Advanced

Ethanol from Softwood - Techno-Economic Evaluation for Development of the Enzymatic Process

Wingren, Anders LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

Etanol som produceras från förnyelsebara råvaror kan ersätta fossila bränslen som t.ex. bensin och diesel. Denna avhandling behandlar den enzymatiska processen för etanolproduktion från barrträd. Baserat på datorprogrammen Aspen Plus och Icarus Process Evaluator har ett verktyg för tekniska och ekonomiska beräkningar tagits fram i vilket hela processen, från trä till etanol, kan studeras och kritiska processparametrar identifieras. Simuleringsmodellen består av förbehandling av råvaran, enzymatisk hydrolys, jäsning, destillation, filtrering och avvattning av fiberrester, indunstning, torkning samt ångproduktion. Experimentella data har legat till grund för simuleringarna. I den påföljande... (More)
Popular Abstract in Swedish

Etanol som produceras från förnyelsebara råvaror kan ersätta fossila bränslen som t.ex. bensin och diesel. Denna avhandling behandlar den enzymatiska processen för etanolproduktion från barrträd. Baserat på datorprogrammen Aspen Plus och Icarus Process Evaluator har ett verktyg för tekniska och ekonomiska beräkningar tagits fram i vilket hela processen, från trä till etanol, kan studeras och kritiska processparametrar identifieras. Simuleringsmodellen består av förbehandling av råvaran, enzymatisk hydrolys, jäsning, destillation, filtrering och avvattning av fiberrester, indunstning, torkning samt ångproduktion. Experimentella data har legat till grund för simuleringarna. I den påföljande ekonomiska utvärderingen uppskattades produktionskostnaden för etanol för alternativa processkonfigurationer och för olika driftsbetingelser. Huvudsyftet med avhandlingen har varit att jämföra olika processalternativ snarare än att beräkna en absolut produktionskostnad för etanolen.



Produktionskostnaden var lägre för samtidig hydrolys och jäsning jämfört med separat hydrolys och jäsning. För samtidig hydrolys och jäsning identifierades både ett minskat ångbehov och en reducering av jästkoncentration som möjliga källor till en lägre produktionskostnad. Simuleringar visade att recirkulering av procesströmmar och ökad substratmängd i hydrolys- och jäsningsstegen resulterar i minskat ångbehov och en reducering av produktionskostnaden. Intressanta alternativ till traditionell flereffektsindunstning är mekanisk ångkompression samt produktion av biogas genom anaerob jäsning.



Utvärdering av förbehandling i två steg visade att detta processkoncept har potential att resultera i en lägre produktionskostnad än förbehandling i endast ett steg. Tvåstegsprocessen ger ett högre etanolutbyte samt har ett lägre behov av enzymer. En nackdel är det högre kapitalbehovet. Förbehandling i två steg måste dock verifieras i pilotskala.



