magistrsko delo študijskega programa II. stopnje
Gregor Kravanja (Author), Željko Knez (Mentor), Mojca Škerget (Co-mentor)

Abstract

Namen magistrske naloge je bil postavitev merilne naprave in razvoj nove metode merjenja površinske napetosti s kapilarnim dvigom dvofaznih sistemov v okolici kritične točke. Za pridobitev natančnih in primerljivih meritev je bilo potrebno poznati natančni notranji premer tankih kapilar. Določili smo ga z metodo laserskega tipanja na nemški koordinatni merilni napravi ZEISS tipa UMC-850 s pomočjo merilne programske opreme CALYPSO 5.1.4. Za merjenje ravnotežne višine smo uporabili računalniški program Logger Pro, ki omogoča natančno analizo razdalj med dvema točkama. Gostote dvofaznih sistemov smo dobili iz podatkovne baze NIST ali jih izmerili s pomočjo gravimetrične metode jemanja vzorcev iz mešalnega avtoklava. Površinsko napetost smo merili v treh dvofaznih sistemih: voda/CO2, slanica/CO2 in polimer PEG/CO2 v razponu od 1 bara do 200 barov. Prve meritve smo izvedli za sistem voda/CO2 pri treh izotermah (25 °C, 45 °C in 60 °C) in jih primerjali z literaturo. Ugotovili smo, da daje naša metoda primerljive in ponovljive rezultate, ki kažejo, da se s povečanjem tlaka površinska napetost linearno zmanjšuje do območja fazne spremembe CO2, v območju višjih tlakov pa doseže konstantno vrednost. Zanimiva je tudi ugotovitev, da se površinska napetost pri atmosferskih pogojih z nižanjem temperature poveča, v območju višjih tlakov pa pada. Zaradi možnosti skladiščenja toplogrednega plina CO2 v slanico smo v avtoklavu simulirali razmere, ki potekajo pri vbrizgavanju CO2 v slane reke več kilometrov pod zemljo. Ugotovili smo, da se z višanjem koncentracije soli v vodni raztopini (od 14 g/l do 200 g/l) viša vrednost površinske napetosti. Z namenom pridobitve še neraziskanih termodinamskih podatkov v okolici kritične točke smo izmerili površinsko napetost sistema polimera PEG/CO2. Rezultati kažejo, da se je površinska napetost sistema PEG/CO2 (molske mase PEG: 200, 400, 600) s povečanjem tlaka prav tako linearno zmanjševala.

Keywords

površinska napetost;kapilarni dvig;gostota;slanica;PEG;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher: [G. Kravanja]
UDC: 536.2:683.97(043.2)
COBISS: 18248214 Link will open in a new window
Views: 2161
Downloads: 476
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Other data

Secondary language: English
Secondary title: DETERMINATION OF THE SURFACE TENSION BY THE CAPILLARY RISE METHOD IN TWO-PHASE SYSTEMS
Secondary abstract: The aim of the thesis was to place a measuring device for determination of the surface tension by the capillary rise method in two-phase systems at higher pressures. In order to obtain accurate and comparable measurements, it was necessary to know the exact inner diameter of the thin capillaries, which we have determined by measuring on the German coordinate machine ZEISS type UMC - 850 using a software CALYPSO 5.1.4. To measure the equilibrium height, we used a computer program Logger Pro, which enables detailed analysis of distances between two points. The densities of two-phase systems were obtained from the NIST database, or measured by the gravimetric method of taking samples from the mixing autoclave. Surface tension was measured in the three two-phase systems: water/CO2 brine/CO2 and polymer PEG/CO2 in the range from 1 bar to 200 bar. The first measurements were performed for the system water/CO2 for three isotherms (25° C, 45° C and 60° C) and compared with the literature. We found that our method provides comparable and reproducible results. As pressure increases, a decrease in the interfacial tension is observed, which is more pronounced at lower temperatures. At lower pressures surface tension decreases with rising temperature; at higher pressures the opposite effect is found. Due to the potential of storage of the greenhouse gas CO2 in brine, we simulated conditions in an autoclave, which take place when injecting CO2 into saline river several hundred meters underground. We found that by increasing the salt concentration in the aqueous solution (form 14g/l to 200g/l) the surface tension value increases. In order to obtain so far unexplored thermodynamic data, surface tension of the system polymer PEG/CO2 was measured. The results show that by increasing pressure the surface tension of the system PEG/CO2 (molar mass of PEG: 200, 400, 600) decreased linearly likewise.
Secondary keywords: surface tension;capillary rise method;density;brine;PEG;
URN: URN:SI:UM:
Type (COBISS): Master's thesis/paper
Thesis comment: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages: XI, 77 str.
ID: 8730179