Crude oil contains many contaminants, such as inorganic salts, sand, drilling mud, suspended solids, polymer, corrosion byproducts, and more. These contaminants need to be removed to refine the oil into a finished product. The process is called separation. Desalting is a part of the refining process, in which, salts and water are removed from the crude oil prior to distillation. Some of the reasons why crude oil desalting is necessary are:
- It increases crude throughput
- There is less scaling, plugging, coking of the heat exchanger and furnace tubes
- Corrosion in the exchanger, fractionators, pipelines, etc is minimal
- Less erosion by solids in the exchanger, control valves, furnace, pumps
How crude oil is desalted
- Crude oil containing sediments and produced salty water is passed through the cold preheat train and then pumped to the desalters (electrostatic coalescers) by crude charge pumps.
- The recycled water or wash water from the desalters is then injected in the crude oil line and the formed fluid enters the static mixer. This maximizes the interfacial surface area for optimal contact between oil and recycled water. Mixers are installed upstream the emulsifying devices in order to improve the contact even more.
- The oil/water mixture is homogeneously emulsified in a “valve” like device. The emulsion then enters the desalter where it gets separated into two phases by electrostatic coalescence induced by the polarization effect. The polarization of water droplets pulls them out from oil-water emulsion phase and as salt is dissolved in these water droplets, it also gets separated along the way.
A desalting unit can be designed with a single or two stages. In refineries, the two stages desalting system is usually applied, that consists of 2 desalters.
So now you know the way of crude oil refinery.
Desalters LLC is one of the leading desalter supply and service companies in Conroe, Texas. Contact us for replacement parts for all types of Desalters.