Self-Ignition Caused by Solar Radiation

Transportation of goods is carried out by railroad tank cars or by tank trucks or by sea containers. Transport of dangerous goods has to be in agreement with international codes like “UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, 5th rev. ed., United Nations, New York and Geneva 2009”. Unfortunately the international codes do not take into account the influence of solar radiation on the self- ignition of chemical reactive substances during transport and storage. The thermal behavior of the chemical substances is regarded only under the influence of the ambient temperature. Thermal loading by solar radiation is neglected. This is a deficiency in all the codes. This paper will explain the importance of taking solar radiation into account. Solar radiation means that package and substance are exposed to an external diurnal heat flux. Depending on the kinetic properties of the substance sooner or later runaway may occur. That is why the induction period of the material in consideration has to be known. Transportation and storage time is only one part of the induction time. A practical example serves to demonstrate the importance of taking external heat flux into account. The thermal behavior of hard coal dust is investigated packed in paper bags and piled up on a palette. It is demonstrated that the runaway process is influenced by solar radiation. If the boundary conditions imply this external heat flux the hard coal dust suffers from runaway after 14 days. If the boundary conditions are governed by ambient temperature only the external heat flux is missing and no thermal explosion will occur. Transportation and storage time has to be significantly less than the induction period of 14 days. How this can be managed is discussed in the last chapter of this paper.