Cantilevered Screw Conveyor for Injecting Coal Into Dryer

General Description

Heyl Patterson Thermal Processing (HPTP) has been designing and building high efficiency industrial dryers and coolers for the powder and bulk solids industry for nearly 150 years and is known as one of the best in the business. For drying and cooling, HPTP offers different product lines suited for specific applications and materials. Among others, one of their drying technologies used in industries around the world includes rotary dryers & coolers.

For a large project in the Western United States, Heyl Patterson supplied a rotary dryer for the Powder River Basin coal mining industry. To continuously feed powder coal to a dryer, the engineering team at HPTP developed an open-ended cantilevered injection screw conveyor that would mate directly to the breach of their rotary dryer. With our history of collaboration, HPTP chose KWS as the best partner to supply the screw conveyor for this project.

Design Parameters

1. Product Type: Powder River Basin Coal
2. Material Density: 35 Lbs. per Cubic Foot
3. Conveyor System Capacity: 125 Cubic feet per Hour
4. Duty: Continuous

KWS Advantages

HPTP needed a manufacturer that could take their concept and turn it into reality. The sales team of engineers at KWS joined forces with the engineering team at HPTP to develop the ideal sizing and design based on specific process parameters.

Providing high-quality equipment is of the utmost importance to HPTP. Therefore, as detailed in the specification, it was critical that all welding conforms to the American Welding Society (AWS) Code. KWS employs all AWS certified welders and was able to provide HPTP with weld procedures and welder certifications.

Special Features

A cantilever screw is only supported on the inlet end by the drive shaft and two bearings. The cantilevered design allows bulk materials to discharge directly from the end of the conveyor and eliminates the need for a tail bearing in the breach of the dryer. The double bearing arrangement on the inlet end is designed to handle the cantilevered load of the screw as well as thrust loads and misalignment.

KWS has specific designs for cantilevered screw conveyors and hundreds of successful installations. The KWS Torque Arm Trough End was uniquely designed for cantilevered screw conveyors. Using a shaft-mounted gear reducer, the trough end allows the gear reducer the freedom to “float”, reducing radial loads and increasing overall reliability.

The temperature at the inlet of the dryer was in excess of 300-degrees F. The KWS cantilevered screw conveyor was constructed from 304 stainless steel to resist corrosion at elevated temperatures. Since rotary dryers are kept under negative pressure, KWS used an adjustable flanged gland seal with multiple rings of packing to prevent air from entering the dryer.

KWS supplied a speed sensor to detect any changes in rotation caused by jams or blockages to protect equipment and processes. When the sensor detects a change in speed, a signal is sent to a control panel to alert the operator of a malfunction. The process may be halted to prevent damage to other conveying or processing equipment.