Extraction And Spectrum Research Of Typical Coal And I Ts Pyrolysis Products

As the largest part of the energy structure in China,the application of coal cleaning technology has become one of the problems to be solved urgently.Among them,the pyrolysis of coal is an important link in the application of the coal industry,and it is also the best research method for low-rank coals with complex structures.Limited by the complexity of the coal structure,the mechanism of pyrolysis of coal is unclear,and a lot of research in this regard are conducted by so many scholars.Based on the research status at home and abroad,this article is aimed at coal and its char,to explore the extraction characteristics of organic solvent by carrying out extraction experiments;The changes of parameters in the thermal evolution of coal are studied through pyrolysis experiments;To carry out spectral analysis of different coal and its char by using nuclear magnetic resonance technology(NMR)and terahertz time-domain spectroscopy(THz-TDS)as technical means.The main research contents of this paper are as follows:Three kinds of coal samples and three kinds of organic solvents with different polarity are selected,the experiments of ordinary thermal extraction,microwave-assisted extraction and reaction kettle extraction are carried out systematically.The results showed that the extraction characteristics of tetrahydrofuran is the best and that of petroleum ether is the worst.With the increase of extraction temperature,the extraction rate increase in the experiment of microwave-assisted extraction and reaction kettle extraction with different growth rate.Compared with the other two extraction methods,the highest extraction rate occurs in microwave-assisted extraction with unique advantages,and the lowest extraction rate occurs in reactor extraction.The extraction rate of the three extraction methods increase with the increase of fixed carbon content in coal samples,showing a positive relationship.The extraction rate of fractional extraction and single-stage extraction showed different changes,with the former decreasing first and then increasing,while the latter increasing first and then decreasing.Char samples with different pyrolysis temperatures and different conversion rates are prepared by char preparation experiment.Tetrahydrofuran is used as the extractant for extraction experiment.The results showed that the extraction rate of low temperature pyrolytic char decreased first and then increased with the increase of residence time.With the increase of temperature,the extraction rate of char with the same conversion rate increases first and decreases,then increases slowly.The change of fractional extraction of char is similar to that of single-stage extraction,but the overall fluctuation is less than that of single-stage extraction,and the extraction rate of the second-stage tetrahydrofuran extraction is the lowest.The extraction products of coal and its char are analyzed by liquid phase NMR.The fraction of aliphatic methyl carbon and the protonated aromatic carbon are extracted by using tetrahydrofuran.The changes of the experiment using microwave assisted extraction,with the increase of extraction temperature,the fraction of methylene carbon and protonated aromatic carbon increase in the number of species.By using reactor extraction,the experimental changes is that with the increase of extraction temperature,the number of fraction of aliphatic methyl carbon and fraction of aromatic methyl carbon increases first and then decreases.The containing fat part of the fraction of aliphatic methyl carbon,fraction of methylene carbon and fraction of aromatic methyl carbon material are extracted in the experiment of char extraction.By comparing the peak reference table,we can know that the molecular weight of the extracted substance is mostly concentrated between 60 and 90.The THz-TDS is used to analyze the coal,its char and their residues.The result show that,the signal is best at 20MPa.The change of signal delay and amplitude of seven coal samples is divided into three regions.Through the analysis of absorption coefficient(K)and average refractive index(M),the relationship between K and M and parameters of macro industrial analysis and element analysis is obtained.By analyzing of coal and coke and their extractive residues,the result show that,the values of K and M are the lowest for ordinary thermal extraction and the highest for microwave-assisted extraction at 120?.Among the three extraction methods,the value of maximum K appeared in reaction kettle extraction and the value of maximum M appeared in microwave-assisted extraction.In the fractional extraction,the values of maximum K and M appeared in the second stage extraction.For char and its extracted residue,the change law of K and M values of low-temperature pyrolytic char is that with the increase of char residence time,it first decreases and then increases,and the increasing trend is not obvious.With the increase of pyrolysis temperature,the absorption and refraction signals drift.