Q & A > Question Details
I am studying the conversion of two stages crude dehydration/desalting train to operate as two separate units due to increased wet crude oil production from oilfields. Much apprecaite if someone can share thier experiences, what factors / paramters should be considered for the conversion and is it really feasible to proceed further.
 
Answers
17/09/2013 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Switching from a two stage operation to two parallel stages will typically increase throughput at the expense of reduced salt removal efficiency. One factor that often gets overlooked when carrying out this design change is the impact on inlet and outlet distributor design. If you keep close to the same total feed rate, going to parallel operation will cut the feed rate to each vessel in half, which reduces the DP across the distributor by a factor of 4. Such a large reduction in flow through distributors can lead to poor distribution and much worse than expected performance from the change.
If your goal is dehydration switching to parallel operation makes sense. If your goal is to improve overall salt removal, going to parallel operation on a desalter is not typically a good idea. If you are at an upstream treater dehydration is normally the primary goal so parallel operation almost always makes sense because it reduces the flow rate per vessel.
13/08/2013 A: keith bowers, B and B Consulting, kebowers47@gmail.com
The de-watering of field production is best accomplished at the crude gathering center with 'heater-treaters designed for de-watering rather than the refinery for two reasons.
1) the removed 'produced water' can be re-cycled into the field for water-flood or steam-flood use.
2) 'De-salting' units are designed to introduce Fresh water into the crude to wash out small amounts of inorganic salts entrained in the oil to avoid their corrosion causing deposition in distillation equipment. Bulk water in the produced crude is almost always very salty and will severely decrease the effectiveness of the Fresh Water washing needed to remove salts.