Stainless Steel Thermal Screw Processors for Cooling and Conveying Wood Biomass Char

General Description

Ensyn Corporation is a producer of renewable liquid fuels derived from wood biomass and agricultural residues. Ensyn’s principal product is RFO™, a liquid biofuel that is a heating fuel and is also a feedstock for refineries for the production of gasoline and diesel. This biofuel is extracted from wood char cake that undergoes special processing. As part of the overall process, Ensyn required a system of stainless steel thermal screw processors to cool the wood char as it exited from a filter press and convey the cooled material to a bulk bagging operation. KWS worked hand-in-hand with Ensyn to develop a successful solution for this project.

Design Parameters

KWS Advantages

Ensyn contacted Rate Technology Systems, the KWS manufacturer representative for eastern Canada at the preliminary stages of the project. They were looking for an experienced manufacturer to solve some major process problems. Ensyn had used a flexible wall belt conveyor to transport the material at the plant, but the conveyor belt was very difficult to clean. Also, the belt conveyor was not a good solution for capturing unpleasant fumes from the filter cake. KWS offered a thermal screw processor solution that cooled the filter cake by at least 50-degrees F and would reliably convey the product to the bulk bagging operation. Cooling the filter cake drastically reduced the odor and fumes. The gas and vapor-tight design of the thermal screw processor captured any remaining fumes and eliminated any odor in the process. Engineers at Ensyn and KWS worked very closely together over the course of several months to design a solution, create an accurate budget and develop a timeline for the project. KWS designed special thermal processors utilizing a hollow center pipe and jacketed trough that provided the necessary surface area for cooling the hot filter cake. The KWS engineering team laid out the entire system in Autodesk Inventor 3D so the Customer could identify space constraints and eliminate interferences. KWS also supplied the interfaces with the filter press outlet and designed structural supports.

Special Features

Filter cake exits the belt press in 200 lb. batches of sticky, sluggish clumps every 30 minutes. The filter cake is corrosive so KWS recommended 304-stainless steel construction. KWS designed a special screw feeder with hopper large enough to handle multiple batches. The screw feeder was designed and manufactured with special cut flights and an electro-polished finish to chop up the material and make sure it doesn’t stick to the screw. The screw feeder metered the filter cake to two inclined 12-inch diameter thermal screw processors in series. The thermal screw processors utilized ribbon flighting to reliably convey the sticky, sluggish material up a 24 degree incline. The ribbon screw design prevented the sticky material from adhering to the flighting where it meets the pipe. The thermal screw processors were sized based on the heat load of the system and to allow for large lumps. Retention time for cooling is also very important so the screw speeds are less than 10-rpm. The covers of thermal screw processors were shrouded so the material would be conveyed up a tubular profile and thus convey more efficiently. Each cover also had couplings for a vapor capturing system. KWS also designed special inspection ports on the thermal screw processors so operators could safely monitor the process.