Another potential advantage, when black liquor is gasified, is increased pulp yield. During gasification, at least part of the sulfur in black liquor is converted to H2S instead of Na2S. The separation of sulfur from sodium before the pulping chemicals are regenerated makes it possible to produce polysulfide or other alternative pulping liquors for higher yield pulping.
Several other factors must be considered in the design of integrated forest biorefineries. One is the need for a carefully designed energy exchange network to minimize entropy generation. Another is the need to minimize the production of NaHCO3 and the accompanying increase in lime demand for causticizing when regenerating pulping liquors. A third factor is the need and availability of technology for removing contaminants – especially tar, alkali metals, and halides – from the synthesis gas produced.
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