SMOKE-NUISANCE, in London, is punishable with fine. The act applies to every furnace employed in working engines by steam, and every furnace in any factory, printing-house. dye-house, distillery, bake-house, etc., which is not constructed so as to consume its own smoke. or which is so negligently used that the smoke is not consumed. The penalty is from to £5. The statute only applies to the metropolis and to the river Thames.—Lt Scotland a similar act is not confined to the Scotch metropolis.
Large consumers of fuel are naturally more anxious about how it can be best burned economically than about how the escape of smoke into the atmosphere can best be pre vented. The two questions are not at all the same, although plans may he devised which will accomplish both objects at the same time. Thus with ordinary bituminous coal not only may the volatile hydrocarbons which sometimes yield 20 per cent of the heating-power pass up the chimney unburned, but nearly two-thirds of the coal may be wasted by the conversion of the carbon into carbonic oxide instead of carbonic acid— that is if the carbonic oxide escapes as such—and yet no smoke may appear. At the same time it is the fact that the most complete combustion of the coal iusurcs there no smoke.
'nese is a great difference of opinion even about the apparently simple question of how the coal should be laid on the furnace bars. The late prof. Maequorn Rankine and others, reasoning on theoretical grounds, say that the fresh coals should be laid on the front of the fire; -while Dr. Anderson. late of the Woolwich arsenal, judging from great practical experience, says that, on the contrary, they should be mainly piled up at the back of the fire. Mr. Wye Williams, again, whose name is so famous in connection with such questions, asserts that the coal is best spread evenly over the furnace bars.
Whether the fuel is heaped at the front, at the back, or spread uniformly over the fire, the cud in view is the same. It is to secure that the volatile hydrocarbons are burned, and that the carbon is converted into carbonic acid, and this can only he done when these gases are conducted over a hot portion of the the with a sufficient supply of air. If the fresh coal is laid on the front, that of a previous charge Inuring been pushed inward, the coal vapors will of course pass over the thin layer of burning fuel at the back, and be more or less burned. When, on the other hand, the fuel is kept banked up at the back (that is at the bridge), and spread evenly over the rest of the grate, although a little smoke may be given off at first, it would, nevertheless, appear that by this plan the mass of incandescent fuel at the bridge is yet more effectual in burning these vapors. The balance of opinion would, however, seem to be in favor of the
method of rapid, thin, and uniform spreading of the coal over the grate, care being taken that no part of the furnace bars are left bare.
With regard to the adirkission of air to the furnace, it is necessary, in order to obtain the best result, that it be admitted through small orifices, and at such a point or points where the temperature is sufficiently high :ror the combustion of the coal vapors, and that it be so regulated that heat is not uselessly absorbed by an excessive supply. It is of course also necessary to have sufficient air passing up between the furnace bars to burl the non-volatile coke. In the recommended by Mr. Wye Williams the fire is fed, as usual, through a door; it slopes downward to the bridge, which rises much above the fire-bars, so that the flames have to pass over it. The bridge consists of two parts, the solid masonry or brick-work and a chambered portion behind it, called the distributor. Into this a tube opens, through which:a supply of atmospheric air enters, and, becoming heated, passes through a number of plates with slits, or with perforations, into the mixing chamber; here the heated air enters into combustion with the carbon in the smoke-laden flame, deprives it of that clement, and greatly increases the heat by its combustion.
Smoke prevention arrangements may be classified as follows: I. Apparatus for the Tegular addition in small quantities and uniform application of the fuel to the fireplace of the furnace. The chief kinds are: (1) A hopper kept charg,ed_with small coal or slack, and feeding a rapidly rotating horizontal disk. (2) A hopper and rollers to reduce the size of the coals, and a screw spreader for throwing them on. the fire. (3) An under grate stoker, which feeds a circular furnace by causing the fresh coal to pass from below through a central orifice into the middle of the incandescent fuel. (4) A hopper and traveling furnace bars. II. Arrangements for the admission of air above as well as below the furnace bars. This is usually done either by means of air-holes with slide or slides to cover them; or opening and shutting slits in the furnace door or above it. Another plan is to have a valve at the further end of tubular flues in the furnace to regulate the admission of air. In one or two instances a clockwork arrangement has been introduced for gradually closing the air inlets in the furnace doors after firing.