Shortround6
Major General
South African 1950s condensing tender. Narrow gauge rail 3' 6" apart.
Granted it is for engine making around 4000hp.
There are a number of fans in the center of the tender so it draws air through the vents/screens on the sides and exhausts the cooling air out the top.
The steam engine itself uses a fan to draw the air though the firebox and boiler to replace the draft provided by the steam exhaust but I don't think most steam road vehicles did that anyway? They used natural draft and not forced draft?
Comparisons between river boats and/or railroads vs road vehicle gets a little tough. You don't need a lot of power to move a boat/small ship very fast. Railroads have very shallow grades, a 3% grade is considered the practical limit and at 3% the load the locomotive can pull is fraction of what it can pull on level ground.
I just happened to run across a description of a 1930 2-8-0 German locomotive built for burning pulverized Lignite by AEG. I have no idea if they built more than one. Most of the details pertain to the tender and feed arrangements. Like a picture of the single cylinder engine used for powering the conveyer screws (max capacity 4360lb per hour) and the 7hp steam turbine powered fan for primary air. It does not give the locomotive's size or power except to say it was rated for train of 1415tons. Grade not given so assume level. The pulverized coal bunker size (a cylinder) was 6.5ft diameter and 13 feet long.
British fooled around with a few 'coal dust' powered locomotives as early as 1917(?) but that was to use up bituminous (black) coal dust that had fallen through the screens of the collieries.
Germans built 6(?) 2-10-0s in 1930/early 30s much like the 2-8-0 but from a different maker. I don't know how many other experiments were made. The East Germans did try again in the early 1950s.
It seems you can have simple/cheap with lower efficiency or complicated/expensive and decent efficiency.