Grit Classifiers for Activated Carbon Plant

<!--

--> Plant Name and Location

Carbon Plant
Wickliffe, KY

General Description

Activated carbon is used in a variety of applications including automotive emission filtration systems and water treatment. The final product begins its life as wood chips or sawdust that is first processed into charcoal, then further modified to provide a very high surface area to volume ratio. Microscopic pores in the finished product trap contaminants while allowing the medium, such as water or air, to pass through freely. KWS Manufacturing has provided high quality screw conveyors for the activated carbon industry for over 40 years.

Grit Classifiers for Activated Carbon Plant

Nine KWS Classifiers are in Series to Wash the Char

Design Parameters

Product Type: Wood Char and Acid Mixture
Material Density: 69.3 Lbs. per Cubic Foot
Moisture Content: 28-Percent Solids
Temperature: 200-Degrees F
Capacity: 282 Cubic Feet per Hour
Duty: 24 Hours per Day, 7 Days per Week

KWS Advantages

After the wood char has been “activated” (surface area increased by physical and chemical processes) it has a high acid content. A succession of dewatering classifiers are used to wash the char and remove the acid from the mixture. A classifier consists of a large reservoir hopper with an inclined screw feeder. A combination of wood char and water enters the reservoir hopper through a pipe connection. The char falls out of suspension by gravity and settles to the bottom of the reservoir hopper. The screw feeder rotates very slowly, removes the char and delivers it to the next classifier for further washing.

By pumping the mixture into the classifier hopper with clean water, the acid is diluted as the wood char settles to the bottom of the screw conveyor. This process continues through a total of nine classifiers before proceeding to the drying equipment. KWS is the leader in the screw conveyor industry when it comes to providing effective long-term solutions. Not only is the mixture abrasive but the acid is highly corrosive. Heavy duty stainless steel construction is required to withstand this application.

Special Features

The classifiers are located in a very congested area and access for maintenance is very limited. The screws in the classifiers are long, single-piece screws that can be difficult to replace due to space constraints. KWS designed a split, two-piece drive trough end that can be removed to allow access for screw removal without having to completely disassemble the drive unit. KWS designed the classifiers with close clearance screws to decrease the gap between the trough and the outside diameter of the screw. The close clearance provides better cleanout with very little char left in the trough.

The classifier hoppers are designed to hold a large amount of water and leakage is a prime concern. The complete classifier tank and trough assembly is a weldment so there are no opportunities for leakage. The lower end of the screw is supported with the KWS exclusive dead-end shaft. The KWS dead-end shaft is flanged and bolts to the hopper using a completely leak-free gasketed mounting plate and projects internally. The tail end of the screw contains an internal Stellite bushing for the bearing surface. The screw rotates over the stationary dead-end shaft. The KWS dead-end shaft and Stellite bushing require little maintenance and are easy to replace. Stellite is a very hard, tough and abrasion resistant material that will easily hold up to the abrasive wood char mixture.