This is not part of the Baker boiler, and the drawing is a bit fuzzy, but I figured I'd throw this in while the camera was handy. This is a layout drawing of the economizer coil for my new/improved "M2012" rapid-natural-circulation boiler. 6 of these 2-path pancake coil units will be stacked up above the firebox/steam-generator section of the boiler. The economizer is the part of a boiler which removes the last bit of practically-recoverable heat from the burner gases, heating the incoming feed-water in the process, before exhausting the cooled gases from the boiler. Note the 2 squares drawn under the tube coil. The innermost square represents the edge of an infrared-reflecting baffle between the firebox and the economizer above it. The firebox is lined with a "waterwall" of vertical steel tubes, in which water circulates rapidly upward as radiant heat from the fire boils the water in the tubes. At full steam output, a minimum of 10 lbs of water circulates for every one lb of steam generated. As in standard natural-circulation water-tube boilers, no pumps, eductors, or other extra devices are required to initiate or maintain this rapid circulation. About half of the heat in the fuel is turned directly into steam at that stage. The exhaust gases from the firebox flow up to the economizer through the gap between the edge of baffle and the inner wall of the boiler [represented by the outer square], and almost no radiant heat reaches the economizer tubing. There will be other baffling, not shown in this drawing, which directs the hot gases through the gaps between the turns of the tubing, flowing over each of the 6 coils in succession. This economizer will have vertical gas up-flow and vertical water down-flow, rather than the horizontal inward/outward gas/water counterflow of the previously-planned Andy Patterson "1999 donut boiler" style economizer. The previous "donut" economizer was designed for my now-discarded "M2006" boiler design. Unlike the old economizer design, this new design gives complete "blowdown" for cleaning. A clean boiler is a happy boiler.
The new design avoids any need for an indexed "wash-out hook", as shown in the Baker boiler above. Some multi-path water-tube boilers, like the Baker, need to have the various coils blown down separately for cleaning.
[This page, August 10th, 2012]
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