[Robert A Cook PE]

I tend to agree with you. I’m glad no one was killed.

[mozarky2]

First, a pulverizer mill “puffed” (I’ve never understood why an explosion of such magnitude is called a puff). The resulting pressure fed to the igniters blows out the ignition, then after a few seconds, KABOOM! The fact that the explosion was heard first, then the black smoke, leaves little doubt in my mind.