无机盐类阻化剂和自由基捕获剂对煤自燃的协同抑制作用

Synergistic inhibition effect of inorganic salt inhibitor and free radical scavenger on coal spontaneous combustion

从隔氧降温和终止自由基链式反应角度出发,将无机盐类阻化剂氯化镁和氯化钙与自由基捕获剂N,N-二苄基羟胺(DBHA)和2,6-二叔丁基-4-甲基苯酚(BHT)结合形成一种持续高效抑制煤自燃的复合阻化剂。以易自燃长焰煤为研究对象,采用阻化性能测定实验、活性官能团以及热分析表征实验研究复合阻化剂的阻化性能;以煤自燃过程中CO释放、煤中活性官能团的转化以及煤体质量的变化规律3者之间的关联性为基础,结合氧化反应热动力学特性,探讨复合阻化剂的阻化机理。实验结果表明:复合阻化剂对煤自燃过程起到协同抑制作用,具有物理化学双重阻化效果。与原煤相比,经复合阻化剂处理煤样,CO释放量在128℃时减少88.7%,在初始失重阶段和吸氧增重阶段抑制率均在80%以上,100℃时抑制率达到82.5%。复合阻化剂通过降低煤中羟基、甲基和亚甲基以及含羰基类活性组分的含量发挥阻化作用,其中芳香酮类化合物相对含量下降明显。添加复合阻化剂的煤体氧气吸附过程变短,吸附量减少,并且随着煤自燃进程发展活化能呈现出增加的趋势,特别在吸氧增重阶段活化能增加53.2%。在初始失重阶段,无机盐的保水作用对煤自燃起到物理隔氧和降温作用;在吸氧增重阶段,自由基捕获剂与煤中含氧活性自由基进行共价键重组,从而起到化学阻化效果。DBHA会释放出游离的H+,并提供未共用电子的氮、氧原子,从而形成多个吸收位点,可以同时对氧自由基和碳自由基等进行捕获;BHT与游离的含氧官能团发生反应,生成稳定的化合物,使得酮类、醌类和醛类化合物的生成途径被打断,阻断煤的自由基链式反应,从化学反应途径抑制煤自燃过程。

From the aspects of isolating oxygen,lowering temperature and terminating free radical chain reaction,a compound inhibitor with continuous effective inhibition of coal spontaneous combustion was obtained from the combination of the inorganic salt inhibitors MgCl2 and CaCl2 with the radical scavengers N,N-dibenzylhydroxylamine(DBHA)and Butylated hydroxyl toluene(BHT).With the easy self-igniting long flame coal as the research object,the inhibitory performances of coal samples treated with different inhibitors were studied by using the inhibition performance test,the characterization of reactive functional group and thermal analysis experiments.Based on the correlations among CO emission,evolution of functional groups,and mass change trend during coal spontaneous combustion,the inhibition mechanism of composite inhibitors was discussed combining with the thermodynamic characteristics of oxidation reaction.The experimental results show that the compound inhibitor has a coordinate inhibitory effect during the whole process of coal spontaneous combustion,with physical and chemical double inhibition effect.Compared with the raw coal,the amount of CO released from coal sample treated by the compound inhibitor was reduced by 88.7%at 128℃,and the inhibition rate reached 82.5%at 100℃.The inhibition ratio is higher than 80%during the initial weight loss stage and the oxygen absorption and weight increase stage.The compound inhibitor plays an inhibitory role by reducing the contents of hydroxyl,methyl,methylene groups and active components containing carbonyl groups in the coal,wherein,the relative content of a carbonyl compounds decreased obviously.The coal-oxygen chemisorption time for coal sample with the addition of composite inhibitor becomes short accompanied by the least adsorption quantity,and the weight gain rate decreased by 0.29%.The activation energy is increased with the development of coal spontaneous com-bustion,especially for the oxygen absorption and weight gain stages,with the activation energy increased by 53.2%.In the initial weight loss stage,the compound inhibitor exhibits physical inhibiting effects by the water retention due to inorganic salt.In weight gain stage,the compound inhibitor exhibits chemical inhibiting effects through the recombination of covalent bonds between free radical scavenger and the oxygen-containing active free radicals in the coal.DBHA releases free H+and provides N and O atoms that do not share electrons.N,N-dibenzylhydroxylamine(DBHA)molecular structure contains multiple absorption sites,which can simulta-neously capture multiple free radicals in coal.Butylated hydroxyl toluene(BHT)reacts with free oxygen-containing functional groups to form stable compounds.Meanwhile,the formation paths for ketones and aldehydes are interrupted.Therefore,the compound inhibitor can control the process of coal spontaneous coal combustion via a chemical reaction pathway.