plates alternating with hollow frames, a pressure is put on the plates and frames 

 holding them in place. They are so arranged that the mud can be forced 

 into the hollow frames allowing the juice to filter through the canvas to the 

 corrugated plates where it is caught and drained to a receiving trough below. 

 In passing through the presses under heavy pressure the sediment, scum and 

 other impurities are caught on the canvas cloths. A certain amount of hot 

 water is forced through the presses which takes with it a portion of the sugar 

 remaining in the scum and mud. When the press is completely filled and the 

 sugar recovered, the mud is then released from the press by opening the frames 

 and removing the cloths. This mud is valuable as fertilizer and is conveyed 

 to the fields. The clear juice from the settling tanks, the cachaza tanks and 

 filter presses is collected in the evaporator supply tank ready to be reduced 

 to a syrup. 



Evaporation 



Water boils under atmospheric pressure at sea level at a 

 Effects temperature of 212 F., and sugar juice a few degrees higher, 



according to the density. If this temperature is applied to 

 the cane juice for a great length of time, it will have a tendency to burn 

 and destroy the sugar, but higher temperatures can be applied to the cane 

 juice for a short time without deterioration. The usual clarified cane juice 

 contains in the neighborhood of 85% water and 15% of solid matter. About 

 75% of the water is removed in an apparatus known as an evaporator. 

 The evaporator usually consists of four cells called a quadruple effect 

 evaporator, or it may have five or in some cases six cells, known as 

 quintuple or sextuple effects. 



The usual type of construction is a vertical cell with the lower section 

 forming a calandria with copper tubes inserted vertically into tube sheets, 

 the juice passing through the tubes and the steam or vapors being held between 

 the outer shell and the tube sheets. The juice enters the first cell and partially 

 covers the heating tubes. Steam at about five pounds pressure is admitted 

 to the calandria, causing the juice to boil and circulate through the tubes. The 

 vapor liberated from the first boiling is conductedthrough vapor pipes directly 

 into the heating calandria of the second cell and the juice from the first cell 

 passes into the juice side of the second cell and from the second to the third 

 and the third to the fourth. Vapors from the last cell are conducted directly 

 to a condenser. As there is little pressure above the liquid in the first cell, 

 it boils at about 215 to 220 F. A vacuum of approximately 5 inches is 

 maintained in the second cell and the temperature at which the liquid will 

 boil is reduced to about 203, so that the vapor from the first cell is hot enough 

 to boil the juice in the second cell. As the vapor from the second cell passes 



42 



