RECYCLING: Filtration System Billed As ‘Fundamentally New’

Less melt loss reportedly experienced compared with typical backflush systems.

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A new melt filtration system for recycling highly contaminated plastics is said to greater productivity than comparable machines on the market while maintaining constant melt pressure and product consistency. The BKG HiCon R-Type 250 from Nordson Polymer Processing. reportedly 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. The unit will debut at K 2016 this month.

 Nordson says the central concept of the 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.

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 608 F (320 C). Throughput can range from 500 to 1500 kg/hr (1102 to 3307 lb). 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.

One key to the efficiency with which the device 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.

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 reportedly possible to operate two HiCon R-type 250 systems in parallel.