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In order to understand the reaction mechanism of lignin pyrolysis, the pyrolysis process of guaiacol (o-methoxyphenol) as a lignin model compound was studied by free radical detection technology (electron paramagnetic resonance, EPR) in this paper. It was proven that the pyrolysis reaction of guaiacol is a free radical reaction, and the free radicals which can be detected mainly by EPR are methyl radicals. This paper proposes a process in which four free radicals (radicals 1- C6H4(OH)O*, radicals 5- C6H4(OCH3)O*, methyl radicals, and hydrogen radicals) are continuously rearranged during the pyrolysis of guaiacol. [ABSTRACT FROM AUTHOR]

An experimental-scale electrostatic precipitator (ESP) was built to investigate the influence of temperature and gas media on collection efficiency and energy consumption. High temperature was harmful to the performance of the ESP and had a considerable influence on large particles. The maximum collection efficiency was lower and energy consumption was higher under coal pyrolysis gas media than under air. Two improvement methods, namely, gas media conditioning and positive polarity power supply, were studied in this work. Both methods can improve the performance of high-temperature ESP under coal pyrolysis gas media. The improvement in collection efficiency under the effect of gas conditioning decreased and that under the effect of a positive power supply increased with the increase in temperature. Gas conditioning and positive power supply increased the maximum collection efficiencies of the ESP at 600 °C under coal pyrolysis gas media by 3.0% and 11.8%, respectively. Unlabelled Image • High temperature was harmful to the performance of the ESP. • The performance of ESP in coal pyrolysis gas is inferior to that in air. • Gas conditioning and positive power supply can improve the performance of ESP. [ABSTRACT FROM AUTHOR]

In this study, the effects of coal blending ratio, pyrolysis temperature, pyrolysis atmosphere and coal particle size on the quality of pyrolyzed char were investigated via a combination of orthogonal experimental design and grey relational analysis. Coal-XG and Coal-LL were pyrolyzed under various conditions to produce chars which were characterized to ascertain their properties such as chemical structure and reactivity. The results indicated that the pyrolysis temperature has the most significant impact on the quality of the char, followed by the pyrolysis atmosphere, coal blending ratio and coal particle size. The increase in pyrolysis temperature not only diminished char yield but also accelerated the consumption of oxygen-containing functional groups and the polycondensation of small aromatic ring structures throughout the reaction process. This led to a reduction in the reactivity of pyrolyzed char and the establishment of a more ordered structure. Meanwhile, the involvement of CO 2 and H 2 O prevented the condensation of small aromatic rings and fostered the generation of additional oxygen-containing functional groups, which resulted in lower yield and higher reactivity of the char under these two atmospheres. Through systematic analysis, only the Raman characteristic parameter I (Gr+VL+Vr) /I D exhibited a strong positive linear correlation with char reactivity, making it a reliable indicator for characterizing the reactivity of char. • The orthogonal design was used to study four response factors. • GRA was used to find optimal conditions and impact ranking of different factors. • Linear regression was applied to relate Raman/FTIR parameters to reactivity. • Blend experiments were conducted with two coking coals. [ABSTRACT FROM AUTHOR]

In this study, the effect of pressure on the pyrolysis characteristics of Naomaohu coal and the physicochemical properties of char during slow pyrolysis is evaluated, and the mechanism of pressure is explored. The results show that the influences of pressure on char yield and physical properties are reflected in both promoting and inhibiting effect, and the latter is more obvious with the increasing temperature. As the pressure increases, the char yield first reduces and then improves, and at 600 °C and 800 °C the minimum yields are in 1.0 MPa and 0.1 MPa, which are 57.48% and 54.04%, respectively. The S BET of char increases first and then decreases. At 800 °C, the S BET of char increases from 7.86 m2/g at 0.1 MPa to 19.81 m2/g at 0.5 MPa and then decreases. The effect of pressure on the chemical properties of char is relatively simple. As the pressure rises, the content of functional groups in char reduces and the degree of graphitization enhances. The TG-DTG curve, XPS, BET, SEM test, experiments on the pressurized micro-fluidized bed reaction analyzer and pressurized pyrolysis-gas chromatography/mass spectrometry show that the pressure mainly affects the pyrolysis process by affecting the secondary reaction of the primary volatiles in the particle and is related to temperature. • The effect of pressure on pyrolysis process has two kinds of promotion and inhibition. • The inflection pressure point from promotion to inhibition is regulated by temperature. • As the pressure increases, the char yield and S BET both rise first and then decrease. • The graphitization degree of char is deepened with pressure. • Pressure mainly affects the pyrolysis process by affecting the secondary reaction of tar. [ABSTRACT FROM AUTHOR]

In order to investigate the pressurized isothermal pyrolysis characteristics of coal, the effect of pressure on gas release characteristics and the kinetics of pressurized isothermal pyrolysis are explored for the first time in a pressurized micro-fluidized bed reaction analyzer (P-MFBRA). This work finds that the yields of CO 2 , CO, CH 4 , and H 2 increases with temperature and pressure. The difference in the order of gas-releasing reduces as temperature and pressure rises, but that of gas-ending first decreases and then increases with pressure. The most probable mechanism functions of CO 2 , CO and CH 4 change from shrinking core model to homogeneous model at 1 MPa, 0.8 MPa and 0.5 MPa, respectively, showing that reaction is controlled by chemistry under low pressure but affected by diffusion effect with elevating pressure. The rate constant and activation energy (Ea) of each gas appear an increasing-decreasing tendency and the difference between Ea of each gas reduces with pressure. Compared with non-isothermal experiments, the Ea (20.8–475 kJ mol−1) and pre-exponential factor in P-MFBRA are less than those (70–150 kJ mol−1) in the pressurized thermogravimetric analyzer (P-TGA), indicating P-MFBRA can effectively reduce the diffusion inhibition, and the kinetics obtained is close to the reaction in industrial fluidized bed reactor. [Display omitted] • The effect of pressure on gas formation is inconsistent at different temperatures. • It is affected by chemistry but diffusion at low and high pressure respectively. • The activation energy appears an increasing-decreasing trend with pressure. • Pressurized micro-fluidized bed can reduce the diffusion inhibition of reaction. • Pressurized isothermal pyrolysis is first done in pressurized micro-fluidized bed. [ABSTRACT FROM AUTHOR]