Practical trainings, student assistants and theses

Mineral carbonation is a promising method for permanent CO₂ storage, particularly relevant to the cement industry, which accounts for about 8% of anthropogenic emissions[1]. In this process, CO₂ is transformed into stable carbonates using calcium- and magnesium-rich minerals. Wollastonite (CaSiO₃) is preferred for its higher reactivity compared to Mg-silicates.

CaSiO₃ + CO₂ → CaCO₃ + SiO₂

Wet carbonation in a three-phase reactor involves CO₂ dissolution, mineral leaching, and carbonate precipitation[2]. The main challenges are slow kinetics and low energy efficiency, requiring optimization of reactor design and operating parameters. Fluid dynamics analysis is essential to enhance mass transfer between CO₂ bubbles and solid particles.

To this end, the study aims to investigate how the reactor’s operating parameters—including temperature, solid loading, stirring rate, and CO₂ flow rate—affect the amount of CO₂ absorbed by the material (CO₂ uptake).

Objectives of the experimental campaign:

• Carbonation experiments on wollastonite under varying operating conditions in a 6 L stirred tank reactor.
• CO₂ uptake measurements of collected samples using a calcimeter.
• Data analysis and optimization of the operating conditions.

[1] A. A. Olajire, “A review of mineral carbonation technology in sequestration of CO2,” J. Pet. Sci. Eng., vol. 109, pp. 364–392, Sept. 2013, doi: 10.1016/j.petrol.2013.03.013.
[2] W. Ding, L. Fu, J. Ouyang, and H. Yang, “CO2 mineral sequestration by wollastonite carbonation,” Phys. Chem. Miner., vol. 41, no. 7, Art. no. 7, July 2014, doi: 10.1007/s00269-014-0659-z.

• Field of study: Process engineering, chemical engineering, mechanical engineering, fluid mechanics, physics or similar orientation
• Advantageous are experiences in laboratory work, evaluation of measurement data (e.g. programming skills) and chemical lab experience
• Ability for practical, accurate and independent work
• Good language skills in English

• Place of work: HZDR
• Start: from April 2026
• Duration: min. 3 months
• Remuneration according to HZDR internal regulations

A multiphase jet is the ejection of a fluid, in which different particles, bubbles and droplets are finely dispersed, from a small orifice. Examples of such systems are the ash clouds of volcanos, the liquid droplets from a spray can or the injection of bubbles in an underwater ramjet engine.

In our numerical and experimental studies of the bubbly jet [1], we encountered an interesting phenomenon that bubbles are pushed out of the jet centre into a thin layer at the jet boundary. This effect may be used to improve mass transfer or bubble-particle collisions in applications such as chemical reactors and mineral flotation. The task of this student work is to perform an experimental parameter study with an optical Doppler probe [2], measuring profiles of the bubble speed, size and volume fraction for different water and air flow rates. The results will elucidate the interaction of liquid flow with bubbles and how the bubble “hole” in the jet centre is affected by the process parameters.

The thesis subject includes…

• conducting and protocolling experiments with advanced optical measurement equipment
• evaluation and interpretation of the measurement data

[1] Zürner et al., Min. Eng. 211 (2024), DOI: https://doi.org/10.1016/j.mineng.2024.108699
[2] Lefebvre et al., Chem. Eng. Sci. 250 (2022), DOI: https://doi.org/10.1016/j.ces.2021.117359

• Field of study: Process engineering, mechanical engineering, fluid mechanics, physics or similar orientation
• Advantageous are experiences in laboratory work, evaluation of measurement data (e.g. programming skills) and optical measurement methods
• Ability for practical, accurate and independent work
• Good language skills in English and/or German

• Place of work: HZDR
• Start: from March 2026
• Duration: min. 4 months
• Remuneration according to HZDR internal regulations