Custom Solutions for Direct Heat Drying

CUSTOM SOLUTIONS

LDC Rotary Direct Heat Dryers are manufactured in two basic configurations:

Co-current (also referred to as parallel flow)
Counter-current (also referred to as counterflow)

Co-Current Rotary Dryer

Many Louisville direct heat dryers are provided in co-current orientation. With the co-current or parallel flow dryer, wet material is introduced into the drum on the same end that the hot gas enters the dryer. Conversely, dry material discharges on the same end of the dryer as the exhaust vapor. The co-current dryer offers two advantages:

• The wettest material comes in contact with the hottest gas as they enter the dryer. This results in a rapid evaporation and rapid cooling of the hot process gas. This typically allows the dryer shell to operate slightly cooler than the counterflow configuration, which extends the life cycle and decreases maintenance of the dryer.

• Since the dry product and vapor exit the dryer on the same end, a correlation exists between the exhaust gas temperature and the condition of the dried product. The LDC burner management system responds to the exhaust gas temperature which ensures instantaneous heat load adjustment to varying conditions upstream of the dryer.

Counter-Current Rotary Dryer

Louisville direct heat dryers are provided in counter-current dryer orientation when the application is warranted. With the counter-current or counterflow dryer, wet material is introduced into the drum on the opposite end that the hot gas enters the dryer and dry material discharges on the opposite end of the dryer as the exhaust vapor. The counter-current dryer is usually considered for processes such as:

• The material is going to be heated in addition to drying. In some aggregate and ore processing applications, it is desired that the material be heated. In those applications, material enters the cold end of the drum and travels towards the hot end. Since the exhaust vapor exits opposite the material, there is no relationship between the temperatures. The product temperature can be hundreds of degrees hotter than the exhaust vapor providing lower stack loss and greater thermal efficiency.

• Material has internal moisture. Some materials contain a high percentage of internal moisture. These materials require sufficient time for the water to migrate to the surface of the particle for evaporation.

The direct heat dryer has a unique set of design requirements considering the potential need to somewhat isolate the atmosphere for proper processing. When it comes to seals, clearly one size does not fit all. Louisville Dryer Company can offer many different types of drum sealing devices specifically designed to meet the needs of the application.

Custom Solutions for Direct Heat Drying