Drying.
—This operation consists of extracting the moisture from the tankage by means of air which is used as a vehicle to carry away the moisture. Various devices are employed for performing this function, such as barometric condensers, siphon tees, pipe condensers, and fan with air wash tower. There is some objection to all of these types, and each operator usually has some home-made device based upon experience. The fan is the more logical; it sweeps a large volume of air through the dryer by withdrawing it and passing it to the wash tower. The air carries away the moisture. To dry cheaply have a positive circulation of air through the dryer by keeping the inlet open, the fan attached to the air outlet connection. Single or multiple of dryers can be arranged on one fan.
Dryers.
—The principal apparatus in the fertilizer department is the dryer. Of these there are several types.
Direct Fire Dryers.
—In direct fire dryers, the tankage and flame produced by the use of oil, coke or coal, are introduced and passed through a cylindrical rotating machine similar to a cement dryer. The dried tankage is discharged at the opposite end from the feed, and the gases and moisture pass through a water spray and chimney to the air. It is practically impossible to operate a dryer of this type without producing an offensive odor in the surrounding territory and they are also considered hazardous from a fire standpoint.
Smith Type.
—This type of dryer is shown in the illustration ([Fig. 75]) and is of the steam jacketed type. The barrel is stationary with a revolving shaft and extended arms carrying the tankage upward which falls back through the air.
Ord Type.
—This dryer is also illustrated, [Fig. 76], and is of the same type, except that the shaft is placed vertical and the revolving arms at right angle to the shaft device which accomplishes the same result.