Massive Pipes

Next to our work car park they are constructing what I think is going to be an incinerator.  Every day for the past month or so, we have enjoyed (!) the constant deep thud-thud-thud of the pile drivers, which has sounded like some hideous Orc factory thing from Lord of the Rings.  Today there arrived some massive pipes, about 3 metres diameter, and ten or so metres long.  I'm not sure what they are for - maybe it will become clear in due course.