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.
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.
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:
One or more benefits can be attained depending on the application:
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)|
The standard screw with a hard faced repairable screw is available in many different designs.
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.
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.
The screw pipes is adapted to the new screw type and is available in two main designs.
A standard screw pipe with straight 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.
The plug pipe is available in two designs, the choice of design depending on process requirements.
Standard design, to create an effective plug.
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 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
|Valmet Feeding Technology|
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