Analysis Of Thermodynamics Characteristics And Evaluation Of Spontaneous Combustion Tendency Of Corrosion Products In Oil Tanks

The corrosion products in oil tanks are taken as the research object,and the non-isothermal experiments are carried out at the heating rates of 5 K/min,10 K/min and 20 K/min.Based on the experimental data,oxidized decomposition characteristics of corrosion products are analyzed,the thermokinetics of corrosion products is studied by using the model-based method and model-free method,and the spontaneous combustion tendency is comprehensively evaluated by relevant indexes with physical connotation.It provides theoretical basis for the prevention of spontaneous combustion of corrosion products and important basis for the prevention of tank explosion accidents from the aspects of thermodynamic characteristics and evaluation of spontaneous combustion tendency.The results are as follows:(1)The oxidized decomposition characteristics of different samples are different,but also have similar characteristics.The oxidation reaction starts from about 380 K,and the weight of samples decreases.There are two oxidized decomposition stages for corrosion products from the inner wall of oil tanks,and three oxidized decomposition stages for corrosion product from the bottom of the oil tank.(2)The apparent activation energy at the conversion of 0.05-0.95 was calculated by three model-free methods at the interval of 0.5.The results show that the apparent activation energy changes irregularly with the increase of conversion.Ozawa method is suitable for solving the apparent activation energy of corrosion products.The average apparent activation energies of the five samples were 136.23 k J / mol,83.01 k J / mol,59.79 k J / mol,108.25 k J / mol and 196.32 k J / mol,respectively.(3)Based on 21 kinds of solid decomposition mechanism,the mechanism function of oxidation decomposition was analyzed by model method and Málek method.The single mechanism is not enough to describe the decomposition process of corrosion products,so the multi-step decomposition model should be applied.(4)Based on TOPSIS theory,the tendency of spontaneous combustion of corrosion products on the inner wall of gasoline tank is lower than that of the same batch of diesel tank.The spontaneous combustion tendency of corrosion products on the inner wall of diesel tank is weaker than that on the bottom of tank.The higher the heating rate is,the higher the tendency of spontaneous combustion is,and the greater the risk of spontaneous combustion is.(5)When the apparent activation energy is not considered as the evaluation index of spontaneous combustion tendency,the comprehensive evaluation result is consistent with that of the apparent activation energy.The heating rate has a certain influence on the evaluation of spontaneous combustion tendency,so it is more reasonable to use the average value of each index under different heating rate to evaluate the spontaneous combustion tendency.