This paper is presented as a report for the Special Research Committee on the Removal of Ash as Molten Slag From Powdered-Coal Furnaces. The primary object of the investigation was to obtain data on the fluxing of coal-ash slags to enable users of slagging-type boilers to increase the fluidity of the deposited ash should it not be possible to tap at available furnace temperatures. Studies were made using a platinum-wound furnace, supplemented by a gas furnace with a 32-in. by 28-in. hearth. A standard of fluidity desirable for easy tapping was established, and the results were expressed as the temperature necessary to produce this fluidity, designated the flow temperature. Values for flow temperature in terms of the chemical composition of the ash, or ash plus flux, were determined for a range of ashes found in American coals, and for additions of the following fluxes: iron ore, limestone, dolomite, fluorspar, saltcake, steel slags, and some less important minerals. It is deduced that limestone or dolomite would be the most economical material to use for slagging-type boilers as now built, and from a diagram the quantity of flux can be computed. The investigation was carried beyond present requirements for slagging-type boilers and to flow temperatures below 2400 deg. fahr. A complete diagram is given for coal ash-lime-iron showing the flow temperature plotted against composition.

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