Agree with others, electric heating uses resistance to do that, and it would not work at 18v@6a. Put it this way, even at their lower setting, small electric space heaters are at 600 watts....so doing this on a toy train layout in a safe way would be a non starter.
Besides, part of the fun of live steam is that alcohol has been used to generate steam (probably not on trains I would suspect, but it was used on some early steam cars), so it is somewhat prototypical
.
The other downside of live steam probably will be that what it puts out may be kind of gunky, or will fall on items on the layout that will attract grime.
