ABSTRACT
To ensure that the dust load into the collectors is kept at a reasonable level, the air velocity through the dryers and coolers should not be excessive. Figure 4 shows a typical ammoniation granulation plant for a NPK mixture. It shows a plant that has a rotary ammoniator granulator, a rotary dryer, and a rotary cooler. These drums are usually common to MAP and DAP plants also. Tests have shown if the gas velocity through the dryer and cooler exceeds 2.0 rnls, the dust loading to the cyclone collectors will be too high for economical design of the collectors. Some companies overdesign the exhaust system so that they can realize higher velocities and increase efficiencies through the cyclones. When this is done, an extra fresh-air inlet duct is installed such as that shown in Fig. 5. The fresh-air inlet is generally used to suck dust from screening and crushing operations. With this arrangement it is possible to have optimum velocities in the dryer, cooler, and cyclone collectors.
