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combustion. The following is an analysis these 60 lbs. of pure carbon, 220 lbs. of from Dr. Percy's work on “Fuel" of a carbonic anhydride (CO,) are produced, coal from the Newcastle district:
and in this combination 60X14,500= Carbon.
870,000 heat units (according to accurate Hydrogen.
5.83 determinations by Favre and Silbermann, Oxygen.
7.90 Dulong and Andrews) are produced. Nitrogen.
The 34 per cent. of volatile matter Sulphur
driven off yield, when the condensible 2.07
vapors of water, ammonia and tar, are which shows at a glance that nearly 16 separated, about 16 of pure combustible per cent of the total weight consists of gas (being equal to about 10,000 cubic such permanent gases as hydrogen, feet per ton of coal) which in combustion oxygen and nitrogen. Those gases are produce 16 x 22,000=352,000 heat units. partly occluded or absorbed within the The escape of these gases from the coke coal, but are also combined with carbon
oven constitutes a
serious loss, which forming volatile compounds, such as the may be saved, to a great extent at least, hydrocarbons and ammonia, so that when if the decarburization is effected in recoal is subjected to heat in a closed re- torts. The total heat producible from tort, as much as 35 per cent. passes away each 100 lbs. of coal is in that case from the retort in a gaseous condition 870,000+ 352,000=1,222,000 or 12,220 and as vapor of water, partly to con- units per lb. of coal. Deduction must, dense again in the form of tar, and of however, be made from this for the heat ammoniacal liquor, and partly to pass required to volatilize 34 lbs. of volatile into the gas mains as illuminating gas, matter for every 100 lbs. of coal used, a mixture merely of marsh gas (CH), and also for heating the coke to redness, olefiant gas (CH), and acetylene (CH), or say to 1,000° Fah. Considering the its value as an illuminant depending multiplicity of gases and vapors proupon the percentange of the last two duced it would be tedious to give the constituents rich in carbon. The result details of this calculation, the result of of the distillation of a ton of coal will be which would approximate to 60,000 heat as follows, from data with which Mr. A. units, or 600 units per lb. of coal treated. Upward has kindly supplied me:
We thus arrive at 12, 200—600=11,600
Cwt. heat units as the maximum result to be Cake....
obtained from 1 lb. of best coal. ConTar...
1.20 Ammoniacal liquor
sidering, however, that the coal
monly used for industrial purposes conCarbonic acid..
0.18 tains more ashes and more water than Sulphur removed by purifying. 0.30 has been here assumed, a reduction of Loss
say 10 per cent. is necessary, and the So great is the loss of heat sustained calorific power of ordinary coal may in an ordinary coal fire, in consequence of fairly be taken at 10,500 units per lb. the internal work of volatilization, that
In applying this standard of efficiency such a fire is scarcely applicable for the to actual practice it will be found that production of intense degrees of heat, the margin for improvement is large inand it has been found necessary to de- deed. Thus, in our best steam-engine prive the coal in the first place of its practice we obtain one actual horsevolatile constituents (to convert it into power with an expenditure of 2 lbs. of coke) in order to make it suitable for the coal per hour (the best results on record blast furnace, for steel melting, and for being 1.5 lbs. of coal per indicated horse. many other purposes where a clear in. power.) A horse-power represents 33.000 tense heat is required.
X 60=1,980,000 foot-lbs. per hour, which In the ordinary coke oven the whole 1,980,000
=980,000 foot-lbs., or units of the volatile constituents are lost, and 2 each 100 lbs. of coal yield only 66 lbs. of of force, per lb. of fuel. Dr. Joule coke, including the whole of the earthy has shown us that 772 foot-lbs. repreconstituents which on a large average sent one unit of heat, and 1 lb. of coal may be taken at 6 lbs., leaving a balance
980,000 60 lbs. of solid carbon. In burning therefore produces =1,282 units
of heat, instead of 10,500, or only one- of radiant heat, why, it may be asked, do eighth part of the utmost possible re- we not resort at once to coke for our dosult.
mestic fuel ? The reasons are twofold ; In melting steel in pots in the old- the coke would be most difficult to light, fashioned way, as still practiced largely and when lighted would look cheerless at Sheffield, 24 tons of best Durham coke without the lively flickering flame. are consumed per ton of cast steel pro The true solution consists, I venture duced. The latent and sensible heat to submit, in the combination of solid really absorbed in a pound of steel in and gaseous fuel when brought thorthe operation, does not exceed 1,800 oughly under control, by first separating units, whereas 24 lbs. of coke are capa- these two constituents of coal. I am ble of producing 13,050 x 2.5=32,625 bold enough to go so far as to say that units or 18 times the amount actually raw coal should not be used as fuel for utilized.
