Research Of Pollution Characteristics And Environmental Risk On Used Mineral Oil

Used mineral oil, as one kind of hazardous wastes, is toxic and flammable; but it also has great recycling value and can be regenerated for fuel oil, base oil, ect. Precisely because of this dual attributes, most of used mineral oil is recovered illegally by small traders without business qualification and sent into the subsequent illegal or unregulated recycling link. These unscrupulous traders reap huge profits, while causing huge hazards to the ecological environment and human health. Currently, domestic studies about used mineral oil focus on its recycling technology, little concerning its generation characteristics, pollution characteristics and environmental risk during its treatment and disposal process. Therefore, it is significant to study its generation characteristics, pollution characteristics and environmental risk during its treatment and disposal process.This paper analyzes the species, generation process, generation links and generation factor of used mineral oil, analyzes the types, sources, concentration and composition of pollutant in it, and studies the migration and transformation of the pollutant during its treatment and disposal process. Combining with migration and transformation of the pollutant, this paper studies the environmental risk of treatment and disposal process of used mineral oil, building exposure scenarios and choosing simplified model.Because of the differences of generation process and work environment among different used mineral oil, the degree of loss and generation factor are significantly different. The generation factor of used white oil is maximum, about 1.0, followed by used vehicle lubricating oil, used quenching oil, used refrigerant oil and used hydraulic oil, 0.6-0.9. The factor of used antirust oil, used lubricating oil and used foundry oil is minimum, 0.1-0.3.Heavy metals in used mineral oil are mainly from the entry during the process of using(Cr, Ni, Pb and Cu) and additives(Zn, Mo and Ba), which accounted for the major part of the heavy metals. Benzene homologues(BTEX) and polycyclic aromatic hydrocarbons(PAHs) are mainly from base oil, oxidative deterioration during its using and entry of fuel oil, which has great impact on the content of BTEX and PAHs in used mineral oil.In the regeneration, heavy metals in used mineral oil all enter into the waste generating in the regeneration, most of which enter into the cracked residue, and the products oil does not contain heavy metal. In the cracking process, new BTEX and PAHs are generated because of the high temperature, and in the adsorption refining process, some of them are removed by adsorption, making the BTEX and PAHs presenting semi-finished oil> refined oil> feedstock. In incineration process of used mineral oil, heavy metal content in flue gas rises with temperature rising. BTEX(except benzene) content decreases with temperature rising, and the main reason is that the higher the temperature is, the combustion of BTEX is more complete. The content of benzene and PAHs first increases and then decrease with the temperature increasing. It is because of that benzene and PAHs can not only be decomposed, but also can be synthesized in high temperature. In different temperature, the rate of decomposition and synthesis are different and make the content of benzene and PAHs first increase and then decrease. When used mineral oil is used as fuel of boiler and spray booth, cumulative non carcinogenic risks are respectively 0.023, 0.078 and 0.050 in three different conditions and cumulative carcinogenic risks are respectively 6.50×10-6、2.55×10-5 and 2.26×10-5. So there exists human health risk when used mineral oil is used as fuel of boiler and spray booth. Cracked residue’s cumulative carcinogenic risks and cumulative non carcinogenic risks are 4.91×10-6 and 0.014 when piled in the open air, and 1.32×10-5 and 0.037 when getting into the landfill. That is to say that there exists human health risk when cracked residue piled in the open air or getting into the landfill. Used filter sand’s cumulative carcinogenic risks and cumulative non carcinogenic risks are 9.44×10-7 and 0.0044 when piled in the open air, and 1.32×10-5 and 0.037 when getting into the landfill. There does not exist human health risk when used filter sand piled in the open air, but exists when getting into the landfill.