MASTER'S DEGREE THESIS
Study of temperature dependence in the absorption cross-section of SO2
Vattenfall AB’s subsidiary ChlorOut AB has patented a measurement instrument, IACM (In-situ Alkali Chloride Monitor). This instrument performs online measurements of alkali chlorides, potassium- and sodium chloride in the hot flue gases. The measurements are performed upstream the superheaters in boilers that burn biomass (e.g. bark, forest and agricultural residues) to give an indication of the corrosion propensity of the flue gases. The measurement principle is based on molecular absorption of UV light in a limited wavelength region. This instrument has also the possibility to measure SO2. Furthermore, it is used to determine the quality of the incoming fuel mix and to provide a control signal to the ammonium sulphate injection system. In the strive to minimize SO2 emissions to the environment, an accurate measuring instrument is a key.
This degree project intends to map the temperature dependence in the absorption cross section (σ) for sulphur dioxide (SO2). It has been found that the measured SO2 concentration varies considerably, depending on how much the temperature deviates between the calibrated and the actual measured temperature over the measuring path length. In other words, the calibration temperature sets the temperature at which SO2 can be measured correctly in a boiler. Consequently, the measuring equipment must have a properly installed calibration spectrum for the temperatures at which the SO2 needs to be measured. This condition can be difficult to meet if the boiler load varies, as is usually the case.
The project will begin with a literature study to obtain a clear picture of the problem as well as an overview of the current research in the field of temperature dependence of the absorption cross section for SO2. The literature study can be undertaken at the university or college where the student is enrolled.
A substantial part of the degree project consists in laboratory work, which will be carried out at Vattenfall’s laboratory in Älvkarleby. The experiments are geared at laying the foundations for the mathematical expression to correct the SO2 concentration, regardless of the measured temperature over the measuring path length and calibration temperature.
A mathematical expression with the actual flue gas temperature as the in-parameter, which allows correct measurement of SO2 regardless of the temperature at which the instrument has been calibrated and the temperature over the measuring path length.
The ideal graduate student will be interested in, and have some knowledge of, optical measurement methods, specifically Differential Optical Absorption Spectroscopy (DOAS) for molecules. Moreover, candidates are initiative-takers, problem-solvers, and have a knack for practical work, since much of the time will be devoted to carrying out measurements in a laboratory environment.
Master’s degree project comprising 30 ECTS within the programme’s main field of study.
Application deadline: 09-12-2018
Start date: Autumn term 2018
Contact details: Tomas Leffler, phone: +46 703 050 210, email: firstname.lastname@example.org