations suggests the technical feasibility. We want to confirm that whether such a set-up has been installed anywhere and what may be the foreseen challenges?
 
Answers
24/07/2009 A: S Banik, Centre for High Technology, sbdr@rediffmail.com
We also did a detailed process and engineering study for VBT flashing using sensible heat. We found flashing of slop is more feasible as metal content has to be minimised. Flashing of slop may help in affording more irrigation of the wash bed which is prone to coking. Engineering study along with cost estimate we found the return on capital is very attractive. However this is yet to be implemented as operating companies would like to have proven technology only.
31/05/2009 A: keith bowers, B and B Consulting, kebowers47@gmail.com
I am not aware of anyone trying to reflash VTB. If you intend to make 'clean' HVGO', some 'overflash' is necessary to wet and wash the entrainment eliminator grids or they will coke quickly. It may be prudent to 'undercut' some in the primary VDU, and leave more HVGO in the 'bottoms' to ensure there is enough material in there to vaporize, condense, draw, and wash the grids.
Preliminary Simulations are not nearly precise enough to support this operation. You MUST have very good TBP distillation data. I am not sure if SIMDIS (gas chromatograph) method will work or not--it depends on the crude and HVGO/Resid ratios. A conventional TPB vacuum distillation might be better, but the lab techs and Chemist MUST be highly skilled and clever to produce data precise enough to use as 'simulator input.'
There is a specialist consulting/engineering firm located in Houston that makes their living designing deep cut VDUs (and fixing others mistakes.) I suggest you get them involved NOW to ensure you are not attempting the infeasible.