The morning of 22 November 2017 was fairly cloudy but the sun caught SY.1225 returning from Sankuang light engine after delivering empties to the loading point there.
Locos don't have to work hard to produce a good exhaust when the temperature is way below zero. Unfortunately sights like this are rarely seen at Wujiu. It's one of those systems where chimney first workings are all downhill and getting a good pile of clag from the chimney is a real challenge.