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Thermodynamic Modelling of Electrolyte Solutions with Application to the Pulp and Paper Industry

Jaretun, Anders LU (2000)
Abstract (Swedish)
Popular Abstract in Swedish

Elektrolyter är ämnen som sönderdelas i ett lösningsmedel och därvid ger upphov till positivt och negativt laddade joner. De starka elektrostatiska krafter i lösningen som detta i sin tur orsakar är typiska för elektrolytlösningar. Redan vid små tillsatser av en elektrolyt till ett lösningsmedel kan lösningens egenskaper förändras kraftigt. Lösningar av elektrolyter spelar en viktig roll inom ett stort antal kemiska processer, liksom i en mängd biologiska och geokemiska system. Under senare år har intresset för möjligheten till simulering och optimering av processer som innefattar elektrolyter vuxit kraftigt som ett resultat av den ökade miljömedvetenheten inom processindustrin.

... (More)
Popular Abstract in Swedish

Elektrolyter är ämnen som sönderdelas i ett lösningsmedel och därvid ger upphov till positivt och negativt laddade joner. De starka elektrostatiska krafter i lösningen som detta i sin tur orsakar är typiska för elektrolytlösningar. Redan vid små tillsatser av en elektrolyt till ett lösningsmedel kan lösningens egenskaper förändras kraftigt. Lösningar av elektrolyter spelar en viktig roll inom ett stort antal kemiska processer, liksom i en mängd biologiska och geokemiska system. Under senare år har intresset för möjligheten till simulering och optimering av processer som innefattar elektrolyter vuxit kraftigt som ett resultat av den ökade miljömedvetenheten inom processindustrin.



Det finns ett stort antal modeller tillgängliga för att förutsäga egenskaper hos elektrolytlösningar; allt från enkla modeller med få parametrar till mer sofistikerade flerparametermodeller. Ett problem är att många av modellerna endast kan tillämpas på vattenlösningar av elektrolyter vid låga koncentrationer. Det finns därför utrymme för fortsatta studier och utvecklande av nya modeller med större giltighetsintervall.



I detta arbete har en existerande modell modifierats för att på så sätt avsevärt utöka dess tillämpningsområde, vad avser elektrolyternas koncentration. Den modifierade modellen har testats med goda resultat på vattenlösningar innehållande en elektrolyt, samt på blandningar av flera elektrolyter i vatten. Framför allt för en-elektrolyt blandningar uppvisar den nya modellen en mycket hög noggrannhet i jämförelse med andra modeller. Vidare behövs endast få modellparametrar för att beskriva mer komplicerade blandningar, och noggrannheten är också för dessa system mycket god.



En annan modell än den som utvecklats i detta arbete, tillgänglig i ett kommersiellt simuleringsprogram, har utnyttjats för att simulera en utfällningsprocess för utstötning av främmande ämnen inom pappersmassaindustrin, och simuleringsresultaten har jämförts med experimentella resultat från laboratoriestudier. Överensstämmelsen mellan experimentella och beräknade resultat är relativt god men det finns möjligheter att förbättra beräkningsmodellen ytterligare. (Less)
Abstract
A thermodynamic model for electrolyte solutions has been derived for binary and multicomponent solutions up to very high molalities. The model was extensively tested on 163 binary aqueous electrolyte systems up to very high molalities, and the results show that the model represents mean ionic activity coefficients and osmotic coefficients very accurately. The model parameters vary significantly between different electrolyte systems, which is probably due to strongly correlated parameters and possibly also due to ion association effects. In the extension of the model to multicomponent systems, the identification of the model parameters was somewhat modified, and an assumption reduced the number of model parameters from four to two per... (More)
A thermodynamic model for electrolyte solutions has been derived for binary and multicomponent solutions up to very high molalities. The model was extensively tested on 163 binary aqueous electrolyte systems up to very high molalities, and the results show that the model represents mean ionic activity coefficients and osmotic coefficients very accurately. The model parameters vary significantly between different electrolyte systems, which is probably due to strongly correlated parameters and possibly also due to ion association effects. In the extension of the model to multicomponent systems, the identification of the model parameters was somewhat modified, and an assumption reduced the number of model parameters from four to two per electrolyte–solvent system. It was found that the regressed model parameters vary much less between different electrolyte systems. The multicomponent model predicts osmotic coefficients very accurately and salt solubilities with reasonable accuracy for multicomponent electrolyte systems, without using ternary parameters. Although very good results have been obtained, there is still room for improvement of the model, either by including ternary data in the parameter regression or by introducing ternary parameters.



