MULTIPLE EFFECTS. 35 J^ 



Plate XLI represents a triple effect evaporating apparatus, as man- 

 ufactured by the Colwell Iron-Works, many sets of which are in use 

 upon sugar plantations, as also in the manufacture of beet sugar. 

 The triple effect is the most economical method of evaporation, as it is all 

 done in vacuum. A general description of this apparatus is as follows : 



It is composed of three cast-iron vacuum pans, so arranged that the 

 vapor generated in the first pan passes to the heating surface of the sec- 

 ond pan, where it boils the liquor; and the vapor thus generated 

 passes to the third, where it boils the syrup ; while the vapor from 

 this third pan passes to the condenser, and is drawn off by means of the 

 vacuum jiump. The fii*st pan receives its steam from the exhaust 

 steam recipient, which also supplies the vacuum pan. 



By this method, there will be required only thirty-five per cent of 

 the steam and water for the proper operation of these pans which 

 would be necessary were all the evaporation done in a single vessel ; 

 but this method of evaporation Avill only hold good on liquor up to 28 

 or 30° Beaume. 



The interior heating surface of these pans consists of two-inch copper 

 tubes, expanded into composition heads, which are properly secured in 

 the lower curbs of the pans. There is also a suitable large circulatino- 

 pipe. The mountings of the pans are about the same as in the vacuum 

 pan. By a system of valves and vapor pipes, any of the pans can be 

 connected directly with the condenser at will, thus making it single, 

 double, or triple effect. 



The course of the liquor is as follows : 



The pump upon the left of the cut draws the defecated liquor from 

 the deposit tanks, the sjieed being so regulated that the pan is kept at 

 a certain level, the vacuum being about 5 inches and the heat about 

 180° F. It is here evaporated to about 15 or 16° Beaume, and, bv 

 means of a discharge cock and pipe, is fed into the second pan in such 

 a quantity as to maintain a fixed level. It is here reduced to about 

 20° Beaume, and a temperature of say 150° F., and, by means of a 

 discharge cock to this pan, the third pan is supplied in the same man- 

 ner. Here the concentration goes on till at the finishing pointy 25 to 

 28° Beaume ; then, by means of the condenser and vacuum pump, the 

 necessary vacuum is maintained, in order to finish at as low a temper- 

 ature as possible. It is now drawn off by means of a montjus, or 

 pump, and passes to the clarifiers. 



The operation is continuous, provided there is a proper supply of 

 defecated juice. 



The saving of fuel and labor by this method over the steam or fire 

 trains is one of the great incentives in adopting this large piece of ma- 



