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[Display omitted] • A soot formation mechanism of the NC-POX process is proposed. • The O 2 /CH 4 ratio should be greater than 0.6 to reduce soot generation. • The evolution of polycyclic aromatic hydrocarbon in precursor was analyzed in detail. • The increase in the O 2 /CH 4 ratio reduces the graphitization degree of soot. Non-catalytic partial oxidation (NC-POX) process is a promising technology for hydrogen and syngas production, but the generation of soot hinders its development. In this study, the yields of soot and its precursors under different working conditions are quantified by experiments. When the O 2 /CH 4 ratio is more than 0.6, the soot yield can be controlled below 1.07% from 2.53%. The soot precursor evolution mechanism in NC-POX is analyzed through the quantification of polycyclic aromatic hydrocarbon (PAH) compounds. It is found that hydrogen abstraction vinyl radical addition (HAVA*) and methyl addition cyclization (MAC) are the main growth pathways of PAHs. The concentrations of H 2 O, CO 2 , and oxygenated hydrocarbons increase with O 2 /CH 4 , which further inhibit the soot generation reactions and reduce the degree of graphitization of soot particles through surface reactions. A soot formation mechanism is proposed. This study provides a quantified reference for soot modeling and the elimination of soot in industry. [ABSTRACT FROM AUTHOR]

• Gasification phenomena of raw PKS, torrefied PKS, and steam-CO 2 are studied. • Euler-Lagrangian two-dimensional CFD model is used to investigate tar formation by modeling all components in tar together. • The gasification efficiency of torrefied-PKS is up by 29.1 % as compare to the raw-PKS. • The S-CO 2 -R and gasification temperature reduced tar concentration by 21.4 % and 20.5 % respectively. Experimental and numerical evaluation of steam and carbon dioxide gasification on torrefied palm kernel shell in an updraft fixed bed gasifier is studied. Euler-Lagrangian two-dimensional model with 15 kinetic reactions is developed to investigate tar formation in relation to torrefaction temperature, gasification temperature, and steam-to-carbon-dioxide ratio (S-CO 2 -R). The combination of steam and CO 2 had considerable effect on the tar reduction and also influenced the gaseous composition significantly when the varying parameters were compared. The results show that increasing both gasification temperature and S-CO 2 -R do enhance the H 2 production whiles drastically reducing the tar formation. The tar concentration reduced by 21.4 % and 20.5 % by changing the S-CO 2 -R from 0.4 to 2.0 and gasification process temperature from 973 and 1173 K respectively. An increase in hydrogen is also observed, from 55.5 % to 60.84 %, when the S-CO 2 -R is increased to 1.2. Similarly, 29.1 % increase is observed in gasification efficiency as compared to the raw-PKS. [ABSTRACT FROM AUTHOR]

• Carbon structure in thermochemical conversion of coal is characterized in-situ. • Transition mechanism between amorphous carbon and aromatic carbon is clarified. • Oxygen-containing functional groups are active sites for low temperature oxidation reactions. Thermal conversion is pivotal for clean and efficient coal utilization. Evolution of solid structure profoundly affects the gasification mechanism. However, in-situ study on coal structure evolution during gasification is limited. In this study, in-situ Raman spectroscopy was used to investigate the carbon structure evolution during thermal conversion. Results revealed two stages in coal pyrolysis: polycondensation and aromatic ring fusion. During polycondensation, numerous side chain groups break, while aromatic compounds condensed and rings fused in the aromatic ring fusion stage, increasing molecular size. In char gasification, larger particles required more time to achieve stable shrinkage, thus delaying coal char graphitization process. Low temperature oxidation led to decreased order due to oxygen-containing structure formation, evolving into a graphite-like structure as disordered carbon diminished. In addition, oxygen-containing groups acted as active oxidation sites. The insights into real-time structure evolution enhance understanding of the particle behavior during thermal conversion of coal. [ABSTRACT FROM AUTHOR]

• Impinging flame of multiple diesel jet in gasifier was investigated. • Dynamic Mode Decomposition was applied to high-speed image sequences. • The dominant oscillation structure in the impinging zone was determined. • Two different combustion patterns caused by impinging effect were revealed. • A significant large-scale entrainment behavior occurs in the impinging zone. Impinging can improve the combustion efficiency of industrial processes. However, studies on the impinging characteristics of multiple jet flames are lacking. In this study, based on an opposing multi-burner gasifier with diesel fuel, the combustion oscillation characteristics in the impinging zone of a four-burner impinging flame were investigated. The dominant oscillation structure in the impinging zone was obtained by applying the Dynamic Mode Decomposition (DMD) algorithm, and the DMD mode and frequency spectral distribution was compared with those under the two-burner impinging condition. Differences in combustion patterns were determined between the two- and four-burner impinging flames. The most intense oscillation was not in the impinging center of the four-burner impinging flame but in the outer annular zone. This study provides valuable information for the structural characterization and impinging enhancement effects of turbulent flames. [ABSTRACT FROM AUTHOR]

• The flow uniformity of large-sized PEMFC was improved with an optimized distribution zone. • Partially dotted matrix can achieve both improved uniformity and reduced manufacturing cost. • Positional and size effects of partially dotted matrix were clarified. Proton exchange membrane fuel cell (PEMFC) is an important device to convert clean-fuel hydrogen into electricity, which has the potential to reduce pollutant emission and our dependence on fossil fuels. Of the many development and manufacturing challenges that need to overcome before large-scale commercialization can be realized, one of the most pivotal ones is flow distribution uniformity. To this end, a distribution zone with partially dotted matrix was proposed, and showed much more effectiveness when compared with the un-optimized distribution zone with an empty chamber. The positional and size effect of the dotted matrix was investigated, and results showed that flow uniformity was maximized when the dotted matrix was placed near the gas inlet. Interestingly, less dotted matrix size could achieve better performance, indicating the potential of this approach to reduce manufacturing cost. The optimized system could achieve more uniform flow with standard deviation of 1.808 × 10-8, maldistribution factor of 3.967 × 10-3 and variable coefficient of 0.4143%, more superior to other similar models reported. Furthermore, a full cell-level simulation was also conducted, affirming the superiority of the proposed model with increased power densities and water distribution uniformities. [ABSTRACT FROM AUTHOR]

• Particle flow behaviors in gasifier were studied with an advanced visualization system. • Statistical analysis of the particle trajectory distribution was presented. • The particle trajectories and PSD were obtained by image processing algorithm. • Particle velocity was analyzed based on the obtained particle trajectories. Based on the bench-scale opposed multi-burner (OMB) coal water slurry (CWS) entrained-flow gasifier, the particle flow behaviors during atomization in the jet zone and non-jet zone of the gasifier were investigated with advanced visualization apparatus. The particle trajectories and particle size distribution were analyzed with particle tracking algorithm and statistical analysis. The particle trajectories in the jet zone indicate that the motions of particles are simple straight lines. And particle flow behaviors in the jet zone can be divided into three types: rotation, deformation, and fragmentation. However, the particle trajectories in the non-jet zone indicate that the particle motion directions present irregular and are unevenly distributed. Statistical analysis of the particle trajectories shows the proportion of particle trajectories in the non-jet zone is larger than that in the jet zone. And with the increase of O/C ratio, the proportion of particle trajectories distributed in jet zone decreases. [ABSTRACT FROM AUTHOR]