any purpose whatsoever, and that the In domestic economy the waste of fuel first step toward the judicious and ecois also exceedingly great, but it is not nomic production of heat is the gas reeasy to give precise figures representing tort or gas producer, in which coal is the loss of effect, owing to the manifold converted either entirely into gas, or into purposes to be accomplished, including gas and coke, as is the case at our ordicooking and the heating and ventilation nary gas works. of apartments. If ventilation could be When in the early part of the present neglected close stoves, such as are used winter London was visited by one of its in Russia, would unquestionably furnish densest fogs, many minds were directed the most economical mode of heating our towards finding a remedy for such a apartments ; but health and comfort are, state of things. In my own case it has after all, of greater importance than resulted in an arrangement which has economy, and these are best secured by met with a considerable amount of favor means of an open chimney. Not only and practical success, and I do not hesidoes the open chimney give rise to an tate to recommend it to you also for active circulation of air through the adoption. Its general application would, room, which is a necessity for our well- as regards dwelling houses, make our being, but heat is supplied to the room town atmosphere as clear as that of the by radiation from the incandescent ma- i surrounding country. If it can be shown terial instead of by conduction from that the arrangement may be easily and stove surfaces; in the one case the walls cheaply applied, that it will relieve our and furniture of the room absorb the housemaids of the most irksome portion luminous heat rays, and yield them back of their daily work in laying fires and to the transparent air, whereas, in the cleaning grates, and that a warm and latter case, the air is the first recipient cheerful fire can be made at a consideraof the stove heat, and the walls of the bly cheaper rate than when using coal, room remain comparatively cold and you will admit, I hope, that the proposal damp, giving rise to an unpleasant musty is worthy of a trial. atmosphere, and to dry rot or other In outward appearance my fire-gratemouldy growth. The adversaries of the which I have not made the subject of a open fireplace say that it warms you on patent, and which may, therefore, be put only one side, but this one-sided radiant up by any grate or gas fitter without heat produces upon the denizens of this restraint-is very similar to the ordinary somewhat humid country, and indeed coal grate ; the latter may, indeed, be upon all unprejudiced people, a particu- converted into the smokeless grate at a larly agreeable sensation ; which is proof, very trifling cost. The essential features I think, of its healthful influence. The of this grate are, that solid carbonaceous hot radiant fire imitates, indeed, the sun fuel, such as coke or anthracite, are used in its effect upon man and matter, and in combination with as much gas as is before discarding it on the score of found necessary to raise the former to wastefulness and smokiness, we should the point of incandescence; that the try hard, I think, to cure it of its admit- combustion is entirely confined to the ted imperfections.
front of the grate, whence radiation into If incandescent coke is the main source the room takes place; and that any heat
reaching the back of the grate is con- grate has been altered to the gas-coke ducted away and utilized in heating the grate just described. incoming air, by which combustion in In order to test the question of econfront of grate is supported. In this way omy, I have passed the gas consumed in greater brilliancy and considerable econ- the grate through a Parkinson's 10-light omy are realized.
dry gas meter supplied to me by the In one arrangement by which this is Woolwich, Plumstead and Charlton Coneffected an iron dead plate is riveted to sumers' Gas Company. The coke used a stout copper plate facing the back of is also carefully weighed. the fire grate, and extending 5 inches The result of one day's campaign of both upwards and downwards from the nine hours is a consumption of 62 cubic point of junction. The dead plate stops feet of gas and 22 lbs. of coke (the coke short about an inch behind the bottom remaining in the grate being in each case bar of the grate to make room for a half- put to the debit of the following day). inch gas pipe, which is perforated with Taking the gas at the average London holes of about one-sixteenth of an inch price of 38. 6d. per 1,000 cubic feet, and placed at a distance of 14 inches along the coke at 18s. a ton, the account stands the inner side of its upper surface. This thus for nine hours : pipe rests upon a lower plate, which is 62 cubic feet of gas at 38. 6d. per thousbent downwards towards the back, so as
2.604 d. to provide a vertical and horizontal chan. 22 lbs. of coke at 188. a ton.
2.121 nel of about 1 inch in breadth between
1.725 the two plates. A trap door, held up by a spring, is provided for the discharge or at the rate of 0.525d. per hour. In of ashes falling into this channel. The its former condition at a coal grate the vertical portion of this channel is occu- consumption exceeded generally two and pied by a strip of sheet copper about 4 a-half large scuttles a day, weighing 19 inches deep, bent in and out like a lady's lbs. each, or 47 lbs. of coal, which at 238. frill, and riveted to the copper back a ton equals 5.7d. for nine hours, being piece.
