Unique melt filtration system shows advantages over traditional backflush systems

  • Fundamentally new design concept
  • Less melt loss than with traditional backflush systems
  • Max. pressure of 350 bar, max. temperature of 320 °C, up to 1,500 kg/h

Nordson Corporation announced that a new melt filtration system for recycling highly contaminated plastics provides higher productivity than comparable systems on the market while maintaining constant melt pressure. The company will introduce the system at K 2016.

Less melt loss than with traditional backflush systems

Tradenamed BKG HiCon R-Type 250, the filtration system transforms highly contaminated polyolefin or styrenic plastics into clean, high-quality material and exhibits less melt loss than with traditional backflush systems for highly contaminated plastics.

Nordson BKG HiCon R-Type 250 filtration system

Unique design concept

The central concept of the HiCon R-Type 250 system is unique. It involves the use of a cylindrical “separating head” with knives arranged on its surface in a helical pattern designed to move contaminant particles forward as the head rotates. Enclosing the head is a stationary filter element called a “strainer tube.” When contaminated melt from an entry port flows into the cylindrical space between the rotating head and the strainer tube, the knives capture the contaminant while the contaminant-free melt moves through the strainer into flow channels that lead to an exit port. At the same time, the rotating head turns a screw which guides the contaminated material through cooling sections and finally to where it is discharged into collecting bins.

Nordson melt filtration system

Shown from right to left are the drive mechanism, the cylindrical separating head, and the discharge screw. A stationary filter element called the strainer tube surrounds the separating head. Green arrows indicate the main polymer flow as melt enters the HiCon™ R-type system, moves into the space between the separating head and the strainer tube, and passes through the strainer into flow channels that lead to a port for the exit of decontaminated melt. Red arrows indicate contaminant that is driven forward to the discharge screw by the helically arranged knives on the separating head.

Max. pressure of 350 bar, max. temperature of 320 °C, up to 1,500 kg/h

A powerful drive actuates the separation head / discharge-screw assembly. The HiCon R-Type 250 system operates at a maximum pressure of 350 bar and maximum temperature of 320 °C. Throughput can range from 500 to 1,500 kg/h. The rate depends on polymer viscosity, filtration fineness, levels of contamination, and other factors. As it exits the system, filtered polymer is maintained at a constant pressure, ensuring uniform processing downstream.

Key to efficiency: design of steel strainer tubes

One key to the efficiency with which the system removes contaminants is the design of the steel strainer tubes, which are available with micro-holes ranging from 120 to 750 microns. The holes are conical in shape, permitting passage of molten polymer while preventing blockage by contaminant. This design and the symmetrically positioned knives in the drum contribute to the long working life of the tube before it needs to be replaced. Once cleaned, moreover, the tube can be reused.

Nordson melt filtration system3

Replacing a strainer tube is facilitated by a built-in swiveling arm for removing the strainer tube housing, and by a hand-operated hydraulic device for disassembling it. To ensure uninterrupted production, it is possible to operate two HiCon R-type 250 systems in parallel.

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