Rotary drum dryer

Ammonium sulfate is produced as a caprolactam by-product from the petrochemical industry, as a coke by-product, and synthetically through reaction of ammonia with sulfuric acid. Only the third process is covered in our discussion. The reaction between anunonia and sulfuric acid produces an ammonium sulfate solution that is continuously circulated through an evaporator to thicken the solution and to produce ammonium sulfate crystals. The crystals are separated from the liquor in a centrifuge, and the liquor is returned to the evaporator. The crystals are fed either to a fluidized bed or to a rotary drum dryer and are screened before bagging or bulk loading. 

The acid and the ammonia or ammoniating solution were sparged under the rolling bed of solids in the drum with a spacer arrangement, as shown in Fig. 24.16. With the proper balance of liquid and solid feeds, granulation occurs as a result of the rolling action in the action in the drum, and it is completed, with hardening, in a rotary-drum dryer. 

In the processing of the fish, after the oil is extracted, the fish cake is dried in rotary drum dryers, finely ground, and packed. The resulting product contains 65% protein. In a given batch of fish cake that contains 80% water (the remainder is dry cake), 100 kg of water is removed, and it is found that the fish cake is then 40% water. Calculate the weight of the fish cake originally put into the dryer. 

Salt removed with rotary-drum dryer. 

An advantage of the cascade dryer over the rotary drum dryer is the reduced space requirement, which may be critical when installing a dryer in combination with an existing boiler. Applications have been mainly as predryers in combination with wood-fuel boilers in saw and pulp mills. 

FIGURE 43.6 Rotary drum dryers (a) single-pass (Courtesy of Vadeb) (b) dryer equipped with disintegration device (Adapted from Imoto, Y. et ah, Dry. TechnoL, 11(7), 1495, 1993) (c) triple-pass (Courtesy of M-E-C Company) (d) cross-section of a triple-pass dryer. (Courtesy of M-E-C Company.)... 

A. Richard, M. Tomczak, M. Aubran, and E. Ronat, An approach to automation of rotary drum dryers, in Comparative Study of Industrial Applications in Drying of Solids, A.S. Mujumdar (Ed.), Sarita Prakashan, New Delhi, India, pp. 253-260 (1990). 

Fig. 1.10. Rotary drum dryer/kiln/furnace for drying, calcining, refining, incinerating granular materials such as ores, minerals, cements, aggregates, and wastes. Gravity moves material cocurrent with gases. (See fig. 4.3 for counterflow.)...

Rotary drum dryers, calciners, kilns, and incinerators tumble bulk material or pieces peripherally and lengthwise downhill, thus exposing all load surfaces, even... 

Fig. 4.3. A rotary drum dryer, kiln, incinerator, or furnace transports granular loads left to right) by gravity and rotation, counterflow to the burner gases and induced air. Parallel flow orco-current flow (fig. 1.10) can be used with some load materials and processes.

The usual method for removing the solvent from the cement is by means of steam-heated drum dryers, wherein a heated solution of the polymer is introduced into the nip of rotary drum dryers and solvent is removed by evaporation. As the solvent evaporates at the drum surface, a thin film of polymer is deposited, which continues to dry as the drum rotates. The dried film is doctored from the drum surface with a knife blade gathered into a rope and cut into small chips. It is then dusted with talc, to prevent massing, and then packaged. 

Fig. 9.8 A microwave-vacuum rotary drum dryer. Adopted from Kaensupeta/. (2002).

Experimental study on drying of chilli in a combined microwave-vacuum rotary drum dryer. Drying Technol. 20(10) 2067-2079. 

---