0,633d. per hour. This result shows that Copper being an excellent conductor the coke-gas fire, as here described, is of heat, and this piece presenting not only a warmer but a cheaper fire than (if not less than a quarter of an inch its predecessor ; with the advantages in thick) a considerable sectional conductive its lit without the trounle of laying the area, transfers the heat from the back of fire, as it is called, and keep alight withthe grate to the frill work in the vertical out requiring to be stirred, that it is channel. An air current is set up by thoroughly smokeless, and that the gas this heat, which, in passing along the can be put off or on at any moment, horizontal channel, impinges on the line which in most cases means considerable of gas flames, and greatly increases their enonomy. brilliancy. So great is the heat imparted A second and more economical arto the air by this simple arrangement, rangement as regards first cost consists that a piece of lead of about half a pound of two parts which are simply added to in weight introduced through the trap the existing grate, viz. : (1) the gas pipe door into this channel melted in five with a single row of hole of about 1-16 minutes—proving a temperature exceed- inch diameter, 1.5 inch apart along the ing 619° Fah., or 326° C. The abstrac- upper side inclining inward, and (2) an tion of heat from the back has, moreover, angular plate of cast iron, with projectthe advantage of retarding the combus- ing ribs extending from front to back on tion of the coke there while promoting its under side, presenting a considerable it at the front of the grate.
surface, and serving the purpose of proI have used this arrangement in a fire- viding the heating surface produced by place at my office, in a room of 7,200 the copper plate and frill work in my cubic feet capacity facing the north. I first arrangement. In using iron instead always found it difficult, during cold of copper it is necessary, however, to inweather, to keep this room at 06° Fah. crease the thickness of these plates and with a coal fire; but it has been easily ribs in the inverse ratio of the conducmaintained at that temperature since the tivity of the two metals, or as regards
the back plate, from 1 inch to inch. Granted the cure of smoke, it might An inclined plate, fastened to the lower still be questioned whether such a plan as grate bar, directs the incoming air upon here proposed could be carried out, on the heating surfaces, and provides at the so large a scale as to affect our: atmossame time a support for the angular and phere, with the existing mains and other ribbed plate which is simply dropped into plant of the gasworks. If gas were to its firm position between it and the back be depended upon entirely for the proof the grate. The front edge of the hori. duction of the necessary heat, as is the zontal plate has vandyked openings, case with an ordinary gas and asbestos forming a narrow grating, through which grate, it could easily be proved that the the small quantity of ashes, that will be existing gas mains would not go far to produced by combustion of the coke or supply the demand; each grate would anthracite in the front part of the grate, consume from 50 to 100 cubic feet an discharge themselves down the incline hour, representing in each house a contowards the back of the hearth, where sumption exceeding many times the supan open ash pan may be placed for their ply to the gaslights. My experiments reception. In adapting the arrangement prove, however, that an average conto existing grates, the ordinary grating sumption of from 6 to 8 cubic feet of gas may be retained to support the angular per hour suffices to work a coke gas plate which has in that case its lower grate, on the plan here proposed. This ribs cut short, to the level of the hori- is about the consumption of a large Arzontal grate.
gand burner, and therefore within the A considerable number of grates have limits of ordinary supply. But, indenow been constructed or altered in ac- pendently of the practical question of cordance with my plan, and have given | supply, it is desirable on the score of great satisfaction to the users, on account economy to rely upon the solid carbon of convenience and economy, which are chiefly for the production of radiant heat, conditions essentially necessary, if we for the following reason : are to make any way toward the more 1,000 cubic feet of ordinary illuminatimportant, I may say national, result of ing gas weigh 34 lbs., and the heat dea “smokeless London,” a smokeless Man- veloped in their combustion amounts to chester, and a smokeless Glasgow. But 34 x 22,000=748,000 heat units. it
may be asked, are you sure that the One pound of solid coke develops in coke and gas grate you advocate, will do combustion, say, 13,400 heat units (asaway with fogs and smoke? My answer suming 8 per cent. of incombustible adis, that it would certainly do away with
= 56 lbs., smoke, because the products of combus- mixture) and it requires
13,400 tion passing away into the chimney are or just half a hundred weight, of this perfectly transparent. Mr. Aitken has, coke to produce the same heating effect however, lately proved in an interesting as 1,000 cubic feet of gas. But 1,000 paper read before the Royal Society of cubic feet of gas cost on an average 38. Edinburgh, that even with perfect com- 6d., and a half hundred weight of coke bustion à microscopic dust is sent up not more than 6d. (at 20s. a ton), or into the atmosphere, each particle of only one-seventh part of the price of which may form a molecule of fog. We
gas. have evidence, indeed, that the whole
If heating gas was supplied at a much universe is filled with dust, and this is, ' cheaper rate it would, in many cases, be according to Professor Tyndall, a fortu- advantageous to substitute incombustinate circumstance, for without dust we ble matter, such as balls of asbestos for should not have a blue but a pitch black the coke or anthracite. The consumpsky, and on our earth we should be, ac- tion of gas would in that case have to be cording to Mr. Aitken, without rain, and increased very considerably, but the should have to live in a perpetual vapor economical principle involved (that of bath. The gas fires would contribute, it heating the air of combustion by conappears, to this invisible dust, and we duction from the back of the grate) should, no doubt, continue to have fogs, would still apply, and produce economibut these would be white fogs, which cal results as compared with those obwould not choke and blacken us.
