FR2667082A1 - Process for scutching plants containing bast fibres, especially flax - Google Patents

Abstract

Process for scutching plants containing bast fibres, especially flax, characterised in that it consists in throwing solid particles violently onto the material so as to remove the non fibrous parts of the plant treated. These particles are advantageously solid particles which have the property of subliming rapidly after contact with the material to be treated, for example frozen particles of the solid carbon dioxide type.

Description

After a vegetative cycle of around a hundred days, the flax stems are torn off by specific machines and placed on the ground to undergo biological degradation by soil micro-organisms. These agents attack pectic cements and allow, by their action, the separation of fibers from other parts of the stem. After this action, the flax is picked up, pressed and stored before undergoing a second transformation, which consists in extracting the fibers contained at the periphery of the stems. This second operation is called "scutching". It consists in grinding the stems by passing them through grooved rollers, then in peeling the stems, that is to say scraping the stems using a steel blade, to make fall all the particles which still remain attached to the fibers after the grinding action.

Other fibrous materials are treated in a similar or similar manner. This is particularly the case for hemp which undergoes a succession of grinding, or else ramie or kenaf.

The scutching of flax is currently carried out by industrial installations which process flax organized in "swaths", constituted by the aligned rods, parallel to each other in a direction perpendicular to the direction of advancement of the material.

The flax swath is pinched in the middle by two belts which ensure its movement. First crushed over its entire length, the tablecloth is then peeled under the action of steel blades, fixed on two drums rotating in opposite directions on either side of the swath, which scrape the stems by treating each pass a swath length of about five meters. This blade works from the nip to the end. This extremely vigorous, alternative action breaks the fibers in many places, which leads to recovering not only the plant waste from the stems, called "anas", but also short pieces of fiber, called tows. reinforced when the swath presents itself in an irregular sheet, with bundles, extra thicknesses, which requires rapid speed adjustments.

The steel blades undergo, by this continuous friction, rapid wear: the replacement of these blades requires costly stops in labor and parts.

The rotation of the drums causes significant air vortices. To allow good evacuation of shives and tows, powerful suction devices are placed under the drums which impose a downward direction of air circulation so as to entrain all the waste. These powerful devices consume large amounts of energy and also require installations to measure them to receive and slow down the quantities of air set in motion in order to be able to recover and sort out the different transported products, shives, dust, tows.

In addition, the fields of culture are often polluted by various waste, in particular by pieces of polypropylene, which after having been rolled up in the heart of the windrows, are found in the tows. These plastics, which are found in fabrics, make the tows unfit for marketing.

The process which is described here makes it possible to eliminate all these difficulties: irregular action, breaking of the fibers with creation of tows, pollution, energy consumption by pneumatic transport, etc ...

This process of exchanging plants with bast fibers arranged at the periphery of the stems under the bark, in particular flax, hemp, or even ramie and kenaf, consists in projecting violently onto the material solid particles so as to remove the non-fibrous parts of the treated plant. These parts, detached from the fibers under the action of the impact of solid particles, fall by gravity onto conveyor belts which entrain the materials collected towards sorting devices.

The process allows a very localized action. The dressing is carried out as for conventional tillers, starting with the part near the nip to finish on the ends: according to a first variant, leaching begins first on the ends of the stems, to gradually go up towards the area of pinching Finally, more advantageously, the mixing begins in several places by multiplying the devices for projecting solid particles in order to reduce the processing times of the material. The solid particles penetrate the thickness of the sheet to remove the woody particles. The action is much less brutal, and the process does not create tows.However, it easily involves foreign bodies, stones, polypropylene and earth.

By flush, the process no longer induces wear and allows work without stopping maintenance. in fact, the projection devices are easily replaced by others without requiring the shutdown of the industry device.
These particles according to a first embodiment consist of grains of sand, steel balls, etc. As a variant, very advantageously, the process uses solid particles which have the property of sublimating after the impact on the material , for example frozen particles and may consist of dry ice granules. Thus, the waste and the shives are not polluted by any foreign bodies that we would have to recycle.

The projection of these particles is advantageously carried out pneumatically, for example an air jet, the pressure of which can be adjusted in order to be able to regulate the power of the impact of the granules.

Claims (6)

1. Method for exchanging plants with bast fibers, in particular flax, characterized in that it consists in projecting violently onto the material solid particles so as to remove the non-fibrous parts of the treated plant 2. Method according to claim 1, characterized in that it consists in using solid particles having the property of sublimating quickly after contact with the material to be treated, for example frozen particles. 3. Method according to claims 1 and 2, characterized in that the solid particles consist of pieces of dry ice. 4. Method according to claims 1, 2 and 3, characterized in that it consists in first cutting the end of the material and then going up towards the nip. 5. Method according to claim 1,2 and 3, characterized in that it consists in exchanging several places of the rod at the same time by having several devices for projecting solid particles. 6. Method according to any one of claims 1 to 5, characterized in that it consists in transporting and projecting the solid particles pneumatically.