58 



delivered into each stoker is regulated. The entire process of taking 

 bagasse from the mill to the furnace room and firing the ovens is auto- 

 matic and a large power plant requires only one or two attendants for 

 regulating the water in the boilers, the fuel in the furnace, and watching 

 the steam pressure. 



Boilers. — ^Any type of boiler may be used but sugar mill engineers 

 generally prefer the multi-tubular boiler in sizes furnishing about 20C 

 horsepower. Considerable economy results in the fuel if the boilers are 

 set tandem and the combustion furnace removed three or four meters 

 from the first boiler. 



Furnaces. — The furnace best adapted for burning bagasse is known as 

 a Dutch oven type and fitted with a stepladder grate and automatic 

 stoker. They are generally built of brick, stone, or concrete, and must 

 be lined with fire brick, in order to stand the intense heat. 



Mill engines. — The most common type of engine used for driving 

 sugar mills is known as the slow-speed, high-duty engine of the Corliss 

 type. They are made in sizes up to 750 horsepower and are connected 

 with the sugar mill through the reducing gear arranged on a separate 

 bed between the engine and the mill. It is always desirable to have 

 plenty of power in a sugar mill as there is always a tendency to add to 

 the work of the engine. 



Juice pumps. — A sugar factory requires a great many pumps for a 

 variety of purposes, especially the transferring of juice from one place 

 to another as desired. For elevating it short distances centrifugal pumps 

 similar to those used for irrigation purposes are commonly used but in 

 smaller sizes. For pumping to high elevations where there is a heavy 

 pressure the horizontal steam pump gives much more satisfactory results. 

 These are made in a variety of sizes and combinations and are generally 

 interchangeable for handling water and syrup. 



Clarification. — Cane juice flows from the mill filled with a great many 

 impurities. The trash is generally caught by the strainer but the juice 

 flows into the receiving tank at the mill. It is then pumped to the 

 liming tank usually located on the first or second floor of the mill building. 

 After the tank is filled it is tested by the chemist who prescribes the 

 amount of lime required for neutralizing the acidity in the juice. It 

 should be stirred in the liming tank by forcing air or steam through it 

 so as to insure a complete mixing of the lime with the juice. 



Juice heaters. — ^A^lile all modern mills use juice heaters, they are not 

 essential. They are, however, very desirable and are but little more 

 expensive than open tanks or clarifiers, fitted with steam pipes. The 

 simplest form of juice heater consists of a boiler-like shell with heads 

 and is fitted with drawn copper tubes in the same manner as a multi- 

 tubular boiler. It has an inclosed space at both ends for admitting and 

 discharging the juice and is fitted with steam pipes generally connecting 



