Mass Flow Screw Feeder and Injection Screw Conveyor

General Description

As a member of the global company, Nabaltec Group, Nashtec LLC, is a chemical company focused on producing eco-friendly functional flame-retardant fillers and specialty oxides for use in multiple industrial sectors. Most of the products are used in the plastics and ceramics industries. Highly specialized products have been developed using aluminum hydroxide and aluminum oxide as a basis. One example where these products are used would be flame-retardant fillers used in cables and electronic devices. In case of fire, the chemicals can delay the spread and suppress the development of environmentally harmful and unhealthy smoke and fumes. The specialty oxides are used for various machine and refractory components.

With the global market expanding, Nashtec began construction of a new manufacturing facility in Texas. NHWL Engineering was contracted to design the plant and offer guidance in the selection of equipment to best fit the manufacturing processes. NHWL developed a specification for mechanical conveying equipment and solicited detailed bids from various manufacturers. Based on industry expertise, as well as design and fabrication capabilities, KWS was selected as a partner to fulfill the requirements for the conveying equipment and connecting chutes. The KWS equipment would receive dried filter cake from a paddle dryer which is discharged into a surge hopper. From this hopper, a twin-screw feeder would accurately meter the bulk material into a cantilevered screw conveyor feeding a mill used to reduce the particle size before further processing.

Design Parameters

1. Product Type: Filter cake
2. Material Density: 60 Lbs. per Cubic Foot
3. Capacity: 117 Cubic feet per Hour

KWS Advantages

KWS met every requirement of the NHWL supplied specifications and with experience in similar applications, was able to provide feedback that would enhance the design to offer ideal conveying performance while handling the cohesive filter cake. Because the new conveying equipment was interfacing with the paddle dryer and mill, the parametric 3D models KWS provided were essential for a successful integration with the other material handling components of the feed system.

KWS Special Features

KWS recommended a live bottom mass flow screw feeder as the most efficient way of metering the filter cake from the hopper. The term “mass flow” describes a material flow pattern in which all material in the hopper is drawn down at the same rate, regardless of if the sticky material is against the sidewall or in the center. Mass flow screws meter the filter cake evenly along the entire length of the inlet opening. The twin-screw design prevents material bridging in the hopper. Even discharge allows the mill to maintain an accurate production sequence without surges.

The discharge of the injection screw conveyor bolts directly to the inlet flange of the mill, requiring the screw to be only supported from the drive end, or cantilevered. The cantilevered design eliminates potential maintenance issues and downtime associated with a shaft seal and bearing in the feed zone.

As an additional measure to prevent material from sticking to the screws, internal welds and surfaces were polished to a minimum 150-grit finish. The cantilevered screw conveyor utilized ribbon flights which have space within the flight and around the center pipe to further minimize the potential collection and buildup of the filter cake.