Jinrui Guo,Yaozong Duan,Fashe Li,Huicong Zhang,Fangguan Tan,Xinhua Qian,Hua Wang
In this study, the emission characteristics and formation mechanisms of aldehydes from biodiesel combustion, both before and after oxidation, are comprehensively investigated through Bunsen burner experiments coupled with Chemkin and Gaussian software simulations. The results reveal that the aldehyde concentration initially decreases, then increases, and eventually decreases again as the oxidation time of the original biodiesel increases. During the first 0–6 h of biodiesel oxidation, its overall saturation increases, while the aldehyde generation potential decreases. After 8 h, oxidation products with low bond dissociation energy (BDE) and multiple double bonds readily dissociate into aldehyde intermediates, such as CH 3 O, CH 2 CHO, and C 4 H 6 . This causes an increase in the concentrations of formaldehyde and acetaldehyde by 120.2 % and 188.3 %, respectively. Between 10 and 12 h, the oxidation products undergo transformation, significantly reducing aldehyde emissions. As the overall carbon chain length of biodiesel shortens, combustion accelerates, and the aldehyde peaks rise more rapidly, appearing earlier. The lowest BDE values, both before and after biodiesel oxidation, are concentrated near the ester group and C=C bond. The oxidation product methyl alpha-eleostearate exhibits the lowest BDE of 315.67 kJ/mol. The formation of oxidation products of biodiesel like methyl alpha-eleostearate leads to incomplete combustion, with aldehyde emissions increasing by 9.5–183.2 %. This is due to the electron-withdrawing, electronegative, and resonance effects of the double bonds, which lower the energy required for H-abstraction and β-decomposition reactions during aldehyde formation.
A modified structured dry water (SCDW) was prepared by introducing sodium alginate (SA) and calcium L-lactate (CL) into conventional dry water (DW) to mitigate the risks associated with methane–air explosions. The preparation parameters were optimized, yielding uniformly distributed and structurally stable particles. The results demonstrate that SCDW exhibits superior mechanical stability and water retention compared to DW. Pipeline explosion experiments evaluated the suppression performance of six sodium- and potassium-modified SCDWs. At spraying concentrations of 25–100 g/m 3 , all modified SCDWs significantly reduced the maximum explosion pressure and flame propagation distance, outperforming DW. Specifically, 5 wt% KCl-SCDW at 100 g/m 3 reduced the maximum explosion pressure and flame propagation distance by 38.75 % and 24.10 %, respectively, compared to DW. When the spraying concentration exceeded 200 g/m 3 , both parameters stabilized. A quantitative analysis of five explosion-related parameters confirmed that salt-modified SCDWs provided superior suppression performance compared to DW, with potassium-modified SCDWs exhibiting stronger effects than sodium-modified ones, and KCl-SCDW demonstrating the best suppression performance. HSC and Chemkin simulations revealed that SCDW exerts both physical and chemical suppression effects. Physically, DW particles suppress combustion through evaporative cooling, oxygen dilution, energy absorption from particle collisions, and thermal radiation blocking. Chemically, gaseous active species capture and consume H and OH free radicals, interrupting chain reactions through catalytic cycles and generating stable compounds, thereby reducing the maximum explosion pressure and flame propagation speed. Modified SCDWs offer an environmentally friendly, stable, and efficient approach to methane-air explosion suppression.
危险品化学品经营许可证（带存储）