Screw Conveyor Classifier Separates Slurry Mixture Containing Glass Microspheres

General Description

Nextrast is a biotechnology company that develops contrasting agents for taking medical images. A silicon-based, orally administered contrasting agent delivers sharp and unambiguous medical images in a single CT pass reducing potential radiation exposure. Nextrast’s technology was developed by its founders at the University of California San Francisco.

Nextrast contacted KWS to help them separate and convey a slurry mixture based on density in an enclosed aqueous system. As the slurry enters and travels across a screw conveyor tank, the material will slowly separate based on the difference in density. Only the floating portion will be collected at the end of the conveyor tank.

KWS worked with Nextrast to design an experimental screw conveyor classifier that would convey the material on top of the liquid and then allow the liquid to be drained out the bottom of the unit. The floating material is moved over the weir to discharge for further processing.

Design Parameters

1. Product Type: Glass Microsphere Slurry
2. Material Density: 10 Lbs. per Cubic Foot
3. Capacity: 35 Cubic Feet per Hour
4. Designed Duty: 24 Hours per Day, 7 Days per Week

KWS Advantages

KWS worked with Nextrast to develop a prototype screw conveyor classifier for the application. Samples of the slurry mixture were examined and tested to determine a simple yet long term solution. The information and application knowledge provided by Nextrast to KWS was very valuable for the success of the application.

KWS Special Features

The KWS screw conveyor classifier was constructed from 304 stainless steel to eliminate corrosion and potential contamination of the slurry. An adjustable weir was located at the end of the conveyor so the floating material could separate from the liquid and discharge to downstream processing.

A bulkhead trough end was located on the drive end with direct-drive shaft mounted gear motor. Purgeable shaft seals were located on both ends to contain the liquid within the conveyor. Shaft seals and gear motor can be easily accessed for maintenance and replacement.

Nextrast required that the conveyor covers be hinged for access and periodic clean out. KWS provided the covers with safety bolts. Safety bolts require a specific tool for access by only trained maintenance personnel. Two safety bolts were installed on every cover to prevent access to moving components.

The screw was designed with very short pitch between the flights to better convey the floating material. Both the drive and tail shafts were fitted to the center pipe of the screw and seal welded in place to prevent liquid from entering the center pipe and contaminating the slurry.