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HQ chipper
Twin chipperChips in hand

Chipping systems

The heart of the woodroom

The challenge

Forest product companies face the challenge of improving the efficiency and productivity of their wood processing operations to reduce operating costs, save raw materials, and reduce energy consumption. The challenge is to produce very high quality chips while minimizing wood losses (fines and pins).

The solution

ANDRITZ offers a range of chipping systems that can accommodate the specific requirements and layout of a customer’s wood processing operation. The chipper is the most important piece of equipment in the woodroom or woodyard because it either produces high quality chips or destroys expensive raw materials.

ANDRITZ designs, manufactures, and delivers chippers as part of a complete wood processing equipment portfolio or as a single machine delivery. By optimizing the cutting geometry, the cutting speed, and other parameters affecting the chipping process, ANDRITZ chippers are designed to produce very high quality chips at high capacity, even from small diameter wood.

There is a tremendous number of variations in the appearance and characteristics of logs which have an effect on the chipping process. ANDRITZ has supplied over 1,100 chippers around the world and has built a depth of expertise. As the leader in chipping technology today, ANDRITZ has delivered chipping systems that produce the highest chip quality at the largest throughput (world record is 500 m3 sub/every effective hour for a 20-hour period).

The basic prerequisite for producing very high and uniform chip quality is that each log will be correctly oriented in relation to the chipper disc during chipping. Once the first knife hits the log, the log must not rotate during the chipping sequence, but the log flow has to remain stable. High capacities are achieved by uniform, constant, and simultaneous chipping of several logs at the same time across the whole width of the bed knife.

ANDRITZ first developed the gravity-fed HQ-chipper by tilting its shaft a little bit downwards and by optimizing its unique chipping geometry. This proved to be a major success milestone.

By tilting the shaft further, ANDRITZ created the horizontally-fed HHQ-chipper, which produced chip quality far superior to anything seen before. This became the second success milestone.

Looking at chipper orders over the past five years, ANDRITZ has delivered 55 chippers. The majority (48 units) have been horizontally-fed HHQ-chippers. One gravity-fed HQ-chipper and six older type chippers were also delivered.

Horizontally-fed HHQ-chipper

The first HHQ-chipper was delivered to Metsä-Botnia’s Joutseno Mill in Finland in 2001. The biggest chipper in the world – the EXL-18I type with 18 knives – was delivered to Veracel Celulose S.A. in Brazil in 2009.

Logs are fed directly to the HHQ-chipper through a large horizontal spout by a chain conveyor at a controlled speed. The horizontal infeed keeps the chipping process stable by holding the logs in the same position relative to the chipper disc during the chipping process. This minimizes the number of oversized and overthick chips, and tightens the chip size distribution. Horizontal infeed also minimizes log impacts, and therefore log breakage, prior to the chipper. The large spout accommodates infeed of crooked wood as well.

The HHQ-chipper with horizontal infeed is best suited for long logs. However, it works with short logs as well because the infeed chain conveyor can orient the short logs during chipping. The improved cutting geometry and optimized cutting speed produce thinner and more rectangular shaped chips, which are well suited to today’s cooking or refining processes.

Low maintenance requirements, easily changeable wear parts, and ergonomic and compact design all contribute to the total economy of the HHQ-chipper.

The chips are side-discharged to a screw hopper placed above the floor level. The gentle discharge reduces chip damage as well as the amount of fines and pins produced. Tests show that the chips are of such high quality that they can be compared with screened chips.

The horizontally-fed HHQ-chipper is designed to produce superior quality chips at high capacity levels and it features:

  • Very high and uniform chip quality due to unique chipping geometry and cutting speed
    • saving raw material
    • producing better pulp quality
    • increasing production and yield
    • lowering chemical consumption in the pulp mill
    • lowering cooking temperatures in the pulp mill
  • High capacity by simultaneous chipping of several logs at the same time across the whole width of the bed knife
  • Minimal oversize and overthick chips
  • Very low generation of small fractions, pins and fines
  • Reduced chip damage
  • Reliable operation

Gravity-fed HQ-chipper

The HQ-chipper is designed to produce the highest quality chips at high capacity from today's varying wood supply. The first HQ-chipper was delivered to Metsä-Botnia’s Kaskinen Mill in Finland in 1989, and the technology has been improved over the years.

The HQ-chipper design combines proven chipping technology with the latest research for today's small diameter pulpwood to produce high quality chips and high capacity. The unique chipping geometry and optimized cutting speed of the HQ-chipper with an inclined shaft produces high quality chips from logs up to 6 m long.

The large spout allows simultaneous chipping of several small diameter logs while maintaining stable position of the logs during chipping. The improved geometry yields thinner, rectangular shaped chips well suited to modern cooking or refining processes.

The chips are side-discharged to a screw hopper placed above the floor level. The gentle discharge reduces chip damage and the amount of fines and pins produced. Tests show that the chips are of such high quality that they can be compared with screened chips.

Low maintenance requirements, easily changeable wear parts, and ergonomic and compact design all contribute to the total economy of the HHQ-chipper.

The HQ-chipper features

  • Very high and uniform chip quality due to unique chipping geometry and cutting speed
    • saving raw material
    • producing better pulp quality
    • increasing production and yield
    • lowering chemical consumption in the pulp mill
    • lowering cooking temperatures in the pulp mill
  • High capacity by simultaneous chipping of several logs at the same time across the whole width of the bed knife
  • Minimal oversize and overthick chips
  • Very low generation of small fractions, pins and fines
  • Reduced chip damage
  • Reliable operation

Horizontally-fed TwinChipper

The TwinChipper is ideal for longwood chipping. The horizontal wood infeed, coupled with integrated breakage processing via a specially designed secondary drop-feed spout, result in improved chip quality and increased capacity.

The TwinChipper features

  • Reduced chip damage
  • Horizontal feed of tree-length wood
  • Minimal oversize and overthick chips
  • Highest possible chip quality and yield from breakage
  • Low pins and fines generation
  • Reduced chip damage

Longwood processing requires horizontal infeed to the chipper. Small pieces of wood sometimes broken off the stem during processing can interrupt the throughput of the chipper and the chip quality produced from the longer stems. The breakage separation capability of the TwinChipper provides an undisturbed flow of logs to the main spout, which increases the capacity of the chipper and improves the chip quality.

In addition to the large, undershaft spout, the TwinChipper is equipped with a secondary drop-feed spout to extract the highest possible chip quality and yield from the broken material.

Longwood is fed to the TwinChipper by a conveyor. The horizontal spout is at the correct angle to the chipper disc to ensure optimum chipping. Breakage is separated from the main feed line, collected in a separate conveyor, and fed to the chipper via the breakage spout located above the main chipper spout.

The large disc diameter enables the use of a large spout opening for crooked wood, while the reduced cutting speed minimizes the amount of fines and pins. The side discharge reduces chip damage caused by the blowing wings of the chipper disc.

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