煤系针状焦生产过程中, 延迟焦化工艺流程中混合油的性能在一个生焦周期内不断发生波动, 如何稳定混合油的性能是确保针状焦质量均匀的一个关键因素。 而混合油性能的差异主要体现在粘流特性的变化方面, 导致这种差异的根源是混合油分子结构发生了变化。 为了进一步定量分析混合油性质变化的根本原因, 本文以一个生焦周期内不同进料时间的混合油为研究对象, 利用傅里叶变换红外光谱(FTIR)分析仪和旋转粘度仪为检测手段。 从红外光谱波数范围700～900, 1 550～1 650, 2 800～3 000和3 000～3 100 cm-1四个区域入手, 引入6种分子结构参数。 详细分析探讨了一个生焦周期内混合油分子结构的变化趋势与粘流特性的关联性。 FTIR谱图分析显示混合油主要是以带有部分脂肪侧链的缩合芳香环结构组成的。 随着生焦过程的进行, 混合油分子中脂肪侧链的支链化程度(I1)不断降低、 芳香度(I2)有所增加。 而芳环的缩合度参数I3以及芳环上的取代情况(I4, I5, I6)的变化较小, 这说明混合油的缩合程度随生焦时间的增加变化不大。 混合油中多组分复杂芳香类物质的共存, 导致了分子间易发生缔合, 使得混合油的初始表观粘度值很大。 混合油的粘流活化能Eη随着生焦时间的延长而呈现出增加的趋势。 理论上缩合芳环和烷基侧链对粘流性质的影响最大, 但是将I1, I2, I3与Eη进行分析时发现回归曲线的拟合优度R2仅可达到0.71。 实际上, 混合油本身支链化程度(I1)低, 支链长度短, 忽略I1对粘流活化能的影响时, 对I2, I3与Eη进行数据处理获得的回归曲线的拟合优度R2反而降低。 综合考虑所有的分子结构参数与Eη进行回归分析时, 回归曲线的拟合优度R2可以达到0.98, 混合油的分子结构参数与粘流特性之间的关系模型为: Eη=703.59-55.88I1-7.83I2+5.73I3-1 866.70I4-694.85I5-83.16I6。 由此可见, 粘流特性是混合油这一复杂体系中所有分子结构特征的宏观表现。

During the production of coal-based needle coke, the performance of the mixed oil fluctuates continuously in a coking cycle due to the delayed coking process. How to stabilize the performance of mixed oil is a key factor in ensure the uniformity of needle coke quality. The difference in the properties of mixed oil is mainly reflected in the change of viscosity. In order to quantitatively analysis of the change of mixed oil, the mixed oil with different continuous feeding time in the same production cycle has been detailed analyzed in this study. Briefly, the Fourier Transform Infrared Spectroscopy (FTIR) analyzer and the rotational viscometer have been used as the detection means, and six kinds of molecular structural parameters which calculated from the various range of FTIR spectrum (700～900, 1 550～1 650, 2 800～3 000 and 3 000～3 100 cm-1, respectively) were used as the significant factors to characterized the mixed oil. The correlation between the viscous fluid flow characteristics and the molecular structure of the mixed oil was discussed in detail. The results showed that FTIR spectrum analysis showed that the mixed oil was mainly composed of condensed aromatic rings with partial aliphatic side chains. The branching degree (I1) of aliphatic side chains decreased continuously, and the aromaticity (I2) in aromatic structure increased slightly in the mixed oil during the production of coal-based needle coke. However, the variation of aromatic ring condensation degree I3 and substitution of aromatic rings (I4, I5, I6) changed slightly, which indicated that the degree of condensation of blends changed little with the increase of coking time. The coexistence of multi-component complex aromatic substances in the mixed oil led to easy association among molecules, which made the initial apparent viscosity of the mixed oil was large. And the viscous fluid flow activation energy Eη increased with the prolongation of production time. In theory, the condensation aromatic rings and alkyl side chains have the greatest influence on viscous flow properties, but when I1, I2, I3 and Eη were analyzed, it was found that the goodness of fit of regression curve R2 can only reach 0.71. In fact, the branching degree of the mixed oil was low and the length of the branching chain was short. When the influence of I1 on the viscous flow activation energy was neglected, the goodness of fit R2 of the regression curve obtained by data processing of I2, I3 and Eη decreased. Considered all the molecular structure parameters and Eη for regression analysis, the goodness of fit of regression curve R2 can reach 0.98. The relationship between the viscous fluid flow characteristics and the molecular structure followed the following model: Eη=703.59-55.88I1-7.83I2+5.73I3-1 866.70I4-694.85I5-83.16I6. It can be seen that the viscous flow characteristics were the macroscopic manifestation of all the molecular structure characteristics in the complex system of mixed oil.