Simulation investigation on separation characteristics of gas-liquid model products from in-situ pyrolysis of tar-rich coal

As a significant strategic resource, tar-rich coal possesses the potential to produce tar, gas, and high-value-added chemicals. The in-situ pyrolysis technology is regarded as a promising method for carbon sequestration and efficient utilization of tar-rich coal. However, the high viscosity of tar creates resistance that complicates the separation of oil-gas resources from other multiphase products generated by in-situ pyrolysis. In this study, computational fluid dynamics (CFD) was employed to investigate the separation characteristics of multiphase products from the in-situ pyrolysis of tar-rich coal in a gas-liquid cylindrical cyclone (GLCC). The study focused on the flow field and separation performance, analyzing the effects of tar ratio, tar component, inlet velocity, and gas-liquid ratio on separation efficiency. The simulation results illustrate that along with the gas flow rates, the thickness and length of liquid film, the carrying capability of gas flow, and the intensity of the swirling field all increase. However, the droplet separation is hindered by insufficient swirl intensity at low flow rates and excessive shear effects at high flow rates. In the context of in-situ pyrolysis of tar-rich coal, the GLCC is better suited for scenarios with low tar content, a low gas-liquid ratio, and tar with a higher proportion of light components. The present work contributes to the green and efficient utilization of tar-rich coal, and it also aims to provide data support for optimizing the separation performance of multiphase pyrolysis products of tar-rich coal.