x= lb moisture/Ib dry solid Figure 9. Typical rate-of-drying curve, constant drying conditions When manufacturing large quantities of a product which does not require tight batch controls, a more efficient operation(usually less expen sive)results by drying the product in a continuous or semi-continuous fashion. The product, in one case, can be batch-stored in large vessels and fed at a continuous rate to the dryer. The product is usually dried in small quantities thus requiring a long time to process the entire amount in a smaller, more efficient piece of equipment. In another situation, ideal for continuous operation, the product would be manufactured upstream of the dryer in atrue plug flow manner and transferred to the dryer at a constant rate. In other words, the dryer's capacity matches that of the upstream equipment. This is the most efficient manner 5.1 Batch Direct Dryers Most direct batch dryers are fluid bed types such as those which retain the batch on a screen while pneumatically fluidizing the product. Mechani cally agitated or tumble rotary dryers also exist. If the product is temperatureDrying 739 Figure 9. Typical rate-of-dqing curve, constant drying conditions. When manufacturing large quantities of a product which does not require tight batch controls, a more efficient operation (usually less expen￾sive) results by drymg the product in a continuous or semi-continuous fashion. The product, in one case, can be batch-stored in large vessels and fed at a continuous rate to the dryer. The product is usually dried in small quantities thus requiring a long time to process the entire amount in a smaller, more efficient piece of equipment. In another situation, ideal for continuous operation, the product would be manufactured upstream ofthe dryer in a true plug flow manner and transferred to the dryer at a constant rate. In other words, the dryer’s capacity matches that of the upstream equipment. This is the most efficient manner. 5.1 Batch Direct Dryers Most direct batch dryers are fluid bed types such as those which retain the batch on a screen while pneumatically fluidizing the product. Mechani￾cally agitated or tumble rotary dryers also exist. Ifthe product is temperature