Conceptual use of vortex technologies for syngas purification and separation in UCG applications

Syngas from Africary's Theunissen underground coal gasification (UCG) project will be used for power production and synthesis of liquid fuels and commodity chemicals. However, some of the coal components, especially condensable water, oils, tars, inorganic trace elements, and a small fraction of fly ash and particulate matter, make their way to the surface via the production well and can cause adverse impacts on downstream processes. Africary's standard design incorporates a cold gas clean-up system that relies on relatively mature techniques based on highly effective wet scrubbers and acid gas removal (AGR) systems such as Rectisolv, but with the downside of low energy efficiency and waste water generation. In this paper, novel technologies for removing contaminants and species separation from the hot (T > 300 degrees C) raw syngas are compared. Comparisons are made between supersonic gas separation (SOS), Ranque-Hilsch vortex tube (RHVT), vortex gradient separation (VGS), and inertia vacuum filtering (IVF), and a vortex-based gas separation concept is proposed for UCG applications.