Separation of Gas Bubbles from Circulation Waters and Pulp Suspensions in Open Channel Flow

The objective of this thesis was to study the removal of gases from paper mill circulation waters experimentally and to provide data for CFD modeling. Flow and bubble size measurements were carried out in a laboratory scale open gas separation channel. Particle Image Velocimetry (PIV) technique was used to measure the gas and liquid flow fields, while bubble size measurements were conducted using digital imaging technique with back light illumination. Samples of paper machine waters as well as a model solution were used for the experiments. The PIV results show that the gas bubbles near the feed position have the tendency to escape from the circulation channel at a faster rate than those bubbles which are further away from the feed position. This was due to an increased rate of bubble coalescence as a result of the relatively larger bubbles near the feed position. Moreover, a close similarity between the measured slip velocities of the paper mill waters and that of literature values was obtained. It was found that due to dilution of paper mill waters, the observed average bubble size was considerably large as compared to the average bubble sizes in real industrial pulp suspension and circulation waters. Among the studied solutions, the model solution has the highest average drag coefficient value due to its relatively high viscosity. The results were compared to a 2D steady sate CFD simulation model. A standard Euler-Euler k-ε turbulence model was used in the simulations. The channel free surface was modeled as a degassing boundary. From the drag models used in the simulations, the Grace drag model gave velocity fields closest to the experimental values. In general, the results obtained from experiments and CFD simulations are in good qualitative agreement.

Katumusoikeusistuimen historiaa

Kirjallisuusarvostelu

Nåden och gåvan i Philipp Melanchthons rättfärdiggörelselära 1521-1535

In this thesis Philip Melanchthon’s doctrine of justification is analyzed, especially the aspects of favor and donum in his writings until 1535. The research task is defined in the introduction of the thesis. Researchers agree, that Melanchthon emphasized the forensic aspect of the doctrine of justification, but this is not the case with the effective aspect of his doctrine of justification. Therefore, I have chosen to focus on the concepts of favor (grace) and donum (gift). The thesis begins with an analysis of the first edition of the Loci communes of 1521 in chapter two, and it ends with the second edition from 1535 in chapter seven. Melanchthon’s most important writings from the intervening period are analyzed in chapters three to six. In chapter eight, I describe my final results from the analysis. Although I have focused on how Melanchthon perceived the relationship between favor and donum, I have also taken note of such loci that are associated with his view of justification. I have done this in order to get a clearer picture of Melanchthon’s doctrine of justification, and of the issues which change in his theological thinking over time. In the research overview in chapter one, I divided the researchers in four different groups depending on how they perceive Melanchthon’s doctrine of justification. This classification is of course not comprehensive, since the reality is much more complicated. The main interpretations present in Melanchthon research are: 1. Christ as favor in justification, but donum is excluded from justification. 2. Christ as favor in justification, but the Spirit is donum in justification. 3. Christ as both favor and donum in justification until the early 1530s. 4. Christ as both favor and donum in justification throughout his life. The fourth option is in my opinion the most preferable. The analysis of Melanchthon’s writings shows that he expects both a forensic, and an effective aspect in the doctrine of justification throughout the examined period. Melanchthon strongly emphasizes that justification is by grace alone through faith for Christ’s sake, but also that the Holy Spirit works the justifying faith, and is the gift bestowed on believers in connection with this. Where the opponents according to Melanchthon see deeds, virtues, or a quality in the believer as the cause of the justification, there Melanchthon sees only Christ.