Structure Optimization And Performance Research Of DT-LHS30 Hydrocyclone

Crude oil needs to go through the process of electric desalting and dehydration before entering the atmospheric and vacuum distillation unit,and the sewage produced after electric desalting accounts for about 3%of the total sewage of the refinery.In recent years,with the aggravation of the problem of heavy and inferior crude oil,the water injection and pharmaceutical dosage are increasing in each oilfield in order to improve the recovery rate,which makes the water quality deterioration of electric desalting wastewater more and more serious.Due to the advantages of good flow field symmetry,flow stability,simple structure and easy operation,the double-tangential inlet hydrocyclone has been paid more and more attention.Aiming at the problem that the electric desalting wastewater in Shengli Refinery is rich in oil and difficult to meet the discharge standard,the optimized structure of DT-LHS30hydrocyclone is obtained through the combination of experimental optimization and numerical simulation in order to reach the discharge standard of electric desalting wastewater.First of all,the preliminary physical properties of electric desalting wastewater were analyzed,including the viscosity,density and four components of oil phase.According to the basic physical properties of sewage,the structure optimization scope of DT-LHS30hydrocyclone was determined,and a small experimental platform was built to explore the influence of different structures on the oil removal performance.On this basis,the structure optimization of double-tangential hydrocyclone was carried out.The optimized single pipe structure was as follows:the cone angle is 4°,the overflow diameter is 4 mm,the tail pipe length is 300 mm,the tail pipe diameter is 12 mm,the insertion depth of overflow port is 15mm.Based on the optimized structure of single pipe,the experimental study of two-stage series sewage oil removal process was carried out.The results show that the total oil removal efficiency of the two-stage series process can reach 99.38%when the inlet flow is 1.5 m~3/h,the primary overflow ratio is 10%,the secondary overflow ratio is 8%,the temperature is50℃and the demulsifier concentration is 20 mg/L.Under this condition,the oil content in outlet water is only 32.7 mg/L,and the total pressure drop is 0.14 MPa.Secondly,under the same operation parameters and physical parameters,the oil removal performance of D30 axial-flow hydrocyclone with the same size as the optimal structure was compared.The results show that the axial-flow hydrocyclone has better performance in treating oily wastewater with low temperature and high viscosity,but needs to add higher concentration of demulsifier and consume more energy.Considering the economy,for the electric desalting wastewater with general temperature of 50℃and oil concentration of 5000mg/L,when the inlet flow rate is 1.5 m~3/h,overflow ratio is 10%,demulsifier concentration is20 mg/L,the results show that the oil removal efficiency of DT-LHS30 hydrocyclone can reach 91.37%,and the pressure drop is 0.099 MPa,the effect is better than axial-flow hydrocyclone.Finally,the numerical simulation of double-tangential/axial-flow hydrocyclone under basic conditions was carried out,and the speed,pressure,turbulence state and volume distribution of oil phase under the conditions of 0～1.8 m~3/h inlet flow and 10%optimum overflow ratio were mainly analyzed,and the internal flow state of hydrocyclone under basic conditions was explored.The simulation results show that the tangential velocity in the separation area of the double-tangential hydrocyclone is higher than that of the axial flow,while the axial velocity is lower than that of the axial flow.Therefore,the separation power of the double-tangential hydrocyclone is greater,the separation time is longer and the oil removal efficiency is higher.The pressure contour diagram also shows that the pressure drop of the double-tangential hydrocyclone is lower.Comparing the simulated values of oil removal efficiency and pressure drop with the experimental results,it is found that the oil removal efficiency and pressure drop trend are basically the same in the range of 0～1.8 m~3/h with the relative error within 10%～15%.The optimum efficiency of DT-LHS30 hydrocyclone proposed in this paper for deoiling of electro-desalination wastewater is above 90%with pressure drop not exceeding 0.1 MPa;the two-stage series deoiling process realizes oil concentration in effluent less than 50 mg/L,the total oil removal efficiency exceeds 99%,which not only minimizes the dosage of agent,but also guarantees the sewage discharge up to the standard,realizes the environmental protection,and has very important practical significance for purifying the water quality of electric desalting wastewater from refineries.