598 GAS-FURNACE 



4000, whilst that carried back by the regenerator is about 3000, making an in- 

 tensity of power which, unless moderated on purpose, would fuse furnace and all ex- 

 posed to its action. 



* Thus the regenerators are alternately heated and cooled by the outgoing and 

 entering gas and air, and the time for alteration is from half an hour to an hour, as 

 observation may indicate. The motive power on the gas is of two kinds : a slight 

 excess of pressure within is kept up from the gas-producer to the bottom of the rege- 

 nerator to prevent air entering and mingling with the fuel before it is burnt; but from 

 the furnace, downward through the regenerators, the advance of the heated medium 

 is governed mainly by the draught in the tall stack or chimney. 



| Great facility is afforded in the management of these furnaces. If, whilst glass 

 is in the course of manufacture, an intense heat is required, an abundant supply of 

 gas and air is given ; when the glass is made, and the condition has to be reduced 

 to working temperature, the quantity of fuel and air is reduced. If the combustion in 

 the furnace is required to be gradual from end to end, the inlets of air and gas are 

 placed more or less apart the one from the other. The gas is lighter than the air ; 

 and if a rapid evolution of heat is required, as in a short puddling furnace, the mouth 

 of the gas-inlet is placed below that of the air-inlet ; if the reverse is required, as in 

 the long tube-welding furnace, the contrary arrangement is used. Sometimes, as in 

 the enameller's furnace, which is a long muffle, it is requisite that the heat be greater 

 at the door-end, because the goods, being put in and taken out at the same end, thoso 

 which enter last, and are withdrawn first, remain, of course, for a shorter time in the 

 heat at the end ; and though the fuel and air enter first at one end and then at the 

 other alternately, still the necessary difference of temperature is preserved by the adjust- 

 ment of the apertures at the ends. 



' Not merely can the supply of gas and air to the furnace be governed by valves in 

 the passages, but the very production of the gas fuel itself can be diminished, or oven 

 stopped, by cutting off the supply of air to the grate of the gas-producer ; and this is 

 important, inasmuch as there is no gasometer to receive and preserve the aeriform 

 fuel, for it proceeds at once to the furnaces. 



1 Some of the furnaces have their contents open to the fuel and combustion, as in 

 the puddling and metal-melting arrangements ; others are enclosed, as in the mufflo 

 furnaces and flint-glass furnaces. 



' The economy in the fuel is estimated practically as one-half, even when the same 

 kind of coal is used either directly for the furnace or for the gas-producer ; but, as in 

 the latter case, the most worthless kind can be employed such as slack, &c., which 

 can be converted into a clean gaseous fuel at a distance from the place of the furnace, 

 so, many advantages seem to present themselves in this part of the arrangement.' 



Professor Faraday concludes his lecture with the following conclusive figures : 



' Carbon burnt perfectly into carbonic acid in a gas-producer would evolve about 

 4000 of heat; but, if burnt into carbonic oxide, it would only evolve 1200. The 

 carbonic oxide, in its fuel form, carries on with it the 2800 in chemical force, which 

 evolves when burning in the real furnace with a sufficient supply of air. The re- 

 maining 1200 are employed in the gas-producer in distilling hycLrocarbons, decom- 

 posing water, &c. The whole mixed gaseous fuel can evolve about 4000 in the 

 furnace, to which the regenerator can return about 3000 more.' 



The following is a brief description of the regenerative gas-furnaces : 



The gas-producer is shown in fig. 1059. The producers are entirely separate from 

 the furnace where the heat is required, and may be made sufficient in number and 

 capacity to supply several furnaces. The fuel is supplied, at intervals of from two to 

 four hours, through the charging boxes A, fig. 1059, and descends gradually on the in- 

 clined plane B, which is set at an inclination to suit the fuel used. The upper portion 

 of the incline B is made solid, being formed of iron plates covered with firebricks ; but 

 the lower portion c is an open grate formed of horizontal flat steps. The large open- 

 ing under the lowest flat step is convenient for drawing out clinkers, which generally 

 collect at that point. The small stoppered holes F at the front, and o at the top of the 

 producer, are provided to allow of putting in an iron bar occasionally to break up the 

 mass of fuel and detach clinkers from the side walls. Each producer is capable of 

 converting daily about two tons of fuel into a combustible gas, which passes off 

 through the uptake H leading to the furnaces. 



The action of the gas-producer in working is as follows : The fuel descending 

 slowly on the solid portion B of the inclined plane becomes heated, and parts with its 

 volatile constituents, the hydrocarbon gases, water, ammonia, and some carbonic acid, 

 which are the same as would bo evolved from it in a gas-retort. There now remains 

 from 60 to 70 per cent, of purely carbonaceous matter to bo disposed of, whicli is 

 accomplished by the current of air slowly entering through the grate c, producing 

 regular combustion immediately upon the grate ; but the carbonic acid (a non-combus- 



