June 14, 2021
The traditional waste lubricating oil recycling technology is distillation-sulfuric acid-white clay refining process. Its biggest disadvantage is that the waste generated in the process easily pollutes the environment. Many oil companies are currently researching and developing new waste oil recovery technologies. The main regeneration processes so far are: Acid-Clay Refining Type, Distillation-Extraction-Clay Refining Type, Distillation-Solvent Refining-Hydrorefining Type, Demetallization-Fixed Bed Hydrorefining Type and Distillation-Hydrorefining Type, Catalytic Cracking, high temperature deep thermal cracking, membrane separation, molecular, distillation, etc.
(1) Acid-white clay refining type uses sulfuric acid to refine the waste lubricating oil. After the acid residue is discharged, the white clay is used for refining. It has the advantages of low investment, strong adaptability and can handle small batches of waste oil, but after the waste oil is regenerated The formation of difficult-to-treat acid residue, waste white clay, waste water and a large amount of acid gas sulfur dioxide endangers the health of employees, corrodes equipment, and pollutes the environment.
(2) Distillation-extraction-clay refining type is to first remove the hydrogen components in the waste oil by distillation, and then use solvent and clay for refining. It is characterized by acid-free refining and there is no acid residue treatment problem. Ethanol is used as a solvent, and its extraction ability is weak, so this process is not widely used.
(3) Distillation-solvent refining-hydrorefining type is to first remove the water and hydrogen components in the waste oil through atmospheric distillation, and then perform the first propane extraction to remove sludge, oxides and some additives. The oil from which propane is removed is firstly distilled under reduced pressure, and then propane is extracted to remove residual additives. Finally, all the lubricating oil fractions are sent to hydrofining. The characteristics of this process are that it will not form secondary pollution, and its adaptability to waste oil raw materials and the quality of regenerated oil are better than other processes. However, the use of hydrogen in the reaction process increases the risk of the process, large investment, and operating conditions. Strict and demanding for operators.
(4) Demetallization-fixed-bed hydrorefining type is to first heat the waste oil to make it contact with ammonium sulfate or ammonium bisulfate aqueous solution in the reactor to produce metal compounds that can be precipitated. After precipitation and stratification, the metal compounds stay in In the water phase, the water layer is filtered to remove the sediment, and the filtrate is recycled. The oil layer is flashed to separate the gasoline layer and the water layer. The flashed oil is adsorbed to remove polar compounds, and then subjected to hydrotreating to further remove residual polar compounds and unsaturated substances. The characteristic of the process is that the water in the system can be recycled, the reaction conditions are mild, and the cracking reaction can be prevented. However, there are still disadvantages of the hydrogenation process, such as high risk and harsh operating conditions.
(5) Distillation-hydrorefining type is heating and distilling waste oil to separate lubricating oil components and residues, and then the distillate is hydrotreated in a series of molybdenum nickel catalyst fixed bed reactors. The characteristics of this process are no waste disposal problems, high yield, good product quality, but high raw material quality requirements. When the metal content of the raw materials is high, complex pretreatments (demetalization, adsorption, etc.) are required.
(6) The waste oil catalytic cracking technology is to add a catalyst to the reactor to heat up, so that the waste lubricating oil is first cracked into a mixture, and then through the processes of rectification separation, decolorization, etc., a qualified diesel product is finally obtained. This method has the advantages of low investment and easy operation, but the reaction temperature is about 350-450℃, and some non-condensable gases will be produced during the cracking process. The current treatment method for this gas is only incineration, and the toxic and harmful gases produced during the incineration process can only be After the activated carbon is adsorbed, it is directly discharged, and the discharged tail gas still contains a large amount of toxic and harmful gases that cannot be absorbed and treated, causing secondary environmental pollution.
(7) The deep thermal cracking process of waste mineral oil vaporizes all the fuel oil in the waste mineral oil through a high temperature reaction system, so that the aromatic hydrocarbons and polycyclic aromatic hydrocarbons in the waste mineral oil are concentrated to form pitch. The vaporized fuel oil enters the fractionation tower and undergoes fractionation in the tower. After cooling, the top oil and gas are separated into gas and fuel oil. After deliquoring, the gas enters the heating furnace as the heating furnace fuel, and the fuel oil is sent out of the device into the storage tank. The advantage of this project is that the residual oil after high-temperature thermal cracking is directly used to produce asphalt, and there is no solid waste. The disadvantage is that the process is complicated, the reaction temperature is higher than 400 ℃, and the proportion of waste mineral oil in the reaction raw materials is only 30%. The other 70% is clearing oil sludge.
(8) The current membrane separation waste oil regeneration process technology mainly comes from the vibrating membrane technology of Hong Kong Zhengchang Group and the nanofiltration membrane technology of Shenzhen Senkeyan Technology Co., Ltd. Although the two membrane separation technologies are simple in process, low in operating temperature, and low in operating cost, in terms of domestic use, the technology is immature, has a small application range, has a very large investment, has a short membrane life, high replacement cost, The core component of Vibration Membrane or Nanofiltration Membrane is its monopoly sales.
(9) The molecular distillation regenerated base oil process mainly relies on the difference in the mean free path of molecular motion of different substances to achieve separation. When the waste lubricating oil flows along the heating plate and is heated, the light and heavy molecules will escape from the liquid surface and enter the gas phase. Because the free paths of the light and heavy molecules are different, the molecules move at different distances after escaping from the liquid surface. The molecules that reach the condensation plate are condensed and discharged, while the heavy molecules cannot reach the condensation plate and are discharged along the mixed liquid. In this way, the base oil can be separated from the waste lubricating oil, and then refined by means of decolorization, filtration, etc., to produce qualified regenerated base oil.
