Devolatilization kinetics of woody biomass at short residence times and high heating rates and peak temperatures. (15th January 2016)

• Record Type: Journal Article
• Authors: Johansen, Joakim M.; Gadsbøll, Rasmus; Thomsen, Jesper; Jensen, Peter A.; Glarborg, Peter; Ek, Paul; De Martini, Nikolai; Mancini, Marco; Weber, Roman; Mitchell, Reginald E.
• Is Part Of: Applied energy. Volume 162(2016)
• Page Start: 245
• Page End: 256
• Publication Date: 2016-01-15
• Subjects: Biomass conversion -- Devolatilization -- High heating rate -- Kinetics -- High temperature -- Low residence time; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2015.09.091
• Languages: English
• ISSNs: 0306-2619

Abstract

Highlights: High peak temperature (1405–1667 K) and heating rate ( 10 5 K s - 1 ) devolatilization. CFD aided particle history tracking. Significantly faster devolatilization kinetics than suggested in the literature. Shown to significantly change the predicted ignition distance in pilot scale. Partial conversion experiments with residence times below 0.1 s. Abstract: This work combines experimental and computational fluid dynamics (CFD) results to derive global kinetics for biomass (pine wood) devolatilization during heating rates on the order of 10 5 K s - 1, bulk flow peak temperatures between 1405 and 1667 K, and particle residence times below 0.1 s . Experiments were conducted on a laboratory laminar entrained flow reactor (LFR) using solid fuel feed rates on the order of 10–20 mg h - 1 . Employing a simple single step first order (SFOR) mechanism with an Arrhenius type rate expression, the best fit of the pyrolysis kinetics was found to be: A = 18.9 × 10 3 s - 1, E a = 21 305 J mol - 1 . The accuracy of the derived global kinetics was supported by comparing predictions to experimental results from a 15 kW furnace. The work emphasizes the importance of characterizing the temperature history of the biomass particles when deriving pyrolysis kinetics. The present results indicate faster kinetics than found in the literature, leading to predicted residence times required for full conversion one order of magnitude lower than when compared to thermogravimetric analysis (TGA) derived kinetics.