Conveying Wet Starch Cake with Ribbon Screw Conveyors
Plant Name and LocationNational Starch Chemical Corp
Salisbury, NC
General Description
National Starch produces starch-based ingredients for the food, beverage, and brewing industries along with industrial starches. As part of their process at the Salisbury, NC plant, excess liquid is removed from the wet starch cake by centrifuges and then conveyed to multiple silos or a dryer on a lower floor. National Starch looked to KWS to design a solution that added flexibility to their process.
Design Parameters
- Product Type: Wet Starch Cake
- Material Density: 30-32 Lbs. per Cubic Foot
- System Capacity: 300 Cubic Feet per Hour
- Duty: 24 Hours per Day, 7 Days per Week
KWS Advantages
National Starch required a conveying system utilizing fully reversible screw conveyors that fed either silos or a dryer, depending upon the needs of their downstream process. The screw conveyors were designed to act as one system and convey different types of starch. This expansion project unfolded over the span of several years and the engineers at KWS were up to the task. There were many technical challenges due to the complexity of the process and many design variables that needed to be solved. The combined experience and knowledge of the National Starch and KWS engineering teams provided a reliable conveying system and optimized the process.
Special Features
Wet starch cake can be very sticky and sluggish to convey. KWS engineers designed high-quality stainless steel ribbon screws that were fed in the center and fully reversible to discharge on either end allowing process flexibility and redundancy. KWS selected ribbon flights to handle the wet cake material and prevent it from sticking to the screw and pipe. KWS polished the screws to 180-grit finish on all surfaces and then electro-polished them to create a mirror finish. The mirror finish eliminated any chance of the wet cake sticking to the screw surfaces. Since the screw conveyors were often cleaned with alcohol or boiling water, KWS provided special UHMW polyethylene blend trough liners for chemical and heat resistance. The UHMW trough liners provided a low-friction surface and reduced the chance of wet cake sticking to the trough surfaces. The liners were designed to be held in place but to also expand and contract with changes in temperature. KWS incorporated variable frequency drives to vary the discharge rate of the conveying system. The variable frequency drives allowed the Customer to modify conveyor output, depending on their process needs. The units were designed on a slight negative slope for easy drainage and cleaning. The complete conveying system was designed to be fully purgeable with nitrogen (thus being explosion proof) inside the troughs and at the seals. Explosion-proof motors were also supplied with the conveyors.
Testimonial
"Thank you KWS for providing a great solution for our process."
Jeff Sollenberger, Engineering Manager – National Starch (2009)
