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QLK5-1999-01071
FIBERVIVAL - Upgrading recycled fibres by appropriate treatments during the stock preparation |
| Contract No: | QLK5-1999-01071 |
| Source: | First Annual Progress Report 2001 |
| Second Annual Progress Report 2002 |
The objective of the FIBREVIVAL project is to restore the properties of recycled fibre by appropriate treatments and to understand the mechanism of restoration (and degradation) in order to propose a solution for industrial papermakers.
Several methods of characterisations have been carried out. These include:
Several types of treatments have been applied to try to restore fibre and or pulp properties. The various treatments applied onto fibres were:
One of the most promising treatments was the decrilling treatment (removal of crills considered as dead fines without any ability to form links with fibres and to contribute to an enhancement of the fibrous network) followed by a refining step. Moreover, by decrilling, a part of the chemical contamination can be removed. Nevertheless, even if this treatment is beneficial to pulp properties, it has no effect on fibre properties because it consists only in a removal of cellulosic materials.
Laboratory trials (and results) are necessary to find a tendency in the improvement of fibre/ pulp properties but cannot be considered as sufficient. It is well known that large differences can be observed between laboratory treatments and industrial treatments. Indeed, industrial treatments are performed in a less gentle way than in laboratory treatments. Various effects of pumps, of recirculation, of residence time, of storage chest, etc.., which cannot be considered in laboratory treatments also have to be considered. Hence, there ia a need to confirm the effects obtained at laboratory scale at semi-industrial scale, where the treatments are applied at larger scale in conditions very close to those found in industrial recycling lines.
In order to compare the results gained in the previous work, the same raw materials have been used for the trials at pilot plant scale. This raw material is a bale of mixed waste paper. This raw material comes from Germany and corresponds to a mixture of old corrugated cardboards, magazines, newspapers, folding boxes, etc.For reasons of homogeneity of the raw materials to be treated on the pilot plant, the bales have been pulled into pieces with a shredder and then perfectly mixed. This was used in experiments aimed at improving the mechanical properties of pulps made from recycled fibres (RF) by several types of reactivation methods (fractionation, physico-chemical, biological and mechanical treatments and decrilling). This work was made at semi-industrial scale (pilot plant facilities) and is essentially based on the most promising results gained at laboratory scale.
During the fifth partner meeting held in Talence (France, 15 March 2002) all partners presented their results concerning sample pulps treated by various methods (mechanical, physico-cheniical, biological and decrilling treatments) which were characterised in terms of fibre morphology, mechanical properties and topochemistry-ultrastructure.
The results of pilot plant scale trials and characterisation have shown that:
This work confirms the possibility of optimising the mechanical properties of pulp and help in the selection of the most promising treatment procedures for industrial scale testing in order to restore the strength potential of recycled fibres. This work is of benefit both for the paper recycling mills and for equipment suppliers to the recycling industry.
Future activities include validation of the laboratory and pilot plant results in an industrial mill using a selection of the most appropriate treatment procedures
Introduction
The various political measures (mandatory and voluntary recycling quotas, ecotaxes, collection promotion, information of people ... ), taken in the interest of sustainable development as well as reflecting public pressure for environemtnal pressure, has resulted in the recycling of vast amounts of post-consumer wastepaper. Annually, in the EU, paper mills produce 75 million tons of paper, for the manufacturing of which 34 million tons of post-consumer waste paper are used. One third of this is used to carry information (newsprint, etc), while 2/3 is packaging paper. Waste paper recycling eliminates the use of 50 to 60 million ton/year of wood and reduces the burden of waste disposal sites by around 165 million M3 per annum.
Increase of the renewable raw material stocks (woods) and further reduction in the burden place on landfill sites requires an increase in the waste paper utilisation rate to 75 % of the EU paper production, which would mean the processing of 17 million tons more waste paper annually. The European paper industry has reached this rate in the case of CBRM (corrugated board raw materials), it was made possible mainly due to the ease of collection of OCC (old corrugated containers), which originated from the CCM (corrugated case materials).
The ever-increasing OCC recycling causes a reduction of in the load-bearing capacity of CCM's, because the recycled fibres are returned to the paper producer several times. Recycling also leads to concentrates in the paper mills made up of the solid and soluble components of the recycled card (plastics, printing inks, adhesives, etc), which get there with the waste paper. Further increase of waste paper recycling is hampered by various harmful effects (described below) which, though well known, had little effect at low waste paper recycling rates, and so were not quantified.
Objectives
The main objectives of this project are:
It is well known that during their lifetime, cellulosic fibres are submitted to chemical, physico-chemical and mechanical treatments. These treatments are cooking for the production of virgin pulps, bleaching for bleached pulps, defibering and refining for the production of mechanical pulps, beating and refining for the production of paper. These treatments, necessary for the production of pulps and papers, are detrimental to the fibre structure if applied without precautions. The fibre ultrastructure is formed with cellulose microfibrils arranged in amorphous and crystalline areas embedded with lignin and hemicelluloses as matrix components. The amorphous areas are considered as dislocation areas in the structure of the fibres: they are weak points. These weak points are inherent to the fibre structure. With the various treatments (chemical, physico- chemical and mechanical), the dislocation areas are transformed into fracture areas as a result of an increase in amorphous areas to the detriment of crystalline areas. Consequently the fibres are weakened and more likely to break when submitted to solicitations.
