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

The effects of two free-floating plants (Eichhornia crassipes and Pistia stratiotes) on the burrow morphology and water quality characteristics of pond loach (Misgurnus anguillicaudatus) habitat

Loach exhibit conspicuous drilling behaviors in the mud of shallow waters, yet their burrow morphology and the factors affecting this behavior have received little attention. We characterized the burrow morphology and water quality of the pond loach Misgurnus anguillicaudatus in three scenarios: in tanks without plants, tanks with the free-floating plant water hyacinth Eichhornia crassipes, and tanks with water lettuce Pistia stratiotes. Water hyacinth effectively removed water TN, COD, NO3-N and NH4-N, and water lettuce removed water TP and NH4-N. Water hyacinth and water lettuce markedly reduced water turbidity and DO, increased TOC and EC. Water hyacinth purified water more effectively than water lettuce, providing a suitable habitat for loach feeding, living and burrowing. The burrow structures were V-shaped, Y-shaped, inverted L-shaped, or complicated dendritic networks composed of multiple V shapes. The hyacinth treatment was characterized by the greatest burrow volume, length, depth, and structural complexity, but the opening size was reduced by dense root mat coverage. Burrows in the water lettuce treatment were characterized by intermediate volume, length, branches and sinuosity, but they had the largest opening and pit size. The control treatment had a flat bottom with the smallest, shortest burrows. This study indicates that free-floating plants improve habitat suitability and change burrow morphology and may be used to improve loach breeding methods