FLAMELESS COMBUSTION ELLIS. 



645 



Fig. 1. 



-Crucible furnace heated by sur- 

 face COMBUSTION. 



to the melting of metals or alloys which are fusible at temperatures 

 below about 600° C, and also in relation to steam raising in multi- 

 tubular boilers. By this proc- 

 ess, much higher temperatures 

 are attainable with a given gas 

 than by the ordinary methods 

 of flame combustion without a 

 I'egenerative system. In fact, 

 w^e have found that Avith any 

 gas of high calorific intensity 

 (such as coal gas, water gas, or 

 natural gas) , the upper practic- 

 able temperature limit is deter- 

 mined by the refractoriness of 

 the material composing the 

 chamber (i. e., the muffle or cru- 

 cible) to be heated, rather than 

 by the possibilities of the com- 

 bustion itself. In a crucible 

 fired by coal gas on this system 

 we have readily melted Seger 

 cone No. 39, w^hich, according to the latest determination of the 

 Eeichsanstalt in Berlin, melts at 1,880° C. We can also easily melt 



platinum, showing the 

 possibilities of the 

 method in regard to high 

 temperatures with gas- 

 fired furnaces. Using air 

 preheated to 500° C. with 

 coal gas, a temperature 

 estimated at somewhat 

 over 2,000° C. has been 

 attained. A very resist- 

 ant chromite, not melting 

 at 1,880° C, was fused in 

 this way. Crucibles of 

 alimdum are fused with- 

 out preheating the air. 



For the very high tem- 

 peratures obtained with 

 coal gas, water gas, or 

 natural gas. Prof. Bone 

 employs a bed composed 

 either of fragments of magnesia, which has been burned at a high 

 tempei'ature, or of a neutral and highly refractory material specially 



Pig. 2.— Surface combustion applied to a muffle 



FURNACE. 



