SYMPOSIUM ON SCIENCE AND RECONSTRUCTION SI 



Below the grate is a couueotion bv which air is admitted 

 from a high-speed blower duriiig the blasting portion of 

 the operation. The air soon brings the fuel bed to a high 

 state of incandescence. During this blowing period the air 

 gas formed, which contains a considerable percentage of 

 carbon monoxide, is burned by a secondary air blast in the 

 carburetor and superheater, and some of the heat is stored 

 in the piles of staggered brick checkerwork with which 

 these chambers are tilled. The combustion products pass 

 through the open stack yalve into the air. When the fuel 

 bed and the checkerwork have attained the proper temper- 

 ature, the blowing is discontinued, the stack valve is 

 closed, and steam is then blown through the incandescent 

 fuel bed. 



The steam reacts with the carbon of the fuel, forming 

 carbon dioxide, carbon monoxide, and hydrogen. The car- 

 bon dioxide content of the gases leaving the generator is at 

 first low, but increases as the fuel bed cools. Since this 

 constituent is of course undesirable, the steaming process 

 is interrupted so soon as it becomes unduly prominent, and 

 the fire is again blasted with air. The gas produced during 

 the steaming, or run period as it is called, usually has a 

 heating value of about 300 B. t. u. per cubic foot. Since 

 most states require a heating value in the finished gas of 

 at least 565 B. t. u., as in Illinois, it is necessaiT to enrich 

 this "blue*- gas, as it is designated, by gas men. This is 

 accomplished by spraying oil onto the hot bricks in the 

 carburetor. The oil is broken up into vapor which mixes 

 with the "blue" water-gas, and this vapor by further con- 

 tact with the hot bricks in the superheater, becomes largely 

 fixed as a permanent gas which will not condense back 

 into oil when cooled. The carburetted gas passes through 

 the water seal of the wash box, W, and thence through 

 further apparatus where it is cooled, cleaned, and purified 

 before being distributed to the consumers. 



It is not to be assumed that the operation is so simple in 

 practice as just described. The blowing and steaming 

 periods have to be regulated with great care, not only as to 

 duration, but also in respect to the amount of air, steam, 

 and oil admitted. A small fraction of a minute added to or 

 subtracted from one of these periods has marked eft'ects on 

 the temperature balance of the machine and nearly all 

 modern gas sets are equipped with steam, air, and oil 



