omputational modeling of reacting flow inside the polyamide 66 polymerization line

Official URL: https://risc01.sabanciuniv.edu/record=b2767356_(Table of contents)

One of the methods used to manufacture polyamide 66 is continuous polymerization. In this manufacturing process, the reaction proceeds continuously, and a specific viscosity value is reached at the end of the reaction. Degradation and cross-linking may occur due to high temperature with high residence time. The average molecular weight drops, and the viscosity decreases due to degradation. These degradations also affect the viscosity build-up profile estimated along the polymerization line and disturb the viscosity increase homogeneity according to the degradation formation. In this thesis, the effect of the geometric structure of the continuous polymerization line on the viscosity build-up, the viscosity formation profile, and the gel formation were investigated. The reacting flow model was used in the research to analyze the viscosity change and the amount of influence through the nozzle. The temperature-viscosity relationship was established with the curve-fit function and integrated into the COMSOL software with the data obtained from the measurements made in the polymerization line at the Line 1 Nylon Yarn Production Facility Kordsa Teknik Tekstil A.Ş. This temperature-viscosity relation is not given directly for confidentiality reasons, and values have been changed accordingly. Four different nozzle geometry designs were investigated to examine the nozzle geometry effect. First nozzle is designed based on the existing nozzle in v the Kordsa polymerization line, second nozzle is designed with narrow-angle, third nozzle is designed with wide-angle, and fourth nozzle is designed as a straight pipeline. Only the geometry parameters were changed during the analysis by keeping the inlet and outlet boundary conditions and temperature parameters constant. All equation sets and constitutive relations were solved with the assistance of COMSOL software, and analyses were carried out. According to the studies, the viscosity formation profile varied with the change made in the geometry parameters without changing the temperature, inlet, outlet, and wall boundary conditions. In the analyses made in four different nozzles, four different viscosity, temperature, and reaction profiles were obtained. According to the flow analysis, as the pipeline diameter narrows, the polymer in the center heats up more than the wider diameter. However, due to this heating, the reaction dynamics change. In the nozzle, which is designed as a straight pipeline, the reaction rate is the lowest, and the lowest viscosity value is seen. Although the inlet and outlet diameters are identical, obtaining different viscosity formation profiles shows that the diameter contraction angle significantly affects the reaction dynamics.