Conjugated processes of black liquor mineral and organic components conversion in supercritical water

The conversion of black liquor (BL) in supercritical water (SCW) at a pressure of 30 MPa and different temperatures ranged from 400 to 750 degrees C was studied using a tubular reactor made of stainless steel. It follows from the mass spectrometric analysis that at 600 degrees C the gasification degree of BL organic matter is alpha = 65% wt., while when increasing the temperature to 750 degrees C, alpha > 100% due to water decomposition. It was revealed that the conversion of the main mineral components of BL (NaOH and Na2S) to Na(2)CO(3 )results from their interaction with the products of SCW gasification of BL organic matter. As was detected, solid products of SCW conversion of BL contain elemental sulfur. It is shown that regeneration of alkali is effectively realized by pumping SCW through the layer of Na2CO3 powder that results from removal of CO2, generated through reaction of Na2CO3 + H2O -> 2NaOH + CO2.