How to hang a dryer vent in a basement ceiling?
You can use metal pipe hanging tape to hold it up. It comes in a roll and has several holes in it which you would use to attach it to your framing with nails or screws. Simply cut it to length with a pair of aviation snips, and nail or screw it up.

Once thing you want to be careful of is not to put it on too tight and crush the vent line.