Browsing by Author "Nauha, Elina"

Filter results by typing the first few letters
Now showing 1 - 5 of 5
  • Dispersing water to hydrocarbon
    (2006) Nauha, Elina
     Helsinki University of Technology | Master's thesis
    Työn kirjallisuusosa keskittyi lähinnä emulsioihin. Kahden toisiinsa liukenemattoman nesteen dispergoinnin perusteet esitettiin, kuten myös eri ilmiöiden vaikutukset dispersioiden ominaisuuksiin ja aineensiirtoon. Markkinoilla olevat dispergointi- ja emulgointilaitteet esiteltiin, keskittyen lähinnä laitteisiin, joita voi käyttää jatkuvatoimisesti putkilinjastossa. Lisäksi esitettiin malleja, joiden avulla nesteiden dispergointikäyttäytymistä sekoittimissa ja näiden jälkeisessä prosessoinnissa voidaan ennustaa. Lopuksi käytiin läpi muutama neste-neste sekoituksen käytännön sovellus eri teollisuuden aloilta. Työn kokeellinen osa aloitettiin rakentamalla mittasysteemi, jolla mitattiin dynaamisella sekoittimella aikaansaadun dispersion pisarakokojakauma. Pisarakokojakaumat määritettiin valokuvaustekniikalla, joka mahdollisti halkaisijaltaan alimmillaan 5 gm pisaroiden havaitsemisen. Tert-butyylialkoholin (TBA) todettiin käyttäytyvän kuten pinta-aktiivinen aine sekä iso-oktaanin että 1-hekseenin vesirajapinnoilla. Tämä todettiin, kun rajapintajännitysmittaukset osoittivat arvojen laskevan TBA lisäyksen myötä. TBA:n lisäys tuotti pienemmän pisarakoon ja stabiloi dispersiota. Dispergoidun faasin tilavuusosuus ja sekoitusnopeus, jolla dispersio tuotettiin, vaikuttivat huomattavasti vähemmän dispersion ominaisuuksiin kuin TBA pitoisuus. Kokeiden toinen osa keskittyi veden liukoisuuteen hiilivetyyn. TBA:n lisäys nosti veden kyllästyspitoisuutta sekä iso-oktaanissa, että 1-hekseenissä. Veden liukoisuus 1-hekseeniin oli hieman korkeampi kuin iso-oktaaniin. Veden liukoisuusnopeuksien mittaamista kokeiltiin ja todettiin, että TBA vaikutti myös nopeuksiin positiivisesti.
  • Homekasvuston viskositeetin mallinnus
    (2013-04-29) Salmi, Katja
     Kemiantekniikan korkeakoulu | Bachelor's thesis
  • Modeling and sizing extraction equipment
    (2022-05-17) Ikäläinen, Juho
     Kemian tekniikan korkeakoulu | Master's thesis
  • Modeling of a rotodynamic reactor
    (2023-08-22) Haikala, Erik
     Kemian tekniikan korkeakoulu | Master's thesis
    Steam cracking is one of the most significant petrochemical processes, with products such as ethylene serving as some of the most important base chemicals. Unfortunately, steam cracking is also one of the most energy consuming and polluting processes in the entire chemical industry. The pressure towards decarbonization has resulted in immense interest towards the electrification of the steam cracking process, one significant example being the shockwave heating based RotoDynamic Reactor (RDR) being developed by Coolbrook. In addition to providing a general overview of the steam cracking process and conventional steam cracking equipment, the literature review part of this thesis aimed to collect and classify examples of undergoing developments towards electric steam cracking. Relevant journal articles, patents, and industrial publications were collected and classified into a framework of types of electrification technology, with the key finding being that while other forms of electric heating may be appealing for upgrading existing equipment, shockwave heating has the potential to bypass many of the existing limitations of conventional cracking. The applied part of the thesis focused on the task of importing state-of-the-art steam cracking kinetic models generated with RMG to Aspen Plus, with the eventual aim of modeling the RDR. The most significant part of the work covered creating a tool for translating RMG-generated kinetic models into Aspen Plus input files. Although the viability of the tool was limited by model convergence within Aspen Plus, ethane cracking with the RDR could be simulated at different residence times and severities, resulting in the desired characteristic temperature profiles of the RDR. Ultimately, product distributions observed for the RDR differed very little from the product distributions of conventional cracking coils.
  • Modeling of bioreactors
    (2019) Nauha, Elina
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Chemicals and biofuel components can be produced with the help of microorganisms in bioreactors. Microorganisms have very specific demands for optimal growth which makes the design and especially scale up of bioreactors challenging. Bioreactors are multiphase systems with complex hydrodynamics. Mathematical modeling can provide information on the functioning of bioreactors without the need for experimentation. Computational fluid dynamic (CFD) calculations are combined with a compartmental modeling approach for the calculation of 1) bubble column photobioreactors for the cultivation of algal cells and 2) large aerated stirred tanks for the cultivation of aerobic bacteria. Inclusion of dispersed phase population balances, mass transfer and reaction models makes the compartmental model very comprehensive. Local values of variables such as oxygen concentrations are attained. Simulation of bubble columns and heterogeneous conditions is enhanced with a new model for the calculation of dispersed phase flows that allows for bubble induced flow. New models for the consideration of light distribution and algal growth kinetics in the compartmental model facilitate the comprehensive simulation of algal growth. The results correspond well with measurements taken from literature and provide new insights to the design and run strategies of photobioreactors. It is shown that large industrial-sized stirred tank bioreactors operate at heterogeneous conditions due to the high oxygen demand of microorganisms. A new simple model estimates gas holdup and mass transfer rates at these conditions. Furthermore, a large stirred tank bioreactor is modeled at homogeneous and heterogeneous conditions with the compartmental modeling approach. Models accounting for the increase in coalescence at high volume fractions are required, without them the mass transfer results are too optimistic. A new reaction model for the uptake of oxygen enables the calculation of local reactor oxygen mass transfer capability at different hydrodynamic conditions. Dead spaces in the reactor are found and suggestions made for reactor design. The importance of considering local conditions in bioreactor modeling is shown by comparison to model runs where local differences are neglected. Omission of local detail leads to different growth dynamics in photobioreactors and overestimated mass transfer in stirred tank bioreactors. The study of outside cultivation in photobioreactors shows that the existence of the night, rather than the light extinction due to biomass during the day, decreases the maximum achievable cell density. Therefore, further modeling studies to the feasibility and optimum run strategy of outside cultivation are warranted. The study of large stirred tank bioreactors presents several issues concerning the use of these reactors in large scale. Designs of vessels and mixers can be altered, but eventually, a change to bubble driven systems such as airlift reactors should be considered.