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The structural evolution of SF-soot (derived from the rapid pyrolysis of ShenFu bituminous coal) and a carbon black (Printex) was performed for air oxidation at 1273 and 1473 K. The morphology and nanostructure transformations were examined at conversion fractions ~0.2, 0.4, 0.6, and 0.8. Three modes of behavior were evident. The behavior of SF-soot followed an internal oxidation model (IOM) at 1273 K. The oxygen was able to fully permeate into the particle core, producing a sphere with variable removal of the interior structure with conversion. However, at the higher temperature, the SF-soot formed a concentric spherical structure with gradual consumption of the inner sphere due to restricted oxygen penetration. The fragmentation of hollow interior particles, on which the available literature is not extensive , was observed from HRTEM and SEM micrographs for the first time. During the oxidation of SF-soot, micropores were mainly generated during the 0–0.2 conversion, while the mesopore surface rapidly increased during the 0.6–0.8 conversion. The X-ray diffraction (XRD) patterns and Raman spectra both show that the oxidation of SF-soot is mainly a disordering process. The graphitic microcrystals were mainly consumed along the longitudinal orientation during the 0–0.2 conversion but were mainly consumed along the horizontal during the 0.4–0.8 conversion. The true densities of SF-soot and carbon black initially increase and then decrease monotonically during oxidation. [ABSTRACT FROM AUTHOR]

Abstract The present work aims to investigate the effects of a CO 2 -rich atmosphere on the characteristics of coal-derived soot. The rapid pyrolysis of Shenfu bituminous coal was conducted in a Drop tube furnace (DTF) in N 2 and CO 2 atmospheres with a wall temperature of 1073–1473 K and residence time below 700 ms. The yields and microstructure characteristics of N 2 -soot and CO 2 -soot were analysed by using a series of techniques (elemental analysis, HRTEM, Raman, XRD, FT-IR and thermogravimetry techniques). CO 2 enhanced the soot formation and proceeded the dehydrogenation. CO 2 improved the order of internal carbon lattices, enhanced the lateral extension of carbon nanostructures, decreased the interplanar spacing of the graphene layers and also promoted the stack of polyaromatic layers. The variations of the SOLO, DUO, TRIO and QUARTO structures were also analysed, and the contribution of CO 2 was found to reduce the defects of the basic structure units (BSU). The defects of soot were an important indication of the initial gasification reactivity. Overall, CO 2 -soot was more mature and low active than N 2 -soot. [ABSTRACT FROM AUTHOR]

In this study, an upgrading process of lignite with supercritical CO 2 extraction under rather mild temperatures was studied as a possible method for producing clean solid fuel with less moisture and enhanced combustion reactivity. The fractal characteristics and reactivity evolution of two typical lignites during the upgrading process by supercritical CO 2 extraction have been studied in present work. Two typical lignites and one subbituminous coal were extracted in different conditions by a semi-continuous supercritical CO 2 extraction device and the evolution of coal pore structure was investigated by N 2 and CO 2 adsorption/desorption isotherms. Two fractal dimensions D 1 and D 2 , at relative pressures 0–0.45 and 0.45–1, respectively, were calculated by the Frenkel-Halsey-Hill model. The combustion reactivity of raw and upgraded coals was studied by a thermogravimetric analyzer. The results indicate that the N 2 quantity adsorbed in pores of upgraded lignite increases with the increase of extraction time and temperature which is consistent with the variation of specific surface area and total pore volume of upgraded lignite. The mesopores and micropores of upgraded HB lignite are developed whereas macropores and mesopores of upgraded ZT lignite are enlarged after supercritical CO 2 extraction. It was found, D 1 values of upgraded HB lignite decrease whereas D 2 values increase slightly. Meanwhile, the D 1 and D 2 values of upgraded ZT lignite are all decreased. The D 1 values are mainly affected by the influence of mesopores and macropores on specific surface area and D 2 values are mainly affected by the effects of fine mesopores and micropores on total pore volume. We found that D 1 values have a positive relationship with the average pore diameter whereas have a negative relationship with specific surface area and total pore volume. D 2 values have a negative relationship with average pore diameter whereas have a positive relationship with specific surface area and total pore volume for the raw and upgraded lignite. The combustion reactivity of upgraded lignite is enhanced after supercritical CO 2 extraction due to the improvement of specific surface area and total pore volume. [ABSTRACT FROM AUTHOR]

Fine particles formed during pyrolysis are the precursors of particulate matters (PM) after combustion and/or gasification. This study aims to conduct a preliminary research on the characteristics of fine particles. The rapid pyrolysis of raw and acid-washed biomass was conducted in a drop tube furnace (DTF) with a wall temperature 1073–1473 K and varied residence times. Components of fine particles formed during rapid pyrolysis were determined by investigating their morphologies and element contents. Particle size distributions (PSDs) of fine particles were also measured by granulometry technique. The results showed that the yields of fine particles increased significantly with increasing pyrolysis temperature. PSDs of fine particles formed at different conditions varied from each other, and trimodally distribution was identified for fine particles derived from pyrolysis of raw biomass at 1473 K. Those independent fine particles consisted of abundant small fragments, and slight soot and ash particles. The size of soot and melting ash particles increased with residence time and temperature, and the size ranges of small fragments broadened as residence time increased. [ABSTRACT FROM AUTHOR]

