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Author:Savela, Miikka-Jaakko
Title:Environmental impact study of softwood prehydrolysis kraft pulping and bleaching
Esihydrolysoidun havusellun valmistuksen ja valkaisun ympäristövaikutusten tarkastelu
Publication type:Master's thesis
Publication year:2013
Pages:vii + 73 s. + liitt. 13      Language:   eng
Department/School:Puunjalostustekniikan laitos
Main subject:Sellutekniikka   (P3002)
Supervisor:Dahl, Olli
Instructor:Vehmaa, Janne ; Rauhala, Tiina ; Piira, Jussi
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201310167718
OEVS:
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Location:P1 Ark Aalto  2284   | Archive
Keywords:autohydrolysis
prehydrolysis
bleaching
TCF
ECF
COD
AOX
autohydrolyysi
esihydrolyysi
valkaisu
Abstract (eng):The objective of this Master's Thesis was to produce prehydrolysis-kraft pulp (dissolving grade pulp) and examine different bleaching sequences for the dissolving grade pulp produced as well as to study the environmental impact of the bleaching.
Hardwoods have been recently studied for the dissolving grade pulp production but the study of softwoods is lately mainly focused on paper grade pulp production.

The literature review focused on different prehydrolysis methods and their properties, the bleaching of pulp and the environmental impact of bleaching.
Also the possibility to convert conventional pulp mill into forest biorefinery was discussed.

The experimental part consisted of prehydrolysis-kraft pulping and subsequent bleaching of the produced dissolving grade pulp with three different bleaching sequences.
The main objective was to produce high purity dissolving grade pulp which achieves the strict environmental standards.

The only bleaching sequence to achieve the targets appointed was the conventional four-phase ECF bleaching sequence.
The bleaching chemical consumption however was rather high with each bleaching stage.
The environmental impact of bleaching showed similar results compared to conventional kraft pulp bleaching in laboratory scale.
The production of dissolving grade pulp from softwood is possible and economically profitable if the market price for dissolving grade pulp is sufficient and if reasonable amount of valuable side products can be further produced from the hydrolysate.
Abstract (fin):Tämän diplomityön tavoitteena oli valmistaa esihydrolysoitua sulfaattisellua (liukosellu) havupuusta ja tutkia valmistetun massan valkaisua eri valkaisusekvensseillä.
Myös valkaisun ympäristövaikutuksia tutkittiin.
Viime aikoina lehtipuu on ollut esihydrolysoidun sellun valmistuksen pääasiallisena tutkimuskohteena, kun taas havupuuta on tutkittu enemmän perinteisen sulfaattisellun valmistuksessa.

Kirjallisuusosassa tutkitaan eri esihydrolyysimenetelmiä sekä niiden ominaisuuksia, sellun valkaisua eri kemikaaleilla, sekä valkaisun ympäristövaikutuksia.
Myös perinteisen sellutehtaan muuntamista tulevaisuuden biojalostamoksi tarkastellaan.

Kokeellisessa osassa valmistetaan esihydrolysoitua havupuusellua ja valkaistaan valmistettu sellu kolmella erilaisella valkaisusekvenssillä.
Tavoitteena on valmistaa esihydrolysoitua sellua, joka saavuttaa halutut laatuvaatimukset ja täyttää vaaditut ympäristökriteerit.

Ainoa valkaisusekvenssi, joka saavutti laatuvaatimukset, oli neljävaiheinen perinteinen ECF-sekvenssi.
Valkaisukemikaalien kulutus oli varsin korkea jokaisessa valkaisuvaiheessa.
Valkaisun ympäristövaikutukset esihydrolysoidulla sellulla olivat samalla tasolla verrattuna tavallisen kraft-prosessin valkaisuun.
Havupuusta valmistettava liukosellu on taloudellisesti järkevää valmistaa vain jos liukosellun hinta on tarpeeksi korkea ja jos sivutuotteina saatavat arvokkaat orgaaniset yhdisteet voidaan hyödyntää nykyistä paremmin.
ED:2013-12-02
INSSI record number: 48103
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