How to use blowtorch to remove valve assembly?

I've never done this before can someone pls give me some tips or what to look for when I know to stop. I have a Coleman 249 and the valve assembly is needed to be removed, it has a cement looking sealant causing it's removal from the bung to be rather perilous.
I dont want to melt or damage the bung soldering.

 

Would concrete remover work?

 

What is the issue with the valve? Why must it be removed.
Concrete remover will not work.

 

It needs to be removed for cleaning as part of a restoration

 

So it does not really need to be removed. You just want to. Please do not do - If it ain't broke, don't fix it.

What does it help to damage a part when restoring others?
Unless it is absolutely necessary for technical reasons to dismantle the lamp completely, this step can be omitted.

Erik

 

Well yeah I want to badly lol. How do I do it