Manufacture of Mii^k Powder 



241 



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 opera- 

 tion 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 insuring a sanitary condition 

 of the machine. 



4. The Campbell Process. — A current of warm air passes 

 through the milk upward until the milk has become . thick. The 

 remainder of the drying is accomplished by exposure to heated air. 

 The dried milk is then ground to a powder. This is the Campbell 

 process, invented in 1900 and patented by J. H. Campbell of New 

 York in 1902. 



5. The Merrell-Gere Process. — The milk is condensed in the 

 vacuum pan to about one-third to one-fourth its volume. The con- 



C 



Fig. 62. The Campbell milk drier 



I A concentrated vessel, a outlet, b valve, c hot water jacket, c' hot 

 water pipe, c° discharge of jacket, B air pipe, e connecting hose, f stand pipe, 

 g air-distributing disc, 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, o' small holes, r 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 circu- 

 lating hot water. 



