THE TECHNOLOGIST. [June 1, 1864. 



528 PRODUCTS OF DISTILLATION OF COAL. 



of coal would be introduced in fifteen or twenty minutes, a rapidity 

 which was most desirable for preserving the heat of the oven. When 

 the charge was being withdrawn and replaced, the gas from the other 

 ovens was allowed to pass continually into the fire-place, so that the 

 floor was kept hot, and the gas accordingly began to show itself, above 

 the opening at the top, only a few minutes after the closing of the door. 

 This opening was then hermetically sealed, and the valve in the outlet pipe 

 being raised, the communication was re-established between the interior 

 of the oven and the great common flue. The products of the great dis- 

 tillation were drawn off by the draught of the chimney, together with 

 the condensation of the liquid, aud the cooling of the gaseous products. 

 After circulating in the great general flue, the products penetrated into 

 the condensating apparatus, wdiere they deposited most of the tar and 

 ammoniacal liquor, and returned to the ovens by the small general flue, 

 whence the gas, purified and dried, passed to each fire. 



The time occupied in charring varied with the nature of the coal, and 

 the density desired for the coke, and with the arrangement of the oven. 

 At St. Etienne it took upwards of seventy-two hours, with rich coals, 

 while at Torteron the time occupied was only twenty-four hours, with the 

 rather poor but flaring coals of Commentry. 



As to the cost, it was stated that the expense of altering each oven at 

 St. Etienne was about 20Z., and that as the value of the additional yield 

 from each oven ought to be about 601. per annum, this outlay should be 

 repaid by four months' work. 



It was asserted that the supplementary products due to these arrange- 

 ments were, a larger yield of coke, and all the tar, the ammoniacal 

 liquors and the gas, which would be obtained from the same coals, if 

 distilled in the retorts of a gas manufactory. Thus, in the great coke 

 works at St. Etienne, the yield had been advanced from 58 - 8 to 

 69*3 per cent., and in the " Fonderies et Forges d'Alais" from 54'6 

 to 69'5 per cent. Generally speaking, with rich, or partially rich coals, 

 the increase in the yield of coke was from 10 to 15 per cent. As to the 

 tar, the proportion collected depended on the nature of the coal, and on 

 the care taken, both in the distillation of the coal and in the conden- 

 sation of its volatile products. It had averaged 2-53 per cent, at the 

 Forges d'Alais, 3 per cent, at Elonge, 325 per cent, at St. Etienne, and 

 had reached as high as 5 per cent, from the ovens of the Paris Gas 

 light Company, where only very bituminous coals were employed ; but 

 it was thought that there might be reckoned 3 per cent, of tar from the 

 bulk of the coal distilled. The proportion of ammoniacal liquors 

 depended also on the quantity of moisture contained in the coal ; but 

 it might be stated at a weight of not less than 10 lbs. of sulphate of 

 ammonia, and sometimes it w r as as much as ] 3 lbs. per ton of coal dis- 

 tilled. At the ovens of the Paris Gas Light Company, from 10,000 to 

 11,500 cubic feet of purified gas were generally obtained from a ton of 

 coal, which yielded from 69 to 70 per cent, of coke, fit for delivery to 

 the railway companies. 



