A study of the mechanism of the rapid pyrolysis of single particles of coal

In this study, the aim was to obtain high bio-oil yields in a fixed bed tubular reactor at various pyrolysis temperatures, reaction times, sweeping gas velocities, particle sizes, and heating rates. In order to improve heat and mass transfer, a stainless steel basket was used. The raw material, olive residue, was placed into the reactor in two different ways: directly and with a stainless steel mesh basket. It was proved that employment of the basket provided an effective heat transfer between the sample and reactor wall. As a consequence, higher volatile yields were observed. The maximum oil yield was achieved as 46.72% with a particle size of 0.85 < D p < 0.45 mm, heating rate of 500 °C min -1 , pyrolysis temperature of 500 °C, and sweeping gas flow rate of 400 cm 3 min -1 . It was concluded that reducing the residence time of evolved volatiles, minimizing the particle size, increasing the heating rate at a pyrolysis temperature of 500 °C, and improving the contact surface of raw material with the reactor wall caused enhancement of mass and heat transfer through the system. Compositions of bio-oils were determined in detail with various chromatographic and spectroscopic methods. These results show that the composition of bio-oil is quite similar to that of crude oil.

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“…Particle size may also affect the course of devolization since the rate may now be transport controlled at high heating rates …”

Section: Resultsmentioning

confidence: 99%

Rapid Pyrolysis of Olive Residue. 1. Effect of Heat and Mass Transfer Limitations on Product Yields and Bio-oil Compositions

Uzun

Pütün

2007

Energy Fuels

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“…1,5−7 Because the radical fragments and their reaction products may crack further, 8 the two-step reactions take place successively and concurrently, which makes it difficult to distinguish them and study each step experimentally. 9 Despite this complexity, it is certain that the main factors that influence the quantity and quality of the tars produced in coal pyrolysis are two: (1) the temperature at which the weak covalent bonds in coal crack and (2) the reaction temperature and time of the volatile radical fragments and their products. Studies have shown that the cracking of the covalent bond in coal is mainly temperature-dependent and not significantly influenced by the heating rate.…”

Section: Introductionmentioning

confidence: 99%

“…The first step is thermal cracking of weak covalent bonds in coal to form volatile radical fragments. The second step is reaction of the volatile radical fragments (including coupling and condensation) to produce pyrolysis products, such as gas, tar, and char. ,− Because the radical fragments and their reaction products may crack further, the two-step reactions take place successively and concurrently, which makes it difficult to distinguish them and study each step experimentally . Despite this complexity, it is certain that the main factors that influence the quantity and quality of the tars produced in coal pyrolysis are two: (1) the temperature at which the weak covalent bonds in coal crack and (2) the reaction temperature and time of the volatile radical fragments and their products.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Tars Produced in Pyrolysis of Four Coals under Various Conditions in a Viewpoint of Radicals

Liu

et al. 2015

Energy Fuels

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Many studies tried to correlate coal pyrolysis conditions with reactivity of tars produced, but few analyzed the radical concentration of tars. This work studies pyrolysis of four coals, with carbon contents in a range of 74−82 wt %, in a fixedbed tubular reactor at three heating rates and three N 2 -purging rates. The changes in the radical concentration of tars under various conditions, such as in solvents (hexane or tetrahydrofuran) or at high temperatures (300, 350, 400, and 450°C), are analyzed. The effect of pyrolysis conditions on the radical concentration of tars is ascribed to the temperature difference between the gas phase and the coal in the reactor, which results in further cracking of tars. The difference in the radical concentration in tars obtained from pyrolysis of different coals is elaborated in a viewpoint of the coal structure and pyrolysis mechanism.

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“…Tominaga et al, 1997 2.02 × 10 3 3.11 × 10 7 1.2 3Solomon et al, 1983 4.5 × 10 13 2.20 × 10 8 1.54Johnson et al, 1988 1.0 × 10 13 1.8 × 10 8 1.8…”

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confidence: 99%

Coal Particle Devolatilization and Soot Formation in Pulverized Coal Combustion Fields

Hashimoto

Hayashi

2021

KONA

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In this paper, recent developments of the devolatilization model and soot-formation model for the numerical simulations of pulverized-coal combustion fields, and the technology used to measure soot particles in pulverizedcoal combustion fields are reviewed. For the development of new models, the validation of the developed models using measurement is necessary to check the accuracy of the models because new models without validation have a possibility to make large errors in simulations. We have developed the tabulated devolatilization process model (TDP model) that can take into account the effect of particle heating rate on the volatile matter amount and the devolatilization-rate parameters. The accuracy of the developed TDP model was validated by using the laser Doppler velocimetry data for the bench-scale coal combustion test furnace. The soot-formation model combined with TDP model for the large eddy simulation (LES) has been also developed. The spatial distributions of both the soot-volume fraction and the polycyclic aromatic hydrocarbons were measured by virtue of laser-induced incandescence (LII) and laser-induced chemiluminescence (PAHs-LIF). The accuracy of the developed sootformation model was validated by using the measured data.

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A study of the mechanism of the rapid pyrolysis of single particles of coal

Cited by 23 publications

References 12 publications

Rapid Pyrolysis of Olive Residue. 1. Effect of Heat and Mass Transfer Limitations on Product Yields and Bio-oil Compositions

Rapid Pyrolysis of Olive Residue. 1. Effect of Heat and Mass Transfer Limitations on Product Yields and Bio-oil Compositions

Analysis of Tars Produced in Pyrolysis of Four Coals under Various Conditions in a Viewpoint of Radicals

Coal Particle Devolatilization and Soot Formation in Pulverized Coal Combustion Fields

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