Journal
FUEL
Volume 297, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.fuel.2021.120768
Keywords
Coal; pontaneous combustion; LDHs; Intumescent flame-retardant; Composite inhibitor; Char layer
Categories
Funding
- National Key R&D Program of China [2018YFC0807900]
- National Natural Science Foundation of China [51674038, 51874193]
- Shandong Province Natural Science Foundation [ZR2018JL019, ZR2017PEE024]
- Qingchuang Science and Technology Program of Shandong Province University [2019KJG008]
- Shandong Province Science and Technology Development Plan [2017GSF220003]
- Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents [2017RCJJ010, 2017RCJJ037]
- Shandong Province First Class Subject Funding Project [01AQ05202]
- SDUST Research Fund [2018TDJH102]
- Taishan Scholar Talent Team Support Plan for Advantaged & Unique Discipline Areas
- CCTEG Science and Technology Innovation Fund [20182MS016]
- Key Program of the National Natural Science Foundation of China [51934004]
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This paper proposes an intumescent flame-retardant for preventing spontaneous combustion of coal, showing good inhibitory effects throughout the oxidation and decomposition stages. The flame-retardant reduces the surface temperature of coal and enhances its stability through various mechanisms at different temperature levels. The presence of the flame-retardant significantly reduces CO release, increases the temperature with the maximum weight loss rate, and decreases heat release during combustion, ultimately leading to the formation of a porous char layer that inhibits further combustion.
The present paper proposes an intumescent flame-retardant, which is suitable for the entire process of spontaneous combustion of coal. Scanning electron microscopy (SEM), simultaneous thermal analysis, in situ FTIR, and temperature programmed experiment were adopted to analyze its inhibiting effect and mechanism. The results indicate that the flame-retardant can play good inhibitory effects during all stages of coal oxidation and decomposition. In the low-temperature stage of 30-120 degrees C, the flame-retardant carries a lot of water and the surface temperature of coal is reduced since the evaporation of water removes heat. Meanwhile, the hydroxyl groups in the flame-retardant can connect with the -COO- groups on the surface of coal through hydrogen bonds, and enhance the stability of coal. With the temperature increase, some interlamellar water molecules in Mg-AlCO3 layered double hydroxides (LDHs) are removed, which reduces the surface temperature of coal. When the temperature is higher than 170. C, the IFR/LDH undergoes alcholysis and expands, releasing a large amount of non-flammable gas to dilute the oxygen around coal. When the temperature reaches 300 degrees C, the expanded foam layer is carbonized and forms a porous char layer, thereby inhibiting the combustion. The CO release of coal sample with flame retardant reduces significantly. The temperature with the maximum weight loss rate increases by 50-70 degrees C, while the heat release reduces by 11.1-24.2%. After calcination at 500 degrees C for 30 min, the carbon residue is more than 1.6 times that of the untreated coal sample.
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