Study On Wet Air Oxidation Of Oily Sludge

Composition of oily sludge is complex, which contains large amounts of residual oil andbenzene, phenol, anthracene, pyrene and other foul-smelling toxic substances, PCBs, dioxins,radioactive elements and other refractory toxic substance. If not addressed, it will seriouslypollute the environment when it is directly discharged. Traditional biotechnology orincineration of the organic matter has low efficiency and poor treatment effect, and thus, anenvironmental problem troubled the petroleum and petrochemical industry. In this paper, weconsider oily sludge as the research object, using the wet oxidation to treat oily sludge forstudying reaction characteristics of biodegradation. It will provide a theoretical basis for oilysludge treatment.The main operating conditions such as reaction temperature, initial COD of oily sludge,reaction time and other factors on the treatment effect by wet oxidation of oily sludge isstudied. Under the condition of adequate oxygen, wet oxidation of oily sludge has goodtreatment effect over a wide concentration range. The best reaction conditions are thatreaction temperature is330°C, pressure is12MPa, oxygen excess is0.8, initial COD of oilysludge is20000mg/L and reaction time is9min. COD removal rate is88.4%. Biodegradabilityof liduid effluents was improved obviously after oily sludge treatment by wet air oxidation.92%of COD removal is reached at reaction temperatures of330°C after9min. Theorthogonal experiment results show that reaction temperature is the best key factor affectingthe efficiency. Biodegradability of liduid effluents can be better with the rise of temperature.When the temperature is330°C, BOD5/COD is greater than0.45and biodegradability is thebest at this point.Catalytic wet air oxidation process improves the treatment effect under a relatively mildcondition. It is found that alkaline and two types of transition metal ion catalysts have goodcatalytic impact on wet air oxidation of oily sludge. The results showed that adding Na₂CO₃and NaHCO₃is propitious to COD removal from oily sludge by wet air oxidation. AddingNaHCO₃is superior to that of Na₂CO₃. Optimal concentration of NaHCO₃is200mg/L. TheCOD removal reaches a maximum of97.7%at this time.Metal ions catalysts show asignificant activity during wet air oxidation of oily sludge. The overall order of catalyticactivity of transitional metal salts is: FeCl3> NiCl2> MnCl2. COD removal increases as thereaction time increases at the presence of Fe³⁺and Ni²⁺. The COD removal reaches99.7%and97.8%after9min with FeCl3and NiCl2catalyst, respectively.