Structural transformation of nascent char during the fast pyrolysis of mallee wood and low-rank coals

Abstract

The changes in char structure during the fast pyrolysis of three different feedstocks from 600°C to 1200°C were investigated. Western Australian Collie sub-bituminous coal, Victorian Loy Yang brown coal and Australian mallee wood were pyrolysed in a wire-mesh reactor at a heating rate of 1000 K s −1 with holding time ranging from 0 s to 50 s. FT-Raman/IR spectroscopy was used to characterise the structural features of the chars obtained at different temperatures. The combined use of a wire-mesh reactor and an FT-Raman/IR spectrometer has provided significant insights into the rapid changes in the chemical structure of nascent char during fast pyrolysis. Our results indicate that the three fuels began significant ring condensation at different temperatures. Mallee wood showed significant growth of large rings within 1 s holding at 600°C; however Loy Yang and Collie coals showed significant ring condensation at 800°C and 900°C respectively. With increase in temperature to 1000°C and higher, most ring condensation occurred at b1 s holding time. The decrease in the intensity of FT-IR spectrum at~1600 cm −1 confirmed the rapid growth in ring systems at relatively high temperatures.

Progress of Raman spectroscopic investigations on the structure and properties of coal

“…The same conclusion was reached in the study of Zhang et al. [100,101] Lievens et al [112] reported the structure of Inner Mongolia low-rank coal, concluding that its aromatic ring structures consisting of 59% amorphous structures (G L , G, G R , V L , and V R bands), 22% highly ordered structures with no less than six rings (D band), 16% aromatic structures characterized by aliphatic and/or ether substitutions (S L , S bands), and 3% substituted benzene rings (S R , R bands).…”

“…In recent years, some researchers [100][101][102][103][104][105][106][107][108][109][110][111][112] studied the structure of coal by using Raman spectroscopy and referring to the curve-fitting method by Li et al [53,86,87] Zhang et al [100,101] considered the structural changes of semicoke during the rapid pyrolysis of wood and low-rank coal at 600-1,200 C and got similar result of Li et al Wang et al [102] reported that the A…”

Effects of Alkali and Alkaline Earth Metallic Species and Chemical Structure on Nascent Char–O2 Reactivity

“…The preparation and the properties of coal samples have been described in ref . The nascent chars, which are prepared for the measurement of AAEM concentration, chemical structure, and char–O 2 reactivity, were produced under the same experimental conditions as those in ref . Briefly, the heating rate was chosen as 1000 K s –1 to achieve fast pyrolysis.…”

“…For Collie coal char, AAEM species showed the negligible effect on the nascent char–O 2 reactivity for the char prepared at 600 °C. Nevertheless, with the fast transformation of nascent char structure during pyrolysis from 600 to 1200 °C, , the roles of AAEM species and char structure on char–O 2 reactivity is still unclear, which arouse the motivation of this study.…”

Structure and CO2 Gasification Reactivity of Char Derived through Pressured Hydropyrolysis from Low-Rank Coal

“…Numerous physicochemical techniques such as Brunauer–Emmett–Teller measurements, Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance, X-ray diffraction (XRD), Raman, and so on have been applied to study the structural features of coal char and provided useful information during pyrolysis. Raman spectroscopy is being more and more widely used to characterize the microstructure of crystalline and amorphous carbon materials due to their high efficiency, nondestructive nature, and high precision. , Li and his group − compared the Raman spectroscopy of condensed aromatic compounds with the chars and identified the deconvoluted peaks of chars, and the identification method has been used to characterize the chemical structure of chars produced from low-rank coals and biomass during pyrolysis and gasification. Xu used the identification method of Li to study the relationship between coal structures and combustion characteristics and found that the Raman spectral parameters can act as a good indicator for coal combustion characteristics.…”