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Author:Hanhikoski, Saara
Title:High yield nucleophile cooking of wood chips
Korkeasaantoinen puuhakkeen nukleofiilikeitto
Publication type:Master's thesis
Publication year:2013
Pages:100 s. + liitt. 9      Language:   eng
Department/School:Puunjalostustekniikan laitos
Main subject:Sellutekniikka   (P3002.)
Supervisor:Vuorinen, Tapani
Instructor:Varhimo, Antero ; Warsta, Elina
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201310167715
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  2325   | Archive
Keywords:nucleophile
neutral sulphite
yield
sulphite pulping
nukleofiili
neutraali sulfiitti
saanto
sulfiittikeitto
Abstract (eng):The objective of Thesis was to study the effect of the sulphite cooking at pH 6-8 on the total pulp yield.
The idea was that in neutral cooking conditions strong nucleophiles like sulphite ion are able to dissolve lignin while the carbohydrates are preserved in a high extent.
In neutral conditions the acid-base- catalyzed degradation of carbohydrates is significantly slowed down, which leads to a high pulping yield.

The cooking experiments produced high kappa pulps with high yield.
The target kappa number 50 was reached by cooking pine chips at 180°C during 240 minutes using 30% Na2SO3-charge and 0.1% AQ-charge, and the initial pH 8.
Lower kappa number was possible to obtain by using higher chemical charge, higher temperature or longer cooking time.
The advantages of these pulps are the high cooking yield, which was 55% at kappa number 50, and also the high brightness, over 60% ISO.
However, the pulp viscosity was decreased considerably during the cooking.
The pulp cooked to kappa number 59 was delignified further with one and multiple oxygen delignification stages.
This decreased the brightness of the pulp under 40% ISO, but the yield and the viscosity were maintained.
The bleaching sequences tested DEDED, DEpDP, and DED resulted in pulps with brightness of 89% ISO and 87% ISO.
The disadvantage of the bleaching was the high chemical consumption, though the pulp properties were maintained.
The total yields of the bleached pulps calculated on wood were between 48-53%.

The chemical composition analysis made from the selected pulp samples confirmed that the yield increase was mainly due to high retention of glucomannans.
The sulphonic acid groups content measured from the cooked pulps were 250-300 mmol/kg, which indicates that the sulphonic acid groups are also attached to the carbohydrates.
However, further experiments are needed to confirm this.
Also deeper analyses are needed to find out the application possibilities of the fibres and the dissolved lignin fragments relative to the possible neutral sulphite biorefinery concept.
Abstract (fin):Diplomityössä tutkittiin neutraaleissa olosuhteissa, pH:ssa 6-8, tehdyn sulfiittikeiton vaikutusta sellun saantoon.
Oletuksena on, että neutraaleissa keitto-olosuhteissa vahvat nukleofiilit kuten sulfiitti-ioni pystyvät reagoimaan ligniinin kanssa ilman hiilihydraattien merkittävää pilkkoutumista.
Kun hiilihydraatteja pilkkovat happo- ja alkali-katalysoidut reaktiot ovat hyvin hitaita, saavutetaan huomattava keiton saannon lisäys.

Laboratoriokokeissa keitettiin sulfiittimenetelmällä massaa, jolla oli korkea kappaluku mutta myös korkea saanto.
Tavoitekappaluku 50 saavutettiin keittämällä mäntyhaketta 180°C lämpötilassa 240 minuuttia lähtö pH:n ollessa 8, ja kemikaaliannosten ollessa 30% Na2SO3 ja 0.1% AQ.
Matalampi kappaluku oli mahdollista saavuttaa vain lisäämällä kemikaaliannosta, nostamalla keittolämpötilaa tai -aikaa.
Kappaluvun ollessa 50 keiton saanto oli 55% puusta laskettuna ja massan ISO-vaaleus yli 60%, mutta massan viskositeetti oli laskenut huomattavasti.
Kappalukuun 59 keitetty suurempi massaerä jatko-delignifioitiin yksi- ja monivaiheisella happivaiheella.
Happidelignifiointi tummensi massan alle 40% ISO- vaaleuteen, kun taas massan kokonaissaanto ja viskositeetti säilyivät lähes muuttumattomina.
Happidelignifioitu massa valkaistiin DEDED, DEpDP ja DED sekvensseillä vaaleuteen 89% ISO ja 87% ISO.
Valkaisun kemikaalikulutus oli huomattavan korkea, mutta massan kokonaissaanto puusta laskettuna oli edelleen 48-53%.

Valituista massoista tehdyt ligniini- ja hiilihydraattianalyysit osoittivat korkean saannon johtuvan korkeasta glucomannaanipitoisuudesta.
Keitetyistä massoista analysoitiin myös sulfonihapporyhmien määrä, joka oli 250-300 mmol/kg.
Tämän tuloksen perusteella voidaan olettaa sulfonihapporyhmien olevan kiinnittyneenä myös hiilihydraatteihin, mutta tarkempia analyysejä tarvitaan asian varmistamiseksi.
Lisäanalyysejä tarvitaan myös selvittämään kuitujen ja liuenneiden komponenttien mahdollisia uusia sovelluskohteita tulevaisuuden neutraalisulfiittibiojalostamokonseptia ajatellen.
ED:2013-12-02
INSSI record number: 48099
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