290 MANUFACTURE OF Mit,K 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 seraper. 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. his 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 cach 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. Pe- 
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. he 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 
