Place of Test: 1. London, England; 2. Peacedale, R. I.; 3. Cincinnati, O.; 4. Pittsburgh, Pa.; 5. Chicago, Ill.; 6. Springfield, O.; 7. San Francisco, Cal.

In all the above tests the furnace was supplied with a fire-brick arch for preventing the radiation of heat from the coal directly to the boiler.

Weathering of Coal. (I. P. Kimball, Trans. A. I. M. E., viii. 204.)— The practical effect of the weathering of coal, while sometimes increasing its absolute weight, is to diminish the quantity of carbon and disposable hydrogen and to increase the quantity of oxygen and of indisposable hydrogen. Hence a reduction in the calorific value.

An excess of pyrites in coal tends to produce rapid oxidation and mechanical disintegration of the mass, with development of heat, loss of coking power, and spontaneous ignition.

The only appreciable results of the weathering of anthracite within the ordinary limits of exposure of stocked coal are conned to the oxidation of its accessory pyrites. In coking coals, however, weathering reduces and finally destroys the coking power, while the pyrites are converted from the state of bisulphide into comparatively innocuous sulphates.

Richters found that at a temperature of 158° to 180° Fahr., three coals lost in fourteen days an average of 3.6% of calorific power. (See also paper by R. P. Rothwell, Trans. A. I. M. E., iv. 55.)

COKE.

Coke is the solid material left after evaporating the volatile ingredients of coal, either by means of partial combustion in furnaces called coke ovens, or by distillation in the retorts of gas-works.

Coke made in ovens is preferred to gas coke as fuel. It is of a dark-gray color, with slightly metallic lustre, porous, brittle, and hard.

The proportion of coke yielded by a given weight of coal is very different for different kinds of coal, ranging from 0.9 to 0.35.

Being of a porous texture, it readily attracts and retains water from the atmosphere, and sometimes, if it is kept without proper shelter, from 0.15 to 0.20 of its gross weight consists of moisture.

Analyses of Coke,

(From report of John R. Procter, Kentucky Geological Survey.)

Experiments in Coking. CONNELLSVILLE Region.
(John Fulton, Amer. Mfr., Feb. 10, 1893.)

Per cent of Yield.

66

92.38

7.21

0.562

66

93.23

5.69

0.749

41,650 340

1365 24,850 26,215 00.82 3.28 59.66 62.94 36.24

These results show, in a general average, that Connellsville coal carefully coked in a modern beehive oven will yield 66.17% of marketable coke, 2.30% of small coke or braize, and 0.82% of ash.

Per Cent

Lost.

The total average loss in volatile matter expelled from the coal in coking amounts to 30.71%.

The modern beehive coke oven is 12 feet in diameter and 7 feet high at crown of dome. It is used in making 48 and 72 hour coke.

In making these tests the coal was weighed as it was charged into the oven; the resultant marketable coke, small coke or braize and ashes weighed dry as they were drawn from the oven.

Coal Washing.-In making coke from coals that are high in ash and sulphur, it is advisable to crush and wash the coal before coking it. A coalwashing plant at Brookwood, Ala., has a capacity of 50 tons per hour. The average percentage of ash in the coal during ten days' run varied from 14% to 21%, in the washed coal from 4.8% to 8.1%, and in the coke from 6.1% to 10.5%. During three months the average reduction of ash was 60.9%. (Eng. and Mining Jour., March 25, 1893.)

Recovery of By-products in Coke Manufacture.-In Germany considerable progress has been made in the recovery of by products. The Hoffman-Otto oven has been most largely used, its principal feature being that it is connected with regenerators. In 1884 40 ovens on this system were running, and in 1892 the number had increased to 1209.

A Hoffman-Otto oven in Westphalia takes a charge of 64 tons of dry coal and converts it into coke in 48 hours. The product of an oven annually is 1025 tons in the Ruhr district, 1170 tons in Silesia, and 960 tons in the Saar district. The yield from dry coal is 75% to 77% of coke, 2.5% to 3% of tar, and 1.1% to 1.2% of sulphate of ammonia in the Ruhr district; 65% to 70% of coke, 4% to 4.5% of tar, and 1% to 1.25% of sulphate of ammonia in the Upper Silesia region and 68% to 72% of coke, 4% to 4.3% of tar and 1.8% to 1.9% of sulphate of ammonia in the Saar district. A group of 60 Hoffman ovens, therefore, yields annually the following:

Ruhr

District.

