Study On Crude Oil Removal And Recovery Of Oily Sludge

A large amount of oily sludge is generated during the oil field exploitation,which is mainly composed of strata sand,crude oil,colloid,chemical additives,and water.Oily sludge from oil fields has complex components and is difficult to be treated.Studying the treatment methods and technologies of oily sludge is of important practical significance.In this work,the deoiling performance of the chemical cleaning method was investigated for the oily sludge produced by Gudong oil production plant in Shengli oilfield,especially the feasibility of surfactant-free microemulsions(SFMEs)for deoiling was explored,and the relevant mechanisms were discussed.It is expected to provide useful information for the treatment of oily sludge.The main research contents and conclusions of this thesis are as follows:(1)Characterization of oily sludgeThe composition of the oily sludge,the viscosity and four component contents of its crude oil,and the composition and particle sizes of its solids were determined,to provide data support for subsequent experiments.The results show that the contents of water,crude oil,and solid of the oily sludge are about 52.0%,37.2%,and 10.8%,respectively.The density and viscosity of its crude oil at 50℃ are about 1.01 g/cm3 and 3.40 Pa·s,respectively.With an increase in temperature(from 20 to 60℃),the viscosity of the crude oil significantly decreases(from～44.2 to 1.47 Pa·s).The contents of four components are:Saturated Hydrocarbons～36.36%,Aromatic Hydrocarbons～21.24%,Resins～19.35%,and Asphaltenes～22.87%.Solid particles of the oily sludge mainly contain quartz,barite and pearl mica,which are amorphous particles with an average size of～12.4 μm。(2)Chemical cleaning oily sludgeDifferent types of 22 surfactants and sodium silicate(Na2SiO3)were chosen,to determine the deoiling efficiencies of single-component and multicomponent for the oily sludge.The effects of various factors such as detergent concentration,liquid/solid ratio,temperature,time,and stirring speed on the deoiling efficiencies were investigated.The results show that a good deoiling efficiency can be obtained by using Na2SiO3 pretreatment followed by surfactant cleaning.The deoiling efficiencies of nonionic,anionic,amphoteric,and cationic surfactants tend to decrease.The combination of a single surfactant and Na2SiO3 can significantly enhance the deoiling efficiency.Under experimental conditions,the combination of Na2SiO3 with NP-10,OP-10,Tween-80,or Brij-30 can reduce the residual oil rate of the treated solids to be less than 1%.The removed crude oil is easy to recover,and the cleaning liquid can be recycled.(3)Treatment of oily sludge with surfactant-free microemulsionsThe phase behavior of the ternary system of n-propanol,water,and the CO2-responsive solvent N,N-dimethylcyclohexylamine(DMCHA)was investigated,where DMCHA is used as the oil phase and n-propanol as the amphiphilic solvent,indicating that SFMEs can be formed.The CO2-responsive behavior of the SFMEs was determined.The deoiling efficiency of the SFMEs for the oily sludge and the effect of various factors on it were investigated,to evaluate their practical application prospects.The results show that the SFMEs have the oil-in-water(O/W),bicontinuous(BC),and water-in-oil(W/O)type microstructures,with the CO2-responsiveness.The three types of SFMEs all have good deoiling performance,showing an increasing tendency in the deoiling efficiency for O/W,BC,and W/O types.Their deoiling efficiency is not obviously affected by the change of deoiling conditions,such as temperature,time,stirring speed,and liquid/solid ratio,within the studied ranges.The residual oil rate of the treated solids can reach～1%.Injecting CO2 into the liquids can seperate oil-water and recover crude oil,and the water phase can be restored to SFMEs by injecting N2 and can be recycled.In addition,the deoiling performance of 12 other SFMEs were also investigated,and it was found that SFMEs containing DMCHA and N,N-dimethylethanolamine(DMEA)have higher deoiling efficiencies.After secondary cleaning,the residual oil rate of solids could be less than 1%.These results preliminarily indicate that SFMEs have application potentials in the oily sludge treatment.