THE: SPRAY PROCESS 309 



feet of the uncontrollable fluctuations in the humidity of the at- 

 mospheric air, as affected by weather conditions. However, in 

 commercial operation the artificial drying of the atmospheric air 

 is generally omitted. 



The air may be blown into the desiccating chamber by a 

 blower fan, in which case a suction fan is frequently also installed 

 to draw the moisture-laden air from the desiccating chamber ; or the 

 injection of the air into the drying chamber may all be taken care 

 of by a strong suction fan located at the air exhaust end of the 

 desiccating chamber. It is claimed that the double arrangement 

 of blowing in and drawing out of the heated' air, requiring less 

 powerful suction at the exhaust end, minimizes the escape of milk 

 powder with the moisture-laden air and thereby facilitates the 

 recovery. The speed of the drying action and the exhaustiveness 

 of desiccation may be augmented by introducing the air in such a 

 manner as to produce a cyclonic air current moving spirally toward 

 the center of the drying chamber, where it escapes while the milk 

 spray issues from the center, is acted on by the centrifugal force 

 and moves tangentially toward the periphery as shown in the Gray 

 patents. 



The temperature of the air as it enters the desiccating cham- 

 ber is generally held at from 250 to 300 F., the temperature of 

 the moisture-laden air discharging from the drying chamber ranges 

 from 150 F. to 200 F. 



Spraying and Desiccating. The drying is accomplished by 

 forcing the milk or condensed milk, in the form of an atomized 

 spray, into the current of heated air in such a manner, that the 

 fluid milk particles, or atoms of the milk spray, remain in suspen- 

 sion sufficiently long to cause them to surrender substantially all 

 of their moisture. The dried particles or flakes of milk are al- 

 lowed to deposit at the bottom or sides of the drying chamber or in 

 a separate collecting chamber, from where they are removed for 

 sifting and packing through a hopper, while the moisture-laden air 

 escapes separately to the outside. 



The Desiccating Chamber. The desiccating chambers in 

 commercial use vary considerably in size and in shape, as well as 

 in arrangement of spray nozzles and intake and outlet of heated 

 air. 



