“…During the coal gasification process, many intermediates are generated: part of intermediates are directly decomposed into small gaseous fragments through hydrolysis reaction; while, other large fragments of aromatics which contains strong bonding energy are converted into H 2 and CO 2 through heterogeneous reactions [ 55 ]. Sun et al [ 56 ] systematically studied the pathway of SCWG (as shown in Fig. 3 ), and found that the graphite-like structure, i.e., polycyclic aromatic hydrocarbons (PAH) generated during the heating process, is stable in SCW; thus, the gasification of PAH is the rate-controlling step to achieve the complete coal gasification in SCW.…”
Section: Poly-generation Based On Scwg Of Coal: Innovational Coal Uti...mentioning
confidence: 99%
“…3 ), and found that the graphite-like structure, i.e., polycyclic aromatic hydrocarbons (PAH) generated during the heating process, is stable in SCW; thus, the gasification of PAH is the rate-controlling step to achieve the complete coal gasification in SCW. To overcome the reaction barrier, Liu et al [ 57 ], Zhu et al [ 55 ], and Sun et al [ 56 ] further studied various homogeneous catalysts, and found that K 2 CO 3 is effective in promoting the coal hydrolysis and aromatics decomposition, and in suppressing the graphite-like PAHs’ production [ 56 ]. Fig.…”
Section: Poly-generation Based On Scwg Of Coal: Innovational Coal Uti...mentioning
Coal consumption leads to over 15 billion tons of global CO2 emissions annually, which will continue at a considerable intensity in the foreseeable future. To remove the huge amount of CO2, a practically feasible way of direct carbon mitigation, instead of capturing that from dilute tail gases, should be developed; as intended, we developed two innovative supporting technologies, of which the status, strengths, applications, and perspective are discussed in this paper. One is supercritical water gasification-based coal/biomass utilization technology, which orderly converts chemical energy of coal and low-grade heat into hydrogen energy, and can achieve poly-generation of steam, heat, hydrogen, power, pure CO2, and minerals. The other one is the renewables-powered CO2 reduction techniques, which uses CO2 as the resource for carbon-based fuel production. When combining the above two technical loops, one can achieve a full resource utilization and zero CO2 emission, making it a practically feasible way for China and global countries to achieve carbon neutrality while creating substantial domestic benefits of economic growth, competitiveness, well-beings, and new industries.
“…During the coal gasification process, many intermediates are generated: part of intermediates are directly decomposed into small gaseous fragments through hydrolysis reaction; while, other large fragments of aromatics which contains strong bonding energy are converted into H 2 and CO 2 through heterogeneous reactions [ 55 ]. Sun et al [ 56 ] systematically studied the pathway of SCWG (as shown in Fig. 3 ), and found that the graphite-like structure, i.e., polycyclic aromatic hydrocarbons (PAH) generated during the heating process, is stable in SCW; thus, the gasification of PAH is the rate-controlling step to achieve the complete coal gasification in SCW.…”
Section: Poly-generation Based On Scwg Of Coal: Innovational Coal Uti...mentioning
confidence: 99%
“…3 ), and found that the graphite-like structure, i.e., polycyclic aromatic hydrocarbons (PAH) generated during the heating process, is stable in SCW; thus, the gasification of PAH is the rate-controlling step to achieve the complete coal gasification in SCW. To overcome the reaction barrier, Liu et al [ 57 ], Zhu et al [ 55 ], and Sun et al [ 56 ] further studied various homogeneous catalysts, and found that K 2 CO 3 is effective in promoting the coal hydrolysis and aromatics decomposition, and in suppressing the graphite-like PAHs’ production [ 56 ]. Fig.…”
Section: Poly-generation Based On Scwg Of Coal: Innovational Coal Uti...mentioning
Coal consumption leads to over 15 billion tons of global CO2 emissions annually, which will continue at a considerable intensity in the foreseeable future. To remove the huge amount of CO2, a practically feasible way of direct carbon mitigation, instead of capturing that from dilute tail gases, should be developed; as intended, we developed two innovative supporting technologies, of which the status, strengths, applications, and perspective are discussed in this paper. One is supercritical water gasification-based coal/biomass utilization technology, which orderly converts chemical energy of coal and low-grade heat into hydrogen energy, and can achieve poly-generation of steam, heat, hydrogen, power, pure CO2, and minerals. The other one is the renewables-powered CO2 reduction techniques, which uses CO2 as the resource for carbon-based fuel production. When combining the above two technical loops, one can achieve a full resource utilization and zero CO2 emission, making it a practically feasible way for China and global countries to achieve carbon neutrality while creating substantial domestic benefits of economic growth, competitiveness, well-beings, and new industries.
