Olli Aaltonen Consulting

Regenerated cellulose fibers from wood pulp via dissolution

 

 

While working at VTT from late 70's to early 80's our research group did a considerable amount of work developing methods which were supposed to replace the viscose process. 

 

We considered several non-aqueous cellulose solvents and ended up working with two: N-ethylpyridinium chloride (NEPC) and DMSO/Paraformaldehyde. (See the publications list).

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We synthesized NEPC in lab, dissolved cellulose in it and spun filament from the dope into water through commercial spinnerets.

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NEPC is an early representative of a group of non-aqueous cellulose solvents which are now called "ionic liquids".

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The work was publicly financed and did not go past preliminary stage. One of the problems was that NEPC only dissolves cellulose when there is extremely little water in the system. It appeared that it may not be possible to dry the extremely hygroscopic NEPC-salt once it has been dissolved in the aqueous spinning bath. NEPC is non-volatile. Therefore the recirculation of NEPC in an industrial process looked impractical.

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Another problem was that NEPC is solid at room temperature. To lower the melting point and reduce the viscosity of the NEPC/Cellulose-solution we had to dilute the solution with an organic solvent. We used DMF. Having to use two solvent components seemed to make the industrial reuse of the solvent excessively complicated.

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We developed the DMSO / Paraformaldehyde - solvent system for cellulose much further. We had a continuous dissolution reactor pilot-plant at VTT in Otaniemi. We also built a continuous spinning pilot-plant (see picture below). Furthermore, we had a continuous distillation pilot-plant for recovering the DMSO from the spinning bath. The spinning trials were successful and we could produce a sufficient amount of cellulose filament to make yarn and to feed a sock-knitting machine.

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What to do with olive processing waste ?

 

 

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Modern olive oil production uses centrifuges to separate oil from the aqueous olive fruit residue, called Alpeorujo in Spain.

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Roughly 800 kg of Alpeorujo and 200 kg of oil is obtained from one ton olive fruit. Since the world production of olive oil is over 3 million tons, the amount of this residue is huge. In Spain alone the production of Alpeorujo is approx. 6 million tons per year.

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Because of high BOD and COD Alpeorujo cannot be dumped in rivers etc. Therefore it has traditionally been collected in large ponds for evaporation over summer, before being combusted.  Nowadays Alpeorujo is apparently dried with flue gases and then combusted for the production of process heat and electricity for the market. This procedure means that much of water and important nutrients are lost.

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It might be better to return as much as possible of the Alpeorujo to the soil in the olive groves, without removing much water.

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My understanding is that one obstacle for reusing Alpeorujo by returning it to soil is that it contains phenolic compounds which are toxic to micro-organisms. The phenolics are present in Alpeorujo mostly as insoluble esters or bound to cell components by glycosidic linkages. Oleuropein is one of the main phenolics in Alpeorujo. Because of the high content of phenolics Alpeorujo does not biodegrade rapidly.

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A solution could be to remove the phenolics from Alpeorujo and then return the treated sludge back to olive groves.

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I have come up with a procedure whereby the insoluble and bound phenolics would be rendered soluble and removed from the sludge. The procedure involves two steps which are not yet experimentally verified. The treatment involves an agent which must be recovered from the sludge and needs to be completely recycled. The recovery of this agent is already practiced in industrial scale.

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This procedure of rendering Alpeorujo recyclable is on hold. The idea is on the shelf after one representative of an Almazara told me that returning the sludge back to soil is forbidden in Spain. I don't know why it should be forbidden but intend to find out.