STEAM BOILERS 



107 



chamber g surrounding the magazine. From g the air passes 

 upwards through hollow cast-iron tuyere blocks and out through 

 the openings, or tuyeres e. The gas formed in the magazine, 

 mixed with the jets of air from the tuyeres, risdfe through the 

 burning fuel above, where it is subjected to a sufficiently high 

 temperature to secure its combustion. Nearly all the air for 

 burning the coal is supplied through the tuyeres, only a very 

 small portion of the supply coming through the grate. The 



FIG. 



ashes and clinkers are gradually forced to the sides of the grate 

 against the side walls of the furnace, from which they are 

 removed from time to time through doors in the furnace front 

 similar to the fire-doors of an ordinary furnace. In other 

 words, owing to the construction of the underfeed stoker, 

 the fire must periodically be cleaned from clinkers and the 

 ashes removed by hand. 



