Production of H2 and medium Btu gas via pyrolysis of lignins in a fixed-bed reactor

Lignins are generally used as a low-grade fuel in the pulp and paper industry. In this work, pyrolysis of Alcell and Kraft lignins obtained from Alcell process and Westvaco, respectively, was carried out in a fixed-bed reactor to produce hydrogen and gas with medium heating value. The effects of carrier gas (helium) flow rate (13.4-33 ml/min/g of lignin), heating rate (5-15 degreesC/min) and temperature (350-800 degreesC) on the lignin conversion, product composition, and gas yield have been studied. The gaseous products mainly consisted of H-2, CO, CO2, CH4 and C2+. The carrier gas flow rate did not have any significant effect on the conversion. However, at 800 degreesC and at a constant heating rate of 15 degreesC/min with increase in carrier gas flow rate from 13.4 to 33 ml/min/g of lignin, the volume of product gas decreased from 820 to 736 ml/g for Kraft and from 820 to 762 ml/g for Alcell lignin and the production of hydrogen increased from 43 to 66 mol% for Kraft lignin and from 31 to 46 mol% for Alcell lignin. At a lower carrier gas flow rate of 13.4 ml/min/g of lignin, the gas had a maximum heating value of 437 Btu/scf. At this flow rate and at 800 degreesC, with increase in heating rate from 5 to 15 degreesC/min both lignin conversion and hydrogen production increased from 56 to 65 wt.% and 24 to 31 mol%, respectively, for Alcell lignin. With decrease in temperature from 800 degreesC to 350 degreesC, the conversion of Alcell and Kraft lignins were decreased from 65 to 28 wt.% and from 57 to 25 wt.%, respectively. Also, with decrease in temperature, production of hydrogen was decreased. Maximum heating value of gas (491 Btu/scf) was obtained at 450 degreesC for Alcell lignin. (C) 2001 Elsevier Science B.V. All rights reserved.