The usual form of ventilating furnace is a plain fire grate placed under an arch, and communicating with the upcast shaft by an inclined drift.
The size of the grate varies with the requirements of the ventilation, but from 6 to io ft.
I and 2), where the fire-grate is placed z i ft.
Scale be removed by falling through a grate, like ordinary coal-ashes.
The Chimney Section Grate Drying space for Slurry Plan FIG.
I meet his servant come to draw water for his master, and our buckets as it were grate together in the same well.
Below the grate, or 4 to 41 in.
If C is the number of pounds of coal burnt per square foot of grate per hour, the calorific value of which is c B.Th.U.
Zinc oxide, ZnO, is maufactured for paint by two processes - directly from the ore mixed with coal by volatilization on a grate, as in the Wetherill oxide process, and by oxidizing the vapour given off by a boiling bath of zinc metal.
The circular grate G can be turned round K by means of the crank E from the outside.
The open grate still holds favour in England, though in America and on the continent of Europe it has been superseded by the closed stove.
This mixture of steam and air enters into the gas-producer e below the fire-grate f.
A few experimental results are set forth in Table XX., from which it will be seen that with a relatively low rate of combustion, a rate which denotes very light service, namely lb of coal per square foot of grate per hour, the efficiency of the boiler is %, which is as good a result as can be obtained with the best class of stationary boiler or marine boiler even when using economizers.
The grate b retains any small pieces of fuel, but allows the liquid cinder to pass through.
At the bottom of the kiln is a grate of iron bars, and on this wood and coke are piled to start the fire.
A large fire-grate (ab), having a cave (c) to facilitate stoking and stepped back at (d), is bounded on one side by a fire-bridge (e); on the other side of this, separated by an air-channel (g), there is first the proper fluxing bed (h), and behind this the "back-bed "(i) for pre-heating the charge.
C. Bischof at Magdesprung (both in Germany), consisted of simple perpendicular shafts of masonry contracted at the top and the bottom, with or without a grate for the coal.
Dr Grierson well describes its movement: "As a work of art, it has for European readers prolixities and episodes which grate against occidental tastes, but no one can read it in the original without being impressed by it as the work of a great genius.
And burning too lb of coal per square foot of grate per hour would Table Xx require that 60,000 ib of air should be drawn through the furnace per hour in order to burn the coal.
_ rying space or urry Kiln Lower shaft containing hot clinker Grate.,› Upper shaft containing raw material FIG.
The effect of this arrangement is that the great body of coal reaches a higher temperature than in an ordinary fireplace, and this, together with the reduction of the carbon dioxide formed immediately above the grate by the red-hot coal in the upper part of the furnace, leads to the formation of carbon monoxide which later on, on the spot where the greatest heat is required, is burned into dioxide by admitting fresh air, preferably pre-heated.
Az¦awea/ clined" step-grate "; D, a;?
Deep. B is the chimney-damper, C the grate, D the door for removing the slags, E the ash-door, F the inlet of the air-blast, G the upper, G 1 the lower outlet for the water-gas which is removed alternately at top and bottom by means of an outside valve, steam being always admitted at the opposite end.
These are almost invariably air furnaces, though sometimes air under pressure is used, as, for example, in the combustion of small anthracitic coal, where a current of air from a fan-blower is sometimes blown under the grate to promote combustion.
Ft., that the rate of combustion is 150 lb of coal per square foot of grate per hour, that the calorific value is 14000, and finally that n =0.06, the maximum indicated horse-power which the engine might be expected to develop would be o 06 X 150 x14000 X24 X 778/1980000 = I 190, corresponding to a mean effective pressure in the cylinders of 59.5 lb per square inch.
Graphite is used for the manufacture of pencils, dry lubricants, grate polish, paints, crucibles and for foundry facings.
Sometimes the purpose of a gas-producer is attained in a very simple manner by lowering the grate of an ordinary fireplace so much that a layer of coal 4 or 5 ft.
Per pound, the maximum indicated horse-power is given by the expression I.H.P. maximum - CcA X778 1980000 where A is the area of the grate in square feet, and is the combined efficiency of the engine and boiler.
The maximum rate of combustion may be as much as so lb of coal per square foot of grate per hour, and in exceptional cases even a greater rate than this has been maintained.
Where the" natural draught "is not sufficient, it is aided either by blowing air under the grate or else by suction at the other end.
This is generally done by making the bed of the furnace very long in proportion to its breadth and to the fire-grate area, which may be the more easily done as a not inconsiderable amount of heat is given out during the oxidation of the ore - such increased length being often obtained by placing two or even three working beds one above the other, and allowing the flame to pass over them in_order from below upwards.
It has many advantages for heavy high-speed service, namely, large and well-proportioned boiler, practically unlimited grate area, fire-box of favourable proportions for firing, fairly low centre of gravity, short coupling-rods, and, finally, a combination of the safe and smooth riding qualities of the fourcoupled bogie type, with great steaming capacity and moderate axle loads.