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Extraction of Lignin from Kraft Cooking Liquor by Ultrafiltration

Wallberg, Ola LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

Lignin är ett biobränsle som kan extraheras från sulfatmassaindustrins koklutar (svartlut). Lignin kan även användas som specialkemikalie. Massaindustrin har därmed tillgång till en än så länge outnyttjad källa för inkomster. Dessutom kan ligninuttag leda till processförbättringar under kokning och blekning av pappersmassan.



I det här arbetet har ligninuttag med keramiska ultrafiltreringsmembran studerats. Experimenten har utförts vid temperaturer upp till 90°C i laboratoriestudien samt vid temperaturer upp till 145°C vid ett massabruk. Ny metodik utvecklades för att göra det möjligt att arbeta vid dessa höga temperaturer på ett säkert och tillförlitligt sätt.

... (More)
Popular Abstract in Swedish

Lignin är ett biobränsle som kan extraheras från sulfatmassaindustrins koklutar (svartlut). Lignin kan även användas som specialkemikalie. Massaindustrin har därmed tillgång till en än så länge outnyttjad källa för inkomster. Dessutom kan ligninuttag leda till processförbättringar under kokning och blekning av pappersmassan.



I det här arbetet har ligninuttag med keramiska ultrafiltreringsmembran studerats. Experimenten har utförts vid temperaturer upp till 90°C i laboratoriestudien samt vid temperaturer upp till 145°C vid ett massabruk. Ny metodik utvecklades för att göra det möjligt att arbeta vid dessa höga temperaturer på ett säkert och tillförlitligt sätt.



Membran med cut-off 5000 och 15000 g/mol har använts under de experimentella studierna. Fluxet av lut var 55 l/m² h och 110 l/m² h vid koncentrering till 90% volymreduktion vid 90°C för de båda membranen. Retentionen av lignin var samtidigt 60% och 30%. Ligninets renhet med avseende på den totala torrsubstansen ökade från 30% till 60% när membranet med cut-off 5000 användes. Att nå högre renhet av lignin var problematiskt därför föreslås det att fällning alternativt diafiltrering av retentatet används för att nå högre renhet.



I arbetet visas det att det är tekniskt möjligt att använda keramiska ultrafiltreringsmembran vid temperaturer över den normala kokpunkten när alkaliska lösningar filtreras. Fluxet var lägre när lut filtrerades i ett massabruk jämfört med när luten filtrerades i laboratoriet. Ligninretentionen minskar från 55% vid 90°C till 30% vid 145°C (400 kPa transmembrantryck).



Fouling och rengöring av membranen studerades både i laboratoriet och vid försöken på massabruket. En framgångsrik rengöringsmetod som baserades på sköljning med permeat utvecklades på laboratoriet. Vid försöken på bruk kunde membranen användas upp till 70 timmar utan att kapaciteten föll för mycket och den ursprungliga kapaciteten återställdes efter rengöring av membranen. (Less)
Abstract
Lignin is a potential biofuel which can be extracted from kraft cooking liquor. Lignin can also prove valuable as a speciality chemical. By extracting lignin potential economical revenue can be gained by pulp mills, as well as technical benefits such as easier delignification and bleaching.



The subject of this work was the extraction of lignin from kraft cooking liquor using ceramic ultrafiltration membranes. Experiments have been performed in both the laboratory, at temperatures below 100°C, and in a pulp mill at temperatures between 90°C and 145°C. In order to operate membranes at high temperatures new methods which ensure safe and reliable operation were developed.



Membranes with cut-offs of 5,000... (More)
Lignin is a potential biofuel which can be extracted from kraft cooking liquor. Lignin can also prove valuable as a speciality chemical. By extracting lignin potential economical revenue can be gained by pulp mills, as well as technical benefits such as easier delignification and bleaching.



The subject of this work was the extraction of lignin from kraft cooking liquor using ceramic ultrafiltration membranes. Experiments have been performed in both the laboratory, at temperatures below 100°C, and in a pulp mill at temperatures between 90°C and 145°C. In order to operate membranes at high temperatures new methods which ensure safe and reliable operation were developed.



Membranes with cut-offs of 5,000 Da and 15,000 Da have been used in the experimental studies. In the laboratory investigation the average flux at 90°C during concentration to 90% volume reduction of kraft cooking liquor was 55 l/m² h and 110 l/m² h using the 5,000 Da and 15,000 Da cut-off membranes, respectively. At the same time the lignin retention was 60% and 30%. Lignin purity with respect to total dry solids content was increased from 30% to 60% using the membrane with a cut-off of 5,000 Da. Reaching higher lignin purities by ultrafiltration alone proved difficult, and it is therefore suggested that diafiltration or acid precipitation be used on the ultrafiltration retentate to achieve higher lignin purities.



