He was very, very demanding and his class was very hard, our median scores were around 20-30% lower than in any other class, but in the end, I can def. say that after two years studying with that dude, it was my strongest subject, I could literally spit pages of text about anything in his exams in the end.
It was very hard, but it was very worth it and very fun to actually understand whats going on inside large chemical reactors.
Ofc, there are some teachers/professors that are making things too hard with no purpose (like robot-reading walls of text in a super speed mode and then demanding you to remember them on exam word by word), but some of them just have high standards and its a good thing