Study On Thermal Runaway Mechanism Of Guanidine Nitrate

Reactive active substance,because its molecule contains the reactive group,so its structures are very unstable.Some thermal runaway accidents were caused by them in industry.According to the literature survey and the statistical analys is of the thermal runaway accidents in the domestic industry from 1984 to 2016,this article chooses guanidine nitrate as the research object.The thermal runaway mechanism of GN was studied from the point of intrinsically safe,using the method of experiment and theory.In the experiment part,the heat flow curve of GN in six heating rate(2,4,6,8,10,and 12?/min)and five kinds of particle size were tested by using Differential Scanning Calorimeter.The weight loss curves of GN decomposition were determined by Thermal Gravimetric Analyzer.Based on the production process of GN,the effects of water,nitric acid,ammonium nitrate and urea on the heat release characteristics of GN were measured.The results show that with the increase of the heating rate,the exothermic peak becomes narrow and moves to the high-temperature region,heat release rate and peak temperature increases.Compared to other experimental conditions,when the heating rate is 6?/min,GN thermal decomposition is more dangerous.According to the calculation based on the method of Kissinger and Ozawa,the activating energy of GN is 121.12kJ/mol and 125.62kJ/mol respectively.With the decrease of the particle size,the GN exothermic peak is narrower and the thermal decomposition efficiency becomes higher.Compared to the other four groups of particle size,when the GN particle size between 161~212?m,GN thermal runaway easier to trigger.TGA experimental results show that the weight loss curve of GN includes four stages.The second stage is the main stage of decomposition,and the maximum value of the weight loss rate is reached at 300?.The water has little effect on the decomposition of GN.Nitric acid can promote the decomposition of GN.Ammonium nitrate can reduce the probability of thermal runaway in GN;both urea and GN are mixed and have an inhibitory effect on each other's thermal stability.In the theoretical part,this paper uses Gaussian 09 software,and the single point energy of the GN molecule was calculated by choosing density functional theory(DFT)with the B3 LYP method in 6-311++G(d)based group as-486.1067 hartree.Then,the heat released and the activation energy of GN was calculated by calculating the vibration frequency of GN molecules,and the bond dissociation of the bonds was sorted and the reaction path was determined.The results show that the heat released of GN is 543.47J/g,which is close to the measured 490J/g.The activation energy of GN is 113.58kJ/mol,which is similar to that obtained under the experimental conditions.The decomposition of the GN molecule first breaks the nitrogen-oxygen single bond,followed by the nitrogen-oxygen double bond.That is the nitric acid part preferentially decomposed to produce water,oxygen and nitrogen oxides.The remaining guanidyl part of the decomposition breaks its carbon and nitrogen single bond,generate ammonia and carbon dioxide.Through the study of GN thermal runaway mechanism,to understand the thermal characteristics of GN,it can provide safety guidance in the process of production,transportation,storage and use.