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Author:Mäntyvaara, Tanja
Title:Refraktometrin prisman likaantuminen
The fouling of the refractometer prism
Publication type:Master's thesis
Publication year:2011
Pages:[7] + 80      Language:   fin
Department/School:Elektroniikan laitos
Main subject:Elektroniikan valmistustekniikka   (S-113)
Supervisor:Paulasto-Kröckel, Mervi
Instructor:Voipio, Ville ; Turunen, Markus
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201207022751
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  1226   | Archive
Keywords:fouling
prism
colloid
crystallization
refractometer
elecrical double layer
agglomeration
deposition
likaantuminen
prisma
kolloidi
kiteytyminen
refraktometri
sähköinen kaksoiskerros
agglomeroituminen
kerrostuminen
Abstract (eng): This thesis seeks to find a better understanding of how a prism of an optical measuring device, a refractometer, gets fouled.
A refractometer measures the concentration of dissolved solids in a process liquid by determining the refractive index of the liquid in contact with the prism.
Prism fouling deteriorates the reliability of the measurement.

One aim of this work was to do a literature review to recognize possible surface fouling mechanisms and factors contributing to the fouling.
Experiments were performed to investigate the influence of fouling on the refractometer optical performance and measurement results and also to find repeatable fouling methods for laboratory use.
The results from this work were used to find plausible ways to reduce prism fouling.

The most common prism fouling mechanisms are colloidal fouling and scaling (crystallization).
The colloidal fouling mechanism was studied by using milks, cream, milk powder, quartz powders and carbon nanotubes.
The scaling was, in turn, studied with potassium nitrate and sucrose.

Factors influencing colloidal fouling are surface charges of the fouling particles and the surface, an ionic strength of the process liquid, pH, flow conditions, viscoelasticity of the colloidal substance, adhesion and cohesion forces between the fouling substance and the surface and also a surface energy.
Factors influencing crystallization are among other things temperature, concentrations, flow conditions and also the fouling material itself.

As a result, the prism fouling could be recognized in most cases either from the refractometer optical image or other measurement results.
The experimental setup proved to provide a practical way of producing repeatable scaling and colloidal fouling with certain colloids.
In the future these methods will be used to carry out further research on prism fouling prevention.
Abstract (fin): Tässä työssä tutkittiin prosessiteollisuudessa käytettävän optisen mittalaitteen, refraktometrin, prisman likaantumista.
Refraktometri mittaa prosessinesteen liuenneiden aineiden pitoisuutta määrittämällä prismaan kontaktissa olevan nesteen taitekerrointa.
Prisman likaantuminen laskee mittausluotettavuutta.

Työssä pyrittiin tunnistamaan mahdollisia pintojen likaantumismekanismeja sekä likaantumiseen vaikuttavia tekijöitä kirjallisuusselvityksen perusteella.
Työssä selvitettiin kokeiden avulla likaantumisen vaikutusta refraktomerin suorituskykyyn ja mittaustuloksiin sekä pyrittiin löytämään toistettavia likaannuttamistapoja.
Saatujen tulosten avulla pyrittiin löytämään tapoja vähentää prisman likaantumista.

Yleisimmät prisman likaantumismekanismit ovat kolloidinen ja kiteytyvä likaantuminen.
Kolloidisten aineiden aiheuttamaa likaantumista pyrittiin selvittämään maitojen, kerman, maitojauheen, kvartsihiukkasten sekä hiilisuspension avulla.
Kiteytyvää prisman likaantumista tutkittiin kaliumnitraatin ja sakkaroosin avulla.

Kolloidien aiheuttamassa likaantumisessa keskeisessä asemassa ovat likaavien partikkelien ja prisman pinnan pintavaraukset, prosessinesteen ionivahvuus, pH, virtausolosuhteet, kolloidisen aineen viskoelastisuus sekä likaavan aineen ja pinnan väliset adheesio- ja koheesiovoimat sekä pintaenergia.
Kiteytyvään prisman likaantumiseen vaikuttavat muun muassa lämpötila, pitoisuudet, virtausolosuhteet sekä itse likaava aine.

Pääsääntöisesti prisman likaantuminen voitiin tunnistaa joko optisesta kuvasta tai muista mittaustuloksista.
Työssä käytettävä koejärjestely osoittautui hyväksi prisman likaannuttamistavaksi etenkin kiteytyvien aineiden sekä muutaman kolloidisen aineen kohdalla.
Näitä likaannuttamistapoja tullaan tulevaisuudessa käyttämään tutkimuksissa prisman puhtaanapysymisen edistämisessä.
ED:2012-02-01
INSSI record number: 43899
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