Influence of fast pyrolysis conditions on yield and structural transformation of biomass chars

Trubetskaya, Anna; Jensen, Peter Arendt; Jensen, Anker Degn; Steibel, M.; Spliethoff, Hartmut; Glarborg, Peter

doi:10.1016/j.fuproc.2015.08.034

Cited by 100 publications

(80 citation statements)

References 47 publications

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“…This indicates that any differences in biomass composition (cellulose, hemicellulose and lignin) between straw and wood only result in small char yield differences. The char yields of beechwood (rich in Ca, K) and wheat straw (rich in Ca, K, Si) were 4e10% points higher than char yields from pyrolysis of other lignocellulosic materials which was associated with the catalytic effect of alkali metals that affect polymerization/cross-linking [52].…”

Section: Char Yieldmentioning

confidence: 94%

Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures

Trubetskaya

Jensen

et al. 2016

Biomass and Bioenergy

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a b s t r a c tThe concentration and type of free radicals from the decay (termination stage) of pyrolysis at slow and fast heating rates and at high temperatures (above 1000 C) in biomass char have been studied. A roomtemperature electron spin resonance spectroscopy study was conducted on original wood, herbaceous biomass, holocelluloses, lignin and their chars, prepared at high temperatures in a wire mesh reactor, an entrained flow reactor, and a tubular reactor. The radical concentrations in the chars from the decay stage range up between 7$10 16 and 1.5$10 18 spins g À1. The results indicated that the biomass major constituents (cellulose, hemicellulose, lignin) had a minor effect on remaining radical concentrations compared to potassium and silica contents. The higher radical concentrations in the wheat straw chars from the decay stage of pyrolysis in the entrained flow reactor compared to the wood chars were related to the decreased mobility of potassium in the char matrix, leading to the less efficient catalytic effects of potassium on the bond-breaking and radical re-attachments. The high Si levels in the rice husk caused an increase in the char radical concentration compared to the wheat straw because the free radicals were trapped in a char consisting of a molten amorphous silica at heating rates of 10 3 e10 4 K s À1. The experimental electron spin resonance spectroscopy spectra were analyzed by fitting to simulated data in order to identify radical types, based on g-values and line widths. The results show that at high temperatures, mostly aliphatic radicals (g ¼ 2.0026e2.0028) and PAH radicals (g ¼ 2.0027e2.0031) were formed.

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Section: Char Yieldmentioning

confidence: 94%

Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures

Trubetskaya

Jensen

et al. 2016

Biomass and Bioenergy

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“…The lower char yield at high temperatures may be explained by several factors. Higher heating rates are known to induce lower char yields [18]. Moreover, volatile and char formation are two parallel reactions, and the latter is probably favored at higher temperatures and higher heating rates.…”

Section: Microscopic Analysis Of the Biochar Surfacesmentioning

confidence: 99%

Biomass Chars: The Effects of Pyrolysis Conditions on Their Morphology, Structure, Chemical Properties and Reactivity

et al. 2017

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Solid char is a product of biomass pyrolysis. It contains a high proportion of carbon, and lower contents of H, O and minerals. This char can have different valorization pathways such as combustion for heat and power, gasification for Syngas production, activation for adsorption applications, or use as a soil amendment. The optimal recovery pathway of the char depends highly on its physical and chemical characteristics. In this study, different chars were prepared from beech wood particles under various pyrolysis operating conditions in an entrained flow reactor (500-1400 • C). Their structural, morphological, surface chemistry properties, as well as their chemical compositions, were determined using different analytical techniques, including elementary analysis, Scanning Electronic Microscopy (SEM) coupled with an energy dispersive X-ray spectrometer (EDX), Fourier Transform Infra-Red spectroscopy (FTIR), and Raman Spectroscopy. The biomass char reactivity was evaluated in air using thermogravimetric analysis (TGA). The yield, chemical composition, surface chemistry, structure, morphology and reactivity of the chars were highly affected by the pyrolysis temperature. In addition, some of these properties related to the char structure and chemical composition were found to be correlated to the char reactivity.

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“…Hansen et al [63] reported that the stems of wheat straw contain more lignin and xylan compared to leaves. Trubetskaya et al [64] suggested that at fast heating rates the formation of metaplast is mostly affected by the bond-breaking and cross-linking of organic components present in lignin that are less volatile than holocelluloses.…”

Section: Tablementioning

confidence: 99%

Comparison of high temperature chars of wheat straw and rice husk with respect to chemistry, morphology and reactivity

Trubetskaya

Jensen

et al. 2016

Biomass and Bioenergy

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Si solid-state NMR Entrained flow reactor Oxygen reactivity Si bearing compounds a b s t r a c t Fast pyrolysis of wheat straw and rice husk was carried out in an entrained flow reactor at hightemperatures (1000e1500) C. The collected char was analyzed using X-ray diffractometry, N 2 -adsorption, scanning electron microscopy, particle size analysis with CAMSIZER XT, 29 Si and 13 C solid-state nuclear magnetic resonance spectroscopy and thermogravimetric analysis to investigate the effect of inorganic matter on the char morphology and oxygen reactivity. The silicon compounds were dispersed throughout the turbostratic structure of rice husk char in an amorphous phase with a low melting temperature (z730 C), which led to the formation of a glassy char shell, resulting in a preserved particle size and shape of chars. The high alkali content in the wheat straw resulted in higher char reactivity, whereas the lower silicon content caused variations in the char shape from cylindrical to near-spherical char particles. The reactivities of pinewood and rice husk chars were similar with respect to oxidation, indicating less influence of silicon oxides on the char reactivity.

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Influence of fast pyrolysis conditions on yield and structural transformation of biomass chars

Cited by 100 publications

References 47 publications

Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures

Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures

Biomass Chars: The Effects of Pyrolysis Conditions on Their Morphology, Structure, Chemical Properties and Reactivity

Comparison of high temperature chars of wheat straw and rice husk with respect to chemistry, morphology and reactivity

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