17.—Peat as a source of illuminating gas.

Prof Pettenkofer, of Munich, was the first to succeed in making illuminating gas from wood; and peat, when operated according to his method, furnishes also a gas of good quality, though somewhat inferior to wood-gas in illuminating power.

It is essential, that well-dried peat be employed, and the waste heat from the retorts may serve in part, at least, for the drying.

The retorts must be of a good conducting material; therefore cast iron is better than clay. They are made of the [symbol: D] form, and must be relatively larger than those used for coal. A retort of two feet width, one foot depth, and 8 to 9 feet length, must receive but 100 lbs. of peat at a charge.

The quantity of gas yielded in a given time, is much greater than from bituminous coal. From retorts of the size just named, 8000 to 9000 cubic feet of gas are delivered in 24 hours. The exit pipes must, therefore, be large, not less than 5 to 6 inches, and the coolers must be much more effective than is needful for coal gas, in order to separate from it the tarry matters.

The number of retorts requisite to furnish a given volume of gas, is much less than in the manufacture from coal. On the other hand, the dimensions of the furnace are considerably greater, because the consumption of fuel must be more rapid, in order to supply the heat, which is carried off by the copious formation of gas.

Gas may be made from peat at a comparatively low temperature, but its illuminating power is then trifling. At a red heat alone can we procure a gas of good quality.

The chief impurity of peat-gas is carbonic acid: this amounts to 25 to 30 per cent. of the gas before purification, and if the peat be insufficiently dried, it is considerably more. The quantity of slaked lime that is consumed in purifying, is therefore much greater than is needed for coal-gas, and is an expensive item in the making of peat-gas.

While wood-gas is practically free from sulphur compounds and ammonia, peat-gas may contain them both, especially the latter, in quantity that depends upon the composition of the peat, which, as regards sulphur and nitrogen, is very variable.

Peat-gas is denser than coal-gas, and therefore cannot be burned to advantage except from considerably wider orifices than answer for the latter, and under slight pressure.

The above statements show the absurdity of judging of the value of peat as a source of gas, by the results of trials made in gas works arranged for bituminous coal.

As to the yield of gas we have the following data, weights and measures being English:—

100 lbs. of peat of medium quality from Munich, gave REISSIG 303 cub. ft. " air-dry peat from Biermoos, Salzburg, gave RIEDINGER 305 " " very light fibrous peat, gave REISSIG 379 to 430 " " Exter's machine-peat, from Haspelmoor, gave 367 "

Thenius states, that, to produce 1000 English cubic feet of purified peat-gas, in the works at Kempten, Bavaria, there are required in the retorts 292 lbs of peat. To distil this, 138-1/2 lbs. of peat are consumed in the fire; and to purify the gas from carbonic acid, 91-1/2 lbs. of lime are used. In the retorts remain 117 lbs. of peat coal, and nearly 6 lbs. of tar are collected in the operation, besides smaller quantities of acetic acid and ammonia.

According to Stammer, 4 cwt. of dry peat are required for 1000 cubic feet of purified gas.

The quality of the gas is somewhat better than that made from bituminous coal.

18.—The examination of Peat as to its value for Fuel, begins with and refers to the air-dry substance, in which:

1.—Water is estimated, by drying the pulverized peat, at 212 deg., as long as any diminution of weight occurs. Well-dried peat-fuel should not contain more than 20 per cent. of water. On the other hand it cannot contain less than 15 per cent., except it has been artificially dried at a high temperature, or kept for a long time in a heated apartment.

2.—Ash is estimated by carefully burning the dry residue in 1. In first-rate fuel, it should amount to less than 3 per cent. If more than 8 per cent., the peat is thereby rendered of inferior quality, though peat is employed which contains considerably more.

3.—Sulphur and phosphorus are estimated by processes, which it would be useless to describe here. Only in case of vitriol peats is so much sulphur present, that it is recognizable by the suffocating fumes of sulphuric acid or of sulphurous acid, which escape in the burning. When peat is to be employed for iron manufacture, or under steam boilers, its phosphorus, and especially its sulphur, should be estimated, as they injure the quality of iron when their quantity exceeds a certain small amount, and have a destructive effect on grate-bars and boilers. For common uses it is unnecessary to regard these substances.

4.—The quantity of coal or coke yielded by peat, is determined by heating a weighed quantity of the peat to redness in an iron retort, or in a large platinum crucible, until gases cease to escape. The neck of the retort is corked, and when the vessel is cool, the coal is removed and weighed. In case a platinum crucible is employed, it should have a tight-fitting cover, and when gases cease to escape, the crucible is quickly cooled by placing it in cold water.

