Study On Smoldering Treatment Technology Of Oily Sludge

Oily sludge is one of the toxic and harmful solid wastes produced in the production process of the petrochemical industry.It is a mixture of various petroleum hydrocarbons,water,solid particles and harmful microorganisms.Due to its complex composition and difficult degradation,effective treatment of oily sludge has gradually become the focus of attention in recent years.The traditional treatment methods generally have the problems of high cost,complex process and complicated process.Smoldering is a new treatment technology in recent years,which can make up for the defects of traditional treatment technology.Based on the smoldering principle,this study took oily sludge from Huabei Oilfield as the representative target pollutant,and carried out a series of research.In this paper,the self-made smoldering equipment was used to control the proportion of oily sludge and soil in a proper proportion,then the smoldering experiment of oily sludge was successfully carried out and the contaminated soil contaminated with petroleum hydrocarbons was repaired.At the same time,the effects of key parameters such as oil content,water content,aeration rate,medium particle size and soil biomass were studied.In the experiment,by analyzing the changes in oil content before and after treatment,the temperature changes during the smoldering process,and the changes in tail gas,the applicable scope and optimal conditions of the smoldering treatment technology to treat the oily sludge were determined.The study found that in the range of oil content of 6%to 18%and water content of 0%to 12%,the air flux is maintained between 0.796 and 6.368 cm/s,and oily sludge can successfully ignite and achieve self-sustained combustion.Then,the degradation efficiency of petroleum hydrocarbon can reach 99%.The experimental results show that when the oil content decreases from 18%to 6%and the aeration rate increases from 0.796 cm/s to 6.368 cm/s,the ratio of CO₂ and CO in the exhaust gas increases from 2.3 and 2.6 to 5.0 and 3.6 respectively,and the complete combustion degree of oily sludge increases gradually;The average smoldering temperature of oily sludge increases from 443.8℃to 539.2℃when the medium particle size decreases from2.000～4.000 mm to 0.000～0.002 mm.In addition,the results of TG-DSC and elemental analysis of oily sludge show that when the oil content is less than 12%,the smoldering peak temperature does not reach the decomposition temperature of the mineral salt,which can effectively reduce the amounts of harmful gases such as SO_X and NO_X.Finally,based on the smoldering model of nonaqueous liquid in porous media,the smoldering model of oily sludge is further explored.The fitting data shows that the calibration parameter a of the model is 68.5,thus the smoldering speed expression suitable for oily sludge in Huabei Oilfield is obtained,which provides technical guidance for on-site treatment of oily sludge.Compared with incineration treatment technology,smoldering can effectively overcome the shortcomings of adding combustion supporting agent and difficult temperature control in the process of incineration treatment,and successfully reduce the treatment cost and risk.Compared with other treatment technologies,smoldering can achieve on-site treatment of oily sludge with low transportation cost and strong operability.Therefore,smoldering can be used as a potential new technology for on-site reduction of oily sludge.