Single-particle coal ignition and alkali metal radiation characteristics based on optical diagnosis technology

Study on the ignition characteristics of coal is the theoretical basis for realizing the high-efficient and clean utilization of coal. The alkali metals such as K and Na in coal are released into the gas phase during combustion and enter the system, which can easily cause high temperature corrosion of the reactor, fouling of the heating surface and slagging in the furnace. Based on the single-particle coal ignition detection platform, the ignition and alkali metal Na* and K* radiation characteristics of single-particle Yangchangwan (YCW) bituminous coal and Naomaohu (NMH) lignite during combustion were investigated under different oxygen volume flow rates. High-speed camera technology was used to capture the flame evolution process during single-particle coal ignition, and hyperspectral imaging technology was used to measure the spontaneous emission spectra of alkali metals Na* and K* in the flame to obtain the spatial release behavior of alkali metals. The results show that the ignition process of different types of coal is different. The enveloping flame is formed in the combustion process of volatile matter in the YCW coal particles, while the ignition reaction of the NMH coal is more intense without enveloping phenomenon due to its high volatile matter content, and the flame brightness in the whole ignition process is stronger than that of the YCW coal. The increase of oxygen can promote the ignition of coal particles, with the increase of oxygen volume flow, the ignition delay time of the YCW coal and the NMH coal decreases, and the ignition delay time of the NMH coal is smaller than that of the YCW coal. When the fire occurs, the flame brightness is the brightest, and the flame shape is relatively smooth and stable. The radiation characteristics of alkali metals Na* and K* in single-particle YCW coal and NMH coal during ignition and combustion are different from that in coke combustion process, in which the radiation intensity of Na* and K* is the strongest. Na* has a release peak both in the volatile reaction process and coke reaction process, but K* radiation intensity does not have an obvious release peak in the volatile reaction process and coke combustion process. When oxygen content increases, the release time of alkali metals from the YCW coal and the NMH coal is gradually advanced, and the beginning time of alkali metal radiation from the NMH coal is less than that from the YCW coal. In addition, the analysis of the ignition process of single-particle coal shows that the release intensity of alkali metals Na* and K* in the peripheral position of the combustion flame is stronger than that in the central position

APPA Increases Lifespan and Stress Resistance via Lipid Metabolism and Insulin/IGF-1 Signal Pathway in <i>Caenorhabditis elegans</i>

Animal studies have proven that 1-acetyl-5-phenyl-1H-pyrrol-3-yl acetate (APPA) is a powerful antioxidant as a novel aldose reductase inhibitor independently synthesized by our laboratory; however, there is no current information on APPA’s anti-aging mechanism. Therefore, this study examined the impact and mechanism of APPA’s anti-aging and anti-oxidation capacity using the Caenorhabditis elegans model. The results demonstrated that APPA increases C. elegans’ longevity without affecting the typical metabolism of Escherichia coli OP50 (OP50). APPA also had a non-toxic effect on C. elegans, increased locomotor ability, decreased the levels of reactive oxygen species, lipofuscin, and fat, and increased anti-stress capacity. QRT-PCR analysis further revealed that APPA upregulated the expression of antioxidant genes, including sod-3, gst-4, and hsp-16.2, and the critical downstream transcription factors, daf-16, skn-1, and hsf-1 of the insulin/insulin-like growth factor (IGF) receptor, daf-2. In addition, fat-6 and nhr-80 were upregulated. However, the APPA’s life-prolonging effects were absent on the daf-2, daf-16, skn-1, and hsf-1 mutants implying that the APPA’s life-prolonging mechanism depends on the insulin/IGF-1 signaling system. The transcriptome sequencing also revealed that the mitochondrial route was also strongly associated with the APPA life extension, consistent with mev-1 and isp-1 mutant life assays. These findings aid in the investigation of APPA’s longevity extension mechanism

Corrosion and degradation mechanisms of high chromia refractory bricks in an entrained-flow gasifier: experimental and numerical analysis

As a crucial component of an opposed multi-burner (OMB) coal-water slurry gasifier, severe degradation of the refractory lining frequently results in costly operation delays. In this work, the morphology and damage evolution of the used high chromia refractory bricks in a gasifier were evaluated by experimental tests and numerical analysis to gain insight into the corrosion and degradation behavior of the refractory lining. The results indicated that the degradation of high chromia refractory bricks were mainly owing to the structural spalling caused by slag corrosion and thermal stress induced by temperature gradient. The stress cracks developed at the corroded interface provided a penetration pathway for slag and served as a sub-surface for further corrosion, resulting in additional corrosion and spalling. Furthermore, the formation of the composite spinel phase with a high thermal expansion coefficient also contributed to significant thermomechanical stress. The degradation behavior of high chromia refractory brick followed the “penetration-dissolution/reaction-spalling” mechanism. Based on experimental and numerical results, a conceptual model was developed to describe the progressive degradation mechanism of refractory, and several possible solutions were also suggested

