Study On Separation Of Phenolics-Aromatics-Alkanes From Low-Rank Coal Hydroliquefaction Oil

Direct coal liquefaction technology is one of the effective ways to obtain liquid fuel and chemicals by coal conversion.The technology is faced with two choices: product-oriented petroleum alternative fuels and raw material-oriented coal-based chemicals and fuels.The former needs to improve the ratio of H/C of liquefied products and reduce the heteroatom content by hydrogenation,and increase the proportion of alkanes to improve the octane / cetane number by hydrocracking.However,the large energy consumption and hydrogen consumption of this method cannot be ignored;moreover,its product is vulnerable to the shocks of oil price.The latter needs multi-step separation / refining to improve the purity and yield of product.Although products with higher value was obtained in this technology,it also required lots of energy consumption and material consumption.Therefore,the integration and evaluation of process units of direct coal liquefaction system under the two different options determine the direct coal liquefaction technology selection.Meanwhile,the establishment of direct coal liquefaction process simulation is conducive to the integration of the units and process evaluation.Based on the experiment data of 0.1 t/d continuous direct coal liquefaction by NEDOL process device,this paper at first analyzed the feasibility of establishing the direct coal liquefaction process from material balance and energy balance,and then the coal drying unit,the hydroliquefaction reaction unit and the reacted product gas-liquid-solid separation unit in the direct coal liquefaction process with Shengli lignite and Shenhua coal as raw materials were simulated respectively on the platform of Aspen Plus.In the process of establishing flowsheet,the liquefied oil was represented by the model compound and the pseudo-component,respectively.The total system material balance was calculated on the basis of the liquefied oil and the physical parameters were complemented to improve the simulation process.While the extractive distillation of phenol with triethylene glycol as solvent,the extraction of aromatics with sulfolane as extractant were studied with 180-200 ? fraction for the separation of phenolics-aromatics-alkanes.The main results and conclusions were as follows:1.Compared with the traditional process,both the temperature and pressure decreased,which leaded to the decrease of the coal conversion rate and the increase of the heavy component in the distilled oil.Although the energy consumption of the liquefaction unit reduced,the difficulty of separating the heavy oil during the separation process was increased.As a result,the energy consumption of the separation unit increased.2.Shenhua coal direct liquefaction oil was simulated with the pseudo-component as model,high and low temperature flash and vacuum distillation were included in this method.In the energy distribution,the separation could make full use of the different performance of the liquefied product for the temperature and pressure,so as to utilize the energy of the early stage,avoiding energy loss of liquefied oil separation under cold state.3.Shenhua coal hydroliquefaction reaction heat was close to the literature value while the reaction heat of Shengli coal was larger.The reason was that Shengli coal belonged to lignite,which was at a low coal-rank and with high reactivity.4.The selected model compound retained the basic azeotropic component of the coal liquefied oil,so the model compounds could be used for the simulation of liquefied oil separation,and UNIF-LBY model was appropriate for this study.5.The separation of phenolics-aromatics-alkanes of the narrow fraction of coal liquefied oil could be realized with triethylene glycol-sulfolane combination solvents and the solvent could be easily separated and recovered.Taking the separation of 180-200 ? fraction liquefied oil as example.The extraction ratio of phenolics was 99.23 wt%,and the purity was 95.75 wt%.The aviation fuel with 81.45 wt% alkanes was obtained,and the purity of aromatics could be up to 79.94 wt%.Finally,the recovery of the two solvents was more than 98 wt %.