THE DEFECATION OF CANE JUICE 273 



Juice Heating. The usual type of juice heater consists of a cylindrical 

 shell, in which are arranged tube plates at either end, the tubes passing 

 from plate to plate. The juice circulates within the tubes, and the steam 

 between the plates and without the tubes. By an arrangement of division 

 plates the juice is constrained to travel in alternate directions through nests 

 of tubes. The tubes vary in length from ten to thirty feet, the changes 

 of direction being from three to forty in different designs. In the largest 

 sizes in use the total length of travel of the juice may reach as much as 250 

 feet. In different designs the velocity of the juices will be found to vary 

 from 100 to 400 feet per minute. Latest practice seems to incline towards 

 the adoption of a higher velocity, following on the generally accepted theory 

 that the transmission of heat increases with the square root of the velocity. 

 On the other hand, the higher velocity demands increased pump power. 



Fig. 155 shows a type of vertical heater with a three-way pass, and 

 affording a low velocity to the juice in transit. A horizontal type designed 

 for a high velocity with twelve changes of direction is shown in Fig. 156. 

 The horizontal and vertical arrangement is interchangeable in these types. 

 The diameter of tube in these heaters is usually from I to I J inches. A type 

 of heater common in Cuba consists of a steel cylindrical shell enclosing a 

 steel spiral. The shell may be as long as forty feet, and be three feet hi 



FIG. 156 



diameter. These heaters are used on unlimed juice, and are expected to 

 operate, a whole crop without cleaning, delivering juice at a temperature of 

 150 to 160 F. to defecators in which the heating is completed. 



The quantity of heating surface required will depend on the steam 

 pressure used, on the liability to scale, and on the velocity of the juice in 

 the heater. With freshly cleaned heaters, with a travel of 250 feet per 

 minute, and with steam at 5 Ibs. gauge, it is possible to heat one ton of 

 juice per hour from 80 F. to 212 F. with 10 sq. ft. of heating surface. The 

 efficiency, however, falls very rapidly, and there should be installed 40 

 sq. ft. per ton-cane-hour. This heating surface may conveniently be divided 

 into three units of 13 sq. ft. each, of which two operate while one is thrown 

 out daily for cleaning. 



Instead of using tubular heaters, the juice may be heated in the vessels 

 in which the settling takes place, and these vessels then become known as 

 Defecators. Two styles of heating elements are used. One evidently 

 derived from Taylor's patent (4032, 1816) and shown in Fig. 157, consists of 

 a system of straight tubes a, collected into a header b, about which the 

 system can rotate for purposes of cleaning. This system is used with rec- 

 tangular vessels, and when provided with a gutter they are known as Elimina- 

 tors in the British West Indies, and as Fletcher Pans in Java. They were, 

 and still are, used to boil juices and to skim off the scums that rise into the 



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