Mixing Screw Conveyor for Polyethylene Powder & Additives LyondellBassell in LaPorte, TX

General Description

Over 100 million tons of polyethylene resins are produced worldwide annually, accounting for 34-percent of the total plastics market. Common products that are used every day such as water bottles, plastic bags and even automobile parts and piping are made from polyethylene resins. Currently, the medical industry has a huge need for N95 medical masks and face shields due to the COVID-19 crisis.

LyondellBasell is one of the world’s largest chemical producers. A subsidiary, Equistar Chemicals suppliers of polymer products including polyolefin resins and polyethylene, was undergoing an expansion of an extrusion line and required new loss-in-weight additive feeders and a mixing screw conveyor. The conveyor receives various additives from six loss-in-weight feeders, provides complete mixing and delivers the compound in a continuous flow to the extruder.

Design Parameters

1. Product Type: HDPE Powders & Pure Additives
2. Material Density: 23.1 to 28.1 Lbs. per Cubic Foot
3. Conveyor System Capacity: 6,739 Cubic feet per Hour
4. Design Temperature: 248-Degrees F
5. Duty: Continuous

KWS Advantages

Bechtel provided engineering and construction services to LyondellBasell for the project and selected Coperion K-Tron to provide the loss-in-weight feeders and the mixing screw conveyor. Coperion K-Tron and KWS have a great working relationship and have completed many successful projects together. KWS supplied the mixing screw conveyor to Coperion K-Tron for the LyondellBassell project.

Engineers from Coperion K-Tron and KWS met at the plant in LaPorte to discuss details of the project with engineers from Bechtel and LyondellBassell. Polyethylene resin purity was a major concern and the loss-in-weight feeders and mixing screw conveyor had to meet very strict quality standards. KWS is an ISO9001-2015 certified company with a very detailed Quality Management System. Bechtel quality inspectors reviewed the KWS quality documentation and were very satisfied.

KWS provided complete material traceability with material test reports and positive material identification testing services. Bechtel quality inspectors visited KWS to perform dimensional checks and witness factory acceptance testing of the screw conveyor prior to shipment.

Special Features

The mixing screw conveyor was over 28-feet long. No internal bearings were allowed due to possible contamination of resin compound. KWS designed a single piece screw mounted on oversized pipe to prevent excessive screw deflection. KWS also added cut flights to the screw with notches every 90-degrees to promote mixing and agitation as the materials are conveyed. For additional mixing action, KWS fitted the screw with adjustable paddles every pitch. Double flights were added at the discharge end of the screw to provide smooth discharge to the extruder.

The internal surfaces of the mixing screw conveyor had to be smooth to prevent material build up. KWS polished all surfaces of the screw, trough and welds to a 150-grit finish with no crevices. Then, the screw was coated with Impreglon non-stick coating for enhanced release properties.

Some of the additives enter the KWS mixing screw conveyor above 225-degrees F. The gear reducer and motor are mounted on a specially designed pedestal and located away from the heat source to prevent possible failure. All rotating parts are guarded with OSHA compliant guards.