ECONOMICAL USE OF FUEL IX CREAMERIES. 23 



one side of the furnace while the other side is partly burned the 

 fresh coal upon being heated discharges large quantities of volatile 

 gases which require a great deal of air for combustion. The air 

 needed for burning the volatile gases is supplied to a great extent 

 by the excess air which conies through the fuel bed on the opposite 

 side of the furnace. As soon as the combustible gases from the 

 charge of fresh coal have been distilled off and burned the opposite 

 side of the grate is fired, with the same result. Instead of firing the 

 sides of the furnace alternately some prefer to alternate in charging 

 the front and back of the furnace. The principle, however, is the 

 same in each case, and it is simply a matter of personal preference. 

 When firing in this manner comparatively small quantities of coal 

 are used at frequent intervals. 



The coking method of firing soft coal has for its object the lessen- 

 ing of the smoke nuisance as well as the economical burning of a 

 highly volatile coal. The method consists in shoveling just inside 

 the furnace door a moderate quantity of coal, which is gradually 

 heated, thus distilling off slowly the volatile gases which pass over 

 the fuel bed in the rear and are burned by mixing with the excess 

 air coming through the fuel bed. After the coking process has been 

 completed the mass is broken up and pushed back over the fuel bed, 

 taking care that all holes and thin spots are covered, and a fresh 

 supply of coal added as before. Coke is the solid substance which 

 remains after all the volatile gases have been driven off from coal 

 through the application of heat. When pure it consists almost en- 

 tirely of carbon and burns without smoke and with very little flame. 

 The frequency of firing by the coking method depends upon the 

 draft and rate at which steam is used, but under ordinary conditions 

 it should be from 10 to 15 minutes. It is believed that this method 

 of firing is the best for creameries, where the fireman has duties to 

 perform in addition to firing the boiler, as the time between firings 

 is somewhat longer than in either the spreading or alternate methods. 

 The fireman should determine for himself how much coal should be 

 fired at a time and the length of time between firings. This can be 

 easity determined by noting the condition of the fuel bed as to holes, 

 the thickness and color of the fuel bed, the quantity of coke required, 

 and the degree of coking for different lengths of time. 



AIR LEAKS. 



In order to burn fuel economically, all air leaks into .the boiler set- 

 ting must be found and stopped. One way to find the points at which 

 air leaks into a boiler setting is to have the boiler under steam and 

 the fire burning rapidly. When the fuel bed is a glowing heap of 

 coals cover the fire with a layer of fuel and close the dampers 

 tight. The fresh fuel will liberate large quantities of gases which 



