Pyrolysis Behavior of the Black Liquor Derived from Soda-Anthraquinone and Soda-Oxygen Pulping of Rice Straw at Different Reaction End Points

Black liquor (BL) with inorganic cooking chemicals and combustible material is the alkali and power resources for pulping. For rice straw pulping, BL obtained from soda anthraquinone (AQ) pulp (SABL) could hardly be combusted in a traditional recovery furnace, because of the involvement of a great deal of silica in it. On the contrary, soda oxygen pulping may have the majority of the silica depositing in pulp owing to the oxidation, instead of its dissolution in the BL (SOBL). The pyrolysis behavior of SOBL was investigated in this paper, and composition and thermal degradation were comparatively studied by elemental analysis and TG-MS/FTIR. The reaction mechanism of pyrolysis of SOBL at different pulping end points is first revealed. The results suggested that SOBL had reasonable silicon content about one-eighth of that of the SABL, and the volatiles can be produced under relatively low temperature. For different reaction end points, with deeper oxidization, more volatiles were released at lower temperature.