# Preparation of CO2-Adsorbing Fire-Extinguishing Gel and Study on Inhibition of Coal Spontaneous Combustion

## TL;DR

A new fire-extinguishing gel was developed that can adsorb CO2 and inhibit coal spontaneous combustion, offering a low-carbon solution for mine fire prevention.

## Contribution

A composite gel with CO2 adsorption and flame-retardant properties was developed for mine fire prevention.

## Key findings

- The optimal gel formulation is 14% PVA, 7% PEI, and 5.5% PAC.
- The gel reduces CO release by 25.97% and increases activation energy by 14.96%.
- The gel maintains over 76% CO2 adsorption efficiency after five cycles.

## Abstract

Spontaneous coal combustion accounts for more than 90% of mine fires, and at the same time, the ‘dual carbon’ strategy requires fire prevention and extinguishing materials to have both low-carbon and environmentally friendly functions. To meet on-site application needs, a composite gel with fast injection, flame retardant, and CO2 adsorption functions was developed. PVA-PEI-PAC materials were selected as the gel raw materials, and an orthogonal test with three factors and three levels was used to optimize the gelation time parameters to identify the optimal formulation. The microstructure of the gel, CO2 adsorption performance, as well as its inhibition rate of CO, a marker gas of coal spontaneous combustion, and its effect on activation energy were systematically characterized through SEM, isothermal/temperature-programmed/cyclic adsorption experiments, and temperature-programmed gas chromatography. The results show that the optimal gel formulation is 14% PVA, 7% PEI, and 5.5% PAC. The gel microstructure is continuous, dense, and rich in pores, with a CO2 adsorption capacity at 30 °C and atmospheric pressure of 0.86 cm3/g, maintaining over 76% efficiency after five cycles. Compared with raw coal, a 10% gel addition reduces CO release at 170 °C by 25.97%, and the temperature-programmed experiment shows an average CO inhibition rate of 25% throughout, with apparent activation energy increased by 14.96%. The gel prepared exhibited controllable gelation time, can deeply encapsulate coal, and can efficiently adsorb CO2, significantly raising the coal–oxygen reaction energy barrier, providing an integrated technical solution for mine fire prevention and extinguishing with both safety and carbon reduction functions.