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In this work, Huadian oil shale from China was treated by hydrothermal pretreatment at 200 °C with 1.0–2.5 h in order to investigate the effect of hydrothermal pretreatment on pyrolysis product distribution and characteristics of oil. The differences in the elemental composition and thermal behavior between the untreated and treated oil shale were analyzed and compared. The hydrothermal treatment process could decompose oxygen functional groups and remove some water soluble inorganics in oil shale, which decreased the formation of gas and water during the pyrolysis. However, hydrothermal pretreatment was conducive to increasing shale oil yield. The maximum of oil yield was obtained at the pretreatment time of 2.0 h. The enhancement of the free-radical reactions during the pyrolysis and the reduction of the secondary cracking reactions of the generated oil vapors were considered as the main reasons. The oil obtained by the treated oil shale had a higher H/C ratio, indicating it had high energy content. The analysis results of chemical compositions in oils showed that the relative content of aliphatic hydrocarbons significantly increased after hydrothermal pretreatment. The further analysis demonstrated that the increase in the pretreatment time caused the generated long chain hydrocarbons tended to be directly released from oil shale particles, and were condensed into the oil. [ABSTRACT FROM AUTHOR]

In our work, thermal behavior and kinetic characteristics of spent lark mushroom substrate were evaluated to elaborate the thermal decomposition mechanisms and explore the influence of heating rate by using thermogravimetric analyzer and Coats–Redfern method. The study of pyrolysis temperature of raw material was also operated at the range of 410–530 °C, under the feeding rate 0.36 g/min, and the nitrogen flow 16 L/h. The results showed that the maximum bio-oil yield was obtained at 470 °C with the yield of 14.4 wt.%. The analysis of Fourier transform infrared spectrometer and gas chromatography coupled with mass selective detector indicated that the target liquid production was consisted of phenols, hydrocarbons and other components. Simultaneously, the low oxygen and high hydrogen content in bio-oil was also determined by elemental analysis. Based on the above-mentioned results, we demonstrated that the bio-oil obtained from the substrate had high utilization value as a potential energy resource. [ABSTRACT FROM AUTHOR]

• A new stable and cost-efficient solar absorber for solar-based applications. • Reveals the influencing factors of photothermal conversion efficiency of nanofluid. • The highest relative efficiency reaches 91.6% at 3 suns. For high-temperatures surfaces, surface absorbers possess a higher evaporation rate while volumetric receivers have a higher solar vapor generation efficiency by localizing high temperatures to the interior of the receiver and thus reduce surface losses. In this work, the solar vapor generation rates and efficiencies of several direct absorption solar collectors were compared by using reduced graphene oxide/graphene oxide and silver nanofluids as evaporators, two of which deserve to be noticed. One is the hybrid nanofluids containing reduced graphene oxide decorated with silver nanoparticles in volumetric solar absorbers and the other one is hybrid nanofluids containing reduced graphene oxide with silver floating on the surface, combining surface absorbers and volumetric ones. The results show that relative efficiency monotonously increases with the light density (e.g. correspondingly changes within 61.5% at 1 sun, 62% at 2 suns, 64% at 3 suns and 69% at 4 suns for 0.45 mg/ml reduced graphene oxide) and nanofluid concentration. The further experiments reveal that nanofluid-assisted vapor generation efficiencies of hybrid nanofluids containing reduced graphene oxide with silver floating on the surface were higher, reaching 91.6% at 3 suns, than the others due to its higher absorbance and plasmonic effect of the nanoparticles and high thermal conductivity of graphene nanosheets. This demonstration of hybrid nanofluids containing reduced graphene oxide with silver floating on the surface holds the promise of significantly expanding the potential applications in desalination, water treatment and power generation. [ABSTRACT FROM AUTHOR]