Study On Demetal Technology Of Used Lubricating Oil

As a renewable industrial hazardous waste,the development trend of waste lubricating oil regeneration process was the hydrogenation process with low pollution degree,while the waste oil hydrogenation process in our country has not been popularized for a long time.The main reason was lack of effective pretreatment process for removing metal from waste lubricating oil.In this paper,two kinds of waste lubricating oil from Jiangsu and Zhejiang were used as raw materials,the metal in the waste lubricating oil was removed by flocculation,heat treatment and low temperature chemical method,in addition,the cause of coking in the heat treatment reactor and the principle of demetal of low temperature chemical method were preliminarily investigated.A kind of flocculant which was developed independently in laboratory was used to study its demetal effect on waste lubricating oil.The results showed that under the better flocculation conditions,the color of the regenerated lubricating oildecreased from 22 to 9,the transmittance increased from 81.7%to 94.8%,the total metal content of the waste lubricating oil after flocculation treatment has been less than 50?g·g^-1,and the removal rate of metal has reached over 98%.Compared with several commonly used alkaline flocculants in the industry,the flocculation agent has good demetallization effect and no bumping phenomenon occured in the experiment.The heat treatment method was used to remove the metal from the waste lubricating oil.The test results in the autoclave showed that under the optimized operating conditions,the ash content of waste lubricating oil was reduced from 0.93wt%to 0.23wt%,and the removal rate of metal reached over 85%.Based on the heat treatment conditions selected by the autoclave,using better operating conditions on 3L continuous test equipment,the metal removal rate of waste lubricating oil reached more than 88%,and the product had a high slag removal rate and good physical and chemical properties.However,there was a problem of coking at the bottom of the reactor in the pilot test of heat treatment.Through the analysis of the degradation law of impurities and the comparison of coke and centrifuge residue during the heat treatment process,it was found that the coking cause of the heat treatment pilot plant was the impurities that were removed by the heat treatment,gradually deposited on the reactor wall,and the coke was formed after a long period of high temperature sintering.A water-soluble phosphorouschemical agent was screened,and the effect of metal removal from waste lubricating oil was examined at a lower reaction temperature.The experimental results showed that when thechemical agent content was 1wt%,the reaction temperature was 160?,the total removal rate of metal in waste lubricating oil exceeded 95%.In addition,there was no coking in the reactor.The analysis of the elements,functional groups and phases of the reaction residue showed that the principle of demetal for low temperature chemical method wasthe metal in the lubricating oil additive was hydrophilic,which was easy to enter the water phase,and reacted withphosphorous chemical agent in aqueous phase,formed phosphate deposits which were neither soluble in oil nor soluble in water,to achieve the effect of removing metals.