A first step towards a standardized iron fuel: Safety characteristics of several pure iron powders

• Four reduced iron powders were analyzed on their safety characteristics. • Three different reduction methods were used. • A general estimation for safety characteristics for iron powders is presented. While the use of iron powder as a dense energy carrier has clear advantages over other carriers such as hydrogen and ammonia in terms of health and safety, risks may still emerge from the powder if accidentally dispersed in air during handling, transport and storage. Since the safety characteristics of dusts are affected by, among others, its particle size distribution, chemical properties and moisture content, it is hard to implement safety measures and select the most promising reduction method without a prior explosion testing. Various production and reduction methods are currently being investigated, each producing a morphologically different type of powder. In one of the key databases on safety characteristics of dusts from the Federation of the Statutory Accident lnsurance of Germany, the maximum explosion pressure ranges from non-explosible (=0) to 5.1 bar and the deflagration index goes up to 111 bar*m /s. In this work the safety characteristics of four different iron dusts, produced via three different reduction methods, are investigated using a 20-Liter sphere according to ISO/IEC 80079–20-2:2016–12 (explosibility). Three of the dusts were found to be explosible and were further tested according to EN 14034–1 (maximum explosion pressure) and EN 14034–2 (maximum rate of pressure rise). Though they were found explosible they were all categorized in dust class St1 as mildly explosible. The morphology of the powder was analyzed before the explosion tests using scanning electron microscopy and X-ray diffraction. The particle size distribution was also determined. Since the chemical properties and the moisture content are known, the findings may be applicable to implementation at larger scale without prior testing of every powder.