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Thermal Decomposition of Inorganic Polysulfides at Kraft Cooking Conditions
KTH, Tidigare Institutioner                               , Pappers- och massateknik.ORCID-id: 0000-0002-2900-4713
1995 (Engelska)Ingår i: Nordic Pulp Paper Research Journal, ISSN 0283-2631, Vol. 10, nr 1, s. 41-Artikel i tidskrift (Refereegranskat) Published
Ort, förlag, år, upplaga, sidor
1995. Vol. 10, nr 1, s. 41-
Nationell ämneskategori
Pappers-, massa- och fiberteknik
Identifikatorer
URN: urn:nbn:se:kth:diva-12998OAI: oai:DiVA.org:kth-12998DiVA, id: diva2:320082
Anmärkning
QC 20100521Tillgänglig från: 2010-05-21 Skapad: 2010-05-21 Senast uppdaterad: 2010-05-21Bibliografiskt granskad
Ingår i avhandling
1. Some factors affecting the amount of residual phase lignin during kraft pulping
Öppna denna publikation i ny flik eller fönster >>Some factors affecting the amount of residual phase lignin during kraft pulping
1997 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The amount of lignin which needs to be removed according to the slow residual delignification phase in kraft pulping, i e residual phase lignin, has been studied as a function of the process conditions. The variebles studied were the concentrations of hydroxide ions, hydrogensulfide ions, sodium ions (ionic strength) and temperature. In addition, the amounts of residual phase ligning in the pulping of different lignocellulosic material were compared. Different additives can be applied to the kraft cook to improve the selectivity. Polysulfide sulfur is one of them and the effectt of polysulfide ions on the amount of residual phase lignin in kraft pulping was also investigated.

It is shown, that the amounts of residual phase lignin in constant composition cooks (highliquor-to-wood ratio) of softwood (spruce), hardwood (birch) andgrass (wheat straw) are affected by the same factors in theinvestigated range. The amount of residual phase lignin isstrongly reduced by higher hydroxide ion concentration during the kraft cook and is to some extent decreased by higherhydrogensulfide ion concentration and lower sodium ionconcentration. These effects were not, however, found to bepurely additive for spruce wood, instead interactions occurred.In order to decrease the amount of residual phase lignin, it isessential to have a high concentration of hydrogensulfide ionswhen cooking with a low hydroxide ion concentration. The temperature has no effect on the amount of residual phase ligninin the range investigated.

It is also shown that the lignin reacting according to theslow delignification phase is not a homogeneous lignin sincealteration of the conditions in the cook can make part of itreact as bulk phase lignin. This indicates that most of theresidual phase lignin is determined by the prevailing conditions,which determine how much of the native lignin reacts according tothe bulk and how much according to the residual delignificationmechanism.

Pulping experiments carried out under the same conditions onwheat straw,  birch wood and spruce wood also showed that theamount of residual phase lignin in wheat straw is only 30% of theamount of residual phase lignin in spruce wood, and that the amount of residual phase lignin in birch wood, is5 0% of the amount of residual phase lignin in sprucewood.

The amount of residual phase lignin was affected by apolysulfide treatment. The amount of residual phase lignin was lowered by 30% for spruce wood and 10% for birch wood with apolysulfide treatment, compared with cooks without polysulfide. An explanation for this may be the finding that polysulfide can introduce a carboxylic acid function into the lignin, which will increase its water solubility, and reduce the need for fragmentation. An additional explanation may be the ability of polysulfides to degrade enol ether structures, which are normally more or less stable during kraft pulping.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 1997. s. 52
Serie
Trita-PMT ; 1997:5
Nyckelord
Deligniflcation, Residual phase lignin, Hydrogensulfide ion, Hydroxide ion, Polysulfides, Ionic strength, Temperature, Lignin, Kraftpulping, Selectivity, viscosity, Kappa number, chemical degradation, Disproportionation
Nationell ämneskategori
Pappers-, massa- och fiberteknik
Identifikatorer
urn:nbn:se:kth:diva-2502 (URN)99-2412642-4 (ISBN)
Disputation
1997-05-22, 00:00 (Engelska)
Anmärkning
QC 20100521Tillgänglig från: 2000-01-01 Skapad: 2000-01-01 Senast uppdaterad: 2010-05-21Bibliografiskt granskad

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Lindström, Mikael E.

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