Staged Condensation of Coal Tar from the Pyrolysis of Coal in a Screw Pyrolyzer

Abstract

Staged condensation of coal tar was studied with a three‐staged condensation system (first stage S1, 100–300 °C; second stage S2, 30–70 °C; third stage S3, 0 °C) to perform on‐line preliminary removal of dust and fundamental fractionation of tar components. The dust and heavy components are predominantly distributed in S1. The polycyclic aromatic hydrocarbons are abundant in S1. Aliphatics and monocyclic phenols are abundant in S2, and the tar in S3 is rich in aliphatics and monocyclic aromatic hydrocarbons. With increasing S2 temperature from 30 to 70 °C, the total organics in the water phase in S2 and S3 are least at an S2 temperature of 50 °C, which is advantageous for post‐treatment of wastewater.

Changes in properties of tar obtained during underground coal gasification process

“…The higher the intensity, the higher the temperatures and the longer the residence tar in the pipeline. Moreover, due to the temperature difference between the beginning and end of the pipeline, the heavier components of tar are liquefied (fractional distillation), and only the lighter components reach the surface (Liu et al 2020;Philips and Muela 1977). Condensation of tar in the pipeline is very unfavourable because the pipeline diameter decreases; in extreme cases, it may become clogged (Department of Energy 2009).…”