Most industries that deal in refining or other heat-intensive processes are nearly hard to impossible to pause or stop. My understanding is that glassmaking plants, for instance, will literally solidify if they ever stop operation--making it an extremely rare occurrence. I wouldn't be surprised if aluminum refining is the same way--fighting entropy keeping things hot is a losing battle, so not very dispatchable.
That is true about float glass plants but for a different, very interesting reason.
Float glass plants work by literally floating a thin sheet of molten glass on top of a giant tank of liquid tin. They have a swimming pool of liquid tin, float molten glass on top, and then push it along the tank length wise.
The glass and tin is then gradually cooled until the glass is solidified. It's then cut into pieces, cooled and stacked.
If the thing suddenly stops, or there is a hiccup of some kind, the thermal expansion of the glass, along with its extreme hardness (lack if strength) it will just shatter the whole mile long sheet of glass. My understanding is that it takes the better part of a year to recover from something like this.
In aluminum, its basically electroplating. They basically electroplate the aluminum out of the ore onto the ingots. My understanding is that takes a few weeks to a month to recover from a similar incident.
I confirm that an aluminium refinery is not something you stop lightly. I remember something about taking two weeks to restart? Maybe more. Source, had family working at a large northern plant.
Being able to restart it at all makes it better than a lot of industries. Many of these liquid-metal affairs depend on convection and inertia to keep the metal molten, and if it solidifies inside a pipe—well, then you don't have a pipe anymore; you have a bimetal pole.
Glass melting furnace never stops after it's started. If it cools down it's basically destroyed so yeah, they run uninterrupted for years. Any maintenance or fixes need to account for that.
There are electrically heated glass furnaces. They work by immersing electrodes in the molten glass, which is electrically conductive, if somewhat resistive. I imagine they could use gas for startup though. The use I saw for this was in making fiberglass from recycled glass cullet.
Right. The wall has to continue to be cooled -- if it reaches the temperature of the melt, it's ruined -- so there's always some heat loss. And if the electrolyte freezes you're also in trouble.
