焦油裂解动力学是热解模型及反应器设计和运行的基础,目前研究将焦油作为整体予以考虑,然而轻质焦油和重质焦油的裂解特性存在显著差异。为了更准确地获得不同馏分焦油在不同温度下的裂解行为和二次反应模型,在微型流化床反应分析仪(MFBRA)考察了轻质焦油和沥青(重质焦油代表物)在550、600、650、700℃的裂解特性和反应动力学。结果表明,随温度升高,轻油和重油裂解生成的气体显著增加,其中轻油裂解的气体以CO和CH4为主,而重油裂解的气体主要由CO、CH4和H2组成。相较轻油,重油更易裂解,反应所需时间更短。基于等温法获得的轻质焦油裂解的平均活化能为49.49kJ/mol,明显高于重质焦油裂解的平均活化能(33.47kJ/mol)。通过对比模型法和等温法的活化能,筛选出最概然机理函数:重油裂解过程中CO、CH4和H2的生成分别符合化学反应(n=2)、三维扩散(球形对称)和收缩几何形状(圆柱形对称)模型;轻油裂解CO和CH4的生成符合化学反应(n=3)和三维扩散(球形对称)模型。试验结果为焦油选择性裂解的数值模拟提供更合理的二次反应模型。

The kinetics of tar cracking is essential to an accurate pyrolysis model and reactor design. Previous studies have predominantlyfocused on the overall cracking behavior of tar. However, it is evident that the cracking behavior differs significantly between light andheavy tar fractions. In order to gain a more precise understanding of the cracking behavior at different temperatures and establish a secondary reaction model, the cracking behavior and reaction kinetics of two distinct tar fractions were investigated using a micro fluidized bed reaction analyzer (MFBRA) under Ar atmosphere conditions at 550,600,650,700 ℃ . The results demonstrate that higher temperatures result in increased yields of cracking-formed gases. Specifically, light tar cracking primarily produces CO and CH4, while heavy tar generates CO, CH4, and H2 as its main products. Moreover, heavy tar exhibits more readily occurring cracking with shorter reaction times compared to light tar. By employing an isothermal method in MFBRA analysis, it is found that the average activation energy for light oil cracking was 49.49 kJ/ mol, which is higher than that for heavy oil cracking (33.47 kJ/ mol). Furthermore, by comparing activation energiesobtained from isothermal methods with mechanism models, suitable mechanism functions are identified: a chemical reaction (n= 2) modelfor CO during heavy oil cracking, three-dimensional diffusion models (spherical symmetry) for CH4 during both types of oil cracking, anda contraction geometry model (cylindrical symmetry) for H2 specifically during heavy oil cracking but not present in light oil cracking scenarios. These results provide valuable insights into developing reasonable secondary reaction models for simulating selective oil cracking.

0 引言

1 试验

   1.1 试验原料

   1.2 试验装置和方法

   1.3 数据处理方法

   1.4 动力学计算

2 结果与讨论

   2.1 轻质焦油和沥青的裂解特性

   2.2 焦油裂解反应活化能

   2.3 焦油裂解反应机理函数

3 结论