过硫酸铵胶囊破胶剂的自加速分解温度和自反应过程研究

Study on the self-accelerating decomposition temperature and self-reaction process of encapsulated ammonium persulfate gel breaker

为评价过硫酸铵胶囊破胶剂在运输中的自反应危险性,按照联合国《关于危险货物运输的建议书——试验与标准手册》中的H 2方法,采用绝热杜瓦量热仪对过硫酸铵胶囊破胶剂进行绝热储存试验,并计算了该物质在3种典型包装下的自加速分解温度。结果表明,分解反应分为2步,其活化能接近,这2步反应实质上是同一反应,即最初反应进行到一定阶段后由于接触面上的反应物消耗和产物积累而停止,而温度升高又引起包覆的聚合物软化,增大了反应物接触面和产物的扩散速度,从而使反应重新开始。研究表明,该物质的包装件不应划入联合国规定的4.1项危险品中的自反应性物质。

The present paper is aimed to introduce our study results on the self-accelerating decomposition temperature and self-reaction process of encapsulated ammonium persulfate gel breaker. As is known, since the hazardous self-reactive explosion of encapsulated ammonium persulfate gel breaker in the process of transportation has often aroused great concern in industrial and transportation practice, the study on how to solve the problem has become a hot topic in recent years. Thus, in this paper, we have first of all introduced and analyzed a few methods for the decomposition temperature （SADT） testing. Next, we have introduced the UN H.2 method in UN ＂Recommendation on transport of dangerous goods-manual of test and criteria＂, which has often been chosen to test the encapsulated ammonium persulfate gel breaker＇s SADT. In proceeding with our study, we have prepared an instrument calibration test by sodium chloride. In addition, we have also worked out the heat loss rate curve of the Dewar container and the heating curve of the gel breaker through examination. By using the heat loss curve per unit mass of three UN packagings for solid stated in the manual of the gel breaker＇ s SADT treating, it is possible to work out the temperatures of the gel breaker＇ s SADT in three packagings-1G （50 L）, 4G （50 L） and 1G （110 L）, which are 90 ℃ , 90 ℃ , and 85 ℃ respectively. The above resuits show that the gel breaker in the all three packages should not be classified as self-reactive substances by UN RTDG-model regulations. Furthermore, there were two kinds of reactions with onset temperatures of about 40 ℃ and 80 ℃ in the decomposition process. The activating energies can also be worked out after the simplified kinetic data treatment, and the final results of the two reactions are very close, which shows the two reactions are essentially the same. Therefore, if the first decomposition reaction ends up due to consumption of the reactants and accumulation of products on the contact surface, it will restart at a higher temperature, since high temperature would soften capsulate polymers, enlarge the contact surface of the reactants again, and speed the diffusion of the products.