Recycler papermakers use recovered fibres for the production of papers and boards. These fibres consist of a mixture of pulps from various origins: mechanical pulps, chemical pulps (unbleached and bleached)... Fibres had already suffered from the various treatments of the first cycle. That explains that recovered fibres are weaker than virgin pulps and that the resulting papers have much less mechanical strength than the papers made from virgin pulps.
This project, has two major objectives, first to find solutions for maintaining the mechanical potential of fibres, in terms of mechanical strength, and second to be able to rehabilitate these recovered fibres in order to restore and to regain the part of mechanical properties they lost. This project is essentially devoted to the raw materials used in brown gade for the production of corrugating papers.
Another objective is also to collect fundamental data about the morphological, ultrastructural and topochemical parameters of the various raw materials and fibres. This will help identify and characteris the effects of the treatments in relation to mechanical properties as well as precisely determine the differences between the properties of virgin fibres and recycled fibres. Indeed, before treating the fibres, it is essential to know more about the raw materials used for papers and boards production from recovered fibres and to quantify along the process (recycling line) the step (or steps) where a part of the mechanical strength of the fibres has been affected.
Activities
This project aims at developing, improving and above all understanding the treatments to be applied on recycled fibres to restore their initial mechanical strength in order to be able to produce papers and boards with good mechanical strength in the brown grade field. In order to reach the objectives of the study, the project has been divided into several workpackages (WP). Workpackage 1 (WP1) covewrs the procedures to be used. Workpackage 2 (WP2) concerns the strength properties of fibres along a recycling line of two or three paper mills in order to evaluate the most detrimental step for the fibre strength. The assessment will been carried out by sampling pulps at the inlet and the outlet. In additions rejects at each step of the recycling lines have also been investigated. In other words, each time, fibres are submitted to a device (refiner, cleaner, screener, pulper, fractionator, low or high speed disperser, thickener ... ) a characterisation and a quantification of the effects of the fibre structure will be performed according to the procedure described in WPl.
Progress
WP2: Fibre properties assessment on recycling papermill In this workpackage, several properties of fibres and pulps have been followed and measured along the recycling lines of industrial mills in order to quantify the most detrimental devices in pulp and fibre strength. An important objective is also to quantify and to understand the changes occurring inside fibres. This aspect is investigated by electron microscopy of fibres at various stages of the recycling line. Particular attention is given to the internal changes occurring in the fibre ultrastructure and affecting the cohesion between microfibrils.
The work covers an analysis of two commercial recycling plants producing pulp for container board (kraft liner, fluting and test liner). These plants are located in Dublin, Ireland and Facture, France. The task involved sampling through each of the recycled operations, followed by physical testing of the pulp (CTP and Smurfit) and microscopy (CERMAV). Mechanical properties have been determined on handsheets prepared in the laboratory. Fibre dimension analyses have been at laboratory scale with a fibre analyser. Ultrastructural data observed by Transmission Electron Microscopy (TEM) provides parameters related to internal characteristics of fibre wall Organisation. The physical properties generated from the series of samples have been compared on a stage to stage basis to determine the effects of commercial process on pulp characteristics. The effects seen are quantifiable and, in their cumulative effect, large.
Discussion-Conclusion
In view of getting a comprehensive characterisation of pulps and fibres (modification, change, degradation ... ) along an industrial recycling line, several aspects have been studied. Those include the determination of fibre dimensions and distribution, mechanical properties of pulps and papers, physicochemical analyses, and ultra-structuril characterisation. The results obtained on industrial pulp samples reveal that transformation occurs inside fibres in the stock preparation. Conventional characterisations of pulp and fibre (dimension, drainability, hydration, mechanical properties) cannot explain what happens inside fibres. Only tendencies can be seen.
This workpackage has been of importance for defining both the magnitude of quality improvement required and the relative ineffectiveness of current processing systems in achieving it. This reflects the amount of damage the fibres have sustained in multiple recyclings, the mixture of fibre types present and the level of non- fibrous material (some sources contained in excess of 10 % ash. Wile microscopy indicates a very high degree of heterogeneity among fibres as well as much non-fibrous content), the goal of regenerating softwood kraft quality is impossible.
Work completed so far indicates some methods can achieve limited improvement (kneading and washing). Physical testing along the fibrelines of two recycling mills (Smurfit mills at Facture, France and Dublin, Ireland) shows a slight gain in strength, though at the end of the process strength which is only 30-40 % of virgin unbleached softwood kraft pulp. Pulp drainage rate, another important fibre quality, decreases throughout the Facture system (and in several other Central European systems compared as references), but increases through the Dublin system.
Future action
Methodology used and improved for fibre characterisation in the frame of WPI and WP2 will be used for the other WP. Experiences between conventional assessment of fibre and pulp properties (in terms of papernakers' point of view) and innovative techniques developed are the conclusions of work to date. Fibre changes are identified and base on this result, improvement or degradation of fibre properties in the rest of the project will be more easily quantifiable.
The results from WP2 will have some effect on the planning for the strength improvement testing in the next phase. First, the focus on fibre types in most need of improvement becomes central. Second, low intensity refining and washing are indicated as the mechanical techniques with a likely chance of success in producing limited revival of recycled fibre.
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Updated
by CPL Press:
03/07/2007
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