Comparison of the effect of mechanical stirring and ultrasound on nucleation kinetics of borax in a batch cooling crystallizer : diploma thesis
| Autor: | Pažin, Anđela |
|---|---|
| Přispěvatelé: | Ćosić, Marija |
| Jazyk: | chorvatština |
| Rok vydání: | 2018 |
| Předmět: |
disodium tetraborate decahydrate
tinkal Mersmann's nucleation criterion TEHNIČKE ZNANOSTI. Kemijsko inženjerstvo dinatrijev tetraborat dekahidrat kinetika nukleacije boraks nucleation kinetics Mersmannov nukleacijski kriterij ultrasound amplitude (HELSCHER UP 400 St) šaržna kristalizacija s hlađenjem brzina vrtnje miješala borax impeller speed TECHNICAL SCIENCES. Chemical Engineering tincal amplituda ultrazvuka (HELSCHER UP 400 St) batch cooling crystallization |
| Popis: | Osnovni zadatak ovog rada bio je ispitati te usporediti utjecaj miješanja i ultrazvučnog djelovanja na kinetiku nukleacije boraksa u šaržnom kristalizatoru s hlađenjem. U kristalizatoru s miješanjem ispitivanja su se provodila pri trima različitim brzinama vrtnje miješala, dok se ispitivanje utjecaja ultrazvuka na kinetiku nukleacije izvršilo pri trima različitim amplitudama ultrazvuka. Eksperimenti su se provodili u kristalizatoru laboratorijskog mjerila, volumena 2,14 dm 3 , u kojem se matična otopina hladila linearnom brzinom od 6 °C h -1 . U prvom dijelu rada, za primijenjene brzine vrtnje miješala (N =100 -350 o. min -1 ) te amplitude ultrazvuka (A = 20 - 40 %), vizualno je određivana širina metastabilnih zona matičnih otopina zasićenih u temperaturnom području od 20 do 35 °C. Na temelju rezultata o širinama metastabilnih zona pri ispitivanim procesnim uvjetima, primjenom Mersmannovog nukleacijskog kriterija određen je dominantni nukleacijski mehanizam, a potom su izračunate i uspoređene brzine nukleacije. Na temelju vrijednosti brzina nukleacije pretpostavljene su karakteristike konačnog produkta kristalizacije s obzirom na veličinu kristala. Odstupanja od predviđenih pretpostavki prisutna su u onim sustavima u kojima nije bilo postignuto stanje potpune suspenzije. S obzirom da niti u jednom sustavu s ultrazvučni djelovanjem nije postignuto ovo stanje, preporuča se kristalizaciju boraksa uz ultrazvučno djelovanje provoditi u kombinaciji s mehaničkim miješanjem. The basic assignment of this study was to investigate and compare the effect of mechanical mixing and ultrasonic irradiation on kinetics of borax nucleation in the batch cooling crystallizer. In the crystallizer with mechanical mixing, the experiments were performed at three different rotational speeds, while the experiments with ultrasound irradiation were performed at three different ultrasound amplitudes. The experiments were carried out in a laboratory scale crystallizer, with a volume of 2.14 dm 3 , in which the mother liquor was cooled down by linear cooling of 6 °C h -1 . In the first part of the work, for the applied impeller rotational speeds (N = 100 - 350 rpm) and ultrasound amplitudes (A = 20 – 40 %), the metastable zones widths of the mother liquors saturated in the temperature range of 20 to 35 ° C were determined. Based on the results of metastable zones widths at the examined process conditions, using the Mersmann's nucleation criterion the dominant nucleation mechanism was determined and the values of nucleation rates were calculated. Also, the values of power consumption per unit mass of suspension saturated at 30 °C, at examined conditions were determined and compared. On the basis of values of nucleation rates, the characteristics of the final crystallization products were assumed regarding crystals size. Deviations from the predicted assumptions are present in those systems where the state of complete suspension has not been achieved. Since that this is the case inside the all of the systems with ultrasound irradiation, it is suggested to conduct crystallization of borax at applied mixing conditions but also to examine the nucleation kinetics of borax in the systems in which mixing and ultrasound are combined. |
| Databáze: | OpenAIRE |
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