FUELS AND THEIR UTILIZATION. 45 



subjecting them to the coking in retorts and ovens of more modern and re- 

 cent construction. The results have been quite satisfactory; the coke is ob- . 

 tained in larger pieces, and hard enough to stand transportation without 

 breakage. 



It is used for fuel, lamp black, in filters, and for the manufacture of gun- 

 powder; more frequently, however, it is manufactured for use in smelting 

 works. The largest amount of the product is secured when the process is so 

 conducted that no carbon of the coal, or but little of it, is burned through 

 admission of air, and when the retorts are kept at a uniform heat in all their 

 parts during the coking process. The efforts of experts engaged in this^in- 

 dustry have been directed, from its beginning up to the present, to obtain a 

 more perfect construction of the ovens for increasing their"producing capac- 

 ity and saving fuel. 



It is now everywhere conceded that the experiments so patiently conducted 

 through many years have been successful, and that though the process may 

 admit of further improvements, the results obtained so far have been highly 

 satisfactory. A plant consisting of a number of furnace ovens was used in 

 Belgium very early. The ovens were of small dimensions with a large num 

 ber of flues, passing below the floor, meandering along their sides, and con- 

 ducting the distilling vapors of one oven to the next, where they serve to 

 heat the coal. An admission of air into the horizontal canals secured the 

 burning of the gas and a full utilization of its heating capacity. 



A coke of excellent quality is also obtained from the refuse coke remain- 

 ing in the retorts after the distillation of lignite for the manufacture" of min- 

 eral oils and paraffine. The material is ground to a line powder, well mixed 

 with from eight to ten per cent of tar, and formed into briquettes which are 

 heated in retorts with the distilling vapors. 



An oven for the manufacture of ' lignite coke of the following construction 

 was long successfully used in Duerkheim a. d. Haardt, Bavaria, Germany, 

 where a seam of brown coal occurs about three feet thick. The material is, 

 however, so crumbling that it is impossible to mine it in pieces of a size suit- 

 able for burning purposes, and on that account it was considered perfectly 

 worthless till it was found that it could be manufactured into coke of the 

 finest quality. The product obtained is so superior an article that it has been 

 successfully used as filter coal, as lamp black, and in gunpowder factories. 

 The coking of the lignite is effected in an oven containing two ranges of 

 cylindrical retorts of fire clay, generally twelve in number, about eighteen 

 inches in diameter and eight feet high. The filling of the retorts takes 

 place from above through cast iron cylinders supplied with covers of the same 

 material. The retorts are connected below with cast iron cones immersed 

 about four to nine inches in water contained in a shallow slanting brick 



