Why is the tank getting hotter? Unless there is a chemical reaction going on in the tank this should not be happening. I suspect someone made a massive error of what they put into the tank.
The chemical must be polymerizing, which can give off a lot of heat. Search "polymerization inhibitor" to learn more.
100% !! There is a reaction going on that shouldn't be happening. They didn't have enough inhibitor in the tank. They apparently can't get MORE into the tank. There are multiple mal-functions going on here.
Other sources say the flash point of the chemical is about 32*F.