Pyrolysis of oil shales: influence of particle grain size on polycyclic aromatic compounds in the derived shale oils

Oil shales of different particle grain sizes were pyrolysed in a 10 cm diam eter x 100 cm high fluidised-bed reactor under both a nitrogen and a steam atmosphere. The oil shares were from the Kimmeridge clay of Jurassic age fr om the UK. The influence of particle grain size on the yield and compositio n of the oil and gases was determined. The gases were analysed for H-2, CO, CO2, CH4 and other hydrocarbons to C-4. The condensed oils were analysed f or their content of polycyclic aromatic compounds (PAC), including polycycl ic aromatic hydrocarbons (PAH), sulphur-PAM (PASH) and nitrogen-PAM (PANH). The oil yield increased with increasing particle grain size. The derived s hale oils contained significant concentrations of PAH, PASH and PANH. The c oncentration of PAC increased with decreasing particle grain size. The PAH consisted mainly of naphthalene, fluorene and phenanthrene and their alkyla ted homologues, and lower concentrations of fluoranthene, pyrene and chryse ne. The PASH identified included benzothiophene and dibenzothiophene, and t he PANH identified included indole, carbazole and their alkylated derivativ es. Increased secondary reactions linked to the formation of PAC were indic ated by the alkene/alkane ratio. The effect of steam was to significantly i ncrease the yield of oil and also to increase the concentration of PAH, PAS H and PANH in the derived shale oil compared with using nitrogen as the swe ep gas.