Method and Device for Enhanced Oil-Water Separation and Desalination in Cold Low-Pressure Separator

A method for enhanced oil-water separation and desalination in a cold low-pressure separator, comprising the steps of

• 1) mixing water-containing oil with desalted water at entrance to transfer salts and hydrogen sulfide in the oil to the desalted water, and flowing the resultant oil-water mixture into a T-shaped liquid-gas separator to rapidly separate gas from the oil-water mixture via flash evaporation, wherein the oil has a pressure of 0.6-4.5 MPa and a temperature of 20-90° C. at the entrance, and the desalted water is injected in such a rate that the injected desalted water accounts for 0-1% of the water-containing oil by volume;
• 2) subjecting the oil-water mixture to secondary washing by injected water, flow conditioning and preliminary separation to separate water having a droplet size over 30 μm, wherein a hydrophilic droplet agglomeration module and a CPI fast separation module are used in the preliminary separation, the hydrophilic droplet agglomeration module is adopted to rapidly agglomerate the water droplets scattering in oil, and the CPI fast separation module performs rapid oil-water separation, the separated water is automatically discharged from bottom by an oil-water interface level controller, or alternatively enters a deep separation chamber through ports at both sides of a partition while oil with a trace of water flows through the partition for next processing step, wherein the water injected in the secondary washing accounts for 0-0.5% of the oil-water mixture, the conditioned oil-water mixture flows in a flow velocity of 0.005-0.05 m/s, and space between each two adjacent corrugated plates in the CPI module is 5-18 mm;
• and
• 3) subjecting the oil with a trace of water to gravity settling followed by a conjugated fiber water removal module containing hydrophilic fibers and oleophilic fibers to separate water droplets having a size of 3-30 μm, automatically discharging the resultant oil by a liquid level controller while at the same time subjecting the separated water to a conjugated fiber oil removal module containing hydrophilic fibers and oleophilic fibers to obtain water containing less than 100 mg/L of oil and then automatically discharging the resultant water by an oil-water interface level controller, wherein water droplets with larger size are settled down during the gravity settling to bottom and then into a water bag;
• wherein the amount of the hydrophilic fibers is 5 to 15% of that of the oleophilic fibers in the conjugated fiber water removal module;
• the amount of the oleophilic fibers is 10 to 20% of that of the hydrophilic fibers in the conjugated fiber oil removal module.