Abstract: A process for significantly decreasing the acid sludge settling time in waste oil recovery processes comprising the steps of heating used oil to a high temperature above 700 degrees Fahrenheit, cooling the heated oil, adding an oxidizing agent to the oil, allowing the acid sludge to settle within a period of approximately 24 to 72 hours, separating the acid-sludge-free oil from the acid sludge which settles out of solution as a result of addition of the oxidizing agent, and adding a polishing agent and separating the re-refined oil from the spent polishing agent. The process produces a high quality re-refined oil rapidly and economically.

Abstract: A process for converting the acid sludge produced by waste oil refineries into an intermediate sludge which can be used in the production of either soft, un-oxidized asphalt or hard, oxidized asphalt, and a process for converting the intermediate sludge into soft, un-oxidized asphalt. The process comprises contacting the entire surface area of acid sludge with a pH altering agent such as water or a solid base such as lime, caustic soda, or soda ash, to convert the acid sludge into a layer of liquid and a layer of intermediate sludge. Then the liquid layer is separated from the intermediate sludge layer, thereby producing an intermediate sludge having properties which make it suitable for use in asphalt production. To produce soft, un-oxidized asphalt, the intermediate sludge is heated to a temperature above the boiling point of water and held at that temperature long enough to remove all the aqueous components to create un-oxidized asphalt.

Abstract: A process for converting the acid sludge produced by waste oil refineries into an acid sludge intermediary which can be used in the production of asphaltic mixtures. The process includes contacting the entire surface area of acid sludge with a pH altering agent such as an aqueous inorganic liquid, and separating the liquid layer from the sludge layer, thereby producing an intermediate sludge having properties which make it suitable for use in asphalt production.