We really don’t want to claim that gas is the wrong energy in principal or that oil is the only way to produce process heat. But there is a third, in a way, unbeatable solution: gas + oil.
Gas + oil is working! You can convert the steam generator in a way that it will burn both. Not at the same time, of course.
Dual solution means double advantage.
Notice: Gas is a grid-bounded energy. More than a third of Germanys’ natural gas is imported from Russia. Through pipelines adjustable by various states. And if just one state adjusts its valve the whole route will be dead. R-I-S-K !