Direct and two-step gasification behaviour of Victorian brown coals in an entrained flow reactor

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Abstract

This study assesses the gasification behaviour of three Victorian brown coals in CO2 using a bench – scale entrained flow reactor in terms of gas quality and carbon conversion. Two gasification processes were investigated: a) gasification of coal in a single step, b)pyrolysis of coal followed by gasification of the char in two steps. The effect of temperature (1000–1400 °C)and input CO2 (10–40 vol%) concentration on two gasification process was investigated. It was found that higher temperature and input CO2 concentration increased CO concentration and carbon conversion. The gasification process (direct and two-step gasification) had little effect on the overall carbon conversion but had a significant effect on the gas composition of the product gases. During two-step gasification, coal pyrolysis contributed to around 65% carbon conversion, almost all H2 and 22–30% CO. Char gasification contributed to around 35% carbon conversion and 70–78% CO. By contrast, direct gasification generated little H2 and more CO in the product gases than two-step gasification. It was estimated that the CO was generated from coal pyrolysis (18.8–24.2%), Boudouard reaction (55.1–66.5%), and the reverse water-gas shift reaction (13.1–19.3%). Regardless of direct or two-step gasification, it was found that entrained flow gasification achieved very high carbon conversion (∼98%)for Victorian brown coals at 1200 °C with around 7 s residence time for the particle size of 90–106 µm.

Original languageEnglish
Pages (from-to)1044-1055
Number of pages12
JournalEnergy Conversion and Management
Volume195
DOIs
Publication statusPublished - 1 Sep 2019

Keywords

  • Brown coal
  • Direct gasification
  • Entrained flow
  • Gasification
  • Pyrolysis
  • Two-step gasification

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