MONITORING OF GAS-LIQUID MASS TRANSFER WITH SINGLE DROPLET EXPERIMENT

Anda Lucia

Research output: ThesisDoctoral Thesis

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Abstract

Reduction and capture of carbon dioxide CO2 gas emissions has attracted global attention in order to avoid global warming. Physical absorption is one method to reduce the CO2 gas from various sources. The spray method is one common process for separation of CO2. For the selection of an absorbent and a design optimization of the spray column, in-depth knowledge of mass transfer characteristics between CO2 and individual droplets are necessary. The physical data properties such as droplet diameter, contact time between gas-liquid systems and mass transfer coefficient are needed to design and optimize the absorption or desorption column. An experimental set-up comprising of a rectangular gas chamber, a shadowgraph system and an analytical method for the determination of CO2 concentration in water has been elaborated in order to study the characteristics of mass transfer between CO2 and liquid droplets. This system allows the observation of droplet size, droplet velocity and droplet behaviour during the formation and falling accurately. A series of droplets are generated by pushing liquid through a needle by means of a peristaltic pump. The droplets were detached from the needle and fell down through a gas chamber filled with nitrogen, and are collected in the bottom of the chamber covered with a kerosene layer. Droplet size, droplet formation time and falling droplets velocity are determined by means of a high-speed camera. CO2 desorption analysis from water droplets is carried out before and after dripping droplets. The liquid phase mass transfers coefficients of CO2 desorption from liquid droplets are determined at different droplet formation times, droplet falling heights and droplet sizes. The coefficient of liquid mass transfer of CO2 desorption from water droplets during formation and falling are evaluated at formation times 0.2328 s, 0.859 s and 1.08 s, falling heights 5 cm, 10 cm, 15 cm and 20 cm and droplet sizes 1.61 mm, 2.67 mm and 3.07 mm, respectively. The droplet velocity for all droplet sizes in this study matched with the model equation and this trends are also same with experiment of Takagaki and Komori [93] especially at short height. The experimental data for the terminal velocity of the droplets were similar to a study performed by Beard [96]. The average desorption rate of CO2 from water droplets during formation and falling at different distances and droplet diameters increases as droplet diameter decreases and decreases as the contact time increases. The experimental results on the ratio between CO2 concentrations at a certain time and initial CO2 concentration for droplet diameters 2.67 mm and 3.07 mm are in good agreement with the model from Hsu et.al [75], whereas for droplet diameter 1.61 mm the results fit Angelo’s model [73] because of pulsation during formation.
Translated title of the contributionBESTIMMUNG DES GAS-FLÜSSIGPHASEN-STOFFAUSTAUSCHES MITTELS EINZELTROPFENEXPERIMENTEN
Original languageEnglish
QualificationDr.mont.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Lehner, Markus, Assessor A (internal)
  • Ott, Holger, Assessor B (internal)
Publication statusPublished - 2017

Bibliographical note

embargoed until null

Keywords

  • Mass transfer coefficient
  • CO2 Desorption
  • Single droplets

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