Moderating electrostatic ignition of organic/mineral animal feed mixtures

Abstract

Mixing inert materials with combustible powders can mitigate electrostatic ignition risks and prevent dust explosions. In the agri-food sector, adding mineral powders to complex organic blends (premixes) is of interest for both nutritional quality and process safety. This research investigates the influence of the minerals' chemical nature and Particle Size Distribution (PSD) on the Minimum Ignition Energy (MIE) of binary mixtures to better understand the inerting effects in premixes. DL-Methionine was mixed with CaCO₃, NaCl, and NaHCO₃, each featuring distinct PSDs and inerting mechanisms. Ignition tests were performed using the MIKE3 apparatus following ISO/IEC 80079-20-2 standards, complemented by Differential Scanning Calorimetry, dust cloud pyrolysis tests in a modified Godbert-Greenwald oven, and gas analysis by micro gas chromatography. The mineral's PSD exhibited the most significant effect on MIE moderation, although its efficacy depended on its chemical nature. For CaCO₃ and NaCl, finer PSDs (median particle diameters of 52 and 35 μm, respectively) effectively inhibited methionine ignition due to their high thermal stability (T_decomp > 900K). NaHCO₃ was the most effective inerting agent, increasing the mixture's decomposition enthalpy by 80% and releasing 30% more CO₂ into the flame zone. These findings support the implementation of inherently safer measures in premix manufacturing.