It was shown that it is technically feasible to operate ceramic ultrafiltration membranes at temperatures above the normal boiling point when treating highly alkaline solutions. The flux was lower when treating kraft cooking liquor in a pulp mill than in the laboratory investigation. It was found that the lignin retention is temperature dependent, decreasing from 55% at 90°C to 30% at 145°C (at 400 kPa transmembrane pressure).



Fouling and cleaning of the membranes were investigated both in laboratory and in mill trials. A successful cleaning method based on rinsing with cooking liquor permeate followed by alkaline cleaning was developed in the laboratory investigation. It was found in the mill trials that the membranes could be operated for up to 70 hours without the fouling becoming too severe and that the capacity of the membranes was restored after chemical cleaning. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • ass. professor Luque Rodríguez, Susana, University of Oviedo, Spain
organization
publishing date
type
Thesis
publication status
published
subject
keywords
lignin, Chemical technology and engineering, cooking liquor, kraft black liquor, Kemiteknik och kemisk teknologi, Ultrafiltration
pages
74 pages
publisher
Department of Chemical Engineering, Lund University
defense location
Room K:C, Centre for Chemistry and Chemical Engineering Getingevägen 60 Lund Institute of Technology
defense date
2005-11-18 13:15
external identifiers
  • other:ISRN: LUTKDH/(TKKA-1004)/1-74/(2005)
ISSN
1100-2778
ISBN
91-7422-092-6
language
English
LU publication?
yes
id
4948be04-e366-48e1-9e59-41cccac6e5ad (old id 545518)
date added to LUP
2007-10-13 13:21:14
date last changed
2016-09-19 08:44:59
@phdthesis{4948be04-e366-48e1-9e59-41cccac6e5ad,
  abstract     = {Lignin is a potential biofuel which can be extracted from kraft cooking liquor. Lignin can also prove valuable as a speciality chemical. By extracting lignin potential economical revenue can be gained by pulp mills, as well as technical benefits such as easier delignification and bleaching.<br/><br>
<br/><br>
The subject of this work was the extraction of lignin from kraft cooking liquor using ceramic ultrafiltration membranes. Experiments have been performed in both the laboratory, at temperatures below 100°C, and in a pulp mill at temperatures between 90°C and 145°C. In order to operate membranes at high temperatures new methods which ensure safe and reliable operation were developed.<br/><br>
<br/><br>
Membranes with cut-offs of 5,000 Da and 15,000 Da have been used in the experimental studies. In the laboratory investigation the average flux at 90°C during concentration to 90% volume reduction of kraft cooking liquor was 55 l/m² h and 110 l/m² h using the 5,000 Da and 15,000 Da cut-off membranes, respectively. At the same time the lignin retention was 60% and 30%. Lignin purity with respect to total dry solids content was increased from 30% to 60% using the membrane with a cut-off of 5,000 Da. Reaching higher lignin purities by ultrafiltration alone proved difficult, and it is therefore suggested that diafiltration or acid precipitation be used on the ultrafiltration retentate to achieve higher lignin purities.<br/><br>
<br/><br>
It was shown that it is technically feasible to operate ceramic ultrafiltration membranes at temperatures above the normal boiling point when treating highly alkaline solutions. The flux was lower when treating kraft cooking liquor in a pulp mill than in the laboratory investigation. It was found that the lignin retention is temperature dependent, decreasing from 55% at 90°C to 30% at 145°C (at 400 kPa transmembrane pressure).<br/><br>
<br/><br>
Fouling and cleaning of the membranes were investigated both in laboratory and in mill trials. A successful cleaning method based on rinsing with cooking liquor permeate followed by alkaline cleaning was developed in the laboratory investigation. It was found in the mill trials that the membranes could be operated for up to 70 hours without the fouling becoming too severe and that the capacity of the membranes was restored after chemical cleaning.},
  author       = {Wallberg, Ola},
  isbn         = {91-7422-092-6},
  issn         = {1100-2778},
  keyword      = {lignin,Chemical technology and engineering,cooking liquor,kraft black liquor,Kemiteknik och kemisk teknologi,Ultrafiltration},
  language     = {eng},
  pages        = {74},
  publisher    = {Department of Chemical Engineering, Lund University},
  school       = {Lund University},
  title        = {Extraction of Lignin from Kraft Cooking Liquor by Ultrafiltration},
  year         = {2005},
}