PYROLYSIS OF KRAFT BLACK LIQUOR - FORMATION AND THERMAL-CONVERSION OFVOLATILE PRODUCTS AND CHAR

Experimental measurements of the carbon-containing products (gases, ta r char and fine particles) were made during rapid pyrolysis of black l iquor solids at 600-1100 degrees C. The product gases were analyzed fo r carbon-containing species by Fourier transform infrared spectrometry (FTIR), and solid residues were analyzed for carbon. Pyrolysis was co mplete in less than 0.3 s at all temperatures. the char yields decreas ed with both reaction time and temperature, and ranged from about 70% at 700 degrees C to 30% at 1100 degrees C. The remaining carbon was di stributed between gases and tar. Secondary pyrolysis reactions convert ed the tar to CO, CO2, methanol, aldehydes and light hydrocarbons. The carbon-containing species detected included CO, CO2, methane, ethylen e, acetylene, formaldehyde, acetaldehyde, methanol, propylene, butadie ne, carbonyl sulphide, methyl mercaptan, and dimethyl sulphide. All of the tar produced was converted to light gases within 1.6 s at 1100 de grees C. At lower temperatures, 15-30% of the carbon input remained as tar within that reaction time.