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PhD topics for academic year 2021/2022

Department of Chemical Engineering

Chemical and Process Engineering

Faculty of Chemical Engineering

Gas - Liquid Mass Transfer. Experimental comparison of various apparatuses performance.

Moucha Tomáš, prof. Dr. Ing. ( mou...@vscht.cz)
The volumetric mass transfer coefficient (kLa) plays a crucial role in industrial design in the case of the process controlled by gas–liquid mass transfer. Prediction of kLa is nowadays mostly based on literature correlations. Our research goal is to establish suitable kLa correlations for different types of devices that would be based on the experimental dataset. The PhD thesis aim at the comparison of various gas-liquid contactor types from the viewpoint of their mass transfer efficiency. The suitable correlations will be developed that would be viable for mechanically agitated gas–liquid contactors and also for pneumatically agitated gas–liquid contactors such as airlift reactor.
Development principles: 1. Seznamte se s popisy mezifázového transportu hmoty mezi plynem a kapalinou včetně bilancí různých typů kontaktorů kapalina - plyn
2. Prostudujte matematické popisy procesu sdílení hmoty, které umožňují stanovení koeficientů přestupu hmoty z experimentálních dat
3. Seznamte se s dostupnými experimentálními zařízeními na UNIPA v pracovní skupině prof. Brucato a prof. Scargiali a na VŠCHT v Laboratoři SH
4. Sestavte plán experimentů, které poskytnou výsledky umožňující porovnání efektivity jednotlivých zařízení podle zvolených kritérií
5. Teoretické poznatky, experimentální postupy a výsledky sepište společně se závěry do podoby dizertační práce
Faculty of Chemical Engineering

KLa - shear stress coupling to design fermenters better

Moucha Tomáš, prof. Dr. Ing. ( mou...@vscht.cz)
In fermentation technologies, mechanically agitated aerated vessels are frequently used. In cases of aerobic fermentations, the Oxygen Uptake Rate - OUR is frequently used as the important design parameter. This means that the gas-liquid mass transfer controlled process is considered and the volumetric mass transfer coefficient - kLa is taken as the most important parameter. The practice shows, however, that the impellers with lower Power number (which means lower turbulence intensity and lower kLa) often ensure higher bioprocess efficiency than those with high Power number (which means higher turbulence intensity and higher kLa). The explanation is brought by the fact that microorganisms/biomass might be damaged by the high turbulence intensity as explained further. The turbulence intensity is proportional to shear stresses occuring in the mechanically agitated fermentation batch. A high shear stress may "cut" the microorganisms, which stop producing their primary product then. The aim of the PhD thesis is to measure the quantities proportional to shear stress values at the process conditions of aerobic fermentations and couple them with the kLa values, which are already at disposal in the Mass Transfer Lab database at UCT Prague. This data coupling will enable to develope the highly efficient industrial fermenters design tool.
Development principles: 1. Seznamte se s popisem transportu hmoty mezi plynem a kapalinou v mechanicky míchaných disperzích
2. Seznamte se s popisem lokálních intenzit turbulnce, fluktuačních rychostí a střižných sil v mechanicky míchaných disperzích kapalina-plyn
3. Prostudujte experimentální techniky měření kLa v Laboratoři sdílení hmoty VŠCHT Praha a techniky měření veličin úměrných intenzitě turbulence na TU Berlin.
4. Prostudujte experimetální podmínky použité k získání kLa dat v databázi na VŠCHT Praha a za shodných podmínek proměřte veličiny úměrné intenzitě turbulence metodikami užívanými na TU Berlin
5. Doplňte databázi kLa dat o veličiny použitelné k výpočtu střižných rychlostí a navrhněte způsob využití takto spárovaných veličin pro návrh mechanicky míchaných fermentorů.
Faculty of Chemical Engineering

Characterization and modelling of dispersion systems with variable viscosity

Šoóš Miroslav, prof. Ing. Ph.D. ( Mir...@vscht.cz)
Kuhn Simon, Prof. Dr. ( sim...@kuleuven.be)
The goal of this project is to characterize and model systems where viscosity of the dispersed phase is rising during the process. Typical examples are emulsification, suspension polymerization or spherical agglomeration. The student will start with simplified system composed of two liquid phases with various viscosities, which will be analyzed by on-line sensors providing information about the droplets sizes. Experimental activity will cover both batch as well as continuous operation modes. Collected data will be consequently used to develop engineering model based on computational fluid dynamic of the fluid flow coupled with population balances to describe coalescence and breakup of dispersed phase for various levels of dispersed phase viscosity. An extension of this activity will be process of spherical agglomeration where dispersed phase will contain particles (nanoparticles or crystals), which can undergo agglomeration and thus increasing the viscosity of the dispersed phase. Developed model will be validated against experimental data collected at various scales or operating conditions.
KU Leuven, Belgium
Faculty of Chemical Engineering

Polymer-based membranes for highly selective removal of CO2 from biogas

Kočí Petr, doc. Ing. Ph.D. ( pet...@vscht.cz)
Vankelecom Ivo, prof. ( ivo...@kuleuven.be)
Membrane-based gas separation technology has contributed significantly to the development of energy-efficient systems for natural gas purification. Also CO2 removal from biogas, with CO2 contents exceeding 40% has more recently known rapid growth and development. Major challenge of polymer membranes for gas separation is related to their susceptibility to plasticization at high CO2 partial pressures. CO2 excessively swells the polymer and eases the permeation of CH4, thus reducing the selectivity. Membrane crosslinking is one of the best ways to prevent the plasticization. Mixed matrix membranes (MMMs), consisting of fillers homogeneously dispersed in a polymeric matrix aim at combining the processibility of polymers and the superior separation properties of the porous fillers. Metal-organic frameworks (MOFs) are such materials which have attracted considerable attention due to their tailorable functionality, well-defined pore size, pore tunability and breathing effects. MMMs for biogas upgrading will be prepared with increased permeabilities by choosing proper MOF/polymer combinations and modifying the thermal treatment, employing core-shell MOF materials with high bulk porosity and a selective shell layer.

KU Leuven, Belgium
Faculty of Chemical Engineering

Solvent and pH stable membranes with ultra-sharp molecular weight cut-off values

Kočí Petr, doc. Ing. Ph.D. ( pet...@vscht.cz)
Vankelecom Ivo, prof. ( ivo...@kuleuven.be)
Membrane-based separations currently offer the best strategy to decrease energy requirements and environmental footprint through newly developed solvent resistant nanofiltration (SRNF) or solvent-tolerant nanofiltration (STNF). So-called solvent activation of polymeric membranes involves treatment of an existing membrane by contacting it with solvents or solvent mixtures, which is hypothesized to restructure the membrane polymer through solvatation, increase polymer chain flexibility and organization into suitable structures. This will be verified by systematically treating membranes with different solvents and testing them for the separation of synthetic liquid streams. A high-throughput set-up will be used. Fundamental physico-chemical characterisations of the membranes before and after the treatments will provide insight in the changes at molecular level. The characterization techniques include gas and liquid uptake experiments (diffusivity), PALS (positron annihilation lifetime spectroscopy, to determine free volume element distributions), ERD (elastic recoil scattering, providing elemental analysis in membrane depth profiles), solid state NMR (nuclear magnetic resonance), TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry).

KU Leuven, Belgium
Updated: 29.11.2019 12:30, Author: Jan Kříž

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