Method for hydrotreating and recycling waste lubricating oil

A method for hydrotreating and recycling waste lubricating oil, comprising the steps of:

• S100) removing small-particle mechanical impurities from the waste lubricating oil with a filter;
• and separating free water and a portion of light hydrocarbons from the waste lubricating oil in a flash distillation column;
• S200) mixing a bottom product obtained from the flash distillation column in S100 with hydrogen gas and a self-sulfurizing oil-soluble transition metal catalyst;
• and pre-hydrotreating the mixture in a slurry bed hydrogenation reactor;
• S300) separating a reaction effluent obtained in S200 to obtain hydrogen-rich gas and a liquid product;
• S400) separating the liquid product obtained in S300 with two-stage hydrocyclone separators to obtain a liquid product and a tailing residue;
• allowing the tailing residue to enter a solvent recovery tower;
• and discharging a tower bottom effluent as a solid residue from the solvent recovery tower;
• S500) obtaining a slurry bed pre-hydrotreating product, which includes the liquid product from the two-stage hydrocyclone separators and a solvent from the solvent recovery tower;
• S600) mixing the slurry bed pre-hydrotreating product with hydrogen gas;
• and streaming the mixture sequentially through a hydrofining reactor, an isomerization-dewaxing reactor and a supplementary refining reactor while the mixture is caused to react in turn through contact with a hydrorefining catalyst, an isomerization-dewaxing catalyst and a supplementary refining catalyst;
• and
• S700) separating an output material in S600 to obtain a naphtha fraction, a diesel fraction and a lubricant base oil fraction, wherein:
• the waste lubricating oil enters the slurry bed hydrogenation reactor through a bottom of the slurry bed hydrogenation reactor and then flows upwards after the waste lubricating oil is mixed with the hydrogen gas and the self-sulfurizing oil-soluble transition metal catalyst in the slurry bed hydrogenation reactor;
• the self-sulfurizing oil-soluble transition metal catalyst includes one of molybdenum, nickel, iron and cobalt;
• and
• S400 further includes setting the two-stage hydrocyclone separators to operate at a temperature of 50-180° C.