Experimentelle Untersuchung und reaktionskinetische Modellierung der Pyrolyse biogener Feststoffe

• Experimental investigation and reaction kinetic modelling of the pyrolysis of biogenic solids

Pielsticker, Stefan; Kneer, Reinhold (Thesis advisor); Scherer, Viktor (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022

Abstract

In this work, the reaction kinetics of biomass during pyrolysis is investigated experimentally and described by modelling. A laboratory-scale fluidised bed reactor coupled with a Fourier-transform infrared spectrometer is used for the experimental investigations. To determine the intrinsic reaction rate, individual samples of pulverised fuel are batch-wise dosed into the reactor at different reactor temperatures (573-1473 K) and the volume fractions of the gaseous pyrolysis products are measured ex situ, quantitatively, and time-resolved in the FTIR gas cell. In addition to different real biomasses, extracted biomass structural components (cellulose, hemicellulose, lignin) are investigated as important model fuels while fossil fuels serve as references. The experimental data obtained are used to calibrate two empirical models of different complexity. Furthermore, the phenomenologically based chemical percolation devolatilisation model (CPD) is optimised, modified for biogenic fuels, and adapted for the experimental boundary conditions of the fluidised bed reactor by implementing suitable balance equations.Using Rhenish lignite as a reference fuel, the model adaptations of the CPD model can be successfully validated. The subsequent analysis of the parameter sets of the bio-CPD model available in the literature provides a combination to describe the time-dependent reaction behaviour for cellulose and hemicellulose in the fluidised bed reactor. For lignin, an improved parameter set is derived via a sensitivity analysis. The superposition of the individual components to describe the pyrolysis behaviour of real biomasses shows that trends (especially for the integral products) can be well expressed. However, the kinetic process itself depends strongly on the interaction of the components. This finding applies equally to the empirical models as well as to other reactor concepts.