Den framtagna modellen har också använts för att jämföra framställning av etanol från gran med en kommersiell process baserad på vete. Produktionskostnaden var något högre för cellulosaprocessen, men till skillnad från stärkelseprocessen finns det fortfarande mycket utvecklingsarbete kvar att göra. Jämfört med stärkelseprocessen kan cellulosaprocessen förbättras avsevärt genom ett högre etanolutbyte, lägre kapitalkostnad, minskat energibehov och effektivare enzymer. (Less)
Abstract
Ethanol produced from renewable resources can be used to replace fossil fuels such as gasoline and diesel. This thesis deals with the development of the enzymatic process used for ethanol production from softwood. A techno-economic tool, based on Aspen Plus and Icarus Process Evaluator, was developed in which the whole process, from raw material to ethanol, was studied and critical process parameters identified. The base case model consisted of steam pretreatment, enzymatic hydrolysis, fermentation, distillation, washing of fibrous residues, evaporation and drying, as well as steam and solid fuel production. In the subsequent economic evaluation the ethanol production cost was estimated and compared with costs obtained using alternative... (More)
Ethanol produced from renewable resources can be used to replace fossil fuels such as gasoline and diesel. This thesis deals with the development of the enzymatic process used for ethanol production from softwood. A techno-economic tool, based on Aspen Plus and Icarus Process Evaluator, was developed in which the whole process, from raw material to ethanol, was studied and critical process parameters identified. The base case model consisted of steam pretreatment, enzymatic hydrolysis, fermentation, distillation, washing of fibrous residues, evaporation and drying, as well as steam and solid fuel production. In the subsequent economic evaluation the ethanol production cost was estimated and compared with costs obtained using alternative process configurations and other process conditions. Based on experimental data it was concluded that a process based on simultaneous saccharification and fermentation (SSF) results in a lower ethanol production cost than separate hydrolysis and fermentation (SHF). The evaluation showed that significant savings in ethanol production cost could be made by reducing the yeast concentration in SSF and by reducing the process energy demand. Simulations showed that the latter could be accomplished by recirculation of process streams or by running the SSF process at a higher substrate load. Mechanical vapour recompression applied to the evaporation step and the replacement of the evaporation unit with an anaerobic digester were both identified as promising alternatives to multiple-effect evaporation of the stillage stream. Two-step steam pretreatment resulted in a lower ethanol production cost than pretreatment in one step. This process concept has yet to be proved on pilot scale. The model was also used for a comparison between the investigated lignocellulosic process and a commercial starch-based process. The ethanol production cost was slightly higher for the lignocellulosic process. However, compared to the starch-based process significant improvements can still be made to the lignocellulosic-based process by reduction of the enzyme loading, energy demand and capital cost. The potential for a higher ethanol yield is also much greater for the lignocellulosic process. The tool presented here is of importance for further development of the ethanol-from-wood process. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Saddler, John, Department of Wood Science, University of British Columbia, Vancouver, BC, Canada
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Kemiteknik och kemisk teknologi, process development, process simulation, ethanol production, Chemical technology and engineering, economic evaluation, softwood
pages
142 pages
publisher
Department of Chemical Engineering, Lund University
defense location
Room A, Centre for Chemistry and Chemical Engineering, Getingevägen 60, Lund Institute of Technology
defense date
2005-06-17 13:15
external identifiers
  • other:ISRN: LUTKDH/(TKKA-1003)/1-72/(2005)
ISSN
1100-2778
ISBN
91-7422-086-1
language
English
LU publication?
yes
id
73d29631-c1e1-44fa-920c-d57465080ed5 (old id 545138)
date added to LUP
2007-11-13 09:17:39
date last changed
2016-09-19 08:44:53
@phdthesis{73d29631-c1e1-44fa-920c-d57465080ed5,
  abstract     = {Ethanol produced from renewable resources can be used to replace fossil fuels such as gasoline and diesel. This thesis deals with the development of the enzymatic process used for ethanol production from softwood. A techno-economic tool, based on Aspen Plus and Icarus Process Evaluator, was developed in which the whole process, from raw material to ethanol, was studied and critical process parameters identified. The base case model consisted of steam pretreatment, enzymatic hydrolysis, fermentation, distillation, washing of fibrous residues, evaporation and drying, as well as steam and solid fuel production. In the subsequent economic evaluation the ethanol production cost was estimated and compared with costs obtained using alternative process configurations and other process conditions. Based on experimental data it was concluded that a process based on simultaneous saccharification and fermentation (SSF) results in a lower ethanol production cost than separate hydrolysis and fermentation (SHF). The evaluation showed that significant savings in ethanol production cost could be made by reducing the yeast concentration in SSF and by reducing the process energy demand. Simulations showed that the latter could be accomplished by recirculation of process streams or by running the SSF process at a higher substrate load. Mechanical vapour recompression applied to the evaporation step and the replacement of the evaporation unit with an anaerobic digester were both identified as promising alternatives to multiple-effect evaporation of the stillage stream. Two-step steam pretreatment resulted in a lower ethanol production cost than pretreatment in one step. This process concept has yet to be proved on pilot scale. The model was also used for a comparison between the investigated lignocellulosic process and a commercial starch-based process. The ethanol production cost was slightly higher for the lignocellulosic process. However, compared to the starch-based process significant improvements can still be made to the lignocellulosic-based process by reduction of the enzyme loading, energy demand and capital cost. The potential for a higher ethanol yield is also much greater for the lignocellulosic process. The tool presented here is of importance for further development of the ethanol-from-wood process.},
  author       = {Wingren, Anders},
  isbn         = {91-7422-086-1},
  issn         = {1100-2778},
  keyword      = {Kemiteknik och kemisk teknologi,process development,process simulation,ethanol production,Chemical technology and engineering,economic evaluation,softwood},
  language     = {eng},
  pages        = {142},
  publisher    = {Department of Chemical Engineering, Lund University},
  school       = {Lund University},
  title        = {Ethanol from Softwood - Techno-Economic Evaluation for Development of the Enzymatic Process},
  year         = {2005},
}