Study Of Producing Naphthenic Oil From Low Rank Coal Tar

The strategies regarding the energy resources and strategies predict that coal will be an important basic energy source in China for the upcoming years.Consequently,the clean,efficient and value-added utilization of medium and low rank coals has become inevitable.The researchers have agreed that the cascade utilization of medium and low rank coal could be the best approach to gain the maximum benefits from the medium and low rank coal,which is also promoted by the government.This thesis focuses on designing the comprehensive utilization process in line with the properties of coal tar derived from the medium and low rank coals.The efficient and clean conversion,and utilization of medium-and low-temperature coal tar have been proposed that promotes the generation of high value-added products.The qualitative and quantitative analysis of medium-and low-temperature coal tar explores the following key research contents: 1)The product distribution of different medium and low-temperature coal pyrolysis processes;2)The optimization of operation parameters and the prediction of product properties in the medium-and low-temperature coal tar separation and hydrogenation using the establishment of phenol compound models in medium-and low-temperature coal tar by extractive distillation and the real component kinetic model of naphthenic oil obtained the from the hydrotreated coal tar;3)The simulation and integration of whole process consisting of extraction-distillation of phenolic compounds from medium-and low-temperature coal tar that coupled with hydrofining process using a commercial process platform software.The main results and conclusions obtained from the above research contents are listed below:1)A nonlinear programming(NLP)product distribution model was established based on the experimental and industrial pyrolysis data reported in the literature.The proposed model is well-comparable with the experimental results,predicting the product distribution of products of low and medium rank coal pyrolysis with 45%-60 %(daf)fixed carbon.The NLP model can provide the target product information and pyrolysis-technology related data.In this view,a comprehensive evaluation model for the pyrolysis of low rank coals is established,which can be used to select the pyrolysis technology of different coals.Taking Naomaohu coal as raw material,the pyrolysis of five heat carrier processes(Toscoal / LR / DG / COED / MRF)was simulated by using the NLP model.Through a comprehensive evaluation of each process,it was concluded that LR and DG processes were more suitable for the pyrolysis of Naomaohu coal.2)According to the characteristics of rich phenolic compounds in mediumand low-temperature coal tar,the phase equilibrium experiment of 3,4-dimethylphenol + naphthalene azeotropic system with triethylene glycol(TEG)was carried out.The thermodynamic equations such as Wilson,NRTL,and UNIQUAC were used to correlate the phase equilibrium data.The original azeotropic system was optimized.Based on the results of qualitative and quantitative analysis of coal tar,the real component model for estimating the phenol oil fraction in coal tar oil was established.The extraction-distillation process was simulated,and the appropriate operating parameters were obtained.At the same time,the removal of phenolics from the coal tar using low eutectic solvents was established.According to the literature and industrial data,the technical parameters related to the different separation methods of phenol such as deep eutectic solvent method,caustic washing process,and extractive distillation were comparatively studied.The results showed that the extractive distillation process was better in the purification and extraction rate of phenols.3)According to the product analysis and raw material composition of hydrotreated coal tar,a method for estimating the physical properties of coal tar oil based on a carbon number-functional group matrix was established.Through this method,the physical parameters of coal tar and its hydrogenation products were obtained.Also,the kinetic model for the hydrogenation of real components present in coal tar was established.The conversion law of each component in coal tar was objectively described.The experimental results showed that the model was feasible and applicable.4)In line with the design of phenolic separation using extractive distillation and the hydro-refining kinetic model,the whole process combining the extractive distillation of phenolics and the hydro-refining of naphthenic oil was developed.According to the technical requirements of energy-saving and emission reduction,the public projects of the new process were integrated and optimized.Also,the whole process flow simulation was realized on the ASPENPLUS platform.The performance of coal tar refining naphthenic oil system technology in terms of material conversion rate,carbon dioxide emission,energy efficiency,and economic benefits was comprehensively evaluated by using the life cycle assessment(LCA)method.The results showed that the new process has advantages in economy,market risk,and emission compared with the hydrogenation of delayed coking coal tar and the hydrogenation of full fraction coal tar.