“…This behavior can be further verified by the descending trend of the A G /A all ratio, taking into account that the G band is related to the vibrations of the ideal graphitic lattice. The lower degree of order in the surface structure of chars, compared to the raw lignite, could be attributed to the formation of molecular amorphous structures on the surface of chars due to the breakage of chemi-cal bonds in macromolecular compounds during the condensation stage of the pyrolysis process [53,56,61].…”
The presented work explores the structural properties, gasification reactivity, and syngas production of Greek lignite fuel (LG) and ex-situ produced chars during CO2 gasification. Three different slow pyrolysis protocols were employed for char production involving torrefaction at 300 °C (LG300), mild-carbonization at 500 °C (LG500), and carbonization at 800 °C (LG800). Physicochemical characterization studies, including proximate and ultimate analysis, X-ray Diffraction (XRD), and Raman spectroscopy, revealed that the thermal treatment under inert atmospheres leads to chars with increased fixed carbon content and less ordered surface structures. The CO2 gasification reactivity of pristine LG and as-produced chars was examined by thermogravimetric (TG) analysis and in batch mode gasification tests under both isothermal and non-isothermal conditions. The key parameters affecting the devolatilization and gasification steps in the overall process toward CO-rich gas mixtures were thoroughly explored. The gasification performance of the examined fuels in terms of carbon conversion, instant CO production rate, and syngas generation revealed an opposite reactivity order during each stage. TG analysis demonstrated that raw lignite (LG) was more reactive during the thermal devolatilization phase at low and intermediate temperatures (da/dtmax,devol. = 0.022 min−1). By contrast, LG800 exhibited superior gasification reactivity at high temperatures (da/dtmax,gas. = 0.1 min−1). The latter is additionally corroborated by the enhanced CO formation of LG800 samples under both non-isothermal (5.2 mmol) and isothermal (28 mmol) conditions, compared to 4.1 mmol and 13.8 mmol over the LG sample, respectively. The pronounced CO2 gasification performance of LG800 was attributed to its higher fixed carbon content and disordered surface structure compared to LG, LG300, and LG500 samples.
“…Among these, the H 2 yield produced from coal is the highest (21.24 million tons), accounting for 63.54%, followed by H 2 produced from by-product gas (7.08 million tons), natural gas (4.6 million tons), and electrolyzed water (0.5 million tons). However, the H 2 contributions from supercritical steam coal [8], photocatalytic water decomposition with solar energy [9], and biological H 2 production [10] are still in the research and developmental stage ( Table 1). Different raw materials yield large differences in the composition and impurity contents of H 2 produced using various technologies.…”
Section: Introductionmentioning
confidence: 99%
“…Thus, efficient H 2 purification technologies that enable the removal of impurities from H 2 and provide high-qualify H 2 for fuel cell vehicles are of the utmost importance for developing the H 2 fuel cell vehicle industry. ] is used as a medium that provides a homogeneous and high-speed reaction because of its special physical and chemical properties, so that the chemical energy of coal is directly and efficiently converted into hydrogen energy [8].…”
Nowadays, we face a series of global challenges, including the growing depletion of fossil energy, environmental pollution, and global warming. The replacement of coal, petroleum, and natural gas by secondary energy resources is vital for sustainable development. Hydrogen (H2) energy is considered the ultimate energy in the 21st century because of its diverse sources, cleanliness, low carbon emission, flexibility, and high efficiency. H2 fuel cell vehicles are commonly the end-point application of H2 energy. Owing to their zero carbon emission, they are gradually replacing traditional vehicles powered by fossil fuel. As the H2 fuel cell vehicle industry rapidly develops, H2 fuel supply, especially H2 quality, attracts increasing attention. Compared with H2 for industrial use, the H2 purity requirements for fuel cells are not high. Still, the impurity content is strictly controlled since even a low amount of some impurities may irreversibly damage fuel cells’ performance and running life. This paper reviews different versions of current standards concerning H2 for fuel cell vehicles in China and abroad. Furthermore, we analyze the causes and developing trends for the changes in these standards in detail. On the other hand, according to characteristics of H2 for fuel cell vehicles, standard H2 purification technologies, such as pressure swing adsorption (PSA), membrane separation and metal hydride separation, were analyzed, and the latest research progress was reviewed.
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