tained by the gas-asbestos arrangements
hitherto used. To illustrate the efficiency larger proportion of the heat developed of this mode of heating the incoming air in combustion to reach the point of by what is called waste heat, I will show luminous radiation. But not only the you another application of the same quantity of light, but its quality, is imprinciple which I have made very re- proved by the higher temperature obcently to the combustion of gas for illum- tained. It may appear surprising, but inating purposes.
it is a fact susceptible of accurate proof, Gas engineers have been under the that the light obtained in consumption impression until now that a supply of of a given amount of gas may thus be cold air was favorable to the production increased by some 40 per cent., and that of a brilliant flame. This is a miscon- in this large proportion the deleterious ception which was very general also as influences connected with gas lighting regards the combustion of solid fuel in ' may be diminished. Gas will thus be furnaces, until it was disproved by Stir-' better able to hold its position against ling, by Neilson, and by the introduction its more brilliant rival the electric light, of the regenerative gas furnace. The except for such large applications as the
duplex burner” owes its brilliancy to lighting of public halls and places, of the heating effect of the one burner upon harbor, railway stations, warehouses, &c., the other ; and my brother, Mr. Freder- for which it is pre-eminently suited. ick Siemens, has more recently con- Add to these improved applications of structed a burner in which the flame of gas the ever-increasing ones for heating the gas is reversed in its action in order purposes, and I have only to express reto heat in its descent the ascending cur- gret that I am not a gas shareholder. If rent of flame-supporting air. By the gas is to be largely employed, however, application of the principle of conduc- for heating purposes, it will have to come tion before described, I obtain the hot down in price; and considering that air current in the most simple manner heating gas need not be bighly purified, without interfering with the free action or possessed of high illuminating power, of the flame. In my arrangement an the time will come, I believe, when we ordinary Argand burner takes its supply shall have two services, one for illuminof gas through an enlarged vertical cop- ating and the other for heating gas. per tube. This copper pipe terminates · In many towns two systems of gas in a rod of highly conductive copper, mains already exist; and it would only which passes upward through the burner, be necessary to appropriate the one for and carries at its top a ball of porcelain illuminating and the other for heating or other refractory material. The rod is gas. The ordinary retorts could be used coated with platinum or nickel to pre- for the production of both descriptions vent oxidation when heated (almost to of gas, it being well known that even redness) by the heat of the flame. The ordinary coal will give up gases of high tube is armed with radial plates of cop- illuminating power during a certain porper presenting a considerable aggregate tion of the time occupied in their entire surface, and abutting externally against distillation. The gases emitted from the a covering of asbestos or other non-con- retort when first charged are to a great ductive material.
| extent occluded gases of low illuminating The waste heat of the flame, or that power such as fire damp or marsh gas, portion of the heat produced in combus- and these should be turned into the tion which is not utilized in luminous heating mains. In the course of half an rays, serves to heat the ball of refractory hour these occluded gases, together with material and the conductive rod. The the aqueous and other vapors will have heat is thus transferred by conduction to left the coal, which is then in the best the upright copper tube, with its laminar condition to evolve olefiant gas and other radii, between the extensive surfaces of gases rich in carbon, and therefore of which currents of air are free to ascend higher illuminating power. The period towards the Argand burner. The air is, during which such illuminating gases are thus heated to from 7000 to 800° Fah. emitted extends over probably two hours, before meeting the gas, and the ultimate after which the retorts should again be temperature of the fame is increased to connected with the heating gas mains, at least the same amount, causing a until the end of the process. The result