Pellet coolers and dryers

Alfalfa dehydration is carried out in a direct-fired rotary dryer. The dried product is transported pneumatically to an air cooler and then to a collecting cyclone. The collected particles are ground or pelletized and then packaged for shipment. The major atmospheric emission from the process is particulate matter, which is controlled by baghouses. Odors may also be a problem, but they disperse rapidly and are no longer a problem at distances of over 1 km. 

Fig. 8.47 a) Pellet press and b) dryer/cooler in an actual plant according to Fig. 8.46 (courtesy Amandus Kahl, Reinbek, Germany)... 

Other flaky chemicals obtained from drum coolers or dryers that have similar properties as those of the fresh DMT can be similarly converted into dense free flowing intermediate products by pelleting, briquetting, or compaction/granulation. Drum dryers feature heated drums that either dip into a bath of suspended particles or are coated by means of axial dispensers with the suspension. As in the case of drum coolers, dry solids are removed from the drum with scrapers and are typically bulky and dusty before suitable agglomeration has taken place. 

---