SUGAR-CANE SIRUP MANUFACTURE 53 
The plate and frame filter press is in general the most satisfactory 
type for mud filtration. ‘It is simple to operate and less expensive 
than some of the more complicated types. 
EVAPORATORS 
Kvaporators used in the larger sirup factories are practically always 
of the open type. Most of them are made entirely of copper, but 
some have iron bodies and copper coils (p. 22). In the very small 
plants galvanized-iron pipe is often used for the coils. Regardless of 
their cost, copper evaporators and copper coils are recommended. 
Open evaporators of the Louisiana type generally contain 50 to 100 
square feet of heating surface, with a maximum of 200 square feet. 
The fact that these evaporators are constructed in very small units 
of heating surface makes it necessary to employ a number of units. 
This is not objectionable, however, as it makes possible greater flexi- 
bility in the operation of the plant. 
EVAPORATOR SUPPLY TANK 
The clear juice from the defecators and filter presses is piped to an 
evaporator supply tank large enough to hold the juice that collects 
during the intervals between the intermittent demands for juice by 
the evaporators. Trash may be kept out by covering all but a small 
portion of the top of this tank with a metal or wooden cover and 
placing a fine-mesh screen over the part not covered. . The juice 
enters through this screen, which catches any trash that might fail 
into the juice while it is passing from the defecators and filters to the 
evaporator supply tank. A connection in the bottom, which drains 
either to a sewer or back into the raw-juice tank, makes it possible 
to wash the tank. The evaporator supply tank is placed low enough 
to permit all juice to fow into it by gravity but high enough to per- 
mit juice also to flow to the evaporators by gravity. 
SIRUP-SEDIMENTING TANKS FOR DILUTE SIRUP 
The dilute sirup resulting from the initial stages of boiling in the 
evaporators is sedimented in tanks arranged in the same manner as 
defecators, but with no steam coils. They should be large enough 
to readily hold the sirup drawn off from one evaporator at the end of 
the first boiling stage. The bottom of each sedimenting tank should 
have a connection leading to the sewer and to the raw-juice tank so 
_ that it may be washed out. Dirt and trash are kept out by a re- 
movable fine-mesh screen. 
PUMP TANK FOR DILUTE SIRUP 
The sirup-sedimenting tanks are arranged to discharge by decanta- 
tion into a trough leading down to the pump tank for dilute sirup. 
This tank collects the sirup after sedimentation, so that it may be 
pumped back to the evaporators for final concentration. It should 
be placed low enough to permit the sirup to flow into it by gravity 
from the sedimenting tanks. A connection at the bottom makes it 
possible to wash it out into the sewer or into the raw-juice tank. 
