Notice how the steam from the power plant hits a certain level, then veers off horizontally. The billows rising from the refinery are doing something totally different, and reaching higher in this instance. It reminds me of a late night photo I got of the refinery and power plant from Highway 1804 north of Bismarck. The steam from the refinery was forming a horizontal line straight south, and the power plant’s steam was heading straight north. I’ll have to look that one up later.
This is a result of the steam hitting a layer of air with a different temperature (and, I presume, a resulting change in pressure). Yes, I did take some astronomy and meteorology in college, but I’m sorry to say I don’t remember many specifics. It makes for a neat photograph, though.