GAS. 



375 



a less extent. The coal in the gasogen is re- 

 newed from time to time, and the interior is 

 cleaned out at longer intervals, but the heat is 

 kept up for long periods. 



The distinctive difference between the mode 

 of applying the heat in this and in the ordinary 

 coal-gas process will be noticed. In making 

 gas from bituminous coal the material is heated 

 in close retorts set in a furnace. The heat is 

 applied to their exteriors. Fire-clay is not a 

 good conductor of heat, but the heat of the 

 furnace is pushed until the retort is heated 

 through. All the heat .the coal gets comes 

 through three inches of fire-clay. This is an 

 extremely wasteful way of applying heat. In 

 the Lowe process the heat is applied directly, 

 the same surface of the fire-brick being alter- 

 nately heated by the products of combustion, 

 and cooled by imparting its heat to the gases 

 passing over it. The candle-power of the gas 

 is under good control, being regulated by the 

 admission of naphtha or petroleum. 



The Strong Process. This is applied to the 

 production of hydrogen only. As in the former 

 method, at least two cupolas are essential, one 

 containing coal, the other fire-bricks. Assum- 



before it reaches the gasogen. Then, very 

 highly superheated, it passes downward through 

 the hot coal and out of the bottom of the cu- 

 pola, and is decomposed into water-gas. At 

 the top of the gasogen there is an aperture, 

 through which a quantity of coal-dust is ad- 

 mitted during the gas-making period. Re- 

 markable as it seems, the steam is so highly 

 superheated that its own heat is enough to 

 cause it to be decomposed by the coal-dust. 

 This is so true, that in the original process 

 the current was not drawn through the coal- 

 cupola at all. The gas was drawn off as soon 

 as the contact between the dust and steam had 

 been effected. But it was found that, though 

 the steam was well decomposed, the gas con- 

 tained a great deal of carbonic- acid gas. To 

 remedy this trouble, the gas was passed down- 

 ward through the hot coal. Thus in the Strong 

 process the air and steam go in exactly oppo- 

 site directions ; in the Lowe process they fol- 

 low the same course. The alternate periods of 

 heating and gas-making are sometimes very 

 short ; they have been reduced to five minutes 

 each. In this process the same system of di- 

 rect heating is employed, but no naphtha is 

 used, and a non-luminous heating gas is pro- 

 duced. The use of coal-dust is a noticeable 

 feature in the Strong process. Sometimes as 

 much as 25 per cent, of slack is used, effecting 

 a considerable saving in the cost of material. 



The Municipal Process. The first works to 

 adopt this process, frequently called the Tessi6 

 du Motay process, were the Municipal Gas- 

 Works of New York. In the Lowe process, 



FIG. 2. STRONG PROCESS. 



ing that the heating is taking place, the course the whole operation of gas-making is one, and 



of the operation is the same as that already de- 

 scribed for the Lowe process. When the heat- 

 ing period is over, the air is shut off and steam 

 is admitted, but the steam enters the apparatus 

 at the farther end of the regenerating cupola. 

 It passes through all the intensely heated brick 



can not be divided into steps. The Municipal 

 process, on the other hand, divides itself into 

 three phases : gas-generating, carbureting, and 

 roasting or fixing. The division makes the pro- 

 cess susceptible of closer watching and more 

 accurate adjustment. Whether this advantage 



