Ignition And Explosion Characteristics And Microcosmic Characterization Of Coloured Corn Starch Dust

Dust explosion accidents in the process of industrial production have caused a great threat to the life and health of personnel and property safety,and seriously restricted the industrial development of the society.The explosion characteristics and variation of coloured corn starch dust were studied by 20 L sphere explosion test units.The characteristics of the oxidation process and the formation laws of gas products of coloured corn starch dust were studied by thermogravimetry–differential scanning calorimetry–fourier transform infrared spectroscopy（TG–DSC–FTIR）.The explosion characteristic parameters under eight different dust concentrations and four ignition delay time conditions were measured.The explosion pressure curves of coloured corn starch dust under two conditions of maximum explosion pressure dust concentration and optimal ignition delay time were drawn.Seven characteristic temperatures in the oxidation process were selected,and the oxidation process was divided into four main stages.The exothermic property of each oxidation stage was analyzed.The activation energy and pre-exponential factor in the four stages were calculated by using three iso-conversion rate methods of Straink,Flynn-Wall-Ozawa（FWO）and Kissinger.The functional groups of coloured corn starch dust were analyzed by in-situ FTIR spectroscopy.The volatile products were detected by TG–DSC–FTIR.The three-dimensional infrared spectra of the oxidation process were drawn,and the index gases（CH₄,H₂O,CO,CO₂）in the oxidation process and their variation laws were obtained.Based on the characteristics of oxidation stage and gas products of coloured corn starch dust,the micro mechanism of oxidation process was revealed from the molecular point of view.The results indicates that the characteristic temperature increased with the increase of heating rate,and the oxidation reaction of colored corn starch dust was easy to occur at a lower heating rate.The coloured corn starch dust showed endothermic trend in the dehydration stage and transition stage,and released heat in the rapid oxidation stage and char combustion stage.The whole oxidation process was exothermic reaction.The value of pre-exponential factor was positively correlated with activation energy,and the reaction in the whole oxidation process,which was surface controlled reaction,had dynamic compensation effect.The functional groups of coloured corn starch dust were O–H,C=O,C–H,C–OH and C–C=O.The volatile products included H₂O,CO₂,CH₄,CO,CH₂O,and CH₃OH.The concentration of CH₄ and H₂O reached the maximum value of the whole reaction process at 350–400 ^oC（rapid oxidation stage）,while the concentration of CO and CO₂reached the maximum value in the range of 450–550 ^oC（char combustion stage）.The content of CO₂ was the the largest.The essence of oxidation reaction of colour ed corn starch dust was the process of internal depolymerization and dehydration of starch molecules after water evaporation to form six kinds of macromolecular gases.The variation law of index gas with temperature in the oxidation process provides a theoretical basis for monitoring the combustion and explosion disaster of coloured corn starch dust in industrial production process,and the results of the research are of reference significance for the prevention and control of the ignition and explosion accident of coloured corn starch dust.