Liquid-liquid Phase Equilibrium Research And Process Simulation Of Extraction Of Highly Concentrated Phenols From Coal Chemical Industry Wastewater With Dibutyl Ether

From the perspective of the characteristics of China's fossil energy structure,achieving clean and efficient use of coal resources is still the focus of current research work."Zero discharge"of wastewater have become an important bottleneck restricting the development of coal chemical industry.However,the key to whether coal chemical industry can achieve"zero discharge"is wastewater treatment and reuse.The composition of coal chemical wastewater is complex,and phenols,cresols and other phenolic compounds which are common highly toxic organic compounds exist in this type of wastewater.Solvent extraction is a common method for treating phenol-containing wastewater in coal chemical industries.Compared with traditional extractants,dibutyl ether has low solubility in water.So dibutyl ether in the raffinate phase does not need to be stripped,which greatly saves the investment of the stripper and daily operating costs.In this study,dibutyl ether is adopted as the extraction solvents to extract and recover phenols from the wastewater,by which the concentration of phenols in the wastewater would be reduced to 300 mg·L^-1 to meet the concentration requirement of phenols in further biochemical treatment process of the wastewater.In this work,liquid-liquid phase equilibrium data of ternary systems dibutyl ether one of four kinds of phenols(phenol,o-,m-,p-cresol)+water at T=(298.15,313.15,333.15)K were determined and then tested the reliability by Othmer-Tobias and Hand equations.The correlation coefficients R² are greater than 99.4%,which demonstrated good linearity.The distribution coefficients(D)and separation factors(S)were calculated to evaluate the efficiency of DBE in separating phenol from aqueous phase and separately.The distribution coefficients(D)and separation factors(S)indicated that it was more difficult to extracted phenol than cresols.The experimental data were correlated by NRTL and UNIQUAC models,and the corresponding binary interaction parameters and the correlated data were obtained.The root mean square deviation(RMSD)between experimental liquid-liquid equilibrium data and the correlated liquid-liquid equilibrium data was not exceed 0.8%,which show that the regressed values from both models are satisfactory.The liquid-liquid equilibrium data of the quaternary system(dibutyl ether+phenol+catechol+water)was measured,and the correlated data and binary interaction parameters were also obtained by regression with NRTL and UNIQUAC models.The deviations(RMSD)between experimental liquid-liquid equilibrium data and the correlated liquid-liquid equilibrium data of the quaternary system were less than 0.25%.The process simulation of extraction and solvent recovery of 100ton·h^-1 coal-chemical Engineering wastewater with dibutyl ether and methyl isobutyl ketone was carried out by Aspen Plus.The process simulation results of dibutyl ether as the extractant showed that,with stages of 5 and phase ratio of 1:1.67,the concentration of dibutyl ether and methyl isobutyl ketone at the bottom outlet of the extraction tower was 150 mg·L^-1 and the concentration of total phenols can be reduced to 300 mg·L^-1 from 6000 mg·L^-1 by solvent extraction at the temperature of 40?.After the extraction process,the wastewater met with the requirement of the subsequent biochemical treatment.According to the utilities cost estimation results,the utility cost was 19.08 yuan or 12.61 yuan for treating per ton highly concentrated phenol-containing coal-chemical industry wastewater with dibutyl ether or methyl isobutyl ketone.