Upper Silesia..........................
Saar.

Sulphate Ammonia,

tons.

40,500

An oven which has been introduced lately into Germany in connection with the recovery of by-products is the Semet-Solvay, which works hotter than the Hoffman-Otto, and for this reason 73% to 77% of gas coal can be mixed with 23% to 27% of coal low in volatile matter, and yet yield a good coke. Mixtures of this kind yield a larger percentage of coke, but, on the other hand, the amount of gas is lessened, and therefore the yield of tar and ammonia is not so great.

The yield of coke by the beehive and the retort ovens respectively is given as follows in a pamphlet of the Solvay Process Co.: Connellsville coal beehive, 66%, retort, 73%; Pocahontas: beehive, 62%, retort, 83%; Alabama: beehive, 60%, retort, 74%. (See article in Mineral Industry, vol. viii., 1900.)

References: F. W. Luerman, Verein Deutscher Eisenhuettenleute 1891, Iron Age, March 31, 1892; Amer. Mfr., April 28, 1893. An excellent series of articles on the manufacture of coke, by John Fulton, of Johnstown, Pa., is published in the Colliery Engineer, beginning in January, 1893.

Making Hard Coke.-J. J. Fronheiser and C. S Price, of the Cambria Iron Co., Johnstown, Pa., have made an improvement in coke manufacture by which coke of any degree of hardness may be turned out. It is accomplished by first grinding the coal to a coarse powder and mixing it with a hydrate of lime (air or water slacked caustic lime) before it is charged into the coke-ovens. The caustic lime or other fluxing material used is mechanically combined with the coke, filling up its cell walls. It has been found that about 5% by weight of caustic lime mixed with the fine coal gives the best results. However, a larger quantity of lime can be added to coals containing more than 5% to 7% of ash. (Amer. Mfr )

Generation of Steam from the Waste Heat and Gases of Coke-ovens. (Erskine Ramsey, Amer. Mfr., Feb. 16, 1894)-1 he gases from a number of adjoining ovens of the beehive type are led into a long horizontal flue, and thence to a combustion-chamber under a battery of boilers. Two plants are in satisfactory operation at Tracy City, Tenn., and two at Pratt Mines, Ala.

A Bushel of Coal.-The weight of a bushel of coal in Indiana is 70 lbs., in Penna. 76 lbs.; in Ala., Colo., Ga., Ill., Ohio, Tenn., and W. Va. it is 80 lbs. A Bushel of Coke is almost uniformly 40 lbs., but in exceptional

cases, when the coke is very light, 38, 36, and 33 lbs. are regarded as a bushel. In others, from 42 to 50 lbs are given as the weight of a bushel; in this case the coke would be quite heavy

Products of the Distillation of Coal.-S. P. Sadler's Handbook of Industrial Organic Chemistry gives a diagram showing over 50 chemical products that are derived from distillation of coal. The first derivatives are coal-gas, gas liquor, coal-tar, and coke. From the gas-liquor are derived ammonia and sulphate, chloride and carbonate of ammonia. The coal-tar is split up into oils lighter than water or crude naphtha, oils heavier than water-otherwise dead oil or tar, commonly called creosote,—and pitch. From the two former are derived a variety of chemical products.

From the coal-tar there comes an almost endless chain of known combinations. The greatest industry based upon their use is the manufacture of dyes, and the enormous extent to which this has grown can be judged from the fact that there are over 600 different coal-tar colors in use, and many more which as yet are too expensive for this purpose. Many medicinal preparations come from the series, pitch for paving purposes, and chemicals for the photographer, the rubber manufacturers and tanners, as well as for preserving timber and cloths.

The composition of the hydrocarbons in a soft coal is uncertain and quite complex; but the ultimate analysis of the average coal shows that it approaches quite nearly to the composition of CH, (marsh-gas). (W. H. Blauvelt, Trans. A. I. M. E., xx. 625.)

