GAS MANUFACTURE 403 



The transition from the experimental to the practical stage proved fatal to the Settle- 

 Padfield system, whilst the Young and Glover became merged in the Glover- West pro- 

 cess, but since 1909 the three remaining systems have been working continuously, and 

 with later improvements are so successful that there is no doubt as to their gradually 

 largely supplanting the older forms of retort in English practice. 



The German intermittent verticals, or Dessau retorts, have been at work at Sunderland 

 since 1909, where at the Ayres Quay works there is an installation of a bench of six beds of 

 ten retorts each. The retorts are 13 feet i^ inches high, tapering from o 

 inches by 22 J inches at the top to 13! by 27? inches at the bottom. The bench 

 carbonises 400 tons of coal per week, and yields between 12,000 and 13,000 cubic 

 feet of gas per ton. The coal is charged into the retorts from an overhead hopper, each 

 taking a little under half a ton, which requires twelve hours for complete carbonising, and 

 during the last two hours steam is passed at a slow rate through the charge, partly to increase 

 the volume of gas, and partly to prevent any sticking of the charge due to carbon deposited 

 on the inner face of the retort, which might interfere with the discharge of the coke when the 

 bottom door of the retort was opened. The use of steam naturally increases the amount 

 of fuel used in the carbonisation, this amounting to 13.96 per cent of the weight of coal car- 

 bonised when no steam is used, and rising to 17.8 per cent when steam is employed, the 

 average of fuel used being about 15 per cent. 



Of the two continuous processes, the Woodall-Duckham has been the longest at work, 

 and there are numerous installations in Great Britain and other countries. The retorts are 

 25 feet in height with a sufficient taper to ensure the slip of the charge. The 

 3 kh t * me occu Pi e d in the travel of the coal from the hopper to the coke extractor 



ertfca/s" at tne bottom of the retort is seven or eight hours. The coke is removed by an 

 extractor, actuated by a ratchet and pawl arrangement on a grooved wheel, and 

 driven by a rocking shaft, and the coke then falls into a watersealed hopper, which is large 

 enough to take the amount drawn out during three revolutions of the extractor, or about 

 three hours' discharge. The coke can be quenched, if necessary, by a small spray of water 

 in the storage hopper, but the amount of water is limited, so that the coke is ejected in 

 practically a dry state and at a temperature of 140 F. The passage of the coal through the 

 retort is governed by the speed of the extractor, the supply of coal at the top of the retort 

 being arranged to keep the retort full, with the exception of a small space at the top where 

 the gas is led off, and which can be regulated in size by a sliding partition. The top of the 

 built-up retort is closed by an iron casting carrying the coal feed, the gas exit pipe, and the 

 sliding partition. The coal feed is a gas-tight hopper fixed eccentrically to the retort and 

 closed by a gas-tight valve, through which the hopper can be filled from another store 

 hopper above. This operation takes a very short time and is necessary only once in three 

 hours, the size of the lower hopper being so calculated as to hold the coal to give the charge 

 of coke removed by the three revolutions of the extractor at the bottom of the retort. 



In any process where automatic and continuous action is arranged for, the working 

 parts of the apparatus are apt to become rather complex, but in spite of the objections 

 raised from time to time against continuous carbonisation, the system is an established 

 success, being at work also in America and on the European Continent. 



The other process based on the continuous carbonisation of coal is the Glover-West. 



In this system an economy is obtained by utilising the heat from the cooling hopper for 



the coke to regenerate the air for the secondary combustion in the flues, this 



Glover-West ma k m g a slight decrease in the fuel consumption, which is given as 10.3 per 



cent. Complete installations have been at work for some time at St. Helens 



and at Droylsden, the latter consisting of two settings of eight retorts, each setting being 



subdivided into two sections of four retorts, for convenience in working. The output of the 



plant is rated at 500,000 cubic feet of gas per twenty-four hours. 



The retorts are 20 feet long, oval in section, and with a slightly increasing taper from 

 the top to the bottom. The coke falls into a cast iron chamber at the bottom of the retorts, 

 and round it the secondary air supply is led. Beneath the coke chamber is the extractor, 

 a slowly revolving vertical screw, driven from a small gas engine by means of an arrangement 

 of levers and ratchet wheels. The coke is discharged into a bottom hopper, from which it is 

 removed about every two hours. The top of the retort is similar to that of the Woodall- 

 Duckham, being provided with the coal feeding hopper, gas exit pipe, and partition. 



Extended experience with these systems has shown that in spite of their apparent com- 

 plexity, they work smoothly and noiselessly, with complete absence of smoke and steam, 

 which is in sharp contrast with the old methods of carbonisation. The wear and tear, also, 

 are very small. A great advantage of the process is the uniformity in composition of 

 the gas, whereas in the old horizontal retorts the composition of the gas evolved at the 

 commencement and at the end of the carbonisation varied enormously, and uniformity in 

 composition was left to the mixation of the gas from many benches in the holder. 



Intermediate between the old processes of carbonisation and coke oven recovery plant 

 comes what is known as "chamber carbonisation." By this method charges of three to 



