Plumbing adapter for beer keg

I was given a stainless steel keg.
I want to convert it into a self dousing tlud for making biochar.
To that end, it should have drain in the bottom.
I was able to remove the spear so now I have a hole where the tap would normally go.
I've begune searching for adaptors thar will go from a Standard keg connection to the NPT standard that we use in the US, but the results are confusing and or expensive.
I might resort to a bunch of silicon caulk,but I thought I would ask here first.

Does anyone have experience connecting the bung hole on a stainless steel keg to standard  NPT threads?

I went down a rabbit hole looking for a solution, before realizing that I could cut the protrusion flush and then use a bulkhead coupling.
So, after a long search for my eye protection, I did just that,plus I cut an 11" dia hole at the other end.
I really should be trying out the self dousing design with tin cans before I try it with stainless steel, but this is what motivated me, so this is what is happening!

Sometimes the low-tech way is the best way. Please share results, observations, and pictures when you give this a test run!

I would guess "quench water" is pretty nutrient-infused from bits of ash and tiny bits of char. I wonder if you could catch and/or redirect it to a spot where it'd do some good?

I often dump my quench water on plants that I either know or guess would prefer a more alkaline soil.  Our soil here is naturally very acidic.   I put it on asparagus, cactus, cherries, crandall currants, and mulberries.

I get inspired by the projects that you do, William, but I  have to remind myself that I am a low skilled, simple projects person.  I enjoy what I can do, but it is on a much, much smaller scale.

John S
PDX OR

John, you get stuff done, which I admire amdn frankly envy!

After the first burn, I put together a combination of 1.25" hardware to plug the hole.
A real buckhead fitting cost to much and would have taken too long to get.
It not happy with what I have so far, but I will be able to make it work.
I shouldhave drilled a a 1/2"-3/4"  hole in the other end, and cut the 111" dia hole around the bung, removing it entirely.
That would have been much easier, but if I only pursued things I was going to do right the first time I'd hardly do anything at all!

Anyhoo, the I'm probably going to skip ahead to using the keg as the inner vessel and craft something else as  the outer cylinder/shroud that delivers  preheated air.
Doing the math, my  inner bucket set up only holds about 3 gallons of combustibles.
If I use the entire top half of the keg as a pyrolysis chamber, that number will be closer to 7 gallons.
This why I'm abandoning the paint bucket for this b uild though it remains a viable tlud on its own.
This tlud is for larger materials, like pallet wood chunks, so every bit of volume helps.
If my bid to make it self dousing  fails , I will plug some holes and use the entire keg as the pyrolysis chamber.

I can do without the outer cylinder/shroud but it really seems to aid in clean combustion.
I have the cylindrical sheet metal skin of a water heater that has been sitting and waiting to be used
It's about 20" in diameter and 60" long.
I after I cult it down to  size and add air inlets at the bottom,I think I will add some centering guides but not attach it directly to the keg.
Keeping it modular and optional  seems like a good plan.