A Novel Highly Stable Biomass Gel Foam Based on Double Cross-Linked Structure for Inhibiting Coal Spontaneous Combustion

Abstract

To enhance the stability of biomass gel foam used for inhibiting coal spontaneous combustion (CSC), a novel highly stable biomass gel foam (SA-Ca2+@TA-GF) based on a double cross-linked structure was prepared by introducing tannic acid (TA) into a gel form (sodium alginate/calcium L-lactate/composite foaming agent). FT-IR confirmed the formation of the double cross-linked structure. The effects of TA concentration on the performance of SA-Ca2+@TA-GF were analyzed, considering gelation time, half-life, film microstructure, and strength. With the addition of 1.6 wt% TA, SA-Ca2+@TA-GF forms a dense foam structure with a gelation time of 10 min. The half-life of the gel foam improves from 0.4 to 30 days and the strength increases by 72.9% compared to that of foam without TA. The inhibition experiments show that SA-Ca2+@TA-GF can asphyxiate coal, thus effectively inhibiting coal oxidation. Additionally, it can increase the temperature of coal at the rapid oxidation stage by 60 °C, and the CO inhibition rate is up to 79.6% at 200 °C. The fire-fighting experiment shows that SA-Ca2+@TA-GF can effectively cool coal and quickly extinguish fires. This study provides a simple method to prepare highly stable biomass gel foams, which is useful for improving the efficiency of gel foams in inhibiting CSC.

Research Progress of Gel Foam Extinguishing Agent in Coal Mines

“…In addition, the accelerated oxidation temperature of coal was delayed from 120 • C to 160 • C, and the CO inhibition rate was 60.5% at 200 • C. On this basis, tannic acid was introduced into this gel foam system to form a double cross-linked structure to enhance the stability of this gel foam. The double cross-linked structure mainly consists of the formation of metal ion coordination bonds between the carboxylate of the sodium alginate and Ca 2+ and the formation of hydrogen bonds between the carboxyl group of sodium alginate and the phenolic hydroxyl group of tannic acid (Figure 8b) [75]. Then, nano-hydroxyapatite (HAP) was introduced into the above gel foam.…”

“…The antioxidant materials in the gel foam could inhibit the spontaneous combustion of coal by preventing the chain reaction of some free radicals in the coal. Han et al [75] proposed a new gel foam and its mechanism in Figure 11. As shown in Figure 11, the coal-oxygen complex reaction is a chain reaction in a continuous cycle.…”

An overview of edible foams in food and modern cuisine: Destabilization and stabilization mechanisms and applications

“…Non‐amphiphilic polysaccharides dispersed in the aqueous phase inhibit the movement and aggregation of dispersed bubbles through gel or thickening mechanism even at low concentrations (Eghbaljoo et al., 2022; Nejatdarabi et al., 2022). Polysaccharides, such as xanthan gum (Sheng et al., 2023), sodium alginate (Han et al., 2022), guar gum (Fan et al., 2023), and cellulose (Weinberger et al., 2009), are often used as gelators to improve the texture and stability of foams. These polysaccharides form a viscoelastic liquid film and a tangled network structure in foam to prevent liquid film drainage, bubble coalescence, and coarsening.…”