液化残渣的微波热解与常规热解对比分析

采用微波加热和常规电加热两种条件进行液化残渣(DCLR)的热解实验，考察了热解产物固体焦、焦油及煤气的组成及结构的变化规律，采用红外分析(FTIR)与气相色谱-质谱(GC-MS)联用技术对热解产品进行了分析表征。研究表明，在微波场中，DCLR的升温速率很快，20 min左右物料温度就可达到900 ℃，最大升温速率可达到329 ℃·min-1，而常规加热的升温速率基本保持恒定。与常规热解相比，微波热解后固体焦的产率降低2.85%，而焦油和煤气产率分别增加了0.66%和2.19%。DCLR热解后固体焦的索氏萃取组分重油(HS)、沥青烯(A)及前沥青烯(PA)含量均大幅降低，而四氢呋喃不溶物(THFIS)则有所增加，但是两种热解条件下得到的固体焦的四种索氏组成差异不是很大，说明DCLR的热解过程是以HS，A与PA的转化为主的。微波热解后固体焦红外谱上3 437.6，1 632.0 cm-1以及1 079.99 cm-1处吸收峰的强度与常规热解相比明显降低，说明微波场中DCLR的热解更为彻底。热解后焦油和煤气产率均有所增加，煤气中H₂含量均达到60%以上。GC-MS分析表明，经由石油醚萃取后的热解焦油中脂肪类、芳香类与醇类物质组成以及C_1~5，C_11~20与C₂₀以上组分的含量均没有发生明显变化，而微波热解焦油中沥青质的含量则下降了7.7%，说明微波作用可有效促进DCLR中沥青质的热分解，有利于热解焦油的轻质化。

A Comparative Study on the Pyrolysis Characteristics of Direct-Coal-Liquefaction Residue Through Microwave and Conventional Methods

The pyrolysis of direct-coal-liquefaction residue (DCLR) was prepared using microwave and conventional pyrolysis. The composition and structure of solid coke, tar and gas were investigated and the pyrolysis products were compared after characterization by infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS).Results showed that DCLR was rapidly heated up to 900 ℃ in 20 min with the maximum heating rate of 329 ℃·min-1 in the microwave field, while the heating rate of conventional heating was constant. Compared with conventional pyrolysis,coke yield decreased by 3% after microwave pyrolysis, whereas the tar and gas yields increased by 0.66% and 2.19%, respectively.After the pyrolysis of DCLR, the extracted compositions consisting of heavy oil(HS), as phaltene (A), and pre-asphaltene (PA) decreased significantly, while the content of tetrahydrofuran insolubles (THFIS) increased. The Soxhlet compositions of the solid coke did not evidently change compared with those after conventional pyrolysis, which indicated that the pyrolysis process of DCLR is mainly based on the conversion of HS, A and PA. After microwave pyrolysis,the intensity of the absorption peak at 3 437.6, 1 632 and 1 079.99 cm-1 on the infrared spectrum of the solid coke was significantly lower than that of conventional pyrolysis, which indicated that DCLR was more thoroughly pyrolyzed in the microwave field.Both tar and gas yields increased after pyrolysis, and the content of H₂ in gas reached above 60%. The results of GC-MS showed that no obvious change in the composition for aliphatics, aromatics, alcohol and the contents of C_1~5, C_11~20 and C_>20in tar was observed after extraction with petroleum ether. The asphaltene content of tar decreased by 7.7% after microwave pyrolysis, which indicated that microwave pyrolysis can effectively promote asphaltene decomposition in DCLR, which benefited tar conversion to light fraction.