The re-purification process is a simple regeneration method with the main purpose of dehydration, including deodorization and de-dissolving.

The re-purification process for the purpose of dehydration is generally to first heat the waste oil to an appropriate temperature, and then either settle or centrifuge or filter, or combine two of the three separation means, or even use three in combination. For example, a patented technology uses warmed vertical tank settling to precipitate sludge (including water) and then circulates in a heated horizontal tank to re-purify the waste oil.

There is also a popular type of dehydration process that combines vacuum hot flashing with rapid de-watering and filtration, and many of these devices are used in factories, many of which are stereotyped and patented. For example, devices mounted on a movable frame include pumps, filters, heat ex-changers, and vacuum evaporators.

There is one such flash filtration dewatering miscellaneous device, including a wire mesh filter, a vacuum evaporation can, an electric heater, and a pump. The waste oil is first filtered through a wire mesh filter (filter area of not less than 2.6 m2), then heated to 60-83 ° C, sprayed into a vacuum evaporation tank through an atomizing nozzle, and evaporated water and light hydrocarbons and other volatiles. The atomizing nozzle is specially made and has many small holes with a diameter of about 10 m. The dehydrated oil is then filtered through a wire mesh and recycled back to the lubricating oil storage tank.

Many countries have waste oil recycling units installed on trucks. The United States has a species. A re-purification device installed on a medium-sized truck. The power of the device is supplied by an automobile engine. The device includes a waste oil tank, a purified oil tank, a centrifuge, a filter, a vacuum degassing pump, a water washing device, and a device for continuously supplementing additives.

There is also a waste oil re-purification device which removes large water droplets and machine impurities by centrifugation and then thoroughly dehydrates by a vacuum flasher.

As for degassing and deodorization, a method of vacuum stripping or vacuum circulation is often employed.

For the waste oil which is difficult to be effective by sedimentation and centrifugation alone, the dehydration can be settled or centrifuged by adding a flocculant, and this method is now widely used in the re-purification process.