An Experimental Study on the Quantitative and Qualitative Characteristics of Tar Formed during Ex Situ Coal Gasification

Over the three-day gasification test of a large coal block with oxygen in atmospheric pressure conditions, yield and composition tar collected was investigated. The sampled approximately every 7 h into sorption tubes directly from reactor outlet. Sand, moisture content 11%, used as an insulating material to simulate environment gasified seam. Light aromatic hydrocarbons (BTEX), phenols, polycyclic (PAHs) were determined tar. results that obtained recalculated concentrations individual components its mass stream process gas. residence time reactor, molar mass, H/C ratio also calculated. As reaction progressed, water contained wet sand started react coal, which significantly affected amount gas produced Due increase generated gases steam, vapours decreased ranging 1 s at beginning 0.35 end. characterised by high average BTEX fractions 82.6%, PAHs 14.7%, phenols 2.7%. Benzene dominant compound, concentration 83.7%. compounds, especially benzene, result secondary processes taking place (hydrocracking steam reforming), which, presence hydrogen heavier transformed lighter ones. total this UCG (underground gasification) process—calculated per ton coal—was 1.8% (counted on basis analysed composition). Comparing efficiency classic coking process, about three times lower.