600 



GAS-FURNACE 



in fig. 1059, can be inserted in the uptake so as to shut off any gas-producer at 

 pleasure. 



It is important that the main gas-flue leading to the furnaces should contain an ex- 

 cess of pressure, however, slight, above the atmosphere, in order to prevent any inward 

 draught of air through crevices, which would produce a partial combustion of the gas, 

 and diminish its heating power in the furnace, besides causing a deposit of soot in the 

 flues. It is therefore necessary to deliver the gas into the furnace without depending 

 upon the chimney-draught for that purpose. This can be easily accomplished when 

 the gas-producers are placed at a lower level than the furnaces ; but as that is not 

 always practicable, the following plan has been adopted. The mixture of gases on 

 leaving the producers has a temperature ranging between 300 and 400 F., which 

 must under all circumstances be sacrificed, since it makes no difference to the result at 

 what temperature the gas to be heated enters the regenerators, the final temperature 

 being in all cases very nearly that of the heated chamber of the furnace, or say 

 2500 F. The initial heat of the gas is therefore made available for producing a 

 plenum of pressure by making the gas rise about 20 feet above the producers, then 

 carrying it horizontally through a wrought-iron tube J, and letting it again descend to 

 the furnace. The horizontal tube J, being exposed to the atmosphere, causes the gas 

 to lose from 100 F. to 150 F. of temperature, which increases its density from 15 to 

 20 per cent., and gives a preponderating weight to that extent to the descending column, 

 urging it forward to the furnace. 



The regenerative gas-furnace consists of the heating chamber, below which are placed 

 four regenerative chambers, which are filled with firebricks built up with spaces be- 

 tween them. The regenerative chambers work in pairs ; the two under the loft-hand 

 end of the furnace communicating with that end of the heating chamber, while the 



other two communicate with the opposite end. The gas enters the heating chamber 

 through one passage, and the air through the other passage whereby they arc kept 

 separate up to the moment of entering the heating chamber, but are then able im- 

 mediately to mingle intimately, producing at onco an intense and uniform flame. 



