MANUFACTURE: OF MILK 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 Merr ell- Gere Process. The milk is condensed in the 

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



Fig. 62. The Campbell milk drier 



I A concentrated vessel, a outlet, b valve, c hot water jacket, c 1 hot 

 water pipe, c 2 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. 



