A statistical approach: understanding the variation in induction time to measure nucleation rates
Visualitza/Obre
Report (1,840Mb) (Accés restringit)
Sol·licita una còpia a l'autor
Què és aquest botó?
Aquest botó permet demanar una còpia d'un document restringit a l'autor. Es mostra quan:
- Disposem del correu electrònic de l'autor
- El document té una mida inferior a 20 Mb
- Es tracta d'un document d'accés restringit per decisió de l'autor o d'un document d'accés restringit per política de l'editorial
Estadístiques de LA Referencia / Recolecta
Inclou dades d'ús des de 2022
Cita com:
hdl:2099.1/24003
Tutor / directorHorst, Joop ter
Tipus de documentTreball Final de Grau
Data2013
Condicions d'accésAccés restringit per decisió de l'autor
Tots els drets reservats. Aquesta obra està protegida pels drets de propietat intel·lectual i
industrial corresponents. Sense perjudici de les exempcions legals existents, queda prohibida la seva
reproducció, distribució, comunicació pública o transformació sense l'autorització del titular dels drets
Abstract
Crystal nucleation is the first and most important step in crystallization process as it has strong impact on crystal product quality. An easy, reliable and accurate way to measure nucleation rate in stirred solutions is the induction time measurement method. At small scale for many systems
the method makes use of variations in measurements which are due to stochastic nature of nucleation and measure nucleation rates based on probability distribution of induction times. The variations could also be because of errors in manual sampling or the analytical technique used. A
statistical analysis of experimental data of induction time measurements was performed to
identify experimental errors. This includes observing the variations due to different factors such as average levels of supersaturation, position in the setup, operating temperatures, etc. which can
affect to the results of the process.
Nicotinamide (NA) in ethanol was used as model system for performing the experiments of induction time measurements under different supersaturation conditions. It was detected that the position where the samples are hold in the setup has no significant influence on the nucleation process.
It was also noticed a statistically significant decrease in the probability distribution so as the nucleation rate of NA with each repetition of experiments of the same samples. It was verified that there are no changes in the saturation temperature, which indicates that there is no degradation
of the compound. A possible explanation of the behaviour of nucleation rates could therefore be the presence of active particles responsible for heterogeneous nucleation which deactivate with the cycles. Actually, the low determined thermodynamic parameter show that heterogeneous nucleation rather that homogeneous nucleation occurs. Moreover, samples of NA in ethanol were
heated to different maximum temperatures like 50ºC, 60ºC and 70ºC and cooled to 25ºC to measure induction times. It was observed that the heating temperature does significantly affect to the nucleation process, as the nucleation rate J decreases with increase in the heating temperature.
This also support the presence of impurities in the system.
4-hydroxyacetophenone (HAP) in ethyl acetate was also used to perform induction time
measurements, and there were no significant differences in the experimental nucleation rate results between the repetitions of the experiments of the same samples. It can therefore be stated that the phenomenon is only system dependent which was observed in case of NA in ethanol.
Col·leccions
Fitxers | Descripció | Mida | Format | Visualitza |
---|---|---|---|---|
Report_Nuria_Llort.pdf | Report | 1,840Mb | Accés restringit |