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ClearSign - Firetube Boiler
A firetube boiler is a type of boiler in which hot gases pass from a combustion zone through one or many tubes running through a sealed container of water. The heat from the gases is transferred through the walls of the tubes by thermal conduction, heating the water and creating steam. Such boilers can be further classified as single pass, two, three or even four pass to denote the number of loops or passes the flue gases make prior to exiting via the stack.
There are two basic designs for firetube boilers. The typical design is the “wetback”, where the rear face of the combustion chamber is water-jacketed for additional heat extraction. The simpler, but less efficient “dryback” variation has the rear of the combustion chamber as an open, insulated box, backed or surrounded only by a sheetmetal.
Firetube boilers were used on virtually all steam locomotives in the horizontal form. Due to their higher heat density, horizontal fire-tube boiler is also typical in marine applications. Therefore, these boilers are commonly referred to as "scotch-marine" or more simply, "marine" type boilers. They also see usage in Residential Heating and in many industrial process for providing process heat and/or steam.
Clearsigns’s disruptive technology has taken such legacy boilers into the 21st century by enabling sub 5ppm NOx performance in a simple to use, automated package delivering > 5:1 turndown.