Much of my family are in chemical engineering, petroleum engineering, and similar engineering fields, and from what I can tell just about the opposite is true. The companies would much rather hire someone back out of retirement as a consultant at 3x their previous salary, than train up someone younger. They'll hire someone younger, but seemingly as a last resort. This seems most true in a few specific fields (e.g. metallurgy specialists), but also true for more common things like process engineers.