I am installing a gas dryer, I understand all the requirements, but cannot find anything that addresses this question; my install comes out the back of the dryer and goes vertical about 4 ft, then turns 90 degrees to exit out the wall to the outside. But is there any requirement that states how close that vertical portion can be to the interior wall? That effects how far the dryer juts out into the room. My dryer installation manual specifies how close the dryer cabinet can be to adjacent walls, but not the vent pipe itself.
Given that the dryer vent pipe typically goes through the wall without any special consideration, touching the wall surface should also be fine. Unlike other combustion appliances, the dryer exhaust is diluted with a great deal of additional air. If it's hot enough to scorch your wall, it's hot enough to scorch your clothes.