They can’t shut down the dang refinery! The lever’s stuck and they’re out of WD-40!
I actually had the least problem with that. It’s entirely plausible that huge machines can’t just turned off in an instant. Even real life nuclear reactors need something like +12 hours even for an emergency shutdown. A city-sized space-refinery probably has so much momentum in it’s spinning parts that it is faster to just shoot that thing.