290 MANUFACTURE OF MiivK POWDER 



revolves and the layer of milk reaches what is termed the front 

 of the machine it is continuously removed in the form of a dry 

 film by a stationary scraper. At this point the machine is pro- 

 vided with a breaker which consists of a shaft with a number 

 of rods projecting through the same, which revolves to break 

 up the film of dried milk as it leaves the drum. This does not 

 reduce the film to a powder, but causes the material to be suffi- 

 ciently broken up to allow it to fall into the receiver where it 

 can be easily handled for removal. 



The receiver is a large cylindrical pan placed below the 

 scraper at the front of the machine. Observation glasses are 

 placed so that all internal parts may be seen while being operated. 

 The receiver is equipped at each end with a door of the full width 

 of the receiver, facilitating the rapid removal of the dried milk. 



Aside from the circulating pump for supplying the milk to 

 the feed pan, there is a condenser and a dry vacuum pump. Be- 

 fore the vapors reach the condenser, they pass through a dust 

 collector. This is water-sealed and prevents the accumulation 

 in the vapor pipe of any dust that may escape from the drum 

 and pass to the condenser. 



This drier is operated under a high vacuum, permitting rapid 

 evaporation at a relatively low temperature. The actual drying 

 time of the film of milk on the drum is about 6 to 7 seconds. 

 The operation is continuous and at the conclusion of the day's 

 run the machine is washed out. If subsequently closed up and 

 evacuated for a few minutes, the entire interior will be dry. in- 

 suring a sanitary condition of the machine. 



3. Spray-Drying Processes. 



To this group belong the several processes in which milk is 

 desiccated by atomizing it into a fine spray and in an atmosphere 

 or current of heated air. The small particles of the milk spray sur- 

 render their moisture quickly and drop to the bottom of the drying 

 chamber in the form of flakes of dried milk while the moisture- 

 laden air escapes to the exterior, screens or other forms of dust col- 

 lectors being provided to recover such parts of dried milk as may 

 escape from the drying chamber with the expelled air. The principle 

 of desiccating fluid substances by atomizing them into an atmosphere 