Preparation of Fe-Doped Carbon Catalyst for Methane Decomposition to Hydrogen

Fe-doped carbon catalysts were prepared from Shenmu sub-bituminous coal with addition of Fe­(NO₃)₃ by KOH activation, and used for catalytic methane decomposition. The effects of Fe amount and carbonization/activation temperature on the structure and catalytic performance of resultant catalysts were investigated. The results showed that ferric nitrate mixed with coal could be directly reduced to Fe metal during the carbonization/activation process without a hydrogen reduction process. Methane conversion over Fe-doped carbon catalysts significantly increases as the amount of added Fe increases. When the amount of Fe added is 30 wt %, the resultant Fe-doped carbon has the highest catalytic activity and methane conversion increases from initial 20% to 58% at the reaction time of 9 h. Low carbonization temperature leads to high initial conversion. The active sites of the Fe-doped carbon catalysts prepared at higher temperature mainly come from metal Fe particles, thus leading to lower initial catalytic activity but better stability

Correlation between Flow Temperature and Average Molar Ionic Potential of Ash during Gasification of Coal and Phosphorus-Rich Biomass

The co-gasification of biomass and coal is helpful for achieving the clean and efficient utilization of phosphorus-rich biomass. A large number of alkali and alkaline earth metals (AAEMs) present in the ash system of coal (or biomass) cause varying degrees of ash, slagging, and corrosion problems in the entrained flow gasifier. Meanwhile, phosphorus is present in the slag in the form of PO43−, which has a strong affinity for AAEMs (especially for Ca2+) to produce minerals dominated by calcium phosphates or alkaline Ca-phosphate, effectively mitigating the aforementioned problems. To investigate the changing behavior of the slag flow temperature (FT) under different CaO/P2O5 ratios, 72 synthetic ashes with varying CaO/P2O5 ratios at different Si/Al contents and compositions were prepared, and their ash fusion temperatures were tested. The effects of different CaO/P2O5 ratios on the FT were analyzed using FactSage thermodynamic simulation. A model for predicting slag FT at different CaO/P2O5 ratios was constructed on the basis of the average molar ionic potential (Ia) method and used to predict data reported from 19 mixed ashes in the literature. The results showed that Ia and FT gradually increased with a decreasing CaO/P2O5 ratio, and the main mineral types shifted from anorthite → mullite → berlinite, which reasonably explained the decrease in ash fusion temperatures in the mixed ash. The established model showed good adaptability to the prediction of 19 actual coal ash FTs in the literature; the deviation of the prediction was in the range of 40 °C. The model proposed between FT and Ia based on the different CaO/P2O5 ratios can be used to predict the low-rank coal and phosphorus-rich biomass and their mixed ashes

Study of synergistic behavior during bituminous coal-cow manure co-gasification: The role of intrinsic AAEM and organic matter

Abstract Co-thermal chemical conversion of coal and biomass is one of the important ways to realize efficient and clean utilization of coal. In this study, a typical Ningdong coal-Yangchangwan bituminous coal and cow manure were used to study the synergistic effect of intrinsic alkali, alkaline earth metals (AAEM) and organic matter on the co-gasification of coal and biomass by thermogravimetry analyzer (TG). The results showed that AAEM had obvious synergistic promotion effect on the gasification of a bituminous coal-cow manure mixture in the isothermal gasification (1000 ℃), whereas the organic matter will show the opposite effect on the process. To further investigate the effect of organic matter on the gasification process, the influence of organic matter on non-isothermal (25-1000 ℃) gasification reaction was investigated with heating rate of 10 ℃ /min, the kinetic parameters of the gasification reaction were obtained by Coats-Redfern method. The increase of biomass mass fraction in the sample facilitates the migration of alkali metals from the material to the solid phase. The possible mechanism of the synergistic effect of intrinsic AAEM/organic matter on the co-gasification process was proposed

In Situ Analysis of Catalytic Effect of Calcium Nitrate on Shenmu Coal Pyrolysis with Pyrolysis Vacuum Ultraviolet Photoionization Mass Spectrometry

To investigate the effect of calcium mineral on the product distribution of low-rank coal pyrolysis, a Chinese subbituminous coal (Shenmu coal), and samples with 5% and 10% added calcium content, were selected to study with a homemade pyrolysis vacuum ultraviolet photoionization mass spectrometry (py-VUV-PIMS) system. In this system, secondary reactions of the pyrolysis products were generally inhibited because of in situ sampling, soft ionization, and high vacuum environment, which allowed direct detection of the initial pyrolytic products. Most evolved compounds during temperature-programmed heating from 30 to 650 °C were ionized by a VUV lamp (10.6 eV). The main products include five categories: alkenes, dienes, aromatics, phenols, and dihydroxy aromatics, which were formed via homolytic scission of weak bonds in side chains and bridges between aromatic nuclei in coal structure. The calcium mineral additives can dramatically affect pyrolytic product distribution, especially oxygen-containing compounds. The main reason is that calcium mineral plays a catalytic role in deoxygenation, which prompted incorporation of oxygen-containing compounds into corresponding aromatics, and resulted in the product of BTX levels increase significantly. The decrease in relative average molecular weight indicated the conversion of heavier components into lighter species, in terms of the observed <i>m</i>/<i>z</i> of the evolved gas components