(41s) Fire and Explosion Hazards Associated with Transfer of Powders into Flammable Solvents

Transfer of powders into flammable solvents is a very common operation frequently applied in different branches of the process industry such as pharmaceutical, paint, adhesive, etc. Typically, additives, pigments, catalysts, or other powders are manually transferred into a vessel already containing a flammable liquid. When the liquid is at a temperature above its atmospheric flash point, a flammable atmosphere could exist at the charging point, if oxygen is not excluded. Many commonly processed powders, when in motion against other surfaces/materials create an electrostatic charge. When the magnitude of the charge is sufficiently high, electrostatic discharges can result. Depending on their nature, electrostatic discharges could ignite flammable vapor atmospheres and/or a hybrid mixture of vapor and powder dust cloud. Hybrid mixtures could be highly explosive with regards to the ease of ignition (ignition sensitivity) and the consequence of the explosion (explosion severity). This paper will consider the following; (1) a case study of deflagration involving a hybrid mixture of flammable solvent and combustible dust; (2) avoidance of the ignition of explosive atmospheres either through inerting or effective ventilation; (3) mitigation of the detrimental effects of an explosion; and (4) discussion of possible ignition sources such as electrostatic discharge from ungrounded equipment, insulating objects, and personnel