Effect of Fe components in red mud on catalytic pyrolysis of low rank coal

Bayer red mud (RM) is a solid waste in alumina production, and the main components is Fe₂O₃. To investigate the effect of Fe₂O₃ in RM on pyrolysis of low-rank coal and catalytic upgrading mechanism on tar quality, pyrolysis experiments of pure Fe₂O₃ and RM mixed with a lignite, Baiyinhua (BYH) coal, were carried out. The results indicate that RM exhibits a similar catalytic effect to Fe₂O₃ in terms of product distribution and tar composition of coal pyrolysis. At 20% addition of RM or Fe₂O₃ in coal, the yield of gas and water increases, while that of char decreases; the yield of H₂ increases by 38.6% or 37.1%, and the yields of CO and CO₂ increase by 58.9%, 78.1% and 24.6%, 44.1%, respectively. GC and GC-MS results prove that the existence of RM or Fe₂O₃ improve the tar quality, and RM shows a better effect, as the content of heavy components decreases by 11.7% with RM and 5.1% with Fe₂O₃. Besides, the content of bisphenol, aliphatic hydrocarbon, oxygenated compounds and heteroatomic compounds decrease simultaneously, thus generating more monophenol and naphthalene. Several characterizations show that Fe₂O₃, as an active component of RM, provides lattice oxygen species to participate in the reaction and changes to Fe₃O₄ by partial oxidation during the pyrolysis process. TGA results and kinetic analysis of coal pyrolysis illustrate that RM can promote BYH coal pyrolysis and increase the yield of gas and liquid.