Coal, or coke, includes of course the ash of the peat. This, being variable, should be deducted, and the ash-free coal be considered in comparing fuels.

5.—The density of peat-fuel may be ascertained by cutting out a block that will admit of accurate measurement, calculating its cubic contents, and comparing its weight with that of an equal bulk of water. To avoid calculation, the block may be made accurately one or several cubic inches in dimensions and weighed. The cubic inch of water at 60 deg. F., weighs 252-1/2 grains.

FOOTNOTES:

[10] The apparent specific gravity here means the weight of the mass,—the air-filled cavities and pores included—as compared with an equal bulk of water. The real specific gravity of the peat itself is always greater than that of water, and all kinds of peat will sink in water when they soak long enough, or are otherwise treated so that all air is removed.

[11] The "full" cubic foot implies a cubic foot having no cavities or waste space, such as exist in a pile, made up of numerous blocks. If a number of peat blocks be put into a box and shaken together, the empty space between the more or less irregular blocks, may amount to 46 per cent. of the whole; and when closely packed, the cavities amount to 30 per cent., according to the observations of Wasserzieher. (Dingler's Journal, Oct., 1864, p. 118.) Some confusion exists in the statements of writers in regard to this matter, and want of attention to it, has led to grave errors in estimating the weight of fuel.

[12] The waste space in peat and wood as commonly piled, is probably included here in the statement, and is usually about the same in both; viz.: not far from 40 per cent.

[13] See note on the preceding page.

[14] Der Torf, etc., S. 43.

[15] See page 00.

[16] On account of the great convenience of the decimal weights and measures, and their nearly universal recognition by scientific men, we have adopted them here. The gramme = 15 grains; 5 degrees centigrade = 9 degrees Fahrenheit.

[17] Pliny, Hist. Nat. (Lib. XVI, 1) expresses his pity for the "miserable people" living in East Friesland and vicinity in his day, who "dug out with the hands a moor earth, which, dried more by wind than sun, they used for preparing their food and warming their bodies:" captum manibus lutum ventis magis quam sole siccantis, terra cibos et rigentia septembrione viscera sua urunt.

As regards the "misera gens," it should be said that rich grain fields and numerous flourishing villages have occupied for several centuries large portions of the Duevel moor near Bremen.

[18] For further account and plans of this machine see Dingler's Polytechnisches Journal, Bd. 176, S. 336.

[19] Described and figured in Bulletin de la Societe d'Encouragement, August 1857, p. 513; also Dingler's Polytechnisches Journal, Bd. 146, S. 252.

[20] Berg- und Huettenmaennische Zeitung, 1859, Nr. 26.

[21] Henneberg's Journal fuer Landwirthschaft, 1858, S. 42.

[22] Henneberg's Journal fuer Landwirthschaft, 1858, p.p. 42 and 83.

[23] Dingler's Journal, Oct., 1864.

[24] Dingler's Polytechnisches Journal, Bd. 152, S. 272. See also, Knapp, Lehrbuch der Chemischen Technologie, 3te Auflage, 1., 167.

[25] Der Torf; seine Bildung und Bereitungsweise, von Rudolph Gysser, Weimar, 1864.

[26] Dingler's Journal, Bd. 165, S. 184.; und Bd. 172, S, 333.

[27] Scientific American, Feb. 10, 1866; also, Facts about Peat as Fuel, by T. H. Leavitt, 2d Ed., Boston, p. 23.

[28] Dingler's Journal, Bd. 168, S. 306, und Bd. 172, S. 332.

[29] Described in Journal of the Society of Arts, 1860, p. 437.

[30] Bernemann & Kerl's Berg und Huettenmaennische Zeitung, 1862, 221.



- Transcriber's Note: Typographical errors corrected in text: Page 6 Robert's changed to Roberts' Page 24 Jaeckel changed to Jaeckel Page 47 Poquonnock changed to Poquonock Page 49 connexion changed to connection Page 51 Poquonnock changed to Poquonock Page 53 Poquonnock changed to Poquonock Page 53 Russel changed to Russell Page 62 subtances changed to substances Page 67 Poquonnock changed to Poquonock Page 89 5 changed to 4 Page 89 Poquonnock changed to Poquonock Page 90 Poquonnock changed to Poquonock Page 91 Poquonnock changed to Poquonock Page 116 artifical changed to artificial Page 127 developes changed to develops Page 149 Kneeding changed to Kneading Page 165 The symbol looks like a D lying on its back. -

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