Mance: Quarry Industry of Southern Indiana 157 



follows: (1) air jets, (2) steam jets, (3) the Eldred process, 

 (4) suction process. 



In the first process, jets of air are forced under the grates 

 and the fire boxes are kept tight on the same principle as forced 

 draft under a boiler. 



In the second method, steam jets are inserted up thru the 

 grate bars to give the necessary force to the upward currents 

 of gas. 



The Eldred process is a combination of the two methods in 

 which steam and air jets are forced into the kiln and suction fans 

 take away the waste gases. 



The fourth method is to apply suction fans at the top of the 

 kiln to draw off the waste gases as fast as they are formed. 



There is no question as to the fuel economy with any of these 

 methods for increasing the draft, but as to their relative value 

 expert engineers are not at all agreed. Of course, the use of re- 

 inforced draft in the manufacture of lime is a source of danger 

 if not properly handled since careless handling is sure to give an 

 inferior product and the danger of overburning is much greater. 

 A carelessly burned product, in addition to being inferior for use, 

 is also inferior in its keeping properties. These difficulties would 

 be lessened if the lime were hydrated before it is put on the market 



One hundred pounds of good limestone will yield from 56 

 to 58 pounds of lime, but the shrinkage in volume does not ex- 

 ceed 15 per cent and is usually much less. There is little differ- 

 ence in the hardness of lime and limestone, but the lime is much 

 more porous and when acted upon by water it falls into a powder. 



Pure lime is infusible at the temperature of the oxyhydrogen 

 flame and is therefore used in the production of the calcium 

 light. For light pencils the lime must be very pure since any 

 impurities cause it to fuse and form a glass slag. Lime is a power- 

 ful base and reacts with acids to form salts of calcium. 



With the development of the use of gas producers and pro- 

 ducer gas in all lines of industry, the increased use of gas in the 

 manufacture of lime is only a matter of time. Several types 

 of gas producers are in use at the present time. The Morgan 

 system is one of the oldest of these. It consists of a cylindrical 

 steel-plate shell which extends into a water-filled ash pan. The 

 fuel is automatically fed in at the top of the producer and scattered 

 over the entire fuel bed. A jet of air and steam is introduced 

 thru a central tuyere in the bottom of the producer. All the 

 operations are continuous and automatic and the ashes are 



