Can I run a natural gas dryer from a portable propane tank?
If your dryer is set up for natural gas, then it isn't going to run on propane - you'll need to install a propane conversion kit.  Most manufacturers sell these for specific models, and I'm sure there are some generic after-market kits out there too. These generally aren't that difficult to install - you'll basically be changing the limit in the pressure regulator and the size of the orifice to the burner.