WOOD AS FUEL.

Wood, when newly felled, contains a proportion of moisture which varies very much in different kinds and in different specimens, ranging between 30% and 50%, and being on an average about 40%. After 8 or 12 months' ordinary drying in the air the proportion of moisture is from 20 to 25%. This degree of dryness, or almost perfect dryness if required, can be produced by a few days' drying in an oven supplied with air at about 240° F. When coal or coke is used as the fuel for that oven, 1 lb. of fuel suffices to expel about 3 lbs. of moisture from the wood. This is the result of experiments on a large scale by Mr. J. R. Napier. If air dried wood were used as fuel for the oven, from 2 to 21⁄2 lbs. of wood would probably be required to produce the same effect.

The specific gravity of different kinds of wood ranges from 0.3 to 1.2. Perfectly dry wood contains about 50% of carbon, the remainder consisting almost entirely of oxygen and hydrogen in the proportions which form water. The coniferous family contain a small quantity of turpentine, which is a hydrocarbon. The proportion of ash in wood is from 1% to 5%. The total heat of combustion of all kinds of wood, when dry, is almost exactly the same, and is that due to the 50% of carbon.

The above is from Rankine; but according to the table by S. P. Sharpless in Jour. C. I. W., iv. 36, the ash varies from 0.03% to 1.20% in American woods, and the fuel value, instead of being the same for all woods, ranges from 3667 (for white oak) to 5546 calories (for long-leaf pine) = 6600 to 9883 British thermal units for dry wood, the fuel value of 0.50 lbs. carbon being 7272 B. T. U.

Heating Value of Wood.-The following table is given in several books of reference, authority and quality of coal referred to not stated.

The weight of one cord of different woods (thoroughly air-dried) is about as follows:

Hickory or hard maple.... 4500 lbs. equal to 1800 lbs. coal. (Others give 2000.) White oak....

1715.)

3850

66

1540

66

66

1450.)

1050.)

925.)

Beech, red and black oak.. 3250
Poplar, chestnut, and elm.. 2350
The average pine..

Referring to the figures in the last column, it is said: From the above it is safe to assume that 24 lbs. of dry wood are equal to 1 lb. average quality of soft coal and that the full value of the same weight of different woods is very nearly the same-that is, a pound of hickory is worth no more for fuel than a pound of pine, assuming both to be dry. It is important that the wood be dry, as each 10% of water or moisture in wood will detract about 12% from its value as fuel.

Taking an average wood of the analysis C 51%, H 6.5%, O 42.0%, ash 0.5%, perfectly dry, its fuel value per pound, according to Dulong's formula, V –

[14,500 C+62,000 (H-],

is 8170 British thermal units. If the wood, as ordinarily dried in air, contains 25% of moisture, then the heating value of a pound of such wood is three quarters of 8170 6127 heat-units, less the heat required to heat and evaporate the 4 lb. of water from the atmospheric temperature, and to heat the steam made from this water to the temperature of the chimney gases, say 150 heat-units per pound to heat the water to 212, 966 units to evaporate it at that temperature, and 100 heat-units to raise the temperature of the steam to 420° F., or 1216 in all = 204 for 4 lb., which subtracted from the 6127, leaves 5824 heat-units as the net fuel value of the wood per pound, or about 0.4 that of a pound of carbon.

The following table, prepared by M. Violette, shows the proportion of water expelled from wood at gradually increasing temperatures:

The wood operated upon had been kept in store during two years. When wood which has been strongly dried by means of artificial heat is left exposed to the atmosphere, it reabsorbs about as much water as it contains in its air-dried state.

A cord of wood = 4 × 4 × 8 = 128 cu. ft. About 56% solid wood and 44% interstitial spaces. (Marcus Bull, Phila., 1829. J. C. I. W., vol. i. p. 293.) B. E. Fernow gives the per cent of solid wood in a cord as determined offi cially in Prussia (J. C. I. W., vol. iii. p. 20):

Timber cords, 74.07% 80 cu. ft. per cord;

Firewood cords (over 6" diam.), 69.44% = 75 cu. ft. per cord;
"Billet" cords (over 3" diam.), 55.55% = 60 cu. ft. per cord;
"Brush" woods less than 3' diam., 18.52%; Roots, 37.00%.

