Solvent Extraction of Superfine Pulverized Coal. Part 2. Free-Radical Characteristics

To better explore coal macromolecular models from the extraction aspects, the behaviors of free radicals during the solvent extraction of superfine pulverized coal were studied. The electron paramagnetic resonance (EPR) method was employed to characterize the extracts and extraction residues (ERs) from the pyridine (PY) and tetrahydrofuran (THF) extraction processes. The EPR parameters of different paramagnetic centers were analyzed through the peak deconvolution, and the detailed extraction mechanisms were discussed. The result suggests that the particle size and polarity of the reagent have the combined influences on the free-radical characteristics during the extraction process. Compared to the raw coals (rcs), the free-radical concentrations of the ER show a similar level, while these are 1 order of magnitude lower for the extracts (about 6 to 9% of rcs). In addition, PY with higher polarity is prone to attack the non-covalent interactions like hydrogen bonds, which can extract more abundant molecule components connected by charge-transfer forces, resulting in 35.42% higher spin concentrations compared to the THF extracts. On the other hand, THF with an affinity with oxygen-containing groups can loosen the coal structure, which extracts more stable oxygenated compounds. In addition, THF can effectively target the π–π interactions, and the paramagnetic centers on these aromatic clusters can be better preserved due to the steric hindrance effect. The study sheds light on better elucidation of coal macromolecular structures, which provides support on better understanding coal pyrolysis and liquefaction behaviors

NO Emissions from Oxidizer-Staged Combustion of Superfine Pulverized Coal in the O₂/CO₂ Atmosphere

The CO₂ control technologies have been studied extensively in recent years, among which the oxy-fuel combustion shows a vast number of advantages to be explored commercially in the near future. However, unexpected problems, such as bad combustion characteristics and serious slagging and depositing issues, show up with the replacement of N₂ by CO₂. These inherent disadvantages in normal O₂/CO₂ combustion can be restrained via combining the superfine pulverized coal and oxy-fuel combustion technology. The axial NO emission characteristics of this new technology were focused here. The effects of the oxidizer staging were also studied in detail. Results indicate that the axial NO emissions of the unstaged O₂/CO₂ combustion basically showed “M” type of distributions along the furnace. The “M” type can be divided into the main homogeneous and heterogeneous reaction zones. The oxidizer-staged O₂/CO₂ combustion can mitigate NO emissions effectively. Coals with smaller particle sizes and higher volatiles are more advantageous for eliminating NO in the staged O₂/CO₂ combustion technology. The superfine pulverized coal used with certain low NO combustion technologies shows significant superiority in both combustion performance and NO abatement

Additional file 1 of De novo assembly of the complete mitochondrial genome of pepino (Solanum muricatum) using PacBio HiFi sequencing: insights into structure, phylogenetic implications, and RNA editing

Supplementary Material