Heterogene Reaktionskinetik alternativer Festbrennstoffe

  • Heterogeneous reaction kinetics of alternative solid fuels

Kreitzberg, Thobias; Kneer, Reinhold (Thesis advisor); Scherer, Viktor (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021

Abstract

To achieve the 1,5 °C goal proclaimed in the Paris Agreement, drastic measures for the reduction of worldwide CO2 emissions are indispensable. A contribution to the realization of these goals can be made by Carbon Capture & Utilization and Carbon Capture & Storage technologies, in which CO2 formed in combustion processes is either further processed and utilized (CCU) or compressed and stored (CCS). For the successful application of these processes sound understanding of the thermochemical conversion processes of the fuels used in this context is a fundamental requirement. With the experimental and theoretical investigations on the heterogeneous conversion of carbonaceous solid fuel particles from alternative raw materials, this work contributes to the realization of these technical processes. In addition to a biogenic fuel made of torrefied beech wood, a surrogate fuel consisting of residues is analyzed. As a representative of fossil fuels, Rhenish lignite is also included as a reference in the investigations of this work. The conversion of these fuels is carried out experimentally in a specially designed lab-scale fluidized bed reactor in a temperature range from 450 °C to 1200 °C and gas atmospheres consisting of 20 Vol.-% oxygen, carbon dioxide and water vapour at atmospheric pressure. The investigations reveal clear discrepancies in the rate of conversion of the surrogate fuel and beech wood during conversion with CO2 and H2O in the temperature range 700 – 1000 °C, while for higher temperatures convergence of both reaction rates is observed. Different mass transfer resistances are identified for both fuels as the main reason. The experimental results are used to extract kinetic parameters for a detailed one-dimensional particle model, in order to obtain a predictive tool for thermochemical conversion of alternative fuels in complex gas mixtures.

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