all fuel chimney section for heat riser?

Would a 36" section of 6" all fuel chimney work for a heat riser in a 6" system?. Would this be durable enough?  just asking,someone gave offered it to me...Larry

I believe you're referring to double wall metal insulated / Class-A chimney sections. Those will not hold up very long as a heat riser.

Probably the easiest heat riser to make yourself is one stacked up with IFB (insulated fire brick) on edge, for a 2.5" riser wall thickness. Some folks stick the IFB together with clay slip. Mine has the IFB mortared in place, mortar made of a 1:1 mix of fire-clay and sand.

If you can't locate a source of insulating firebrick (they are an expensive specialty item), common "split" firebrick laid up on edge so the wall is 1 1/4" thick and wrapped with rockwool insulation makes a good riser.