Study On Demulsification And Coalescence Technology Of Oily Wastewater From Coking Plant In Petroleum Processing

Due to the high oil content,the operation stability of the delayed coking plant will be deteriorated and the long-term operation of the unit will be greatly affected.The traditional wastewater treatment method can not meet the existing environmental protection requirements due to the large energy consumption and low efficiency.The preliminary synthesized organic coalescence materials are not good enough to remove the emulsified oil to the appropriate concentration of environmental protection requirements.Therefore,it is necessary to study the mechanism of coalescence,develop high-performance energy-saving and environmental protection oil removal technology,explore new modified coalescence materials,improve coalescence process conditions,and improve coalescence oil removal efficiency.This is of great significance for petrochemical enterprises to treat oily wastewater and meet the requirements of green environmental protection processing.In this paper,several kinds of oil-bearing or sulfur-containing sewage,such as coking vent tower,coking fractionation tower and stripping raw material tower,are used to conduct demulsification and oil removal experiments with demulsifiers 2W30,2W48,2W801 and L-S.It is found that the composite demulsifier L-S has more efficient and broader demulsification advantages.Compared with the hydrophilic stainless steel coalescing material,the hydrophobic polytetrafluoroethylene(PTFE)coalescing material can improve the oil removal efficiency by more than 20%at the flow rate of 60 L/h and 70 L/h.Without adding demulsifier,the oil removal rate of PTFE filler is always higher than 64%in 10 days continuous feeding experiment,and the oil content is always lower than 180 mg/L after dehydration,which keeps a certain stability.After adding proper demulsifier and standing for 20 minutes,the oil content of the final effluent after comprehensive treatment can reach 93.5 mg/L,which is lower than 100 mg/L required by the enterprise.It has a wide prospect in practical industrial application.In order to further improve the oil removal effect,the superhydrophobic modification was further explored.The modified silica nanoparticles modified by Amino-propyl-triethoxysilane(KH550)were grafted on the activated PTFE surface with glycidyl methacrylate(GMA)as the intermediate to form a superhydrophobic layer,and a modified coalescence material with high efficiency of oil removal was prepared.It is found that the surface roughness of PTFE is greatly improved by the introduction of SiO2,and the surface of SiO2 is rich in groups.As a results,the modified PTFE has excellent acid and alkali resistance as well as salt resistance.The oil removal efficiency of prepared material fluctuates between 72.5%and 69.7%in 15 cycle experiments,and the oil content in the effluent is between 137-151.5 mg/L,maintaining a certain stability.