A Study On The Technology Of Reducing And Recycling Oily Sludge In Steel Enterprises

The steel enterprises may produce a large amount of oily sludge in the processes of steel smelting andwastewater treatment. The sludge mainly comes from settlement tank, advection settlement tank,chemical oil separator and high-rate filter backwashing, etc.. With a complex composition, thesolid-liquid ratio of the sludge is relatively stable, so it is hard to achieve a complete settlement. makingsludge treatment very difficult without the intervention of external force. The sludge usually containschemicals such as hydrocarbons, phenols and benzenes which are highly toxic and accompanied by stench,so if it is discharged without treatment, the natural environment will be severely polluted, and largequantities of useful resources will be wasted. Therefore, searching for effective solutions to the problem ofoily sludge pollution and improving the comprehensive utilization rate of oily sludge so as to change trashinto treasure and turn harms into benefits, will undoubtedly become an important approach to explore anew prospect of Chinese steel industry and the only way to implement sustainable development strategies.In view of the current situation of great difficulties in dealing with oily sludge in the steel enterprises,the paper studies the oily sludge produced by wastewater treatment system of steelmaking and steel rollingplant of Anyang Steel Group Corporation. Based on a great quantity of domestic and foreign data, andcombined with the characteristics of oily sludge, the author of this paper carries out a research into theintegrated technology of quenching and tempering-mechanical dehydration-solvent extraction.Through a quenching and tempering experiment of the oily sludge, a quenching and temperingcompound has been discovered. With this quenching and tempering compound, the author of this paperadopts a one-factor approach to investigate the influences of experimental temperature, pH value andstirring time on the effect of quenching and tempering oily sludge. Through a series of extractionexperiments of oily sludge, the best extraction agent has been selected, and the optimum dosage has beendetermined. Then extraction effects of two types of oily sludge with different moisture content have beencompared so as to verify the results of the extraction experiments. The favorable experimental conditions of quenching and tempering-mechanical dehydration of oilysludge are as follows: PR-A which is composed of ferric chloride, cationic polyacrylamide (CPAM) andquicklime, functions as the quenching and tempering compound, the experimental temperature ranges from70℃to80℃, pH value from4.0to5.0, the stirring time is30minutes, and the mechanical dehydrationequipment is for the400kPa (absolute pressure) plate and frame filter press. Under favorable operatingconditions, the moisture content of oily sludge will decline from98.6%to70.3%, the volume will become1/17of the original sludge, thus greatly reducing the volume of oily sludge.After quenching and tempering and leaching oily sludge, the author adopts solvent extractionapproach to deal with oily sludge. The findings of the experiment show that based on the premise of theextractant selection principle, the best extraction agent is120#solvent oil, and when the ratio of extractantdosage to the quantity of oily sludge is40:1(extractant/oily sludge (V/G)), the best extraction effects wouldbe achieved. The heating value of the dry residue left after the extraction is6925kJ/kg, which means theprocessing effect is good, and the extracted oil can be used for refining oil or as fuels.The results of the experiments demonstrate that the technical route of oily sludge treatment, theintegrated technology of quenching and tempering-mechanical dehydration-solvent extraction, is feasible,because it not only achieves the goal of reducing the amount of oily sludge, but also realizes the recyclingof the oily sludge.