High expansion (Hi-Ex) foam is recommended to suppress the leakage and diffusion of cryogenic liquid due to its light weight and large volume. However, the disadvantages of low stability and high break rate under environmental conditions are all limited the further application in vapor mitigation and fire extinguishing. So that, this paper focus on the effect and mechanism of nanoparticles in stabilizing Hi-Ex foam. Three kinds of nanoparticles with different concentration were selected to evaluate the effect of foam half-life and the mechanism of particles on improving the foam stability. The results indicated that different particle concentrations can improve the foam stability to a specific extent, and the maximum improving of half-life can increase by 95.4% in the presence of the hydrophilic SiO 2 at .5 wt%. Meanwhile, the hydrophilicity, size, and morphology of the particles have a specific impact on the foam stability. The foam expansion rate first increased and then decreased. From the microscopic point of view, the bubble size gradually increases with time by two processes of ripening and coalescence and satisfied in a logarithmic distribution. While, the liquid film thickness remarkably decreases due to foam drainage without particles and the adsorption and accumulation of nanoparticles on foam lamella can provide a spatial barrier for the film thinning and the inter bubble diffusion. Finally, the microscopic interaction mechanism on improving the foam stability has been further explored and revealed in these two aspects.
Jianlu Zhu,Youmei Peng,Naiya Xie,Zihe Li,Yixiang Zhang,Wuchang Wang,Yuxing Li
In the process of high expansion foam inhibiting liquefied natural gas (LNG) leakage evaporation, LNG and water in foam will generate hydrates in a normal pressure environment. In order to study the absorption effect of hydrate on LNG vapor, a hydrate formation device in an LNG–foam system was designed. The gas content experiment of hydrate was carried out to evaluate the inhibition effect of hydrate absorption on LNG evaporation, which provides a basis for improving the stability time of hydrate and reducing the escape rate of natural gas. Tetrahydrofuran (THF) will aggravate the foam drainage rupture, thereby weakening the stability of the foam. On the basis of adding a hydrate thermodynamic promoter, nanoparticles were added to enhance the stability of foam. The experimental results show that the foam half-life of 1 wt % THF and 0.5 wt % hydrophilic SiO2 nanoparticles is the longest, which is 1.7 times higher than that without additives. The gas absorption of hydrate formed in the compound system accounts for 57.5% of LNG evaporation gas, which is more than 4 times that without additives.
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