FUEL BY-PRODUCTS 53 



retained in the coke than when slow carbonization is per- 

 mitted. With quick heating of 2 or 3 hours in the labor- 

 atory, the amount of nitrogen left in the coke from the same 

 kind of coal is from 60-70 %. When coal is distilled at a 

 very low temperature for the production of coalite, or other 

 similar semi-carbonized coal, the yield of ammonia is 

 smaller than when high temperatures are used as in gas or 

 coke production ; about 2\ pounds of ammonia per ton of 

 coal when partially distilled as against about 5 pounds when 

 fully carbonized. The presence of air in the retort results 

 in loss of ammonia by oxidation. Steam and hydrogen 

 sulphide conserve ammonia from oxidation in the retorts. 

 At temperatures below 150 C. (300 F.) the oxidation of 

 ammonia by air is negligible. 



" Mond " Gas. In the manufacture of Mond gas the 

 difficulty of using bituminous fuel for the production of 

 water gas has been removed. By blowing a large amount 

 of steam, with the amount of air necessary to produce gas 

 through coal undergoing combustion, the temperature of 

 the gas is kept sufficiently low to enable the major part of 

 the nitrogen in the coal to be obtained as ammonia. For 

 every ton of coal distilled, 2 J tons of steam are admitted. In 

 this process common bituminous slack is first fed into a 

 hopper at the top of a gas generator, where it undergoes 

 distillation, and the volatile products pass down through 

 the hot coal before joining the bulk of the gas leaving the 

 producer. By these means the tar is largely converted into 

 permanent gas, and the partly carbonized slack then passes 

 from the hopper into the body of the producer, where it 

 is acted upon by an air blast, which is saturated with 

 steam at 85 C. (185 F.) and superheated by waste heat 

 from the producer. The bottom of the generator is conical, 

 and is sealed in a tank of water used to receive the ashes, 

 which can be periodically removed without interrupting 

 the manufacture of gas. The hot gases, mixed with excess 

 of steam, leave the generator, and then pass through a heat 

 interchanger, parting with their heat to the air supply of 

 the generator and becoming themselves cooled in the process. 



