A method is provided for reprocessing a petroleum-based waste oil feedstock into diesel fuel. The method includes forming a treated feedstock by (a) filtering the feedstock, thereby removing solids and metals from the feedstock, and (b) dehydrating the feedstock; vaporizing the treated feedstock to produce an oil vapor; passing the oil vapor through at least one catalyst bed and subsequently through a cooler, thereby converting the oil vapor to a hydrocarbon liquid product with a diesel product boiling point range; and removing contaminants from the hydrocarbon liquid product, wherein the contaminants are selected from the group consisting of particulates and color precursors.

A method for the regeneration of used lubricating oils to produce lubricant base oils includes the steps of (a) removing resin and impurities by distillation, (b) catalytic oxidation treatment and (c) adsorption process. The method can efficiently reduce the color, metal ions, and sulfur content under mild reaction conditions at low cost and obtain high yield of regenerated oil above 85 wt. %.

A method for the regeneration of used lubricating oils to produce lubricant base oils includes the steps of (a) removing resin and impurities by distillation, (b) catalytic oxidation treatment and (c) adsorption process. The method can efficiently reduce the color, metal ions, and sulfur content under mild reaction conditions at low cost and obtain high yield of regenerated oil above 85 wt. %.

A method for continuous purification of motor lubricant oil includes circulating lubricant oil between a motor lubricant oil tank and a motor; transporting contaminated lubricant oil from the motor lubricant oil tank in a cleaning loop. The transport in the cleaning loop includes adding at least one liquid separation aid to contaminated lubricant oil; supplying contaminated lubricant oil to a three-phase centrifugal separator; continuously separating contaminants from the lubricant oil in the separator and continuously discharging a first liquid phase including purified lubricant oil from a liquid light phase outlet of the separator, continuously discharging a second liquid phase including solid contaminants from a liquid heavy phase outlet of the separator and continuously discharging a sludge phase from a sludge outlet by the aid of a conveyor screw of the three-phase separator. The method further includes transporting the first liquid phase including purified oil back to the lubricant oil tank. The present invention further provides a system for carrying out the method.

A method for continuous purification of motor lubricant oil includes circulating lubricant oil between a motor lubricant oil tank and a motor; transporting contaminated lubricant oil from the motor lubricant oil tank in a cleaning loop. The transport in the cleaning loop includes adding at least one liquid separation aid to contaminated lubricant oil; supplying contaminated lubricant oil to a three-phase centrifugal separator; continuously separating contaminants from the lubricant oil in the separator and continuously discharging a first liquid phase including purified lubricant oil from a liquid light phase outlet of the separator, continuously discharging a second liquid phase including solid contaminants from a liquid heavy phase outlet of the separator and continuously discharging a sludge phase from a sludge outlet by the aid of a conveyor screw of the three-phase separator. The method further includes transporting the first liquid phase including purified oil back to the lubricant oil tank. The present invention further provides a system for carrying out the method.

A method for re-refining used oils comprises contacting feedstock comprising purified used oil with extraction solvent to perform continuous liquid-liquid solvent extraction, to produce an extract stream comprising the extraction solvent and an extract dissolved in the extraction solvent. The feedstock and the extraction solvent are agitated by a variable speed agitator during the solvent extraction at a selected agitation speed. The extract is separated from the extraction solvent and subjected to a continuous flow liquid phase hydrogenation treatment to produce an oil product. A system for performing the method includes a purification unit for purifying the used oil; an extraction column for extracting the extract from the feedstock; and a continuous flow liquid phase hydrogenation unit. The extraction column comprises an agitator configured to agitate the feedstock and the extraction solvent flowing through the extraction column at a variable agitation speed.

A method for re-refining used oils comprises contacting feedstock comprising purified used oil with extraction solvent to perform continuous liquid-liquid solvent extraction, to produce an extract stream comprising the extraction solvent and an extract dissolved in the extraction solvent. The feedstock and the extraction solvent are agitated by a variable speed agitator during the solvent extraction at a selected agitation speed. The extract is separated from the extraction solvent and subjected to a continuous flow liquid phase hydrogenation treatment to produce an oil product. A system for performing the method includes a purification unit for purifying the used oil; an extraction column for extracting the extract from the feedstock; and a continuous flow liquid phase hydrogenation unit. The extraction column comprises an agitator configured to agitate the feedstock and the extraction solvent flowing through the extraction column at a variable agitation speed.

The present invention provides method for separating contaminants from a liquid mixture comprising the steps of a) providing a feed of said liquid mixture to be purified, b) adding a separation aid to the liquid mixture to be purified, wherein said separation aid is capable of binding said contaminants and c) supplying a flow of compressed air into said feed after step b) has been performed to provide a feed comprising air. The method further comprises steps d) removing air from said feed comprising air to provide a deaerated feed; and e) supplying said deaerated feed to a separator, and f) separating a phase comprising contaminants and said separation aid from said liquid mixture in said separator, wherein the separation aid added in step b) is insoluble in said liquid mixture at the separation conditions in step f). The present invention further provides a system for separating contaminants from a liquid mixture.

The present invention provides method for separating contaminants from a liquid mixture comprising the steps of a) providing a feed of said liquid mixture to be purified, b) adding a separation aid to the liquid mixture to be purified, wherein said separation aid is capable of binding said contaminants and c) supplying a flow of compressed air into said feed after step b) has been performed to provide a feed comprising air. The method further comprises steps d) removing air from said feed comprising air to provide a deaerated feed; and e) supplying said deaerated feed to a separator, and f) separating a phase comprising contaminants and said separation aid from said liquid mixture in said separator, wherein the separation aid added in step b) is insoluble in said liquid mixture at the separation conditions in step f). The present invention further provides a system for separating contaminants from a liquid mixture.

A method for re-refining used oils comprises contacting feedstock comprising purified used oil with extraction solvent to perform continuous liquid-liquid solvent extraction, to produce an extract stream comprising the extraction solvent and an extract dissolved in the extraction solvent. The feedstock and the extraction solvent are agitated by a variable speed agitator during the solvent extraction at a selected agitation speed. The extract is separated from the extraction solvent and subjected to a continuous flow liquid phase hydrogenation treatment to produce an oil product. A system for performing the method includes a purification unit for purifying the used oil; an extraction column for extracting the extract from the feedstock; and a continuous flow liquid phase hydrogenation unit. The extraction column comprises an agitator configured to agitate the feedstock and the extraction solvent flowing through the extraction column at a variable agitation speed.