CANE SUGAR. 



Greiner Pan. The pan designed by Greiner was amongst the first 

 departures from the * Standard ' pattern. It was constructed with the idea of 

 obtaining a large heating surface and placing the same all in the lower part 

 of the pan, so that the whole heating surface would be in use from the start of 

 the boiling. As now made it is shown partly in section in Fig. 192. The 

 heating surface consists of a number of concentric elements supported on cast- 

 iron standards. Steam is admitted and condensed water taken away at the 

 bottom of each element ; the valve A controls the admission of steam to 

 the small elements used in the process of obtaining grain, and that at B to the 

 larger elements used when the pan is working at its full capacity. 



Shape of Pan. Following on the principles developed in Chapter 

 XVI. it is easy to see that high pans of small diameter will be less efficient 

 than shallower pans, since the height of the column of massecuite will 

 materially increase the boiling temperature of the mass ; on the other hand, 

 there are mechanical difficulties in the way of indefinitely increasing the 

 diameter of pans, and with helical coils as heating surface, as shown imme- 

 diately above, the longer coils required in pans of large diameter tend to 

 become very inefficient ; the most efficient shape of pan then becomes one 

 of considerable diameter in proportion to height, with a tubular or short coil 

 system of heating surface. 



Technique of Boiling. The actual process of boiling the pan may 

 be divided into three stages : the granulation, the growing of the crystals, and 

 the bringing up to strike. The granulation is effected by forming in the pan 

 a solution of sugar saturated at a certain temperature, and then by causing 

 the temperature to fall to make the sugar crystallize. Different methods for 

 effecting this exist : the temperature may be lowered by increasing the quan- 

 tity of injection water and so obtaining a more complete vacuum, by shutting 

 off the supply of steam from the coils, or by introducing a quantity of cold 

 syrup; in whatever way the granulation is obtained the sugar separates as 

 minute, barely visible crystals. In forming grain some pan boilers take in at 

 one charge the whole amount of syrup from which they intend to granulate, 

 and others take in smaller charges gradually working up to the requisite 

 amount. Instead of forming grain from the syrup the practice of seed grain is 

 extensively followed ; in this process a quantity of a small grained sugar 

 obtained from previous work is taken into the pan, together with the first 

 charge of syrup, and the crystals thus introduced form the points upon which 

 the sugar deposits in the subsequent process ; the sugar used is generally the 

 small grained sugar resulting from the after-boilings of molasses. One ton of 

 such sugar can in general be used as grain for every 25 or 30 tons of masse- 

 cuite that the pan holds. This procedure, besides saving time in boiling the 

 first charge of grain, forms a very economical method of suppressing a portion 

 of the low products. In forming grain the quantity of syrup used for granu- 



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