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Abstract

Underground Coal Gasification (UCG) technology is steadily improving due to high scientific and industrial efforts in currently over 14 countries worldwide. A fundamental UCG objective refers to syngas production for multiple end-uses, accompanied by environmental impact mitigation focusing contaminant reduction. In terms of this topic, the control of groundwater quality endangering tars has been a key problem rarely addressed in UCG publications so far. Considering UCG main sub-processes, operating parameters and tar spectrum knowledge grounded upon established thermodynamic equilibrium principles, an innovative and flexible model approach for coupled gas quality-tar production balances is presented here. The model is validated against literature data of the Hanna-I and Centralia-Partial Seam CRIP (PSC) field trials. For both trials good matching results were found. Main gas compounds and Lower Heating Values (LHVs) results are close to reported data partly reaching less than 10% deviation (relative error range for main compounds 4.32–18.6%, LHV 6.60–21.7%). Tar literature trend-modeling comparisons down to the single pollutant scale are addressed for the first time considering published data. Results here successfully reflect main qualitative tar tendencies, while current quantitative prognoses are on a satisfactory level, and expected to be further improved with the availability of more comprehensive in-situ data.