Q & A > Question Details
Question is based on Desalter operation.
1. What can be possible reasons of mud in brine but no traces of oil during normal desalter operation? Is desalter paramters temperature, pressure and mixing delta P plays any role in it?
2. What is the role of Pressure and Temperature in desalter operation?
3. On what basis, Transformer KV setting to be changed in desalter?
4. What is the role of Mixing Valve DP in desalter operation and when does it require to be changed?
11/10/2016 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Solids that do not settle out in tankage will tend to settle out in the desalter, and is blown out of the bottom periodically. The brine is removed at an elevation above the mud level. Usually, there is good separation between the brine (water) and the mud. Maybe more frequent mud removal is needed.
A delicate balance is attempted between the extent of mixing, as influenced by the mixing valve delta P, settling time and the strength of the electric field, which is set by the transformer capacity. Based on pilot plant and field data, the desalter licensor is knowledgeable in specifying the equipment sizing and operating variables, including temperature, for a given crude or crude mix. Some crudes have a higher conductivity than others, affecting the transformer size required. The other variable is the amount of water injected. The pressure is selected to keep the oil a liquid at the selected operating temperature.
10/10/2016 A: Prabu Natarajan, Natco Uk Ltd, prabunatarajanuk@yahoo.com
1. Mud in the brine indicates that the mud is not completely in solid sate and thus not removed by separators upstream. Mud is easily dissolved in water rather oil. As components of mud might not be oil wetted and thus no traces of oil. Mix valves might play a significant role in dispersing the mud in the liquid form if it mixes the fluid aggressively. Pressure and temp doesn't play a lead role however keeping the mud in suspension or in solid form could be.
2. Pressure in the desalter keeps the fluid inside the desalter in liquid form. Reduction in pressure might force teh liquid to flash which will burn the PTFE internals inside. Higher the temp, lower the viscosity and thus increasing the temp to an optimum level will increase the settling rate of water droplets from oil feed.
3. Transformer KV is selected based on the power required to bring the water droplets together but not split. Based on the conductivity of the fluid, optimum KV will be selected. no one size fits all.
4. Mixing valve is used to mix fresh or less saline water with the wet crude entering the desalter/dehydrator. Having the water droplets at an even size improves desalter performance which can be achieved by choosing the right mix valve. Also mix valve should not over do its duty by creating stable emulsions as it will be difficult to separate even in the pro.water treatment system.