Tar formation during black liquor low-temperature gasification was studied both in a full-scale steam reformer and in a small-scale gasifier.In the full-scale unit,gravimetric tar contents in the product gas were determined to correspond to approximately 4.5% of liquor organic carbon.An approximately equal amount of lighter condensable organic compounds was estimated to be present in the product gas.The tar contained phenolics and both substituted and unsubstituted multi-ring compounds.40% of the tar compounds detected by GC/MS analysis were one-ring compounds.The tars from the small-scale unit were primarily mono-,di-and tri-substituted one and two-ring phenolic compounds.Increasing the gasifier temperature decreased tar formation and increasing black liquor solids feed rate increased tar formation.
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