[Terrapreta] water gas?

[Gerald Van Koeverden]

Does anybody know if water-drenching very hot char, or injecting  
water into a charcoal kiln to arrest carbonization is dangerous?

David Hirst wrote me:

"This is the recipe for what I believe is called "Water Gas" in  
ironworks and a by-product
of making the coke used in blast furnaces. After coke is left once  
heat has driven off
all the hydrocarbons in coal - leaving carbon, then steam (ie water)  
is passed through
the coke, forming H2 and CO, a fairly high energy density gas, I  
believe often used in
the blast furnaces."

Does anybody have any experience with what would happen?  Maybe just  
a sizzling fizzle?

Gerrit