An electrolyte model available in the commercial simulation program Aspen Plus was used to simulate a cooling crystallization process for the removal of non-process elements from a pulp and paper mill, and the simulation results were compared to experimental results. The comparison shows a fair agreement between the results although improvements still can be made. Leaching of electrostatic precipitator dust as a means of non-process element removal was also investigated experimentally. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Prof Rasmussen, Peter, Technical University of Denmark, Lyngby, Denmark
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Potassium, Chloride, Chemical recovery, Leaching, Crystallization, Kraft pulping, Non-process elements, Solubility, Local composition, Excess properties, Osmotic coefficient, Electrolytes, Activity coefficient, Wood, pulp and paper technology, Pappers- och massateknik
pages
132 pages
publisher
Chemical Engineering, Lund University
defense location
Lecture hall B, Centre for Mathematical Sciences, Sölveg. 18, Lund.
defense date
2000-05-12 10:15
external identifiers
  • other:LUTKDH/(TKKA-1002)/1-44/(2000)
ISSN
1100-2778
ISBN
91-7874-043-6
language
English
LU publication?
yes
id
8cf5125c-8a2b-41f9-9efc-e42b02c9cc77 (old id 40519)
date added to LUP
2007-08-01 09:35:31
date last changed
2016-09-19 08:44:59
@phdthesis{8cf5125c-8a2b-41f9-9efc-e42b02c9cc77,
  abstract     = {A thermodynamic model for electrolyte solutions has been derived for binary and multicomponent solutions up to very high molalities. The model was extensively tested on 163 binary aqueous electrolyte systems up to very high molalities, and the results show that the model represents mean ionic activity coefficients and osmotic coefficients very accurately. The model parameters vary significantly between different electrolyte systems, which is probably due to strongly correlated parameters and possibly also due to ion association effects. In the extension of the model to multicomponent systems, the identification of the model parameters was somewhat modified, and an assumption reduced the number of model parameters from four to two per electrolyte–solvent system. It was found that the regressed model parameters vary much less between different electrolyte systems. The multicomponent model predicts osmotic coefficients very accurately and salt solubilities with reasonable accuracy for multicomponent electrolyte systems, without using ternary parameters. Although very good results have been obtained, there is still room for improvement of the model, either by including ternary data in the parameter regression or by introducing ternary parameters.<br/><br>
<br/><br>
An electrolyte model available in the commercial simulation program Aspen Plus was used to simulate a cooling crystallization process for the removal of non-process elements from a pulp and paper mill, and the simulation results were compared to experimental results. The comparison shows a fair agreement between the results although improvements still can be made. Leaching of electrostatic precipitator dust as a means of non-process element removal was also investigated experimentally.},
  author       = {Jaretun, Anders},
  isbn         = {91-7874-043-6},
  issn         = {1100-2778},
  keyword      = {Potassium,Chloride,Chemical recovery,Leaching,Crystallization,Kraft pulping,Non-process elements,Solubility,Local composition,Excess properties,Osmotic coefficient,Electrolytes,Activity coefficient,Wood,pulp and paper technology,Pappers- och massateknik},
  language     = {eng},
  pages        = {132},
  publisher    = {Chemical Engineering, Lund University},
  school       = {Lund University},
  title        = {Thermodynamic Modelling of Electrolyte Solutions with Application to the Pulp and Paper Industry},
  year         = {2000},
}