微米/纳米PMMA粉尘爆炸抑制过程中压力特性与热化学动力学的相关性

Correlation between pressure characteristics and thermochemical kinetics during suppression of micro/nano PMMA dust explosion

为了揭示微米/纳米PMMA (polymethyl methacrylate)粉尘爆炸的抑制机理,利用同步热分析仪和20 L爆炸试验装置,对微米/纳米PMMA粉尘在抑爆粉剂NaHCO3干预下的热解动力学特性和爆炸特性展开了实验研究,分析了惰化爆炸混合体系的爆炸压力特性参数与热化学动力学参数的相关性,并探讨了基于热化学动力学的粉尘爆炸抑制机理。结果表明:NaHCO3通过物理化学协同抑制作用影响了微米/纳米PMMA粉尘的热解及氧化进程,提高了爆炸混合体系的活化能,减弱了爆炸强度;且抑爆剂粒度越小、添加比例越大,爆炸混合体系的表观活化能越大;与最大爆炸压力相比较,最大爆炸压力上升速率对爆炸体系活化能的敏感度较高,而纳米PMMA粉尘对爆炸混合体系活化能的敏感度大于微米PMMA粉尘,抑爆效果也更显著。

To reveal the explosion suppression mechanism of micron/nano polymethyl methacrylate(PMMA)dusts,the synchronous thermal analyzer and the 20-L explosion test device were used to test the pyrolysis oxidation characteristics and the explosion overpressure evolution characteristics of micro/nano PMMA dust under the intervention of NaHCO3.Coats-Redfern method was used to calculate the kinetic parameters for the rapid pyrolysis of 30μm and 100 nm PMMA and micro/nano mixtures,and the correlation between pressure characteristics and thermochemical kinetics during suppression of micro/nano PMMA dust explosion was analyzed,and then the suppression mechanism of dust explosion based on thermochemical kinetics was discussed by establishing the physical model of suppression mechanism of NaHCO3 on micro/nano PMMA dust explosions.The results show that the pyrolysis oxidation processes of 30μm and 100 nm PMMA dusts are suppressed by NaHCO3,and the apparent activation energy and pre-exponential factor are increased.The maximum explosion pressure and the maximum explosion pressure rise rate of both micro-and nano-PMMA dusts are decreased obviously.In the pyrolysis stage of the mixture system,the suppression effect of NaHCO3 is mainly dominated by physical suppression,including the cooling effect of both pyrolysis reaction and products as well as the dilution effect on the concentration of combustible reactant.In the oxidation stage of the mixture system,the suppression effect of NaHCO3 is mainly dominated by chemical suppression.The free radicals are absorbed by the active groups NaOH,forming the Na↔NaOH suppression cycle.And for explosion suppressant,the smaller the particle size and the larger the adding mass ratio,the greater the apparent activation energy E of explosion mixture system,and the more significant the suppression effect.It is worth noting that compared with the maximum explosion pressure,the sensitivity of explosion pressure rise rate to the E increment of explosion mixture system is great,and nano-PMMA dust is more sensitive to the E increment of explosion mixture system than micro-PMMA dust,and the corresponding suppression effect of NaHCO3 on nano-PMMA dust is more significant.