Verhalten und Kontrolle von Schlacken des bioliq®-Vergasers

Pressurized entrained-flow gasification of biogenic resources is a sustainable and CO$_{2}$-neutral process to produce biofuels and further carbonaceous products. The bioliq®-process integrates the gasification in a process chain to convert straw and wood residuals into high-quality biofuels. The feedstock is initially converted via fast pyrolysis into a slurry consisting of a tar rich, liquid phase and a char, which is called BioSyncrude®. Afterwards, the bioslurry is converted into an almost tar-free, low methane containing syngas in a pressurized entrained flow gasifier at temperatures above 1200 °C. The syngas is finally used as basic reactant for the production of biofuels. Due to the high temperatures in the entrained-flow gasification the ash from the char melts, flows down the inner wall of the gasifier and is thus continuously removed. Furthermore, the formed slag layer protects the reactor wall against corrosion. Therefore, the characterization of the flow behaviour and the adjustment of the optimal viscosity range by influencing the slurry composition are the main objectives in this thesis. One possibility is to determine the viscosity of the slag from the outflow of the gasifier and deduce the viscosity at the inner reactor wall. The measured and the modelled viscosity values are compared and thus, the viscosity model is evaluated. A second possibility is to simulate the chemical composition of the slag at the inner reactor wall. A thermochemical model uses the composition of the slurry to calculate this slag composition according to gasifier conditions. The focus is on the release of Na and K due to the gasifier conditions before the slag is formed. The modelled viscosities are compared with experimental values to fit and evaluate the model parameters. The advantage of this method is to predict the flow behaviour at the inner reactor wall, which can be preventively adjusted by fluxing. For the economic operation of the gasifier, low viscous slags are preferred to reduce also the operation temperature and minimize the heat loss. Na- and K-rich additives are suitable fluxes, at which the viscosity is more reduced by Na, because it is less volatile at gasifier conditions. Hence, a higher amount of Na is incorporated in the slag network. However, adding too much Na will cause corrosion of the reactor wall and also significant amount of Na in the quench water. The models developed in this work allow for prediction the flow behaviour of the slags at the inner reactor wall. Furthermore, the potential influence of flux can be simulated and the complex reaction behaviour of the ash components can be described. Thus, the relation between the chemical slag composition and its viscosity can be shown in this thesis