Q & A > Question Details
We have a single stage desalter that will run more heavy crude about API=23, Wash Water about 7%, T=280F. There are 2 Transformer about 150 kVa each. Is there a good way to assess what this existing transformer can handle in term of max conductivity of crude ? Are there easy calculations one can do if you had crude conductivity, etc?
28/04/2014 A: Vishnu Ram A S, RIL, vishnu.selvaraj@ril.com
If the metal contents are more in the crude blend, it is better to shift the Transformer tapping to lower capacity and keep the temperature of Desalter inlet between 145 to 150C. Beyond 150C, the load of the Transformer usually raises and reduces the Desalting Efficiency. Moreover it can result in Water carry over in worst case.
Crude like DOBA can conduct heavily with the more concentration of Calcium components. In that case, we need to reduce the pH of the Brine to enhance separation of Oil/Water inside the desalter vessel. pH may be reduced with weak organic acids available in the market..Better not to go with Inorganic acid injection to reduce the pH.
16/01/2014 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Current draw by the transformers is a function of the resistance of the system to current flow and the driving force (Voltage). Resistance is a function of the conductivity of the oil (inverse relationship) and the spacing between the grids. The voltage driving force will depend on which voltage tap is being used on the transformers. I suggest that you get with your desalter manufacturer to help you better understand how the crude change will impact desalter operation.
Conductivity of the oil actually feeding the desalter can be difficult to predict. It does not blend linearly or as best I can tell from discussions with desalter manufacturers even predictably at all. Also keep in mind that onductivity increases with temperature. There are some steps you can take to deal with high crude oil conductivity but I won't go into them here.
If you don't get satisfactory answers from your desalter manufacturer, I may at least be able to help with how to manage your desalter operation on a heavier/more conductive crude even I can't predict exact transformer limits.