Reply To: GPCS – is it the solution for poor coal
I agree entirely with David’s analysis. I am of the opinion that it is necessary to have some form of control system to regulate the quantity of steam being supplied to the grate.
It’s also interesting to consider this analysis with the discussion of various coal types currently being held on the Nat. Pres. forum.
It would be difficult to engineer a durable probe that could monitor the grate temperature directly, but as a half way house, my suggestion would be to provide a valve which shuts down the undergrate steam if the boiler pressure drops below, say 85%, of its nominal value. I’ve been advised that suitable valves are commercially available to achieve this. Admittedly, there are other reasons why the boiler pressure might fall, but I don’t think that shutting off the undergrate steam would be too much of a disadvantage.
The other point that needs considering is whether there is sufficient secondary air to burn the gases produced by the system (i.e. hydrogen and carbon monoxide). We seem to be assuming that sufficient secondary air passes through the firebox door, but is this actually the case? If I remember correctly, for “Red Devil” additional openings were created in the side of the firebox. Gases passing unburned through the chimney obviously represent a loss of usable energy. Perhaps it may be possible to monitor the carbon monoxide content in the smokebox gas.
Rather than cutting holes in the side of the firebox, and thus penetrating the pressure vessel, my preference would be to have secondary air pipes passing up alongside the grate from below the locomotive. This opens up the possibility of considering pre-heating the secondary air, using exhaust steam. (Preheating primary air could lead to further clinkering problems).