In this study, the drying characteristics and kinetics of two typical lignites were investigated by using supercritical carbon dioxide (SCCO 2 ) at mild temperature (62–102 °C). The drying characteristics results show that SCCO 2 extraction drying has advantages over conventional drying such as better heat transfer and faster diffusion rate. Seven previous thin-layer models and a new proposed model were applied to analyze the lignite drying kinetics, and the proposed model obtained the best fit to the lignite drying process in all of the models. Apparent diffusion coefficients of moisture in SCCO 2 drying are higher compared with conventional drying method. The activation energies for the diffusion process of two typical lignites are 10.5561 and 11.6218 kJ/mol, which are far lower in comparison to conventional drying process. The pore structure and gasification reactivity of drying lignite were analyzed and both of them have an obvious improvement after the SCCO 2 drying process. [ABSTRACT FROM AUTHOR]

In our study, not only the P-QRS-T waves but also the micro-wavelets before QRS complex (in P wave and PR segment) and after QRS complex (ST segment and upstroke of T wave) were first to be identified on surface electrocardiogram in human by the "new electrocardiogram" machine (model PHS-A10) according to conventional 12-lead electrocardiogram connection methods. By comparison to the conventional electrocardiogram in 100 cases of healthy individuals and several patients with arrhythmias, we have found that the wavelets before P wave theoretically reflected electrical activity of sinus node and the micro-wavelets before QRS complex may be related to atrioventricular conduction system (atrioventricular node, His bundle and bundle branch) potentials. Noninvasive atrioventricular node and His bundle potential tracing will contribute to differentiation of the origin of wide QRS and the location of the atrioventricular block. We also have found that the wavelets after QRS complex may be associated with phase 2 and 3 repolarization of ventricular action potential, which will further reveal ventricular repolarization changes. [ABSTRACT FROM AUTHOR]

• Evolution of morphology and nanostructure of soot and carbon black during CO 2 gasification were investigated. • Three gasification modes were observed for soot and carbon black. • Here soot nanostructure transformed from ordered to less ordered during gasification. • The conversion took place both on the surface and within the core after pore formation and expansion. • The crystallites were preferentially consumed along the graphitic edges for coal-derived soot. The morphology and nanostructure evolution during gasification was examined for a coal-derived soot and, to permit comparisons to other research, two carbon black samples. The investigation examined four different conversion extents at 1273 and 1473 K. The primary particle diameter decreased significantly during the initial stage and then changed slowly. The gasification behavior varied with the initial nanostructure and treatment temperature. At 1273 K the consumption behavior followed a hybrid mode comprised of shrinking core and homogeneous reaction models. However, at 1473 K, a previously unobserved gasification behavior occurred with the soot forming concentric spheres. Here the gasification progressed by initially forming micropores, followed by insufficient permeation of oxidant with the subsequent consumption of the core, ultimately forming hollow particles. Raman spectra and X-ray diffraction patterns indicated there was a transformation from initially ordered to less well-ordered structure. Partial gasification induced disordering to different extents, accompanied by a slight maturing associated with thermal annealing. The crystallites were preferentially consumed along the graphitic edges for coal-derived soot. At the start of gasification, the density of the soot increased but subsequently declined. Abundant micropores with multimodal distributions were newly generated and continually developed during gasification. [ABSTRACT FROM AUTHOR]

• The rapid hydropyrolysis behavior of pulverized bituminous coal in a drop-tube furnace (DTF) was studied. • Hydrogen significantly improved the yield of methane when the temperature was below 900 °C. • Hydropyrolysis increased the content of naphthalene in tar and promoted the degree of lightening of tar. • Hydropyrolysis at 950 °C resulted in low graphite content char suitable for gasification. • The char from hydropyrolysis has a higher condensation degree structure and higher saturation. This paper aims to investigate the hydropyrolysis behavior of pulverized bituminous coal in a drop-tube furnace (DTF) with a temperature of 800–1000 °C. The effects of temperature and hydrogen on the compositions (gases and tar) and the structure of products (char) were investigated. Hydropyrolysis between 800 and 1000 °C resulted in a high yield of methane, and tar production decreased with increasing temperature. Besides, the light components of tar, especially the naphthalene, were significantly increased with hydrogen. The methane yield firstly increased to a peak value of 72.83 ml/g(air-dried coal) at 900 °C and then decreased with increasing temperature during hydropyrolysis. Hydrogen significant improved the yield of gaseous hydrocarbon (C 2 H 2 , C 2 H 4 , and C 2 H 6) when the temperature below 900 °C, while rarely change that at a higher temperature. At the temperature above 900 °C, the content of graphite in the hydropyrolysis char was lower than that of pyrolysis char in nitrogen. The graphite contents in the char decreased to a minimum at 950 °C and then gradually increased with increasing temperature. The char from hydropyrolysis has a higher condensation degree structure and higher saturation. The small aromatic molecules transformed into large aromatic molecules with increasing temperature under both pyrolysis and hydropyrolysis. [ABSTRACT FROM AUTHOR]

In order to study the primary fragmentation behavior of coals and biomasses, experiments of rapid pyrolysis were carried out. This work focused on the devolatilization and fragmentation characteristics including the solid/gas yield, particle density/morphology, particle size and fragmental probability ( S f ). The effects of temperature, time and solid property were investigated. The viscous flow model was employed to characterize the pressure difference (Δ P ), which was considered as the driving force of diffusion and fragmentation. The Ohm principle was used to establish the linear relation of devolatilization rate and fragmentation rate. The result showed that temperature and time have positive contribution to the fragmentation. The occurrence of fragmentation was observed more apparently with the decreasing of the ash content in the biomass. The pressure difference has a positive correlation with the fragmental rate, which shows the validity of application Ohm principle in the prediction of fragmenting process. [ABSTRACT FROM AUTHOR]