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Indiana University Studies 



therefore that the time has come to begin casting about for some 

 more economical type of power unit. The rapid development 

 of the gas producer and gas engine seems to promise the most 

 reliable substitute for the steam plant. It is confessed by every 

 good engineer that the steam plant that can utilize 12 per cent 

 of the energy in the coal is exceptional, and this can only be 

 reached in the best equipped and most modern large-unit plants. 



It has long been observed that when coal is thrown upon a 

 hot fire a portion of it bursts into flame, or goes off as gases and 

 smoke. This portion is known as the volatile matter of the coal. 

 The solid portion remaining behind has been called coke, and this 

 part consists largely of carbon but also contains the ash or non- 

 burning part of the coal. When coal is treated in retorts for the 

 coal gas, the coke remains behind as a by-product. It was found 

 that this coke, or at least the carbon in it, could be burned into 

 carbon monoxide provided the supply of oxygen was kept low 

 enough so that the formation of any considerable quantity of 

 carbon dioxide was impossible. This led to the modern process 

 of producing gas from coal by passing a moderate supply of air 

 with or without steam thru a thick fuel bed at a high temperature. 

 In this way the combustible matter of the coal can be driven off 

 as gas, without the production of coke. This gas is called pro- 

 ducer gas and the apparatus used is called a gas producer. There 

 are at present manufactured in this country three distinct types of 

 gas producers: the suction producer, the pressure producer, 

 and the down-draft producer. There are also combinations of 

 the up-draft and the down-draft producer, called double-zone 

 producers. In the suction producer the draft of air thru the 

 producer is produced by the suction of the engine cylinder. In 

 this type the supply of air is liable to be enough to interfere with 

 the production of a satisfactory gas and so steam must be added 

 to the draft. The necessary steam is generated at atmospheric 

 pressure by the hot gases leaving the producer and is drawn into 

 the producer with the air supply. As this mixture of air and steam 

 comes into contact with the highly-heated lower part of the fuel 

 bed, the oxygen of the air and the oxygen of the steam combine 

 with the carbon to form carbon dioxide. As the carbon dioxide 

 passes up thru the higher parts of the fuel bed it is reduced to the 

 monoxide, and the hydrogen in the steam passes on with the 

 carbon monoxide formed. 



In the pressure producer the air is driven into the producer 

 under pressure and the gas is stored in tanks for use in the engine. 