CHARCOAL.

Charcoal is made by evaporating the volatile constituents of wood and peat, either by a partial combustion of a conical heap of the material to be charred, covered with a layer of earth, or by the combustion of a separate portion of fuel in a furnace, in which are placed retorts containing the material to be charged.

According to Peclet, 100 parts by weight of wood when charred in a heap yield from 17 to 22 parts by weight of charcoal, and when charred in a retort from 28 to 30 parts.

This has reference to the ordinary condition of the wood used in charcoalmaking, in which 25 parts in 100 consist of moisture. Of the remaining 75 parts the carbon amounts to one half, or 37% of the gross weight of the wood. Hence it appears that on an average nearly half of the carbon in the

wood is lost during the partial combustion in a heap, and about one quarter during the distillation in a retort.

To char 100 parts by weight of wood in a retort, 12% parts of wood must be burned in the furnace. Hence in this process the whole expenditure of wood to produce from 28 to 30 parts of charcoal is 112% parts; so that if the weight of charcoal obtained is compared with the whole weight of wood expended, its amount is from 25% to 27%; and the proportion lost is on an average 111⁄2 371⁄2 = 0.3, nearly.

According to Peclet, good wood charcoal contains about 0.07 of its weight of ash. The proportion of ash in peat charcoal is very variable, and is estimated on an average at about 0.18. (Rankine.)

Much information concerning charcoal may be found in the Journal of the Charcoal-iron Workers' Assn., vols. i. to vi. From this source the following notes have been taken:

Yield of Charcoal from a Cord of Wood.-From 45 to 50 bushels to the cord in the kiln, and from 30 to 35 in the meiler. Prof. Egleston in Trans. A. I. M. E., viii. 895, says the yield from kilns in the Lake Champlain region is often from 50 to 60 bushels for hard wood and 50 for soft wood; the average is about 50 bushels.

The apparent yield per cord depends largely upon whether the cord is a full cord of 128 cu. ft. or not.

In a four months' test of a kiln at Goodrich, Tenn., Dr. H. M. Pierce found results as follows: Dimensions of kiln-inside diameter of base, 28 ft. 8 in.; diam. at spring of arch, 26 ft. 8 in.; height of walls, 8 ft.; rise of arch, 5 ft.; capacity, 30 cords. Highest yield of charcoal per cord of wood (measured) 59.27 bushels, lowest 50.14 bushels, average 53.65 bushels.

No. of charges 12, length of each turn or period from one charging to another 11 days. (J. C. Ï. W., vol. vi. p. 26.)

Results from Different Methods of Charcoal-making.

Fir and white-pine
wood, mixed. Av. 25
lbs. per cu. ft.

72.224 7 59.5

13.3

52.5 18 3 43.9

13.3

Av. good yellow pine) 54.7 22.0 45.0

17 5

weighing abt. 25 lbs.

per cu. ft.

42.9'17.1 35 0

17.5

Swedish meilers, av, results American kilns, av. results American meilers, av. results........ Consumption of Charcoal in Blast-furnaces per Ton of Pig Iron; average consumption according to census of 1880, 1.14 tons charcoal per ton of pig. The consumption at the best furnaces is much below this average. As low as 0 853 ton, is recorded of the Morgan furnace; Bay furnace, 0.858; Elk Rapids, 0.884. (1892.)

Absorption of Water and of Gases by Charcoal.-Svedlius, in his hand-book for charcoal-burners, prepared for the Swedish Government, says: Fresh charcoal, also reheated charcoal, contains scarcely any water but when cooled it absorbs it very rapidly, so that after twenty-four hours, it may contain 4% to 8% of water. After the lapse of a few weeks the moisture of charcoal may not increase perceptibly, and may be estimated at 10% to 15%, or an average of 12%. A thoroughly charred piece of charcoal ought, then, to contain about 84 parts carbon, 12 parts water, 3 parts ash, and 1 part hydrogen.