Development Of Low Temperature Coal Tar Ethanolamine Extraction Process

As important chemical raw materials and intermediates,phenolic compounds have important economic value.Low-temperature coal tar contains 20% ~ 30% of phenolic compounds.Extracting phenolic compounds from low-temperature coal tar can not only reduce hydrogen consumption in subsequent production processes,but also improve economic benefits.In our previous work,it was verified that ethanolamine can be used as an extractant to efficiently and cleanly separate phenolic compounds from low-temperature coal tar.95% extraction rate of phenolic compounds in low temperature coal tar by ethanolamine.In this paper,the process of extracting phenolic compounds from low-temperature coal tar by ethanolamine method was conceptually designed and optimized.1.According to the measured vapor-liquid phase equilibrium data of the binary system,Data Regression of Aspen Plus was used to fit the thermodynamic parameters of the ethanolamine and phenol,ethanolamine and m-cresol systems.In the conceptual design of the process,a suitable thermodynamic model and accurate thermodynamic parameters are one of the necessary conditions to ensure accurate system simulation.Among phenolic compounds,phenol is selected as a key component and m-cresol is a non-critical component according to the boiling point.The high-pressure vapor-liquid equilibrium device is used to determine the isobaric vapor-liquid equilibrium data of the binary system,that is,T-X-Y data: determine the vapor-liquid phase equilibrium data of the ethanolamine-phenol system at 101.3Kpa,202.6Kpa,303.9Kpa,and 405.3Kpa;the measurement is at 101.3Kpa vapor-liquid equilibrium data of ethanolamine-m-cresol system.Use the area test and the van ness test to check the thermodynamic consistency of the measured vapor-liquid phase equilibrium data.After the test is passed,the binary interaction parameters of the NRTL model,Wilson model and UNIQAC model are regressed by Aspen Plus and error analysis is performed.The error of the regressed NRTL model is smaller than that of Wilson model and UNIQAC model.In the conceptual design and optimization of subsequent processes,the regressed NRTL model is used as the thermodynamic model.2.After the low-temperature coal tar was extracted with ethanolamine,the ethanolamine content in the extracted phase was about 71 wt%.Single column distillation was used to separate ethanolamine from phenolic compounds.The design stipulates that the ethanolamine content in the tower top stream is 99 wt%,and the ethanol content in the tower kettle output stream is 0.1 wt%.When the design requirements are met,the energy consumption of single column distillation reboiler is 9.22MW/T(low temperature coal tar).In order to reduce energy consumption,two types of double-effect distillation processes,LGH and HGL,are designed.Compared with single-column distillation,LGH double-effect distillation reduces energy consumption by 20% and HGL double-effect distillation achieves 44.8%.3.After the low-temperature coal tar is extracted with ethanolamine,the ethanolamine content in the raffinate phase is about 2.1 wt%.Because water and ethanolamine are completely miscible,the boiling points of ethanolamine and water are very different.The ethanolamine in the raffinate phase is back-extracted with water,and the ethanolamine-water system is separated by single column distillation after extraction.In Aspen Plus using the Extract module to simulate the back-extraction process of the raffinate phase-water system,due to the lack of corresponding liquidliquid phase equilibrium data and other reasons,there is a large error between the simulation results and the actual results.The extraction effect of water and raffinate was determined by the results of extraction experiments.It has been proved by backextraction experiments that the solvent ratio(water: light oil)is 2: 1.After shaking at a constant temperature water bath shaker at 60 ° C.for 40 minutes and back-extracting three times,the ethanolamine content in the layer light oil was 0.17 wt%,and the ethanolamine content in the water phase was 0.97 wt%.The water-ethanolamine system in the extraction phase was simulated by single column distillation.To meet the design requirements: the ethanolamine content in the aqueous phase produced at the top of the tower is less than 0.01 wt%;the ethanolamine content in the tower kettle produced liquid is controlled at 99 wt%,and the heat load of the reboiler of the extractant recovery tower is 0.514MW/T(low temperature coal tar).In this paper,the conceptual design of the extractant recovery process after ethanolamine extraction of low-temperature coal tar phenolic compounds and optimization of operating parameters were performed.The research in this paper will lay the foundation for the industrial application of ethanolamine in the extraction of phenolic compounds from low-temperature coal tar.