Shaftless Screw Conveyors for Pyrolysis of Waste Plastic and Scrap Tires

General Description

The United States produces over 40 million tons of waste plastic, and 4 million tons of scrap tires each year. Approximately 75-percent of plastic waste ends up in landfills, with only 10-percent being recycled. About 20-percent of scrap tires end up in landfills. The majority are reused for tire-derived fuel, ground rubber applications, and civil engineering uses.

Pyrolysis is the thermochemical decomposition of material at elevated temperatures in the absence of oxygen. It is a proven and commercially viable technology used in the recycling and waste-to-energy industries to convert waste plastic and trash into fuel oil through processes that are scalable, flexible, and environmentally positive. In general, pyrolysis of various substances produces gas and liquid products and leaves a solid residue called char that is rich in carbon content. Pyrolysis converts waste materials into sustainable biofuels and is in great demand because it is an environmentally friendly technology.

KWS partners with many different technology providers to design mechanical conveying systems for injecting waste materials into the pyrolysis process and convert waste to usable gases and liquids. Typically, mechanical conveying systems are subjected to temperatures up to 1,700-degrees F. KWS has developed solutions to satisfy the unique needs of the pyrolysis industry.

Design Parameters

1. Product Type: Coal, Scrap Tires, and Scrap Plastic
2. Material Density: Coal = 35 to 58 Lbs. per Cubic Foot
3. Capacity: 100 Cubic Feet per Hour
4. Duty: 24 Hours per Day, 7 Days per Week
5. Design Temperature: 752-Degrees F

KWS Advantages

KWS has decades of engineering experience, and our Engineers work closely with our customers to design and manufacture solutions to meet their needs. Since each process is unique, it is important for KWS to fully understand the application and customer requirements. KWS works to provide seamless integration throughout the process, from initial design to installation and start-up.

KWS Special Features

KWS equipment used in the pyrolysis industry is designed to withstand temperatures up to 2,000-degrees F with internal pressures of 10-psi. Shaftless screw conveyors are a logical selection for high temperature applications since there are no internal bearings. For this specific application, KWS manufactured the shaftless flighting from Nitronic 60 material for the outer wear spiral and Inconel 625 for the inner spiral. Inconel 625 maintains high yield strengths at elevated temperatures and is corrosion and abrasive resistant. Nitronic 60 provides a non-galling surface at elevated temperatures.

Conveyor housings were constructed from 310 stainless steel pipe with Class-150 slip-on flanges at every connection to hold at least 10-psi. Extended pedestal drive bases with special shaft couplings were required to keep drive components away from extreme heat. Conveyor operating speed was less than 8-rpm to reduce abrasion on spiral and housing.