Inhibiting effects of carbonised and oxidised powders treated with ionic liquids on spontaneous combustion

Abstract

The waste of the coal-based activated carbon (CBAC) production process, carbonised powder (CP) and oxidised powder (OP), easily store heat, trigger spontaneous combustion under hot storage conditions, and exhibit strong pyrophoricity. CP and OP pose a serious threat to local environments and inhabitants’ health. In this work, the spontaneous combustion of waste materials generated during the preparation of activated carbon in the coal chemical industry was studied, which has been less studied by previous researchers, and the spontaneous combustion was prevented and controlled by ionic liquid (ILs), a new type of environmentally friendly inhibitor. The influence of ILs containing [BMIM]+ ([BMIM][BF4], [BMIM][NO3], and [BMIM][I]) on the spontaneous combustion of CP and OP was studied and quantitatively analysed. The different samples’ mass loss at different stages was analysed using thermogravimetry at three heating rates (5.0, 10.0, and 15.0 °C/min). A temperature-programmed experiment was used to test the inhibiting effect in treated samples. The results indicated that ILs had varying inhibiting effects on the pyrophoricity of samples. The ILs [BMIM][BF4] [BMIM][NO3] [BMIM][I] had, in descending order of percent inhibition, an inhibitory effect on OP; the order for CP inhibition was as follows: [BMIM][NO3]> [BMIM][BF4]> [BMIM][I]. After IL treatment, the maximum, minimum, and average apparent activation energy all increased to varying degrees. At 30–180 °C, the average percent of inhibition of [BMIM][BF4]–Y (OP treated with [BMIM][BF4]) and [BMIM][NO3]–T (CP treated with [BMIM][NO3]) was 20.21% and 7.32%, respectively, and the maximum inhibition percent was 38.53% and 16.13%, respectively.