THE EVAPORATION OF THE JUICE TO SYRUP. 



can be condensed by the juice. The megass corresponding to 1 000 Ibs. of juice 

 will roughly afford 1,000,000 B.T.U., so that the saving calculated on the 

 megass available for fuel will be between 4 and 5 per cent. 



If this scheme is used it must be remembered that the juice is at 

 atmospheric pressure and the heating vapour under a high vacuum ; unless the 

 the apparatus is carefully constructed and maintained in good order there is 

 then danger of juice being carried away int.o the condenser. 



Condensers. The condensers which find use in forming and main- 

 taining the vacuum in the last body of an effect may be classed as jet or surface 



condensers, or again as dry or wet con- 

 densers. Surface condensers are only used 

 where the vapour from the last body is 

 used to heat juices, as explained imme- 

 diately above. 



The injection condenser, usually 

 employed to condense the vapours given 

 off from the last body of an effect, consists 

 essentially of a cast-iron cylindrical body 

 connected by a pipe, called the vapour pipe, 

 to the vapour space of the effect, and also 

 by a second pipe to the suction of an air 

 pump ; a third pipe called the injection 

 pipe leads water from a well to the con- 

 denser. A vacuum being formed in the 

 condenser by means of the pump, water 

 enters the condenser under the influence of 

 atmospheric pressure. The vapour given 

 off from the effect meeting the stream of 

 cold water is condensed, and the vacuum 

 maintained ; the condenser water and 

 incondensible gases pass to the pump and 

 are there discharged. 



As the efficiency of a multiple effect depends very largely on the vacuum 

 in the last body, and this in turn on the completeness of the condensation, 

 attention to the design of the condenser is important. The commonest method 

 of distributing the injection water within the condenser is by means of a rose ; 

 with this arrangement there is liability of the holes becoming choked, 

 especially when any but the cleanest water is available. Better arrangements 

 are shown in Figs. 180 and 181. In the form shown in Fig. 180 the vapour 

 enters at a and the injection water at b ; the whole then follows the path 

 indicated by the arrows through the apertures in the plates, and is discharged 

 at d to the air pump. In the form shown in Fig. 181 the injection water 



FIG. 181. 



325 



