280 MANUFACTURE OF MirK PowprR 
otherwise. ‘Phis subdivided product is then placed on shelves 
or trays and dried in a chamber heated to a temperature below 
the coagulating point of the albumen. 
rr} > 
HOT WATER 
BLOWER ( 
H 
Fig. 91. The Campbell milk drier 
I. A concentrating vessel, a outlet, b valve, ec hot water jacket, c! hot 
water pipe, c* discharge of jacket, B air pipe, e connecting hose, f stand pipe, 
g air-distributing dise, t air chamber.—II. E pug mill, i cylinder, j hopper, 
k chute, 1 horizontal shaft, m blades for stirring, m’ projections for scraping 
blades, F Vermicelli-machine, n hopper, o cylindrical chamber, p piston, q 
spiral screw, q’ worm-wheel, 0’ small holes, nr endless traveling apron, s tray 
with perforated bottom.—III. G drier, t body of drier, H blower, t’ flue, u 
opening to insert trays, u’ opening for removing trays, vv endless chains with 
projections for supporting trays, w coil heater, w’ pipe circulating hot water. 
In the processes of the dough-drying principle of desiccation, 
the dried product is reduced to a marketable powder by grinding 
it and then bolting or or sifting it. 
2. Film-Drying Processes. 
‘To this group belong the numerous processes in which the 
milk, with or without previous concentration, 1s dried on the 
surface of one or more steam-heated, revolving drums. ‘The 
mill is either picked up by the revolving drums, or it is sprayed 
onto these drums, forming a thin film which dries rapidly. The 
film of dried milk so formed is atomatically removed with each 
revolution of the drum by means of a mechanical scraper. In 
some of the processes of the film-drying type the drying cyl- 
inders operate in the open, under atmospheric pressure, in others 
