Experimental characterization of turbulent particle laden reactive flows under air and oxy-fuel conditions

  • Experimentelle Untersuchung turbulenter partikelbeladener Strömungen unter Reaktiven Luft- und Oxyfuel-Bedingungen

Zabrodiec Garcia, Diego Manuel; Kneer, Reinhold (Thesis advisor); Dreizler, Andreas (Thesis advisor)

Aachen : RWTH Aachen University (2021, 2022)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021

Abstract

Pulverized coal combustion is one of the most employed thermal processes for heat and power generation, being an important source of global CO2 emissions. Oxy-fuel combustion is a promising technology which has the potential to significantly reduce these emissions. In oxy-fuel combustion processes, carbon-based fuels are burned in an oxidizing atmosphere mainly composed of an O2/CO2 mixture instead of conventional air (O2/N2). The substitution of the oxidizer significantly facilitates the capture of CO2 gas and the posterior storage and sequestration. However, given the complexity of the involved mechanisms, significant research is still required for a successful large-scale implementation the technology. This work presents an experimental study conducted on pulverized coal flames under air and oxy-fuel conditions, with the objective of deepening the understanding of their characteristics and behaviour. Experiments were conducted in a pilot-scale combustion chamber employing two different annular-swirl burners and lignite as fuel. Two sets of flames, with different thermal power and oxidizer composition, were used in this study. The first set is composed of three 60 kW flames with the same stoichiometry but different oxidizer composition (one air case and two oxy-fuel cases with 21 and 25 vol.-% O2 content). The second set is composed of four 40 kW flames with varied stoichiometry (one air case and three oxy-fuel cases with 23, 27 and 33 vol.-% O2 content). Flame aerodynamics were studied using two-dimensional laser Doppler anemometry. Complementary flame radiation measurements were also conducted to evaluate the spectra and estimate particle temperatures. Results show that flow patterns are determined mainly by the burner inlet conditions. The higher momentum of the oxy-fuel mixtures can also have a significant effect on the flow patterns and reactant mixing. Different O2 contents in the oxidizer can also affect the flame shape and swirl intensity. Radiation measurements revealed the presence of emission lines from several minerals. Particle temperatures in oxy-fuel cases with higher O2 contents, were observed to be similar as in the air cases.

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