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Plug screw feeder

The plug screw feeder feeds raw materials like chips, saw dust, shavings or straws continuously into a pressurized or liquid filled vessel. The plug screw feeder compresses the raw mateiral and forms a pressure tight plug at the same time as it feeds the raw material in to the pressurized preheater. During the compressing, it removes water, air and pitch from the raw material. The efficiency of the water removal has high impact of the energy consumption in the drying process.

The water pressate can be recycled back to the chip washer or treated to be used in the steam generator to achieve as close to zero effluent as possible from the plant. 

Valmet ADI plug screw feeder are made of heavy duty casted parts to provide long life time and have the best water removal on the market.  It is very easy to operate and needs very little maintenance. Another key feature that distinguish Valmet plug screw feeders to competitor feeders is that the feed screw is journaled/supported by preloaded bearings with zero gap to keep the feed screw in center and avoid metal to metal wear between the screw and the casing (conical screw pipe).

The screw feeder consists of chip inlet, tapered compression zone with draining holes for water and air and a outlet.  It is driven by a frequency controlled AC-motor via a foot mounted gear reducer.

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Valmet Feeding Technology

Is when Valmet optimize  the feeder to customer specific needs, e.g high dewatering, high wear resistance, high capacity, stable feeding or a combination of several factors.

A screw feeder upgraded with Valmet’s feeding technology provides uniform feeding, optimized dewatering and therefore reduced energy consumption. Consequently, this concept is the optimal answer for upgrading our customer's various processes.

Why is choosing correctly so important?

Different processes have different requirements. In some processes dewatering is the most important parameter, while in other applications very uniform feeding is essential. The main factors that are influenced by choice can be summarized as follows:

  • Dewatering
  • Capacity
  • Energy consumption
  • Feeding stability
  • Lifetime

Benefits

One or more benefits can be attained depending on the application:

  • Improved dewatering with
    • Less steam consumption in preheater
    • Lower energy consumption in the dryer
  • More uniform and stable feeding of chips , which stabilizes the load on the refiner and segment life
  • Longer lifetime
  • Reduced motor load and less energy consumption.

Customized installations

Depending on the specific process, Valmet Feeding Technology is customized to fit each function by careful choice of screw type, screw compression, rear screw pipe, screw pipe, plug pipe and wear sleeve.

Screw Rear screw pipe Screw pipe Plug pipe Wear sleeve
Standard (LL) Staight bars Straight bars (LL) Standard Slotted
XP Screw Spiral bars Spiral bars (LL) Dewatering plug pipe No holes (LL)
Compression rate 1.6:1 - 4:1       Holes 1 section (LL)
        Holes 2 sections (LL)

(LL) Available in long lasting material

Screws are available in two main designs

Standard screw

The standard screw with a hard faced repairable screw is available in many different designs.

Long Lasting material

The Feed Screw LL is cast and heat treated to a very durable material. This type of screw is suitable for applications where maximized lifetime is required. This screw is not repairable. Price and wear resistance are its benefits – as much as three times longer lifetime. The energy consumption has also been found to decrease by as much as 30% in some cases.

Compression

The screws are available in various compressions (volume at inlet/volume at outlet). High screw compression produces higher capacity and dewatering, but at the same time requires greater torque, which can cause increased wear.

Rear screw pipe and screw pipe

The screw pipes is adapted to the new screw type and is available in two main designs.

Standard

A standard screw pipe with straight bars.

Spiral bars

Depending on process requirements, running pulp or chips with spiral bars reduces friction in the compression zone. Decreased friction produces lower energy consumption and more uniform feed.The screw pipe is also available in Long Lasting material.

Plug pipe

The plug pipe is available in two designs, the choice of design depending on process requirements.

Standard

Standard design, to create an effective plug.

Dewatering Plug Pipe

This product extends the dewatering zone and therefore achieves better dewatering. A drain hood is installed to collect the water squeezed out from the plug pipe. The dewatering can be increased by as much as 30%. The plug pipe is equipped with replaceable wear sleeves

Wear sleeve

Wear sleeves are used in connection with the Dewatering Pulg Pipe. The choice of sleeve depends on the process conditions.The wear sleeves is also available in Long Lasting material except the slotted version.

Material available for download

Our expertise is at your service

Our focus is to bring your performance forward utilizing our extensive experience and in-depth knowledge of pulp process technology. Get in touch with our experts through your local Valmet office, or the link below.