Application Example: Feeder Accuracy - A Critical Element in PE Resin Pelletizing and Compounding Processes

Application Example: Polyolefins / Bulk Polymer Compounding: Production of PE pellets LDPE, LLDPE, HDPE


There are a number of well known PE polymerization licenses which are applied in 80% of the world's PE/PP Base Resin production lines. The main licenses are Unipol, Sheripol and Borstar. Examples are shown in the pictures below.

In each case there is a continuous stream of PE/PP powder (fluff) being produced, which must be pelletized. It is in this pelletizing process that Coperion K-Tron feeders play a key role in metering the PE powder being fed into the compounder for the pelletizing process.

Main Component

PE/PP Base Resin Powder


Antioxident, Stabilizers, Fillers, etc.

Typical Production Rate

10,000 - 55,000 kg/hr or 22,000 - 120,000 lb/hr

Basell / Sheripol

Unipol (DOW/Union Carbide)

Higher Feeding Accuracy For Better Product Quality

The Coperion K-Tron Smart Flow Meter (K-SFM) design is very compact: it needs 80% less building height than a comparable LWF. Another advantage is the gentle handling of the product with a continually free path. The lack of moving parts almost eliminates the need for maintenance. At the same time the integrated online auto-tare feature means the K-SFM can be tared without interrupting the product flow and changes in bulk density have no effect on accuracy.The K-SFM operates at pressures of +/- 0.1 bar.

Depending on the formulation, between one and seven loss-in-weight feeders accurately feed the additives at a constant ratio to the main stream of PE powder.

Typical Scope of Supply

Main ingredient:

PE/PP powder or fluff is fed by a Smart Flow Meter 275 or 350 in combination with a rotary valve at rates of 1,000 - 25,000 kg/hr (2,200 - 55,000 lb/hr). The size of the rotary valve depends on the required minimum/maximum feed rates. To avoid pulsation Coperion K-Tron recommends a minimum speed of 30 vanes per minute at the minimum feed rate. A screw conveyor could also be used.


Irganox, calcium carbonate, stabilizers and other additives are fed by loss-in-weight screw feeders such as the K2-ML-T20 or K2-ML-T35 at rates of 1 - 100 kg/hr (2 - 220 lb/hr) depending of the material and feeder.

For free flowing products Coperion K-Tron Premier vacuum sequencing receivers can be used to keep the feeders well supplied. For sticky materials such as Irganox, Tinuvin, or CaCO3 the P Series is the right choice.

Control System

The throughput measured by the Smart Flow Meter provides the master signal for the rest of the feeder line. The loss-in-weight feeders dose the additives in preset ratios based on the master signal (master/slave).

The on-machine Coperion K-Tron Control Module (KCM) combines the function of motor drive and feeder control in a compact package.

In this example the K-Vision operator interface provides a single user interface for up to 16 feeders. The integrated K-Link feature allows for communication with the host DCS system via Modbus (Modicon) RTU, Allen Bradley DF1 or Profibus. Alternatively, a Coperion K-Tron Smart Commander could be used for up to 30 feeders and 8 lines.

Feeding Process

The main component, PE/PP powder, is accurately and gently fed into the pelletizing extruder by a Smart Flow Meter at rates of up to 25,000 kg/hr (55,000 lb/hr). Some licenses, such as Unipol, typically specify loss-in-weight screw feeders for the main component but Coperion K-Tron has been very successful in the use of the Smart Flow Meter for feeding the PE powder instead of using a LWF.

There are a number of well known PE polymerization licenses which are applied in 80% of the world's PE Base Resin production lines.The main licenses are Unipol, Himont and Borstar. Two examples are shown here.


* This process specifies a loss-in-weight feeder but Coperion K-Tron has had success using the Smart Flow Meter instead.

Main Component

PE Base Resin Powder


Antioxidant, Stabilizers, Fillers, etc.

Typical Production Rate:

10,000 - 55,000 kg/hr or 22,000 - 120,000 lb/hr


Automotive, Building, Construction, Appliances, Housewares, Electronics, Furniture, Health, Hygiene, Leisure & Sport, Packaging, Pipes, Textiles

Environmental Conditions:

PE pelletizing processes are typically classified as IP55/NEMA12. The system and all feeders are generally blanketed with N2 (5-10 mbar).

Depending on the license, gas explosion protection may be required, i.e. Zone 1, Temperature class T3 for Europe and Zone 1, Division 2 for USA. In this case standard Coperion K-Tron XP executions must be applied.

Typical Feedrates

Coperion K-Tron Smart Flow Meter (K-SFM) Advantages

Coperion K-Tron Smart Flow Meter (K-SFM)
  • Accuracy of +/- 0.5%
  • Continually free path
  • Gentle handling of bulk material
  • Easy to clean
  • No energy needed to transport bulk material
  • Virtually maintenance free
  • Independent of bulk density
  • Integrated autotare system
  • No moving parts
  • Simple, robust design


Over 100 Coperion K-Tron Smart Flow Meters have been successfully installed in similar process lines worldwide. Our Coperion K-Tron sales staff can provide you with the latest reference list.

Economic Assessment

New PE lines generally include high performance compounders such as those supplied by Coperion, JSW, Farrell, and Kobe Steel. The K-SFM, with its compact design and fast weight measurement, combined with the state-of-the-art algorithms of the SCM, help the customer reduce building height while also reducing the amount of waste material created during start-up and shut-down periods of the production line.

Future Potential

There are a number of PE plants all over the world. This market is still growing by about 3-5% annually. PE is an important base material in more and more processes. Retrofitting and debottlenecking existing PE lines also offer potential for new products.

Typical Producers

BP, Bassell, Exxon, Elf Atochem, Borealis, DSM, Solvay, Fina, ICI, Targor, BASF, Elenac, DOW, and more...

Testing Facilities

Coperion K-Tron has well-equipped testing facilities to test high rates of PE powder and additives. We can handle up to 20 tons per hour of PE powder for accuracy testing. Long term testing is also available since material can be recirculated.