Effect of Electrostatic Charging of Dry Combustible Particulates on Fires and Explosions

Solids Processing of dry particulates of various forms and shapes within unit operations ranging from milling to mixing, crystallization to drying involving storage, handling and conveying results in the generation of electrostatic charging. This accumulation of charges on the particulates is due to frictional effects of discrete particles and is normally referred to as tribo-charging. The degree to which particles may be charged is a function of the resistivity of particles; higher the resistivity is longer the duration of charge retention with slower dissipation. If such a particulate product is handled, it is critical to understand the static charging effects in a unit operation since the ignition hazard posed by the charge accumulation and retention is associated with the possibility that some portion of this energy will be released rapidly by an electrostatic spark which may be energetic enough to ignite a suspension of dust cloud that might be present. The incident's investigation involving static charging is always a challenge to conclude since tracing back to ignition sources is very complex. Hence, preventing such an incident is crucial. This paper presents a fundamental approach of understanding various types of charge generation in a given unit operation and solutions to mitigate them with some practical case studies.