. Technical paper . character of the whirling motion of the gases leaving the fire box,which may be readily observed through the observation hole in the side wall of the Heineboiler, is indicated in fig-ure 26. In the figure Arepresents a current of airrising from the ash pit; Band B represent currentsof air introduced over thetop of the fuel bed throughopenings at the base ofthe furnace arch. It isnot improbable that plac-ing mixing structures inthe combustion chamberback of the grate to de-flect the flow lines of thegases would diminish thetime and space requiredfor complete ser
. Technical paper . character of the whirling motion of the gases leaving the fire box,which may be readily observed through the observation hole in the side wall of the Heineboiler, is indicated in fig-ure 26. In the figure Arepresents a current of airrising from the ash pit; Band B represent currentsof air introduced over thetop of the fuel bed throughopenings at the base ofthe furnace arch. It isnot improbable that plac-ing mixing structures inthe combustion chamberback of the grate to de-flect the flow lines of thegases would diminish thetime and space requiredfor complete series of tests to determine the effect of variations in the methodof mixing the air and furnace gases is contemplated as a part of thegeneral investigation of the combustion of fuel. One of the dim-culties in the way of the successful use of mixing structures in thecombustion chamber, especially at the higher rates of firing, is thatof obtaining materials that will withstand the high temperatures ofthe furnace Figure 26.—Section through stoker showing mixing ofgases caused by currents of air. INFLUENCE OF RATE OF HEATING COAL COMBUSTION. ON SPACE REQUIRED FOR The composition, as well as the amount, of volatile matter givenup by a given coal varies greatly with the temperature to which thecoal is heated and the rate of heating. The influence of tempera-ture on the amount and composition of the volatile matter distilledfrom various coals has been studied by Porter and Ovitz of the Bureau DISCUSSION OF RESULTS OF TESTS. 41 of They found, for example, the following values for thevolume of combustible gas given off in 10 minutes from 10 gramsof air-dried Pocahontas coal: Relation of temperature of furnace to volume of combustible gas. Temperature of furnace, ° C I 600 Volume of combustible gas, 50 700670 8001,570 9002,300 The amount of tar produced increases with increase of temperaturein about the same proportion as does the volume of combustible gases. The hea
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