Studies of the Co-pyrolysis of Oil Shale and Wheat Straw

Abstract

The co-pyrolysis characteristics of oil shale−biomass blends were investigated by open-system pyrolysis with a thermogravimetry−mass spectrometry (TG−MS) analyzer and by closed-system pyrolysis with a fixed-bed reactor. Online Fourier transform infrared (FTIR) spectrometry and gas chromatography−mass spectrometry (GC−MS) were employed to analyze the gas and liquid products that were generated from the closed-system pyrolysis. In addition, the Gaussian program was also employed for quantum chemistry calculations. According to the results, one important reaction mode of oil shale−biomass interactions can be described as the "biogas−kerogen" reaction, which means the combination of kerogen and some free radicals volatilized from the biomass in the temperature range of 180−400 °C. During the co-pyrolysis, the oil shale influences the distribution of the oxygen content in the biomass products, causing an increase of CO 2 and CO in the gaseous products and a reduction of oxygen-containing compounds such as alcohols, aldehydes, lipids, and ethers in the liquid products. The results will be useful for improving the quality of shale oil in the industrial utilization of oil shale in the future.

Current status of co-pyrolysis of oil shale and biomass

“…The synergetic effects were also observed to reduce the activation energy of the mixtures, which decreased mainly at low temperatures (< 400 °C). This was observed by Chen et al [80] and Dai et al [84] in the co-pyrolysis of OS with wheat straw grain and microalgae, respectively. However, the synergetic effects noticed in co-pyrolysis cannot be generalized, as a study by Kiliç et al [19] with OS and E. rigida and that by Janik et al [81] with OS and Terebinth berries found that co-pyrolysis behaved as an additive process, resulting in additive yields of products from the individual FS pyrolysis.…”

“…In various studies, these interactions resulted in non-linear changes in yields, unlike the linear changes in yields from the individual pyrolysis of FS. The interactions also increased the yield of oil and its H/C ratio, as observed by Chen et al [79], and the yield of gas while reducing that of solid residues [80,82,[84][85][86]. The synergetic effect of co-pyrolysis can depend on the blend ratio of BM:OS, as shown by Dai et al [84], who demonstrated a maximum synergy at 30 wt% blends of OS using microalgae and OS.…”

“…The bio-oils obtained from BM pyrolysis have very different characteristics from those of shale oil. For example, bio-oil is lighter than shale oil and contains more oxygenated compounds [80]. It is mostly water-soluble differently from the mainly benzene-soluble shale oil [81].…”

Oxidation Characteristics of the Semicoke From the Retorting of Oil Shale and Wheat Straw Blends in Different Atmospheres

“…So, many researchers have pyrolyzed biomass with waste plastics, tires, coal, etc., and found that copyrolysis could increase the yield of the obtained oil and upgrade its quality [2][3][4][5]. Recently, the authors of this work investigated the co-retorting of oil shale and wheat straw [6]. It was found that the H free radical from the decomposition of wheat straw could induce the cracking of the bridge bonds of kerogen and accelerate the pyrolysis reaction.…”

“…Finally, the semicoke samples obtained from the retorting were marked as S 1-5 , respectively, according to the mass ratios of the matrix oil shale and wheat straw, and then ground below 0.2 mm for TG-MS experiments. Table 1 presents the results of proximate and ultimate analyses of semicoke samples; the compositional data about their raw material have been given by Chen et al [6]. The researchers established that there occurred interactions between samples of raw wheat straw and oil shale during the retorting.…”