Peat and its Uses as Fertilizer and Fuel Part 16

At Pillersee, in Austria, spathic iron ore has been reduced by a mixture of fir-wood charcoal, and air-dry peat in the proportions of three parts by bulk of the former to one of the latter. The use of peat was found to effect a considerable saving in the outlay for fuel, and enabled the production to be somewhat increased, while the excellence of the iron was in no way impaired. The peat was of the best quality, and was worked and moulded by hand.

When the ore is refractory and contains impurities that must be fluxed and worked off in slag, a large proportion of air-dry peat cannot be used to advantage, because the evaporation of the water in it consumes so much heat, that the requisite temperature is not easily attained.

At Achthal, in Bavaria, air-dry peat was employed in 1860, to replace a portion of the fir wood charcoal, which had been used for smelting an impure clay-iron-stone: the latter fuel having become so dear, that peat was resorted to as a make s.h.i.+ft. Instead of one "sack," or 33 cubic feet of charcoal, 24 cubic feet of charcoal and 15 cubic feet of peat were employed in each charge, and the quant.i.ty of ore had to be diminished thereby, so that the yield of pig was reduced, on the average, by about 17 _per cent._ In this case the quality of the iron, when worked into bar, was injured by the use of peat, obviously from an increase of its content of phosphorus. The exclusive use of air-dry peat as fuel in the high furnace, appears to be out of the question.

At Ransko, in Bohemia, _kiln-dried peat_, nearly altogether free from water, has been employed in a high furnace, mixed with but one-third its bulk of charcoal, and in cupola furnaces for re-melting pig, full-dried peat has been used alone, answering the purpose perfectly.

The most important metallurgical application of peat is in the refining of iron.

Dried peat is extensively used in puddling furnaces, especially in the so-called gas puddling furnaces, in Carinthia, Steyermark, Silesia, Bavaria, Wirtemberg, Sweden, and other parts of Europe. In Steyermark, peat has been thus employed for 25 years.

Air-dry peat is, indeed, also employed, but is not so well adapted for puddling, as its water burns away a notable quant.i.ty of iron. It is one of the best known facts in chemistry, that ignited iron is rapidly oxidized in a stream of water-vapor, free hydrogen being at the same time evolved.

In the high furnace, _peat-coal_, when compact and firm (not crumbly) may replace charcoal perfectly, but its cost is usually too great.

When peat or peat-coal is employed in smelting, it must be as free as possible from ash, because the ash usually consists largely of silica, and this must be worked off by flux. If the ash be carbonate of lime, it will, in most cases, serve itself usefully as flux. In hearth puddling, it is important not only that the peat or peat-coal contain little ash, but especially that the ash be as free as possible from sulphates and phosphates, which act so deleteriously on the metal. The notion that, in general, peat and peat charcoal are peculiarly adapted for the iron manufacture, because they are free from sulphur and phosphorus, is extremely erroneous. Not infrequently they contain these bodies in such quant.i.ty, as to forbid their use in smelting.

In the gas-puddling furnace, or in the ordinary reverberatory, impure peat may, however, be employed, since the ashes do not come in contact with the metal. The only disadvantage in the use of peat in these furnaces is, that the grates require cleaning more frequently, which interrupts the fire, and, according to Tunner, increases the consumption of fuel 8 to 10 _per cent._, and diminishes the amount of metal that can be turned out in a given time by the same quant.i.ty.

Notwithstanding the interruption of work, it has been found, at Rothburga, in Austria, that by subst.i.tution of machine-made and kiln-dried peat for wood in the gas-puddling furnace, a saving of 50 _per cent._ in the cost of bar iron was effected, in 1860. What is to the point, in estimating the economy of peat, is the fact that while 6.2 cubic feet of dry fir-wood were required to produce 100 lbs. of crude bar, this quant.i.ty of iron could be puddled with 4.3 cubic feet of peat.

In the gas furnace, a second blast of air is thrown into the flame, effecting its complete combustion; Dellvik a.s.serts, that at Lesjoeforss, in Sweden, 100 lbs. of kiln-dried peat are equal to 197 lbs. of kiln-dried wood in heavy forging. In an ordinary fire, the peat would be less effective from the escape of unburned carbon in the smoke.

In other metallurgical and manufacturing operations where flame is required, as well as in those which are not inconvenienced by the ingredients of its ash, it is obvious that peat can be employed when circ.u.mstances conspire to render its use economical.

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 quant.i.ty 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 quant.i.ty 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 quant.i.ty 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 quant.i.ties 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, 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 quant.i.ty 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 quant.i.ty of _coal_ or _c.o.ke_ yielded by peat, is determined by heating a weighed quant.i.ty 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 c.o.ke, 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 F., weighs 252-1/2 grains.

FOOTNOTES:

[10] The apparent specific gravity here means the weight of the ma.s.s,--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 s.p.a.ce, 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 s.p.a.ce 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 _Wa.s.serzieher_.

(_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 s.p.a.ce_ 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 flouris.h.i.+ng 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.