Abstract
The impacts of the composition and properties of tar products on their utilization are of great importance, while the consequences of varying tar separation conditions on distillation fractions remain underexplored. Solid impurities in special tar products (e.g., subsurface in situ pyrolysis-derived tar-like substances) can contribute to the separation as well. In the present study, low-temperature coal tar (LTCT) was used as an analogue to pyrolysis product, mixed with semi-coke and coal dust, representing pyrolytic byproducts and nonpyrolytic substances, respectively. The LTCT mixtures were tested with vacuum distillation at various pressures and temperatures. The results revealed the role of pressure in fraction distribution across temperatures, with higher pressure concentrating fractions at lower temperatures. The impact of solid impurities on distillation primarily stemmed from adsorption. Minimal concentrations of solid impurities carried coal dust/semi-coke into the distillation, but higher levels retained them in the residue. The adsorption of coal dust was quite high at lower temperatures and waned as temperature increased, unlike semi-coke, which had consistent adsorption throughout the distillation. The present study can advance the understanding of vacuum distillation for tar products in the presence of solid impurities, offering a framework for the effective distillation/utilization of coal tar. By probing separation conditions, tar properties, and solid impurity effects, the present research will refine strategies for optimizing coal tar use, crucial for enhancing energy security and sustainable progress in China.